While acting as chairman of Hiller in the mid 80’s we lost our senior test pilot while testing a new series of “hot and high” blades. Anytime you “unload” the blades of a teetering rotor system they become extremely unstable. This is a characteristic that was well documented during the Vietnam war. Unloading is when you subject the blades to near zero “g” or a negative “g” force. Depending on atmospheric conditions they can be subjected to other influences such as wind gusts or turbulence that can cause unwanted deflection when approaching an “unloaded” condition. A rotor system with a larger mass will tend to increase the dampening the rotor thus lighter blade systems can be more unpredictable. Further, Dampening can affect an oscillation that can occur when the blade reaches the end stop and the blades flex causes an increased deflection and subsequent oscillation. The blades will deflect or oscillate between end stops with an increase the rate of oscillation and an increase in deflection of the blades until they 1) snap the mast, 2) deflect the blade sufficiently to come in contact with the boom, or 3) cause one of the blades to separate causing s severe inbalance of the rotor system which in turn will cause total destruction due to centrifical force.. A stable teetering rotor system most be kept fully loaded and avoid any violent manoeuvres close to the edges of the performance envelope. This is one of the reasons the Hugh’s 500 became popular with its fixed rotor system during the war as it allowed the aircraft to be far more manoeuvre able and forgiving. That test pilot was one of the most senior test pilots at the time having just certified the Apachie and Hugh’s Notar. It was in an Fh100 turbine.
I did aerospace engineering, have fixed wing PPL and had to read this twice. I agree with KAM this is first class information. I also found this link on the Vuichard Method to recover from a vortex ring. Its pretty good at showing what the Vortex Ring is. I didn't quite get the opposite rudder until I simulated the force directions in a swivel chair. It then made perfect sense. If you think the link isn't useful or appropriate let me know and I'll remove it. ua-cam.com/video/HjeRSDsy-nE/v-deo.html
I know personally that you can cut the tail off an MD-600 NOTAR if you try. See MIA00FA102 (hint Florida man says “watch this!”). It flew over my shop every morning eastbound. Such a magnificent machine. I’ve never seen a helicopter hold station like that one. Then one day it was gone.
Wow! God bless him and all the others that afforded us the “tombstone” technology. It amazes me that things that can seem so simple are so truly complicated. Before the Osprey accidents, I had never heard or the “vortex ring” effects… holy cow, like there isn’t enough to think about just operating in a three dimensional environment…
So true! I was a student pilot At Palomar airport flying Flying a new R22 serial 38, I was taken under that test pilots wing and watched him do the first autorotation in the Hugh's NOTAR prototype, a converted OH6. He once told me if I fooled with that 2 bladed R22 system it would kill me, I still think about all those test pilots I had lunch with "especially him" who pushed new untested machines to the limit for many future helicopter pilots safety. Thanks to his care, and no BS advice, I'm still alive and flying helicopters 41 years later, Thank you Charley! R.I.P. Charles Hench, Chief test pilot, Hugh's helicopter 1979-1981
I knew the CFI when she was a Forest Service helitack firefighter. Great person that always was smiling and a good person to be around. She will be missed. RIP Lorax.
I met and briefly spoke to this CFI at HAI back in February. Ms Trout made a remarkable impression on me as being very outgoing and cheerful, but also very bright and professional. She was extremely passionate about flying and had a very promising career ahead of her. This was an incredibly tragic loss.
I recently completed my helicopter private license and have about 450 hrs fixed wing. There is a stark difference in training between fixed and rotary wing with a much greater emphasis on emergency training and avoiding states/actions that will kill you. About the only advantage a fixed wing license gives you is in radio comms and navigation (but even that’s not quite the same as you cannot ever take your right hand off the cyclic, so folding charts etc is all one-handed and maintaining altitude tolerance whilst distracted is much more challenging than fixed wing). There are some actions in responding to abnormal states that require an ‘opposite’ action compared to fixed wing flying; an engine failure in fixed wing during cruise requires converting excess speed to altitude and getting to best glide thus BACK with your left hand on yoke, to enter auto with R44 (less than 2 sec window to do so otherwise unrecoverable fall to the ground) you push DOWN on collective with left hand and gentle slight aft on cyclic. It took a while to get the brain tuned properly into that. Also low g events require very gently delicate response compared to what you may instinctively do in a fixed wing aircraft otherwise mast bump / tail boom strike. The instructor ALWAYS had his hand touching or adjacent to cyclic and collective during any turbulence even right at the end of the training as there are absolutely no do-overs in a helicopter. I found the transition fascinating and it’s much more challenging to learn to fly safely than I would have imagined. Despite picking up the basic flying skills pretty quickly re manoeuvering, hovering, power management etc it took much longer to get to solo than the case for fixed wing as you have to be competent in all emergencies and abnormal conditions. It was about 25 hrs to solo compared to 8 fixed wing. I had to reliably demonstrate autorotation entry and touchdowns, avoidance of mast bumping, avoidance of tail boom strike, avoidance of vortex ring state, loss of tail rotor effectiveness, tail rotor drive failure, jammed pedals, engine failure in hover and engine failure during takeoff/transition. Once you have all that nailed you get to do your first solo circuit!
You hit the proverbial nail on the head with your post. You should come fly in Phoenix AZ if you haven't already. On top of everything you wrote about you can enjoy the FAA designated complex airspace along with the lovely flying weather. The daily forecast is usually, sunny with a slight chance of a runway incursion and a possibility of a mid-air collision as the day warms up to 120 degrees. And always remember what was always posted in every flight school I've been in for Rotorcraft/Helicopter "It's not a matter of...... if you crash, but when" considering helicopters are the best aviation definition of an unstable aircraft. Safe travels to you, that like myself are the few that can do what we do. Alex, Scottsdale AZ - Commercially Licensed Rotorcraft/Helicopter, Instrument Rating, with a Fixed Wing add on. (Not Currently current on any for reasons associated with this video, but not in relation to said video and or anyone directly involved, or connected to this tragic event). Just decided to take a break.
@@alexdelarge8749 one day sometime soonish perhaps... I'm from Perth in Western Australia and fly from YPJT. Frequent traveller to the US pre-Covid and looking to return soon. Keen to explore a little in both rotary and fixed-wing - recently bought an M5-235C to build some further skills. Somewhat unusually I did my ab-initio fixed-wing training in a 300hp Stearman...always up for a bit of a challenge. I have a few videos on my channel of fun in the Stearman around Perth 🙂
@@Chris-bg8mk yes we had to do touchdown autos. Also not required for PPL(H) here in Australia, but the school I went to took a slightly different approach to most as they wanted to produce pilots properly able to manage autos to the ground. The Chief Flying Instructor has a few thousand hours of heli-mustering experience where a lot of time is spend on or inside the edge of the dead man’s curve so he was really big on safely getting onto the ground in an emergency and being pretty sharp on managing autos.
@@Chris-bg8mk Some helicopter flight schools do teach touchdown autorotations. Accident chances do increase, but sometimes those last few feet make all the difference. In 1981 when I got my Commercial Helicopter rating the school I attended taught touchdown autos in their Hughes 300’s, and while difficult to master, really brought up one’s confidence level. Came in handy a few years later when I had an engine failure in a Hughes 500D. Things happened quickly, but the training kicked in and I autorotated into a farm field and landed safely. Engine was toast, but not a scratch on the 500. Later when I started flying Bell helicopters I attended their flight academy in Texas every year, and we did ALL the emergency maneuvers to the ground. The instructors were seasoned pilots, many of them Vietnam veterans, and it was fun to see them do things in a helicopter I didn’t think you could do. By the way, the Army used to do touchdown autorotations, but they found that they were damaging so many of them that they went to doing power recovery’s. 😏
There are a handful of incredible channels that talk about flying. Each of which give another vantage point. You give a good understanding of the technical nitty gritty.
Juan is so good at explaining these cases in easy to understand terminology. Thank goodness because I need the Aerodynamics for Dummies version. My heart breaks for the families and friends suffering from this tragedy! RIP🚁
It’s called low-G mast bumping. It can happen to any semi-rigid rotor system, including Army UH-1. Army and Robinson Helicopter have special training for avoidance.
When we fly game surveys here in southTexas in R44 I notice they have the placard “NO LOW G PUSHOVER” When I asked the pilot about it he explained it technically and this just reiterated your lesson at the end. Fly safe!
As a former helicopter pilot now fixed wing. You are correct. This maneuver requires only two steps to get out of. 1. Lower collective and 2. Gentle forward on the cyclic. You want to get airspeed then climb out. All movements should be the width of a dime.
Unfortunately… once the rotor is unloaded, movement of the cyclic will usually cut off the tail and sent the main rotor right into the cabin where the lilt is sitting. Never get light in the but.
