It’s very easy to tell that Juan has many, many hours of flying time. So focused and thorough; he knows a tremendous amount about a lot of aircraft. I just love his analysis.
What I like about Juan is he has so much aviation information in his mind, he has to page through his memory to access the information for the particular item he’s talking about. He has to pause to figure out which terabyte the information is on. As a parent it reminds me of a young child trying to make up a story. Two similar looks two VASTLY different situations. Juan is a walking aviation Wiki. Thanks Jaun.
@@jimsteinway695 I Believe that hs Hesitation is a well developed of ENGAGE the BRAIN before engaging the Mouth. A feature that (In the words of one of my old TI's at Chanute AFB in '65 would say) It would 'BEHOVE YOU TROOPS' and many Politicians and us to accomplish.
Juan was trained by the best: United States Air Force... (fka US ARMY Air Force), with an unbroken chain of excellence and innovation going back to the earliest days of powered flight. His airline is lucky to have him. OTOH, many at the controls of today's bizjets and turboprops went to Joe's Flight School, in Podunk, and just did NOT have the safety and PIC discipline drilled into them. (If no one YELLED at you during flight training, you are vulnerable to... doing the wrong thing, at the wrong time... pity.)
I prefer not to slather all over the place with slobbery praise and overly emotional sentimentality. Juan definitely knows as much as anyone, if not more, about aviation topics but in my humble opinion he needs to work on his presentation just a little in order to take it to the next level. Sometimes the stop and go recitation gets to be a little frustrating and while it boarders on potentially being a significant part of his style I'm of the opinion that he may need to relax just a tiny bit during his presentation and it would be a significant improvement for him; maybe he simply needs to rehearse his lines once or twice before doing a take or even repeat his lines in the mirror in order to make a vast improvement for himself. He's still my favorite aviation authority no matter how much he rehearses before his 'takes' and of course its his business how he runs his show, not mine. I always seem to have more critical thoughts towards the flood of slavering, kowtowing hangers on that constantly emote all over youtube; compliments are one thing but America seems to be so choc full of effusively sentimental, thin skinned wussies. Seriously, sometimes the comment sections of these videos read like cheap, overdone romance novels.
@@CRSolarice Since when is praise for doing a great job a negative thing. Hey Karen, if you can’t say something nice, just pass on by. Nobody wants to read your negative comments.
Something to consider. As an aircraft mechanic I have observed this sequence several times. Aircraft taxies to the GA ramp. Sets the parking brake. Locks the airplane and leaves. Several hours later the line crew has to relocate that aircraft. They hook up and as the they are able to move the aircraft they start the tow. Soon they notice that the tug is slowing down and very soon after they realize that the brakes are set. That is when I get a call! If we can’t get in touch with the owner and the aircraft is on a taxi way I release the brakes by loosening a bleeder on each mlg enough to release the brake. What happens is the brakes were hot when the parking brake was set. The were cold when the tow was started. However, dragging brakes rapidly heat up and expand. Dragging brakes now become locked brakes. Citation multi disc brakes will do the same thing. If the pilot set the parking brake to prevent the aircraft from rolling at idle and no more than that we have the same problem. Those big engines will move the aircraft into position for takeoff however, as the roll begins the brakes very rapidly heat up and soon they are locked. I believe this parking brake was set. The amount of braking is determined by the amount of peddle pressure applied when setting the parking brake. It is just a valve that closes off the fluid to the mlg brake caliper. The only way for that fluid to return is by opening the parking brake valve.
This exact sort of parking brake is offered in the aftermarket to - of all things - kit car builders. Often times, there is no way to have a proper emergency brake, so the existing calibers do double duty. Just like in the aircraft, the pedal is depressed and then the valve is shut, holding that pressure in the lines and caliper. So in the plane, the pressure is totally dependent upon how hard the pilot presses the pedals when the button is pushed, so the parking brakes can absolutely end up with anything between zero and 100%.
Excellent review. You and Mentour pilot are UA-cam's best accident reviewers. And your presentations, already top-shelf, are improving with each (unfortunate) review. Thanks.
see accident report of "Cessna Citation 560 Ultra, VP-CSN" in 2003 in which the parking brake was inadvertently partially or fully on at touchdown. Pilot subsequently had their company checklists amended to add Parking Brake OFF, before take-off and before landing. " Furthermore, trials conducted by the operator, subsequent to the accident, showed that it was possible to move the aircraft at speed with partial parking brake selected. "
Why is there a "partial parking brake" selection? The Europeans have noted several accidents with these types of aircraft whereby the parking brake was either not releasing or residual pressure in the system applying the brakes, as Juan suggested. A simple electrical circuit on the wheels should be installed to monitor actual wheel speed vs. ground speed, wheel slippage could then be calculated.
@@alexaltrichter1597 Or "Anti-Skid-in operation", means it is modulating the brake pressure. I would wish for an automatic release of the parking brake by throttle advance. Either this disengages the brake lever or the throttle cannot be advanced when the lever is not fully released. How many times have I set the parking brake on my car! And only when I got of the gas I notice by the rapid deceleration that the brake was still on. Despite having an indicator light in the panel! 🤢
It appears to me that this is a design flaw. If Cessna refuses to fix it, it's up to us to get the word out AND when you are a pilot flying these airplanes, take personal responsibility.! Add parking brake check to your checklist yourself! Spread the word to every single pilot you meet flying this type of aircraft! If we work together, we CAN make a difference!
Disclaimer: experience from auto hydraulics may not apply here, but maybe? There is a condition where a hydraulic master cylinder does not quite return fully, which it needs to do, to open the system to reservoir(=atmospheric) pressure and equalise. Although there is little or no system pressure at the time, the system is closed and any expansion (due to heat in the wheels?) can cause pressure to rise and brakes to drag increasingly with time. In extreme cases, they can lock on. In cars and motorcycle hydraulics, the solutions are 1) make sure the master cylinder piston physically returns *fully*. If the lever is adjusted wrongly, this can't happen reliably. And it's not enough to only check for no system pressure. 2) make sure the control lever is operated fully off each time, with no exceptions.
Apologies. I was interrupted by family and missed an important part. The parking brake valve takes the place of 'master' in what I said above. ideo mkes it clear that a sticking valve, or pilot leaving it set with the brakes only partly on, could cause this problem. I'd be hoping for a change of procedure AND a warning of brake pressure while engine revs are up enough for takeoff.
I was taught how to do a acceleration check speed@distance in the first few take- offs fir my PPL training. And it was reinforced regularly becoming instinctive after that. I get goosebumps that commercial charter pilots flying jets could somehow not have that as pert of their essential awareness regimin on take-off. I was trained in South Africa, only PPL single engine. Thanks Juan for all your fantastic videos.
@Matthew H If it is a regular use airfield you know where you should have at least a certain speed depending on the aircraft you are flying. Otherwise time is a measurement. If you are experienced, and with lighter singles you can immediately within a few seconds feel if acceleration is normal or not. It is much more procedural with commercial flying and the airlines. But the basics are the same.
Grateful for the clear explanation of the issues here. Retired after 45 years in navigation aids, radar, and comms in support of civil aviation. As Scott Manley says 'Fly Safe!'.
Videos like this makes aviation safer for all. It takes time to pull all the information together, then make the video. You can't expect someone to do this week after week, while also working his regular job, for nothing, do you??? I'm glad we have something like youtube where we can get this great information all for free while the guy doing the work gets paid also. It's a win win for all.
For this type of video, Juan gets no remuneration from UA-cam because UA-cam considers it "sad" or something like that. He depends on Patreon for his accident reporting videos. Utterly stupid Google policy given that air safety is almost entirely based on the analysis of accidents and the lessons learned, and also increasing public confidence in aviation. Why can millions be made by the Canadian and other corporate producers of the "Air Accident Investigation" shows on cable TV but private individuals such as Juan cannot on UA-cam ?
I just turned 47, and have started flight school. And really watching Juan has taught me a lot. Not replacing my instructor, but in teaching me this. The checklist is so Damn important, being aware of things you may not see in the checklist is just as important
I owned and flew a C560 or Citation V for several years. A couple of notes; I don’t recall the parking brakes ability to hold back two P&W JT-15 Ds with almost 6000 Lbs of total thrust! So our procedure was to release the parking brake on taxi, check brakes for rolling and stopping while taxing on both sides (left and right) and never touch parking brake handle again. I ‘believe’ a partial engagement is possible and the activation of anti-skid is also possible with brakes heating and locking while aircraft is rolling and the system would not know of a ‘partial engagement’……
@blancolirio you're missing a critical point: the parking brake valve only traps the pressure applied when it is set. It's entirely possible to depress the brake only very lightly when setting the parking brake. The drag may not be immediately evident to the pilot on the next taxi to the runway but it would be more than enough to heat up the carbon brakes on the takeoff roll.
Correct. It is also likely that if you're just using the P brake to stop it from rolling to grab a clearance or something you would not push hard on the brakes before trapping pressure with the P Brake, just enough to stop idle thrust from rolling it. Also, carbon brakes get better with heat which increases the problem on ground roll. Lastly, at fwd CG limits It feels to me that there is not a lot of "extra" elevator authority to rotate around Vr speeds, I don't feel like it would take much brake drag to cause "no rotation". Cessna should add something to trigger the "NO TAKEOFF" light if there is any trapped pressure in the system.
XLS serial number 6001 and up wiring diagrams show a proximity switch at the parking brake valve lever that is supposed to trigger the no take off warning annunicator. N560AR was SN 6026.
@@blancolirio The wiring diagram doesn't specify European certified aircraft, the print is applicable for aircraft serial number 6001 and up. The IPC lists the park brake proximity switch being effective on earlier serial numbers that were British, Denmark, and French certified aircraft.
@@jasonross3294 USA Certified aircraft do not have the proximity switch regardless of aircraft age or serial number, the wiring is not present in the aircraft I am familiar with that is SN6100+
@@blancolirio USA Certified aircraft do not have the proximity switch regardless of aircraft age or serial number, the wiring is not present in the aircraft I am familiar with that is SN6100+ The X+, Sovereign +, Latitude, and Longitude all have a No Takeoff CAS Message through the G5000 System for parking brake on, that is incorporated into the throttle system. I do not believe the CJ3+ or M2 with G3000 have a CAS for P Brake on
I flew Cessna 400 series, CE500 series and Citation CJ series aircraft. Parking brake controls appeared the same on all aircraft. My procedure on releasing parking brake was to pump the brakes after the parking handle was released to verify the parking brake was released . LR45 has parking brake warning on takeoff configuration ICAS. Bombardier certified that aircraft the same FAR25 certification requirements that the B777 met. Europeans were smart requiring this configuration warning for this. Cessna will stick by there present checklists to evade a lawsuit. Excellent video
I hope the NTSB has enough brains to recommend this change not only in its final recommendations to Cessna but also to the FAA to "require" this, thus giving Cessna a legal "out" to make the change "...only because the FAA unnecessarily required it...". Future safety is more important than Cessna paying for their negligence, much as they ought to.
Is it possible for the anti-skid system to vary the hydraulic brake pressure felt at the brakes with the parking brake engaged? Or would the parking brake valve, when engaged, prevent the anti-skid system from varying the hydraulic pressure going to the brakes?
@@thisisnotmax From the schematics I take it that the parking brake lever simply applies any pressure that is in the system to the brakes. Upstream in the brake line is the ant-skid-controller which modulates the pressure. From the picture of the skid marks it becomes clear, as Juan mentioned, that the wheels were skidding more and then less again. The stripe was not continuously the same strength.
Its refreshing to have the experience and expertise of a great pilot analyzing these incidents with the purpose of keeping US safe so we don't screw up and make the same mistakes. Great job Mr. Juan Brown! Very much appreciated!
Great update. I really appreciate your perspective clearly underscoring the "takeaway" lessons from your reports on mishaps. No histrionics, no sensationalism, and value added from your professional pilot experiences. (You reminded me of a hydraulic parking break valve I had added to one of my POV trucks. I believe the lever did not release the brake fluid pressure unless there was pressure from the foot pedal, too.)
Some quick thoughts - If the parking brake isn't fully released - the system partially pressurized, then the wheels will roll, with some drag, until some of the weight on the wheels is relieved as the wing starts to lift - at which point, the wheels would lock, as the friction of the brakes exceeds that of the wheels on the runway. At that point, the antiskid would detect the lockup and relieve the pressure, then the brakes would lock again as the antiskid cycles. Other thought - since the parking brake valve is holding the pressure released into the system by activating the toe brakes, if the toe brakes are only partially applied, then it's possible to have a partial application of the brake that isn't enough to stop the airplane, but will hold it back. From teh system diagram, the parking brake valves are check valves - one-way valves - they'll hold the brake pressure at a certain level, but will permit additional pressure to be added by normal brake application, but not released.
Almost, but antiskid is before the parking brake system and can't effect pressures after it. (It just locks the pressure in after it). The skid marks are likely from suspension hop as the tires lose grip.
Juan, tomorrow I will study and understand “Minimum Acceleration Check Speed” for my Saratoga Turbo. It won’t move with the parking brake set but it will move with it half set, ask me how I know. I’ll figure this out and make it part of my takeoff check, like oil pressure, manifold pressure, airspeed alive. I participate in the Wings program every year and I’ll talk to my instructor about it. I’ll even check with our wings region person to see if this is covered. Thanks Juan!!!
Great analysis, as usual, and that 50/70 rule is a handy cross-check. Regarding the annunciator system for the PB, every automobile has a red dash light that shows 'BRAKE', and many newer ones have annoying dingers that at least indicate something isn't right to start rolling. Brake temperature warning might have some use in helping identify this problem along with a warning , and since brake pressure is monitored, residual pressure with brakes released would show a condition of fluid trapped in the wheel caliper areas. I've heard in the past of aircraft that actually got off the ground ok with the dragging brakes on fire, then retracted into the wheel wells, and then.......... I've been within 20 feet of a KC-130 tire that blew off a shattered rim during towing, and it has enough force to de-skin a wing.
Been watching Ryan at Missionary Bush Pilot for a while and he always picks his spot for "air speed alive" before advancing the throttle. If I was a pilot, I would add the p brake to my checklist if it wasn't already there. Never take anything for granted.
As a Fixed wing man MANY MANY MANY Moons for Uncle Sam, you are IMHO Thee BEST for attention to detail and and there is NO 1 Else I watch. As the old saying goes “Take offs are Optional but landings are Mandatory”. Great Job as always.
SB is needed to add the brake config to the take off config parameters like in the challenger 604. With the brakes set and throttles forward you get a T/o config brakes.
Great video, Juan! You explain what had troubled me about this accident: IF the pilots had for some reason aborted the takeoff after V1, which everybody was assuming was the reason for the tire marks on the runway, WHY did the witnesses seem to indicate that the engines were at full takeoff power throughout the accident sequence ("normal" sounding to a witness beyond the runway end until the one engine evidently ingested something from the power pole), and why did they fly for a distance? That's not the typical abort-after-V1 profile. We assumed it had to do with the elevated runway, perhaps, but it didn't feel right. This sort of explains it. And the report indicates, as you note, that indeed the engines were at takeoff thrust throughout the sequence. The one witness's observation about not seeing the nose wheel off the ground at the intersection, and the observation that the a/c was moving slower than usual, suggest that some level of braking was being applied very early in the takeoff roll, retarding the acceleration and holding the nose down. And yet the skid marks and antiskid "chirps" don't appear until well down the runway. How was it that the tires were rotating on this aircraft at all with the parking brake on, and if takeoff thrust was enough to overcome the parking brake, why didn't we see skid marks until they're 2/3 down the runway? Was MORE brake pressure applied by the system later in the roll? How does that make sense? One possibility is that the lift component from the higher speed as the accelerating aircraft got towards the end of the runway would make the aircraft lighter on the tires, reducing friction between the rear tires and the ground so that the ground wouldn't turn the wheels and instead they would skid. (Indeed, maybe that's the explanation.) If so, that supports the idea that the parking brake was applied from the very beginning and indeed takeoff thrust in this thing is enough to overcome the parking brake (as it is in my automobile). If that's the case, then Cessna indisputably needed to have the parking brake as part of the NO TAKEOFF warning system. With the brake on, and takeoff power applied, the aircraft behaved normally-ENOUGH that the pilots didn't immediately decide to abort. What is truly-disgraceful here, and I know you're too polite to say it, is that some European agencies (or smart customers) apparently required that the parking brake be part of the NO TAKEOFF warning system, so Cessna plainly has the wiring and computer logic already in place to provide this safety measure but decided not to include or activate it in US-registered aircraft. This also reminds me a bit of the Ameristar Charters MD80 accident, where the Captain (who had a zillion hours in DC9-series aircraft) pulled back on the yoke, got nothing, pulled further, still got nothing, and immediately aborted even though he was beyond V1, basically saving everybody. NTSB said that had he taken even a couple of seconds to think about it before aborting, everyone would have died, as they would if he had tried to take it into the air, because it was under no circumstances going to fly. Being present and fully-focused in every moment of the takeoff is what allowed him to react decisively to an anomaly, whereas these poor guys evidently didn't have that edge-of-their-chairs, looking for reasons not to depart, knife-edge awareness that would have allowed them to timely abort. I like the guy who says that every landing is an aborted go-around. Perhaps there's a component of that mentality that would have saved lives here.
@William Candee referring to the first part of your post about the skid marks, maybe the tyres were rotating initially (assuming the parking brake was ‘partially’ set) but wore a flat spot. The flat spot might only grab slightly for a start but it would grow to the point where it’s just going to lock into that position on the tarmac and leave a continuous skid mark. This might even explain the intermittent darker patches which have been attributed to the ABS.
I have had a citation accelerate with the brakes locked during ground runs..it went about ten metres before I got the power back... I know of another 560 citation went half way down the runway on take off with the wheels locked and on fire..
I’d add my son (real pilot) and me (guy who pays for pilot) tried this takeoff in x-plane and MSFS. I gotta say on the best day, it’s pretty close to the runway end lights when the citation lifts off (without the parking brake) on that same departure. He managed to get a 737-max and a 767 off with actually a shorter roll. But as you note, there is zero margin for error here. It must be money that they’re based at Robertson field given that Bradley international (with its 9500’ 6/24 runway) is about a minute away by plane
Humans are amazing at finding a way to make a aircraft system work against them. If there is something that can be done wrong, it's only a matter of time before it's found. The FAA's job is to act as quickly as possible to avoid this from happening over and over by acting a tad faster in reporting the incidents
One possible explanation is that to land on that short runway requires heavy braking. The Citation landing distances are dependent on touching down at the correct speed and with aggressive braking. Not the kind of braking that most pilots carrying passengers apply. Heavy braking heats up the disks and the pads. Then the aircraft sits and the disks and the pads cool down. So with the cooling, the brakes are not effectively on (the pads are not pushing against the disks). Then they take off with the parking lever still pulled, parking brakes on, and as the aircraft accelerates down the runway the pads and disks heat up and all the sudden the brakes are on (pads applying pressure to the disks) and the skid marks start. With the brakes cooled down, the aircraft might taxi normally and the pilots didn't realize that the parking brakes were on.
Very professional and thorough presentation Juan! Expect an FAA Airworthiness Directive to be issued in the very near future to address this problem. I see the installation of new parking brake valves on the Excel series of aircraft and then the possible install of a redesigned valve when they become available. In addition, the parking brake position will have to be incorporated into the "No Takeoff Warning System". If this modification is not feasible, then an independent subsystem will have to be designed to trigger the Master Warning System when the throttles are advanced to the takeoff position and the parking brake is in the set/on position. Flight Manual and checklist amendments will have to be included as well. For your information, the larger and more elaborate models of Cessna Citations have the parking brake position monitored by the No Takeoff Warning System. The 560XL series shares it type certification and type design specifications with the original Model 560 and was delivered as such.
Less than full brake system pressure can be trapped in the brakes under the following scenario. The brake metering valve, which is controlled via the toe brakes, modulates brake pressure from zero to a little over 1000 psi. What happens is the pilot applies just enough brake to stop and hold the aircraft (which is at idle thrust) then decides to set the parking brake. At this moment, there may only be around 300 to 400 psi trapped in the brakes. Moving the aircraft forward again while forgetting to release the parking brake is easy, just add power and it will roll forward. It will definitely require more power than normal to maintain or achieve a given speed. Bottom line here is when setting the parking brake on a Cessna Citation is to fully depress the toe brakes so the brake metering valve can apply maximum pressure to the brakes.
Juan, there is a reference I saw on the checklist for Brakes on the static roll and rolling take off to release, but nothing on parking brakes. I'm not a pilot, but you'd imagine there had to have been a lack of performance immediately if they were dragging brakes. Great job on this, fascinating and sad we have to lose people in order to update checklists, flight control systems... excellent video.
Since a long time I'm thinking about a takeoff acceleration warning system. Thru the GPS it should be possible to evaluate the exact position of the aircraft on the runway at any time. So it's easy for the FMS (which has a database of runway lengths of all airports) to calculate the remaining runway in front of the aircraft at any time. When FMS now do calculations with the actual speed and actual acceleration values, it should be possible do determine the estimated takeoff position. And when it is beyond a specific safety margin, the FMS should give a master warning!
When I set the parking brake on my car, I ALWAYS jam them on as hard as possible. I don't want there to be any doubt when I try to drive off that the parking brake is on or not. I nearly burned out the brakes on my wife's car one time because I didn't know that she had set the parking brakes on weakly, and the car drove almost normally. Luckily, I detected the problem in time. Dunno know if this is how aircraft parkng brakes work or not, but it's good advice for us folks who only drive non-flying vehicles.
My 14 year old Jeep has a parking brake warning light and it also beeps loudly at me if I try to drive away with the parking brake on. It also gives priority to the brakes over the throttle, so that if both pedals are pressed, the throttle drops to idle immediately, even if the throttle pedal is still being pressed. If you have a "floor mat incident" where the throttle sticks at full, all you have to do is press the brake pedal and the engine will go to idle.
That reminds me of a class mate when we were around the age to get driving licenses. He pulled up in his fathers BMW before school and told us prod that his father promised him this car. He went silent when we questioned the skid marks and the red glowing rear drum brakes 🤣
Great stuff Juan. As a high time c500,c560xl, c650 (all same brake) guy I can tell you the brake almost hits your right knee when pulled. The parking Brake pressure is directly related to the pressure applied to the pedals BEFORE the parking brake is pulled! There is NO accumulator. It is very common for a citation to go rolling off a sloped ramp if the chocks are pulled. Because not much pressure was applied to the toe brakes. I personally have had an airplane change parking spots with a co-pilot sitting in the airplane un aware he had moved 60ft down the ramp. I can’t imagine how someone can take off with the brake on(SMH). But I really looks like that’s what they did. Damn shame. Also I always use a parking brake! If my head goes down to do anything to the fms, to brief a chart, or take my eyes away from outside the airplane the parking brake is set. The last thing you need is to accidentally move! I’ve been in several airplanes that the pilot flying released enough pressure to let the airplane roll, with both heads in the cockpit. This always results in a panic stop and one of the pilots saying an f word!
Iirc, the brake lever near the pilots right knee in the C650 is the emergency brake, not the parking brake handle. The parking brake handle is behind the center console and is pulled up to engage and pushed down to disengage. That’s from memory which is years old though. I do have a pic of the 650 cockpit and the emergency brake handle by the pilot’s right knee is just to the left of the emergency gear extension handle.
@@speedlever I had forgot that. Been awhile out of the 650. I do remember that control lock down in the center that we used. Thanks for the correction. I went form the 650 to the 560xls, sure I still have a little of mix in my head. Strange mix of everything in the xl.