When Robinson helicopters arrived on the scene the 2-seat R-22 (which has the same rotor type as the R-44) appeared to be a good trainer. Flight schools bought the R-22 for use as primary trainers. This resulted in several fatal accidents where student pilots would unload the rotor with incorrect cyclic inputs, which caused rotor blades to strike the fuselage or the tail boom. There are a couple of special regs (SFARs) that were created to address this
I really like the way you drill into the core problem: Knowledge Transfer. I've worked in industrial design and manufacturing since the '70's and have kept up with technological changes to the industry. Passing on what I know to a diminishing number of people is creating a situation where knowledge will die and be replaced by automation. Which relies on the software writer's knowledge.
SFAR 73 to Part 91 is required reading to be able to learn to fly in a Robinson by law. It covers i) energy management ii) mast bumping iii) Low Rotor RPM (blade stall), iv) Low G hazards v) Rotor RPM decay among other requirements. Of course all of these are l possible in any two bladed rotor system. Huey’s included.
Thank you for the explanation, Juan. I am an R22 student and both my instructor and I were talking about this. His take was they essentially had an SWP (settling with power) either accidentally or as a training exercise and exactly as you said, there had to have been bad inputs, at a high rate of speed followed by another counter-input abruptly that caused the rotors to strike the tail boom and sever it. I have practiced SWP to the extent that is allowed with one of my instructors at 3000 ft and I remember just how scary it was to drop so fast (the feeling of falling and gravity sucking you in) and how strong you needed to be mentally to avoid doing what your brain wants to do which is to pull more collective and aft cyclic but instead you need to smoothly apply very little cyclic forward and let the rotor blades grab fresh air and magically the feeling of falling stops and your rate of descent slows down. The fact that this new CFI was training a fixed wing pilot makes me think that the student pilot reacted based on their fixed wing training and the instructor didn't have the power or time to react appropriately causing this catastrophe but we will know whenever the report comes out I hope. Tragic loss nonetheless, I feel deeply sorry for all the families involved.
The procedure is to reduce power and initiate directional flight. The hardest thing to do is to reduce power. The directional flight can be in any direction. I flew helicopters for 26 years in the Army and forward flight is not always possible, hence the procedure of establishing directional flight. I think we should all stop speculating and wait on the accident investigation. It could be myriad of things that brought this aircraft down. It’s unfortunate there are not available civilian simulators for students to learn emergency procedures. We’re very fortunate in the military that we have the opportunity to practice every emergency procedure imaginable that you can’t practice in the aircraft. Prayers go out to the families.
JUAN,Hello, gee sad situation, sad to loose 2 people,I had only been in the 4 placeROBINSON ONCE, BUT HAD MANY FLIGHTS IN LARGE SICORSKY & an older BOEING VERTOL, , I had NOT yet heard of this one ,so thanks for the update, 🇺🇸🇺🇸🇺🇸🇺🇸
I flew off my Navy ship on the ships helicopter over part of the Mediterranean Sea to Lisbon, Portugal when getting out of the Navy in 1981. The flight was flawless and smooth but I was a nervous wreck the whole time as I always am when I had to fly somewhere. Imagine the guy that's leading the Indy 500 with ten laps to go. You're listening for any noise or vibration coming from that machine until you are safely in victory lane. That was me whenever I had to fly.
My wife is a teacher in Garland, right next to Rowlett. That helicopter flew over her school and recess playground when they were outside. The accident was two minutes flying from the school.
ATP rated helicopter pilot and CFI/CFII helo - this has all the classic indications of mast bumping - concur with the discussion that JB is leading here. Also the Robinson R44 is covered by a SFAR - the requirments of which must be fulfilled to act as PIC on this model. Keep up the great work JB.
I took a Commercial Rotary Wing Add-on course flying Bell 47s with U.S. Army combat experienced instructors. An important lesson was to not move the cyclic control more space than the diameter of a half dollar, unless performing a quick stop. Even then it was a gradual effort. I completed the five week course in three. My instructors, especially Bob Seales, we're well experienced and dedicated to safe practices.
Way back in the day when I was training in a 22 there is a situation where you can do that, high altitude hover stick forward hard stick back. A rookie after me took out that trainer in Austin years ago.
You're so good at explaining mechanics and aerodynamic forces. Also situations which may help create less margin for error. Rest in Peace trainee pilot and trainer.. Let's learn from this. Especially in a time of pilot need.
I learned about this phenomena called mast bump in DCS (flight sim) in the Huey as I kept watching my main rotor keep sailing off in the distance without me, lol. Millennials know and invented everything, didn't you know that Juan?
Someone posted a really cool Army video in the VTOLVR that explains these types of things. I think I learned more about helicopters in that one video than from anywhere else
With what little I know about rotary wing aircraft, mast bumping is to be absolutely avoided. Keep a positive G load on the main rotor at all times. Avoid negative G pushovers, etc. I have real world fixed wing experience and Jet Ranger 206 simulator experience. Yes, smooth and minimal inputs on the controls of a helicopter.
You should qualify your “blanket statement “ about keeping positive g’s and avoiding pushovers in helicopters. 100% depends on following POH and manufactures operating limits. Many, many helicopters can and routinely do low g maneuvers, the R-44 and B 206 are not in that category. As a military instructor pilot in the AH-64 for 16 years we taught and pilots had to perform a High/Low G maneuver…… pulling into a 2 G pull up followed by a .5G push over. Understand not all helicopters are subject to a low G restriction.
As a fixed wing pilot, a few years ago, I was at a local air show and a few med and military copters were on static display there. A crew member “explained” to me that helos don’t fly - they beat the air into submission.
As a commercial fixed wing pilot about to start my rotary training in Robinson helicopters, this phenomenon is extremely interesting. Thanks for the info Juan! Hope you're enjoying NYC. I've never been... yet! Hopefully someday I'm filming some awesome stuff from a helicopter over NYC :D
Anyone who has flown a Robinson, like me knows that the first thing a good instructor tells you to never do in a Robinson is to get into a negative G situation, mast bumping is what its called and its mentioned all over the operating handbook. The blades can literally wrap around the cabin and will take off the tail boom, no recovery from that.
Legally you have to be instructed on low G, mast bumping, energy mgmt, low rpm, and rpm decay before manipulating the controls of an r44 or r22 based on SFAR 73.
Memo to self: never consider getting climbing into a Robinson, because I make every mistake in the book at least once, and a few new never heard of mistakes too.
Very tragic event…my wife and I knew the CFI and were actually scheduled to fly Friday afternoon just after the accident happened at SKY. School is grounded as of now while FAA and NTSB are there investigating.
Since 1982, 600 people have died in Robinson helicopter crashes. But Robinson continues to mass-produce nonetheless, and it does so without having to make many changes to its flawed helicopters.
Yeah, It would likely be the worst trainer on the market...considering fatalities and their unwillingness to strengthen the blades...I always cringe when I see another chop its own tail boom off and the occupants die another grizzly death. When will they learn.
The way the metal in the tail section is splayed outward in all directions around the break point it makes me wonder if a coupling or something failed in the tail rotor driveshaft which then ripped up and separated the tail. There appears to be some sort of coupling on the shaft at this point in the tail section held by the NTSB investigator. Also there is no noticable damage to the rotor blades until it rolls inverted then as soon as the blades hit the tail they start to come apart.
I believe the tail rotor had already been severed by the time we see the helicopter in view on the video. Then because of the violent rotation the blades severed of more of the tail boom. Go back and look at the first couple seconds of the video and you can see that the rotor assembly is not visible. I believe that's because it is above the camera frame tumbling down above the helicopter.
Yes the aircraft might have been “operated outside of it’s design limits” but Robinson’s have a very high incidence of this very problem even when compared to other training helicopters. They also have very light blades and this means low rotor inertia causing still other problems. I have lost two friends (both were careful and fairly experienced pilots) flying Robinsons so I am pretty biased. Robinson’s are inexpensive compared to other Helicopter and that is why they are popular trainers. They are not well suited to this role.
Low inertia blades also give you faster RPM recovery. Like any helicopter if you dont hit the spinny things on objects and manage your RRPM blade inertia is irrelevant.
One flight school lost a pilot and a trainee and they went to Frank Robinson complaining about it trying to sue him. He told him to kick rocks he never designed the helicopter to be a trainer
and how many accidents. one hundred? 43 just in a short span of time years ago. some body has deep connections to government official to allow this garbage to continue being manufactured.
Ironic that it's attractive as a trainer because it's cheap but not attractive as a trainer because it's unforgiving to inexperienced pilots or pilots not specifically experienced with this helicopter. Yet, a flight school can't buy a better, more expensive trainer because people will go to the cheapest school...because you get what you pay for doesn't cross their mind or their desire to fly is bigger than their budget to fly.