@@tymatt4555 No worries. Been years out of the cockpit for me. Flew a bunch of different Citations but never had the pleasure of the 560xl. I loved the 650 (III and VII). I hate to think all I’ve forgotten.
@@speedlever the 7 was a great flying airplane. The xl not so much, heavy on the controls and main gear way to far aft of CG. But it’s a hauling truck, with good field performance on that straight wing. And lots of baggage space. I’m in the falcon 2000lx now and it flys almost as nice as the 650. But lots more power and range.
According to the schematic shown, if the parking brake were "set" with only moderate/light pressure on the brake pedals, the lowest part of the system would be holding a partial brake pressure, a drag but not a full hold-back-against-the-engine.
@@bobroberts2371 That is what I thought at first glance. Careful review of the schematic showed me otherwise. The actual last valves are the A/S Shuttle Valves, which actually release the brakes when a skid is detected.
One thing that i have observed and no one is talking about is, even as the parking brake may have been set at minimum setting, as the wheels turn the brake pads, rotors and calipers heat up tremendously. Which causes the fluid in the caliper to expand and apply more brake. I "IMO" believe that is why the skid marks were not seen except on the far end of the runway. When I learned to fly back in the day, my instructor had me use the toe brakes to do a run-up.
@@RyeHillBaptistChurch Good point. It appears (looking at online documentation) that this build-up is one of the things the A/S Servo Valve is supposed to alleviate, but with the P\B Check Valve set, this alleviation would be negated.
@@bobroberts2371 ...(more) Looking at the technical documents for the A\S Servo Valve, the function of this valve is to provide a constant supply of brake fluid corresponding to the applied pressure on the pedals as the A/S Shuttle Valves release fluid, thus preventing pedal sink.
Yes, we had a similar occurrence on a Citation XL about 15 years ago. During takeoff the aircraft would not rotate, crew aborted and stopped safely. I do not remember whether the parking brake had been set accidentally or whether the brakes locked up partially due to a defect. In any case, those XLs will not rotate in such a situation, period. On the current type that I fly we do have an "acceleration indication" (g-force) on our PDU (primary display units) and during takeoff there's an official callout "acceleration checked" at about 50 knots. Potentially a life-saver!
Agreed these definitely need a brake/throttle interface that prevents the throttles from being advanced, or an audible TC warning that would sound, if this were attempted during normal flight operations. In this case the brake(s) may not have locked completely until friction heat caused enough expansion to defeat the ABS system. Good report Juan, thanks.
All my career each time I pulled into position or unto the runway for takeoff I performed what I called the suicide check : flaps, stab trim, bugs and brakes and at the beginning of the takeoff roll...slight .and pull on the elevator to see if there is movement.
Good job Juan. Forgot to mention that the crew should have Aborted with a loss of directional contol prior to V1, which is part of the standard takeoff breifing. A Monday morining QB would have used wet runway V1 data on this short runway. This would give them more runway available to stop on if a rejection was needed.
I commented in your initial video on this crash that it was the parking brake on. I personally witnessed a takeoff from the right seat in a citation a few years back where the captain forgot to release the brake after an extended line up and wait. It took almost all of the 8300’ runway to be airborne and we burst a tire on landing. The first thing you think about is the engines are not making power. It wasn’t until after rotation I looked over and pointed out to the captain the parking brake was set and told him not to raise the gear which he did anyway. They have no chance on a short runway like that. There was definitely a distraction to the crew right before taking off leading the captain to forget to release the brake.
In the MQ-9 Reaper, we had an acceleration time check. It's not what I'd consider a high performance aircraft, but it's flown like an 11k pound turboprop. We calculate TOLD data, including V-Speeds, and time to 50kts. When I takeoff, I call the seconds on the clock in the HUD. "FULL POWER, 12 ON THE CLOCK." If our acceleration time check is 17 seconds, both crew members know to look for 29 seconds on the clock. The Sensor Operator acts much like a copilot, and monitors the speed check. Usually it sounds like "50, SPEED CHECKS," and I'll look at the clock and speed as well, and call "GO." It's a good and critical practice. We have different criteria than standard V1/V2 etc, since it's a single engine aircraft, but it's proven to be a good, safe procedure.
This is not a shot fired at you, just an observation. But I never realized how often the Air Force crashes drones until I went to AMIC ("safety school"). And how frequently they go lost link. There are a lot of unique challenges to flying drones.
@@MattH-wg7ou I knew a couple guys in the air force who were stationed in Korea as maintence crew on the Global Hawk... One of them swore up and down it was a manned aircraft, and he WASN'T joking..... Scared the shit out of me. Lol Unless DARPA is up to some really crazy shit, and he was saying things he really shouldn't have been saying... I'm pretty sure someone is stupid in this situation, and it isn't me. The hell kind of maintenance was he doing? Haha that was over 10 years ago and I still laugh about it to this day. I really hope some senior enlisted was playing a prank on him and had him convinced like, a pilot climbed in there when nobody was looking and you couldn't see him, cause no windows..because otherwise. Man... I don't know what to say.
I think arrival position is where they would start their take off roll, opposite end to take off end. Arrivals end would be where arriving planes would touch down.
The locals say MAN-ee-oh (think manny-o). MAN-tee-oh also works and that is what you will hear in most of NC. Wonderful little place on Roanoake Island just before the Outer Banks. Have been fortunate enough to visit the Carolina coast many times. I really enjoy your channel Juan, especially the level of detail you go into. Thanks for all the time you put into making these videos for us.
The parking brake valve traps whatever pressure is applied to the brakes when the parking brake is set. Best procedure is to stand on the brakes (with power/28v on) to energize the power brake pump, stand on the brakes, then set the parking brake. Newer airplanes have done away with master cylinders on the rudder pedals entirely, pedals just apply inputs to the brake metering valves downstream from the electric brake pump. Any other procedure just traps whatever residual pressure happens to be in the system. Sometimes its enough to keep the airplane from rolling, especially with new/good brakes on a level ramp Worn brakes? Sloped ramp? Maybe, maybe not. Another issue was related during a line shack BS session about this. C560 was chocked, needed to be relocated to other side of field. Guys hook up, start towing it across. Had to stop before crossing the active. Start to pull again, wont move. Brakes are locked. Parking brake set in cockpit, aircraft door locked. Pilot had to be called out to unlock door and release the brakes. The consensus was that the pressure gradually increased as the dragging brakes temp increased, thus locking the brakes when stopped Same system has been used in the 500 series since day one, along with the 650s. One might ask why there is suddenly a problem. The 560XL/EXCEL has an abundance of power, compared to the earlier 500 series. When mechanics do ground runs, especially when you need to run it above 85% and are light on fuel, its good practice is to stand on the brakes, apply the parking brake AND chock the main wheels. Its easy for the airplane to overpower whatever drag coefficient there is between tires and pavement. So why does this problem occur recently, when the parking brake system has worked fine for the previous 40-50 years? I'm just guessing, but one of the factors may be that there are a bunch of pilots out there who dont know, or care to understand, how their airplane's systems actually work. You will debrief these guys who write squawk scenarios that "cant happen", then get the "deer in the headlights" look when you start asking for more details. Any mechanic/AMT who has spent any time at all debriefing flight crews can tell you this.
In all my years of flying different type of aircrafts, I always perform and use the BFATS check; Brake (parking brake OFF), Flaps(set for T/O), Airspeeds(Posted, reviewed), Trims(set for T/O) and S for safety ( T/O clearance, seatbelts, etc). Never failed me. And for God sake Cessna please incorporate the parking brake into the take off warning system! Stay safe everyone
Great video. I did alot of single pilot flying in my career. I agree to not setting the parking brake after taxiing begins with some exceptions. When i was single pilot and got a line up and wait i would stop at an angle so i could see the final over my shoulder. Departing from a high speed taxiway at a busy airport would present a problem so when i pulled onto the runway i turned a little to see the final. Controllers are awsome but human,
Great report Juan. My Granddaughter has her PPL and is now doing CPL. My god this flying business is complicated just trying to get airborne. Hate hearing about crashes. May those poor people Rest In Peace. 🙏 🇦🇺
From the diagram and your description on how to set the parking brake, I can imagine the following scenario: The pilots brought the plane to a normal stop with normal braking force, then set the parking brake. The set parking brake just kept the pressure the pilots had applied at the time they set the brake. Aircraft didn't move, engines at idle. When they were finished updating the FMS, they advanced the throttle, maybe slightly wondering why they had to apply a somewhat higher thrust to overcome the resistance of stopped wheels. They didn't stop again on the runway but just opened the throttles for the takeoff run, not noticing they were still applying a normal braking force. Since they didn't do the takeoff performance check, they thought they were accelerating normally and tried to take off. The result was this crash.
If the park brake was on, cycling the antiskid should have released the brake. But the Cessna schematic shows the park brake is a check valve, which means the antiskid servo would pump the pressure back up again with the park brake holding the new pressure. That's the part of this design that sucks, IMO. The park brake check valve should not be where it is in 17:21 schematic, but perhaps rather between the power brake valve and antiskid servo valve.
It's a wacky system that has never been brought up by Cessna in detail. The Latitude, Longitude, Sovereign + and X + have No Takeoff warnings with the P Brake on... I'm not aware of any other Citations that do. It could be fixed by adding it to the micro-switch that is already in the throttle quadrant that annunciates No Takeoff if flaps are beyond T/O, speedbrakes deployed, or out of T/O trim... why the P Brake isn't on there is mind boggling.
@@oreo10111 I'm surprised that the high-end Cessna jets that you mentioned above don't have parking brake NO TAKEOFF warnings. In the Citation 525 M2, there's both a NO TAKEOFF CAS message on the primary flight display whenever the parking brake is set. And when you advance the throttles for takeoff beyond the cruise detente, the warning becomes an oral warning. Why is it the case that the lower end of the Cessna jet lineup has more sophisticated parking brake warnings? Is it because all of the planes that you mentioned require two pilots a and they should know better working as a team? Or put it another way, catch each other's mistakes? In case some don't know, the Citation 525 series is certified for single pilot operations.
It would appear that the parking brake would only be applied as firmly as the service brakes were applied while the parking brake knob is pulled out. Could conceivably be applied just enough to not really be noticed, but still enough to interfere with the takeoff... Also, pulling up elevator would drive the braking wheels harder into the ground. A really bad deal.
Thank you, Juan. I'm just a VERY casual simmer, but everything felt wrong about this one. I went and flew a short runway in MSFS 2020 in a Citation, and it definitely goes by quickly. In the sim, the parking brake is just on or off (as far as I know; maybe it can be configured) so the problem wouldn't have ever occurred to me. It's very sad that something like this cost lives. I hope Cessna makes those changes.
I wish everyone connected with aviation was as dedicated with regards to finding out cause & effect and making sure it doesn’t get repeated causing loss of life & airframes. Thanks Juan for all you do to help keep aviation safe.
Juan, nice video, but clearly the parking brake is working as intended. As a mechanical engineer I believe what is happening with the skid marks is that enough lift was generated to allow the tires to skid, the suspension unloaded (moved down), traction re-established, suspension loaded until slip and repeat. Think of tire hop of a car accelerating, just in reverse. The ABS is upstream of the parking brake and can't release parking pressure or reapply parking pressure.