@@Texas240 cheapest to operate. best fuel burn. less complicated. the only thing that was ever super dangerous with the robinsons was the fuel tanks. a lot of them didnt have puncture resistant bladders. chances are the trainee did something wrong. they mentioned he was an airplane pilot working on his helicopter rating. my guess is he did a push over unloading the rotor and it hit the tail cone. but that picture of the tail doesnt look like it was sliced. looks like something blew it up from the inside out
He explained mast bumping which doesn’t have anything to do with this crash. The aircraft crashed because of a boom strike as a result of a low-G condition. Helicopters are designed to hang under the main rotor with the rotor blades flexing up. In a low-G situation the helicopter’s momentum is forced up into the rotor system causing the rotor blades to flex down where they can contact the tail boom.
@@nocalsteve Besides coning, I’ve never heard of blades simply flexing in the wrong direction, and I taught helicopters for a couple years. Low G/mast bumping are taught together. The whole idea is unloading the rotor disc which allows it move independently from the rest of the system. At that point, it’s extremely unstable and any large control input could cause the blades to flap far enough to exceed the mechanical stops and contact the mast and/or the boom.
@@Hamchuck112 Am also a Rotorcraft CFII and that's exactly right. Mast bumping is taught in association with severing the tail as one, the other, or both are very likely should a pilot enter a low G state and make any abrupt cyclic control inputs. Especially since the low G condition is usually accompanied by a rapid right rolling action because the main rotor and fuselage are working relatively independently and the tail rotor thrust causes the helicopter to roll about the longitudinal axis. Thus the untrained pilot's reaction would be to immediately input left cyclic to counter the roll, but because the main rotor is fairly unloaded, it can flex down below the droop stops and contact the boom and/or mast. Pretty catastrophic results regardless of if only one or the other happens. Definitely tragic and my heart goes out to these pilots' families.
Thanks Juan. Even though you aren’t a chopper pilot you get the info as fact from the proper sources and relay it to us. Tragic incident and condolences to all involved.
In the late 80’s we had a CH 136 Kiowa return to base with a chunk missing out of the tail rotor drive shaft cover. Pilot had mast bumped while low level training, flying over trees and dropping down on to fields. Replaced the trds cover, seat covers and air freshener, return to service.
These are two different things, your guy had a boom strike, not a mast bump. A mast bump damages the main rotor shaft, a boom strike is when a main rotor blade hits the tail boom.
Thank you Juan. I know I’m not the only one to have asked you to cover this, but I specifically wanted to hear your take on it, because even your educated guess is far more likely to be accurate, than many others. Your commentary is also more likely to be balanced without making conjecture. Thanks for the explanation of the rotor balance and mast bump concept. Of course we will have to wait for the official answers, but one total guess of mine is that a rapid control input was introduced, causing the rotor to flex so much that it took the tail boom off. One video clip of the incident shows the R44, already without the tail, and managed to make a hover, and looked for a second like it could autorotate, but lost it, rolled sideways, and the mains folded. Very tragic, I’m sorry for their loved ones losses.
@@zzodr it was a probable cause. We will most likely never know exactly what happened to cut the tail off that R44. It could have been the tail rotor drive linkage coming apart, it could have been exaggerated rapid control input, it could have been clear air wind shear, it could have been a combination of those things, all of which are probable causes, not for sure the cause, but probable cause. Furthermore if it were a factor of a newly certified rotorcraft instructor combined with a new to rotorcraft student pilot, then maybe, MAYBE a possible recommendation might be that newly certified rotorcraft instructors do their first 24 hours of “flight instruction”, re-certifying pilots renewing their existing licenses, and requiring new student pilots, new to rotorcraft, to have instructors who are certified to train students who are new to rotorcraft. Or maybe there’s no reasonable recommendation to be made, since there’s no way to know “for sure” what caused the tail rotor assembly to separate from that R44.
Of my 2000+ hours in helicopters, .5 hours was in an R22. I booked an hour, but I was so terrified after the first autorotation, i told the instructor that I was done. Kids like them because they're fast. The R22 and R44 are giving the industry a bad reputation.
In the R22 and R44 mast bumping wouldn't necessarily cause a tail boom strike. It will, however cut notches in the main rotor shaft that can cause the shaft to fail, turning the machine into a ballistic brick. (One of the helicopters at the school where I trained came extremely close to main rotor shaft failure while an instructor was demonstrating a low-g maneuver to a prospective student and encountered mast bumping. The prospect decided his life was too dear and walked away without taking his first lesson.) Low rotor RPM is a more likely cause of a tail rotor strike. These aircraft have low-inertia rotor systems, so the pilot needs to stay on top of rotor RPM. Typically, correction must be made within two seconds or the RPM can decay to the point that it cannot be recovered, even at full power, and the helicopter gets a case of "blew blades". I hold a commercial rating in rotorcraft and my primary training was in the Robinson R22.
You seem knowledgeable enough. Why is a helicopter model particularly vulnerable to aggressive inputs, and is hard to auto rotate, widely used as a trainer? Why not something more forgiving.
@@spider0804 - I was told that the Robinson R22/R44 behave more like many jet-powered helicopters, so if a student can master the R22, the transition to more complex types would be easier. This was in the days before fly-by-wire became commonplace, but now with computers actually flying aircraft based on control input by the pilot, much can be done to alter the "feel" of the aircraft using software.
As a Rotorcraft CFII, I can assure you that every book I've ever read indeed mentions that a low-G power pushover can absolutely end in a severed tail boom. It could be an and/or situation, but regardless, if either of those fails it can be catastrophic. That said you CAN make a landing without a tailrotor by initiating an autorotation, as that removes engine torque. Not completely sure as to how the helicopter would maneuver if it lost both the tail rotor AND the horizontal/vertical stabilizer. Also, any helicopter instructor that actually "demonstrates" a low-G situation maneuver in the air by actually entering into a low-g condition shouldn't be instructing. Someone's going to get killed, and it sounded like he came close with that potential student. That student was right to walk away. Every text on the issue makes it clear that even experienced test pilots have been killed investigating the low-G condition and that no pilot should ever attempt to actually induce low-G in a Robinson or any other semi-rigid rotor system.
Knowledge is easy to pass on, Hard won experience and the intuition that comes from that is some what harder to pass on and usually goes with us when we pass on.
Day 1 in my helicopter training was to talk about Low-G and how dangerous it is. If they were practicing high altitude hovering and descending with power if you move the cyclic forward too fast this is what can happen. Really sad. Condolences to the families.
As a former part-time heli pilot, your analysis is spot on. Robbies are very fidgety and especially an R-22. I realize this was an R-44, but very similar designs. Cheers and RIP to the two pilots. Sad scenario.
Years ago I was talking to a helicopter pilot who flew in the military. He said if you try to pick up a stationary helicopter by lifting at the ends of the rotor blades, the blades will snap in half. It's the centripetal force of the spinning rotor that gives the blades the strength to lift the helicopter. I have never wanted to fly in a helicopter since.
No it’s CENTRIFUGAL force (not centripetal) that keeps the rotor blades of a helicopter rigid while spinning from the axis of rotation, thus giving the entire rotor disk the ability to produce lift as a whole.
Think of it like this. Take a piece of string about two feet long, tie a one pound weight in the center. Now, place a finger under each side of the string about six inches out from the weight and raise your hands. The string will slip off your fingers but, the weight will lift. Now, grab each end of the string and pull outward with about ten pounds of force and raise your hands. The string is now ridged and will lift the weight. The centrifugal force of the spinning helicopter blades make them ridged enough to lift the helicopter.
In your example the weight is entirely on the ends, where in reality the weight is distributed through the blade, and entirely on the shaft. If you pick a 747 up by the wing tips it will snap too... Your example is misleading.
Good explanation Juan. Here in New Zealand we have a disproportionately high number of these tail boom accidents on R44 and R22 helicopters. We’ve even had Robinson send representatives out to address the issue here. Much of it has been put down to flying these in overly turbulent , mountain conditions which puts the helicopter outside of its design envelope. Unfortunately, the result of a tail boom strike, is also a resulting cabin strike at the other end for the helicopter which results it fatal injuries to the occupants.
In the Navy back in '73 I did time in line division in our SH2D Seasprite squadron. While getting trained up in the vagaries of ground directing helos, and specifically the SH2D, I was introduced to the "droop stops". It was explained that the droop stops were weighted, pivoting, locking levers on the rotor hub that, when the rotor spun up to a minimum RPM, would pivot, unlocking the rotor blades so they could free float in flight. It was further explained that one of my primary duties when directing was monitoring the transition of the stops from locked to unlocked on spin up, and unlocked to locked on spin down, signaling the pilot on their position when transitions occurred. The price of allowing the rotor RPM to spin down without all of the droop stops engaged was a boom strike. Naturally I asked, "What do I do if the stops don't lock in?" The answer was to signal the pilot to pick up his RPM again, run to the line shack and get the red broom handle standing in the corner behind the door, and go back out and give the offending stop a "whack" when it came by. I resolved at that time that if I ever had a stuck droop stop that I would run and get someone from the AF/PP shop instead. Thankfully, I never did.
I worked on the NZ Navy SH-2G(NZ)s. We were also taught to direct the pilot to increase RRPM if a droop stop failed. If a stop didn't engage on the second RRPM decrease, the solution was to get a fire truck out to hit the stop with high pressure water from the truck's foam cannon. If that failed, the next step was to strap a bed mattress to the tai, hoping that the blade would bounce off it as it drooped when it passed over the tail boom.
I still remember the Droop Stops in/out marshalling signal from my days in the Royal Navy, Fleet Air Arm, last century...... I never used it though as the Rotary Aircraft type I worked on had an unarticulated Main Rotor Head.
Called out droops in/out when I was a crew chief on H3's. Happened to me a handful of times. Just spun up and tried again. We used light lubricating fluid on the droop hinges. Very rare occurrence of a droop refusing to come in.
That's exactly how I understand how the robinson rotor system works. Frank Robinson came to our country and we explained how we use his helicopters and he was horrified
Mast-bumping was a big problem with Hueys during the war in Viet Nam. There is an Army video on UA-cam which addresses the need to keep the rotor loaded during terrain-following flight.
I bop around for work a lot, mostly 185s and Beavers, but increasingly in R44s seems like every place that is allowed to use them is getting one. And now I am scared. I don't like the haughty cowboy attitude of some of the pilots, but don't know enough about flying in order to determine if they are good(safe) pilots or not. You have made me want to turn down rides, but i don't really have much of a choice without changing not just jobs, but careers. Damn. Thanks for the great info, hope you aren't covering me some day.
If you ever saw what the guys in South TX do while herding cows (and sometimes deer) it would blow your mind. I don't blame you for being nervous one bit.
Interesting comment Rhane. I last flew with my father when he worked for Hughes in the 1970's. I was never scared because I was a kid (7-11). I haven't had the opportunity to fly in a helicopter since, and now at 56 I'm scared enough to avoid them but will jump at any opportunity to fly in any single or multi engine fixed wing aircraft. That being said, is there a tactfully correct way Rhane Pfeiffer can screen the pilots (avoid the cowboys) he must fly with without offending them or losing his job (career).
Control smoothness is much more important in helicopters and negative gs are no nos. We Army helicopter pilots developed a bad habit of fast approaches in Vietnam to reduce the enemies time to target us going into hot LZs. Absolutely not necessary in normal conditions. The big safety advantage of helicopter is that we can approach slow, shaking slow, and see every wire and every obstruction in the LZ clearly. Watch the rate of closure with the desired touchdown spot. Far back it appears to close at a brisk walk, same as in your auto coming to an intersection. Your helicopter pilot should decelerate on short final enough to keep that spot closing at what appears to be a brisk walk, just like when decelerate into an intersection with your auto. Fuss at him if the apparent rate of closure appears to speed up. Things appearing to speed up is scary in your auto. It is scary in an aircraft as well, especially the helicopter that can decelerate a bit more than the airplane. Just a note, the 185 and Beaver should decelerate as well. Yes, the apparent brisk walk rate of closure. The helicopter can get shaky slow and it will appear to be no apparent rate of closure at all.
A construction Company i worked for had a new Bell Jet Ranger and an experienced Vietnam pilot. My clients liked to fly over their projects and I had to accompany them. Hated every minute I was in the thing. Even more than when I was in the military and had to fly in them as an artillery forward observer. I’m a private pilot so flying doesn’t scare me but a seat in a helicopter does.
I could of miss-heard you, but when RPMR is low and loaded, the blades cone up. The phenomenon called settling with power or vortex which is based off the main rotor, LTE in the tail. Though vortex/lte can literally the same EP and avoidable. Move fwd and reduce power if able. SWP is harder to detect right away but LTE typically has warning signs and you can maneuver to get the wind in your favor. Fly low, draw fire.
Sorry to hear about this crash and your loss. Good review. I enjoy your flights with Pete and James in Ercoupe. Has there been an update on Tango and Juliet crash in Cessna 140 at Williams, AZ? Bill
Interesting fact, Frank Robinson never built or designed this Helicopter to be a training platform. It was meant as a commuter for a businessman similar to the Cessna 150 Commuter advertising campaign.
Most rotary wing aircraft masts are hollow; more like a pipe than a solid axle shaft. It only takes a small dent or deformation to jeopardize the structural load bearing capability of said mast. By way of demonstration, you can place a cinder block carefully atop an empty beer can and it will support the weight. Now, tap the side of the can with a metal ruler and see what happens; crunch! While the term used is mast bump-ing, in truth, it is more like mast bump. Smoothness on the controls and a loaded rotor head (no zero or negative G maneuvers) will reduce the likelihood of mast bump in a two-bladed underslung system.
I don't really know anything about this stuff I just wanted to understand in a nutshell what happened here and you hit the nail on the head quickly and efficiently. Thanks!
I did the helicopter add on after flying fixed wing for 20 years. ASMEL/COMMERCIAL/INSTRUMENT. I flew the Schweitzer 300C, which is a fine heli, and not hard to fly. A heli is fantastic fun. In my opinion, since I can drive a car with a clutch, and motorcycles with twist throttles, I did not find it difficult to learn the helicopter. Our young people now have missed out on the background we older folks have.
Well defined and described Juan. Have always wanted to transition over from fixed wing PPL to rotor wing endorsement. Some how time passed by faster than I was motivated to do so.
Same here. Funny thing is, I started flying helicopters before fixed wing. I flew some 20 hours in a Bell 47 and was instantly in love. But life happened, money became short, had give it a break. When I had the chance to start flying again, it had to be fixed wing (less than 1/2 of the cost in my region). So I became a pilot, fixed wing, but 30 years on, never lost the profound admiration for helicopters. My fix: started flying RC helicopters, which is the next best thing.
Robinson’s safety record is great…. If the PIC obeys the limitations of the aircraft. The problem is, people exceed the aircrafts limitations and break the rules as set for the safe operation of a Robbie. Plain and simple.
Don't listen to the know it alls and arm chair pilots Juan. Your explanation was spot on. I started my training in 1981 when the R22 was just being introduced in Canada. I did the 60/40 commercial, the 40 on a Bell 206. I found the R22 to be a good trainer. One thing that was consistently drilled into us was the low rotor inertia and the importance of maintaining proper rotor rpm. When doing simulated engine failures/autos, getting the collective down quickly was paramount. I can't recall any mention of mast bumping during training, even on the 206. We had around 12 students and several Robinsons. We had one accident, a dynamic roll over on a snow covered lake. No other accidents in the 6 months I was there and we flew six days a week. The R22 was demanding and unforgiving of mishandling but I liked it. Transitioning to the 206 was a dream and it was more forgiving. Autorotations were a non event, even full ons. Thanks for your efforts and stay safe.
At age 68 I decided to add a helicopter rating to my CSEL, CSES and CG ratings. I did one lesson in an R22 and went home, googled it and saw the accident rates in the Robbies. The rest of my lessons were in a Guimbal Cabri G2. I had no intent of instructing or flying tours, just wanted to learn to fly a helicopter which I accomplished. Frank Robinson himself said the Robinson was never meant to be a training helicopter yet it is the most used for instruction in the USA and elsewhere.,
from what i have heard and read. train over deep enough water to save your life. that is what we did when learning how to get out of an induced stall first experience. river pond lake
When you see the areal shots of the crash site, it’s amazing that it came down in an open lot, instead of on surrounding buildings. BTW, the collective knowledge demonstrated in the comments on this channel is greatly appreciated.
I notice there is much discussion concerning VRS vs SWP. When I was a student in helicopters (long ago and far away) the only term used was SWP. I can see why there is now confusion on this subject. I understand now that the term SWP can be used to describe "inadequate" power to arrest descent rate. Additionally, SWP can also result from VRS. When I was discussing VRS (aka SWP) with my students I related it to prop cavitation in a boat prop, at least to those who operated powered watercraft! In any case, we still do not know what initiated the event that led to this tragedy. My heartfelt condolences to the families and friends of these aviators. Great work Juan. I really enjoy your videos.
I think the confusion arose from difference in navy/marine/army manuals. .Vortex ring is the preferred term now .settling with insufficient power should be the other term
I think the problem with the R-44 is that while cheap and simple enough as a trainer, unlike say a cessna 172 which is built like a tank, the r-44 isn’t. Obviously as a selection bias (statistical) training craft are more likely going to be involved in accidents simply because their prevalence in training, but 172s don’t stand out since they just take abuse
We live in Rowlett, what a crazy event. The even crazier thing is that it landed in an empty field next to many stores and a busy street, Lakeview parkway.
Inertial Sensor Modules (IMUs) have used in motorcycles for 10 years now. Motorcycles are subject to yaw and roll axes, lacking only the z (altitude) axis of aircraft. Riding motorcycles near the edges of the performance envelope is easier with IMUs and software that control brakes, throttle and suspension on sketchy surfaces. After listening to comments from helicopter pilots about how easy it is to mishandle the controls, I'm wondering why IMUs and software-aided controls are not incorporated in helicopters like they are in Airbus planes?