While I don't have aircraft experience, I have extensive automotive and industrial experience. The diagram is more of a theory of operation rather than exact schematic however there is enough detail to sus out operation. Working the system from top down. Dotted black lines are electrical connections Purple lines are hydraulic system returns ( from the basic diagram it appears that when the toe brakes are depressed, this bleeds pressure from the control side of the Power Brake Valve. The output of the PBV is what applies the brakes. This is a fail safe, if a toe brake valve leaks the brakes apply rather than not being operational. ) Green lines are returns to the supply reservoir . Red lines are what applies the brake calipers. Blue lines are the emergency braking system. Working the system from bottom up Shuttle valves at wheels. This selects between the service braking system and the emergency braking system. This is basally 2 check valves per wheel that automatically select between the two. If the emergency braking system is applied, the rest of the system has no effect, the brakes remain applied. Parking brake check valves. When the parking brake lever is in the OFF position, fluid can flow in both directions. When the parking brake lever is in the ON position, fluid can flow to the wheel brakes through the check valve but not away from the wheel brakes. This means that the pilot can move the parking brake lever to ON then push the foot pedals in order to set the parking brake. If the parking brake lever is set to ON and no other action taken, the aircraft will still be free to roll. Anti skid servo valve. This is what bleeds pressure from the red lines in order to release the brake caliper preventing the wheel from skidding. From the diagram, it DOES NOT have the capability to apply the brakes. Power brake valve This directs hydraulic pressure to the rest of the system when the toe brake pedals are depressed. The system is set up so a pressure reduction in the purple lines causes the valve to move allowing pressure to flow from the accumulator to the rest of the braking system. Accumulator / hydraulic pump This is where the system gets operational pressure. This system acts more like air brakes on a large truck than hydraulic brakes on a car. Toe brake pedals This bleeds pressure from the Power brake valve to the reservoir to allow the service brakes to apply. Weight on wheels switch ( not shown ) Juan replied that this arms the anti skid system when the aircraft is on the ground.
Part 2 So, if the parking brake lever is in the ON position, the brakes can be applied through the service brake system but the brakes will not release. This means that the anti skid system has no effect in reducing braking pressure. The light / dark skid marks may be from the brakes overheating and developing uneven braking forces as the brake rotor warps. Another possibility is the runway has differing friction coefficients / surface texture causing the skid to change. If the skid marks were from the anti skid system and the pilot was using the toe brakes, I wonder if he was trying to stop but forgot to cut engine power If a toe brake valve developed a leak, the brake for that side would apply. Left and right would have to leak at the same time in order for both brakes to apply so I don't think that this is the case. If the Power Brake Valve developed an internal leak on the purple line control side, this would apply the brakes and allow the anti skid to operate. The real question is, for this particular PBV component, is there an overlap between L and R systems?
Sounds like the Cessna needs a latch and a spring on the PB, where setting the brake latches it against a spring--and when you release the brake, the spring insures that it releases completely.
Very informative. Like with our ARFF Rescue vehicles, we can not move the vehicle if the parking brake is on. I think they should do that with these type of aircrafts, or have a loud beep in the cab when the parking brake is on so that the pilot will have no way of forgetting. These types of crashes should never happen. Thanks for this review.
I think the parking brakes were partially applied but not enough so to be noticed on the initial part of the takeoff roll. As the brake rotors heated up, probably red hot, they locked the mains. Also possible the pilot not flying, realized a s!ow acceleration hit the toe brakes and the parking brake va!ve, being shown as a check va!ve, locked the mains.
In the Falcon 7X we note the expected acceleration and the displayed acceleration displayed rather than an indicated airspeed check. Normally the expectation is around .40g + at light weights down to the .20 range at very heavy weights and high/hot conditions. A significant deviation is cause for rejection. The parking brake position is monitored on most business jets. Perhaps because the Citation was certified so long ago it was not a requirement at that time.
This is what I was thinking.... I did delivery on this type model 99-2008 @ Cessna/Wichita. Lots of flights & taxi runs as a mechanic. I never had any forgot moments like this...
Excellent as usual Please cover the crashes at Arkenstol as there seems to be zero coverage of the accidents and a heck of a lot of speculation and verbosity concerning the entire contest. It would be nice to see the truth.
One factor that I did not see mentioned in the comments here yesterday, which I only learned about late last night, reading the "Cessna Citation XLS - Power Brake and Anti Skid System", is that the anti-skid system only operates when the speed is above 59 knots.
I have been flying the 560 XL and XLS for 16 years now. Even with the parking brake set after starting the engines it sometimes will roll on you if you’re not careful.
The parking brake on these aircraft use a valve that traps fluid/pressure in the line and at the wheels. There's check valves that allow pressure to be INCREASED by pressing the pedals while the parking brake is set but doesn't allow fluid to return the other direction. There's a few ways you can get "partial" braking with this system. One is if you are not pressing the toe brakes hard when you activate the parking brake since whatever pressure is at the wheel is what is maintained. Second is if you set the parking brake when the brakes are hot as they cool the hydraulic fluid contracts and releases the brake pressure at the wheels. It only takes a VERY slight contraction of the fluid to cause a SIGNIFICANT drop in the trapped brake pressure.
Juan you mentioned that if you have a second pilot then have him holler at you if you're rolling when writing down a clearance... he really is the one who should be writing the clearance but I get the point that in a single pilot type aircraft, a second pilot may be more of a request or tag along rather than a structured operation. I've been such a second pilot in small charter ops at the start of my career. And yes Cessna should look at this system inclusion in the Config Warning. We had this in the Lear as far as I recall, and every aircraft I've flown since.
Not saying it happened here Juan, but I’ve seen on some automotive brake hoses where they deteriorate inside and form a sort of check valve and not let pressurized fluid back thru quickly when the pedal is released. This usually shows itself as a caliper that won’t apply or one that drags and wears out that pad prematurely.
I've seen this loads of times in the classic car world. The inner hose collapses and when the brake pedal is depressed the fluid pressure opens up the collapsed inner hose and the subsequent release of pressure allows the inner to "relax" into it's deformed or flattened state thus not allowing the brake fluid to return to the braking system or master cylinder. Visual checks of the brake hoses don't catch this failure condition, it's usually only caught if you have an assistant operate the brakes whilst you apply your fingers to the affected hose. Due to the structural integrity of the hose being compromised the hose will often swell more than is acceptable and then remain hard as it is pressurised with hydraulic fluid. Further confirmation can be obtained by the fact that the wheel will not turn and when the bleed valve is released whilst you keep your fingers on the brake hose, the pressure under your fingers will disappear and the wheel will again be able to rotate.
Decent aviation-grade hydraulic hoses should not allow this to happen. That is why I use them to replace the brake hoses on every vehicle I've ever owned, with the advantage that they will last until long after the frame rots out and the cylinder bores are oval.
My 2012 Civic will warn me if I go above 5 mph with the parking break on. I'm pretty sure this car costs less than maybe 2 years of required maintenance on a Citation.
I have more experience on the bombardier jets, but a Lear 31,45 and 60 WILL NOT hold the brakes if you apply full power. Your going for a ride unless your using big chalks.
It looks like the Chandler, Arizona crashes were flight school crashes, for sure the helicopter which listed both the flight instructor and student as casualties. Your graphics are always exceptional Juan.
JUAN, HI as I recalled there were. DISTINCT RIGHT BRAKES SKID MARKS, THEN ACROSS THE GRASS, initially I said it looks as they were ABORTING but continued on as those skid marks showed up ,,,,, RIP & Condolances to their families 🇺🇸🇺🇸🇺🇸🇺🇸
They never throttled back. During the first 1/2 or so of the takeoff run, the weight of the plane was on the wheels and that kept the wheels rotating. As the plane accelerated, it got lighter until there was no longer enough weight on the tires to make them rotate and they began to slide..
Juan, MY BLOOD BOILED at 18.20 when you read out loud that Cessna, ALREADY HAVE a 'NO TAKEOFF' park brake on warning system available for this model, but was not installed. picnic
The four main tires and brakes all brake engaged via. one parking brake handle. Pretty easy to see how brake fluid pressure could bleed-off 3 of the wheel-brake assemblies and once the aircraft started rolling heat expanded the friction pads. Choking off the take-off roll speed.
Just thought I’d mention as an A/C engineer here in the UK back in the 1970’s. I found that sometimes when releasing the parking brake (on a different make of US aircraft) it would hang up. Meaning that pushing or releasing the control knob didn’t necessarily release the brake. The pressure in the system was not allowing the valve to release, or release properly. As an engineering practice, re apply brake pressure before releasing the parking brake. This should make sure the brakes are off and the parking brake system is off. Some aircraft had quite a basic and rudimentary system, just a push pull wire.
You do something like the acceleration check with a 150 at airports over 6000msl on warm days. It isn't exactly the same, and the margins aren't as critical, but learning in low HP at high altitude .... It's a smaller dog but it has a similar bite.
Cessna will be hesitant to mention anything unless the NTSB does more than just mention the position of the Parking Brake in a report. It will have to directly attribute the cause related to Parking brakes or if Cessna changes anything it is an admission of liability.
Im going to take the acceleration check into consideration, “two good engines” & waiting for V1 doesn’t catch this fault. Point 3 is a possibility since this happened to this type twice or maybe more? Anyone else out there have this happen in some way? I’m guessing 120 is enough to fly an Excel with a normal rotation but this was anything but. Sounds like an accelerated stall, he had to pull too hard to unstick (with that nose down pitching from the brakes) and then it pitched up hard after lift off. I don’t have the numbers on an Excel but online saw typical approach Vref of 106.
Hi Juan - if those wheels weren't locked solid by the parking brake, then as that aircraft picked up speed, those brakes would got hot and will apply more brake power as heat comes into the system. The heat would cause some fluid expansion, and rotor expansion. Surprising the antilock continued to work though! This is a common issue on motorcycles rear brakes when not serviced properly and too full on fluid.
Don't know if it has been mentioned. The Dassault Falcon series (at least 50/900) had a G acceleration meter in an upper corner of the PFD. The takeoff numbers included this minimum acceleration number. It is the only series of civil aircraft I have seen with this but I thought it was wonderful. A quick glance at 80 Kts told you if the airplane was performing as advertised. Left you in a relatively low speed regime for a reject if you weren't accelerating properly. Anyhow, Excellent breakdown Juan!
Man.. so sad to hear about that midair in Chandler.. I was just thinking how nice it was that I hadn’t heard from Juan in awhile.. condolences to the family.
It’s very easy to tell that Juan has many, many hours of flying time. So focused and thorough; he knows a tremendous amount about a lot of aircraft. I just love his analysis.
What I like about Juan is he has so much aviation information in his mind, he has to page through his memory to access the information for the particular item he’s talking about. He has to pause to figure out which terabyte the information is on. As a parent it reminds me of a young child trying to make up a story. Two similar looks two VASTLY different situations. Juan is a walking aviation Wiki. Thanks Jaun.
@@jimsteinway695 I Believe that hs Hesitation is a well developed of ENGAGE the BRAIN before engaging the Mouth. A feature that (In the words of one of my old TI's at Chanute AFB in '65 would say) It would 'BEHOVE YOU TROOPS' and many Politicians and us to accomplish.
Juan was trained by the best: United States Air Force... (fka US ARMY Air Force), with an unbroken chain of excellence and innovation going back to the earliest days of powered flight. His airline is lucky to have him. OTOH, many at the controls of today's bizjets and turboprops went to Joe's Flight School, in Podunk, and just did NOT have the safety and PIC discipline drilled into them. (If no one YELLED at you during flight training, you are vulnerable to... doing the wrong thing, at the wrong time... pity.)
I prefer not to slather all over the place with slobbery praise and overly emotional sentimentality. Juan definitely knows as much as anyone, if not more, about aviation topics but in my humble opinion he needs to work on his presentation just a little in order to take it to the next level. Sometimes the stop and go recitation gets to be a little frustrating and while it boarders on potentially being a significant part of his style I'm of the opinion that he may need to relax just a tiny bit during his presentation and it would be a significant improvement for him; maybe he simply needs to rehearse his lines once or twice before doing a take or even repeat his lines in the mirror in order to make a vast improvement for himself. He's still my favorite aviation authority no matter how much he rehearses before his 'takes' and of course its his business how he runs his show, not mine. I always seem to have more critical thoughts towards the flood of slavering, kowtowing hangers on that constantly emote all over youtube; compliments are one thing but America seems to be so choc full of effusively sentimental, thin skinned wussies. Seriously, sometimes the comment sections of these videos read like cheap, overdone romance novels.