I've never seen an IMU in a motorcycle but hobby 'drones' all use them for stabilisation. Without an IMU they are impossible to fly, even for experienced model pilots. Human reactions simply aren't fast enough. With an IMU a 10 year old can fly one. For full size helis the limiting factor is cost. It is hugely expensive to certify fly by wire controls.
You did your usual great job of explaining a complicated subject in easy to understand terms. Most helicopters don't "like" to have the rotor system unloaded. Almost all control inputs in helicopters need to be small and smooth or they can get away from ya in a hurry. Always hate to here of fatal crashes, condolences to the families of the victims.
i live in rockwall, about 3 miles from rowlett. pretty sure that's the same heli i always see circling about in town, a white r44. sad to hear it's gone.
You did a pretty good job covering this without being a rotary pilot (I could be wrong!)... I did my transition to rotary at first with the R44, and then I went to the Enstrom, for this very reason. I'm not going to put my heli instructor on the spot, but this apparently is/was a known flaw. Living in the Dallas area, I saw this right after it happened, and it took my breath away. I'm not an aeronautical engineer, but there should be limits on what I was brought up to call a "Boom Strike".. It's the same thing, and when you trash the blades, you will never be able to do a successful auto... I don't care how much time you have. This is a ride into the ground that gives me shivers.. I don't recall what I read a long time ago, but the state this woman put this helicopter in was recommended by an outside contractor who "specializes" in this situation... It has been a long time but there is partial ring state issues in this.. Just, personally, and again, I AM NOT an engineer, but I damn sure will never fly in a helicopter again that I can jerk on and cut my tail off... I DO NOT like the high masts of the Robinson, and while I have had great experiences in the Enstrom, I don't like these types of helicopters... However, have fun if you wanna go cheap. This beautiful lady crashed near my proverbial back yard. I can ONLY imagine what she (and her student) were going through trying to regain control while lawn darting into a fireball... How about you? SAD... Don't create a fatal friggen fail...
Very good explanation... this made me think of a video I saw where a CH 53E Sea Stallion chopped off it's own refueling probe...I'm wondering if the same thing happened in that case...
Enjoyed this insight, Juan-thank you…from everything I’ve read, sounds like 2 very good people were lost in this unfortunate training accident. If it were easy, everyone would be a pilot…..Condolences 🚁🙏🏽
I have never flown a R44 but being a Bell guy (OH-13,Huey,OH-58, Cobra,Bell 47,Bell 205,206,212,and 412), I wonder if that goofy offset cyclic system makes it more difficult to correct( or over correct) a student pilot on the controls in the right seat.The left cyclic,instead of being in the conventional position between the pilots legs, is at an angle and quite a bit higher.
One of the things we train for is to correct students while the cyclic is up in the air. Starting in CFI with an instructor all the way to internal recurrent training. It is goofy, but you get used to it. If I’m flying, or have to take the controls from a student, I position the cyclic against my thigh again for better control authority. I never demo maneuvers with it in the air, safety and aircraft control comes first.
Back in the late 80s I was working working on my helicopter add-on. On my first lesson in the R22 me and the instructor were flying along and the machine started vibrating and the instructor took the cyclic and went aft then forward. This happened a couple of more times, the instructor explained that the blades were flapping and if you let it go unchecked that it could strike the tail boom and that was just straight and level flight. It was a design flaw that has since been overcome. I had some scary moments with the Robinson's and I personally refuse to fly in one. I ended up getting my training and rating in a Hughes 269. Unless they have changed their rules the FAA will not allow their people to do check rides in a Robinson.
They do. There is now an extra piece of FAA certification (SFAR 73) for flying a Robinson aircraft, to be hyper-aware of low G situations and to pull back on the cyclic to load the rotors, to avoid flutter which can damage the rotor mast, or indeed chop your own tail off. It's required of everyone who even takes the controls of a Robinson R22 or R44, so the pilots would have been certified. They may have been attempting another training manouver and accidentally exceeded design limitations in this way, perhaps the pilot routinely flew different aircraft and was less familiar with the Robinson, but I'd say it's hard to imagine it wasn't pilot error in this case.
We got it on the MV-22 osprey when I worked on it in the marine corps. A real helicopter might be different, however when it happened to us it was often called a “swashplate overtilt”. Granted we did have sensors all over the place on the aircraft. If a pilot would ever push in power to much when landing in helicopter mode, sometimes we would get “flapping critical or caution high hot”. Which meant one of the rubber bearings within the hub cracked in half. It’s very interesting how a normal helicopter operates and it’s even more interesting how the osprey operates.
I am not coordinated enough to fly helicopters. I'll stick with a Skyhawk. I understand that the Russian Hind helicopter is very prone to tail boom strikes during maneuvering. Good explanation of what may have happened with this incident.
It's surprising that if they know that abrupt movements cause the rotor to strike the tail, that they wouldn't change their design to prevent that. Surely it wouldn't be a difficult thing to implement. Maybe add tension on the controls so that you can't push them so quickly.
The maneuver they were doing i believe,, is also referred to as Settleing With Power. In many cases, Mast Bumping will ressult in Main rotor separation. This happened with Air Evac Lifeteam out of Vilonia, AR. A few years back. I had been a mechanic on that aircraft earlier and the Flight Nurse was a friend. I am a helicopter mechanic/pilot and this is always in the back of my mind.
Settling with Power is essentially the same thing as VRS - though this is widely debated and has caused god knows how many arguments and lost friendships over disagreements. the true terminology that separates VRS/SWP is "Power Settling" Settling With Power and VRS are the same thing, you have power applied and the rotor is losing its ability to keep the aircraft afloat, this is inherently due to VRS where the descent is over coming the velocity of the rotor downwash and the aircraft is recycling its own wake. VRS Occurs in a very specific region of hovering.
0:51 Juan, there is a aerodynamic phenomenon that occurs when the helicopter reaches Vne. As you increase collective and push forward on the cyclic to increase airspeed in flight, it moves the tail of the helicopter closer to the main rotor path as speed increases. One of the few situations in which a tail could be severed off of a Robinson. When you encounter gusts of wind at higher airspeeds, its possible to enter a tail strike scenario with the main rotor because the flight procedure requires you to decrease airspeed when encountering strong winds at high airspeeds (aft on cyclic lower collective and left pedal to counter the torque of the main blades. The spin on this section of flight is if you are in a strong climb (however lower airspeeds) and encounter the gusts of wind it is possible to want to nose forward and enter low-g mast bump/rotor strike on the tail scenario which would explain the folded main rotors. Strange things happen to helicopter airframes when stress tolerances are overloaded or you input the wrong control during a critical moment.
So, the nose would have a tendency to tuck under in a gust? Interesting. I know of a crash involving a Sikorsky S-76 that tucked its nose and chopped off the tail boom when a float bag accidentally inflated at significant airspeed.
Correction: During Blade Coning the Rotor RPM speeds up instead of slowing down. Think about a figure skater bringing her arms in, the speed of the spin increases. It’s called the Law of Conservation of Angular Momentum.
Blades cone up during low-RPM as the centrifugal force that normally holds the blades "flat" is reduced, and the lift produced by the blades pulls them up.
@@ganthrithor that doesn’t make any sense. Have you seen the blades on a CH-47 chinook? When the blades are not turning the blades are drooped. The moment the RPM is increased, they rise. The faster it spins (higher rpm) the more it cones.
@@pnorva There's no lift when the helicopter is sitting flat-pitch on the ground. Blades going straight out to the sides perpendicular to the axis of rotation is not coning. Drooping is coning in reverse. When you pull pitch, the blades lift up and cone. When you pull pitch while decreasing RPM, they cone higher.
@@ganthrithor That’s not what I meant when I said coning. When you pull pitch, yes it cones because the weight of the helicopter is now affecting it. The load on the blades causes it to cone. If you pull aft cyclic during a high G maneuver, it adds even more load and cones. As it cones, the RPM speeds up not slows down. If the blades are unloaded, let’s say on a neg G maneuver, the blades will be flatter and RPM will decrease.
I too got my rotorcraft license (in an R-22) as an add on after about 1000 hours flying fixed wing aircraft. I had always wanted to fly a helicopter but my wife at the time forbade it. The first thing I did post divorce was take rotorcraft lessons. It was tough to master but SO much fun to fly once mastered. Anyway, I have not flown a helicoper in quite a while but have about 250 hours in the R-22. One thing that was drilled into my head regarding the R-22 (which also applies to the R-44) is to NEVER do any low g manuvers as this can easily be the result. In a fixed wing, pushing the nose over is a non-event so I had to completley change my way of thinking when in the R-22. Just my opinion but I think it very likely this is what occured here. It would take only mere seconds in a low g manuever to cause the main rotor to contact the boom. It would have happened so fast that the instructor would have had no chance to correct it.