@@CRSolarice Since when is praise for doing a great job a negative thing. Hey Karen, if you can’t say something nice, just pass on by. Nobody wants to read your negative comments.
Something to consider. As an aircraft mechanic I have observed this sequence several times. Aircraft taxies to the GA ramp. Sets the parking brake. Locks the airplane and leaves. Several hours later the line crew has to relocate that aircraft. They hook up and as the they are able to move the aircraft they start the tow. Soon they notice that the tug is slowing down and very soon after they realize that the brakes are set. That is when I get a call! If we can’t get in touch with the owner and the aircraft is on a taxi way I release the brakes by loosening a bleeder on each mlg enough to release the brake. What happens is the brakes were hot when the parking brake was set. The were cold when the tow was started. However, dragging brakes rapidly heat up and expand. Dragging brakes now become locked brakes. Citation multi disc brakes will do the same thing. If the pilot set the parking brake to prevent the aircraft from rolling at idle and no more than that we have the same problem. Those big engines will move the aircraft into position for takeoff however, as the roll begins the brakes very rapidly heat up and soon they are locked. I believe this parking brake was set. The amount of braking is determined by the amount of peddle pressure applied when setting the parking brake. It is just a valve that closes off the fluid to the mlg brake caliper. The only way for that fluid to return is by opening the parking brake valve.
This exact sort of parking brake is offered in the aftermarket to - of all things - kit car builders. Often times, there is no way to have a proper emergency brake, so the existing calibers do double duty. Just like in the aircraft, the pedal is depressed and then the valve is shut, holding that pressure in the lines and caliper. So in the plane, the pressure is totally dependent upon how hard the pilot presses the pedals when the button is pushed, so the parking brakes can absolutely end up with anything between zero and 100%.
Excellent review. You and Mentour pilot are UA-cam's best accident reviewers. And your presentations, already top-shelf, are improving with each (unfortunate) review. Thanks.
Hello there👋👋,how are you doing today?hope you’re having a wonderful day?GOD BLESS YOU!!!💕
@@amytaylor8910 Hello, Amy. Are you friends with the &&& pilot, Juan Brown? (blancolirio) Hope you are smiling.
@@kevinferrell6466 hey. No I’m not. Yeah I always try to smile. Where are you from?
@@amytaylor8910 Clearwater florida. And you?
@@kevinferrell6466nice place. I’m originally from New York but I live in VA. How’s the weather there?
see accident report of "Cessna Citation 560 Ultra, VP-CSN" in 2003 in which the parking brake was inadvertently partially or fully on at touchdown. Pilot subsequently had their company checklists amended to add Parking Brake OFF, before take-off and before landing. " Furthermore, trials conducted by the operator, subsequent to the accident, showed that it was possible to move the aircraft at speed with partial parking brake selected. "
Why is there a "partial parking brake" selection? The Europeans have noted several accidents with these types of aircraft whereby the parking brake was either not releasing or residual pressure in the system applying the brakes, as Juan suggested. A simple electrical circuit on the wheels should be installed to monitor actual wheel speed vs. ground speed, wheel slippage could then be calculated.
@@alexaltrichter1597 Or "Anti-Skid-in operation", means it is modulating the brake pressure. I would wish for an automatic release of the parking brake by throttle advance. Either this disengages the brake lever or the throttle cannot be advanced when the lever is not fully released. How many times have I set the parking brake on my car! And only when I got of the gas I notice by the rapid deceleration that the brake was still on. Despite having an indicator light in the panel! 🤢
It appears to me that this is a design flaw. If Cessna refuses to fix it, it's up to us to get the word out AND when you are a pilot flying these airplanes, take personal responsibility.! Add parking brake check to your checklist yourself!
Spread the word to every single pilot you meet flying this type of aircraft! If we work together, we CAN make a difference!
Disclaimer: experience from auto hydraulics may not apply here, but maybe?
There is a condition where a hydraulic master cylinder does not quite return fully, which it needs to do, to open the system to reservoir(=atmospheric) pressure and equalise. Although there is little or no system pressure at the time, the system is closed and any expansion (due to heat in the wheels?) can cause pressure to rise and brakes to drag increasingly with time. In extreme cases, they can lock on.
In cars and motorcycle hydraulics, the solutions are
1) make sure the master cylinder piston physically returns *fully*. If the lever is adjusted wrongly, this can't happen reliably. And it's not enough to only check for no system pressure.
2) make sure the control lever is operated fully off each time, with no exceptions.
Apologies. I was interrupted by family and missed an important part. The parking brake valve takes the place of 'master' in what I said above. ideo mkes it clear that a sticking valve, or pilot leaving it set with the brakes only partly on, could cause this problem. I'd be hoping for a change of procedure AND a warning of brake pressure while engine revs are up enough for takeoff.
I was taught how to do a acceleration check speed@distance in the first few take- offs fir my PPL training. And it was reinforced regularly becoming instinctive after that. I get goosebumps that commercial charter pilots flying jets could somehow not have that as pert of their essential awareness regimin on take-off. I was trained in South Africa, only PPL single engine. Thanks Juan for all your fantastic videos.
Question from a non-pilot:
How do you measure distance during take off?
@Matthew H If it is a regular use airfield you know where you should have at least a certain speed depending on the aircraft you are flying. Otherwise time is a measurement. If you are experienced, and with lighter singles you can immediately within a few seconds feel if acceleration is normal or not. It is much more procedural with commercial flying and the airlines. But the basics are the same.
Grateful for the clear explanation of the issues here. Retired after 45 years in navigation aids, radar, and comms in support of civil aviation. As Scott Manley says 'Fly Safe!'.
Videos like this makes aviation safer for all. It takes time to pull all the information together, then make the video. You can't expect someone to do this week after week, while also working his regular job, for nothing, do you??? I'm glad we have something like youtube where we can get this great information all for free while the guy doing the work gets paid also. It's a win win for all.
But he is no where near being renumerated commensurate with the great value, in terms of human lives, prosectively saved.
Patrion goes some way towards it. Juan was my first one
For this type of video, Juan gets no remuneration from UA-cam because UA-cam considers it "sad" or something like that. He depends on Patreon for his accident reporting videos. Utterly stupid Google policy given that air safety is almost entirely based on the analysis of accidents and the lessons learned, and also increasing public confidence in aviation. Why can millions be made by the Canadian and other corporate producers of the "Air Accident Investigation" shows on cable TV but private individuals such as Juan cannot on UA-cam ?
I just turned 47, and have started flight school. And really watching Juan has taught me a lot. Not replacing my instructor, but in teaching me this. The checklist is so Damn important, being aware of things you may not see in the checklist is just as important
I owned and flew a C560 or Citation V for several years. A couple of notes; I don’t recall the parking brakes ability to hold back two P&W JT-15 Ds with almost 6000 Lbs of total thrust! So our procedure was to release the parking brake on taxi, check brakes for rolling and stopping while taxing on both sides (left and right) and never touch parking brake handle again. I ‘believe’ a partial engagement is possible and the activation of anti-skid is also possible with brakes heating and locking while aircraft is rolling and the system would not know of a ‘partial engagement’……
@blancolirio you're missing a critical point: the parking brake valve only traps the pressure applied when it is set. It's entirely possible to depress the brake only very lightly when setting the parking brake. The drag may not be immediately evident to the pilot on the next taxi to the runway but it would be more than enough to heat up the carbon brakes on the takeoff roll.
Correct. It is also likely that if you're just using the P brake to stop it from rolling to grab a clearance or something you would not push hard on the brakes before trapping pressure with the P Brake, just enough to stop idle thrust from rolling it. Also, carbon brakes get better with heat which increases the problem on ground roll. Lastly, at fwd CG limits It feels to me that there is not a lot of "extra" elevator authority to rotate around Vr speeds, I don't feel like it would take much brake drag to cause "no rotation". Cessna should add something to trigger the "NO TAKEOFF" light if there is any trapped pressure in the system.
XLS serial number 6001 and up wiring diagrams show a proximity switch at the parking brake valve lever that is supposed to trigger the no take off warning annunicator. N560AR was SN 6026.
Thanks, this helps clarify one of my questions if there was a speed warning / no take off condition annunciator on this complex bird.
hmmmm interesting. Euro models only?
@@blancolirio The wiring diagram doesn't specify European certified aircraft, the print is applicable for aircraft serial number 6001 and up. The IPC lists the park brake proximity switch being effective on earlier serial numbers that were British, Denmark, and French certified aircraft.
@@jasonross3294 USA Certified aircraft do not have the proximity switch regardless of aircraft age or serial number, the wiring is not present in the aircraft I am familiar with that is SN6100+
@@blancolirio USA Certified aircraft do not have the proximity switch regardless of aircraft age or serial number, the wiring is not present in the aircraft I am familiar with that is SN6100+ The X+, Sovereign +, Latitude, and Longitude all have a No Takeoff CAS Message through the G5000 System for parking brake on, that is incorporated into the throttle system. I do not believe the CJ3+ or M2 with G3000 have a CAS for P Brake on
I flew Cessna 400 series, CE500 series and Citation CJ series aircraft. Parking brake controls appeared the same on all aircraft. My procedure on releasing parking brake was to pump the brakes after the parking handle was released to verify the parking brake was released . LR45 has parking brake warning on takeoff configuration ICAS. Bombardier certified that aircraft the same FAR25 certification requirements that the B777 met. Europeans were smart requiring this configuration warning for this. Cessna will stick by there present checklists to evade a lawsuit. Excellent video
I hope the NTSB has enough brains to recommend this change not only in its final recommendations to Cessna but also to the FAA to "require" this, thus giving Cessna a legal "out" to make the change "...only because the FAA unnecessarily required it...". Future safety is more important than Cessna paying for their negligence, much as they ought to.
Is it possible for the anti-skid system to vary the hydraulic brake pressure felt at the brakes with the parking brake engaged? Or would the parking brake valve, when engaged, prevent the anti-skid system from varying the hydraulic pressure going to the brakes?
@@thisisnotmax From the schematics I take it that the parking brake lever simply applies any pressure that is in the system to the brakes. Upstream in the brake line is the ant-skid-controller which modulates the pressure. From the picture of the skid marks it becomes clear, as Juan mentioned, that the wheels were skidding more and then less again. The stripe was not continuously the same strength.
Bummer all around Juan. Great video, keep it up. Thanks!
Its refreshing to have the experience and expertise of a great pilot analyzing these incidents with the purpose of keeping US safe so we don't screw up and make the same mistakes. Great job Mr. Juan Brown! Very much appreciated!
Great update. I really appreciate your perspective clearly underscoring the "takeaway" lessons from your reports on mishaps. No histrionics, no sensationalism, and value added from your professional pilot experiences. (You reminded me of a hydraulic parking break valve I had added to one of my POV trucks. I believe the lever did not release the brake fluid pressure unless there was pressure from the foot pedal, too.)
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Some quick thoughts - If the parking brake isn't fully released - the system partially pressurized, then the wheels will roll, with some drag, until some of the weight on the wheels is relieved as the wing starts to lift - at which point, the wheels would lock, as the friction of the brakes exceeds that of the wheels on the runway. At that point, the antiskid would detect the lockup and relieve the pressure, then the brakes would lock again as the antiskid cycles.
Other thought - since the parking brake valve is holding the pressure released into the system by activating the toe brakes, if the toe brakes are only partially applied, then it's possible to have a partial application of the brake that isn't enough to stop the airplane, but will hold it back. From teh system diagram, the parking brake valves are check valves - one-way valves - they'll hold the brake pressure at a certain level, but will permit additional pressure to be added by normal brake application, but not released.
Almost, but antiskid is before the parking brake system and can't effect pressures after it. (It just locks the pressure in after it). The skid marks are likely from suspension hop as the tires lose grip.
Juan, tomorrow I will study and understand “Minimum Acceleration Check Speed” for my Saratoga Turbo. It won’t move with the parking brake set but it will move with it half set, ask me how I know. I’ll figure this out and make it part of my takeoff check, like oil pressure, manifold pressure, airspeed alive. I participate in the Wings program every year and I’ll talk to my instructor about it. I’ll even check with our wings region person to see if this is covered. Thanks Juan!!!
"ask me how I know" - We don't need to ask, lol. Thanks for the report; it may go a long way toward safety in the future.
Great analysis, as usual, and that 50/70 rule is a handy cross-check. Regarding the annunciator system for the PB, every automobile has a red dash light that shows 'BRAKE', and many newer ones have annoying dingers that at least indicate something isn't right to start rolling. Brake temperature warning might have some use in helping identify this problem along with a warning , and since brake pressure is monitored, residual pressure with brakes released would show a condition of fluid trapped in the wheel caliper areas. I've heard in the past of aircraft that actually got off the ground ok with the dragging brakes on fire, then retracted into the wheel wells, and then.......... I've been within 20 feet of a KC-130 tire that blew off a shattered rim during towing, and it has enough force to de-skin a wing.
Been watching Ryan at Missionary Bush Pilot for a while and he always picks his spot for "air speed alive" before advancing the throttle. If I was a pilot, I would add the p brake to my checklist if it wasn't already there. Never take anything for granted.
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As a Fixed wing man MANY MANY MANY Moons for Uncle Sam, you are IMHO Thee BEST for attention to detail and and there is NO 1 Else I watch. As the old saying goes “Take offs are Optional but landings are Mandatory”.
Great Job as always.
SB is needed to add the brake config to the take off config parameters like in the challenger 604. With the brakes set and throttles forward you get a T/o config brakes.
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You have the ability to explain what few of us would ever understand on our own. Great job. Thanks again
Contamination of the park brake shutoff valve could very well leave pressure in the circuit downstream....that's a very good point Juan.
Great video, Juan! You explain what had troubled me about this accident: IF the pilots had for some reason aborted the takeoff after V1, which everybody was assuming was the reason for the tire marks on the runway, WHY did the witnesses seem to indicate that the engines were at full takeoff power throughout the accident sequence ("normal" sounding to a witness beyond the runway end until the one engine evidently ingested something from the power pole), and why did they fly for a distance? That's not the typical abort-after-V1 profile. We assumed it had to do with the elevated runway, perhaps, but it didn't feel right. This sort of explains it. And the report indicates, as you note, that indeed the engines were at takeoff thrust throughout the sequence.
The one witness's observation about not seeing the nose wheel off the ground at the intersection, and the observation that the a/c was moving slower than usual, suggest that some level of braking was being applied very early in the takeoff roll, retarding the acceleration and holding the nose down. And yet the skid marks and antiskid "chirps" don't appear until well down the runway. How was it that the tires were rotating on this aircraft at all with the parking brake on, and if takeoff thrust was enough to overcome the parking brake, why didn't we see skid marks until they're 2/3 down the runway? Was MORE brake pressure applied by the system later in the roll? How does that make sense? One possibility is that the lift component from the higher speed as the accelerating aircraft got towards the end of the runway would make the aircraft lighter on the tires, reducing friction between the rear tires and the ground so that the ground wouldn't turn the wheels and instead they would skid. (Indeed, maybe that's the explanation.) If so, that supports the idea that the parking brake was applied from the very beginning and indeed takeoff thrust in this thing is enough to overcome the parking brake (as it is in my automobile). If that's the case, then Cessna indisputably needed to have the parking brake as part of the NO TAKEOFF warning system. With the brake on, and takeoff power applied, the aircraft behaved normally-ENOUGH that the pilots didn't immediately decide to abort.
What is truly-disgraceful here, and I know you're too polite to say it, is that some European agencies (or smart customers) apparently required that the parking brake be part of the NO TAKEOFF warning system, so Cessna plainly has the wiring and computer logic already in place to provide this safety measure but decided not to include or activate it in US-registered aircraft.
This also reminds me a bit of the Ameristar Charters MD80 accident, where the Captain (who had a zillion hours in DC9-series aircraft) pulled back on the yoke, got nothing, pulled further, still got nothing, and immediately aborted even though he was beyond V1, basically saving everybody. NTSB said that had he taken even a couple of seconds to think about it before aborting, everyone would have died, as they would if he had tried to take it into the air, because it was under no circumstances going to fly. Being present and fully-focused in every moment of the takeoff is what allowed him to react decisively to an anomaly, whereas these poor guys evidently didn't have that edge-of-their-chairs, looking for reasons not to depart, knife-edge awareness that would have allowed them to timely abort. I like the guy who says that every landing is an aborted go-around. Perhaps there's a component of that mentality that would have saved lives here.
@William Candee referring to the first part of your post about the skid marks, maybe the tyres were rotating initially (assuming the parking brake was ‘partially’ set) but wore a flat spot. The flat spot might only grab slightly for a start but it would grow to the point where it’s just going to lock into that position on the tarmac and leave a continuous skid mark. This might even explain the intermittent darker patches which have been attributed to the ABS.
I have had a citation accelerate with the brakes locked during ground runs..it went about ten metres before I got the power back...
I know of another 560 citation went half way down the runway on take off with the wheels locked and on fire..
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spot on Juan - make the parking brake a part of the master caution system!
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I’d add my son (real pilot) and me (guy who pays for pilot) tried this takeoff in x-plane and MSFS. I gotta say on the best day, it’s pretty close to the runway end lights when the citation lifts off (without the parking brake) on that same departure. He managed to get a 737-max and a 767 off with actually a shorter roll. But as you note, there is zero margin for error here. It must be money that they’re based at Robertson field given that Bradley international (with its 9500’ 6/24 runway) is about a minute away by plane
In the AIRBUS the parking brake was an called audible “BRAKES RELEASED” or “BRAKES PARKED”. Seemed to work fine.
Went to A&P school with one of the pilots he was always very professional and had been a pilot for some time when we graduated.
Excellent report, as always, Juan. Ididn't know, stuff like this could even happen...
Thanks Juan, it’s so good to have your amazing in depth expertise on YT. 👏
Humans are amazing at finding a way to make a aircraft system work against them. If there is something that can be done wrong, it's only a matter of time before it's found. The FAA's job is to act as quickly as possible to avoid this from happening over and over by acting a tad faster in reporting the incidents
One possible explanation is that to land on that short runway requires heavy braking. The Citation landing distances are dependent on touching down at the correct speed and with aggressive braking. Not the kind of braking that most pilots carrying passengers apply. Heavy braking heats up the disks and the pads. Then the aircraft sits and the disks and the pads cool down. So with the cooling, the brakes are not effectively on (the pads are not pushing against the disks). Then they take off with the parking lever still pulled, parking brakes on, and as the aircraft accelerates down the runway the pads and disks heat up and all the sudden the brakes are on (pads applying pressure to the disks) and the skid marks start. With the brakes cooled down, the aircraft might taxi normally and the pilots didn't realize that the parking brakes were on.
Very professional and thorough presentation Juan! Expect an FAA Airworthiness Directive to be issued in the very near future to address this problem. I see the installation of new parking brake valves on the Excel series of aircraft and then the possible install of a redesigned valve when they become available. In addition, the parking brake position will have to be incorporated into the "No Takeoff Warning System". If this modification is not feasible, then an independent subsystem will have to be designed to trigger the Master Warning System when the throttles are advanced to the takeoff position and the parking brake is in the set/on position. Flight Manual and checklist amendments will have to be included as well. For your information, the larger and more elaborate models of Cessna Citations have the parking brake position monitored by the No Takeoff Warning System. The 560XL series shares it type certification and type design specifications with the original Model 560 and was delivered as such.
Probably 3 years from now.
Less than full brake system pressure can be trapped in the brakes under the following scenario. The brake metering valve, which is controlled via the toe brakes, modulates brake pressure from zero to a little over 1000 psi. What happens is the pilot applies just enough brake to stop and hold the aircraft (which is at idle thrust) then decides to set the parking brake. At this moment, there may only be around 300 to 400 psi trapped in the brakes. Moving the aircraft forward again while forgetting to release the parking brake is easy, just add power and it will roll forward. It will definitely require more power than normal to maintain or achieve a given speed. Bottom line here is when setting the parking brake on a Cessna Citation is to fully depress the toe brakes so the brake metering valve can apply maximum pressure to the brakes.
Juan, there is a reference I saw on the checklist for Brakes on the static roll and rolling take off to release, but nothing on parking brakes. I'm not a pilot, but you'd imagine there had to have been a lack of performance immediately if they were dragging brakes. Great job on this, fascinating and sad we have to lose people in order to update checklists, flight control systems... excellent video.
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Parking brake on. Hmmm.
One other thing what about the Citation that crashed in Sheep mountains on a flight out of Troutdale, Oregon.?
Since a long time I'm thinking about a takeoff acceleration warning system.
Thru the GPS it should be possible to evaluate the exact position of the aircraft on the runway at any time.
So it's easy for the FMS (which has a database of runway lengths of all airports) to calculate the remaining runway in front of the aircraft at any time.
When FMS now do calculations with the actual speed and actual acceleration values, it should be possible do determine the estimated takeoff position.
And when it is beyond a specific safety margin, the FMS should give a master warning!
When I set the parking brake on my car, I ALWAYS jam them on as hard as possible. I don't want there to be any doubt when I try to drive off that the parking brake is on or not. I nearly burned out the brakes on my wife's car one time because I didn't know that she had set the parking brakes on weakly, and the car drove almost normally. Luckily, I detected the problem in time.
Dunno know if this is how aircraft parkng brakes work or not, but it's good advice for us folks who only drive non-flying vehicles.
My 14 year old Jeep has a parking brake warning light and it also beeps loudly at me if I try to drive away with the parking brake on. It also gives priority to the brakes over the throttle, so that if both pedals are pressed, the throttle drops to idle immediately, even if the throttle pedal is still being pressed. If you have a "floor mat incident" where the throttle sticks at full, all you have to do is press the brake pedal and the engine will go to idle.
That reminds me of a class mate when we were around the age to get driving licenses. He pulled up in his fathers BMW before school and told us prod that his father promised him this car. He went silent when we questioned the skid marks and the red glowing rear drum brakes 🤣
Great stuff Juan. As a high time c500,c560xl, c650 (all same brake) guy I can tell you the brake almost hits your right knee when pulled. The parking Brake pressure is directly related to the pressure applied to the pedals BEFORE the parking brake is pulled! There is NO accumulator. It is very common for a citation to go rolling off a sloped ramp if the chocks are pulled. Because not much pressure was applied to the toe brakes. I personally have had an airplane change parking spots with a co-pilot sitting in the airplane un aware he had moved 60ft down the ramp. I can’t imagine how someone can take off with the brake on(SMH). But I really looks like that’s what they did. Damn shame. Also I always use a parking brake! If my head goes down to do anything to the fms, to brief a chart, or take my eyes away from outside the airplane the parking brake is set. The last thing you need is to accidentally move! I’ve been in several airplanes that the pilot flying released enough pressure to let the airplane roll, with both heads in the cockpit. This always results in a panic stop and one of the pilots saying an f word!
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Iirc, the brake lever near the pilots right knee in the C650 is the emergency brake, not the parking brake handle. The parking brake handle is behind the center console and is pulled up to engage and pushed down to disengage. That’s from memory which is years old though.
I do have a pic of the 650 cockpit and the emergency brake handle by the pilot’s right knee is just to the left of the emergency gear extension handle.
@@speedlever I had forgot that. Been awhile out of the 650. I do remember that control lock down in the center that we used. Thanks for the correction. I went form the 650 to the 560xls, sure I still have a little of mix in my head. Strange mix of everything in the xl.