It seems odd to me that the rotor did this. The rotor blade runs "parallel" to the boom, and if it were to torque enough to contact, the damage seen would be at more of an angle. This damage seems to run perpendicular to the boom. My first thought when I saw the video of the man carrying the tail section, I assumed the damage was caused by the drive shaft failing inside the boom at the point of the break.
What a tragic one. You point out what many of us have often thought, when looking at accident reports. (not referring to this one, since we don't know the specifics yet) Knowing "how to fly" an aircraft is not enough. Pilots should all be aware of the design limitations and all the quirks of their aircraft. (I also think that all pilots of fixed-wing aircraft should know their reduced-power, and power-off glide ratios. These things (and much more, of course) need to be part of all new pilots' education, and shouldn't be lost, just because people are rushing to fly right now.
It doesn't help that in the helicopter world, the vehicle that is popular as a trainer because it's cheap wasn't designed to be friendly or forgiving to pilots not experienced with its quirks, ie pilots in training.
While acting as chairman of Hiller in the mid 80’s we lost our senior test pilot while testing a new series of “hot and high” blades. Anytime you “unload” the blades of a teetering rotor system they become extremely unstable. This is a characteristic that was well documented during the Vietnam war. Unloading is when you subject the blades to near zero “g” or a negative “g” force. Depending on atmospheric conditions they can be subjected to other influences such as wind gusts or turbulence that can cause unwanted deflection when approaching an “unloaded” condition. A rotor system with a larger mass will tend to increase the dampening the rotor thus lighter blade systems can be more unpredictable. Further, Dampening can affect an oscillation that can occur when the blade reaches the end stop and the blades flex causes an increased deflection and subsequent oscillation. The blades will deflect or oscillate between end stops with an increase the rate of oscillation and an increase in deflection of the blades until they 1) snap the mast, 2) deflect the blade sufficiently to come in contact with the boom, or 3) cause one of the blades to separate causing s severe inbalance of the rotor system which in turn will cause total destruction due to centrifical force.. A stable teetering rotor system most be kept fully loaded and avoid any violent manoeuvres close to the edges of the performance envelope. This is one of the reasons the Hugh’s 500 became popular with its fixed rotor system during the war as it allowed the aircraft to be far more manoeuvre able and forgiving. That test pilot was one of the most senior test pilots at the time having just certified the Apachie and Hugh’s Notar. It was in an Fh100 turbine.
Wow, very good Information here, thank you.
I did aerospace engineering, have fixed wing PPL and had to read this twice.
I agree with KAM this is first class information.
I also found this link on the Vuichard Method to recover from a vortex ring. Its pretty good at showing what the Vortex Ring is. I didn't quite get the opposite rudder until I simulated the force directions in a swivel chair. It then made perfect sense. If you think the link isn't useful or appropriate let me know and I'll remove it.
ua-cam.com/video/HjeRSDsy-nE/v-deo.html
I know personally that you can cut the tail off an MD-600 NOTAR if you try. See MIA00FA102 (hint Florida man says “watch this!”). It flew over my shop every morning eastbound. Such a magnificent machine. I’ve never seen a helicopter hold station like that one. Then one day it was gone.
Wow! God bless him and all the others that afforded us the “tombstone” technology. It amazes me that things that can seem so simple are so truly complicated. Before the Osprey accidents, I had never heard or the “vortex ring” effects… holy cow, like there isn’t enough to think about just operating in a three dimensional environment…
So true! I was a student pilot At Palomar airport flying Flying a new R22 serial 38, I was taken under that test pilots wing and watched him do the first autorotation in the Hugh's NOTAR prototype, a converted OH6. He once told me if I fooled with that 2 bladed R22 system it would kill me, I still think about all those test pilots I had lunch with "especially him" who pushed new untested machines to the limit for many future helicopter pilots safety. Thanks to his care, and no BS advice, I'm still alive and flying helicopters 41 years later, Thank you Charley! R.I.P. Charles Hench, Chief test pilot, Hugh's helicopter 1979-1981
I knew the CFI when she was a Forest Service helitack firefighter. Great person that always was smiling and a good person to be around. She will be missed. RIP Lorax.
I met and briefly spoke to this CFI at HAI back in February. Ms Trout made a remarkable impression on me as being very outgoing and cheerful, but also very bright and professional. She was extremely passionate about flying and had a very promising career ahead of her. This was an incredibly tragic loss.
was she good looking
I recently completed my helicopter private license and have about 450 hrs fixed wing. There is a stark difference in training between fixed and rotary wing with a much greater emphasis on emergency training and avoiding states/actions that will kill you. About the only advantage a fixed wing license gives you is in radio comms and navigation (but even that’s not quite the same as you cannot ever take your right hand off the cyclic, so folding charts etc is all one-handed and maintaining altitude tolerance whilst distracted is much more challenging than fixed wing).
There are some actions in responding to abnormal states that require an ‘opposite’ action compared to fixed wing flying; an engine failure in fixed wing during cruise requires converting excess speed to altitude and getting to best glide thus BACK with your left hand on yoke, to enter auto with R44 (less than 2 sec window to do so otherwise unrecoverable fall to the ground) you push DOWN on collective with left hand and gentle slight aft on cyclic. It took a while to get the brain tuned properly into that. Also low g events require very gently delicate response compared to what you may instinctively do in a fixed wing aircraft otherwise mast bump / tail boom strike.
The instructor ALWAYS had his hand touching or adjacent to cyclic and collective during any turbulence even right at the end of the training as there are absolutely no do-overs in a helicopter.
I found the transition fascinating and it’s much more challenging to learn to fly safely than I would have imagined. Despite picking up the basic flying skills pretty quickly re manoeuvering, hovering, power management etc it took much longer to get to solo than the case for fixed wing as you have to be competent in all emergencies and abnormal conditions. It was about 25 hrs to solo compared to 8 fixed wing. I had to reliably demonstrate autorotation entry and touchdowns, avoidance of mast bumping, avoidance of tail boom strike, avoidance of vortex ring state, loss of tail rotor effectiveness, tail rotor drive failure, jammed pedals, engine failure in hover and engine failure during takeoff/transition.
Once you have all that nailed you get to do your first solo circuit!
You hit the proverbial nail on the head with your post. You should come fly in Phoenix AZ if you haven't already. On top of everything you wrote about you can enjoy the FAA designated complex airspace along with the lovely flying weather. The daily forecast is usually, sunny with a slight chance of a runway incursion and a possibility of a mid-air collision as the day warms up to 120 degrees. And always remember what was always posted in every flight school I've been in for Rotorcraft/Helicopter "It's not a matter of...... if you crash, but when" considering helicopters are the best aviation definition of an unstable aircraft.
Safe travels to you, that like myself are the few that can do what we do.
Alex, Scottsdale AZ - Commercially Licensed Rotorcraft/Helicopter, Instrument Rating, with a Fixed Wing add on. (Not Currently current on any for reasons associated with this video, but not in relation to said video and or anyone directly involved, or connected to this tragic event). Just decided to take a break.
@@alexdelarge8749 one day sometime soonish perhaps... I'm from Perth in Western Australia and fly from YPJT. Frequent traveller to the US pre-Covid and looking to return soon. Keen to explore a little in both rotary and fixed-wing - recently bought an M5-235C to build some further skills.
Somewhat unusually I did my ab-initio fixed-wing training in a 300hp Stearman...always up for a bit of a challenge.
I have a few videos on my channel of fun in the Stearman around Perth 🙂
You had to do touchdown autos? In the states? Not required or recommended by the private PTS.
@@Chris-bg8mk yes we had to do touchdown autos. Also not required for PPL(H) here in Australia, but the school I went to took a slightly different approach to most as they wanted to produce pilots properly able to manage autos to the ground. The Chief Flying Instructor has a few thousand hours of heli-mustering experience where a lot of time is spend on or inside the edge of the dead man’s curve so he was really big on safely getting onto the ground in an emergency and being pretty sharp on managing autos.
@@Chris-bg8mk Some helicopter flight schools do teach touchdown autorotations. Accident chances do increase, but sometimes those last few feet make all the difference. In 1981 when I got my Commercial Helicopter rating the school I attended taught touchdown autos in their Hughes 300’s, and while difficult to master, really brought up one’s confidence level. Came in handy a few years later when I had an engine failure in a Hughes 500D. Things happened quickly, but the training kicked in and I autorotated into a farm field and landed safely. Engine was toast, but not a scratch on the 500.
Later when I started flying Bell helicopters I attended their flight academy in Texas every year, and we did ALL the emergency maneuvers to the ground. The instructors were seasoned pilots, many of them Vietnam veterans, and it was fun to see them do things in a helicopter I didn’t think you could do.
By the way, the Army used to do touchdown autorotations, but they found that they were damaging so many of them that they went to doing power recovery’s. 😏
There are a handful of incredible channels that talk about flying. Each of which give another vantage point. You give a good understanding of the technical nitty gritty.
Juan is so good at explaining these cases in easy to understand terminology. Thank goodness because I need the Aerodynamics for Dummies version.
My heart breaks for the families and friends suffering from this tragedy! RIP🚁
It’s called low-G mast bumping. It can happen to any semi-rigid rotor system, including Army UH-1. Army and Robinson Helicopter have special training for avoidance.
When we fly game surveys here in southTexas in R44 I notice they have the placard “NO LOW G PUSHOVER” When I asked the pilot about it he explained it technically and this just reiterated your lesson at the end. Fly safe!
As a former helicopter pilot now fixed wing. You are correct. This maneuver requires only two steps to get out of. 1. Lower collective and 2. Gentle forward on the cyclic. You want to get airspeed then climb out. All movements should be the width of a dime.
Unfortunately… once the rotor is unloaded, movement of the cyclic will usually cut off the tail and sent the main rotor right into the cabin where the lilt is sitting. Never get light in the but.
When Robinson helicopters arrived on the scene the 2-seat R-22 (which has the same rotor type as the R-44) appeared to be a good trainer. Flight schools bought the R-22 for use as primary trainers. This resulted in several fatal accidents where student pilots would unload the rotor with incorrect cyclic inputs, which caused rotor blades to strike the fuselage or the tail boom. There are a couple of special regs (SFARs) that were created to address this
Correct.
No amount of sfars will correct a faulty helo design
@@rfcdgafI was wondering if they couldn't put the rotors up higher, put the tail lower, or even make a lock that doesn't allow you to do this
@@jimlthor
It's called a fully ridged or full articulated rotor hub.
I really like the way you drill into the core problem: Knowledge Transfer. I've worked in industrial design and manufacturing since the '70's and have kept up with technological changes to the industry. Passing on what I know to a diminishing number of people is creating a situation where knowledge will die and be replaced by automation. Which relies on the software writer's knowledge.
Knowledge transfer should be irrelevant. This problem should be made impossible to occur. It should be designed out.
@@geoffnewman3109 As long as the designer has the knowledge.
SFAR 73 to Part 91 is required reading to be able to learn to fly in a Robinson by law. It covers i) energy management ii) mast bumping iii) Low Rotor RPM (blade stall), iv) Low G hazards v) Rotor RPM decay among other requirements.
Of course all of these are l possible in any two bladed rotor system. Huey’s included.
Thank you for the explanation, Juan. I am an R22 student and both my instructor and I were talking about this. His take was they essentially had an SWP (settling with power) either accidentally or as a training exercise and exactly as you said, there had to have been bad inputs, at a high rate of speed followed by another counter-input abruptly that caused the rotors to strike the tail boom and sever it. I have practiced SWP to the extent that is allowed with one of my instructors at 3000 ft and I remember just how scary it was to drop so fast (the feeling of falling and gravity sucking you in) and how strong you needed to be mentally to avoid doing what your brain wants to do which is to pull more collective and aft cyclic but instead you need to smoothly apply very little cyclic forward and let the rotor blades grab fresh air and magically the feeling of falling stops and your rate of descent slows down. The fact that this new CFI was training a fixed wing pilot makes me think that the student pilot reacted based on their fixed wing training and the instructor didn't have the power or time to react appropriately causing this catastrophe but we will know whenever the report comes out I hope. Tragic loss nonetheless, I feel deeply sorry for all the families involved.
The procedure is to reduce power and initiate directional flight. The hardest thing to do is to reduce power. The directional flight can be in any direction. I flew helicopters for 26 years in the Army and forward flight is not always possible, hence the procedure of establishing directional flight. I think we should all stop speculating and wait on the accident investigation. It could be myriad of things that brought this aircraft down. It’s unfortunate there are not available civilian simulators for students to learn emergency procedures. We’re very fortunate in the military that we have the opportunity to practice every emergency procedure imaginable that you can’t practice in the aircraft. Prayers go out to the families.
@Johnny D's oh sure, all the time. 😐Airborne
@Johnny D's never make it out as a hole person
@Johnny D's not fast enough
@@bks252 better sims is key
You may not be a chopper pilot but it is another complete follow up with what is known at present. Thanks Juan!!
JUAN,Hello, gee sad situation, sad to loose 2 people,I had only been in the 4 placeROBINSON ONCE, BUT HAD MANY FLIGHTS IN LARGE SICORSKY & an older BOEING VERTOL, , I had NOT yet heard of this one ,so thanks for the update, 🇺🇸🇺🇸🇺🇸🇺🇸
I flew off my Navy ship on the ships helicopter over part of the Mediterranean Sea to Lisbon, Portugal when getting out of the Navy in 1981. The flight was flawless and smooth but I was a nervous wreck the whole time as I always am when I had to fly somewhere. Imagine the guy that's leading the Indy 500 with ten laps to go. You're listening for any noise or vibration coming from that machine until you are safely in victory lane. That was me whenever I had to fly.
Just look at the global history of Robinson mast bumping accidents, especially those in NZ, much more common than people think.
My wife is a teacher in Garland, right next to Rowlett. That helicopter flew over her school and recess playground when they were outside. The accident was two minutes flying from the school.
Amazing description of helicopter flight dynamics by a 777 pilot!
ATP rated helicopter pilot and CFI/CFII helo - this has all the classic indications of mast bumping - concur with the discussion that JB is leading here. Also the Robinson R44 is covered by a SFAR - the requirments of which must be fulfilled to act as PIC on this model. Keep up the great work JB.
Do you reckon the rotor is behavingly like it's just been mast-bumped and gone through a tailshaft?
Thanks Juan Brown as usual explained where we can at least have a idea of the incident.
I took a Commercial Rotary Wing Add-on course flying Bell 47s with U.S. Army combat experienced instructors. An important lesson was to not move the cyclic control more space than the diameter of a half dollar, unless performing a quick stop. Even then it was a gradual effort. I completed the five week course in three. My instructors, especially Bob Seales, we're well experienced and dedicated to safe practices.
The Army was the first to learn what mast bumping was and what was causing it.
They lost many helicopters to this very thing.
1:29 one of the best educational demonstration I've seen on this mechanism, so clever 👍
Way back in the day when I was training in a 22 there is a situation where you can do that, high altitude hover stick forward hard stick back. A rookie after me took out that trainer in Austin years ago.
Such a sad loss for a guy who gave so much back and did so much for the Equine community nationwide RIP Bud ❤️
Yes; his family and friends are affected, and everyone of his many clients and their animals.
So sorry for your loss. 🕊
So sad. Prayers for his family and for the Instructor Pilot. So sad. Horrible crash.
You're so good at explaining mechanics and aerodynamic forces.
Also situations which may help create less margin for error.
Rest in Peace trainee pilot and trainer..
Let's learn from this. Especially in a time of pilot need.
I learned about this phenomena called mast bump in DCS (flight sim) in the Huey as I kept watching my main rotor keep sailing off in the distance without me, lol.
Millennials know and invented everything, didn't you know that Juan?
It's best to learn of it in a sim than for real.
Someone posted a really cool Army video in the VTOLVR that explains these types of things. I think I learned more about helicopters in that one video than from anywhere else
Just an FYI never pull down on a robinson main rotor blade. Push up on the opposite blade.
With what little I know about rotary wing aircraft, mast bumping is to be absolutely avoided. Keep a positive G load on the main rotor at all times. Avoid negative G pushovers, etc. I have real world fixed wing experience and Jet Ranger 206 simulator experience. Yes, smooth and minimal inputs on the controls of a helicopter.
Maybe more simulator experience and training can reduce these accidents.
You should qualify your “blanket statement “ about keeping positive g’s and avoiding pushovers in helicopters. 100% depends on following POH and manufactures operating limits. Many, many helicopters can and routinely do low g maneuvers, the R-44 and B 206 are not in that category. As a military instructor pilot in the AH-64 for 16 years we taught and pilots had to perform a
High/Low G maneuver…… pulling into a 2 G pull up followed by a .5G push over. Understand not all helicopters are subject to a low G restriction.
May God comfort the families of the two pilots. Thanks for this story Juan.
As a fixed wing pilot, a few years ago, I was at a local air show and a few med and military copters were on static display there. A crew member “explained” to me that helos don’t fly - they beat the air into submission.
Right. Every time I see a helicopter in the air I wonder why.
@@soaringvulture
Cynical lol!
How can a friendly greeting fly? Or beat the air for that matter...
As a commercial fixed wing pilot about to start my rotary training in Robinson helicopters, this phenomenon is extremely interesting. Thanks for the info Juan! Hope you're enjoying NYC. I've never been... yet! Hopefully someday I'm filming some awesome stuff from a helicopter over NYC :D
Anyone who has flown a Robinson, like me knows that the first thing a good instructor tells you to never do in a Robinson is to get into a negative G situation, mast bumping is what its called and its mentioned all over the operating handbook. The blades can literally wrap around the cabin and will take off the tail boom, no recovery from that.
Legally you have to be instructed on low G, mast bumping, energy mgmt, low rpm, and rpm decay before manipulating the controls of an r44 or r22 based on SFAR 73.