@@tymatt4555
No worries. Been years out of the cockpit for me. Flew a bunch of different Citations but never had the pleasure of the 560xl. I loved the 650 (III and VII). I hate to think all I’ve forgotten.
@@speedlever the 7 was a great flying airplane. The xl not so much, heavy on the controls and main gear way to far aft of CG. But it’s a hauling truck, with good field performance on that straight wing. And lots of baggage space. I’m in the falcon 2000lx now and it flys almost as nice as the 650. But lots more power and range.
According to the schematic shown, if the parking brake were "set" with only moderate/light pressure on the brake pedals, the lowest part of the system would be holding a partial brake pressure, a drag but not a full hold-back-against-the-engine.
The antilock system would not have any influence when the parking brake valve is set to ON since it is the last valve before the actual brakes.
@@bobroberts2371 That is what I thought at first glance. Careful review of the schematic showed me otherwise. The actual last valves are the A/S Shuttle Valves, which actually release the brakes when a skid is detected.
One thing that i have observed and no one is talking about is, even as the parking brake may have been set at minimum setting, as the wheels turn the brake pads, rotors and calipers heat up tremendously. Which causes the fluid in the caliper to expand and apply more brake. I "IMO" believe that is why the skid marks were not seen except on the far end of the runway. When I learned to fly back in the day, my instructor had me use the toe brakes to do a run-up.
@@RyeHillBaptistChurch Good point. It appears (looking at online documentation) that this build-up is one of the things the A/S Servo Valve is supposed to alleviate, but with the P\B Check Valve set, this alleviation would be negated.
@@bobroberts2371 ...(more) Looking at the technical documents for the A\S Servo Valve, the function of this valve is to provide a constant supply of brake fluid corresponding to the applied pressure on the pedals as the A/S Shuttle Valves release fluid, thus preventing pedal sink.
Yet another expert dissection of a tragic accident, sir. Much to be learned here.
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Yes, we had a similar occurrence on a Citation XL about 15 years ago. During takeoff the aircraft would not rotate, crew aborted and stopped safely. I do not remember whether the parking brake had been set accidentally or whether the brakes locked up partially due to a defect. In any case, those XLs will not rotate in such a situation, period.
On the current type that I fly we do have an "acceleration indication" (g-force) on our PDU (primary display units) and during takeoff there's an official callout "acceleration checked" at about 50 knots. Potentially a life-saver!
Agreed these definitely need a brake/throttle interface that prevents the throttles from being advanced, or an audible TC warning that would sound, if this were attempted during normal flight operations.
In this case the brake(s) may not have locked completely until friction heat caused enough expansion to defeat the ABS system.
Good report Juan, thanks.
All my career each time I pulled into position or unto the runway for takeoff I performed what I called the suicide check : flaps, stab trim, bugs and brakes and at the beginning of the takeoff roll...slight .and pull on the elevator to see if there is movement.
Yep, pretty much how I did it as well. Like your handle. I loved flying the DC8.
Good job Juan. Forgot to mention that the crew should have Aborted with a loss of directional contol prior to V1, which is part of the standard takeoff breifing. A Monday morining QB would have used wet runway V1 data on this short runway. This would give them more runway available to stop on if a rejection was needed.
I commented in your initial video on this crash that it was the parking brake on. I personally witnessed a takeoff from the right seat in a citation a few years back where the captain forgot to release the brake after an extended line up and wait. It took almost all of the 8300’ runway to be airborne and we burst a tire on landing. The first thing you think about is the engines are not making power. It wasn’t until after rotation I looked over and pointed out to the captain the parking brake was set and told him not to raise the gear which he did anyway.
They have no chance on a short runway like that.
There was definitely a distraction to the crew right before taking off leading the captain to forget to release the brake.
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In the MQ-9 Reaper, we had an acceleration time check. It's not what I'd consider a high performance aircraft, but it's flown like an 11k pound turboprop. We calculate TOLD data, including V-Speeds, and time to 50kts. When I takeoff, I call the seconds on the clock in the HUD. "FULL POWER, 12 ON THE CLOCK." If our acceleration time check is 17 seconds, both crew members know to look for 29 seconds on the clock. The Sensor Operator acts much like a copilot, and monitors the speed check. Usually it sounds like "50, SPEED CHECKS," and I'll look at the clock and speed as well, and call "GO." It's a good and critical practice. We have different criteria than standard V1/V2 etc, since it's a single engine aircraft, but it's proven to be a good, safe procedure.
Excellent!
This is not a shot fired at you, just an observation. But I never realized how often the Air Force crashes drones until I went to AMIC ("safety school"). And how frequently they go lost link.
There are a lot of unique challenges to flying drones.
Proper (and easy to remember) Physics is always a good thing in aviation!
@@MattH-wg7ou I knew a couple guys in the air force who were stationed in Korea as maintence crew on the Global Hawk... One of them swore up and down it was a manned aircraft, and he WASN'T joking..... Scared the shit out of me. Lol Unless DARPA is up to some really crazy shit, and he was saying things he really shouldn't have been saying... I'm pretty sure someone is stupid in this situation, and it isn't me. The hell kind of maintenance was he doing? Haha that was over 10 years ago and I still laugh about it to this day. I really hope some senior enlisted was playing a prank on him and had him convinced like, a pilot climbed in there when nobody was looking and you couldn't see him, cause no windows..because otherwise. Man... I don't know what to say.
Thank you from your explicit information, your explanation has been great thank you , this is why i love to listen to you , being a novice .
I think arrival position is where they would start their take off roll, opposite end to take off end. Arrivals end would be where arriving planes would touch down.
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The locals say MAN-ee-oh (think manny-o). MAN-tee-oh also works and that is what you will hear in most of NC. Wonderful little place on Roanoake Island just before the Outer Banks. Have been fortunate enough to visit the Carolina coast many times.
I really enjoy your channel Juan, especially the level of detail you go into. Thanks for all the time you put into making these videos for us.
The parking brake valve traps whatever pressure is applied to the brakes when the parking brake is set.
Best procedure is to stand on the brakes (with power/28v on) to energize the power brake pump, stand on the brakes, then set the parking brake. Newer airplanes have done away with master cylinders on the rudder pedals entirely, pedals just apply inputs to the brake metering valves downstream from the electric brake pump.
Any other procedure just traps whatever residual pressure happens to be in the system. Sometimes its enough to keep the airplane from rolling, especially with new/good brakes on a level ramp Worn brakes? Sloped ramp? Maybe, maybe not.
Another issue was related during a line shack BS session about this. C560 was chocked, needed to be relocated to other side of field. Guys hook up, start towing it across. Had to stop before crossing the active. Start to pull again, wont move. Brakes are locked. Parking brake set in cockpit, aircraft door locked. Pilot had to be called out to unlock door and release the brakes.
The consensus was that the pressure gradually increased as the dragging brakes temp increased, thus locking the brakes when stopped
Same system has been used in the 500 series since day one, along with the 650s. One might ask why there is suddenly a problem.
The 560XL/EXCEL has an abundance of power, compared to the earlier 500 series. When mechanics do ground runs, especially when you need to run it above 85% and are light on fuel, its good practice is to stand on the brakes, apply the parking brake AND chock the main wheels.
Its easy for the airplane to overpower whatever drag coefficient there is between tires and pavement.
So why does this problem occur recently, when the parking brake system has worked fine for the previous 40-50 years?
I'm just guessing, but one of the factors may be that there are a bunch of pilots out there who dont know, or care to understand, how their airplane's systems actually work. You will debrief these guys who write squawk scenarios that "cant happen", then get the "deer in the headlights" look when you start asking for more details.
Any mechanic/AMT who has spent any time at all debriefing flight crews can tell you this.
In all my years of flying different type of aircrafts, I always perform and use the BFATS check; Brake (parking brake OFF), Flaps(set for T/O), Airspeeds(Posted, reviewed), Trims(set for T/O) and S for safety ( T/O clearance, seatbelts, etc). Never failed me. And for God sake Cessna please incorporate the parking brake into the take off warning system! Stay safe everyone
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Great video. I did alot of single pilot flying in my career. I agree to not setting the parking brake after taxiing begins with some exceptions. When i was single pilot and got a line up and wait i would stop at an angle so i could see the final over my shoulder. Departing from a high speed taxiway at a busy airport would present a problem so when i pulled onto the runway i turned a little to see the final. Controllers are awsome but human,
Great report Juan. My Granddaughter has her PPL and is now doing CPL. My god this flying business is complicated just trying to get airborne. Hate hearing about crashes. May those poor people Rest In Peace. 🙏 🇦🇺
From the diagram and your description on how to set the parking brake, I can imagine the following scenario:
The pilots brought the plane to a normal stop with normal braking force, then set the parking brake. The set parking brake just kept the pressure the pilots had applied at the time they set the brake. Aircraft didn't move, engines at idle. When they were finished updating the FMS, they advanced the throttle, maybe slightly wondering why they had to apply a somewhat higher thrust to overcome the resistance of stopped wheels.
They didn't stop again on the runway but just opened the throttles for the takeoff run, not noticing they were still applying a normal braking force. Since they didn't do the takeoff performance check, they thought they were accelerating normally and tried to take off. The result was this crash.
If the park brake was on, cycling the antiskid should have released the brake. But the Cessna schematic shows the park brake is a check valve, which means the antiskid servo would pump the pressure back up again with the park brake holding the new pressure. That's the part of this design that sucks, IMO. The park brake check valve should not be where it is in 17:21 schematic, but perhaps rather between the power brake valve and antiskid servo valve.
It's a wacky system that has never been brought up by Cessna in detail. The Latitude, Longitude, Sovereign + and X + have No Takeoff warnings with the P Brake on... I'm not aware of any other Citations that do. It could be fixed by adding it to the micro-switch that is already in the throttle quadrant that annunciates No Takeoff if flaps are beyond T/O, speedbrakes deployed, or out of T/O trim... why the P Brake isn't on there is mind boggling.
@@oreo10111
I'm surprised that the high-end Cessna jets that you mentioned
above don't have parking brake NO TAKEOFF warnings.
In the Citation 525 M2, there's both a NO TAKEOFF CAS message on
the primary flight display whenever the parking brake is set. And when
you advance the throttles for takeoff beyond the cruise detente, the
warning becomes an oral warning. Why is it the case that the
lower end of the Cessna jet lineup has more sophisticated parking
brake warnings? Is it because all of the planes that you mentioned require
two pilots a and they should know better working as a team? Or put it
another way, catch each other's mistakes?
In case some don't know, the Citation 525 series is certified for single
pilot operations.
It would appear that the parking brake would only be applied as firmly as the service brakes were applied while the parking brake knob is pulled out. Could conceivably be applied just enough to not really be noticed, but still enough to interfere with the takeoff... Also, pulling up elevator would drive the braking wheels harder into the ground. A really bad deal.
Thank you, Juan. I'm just a VERY casual simmer, but everything felt wrong about this one. I went and flew a short runway in MSFS 2020 in a Citation, and it definitely goes by quickly. In the sim, the parking brake is just on or off (as far as I know; maybe it can be configured) so the problem wouldn't have ever occurred to me.
It's very sad that something like this cost lives. I hope Cessna makes those changes.
I wish everyone connected with aviation was as dedicated with regards to finding out cause & effect and making sure it doesn’t get repeated causing loss of life & airframes. Thanks Juan for all you do to help keep aviation safe.
Non pilot here but love watching these videos, thanks for sharing
Juan, nice video, but clearly the parking brake is working as intended.
As a mechanical engineer I believe what is happening with the skid marks is that enough lift was generated to allow the tires to skid, the suspension unloaded (moved down), traction re-established, suspension loaded until slip and repeat.
Think of tire hop of a car accelerating, just in reverse.
The ABS is upstream of the parking brake and can't release parking pressure or reapply parking pressure.
While I don't have aircraft experience, I have extensive automotive and industrial experience.
The diagram is more of a theory of operation rather than exact schematic however there is enough detail to sus out operation.
Working the system from top down.
Dotted black lines
are electrical connections
Purple lines
are hydraulic system returns ( from the basic diagram it appears that when the toe brakes are depressed, this bleeds pressure from the control side of the Power Brake Valve. The output of the PBV is what applies the brakes. This is a fail safe, if a toe brake valve leaks the brakes apply rather than not being operational. )
Green lines
are returns to the supply reservoir .
Red lines
are what applies the brake calipers.
Blue lines
are the emergency braking system.
Working the system from bottom up
Shuttle valves at wheels.
This selects between the service braking system and the emergency braking system. This is basally 2 check valves per wheel that automatically select between the two. If the emergency braking system is applied, the rest of the system has no effect, the brakes remain applied.
Parking brake check valves.
When the parking brake lever is in the OFF position, fluid can flow in both directions. When the parking brake lever is in the ON position, fluid can flow to the wheel brakes through the check valve but not away from the wheel brakes. This means that the pilot can move the parking brake lever to ON then push the foot pedals in order to set the parking brake. If the parking brake lever is set to ON and no other action taken, the aircraft will still be free to roll.
Anti skid servo valve.
This is what bleeds pressure from the red lines in order to release the brake caliper preventing the wheel from skidding. From the diagram, it DOES NOT have the capability to apply the brakes.
Power brake valve
This directs hydraulic pressure to the rest of the system when the toe brake pedals are depressed. The system is set up so a pressure reduction in the purple lines causes the valve to move allowing pressure to flow from the accumulator to the rest of the braking system.
Accumulator / hydraulic pump
This is where the system gets operational pressure. This system acts more like air brakes on a large truck than hydraulic brakes on a car.
Toe brake pedals
This bleeds pressure from the Power brake valve to the reservoir to allow the service brakes to apply.
Weight on wheels switch ( not shown )
Juan replied that this arms the anti skid system when the aircraft is on the ground.
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Part 2
So, if the parking brake lever is in the ON position, the brakes can be applied through the service brake system but the brakes will not release. This means that the anti skid system has no effect in reducing braking pressure.
The light / dark skid marks may be from the brakes overheating and developing uneven braking forces as the brake rotor warps. Another possibility is the runway has differing friction coefficients / surface texture causing the skid to change.
If the skid marks were from the anti skid system and the pilot was using the toe brakes, I wonder if he was trying to stop but forgot to cut engine power
If a toe brake valve developed a leak, the brake for that side would apply. Left and right would have to leak at the same time in order for both brakes to apply so I don't think that this is the case.
If the Power Brake Valve developed an internal leak on the purple line control side, this would apply the brakes and allow the anti skid to operate. The real question is, for this particular PBV component, is there an overlap between L and R systems?
@@amytaylor8910 Why do you have a mask on in your avatar?..Were you in very large group of people, who were breathing?
Sounds like the Cessna needs a latch and a spring on the PB, where setting the brake latches it against a spring--and when you release the brake, the spring insures that it releases completely.
Very informative. Like with our ARFF Rescue vehicles, we can not move the vehicle if the parking brake is on. I think they should do that with these type of aircrafts, or have a loud beep in the cab when the parking brake is on so that the pilot will have no way of forgetting. These types of crashes should never happen. Thanks for this review.
I think the parking brakes were partially applied but not enough so to be noticed on the initial part of the takeoff roll. As the brake rotors heated up, probably red hot, they locked the mains. Also possible the pilot not flying, realized a s!ow acceleration hit the toe brakes and the parking brake va!ve, being shown as a check va!ve, locked the mains.
In the Falcon 7X we note the expected acceleration and the displayed acceleration displayed rather than an indicated airspeed check. Normally the expectation is around .40g + at light weights down to the .20 range at very heavy weights and high/hot conditions. A significant deviation is cause for rejection.
The parking brake position is monitored on most business jets. Perhaps because the Citation was certified so long ago it was not a requirement at that time.
This is what I was thinking.... I did delivery on this type model 99-2008 @ Cessna/Wichita. Lots of flights & taxi runs as a mechanic. I never had any forgot moments like this...
Nice to see that you follow up accidents and not only go for.the news as everybody else do. Thanks
Great analysis. Put check parking brake on the list yourself, don’t wait for Cessna which will be looking to CYA before changing anything.
Excellent as usual
Please cover the crashes at Arkenstol as there seems to be zero coverage of the accidents and a heck of a lot of speculation and verbosity concerning the entire contest. It would be nice to see the truth.
One factor that I did not see mentioned in the comments here yesterday, which I only learned about late last night, reading the "Cessna Citation XLS - Power Brake and Anti Skid System", is that the anti-skid system only operates when the speed is above 59 knots.
another fantastic explanation for pilots and non-pilots alike of what exactly went wrong, causing this tragic accident by Juan....thank you sir
I have been flying the 560 XL and XLS for 16 years now. Even with the parking brake set after starting the engines it sometimes will roll on you if you’re not careful.
The parking brake on these aircraft use a valve that traps fluid/pressure in the line and at the wheels. There's check valves that allow pressure to be INCREASED by pressing the pedals while the parking brake is set but doesn't allow fluid to return the other direction. There's a few ways you can get "partial" braking with this system. One is if you are not pressing the toe brakes hard when you activate the parking brake since whatever pressure is at the wheel is what is maintained. Second is if you set the parking brake when the brakes are hot as they cool the hydraulic fluid contracts and releases the brake pressure at the wheels. It only takes a VERY slight contraction of the fluid to cause a SIGNIFICANT drop in the trapped brake pressure.
Thank you for your fast updates on all these plane crashes.
Great job Juan. Great analysis that should help save lives.
Thanks!
Thanks Craig!
Juan you mentioned that if you have a second pilot then have him holler at you if you're rolling when writing down a clearance... he really is the one who should be writing the clearance but I get the point that in a single pilot type aircraft, a second pilot may be more of a request or tag along rather than a structured operation. I've been such a second pilot in small charter ops at the start of my career. And yes Cessna should look at this system inclusion in the Config Warning. We had this in the Lear as far as I recall, and every aircraft I've flown since.
Hello there👋👋,how are you doing today?hope you’re having a wonderful day?GOD BLESS YOU!!💕
Not saying it happened here Juan, but I’ve seen on some automotive brake hoses where they deteriorate inside and form a sort of check valve and not let pressurized fluid back thru quickly when the pedal is released. This usually shows itself as a caliper that won’t apply or one that drags and wears out that pad prematurely.
I've seen this loads of times in the classic car world. The inner hose collapses and when the brake pedal is depressed the fluid pressure opens up the collapsed inner hose and the subsequent release of pressure allows the inner to "relax" into it's deformed or flattened state thus not allowing the brake fluid to return to the braking system or master cylinder.
Visual checks of the brake hoses don't catch this failure condition, it's usually only caught if you have an assistant operate the brakes whilst you apply your fingers to the affected hose. Due to the structural integrity of the hose being compromised the hose will often swell more than is acceptable and then remain hard as it is pressurised with hydraulic fluid. Further confirmation can be obtained by the fact that the wheel will not turn and when the bleed valve is released whilst you keep your fingers on the brake hose, the pressure under your fingers will disappear and the wheel will again be able to rotate.
Decent aviation-grade hydraulic hoses should not allow this to happen. That is why I use them to replace the brake hoses on every vehicle I've ever owned, with the advantage that they will last until long after the frame rots out and the cylinder bores are oval.
Happened to our van recently. Old hoses were "mungy". Replaced.
I ‘ll be adding both parking brake and rotation/rejected take-off position to my C172 take-off checklist from now on! Thanks Juan. Cheers.
My 2012 Civic will warn me if I go above 5 mph with the parking break on. I'm pretty sure this car costs less than maybe 2 years of required maintenance on a Citation.
LOL...try two months worth of maintenance...
I have more experience on the bombardier jets, but a Lear 31,45 and 60 WILL NOT hold the brakes if you apply full power. Your going for a ride unless your using big chalks.
Chocks.
Helicopter vs. plane crash happened at Fulton County airport in Atlanta GA… both were doing training on parallel runways too.
It looks like the Chandler, Arizona crashes were flight school crashes, for sure the helicopter which listed both the flight instructor and student as casualties. Your graphics are always exceptional Juan.
JUAN, HI as I recalled there were. DISTINCT RIGHT BRAKES SKID MARKS, THEN ACROSS THE GRASS, initially I said it looks as they were ABORTING but continued on as those skid marks showed up ,,,,,
RIP & Condolances to their families 🇺🇸🇺🇸🇺🇸🇺🇸
They never throttled back. During the first 1/2 or so of the takeoff run, the weight of the plane was on the wheels and that kept the wheels rotating. As the plane accelerated, it got lighter until there was no longer enough weight on the tires to make them rotate and they began to slide..
As usual Juan, you ask and bring forth questions that need to be answered.
Juan, MY BLOOD BOILED at 18.20 when you read out loud that Cessna, ALREADY HAVE a
'NO TAKEOFF'
park brake on warning system available for this model, but was not installed.
picnic
The four main tires and brakes all brake engaged via. one parking brake handle. Pretty easy to see how brake fluid pressure could bleed-off 3 of the wheel-brake assemblies and once the aircraft started rolling heat expanded the friction pads. Choking off the take-off roll speed.
Great analysis Juan.
Great report Juan! Thank you!
Thank you for this balanced and concise assessment.
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Lots of knowledgeable folks called that one when it first happened.
If they supply a warning on the European models, it should be applied across the whole line.
Just thought I’d mention as an A/C engineer here in the UK back in the 1970’s. I found that sometimes when releasing the parking brake (on a different make of US aircraft) it would hang up. Meaning that pushing or releasing the control knob didn’t necessarily release the brake. The pressure in the system was not allowing the valve to release, or release properly. As an engineering practice, re apply brake pressure before releasing the parking brake. This should make sure the brakes are off and the parking brake system is off. Some aircraft had quite a basic and rudimentary system, just a push pull wire.
You do something like the acceleration check with a 150 at airports over 6000msl on warm days. It isn't exactly the same, and the margins aren't as critical, but learning in low HP at high altitude .... It's a smaller dog but it has a similar bite.
Cessna will be hesitant to mention anything unless the NTSB does more than just mention the position of the Parking Brake in a report. It will have to directly attribute the cause related to Parking brakes or if Cessna changes anything it is an admission of liability.
So detailed analysis of a case. Very helpful for newcomer pilots. I will triple check brakes…
Im going to take the acceleration check into consideration, “two good engines” & waiting for V1 doesn’t catch this fault. Point 3 is a possibility since this happened to this type twice or maybe more? Anyone else out there have this happen in some way?
I’m guessing 120 is enough to fly an Excel with a normal rotation but this was anything but. Sounds like an accelerated stall, he had to pull too hard to unstick (with that nose down pitching from the brakes) and then it pitched up hard after lift off. I don’t have the numbers on an Excel but online saw typical approach Vref of 106.
Hi Juan - if those wheels weren't locked solid by the parking brake, then as that aircraft picked up speed, those brakes would got hot and will apply more brake power as heat comes into the system. The heat would cause some fluid expansion, and rotor expansion. Surprising the antilock continued to work though! This is a common issue on motorcycles rear brakes when not serviced properly and too full on fluid.
Don't know if it has been mentioned. The Dassault Falcon series (at least 50/900) had a G acceleration meter in an upper corner of the PFD. The takeoff numbers included this minimum acceleration number. It is the only series of civil aircraft I have seen with this but I thought it was wonderful. A quick glance at 80 Kts told you if the airplane was performing as advertised. Left you in a relatively low speed regime for a reject if you weren't accelerating properly.
Anyhow, Excellent breakdown Juan!
Man.. so sad to hear about that midair in Chandler.. I was just thinking how nice it was that I hadn’t heard from Juan in awhile.. condolences to the family.