Memo to self: never consider getting climbing into a Robinson, because I make every mistake in the book at least once, and a few new never heard of mistakes too.
@@ushouldntjudgeme3683 Don't fly a helicopter, lots of those mistakes in the book lead to fatalities.
@@spider0804 thanks that's good advice, I'll just leave it to the fools to fly the Robinsons
Why would anyone fly one of these ?madness
Thanks Juan. I learn something new every time I visit the blancolirio channel. All the best, Mart in England.
Very tragic event…my wife and I knew the CFI and were actually scheduled to fly Friday afternoon just after the accident happened at SKY. School is grounded as of now while FAA and NTSB are there investigating.
Since 1982, 600 people have died in Robinson helicopter crashes. But Robinson continues to mass-produce nonetheless, and it does so without having to make many changes to its flawed helicopters.
Yeah, It would likely be the worst trainer on the market...considering fatalities and their unwillingness to strengthen the blades...I always cringe when I see another chop its own tail boom off and the occupants die another grizzly death. When will they learn.
I saw R-22 main blade cut the tail boom during a hard landing practicing auto-rotation at SNA years ago. Luckily all survived.
I learned a lot here Juan, again thank you. Very sad to hear the outcome of the pilots.
Thank you for this report. You did a very good job in explaining it.
Best explanation of how a helicopter operates. Always a great job. Sad to hear that topic.
Thank you Juan. Brooke we all miss you.
The way the metal in the tail section is splayed outward in all directions around the break point it makes me wonder if a coupling or something failed in the tail rotor driveshaft which then ripped up and separated the tail. There appears to be some sort of coupling on the shaft at this point in the tail section held by the NTSB investigator. Also there is no noticable damage to the rotor blades until it rolls inverted then as soon as the blades hit the tail they start to come apart.
I believe the tail rotor had already been severed by the time we see the helicopter in view on the video. Then because of the violent rotation the blades severed of more of the tail boom. Go back and look at the first couple seconds of the video and you can see that the rotor assembly is not visible. I believe that's because it is above the camera frame tumbling down above the helicopter.
Same as an accident at Broome, Western Australia in 2020.
Yes the aircraft might have been “operated outside of it’s design limits” but Robinson’s have a very high incidence of this very problem even when compared to other training helicopters. They also have very light blades and this means low rotor inertia causing still other problems. I have lost two friends (both were careful and fairly experienced pilots) flying Robinsons so I am pretty biased. Robinson’s are inexpensive compared to other Helicopter and that is why they are popular trainers. They are not well suited to this role.
Low inertia blades also give you faster RPM recovery. Like any helicopter if you dont hit the spinny things on objects and manage your RRPM blade inertia is irrelevant.
One flight school lost a pilot and a trainee and they went to Frank Robinson complaining about it trying to sue him. He told him to kick rocks he never designed the helicopter to be a trainer
and how many accidents. one hundred? 43 just in a short span of time years ago. some body has deep connections to government official to allow this garbage to continue being manufactured.
Ironic that it's attractive as a trainer because it's cheap but not attractive as a trainer because it's unforgiving to inexperienced pilots or pilots not specifically experienced with this helicopter.
Yet, a flight school can't buy a better, more expensive trainer because people will go to the cheapest school...because you get what you pay for doesn't cross their mind or their desire to fly is bigger than their budget to fly.
@@Texas240 cheapest to operate. best fuel burn. less complicated. the only thing that was ever super dangerous with the robinsons was the fuel tanks. a lot of them didnt have puncture resistant bladders. chances are the trainee did something wrong. they mentioned he was an airplane pilot working on his helicopter rating. my guess is he did a push over unloading the rotor and it hit the tail cone. but that picture of the tail doesnt look like it was sliced. looks like something blew it up from the inside out
For someone that isn't a helicopter pilot, you explained that very well.
He explained mast bumping which doesn’t have anything to do with this crash. The aircraft crashed because of a boom strike as a result of a low-G condition. Helicopters are designed to hang under the main rotor with the rotor blades flexing up. In a low-G situation the helicopter’s momentum is forced up into the rotor system causing the rotor blades to flex down where they can contact the tail boom.
@@nocalsteve Besides coning, I’ve never heard of blades simply flexing in the wrong direction, and I taught helicopters for a couple years.
Low G/mast bumping are taught together. The whole idea is unloading the rotor disc which allows it move independently from the rest of the system. At that point, it’s extremely unstable and any large control input could cause the blades to flap far enough to exceed the mechanical stops and contact the mast and/or the boom.
@@Hamchuck112 Am also a Rotorcraft CFII and that's exactly right. Mast bumping is taught in association with severing the tail as one, the other, or both are very likely should a pilot enter a low G state and make any abrupt cyclic control inputs. Especially since the low G condition is usually accompanied by a rapid right rolling action because the main rotor and fuselage are working relatively independently and the tail rotor thrust causes the helicopter to roll about the longitudinal axis. Thus the untrained pilot's reaction would be to immediately input left cyclic to counter the roll, but because the main rotor is fairly unloaded, it can flex down below the droop stops and contact the boom and/or mast. Pretty catastrophic results regardless of if only one or the other happens. Definitely tragic and my heart goes out to these pilots' families.
Thanks Juan. Even though you aren’t a chopper pilot you get the info as fact from the proper sources and relay it to us. Tragic incident and condolences to all involved.
In the late 80’s we had a CH 136 Kiowa return to base with a chunk missing out of the tail rotor drive shaft cover. Pilot had mast bumped while low level training, flying over trees and dropping down on to fields. Replaced the trds cover, seat covers and air freshener, return to service.
These are two different things, your guy had a boom strike, not a mast bump. A mast bump damages the main rotor shaft, a boom strike is when a main rotor blade hits the tail boom.
You can explain the physics of rotorcraft to the most basic examples, your an amazing teacher
Having that very same problem in trucking.
Especially OTR and Hazmat Tanker like me.
The new teaching the newer teaching the absolutely green!
Thank you Juan. I know I’m not the only one to have asked you to cover this, but I specifically wanted to hear your take on it, because even your educated guess is far more likely to be accurate, than many others. Your commentary is also more likely to be balanced without making conjecture. Thanks for the explanation of the rotor balance and mast bump concept.
Of course we will have to wait for the official answers, but one total guess of mine is that a rapid control input was introduced, causing the rotor to flex so much that it took the tail boom off.
One video clip of the incident shows the R44, already without the tail, and managed to make a hover, and looked for a second like it could autorotate, but lost it, rolled sideways, and the mains folded. Very tragic, I’m sorry for their loved ones losses.
It's a good explanation but it isn't what caused the accident.
@@zzodr it was a probable cause. We will most likely never know exactly what happened to cut the tail off that R44. It could have been the tail rotor drive linkage coming apart, it could have been exaggerated rapid control input, it could have been clear air wind shear, it could have been a combination of those things, all of which are probable causes, not for sure the cause, but probable cause. Furthermore if it were a factor of a newly certified rotorcraft instructor combined with a new to rotorcraft student pilot, then maybe, MAYBE a possible recommendation might be that newly certified rotorcraft instructors do their first 24 hours of “flight instruction”, re-certifying pilots renewing their existing licenses, and requiring new student pilots, new to rotorcraft, to have instructors who are certified to train students who are new to rotorcraft. Or maybe there’s no reasonable recommendation to be made, since there’s no way to know “for sure” what caused the tail rotor assembly to separate from that R44.
The fact that they got it to hover without the tail is amazing after that it was horrible to watch.
Of my 2000+ hours in helicopters, .5 hours was in an R22. I booked an hour, but I was so terrified after the first autorotation, i told the instructor that I was done. Kids like them because they're fast. The R22 and R44 are giving the industry a bad reputation.
In the R22 and R44 mast bumping wouldn't necessarily cause a tail boom strike. It will, however cut notches in the main rotor shaft that can cause the shaft to fail, turning the machine into a ballistic brick. (One of the helicopters at the school where I trained came extremely close to main rotor shaft failure while an instructor was demonstrating a low-g maneuver to a prospective student and encountered mast bumping. The prospect decided his life was too dear and walked away without taking his first lesson.) Low rotor RPM is a more likely cause of a tail rotor strike. These aircraft have low-inertia rotor systems, so the pilot needs to stay on top of rotor RPM. Typically, correction must be made within two seconds or the RPM can decay to the point that it cannot be recovered, even at full power, and the helicopter gets a case of "blew blades". I hold a commercial rating in rotorcraft and my primary training was in the Robinson R22.
You seem knowledgeable enough.
Why is a helicopter model particularly vulnerable to aggressive inputs, and is hard to auto rotate, widely used as a trainer?
Why not something more forgiving.
@@spider0804 - I was told that the Robinson R22/R44 behave more like many jet-powered helicopters, so if a student can master the R22, the transition to more complex types would be easier. This was in the days before fly-by-wire became commonplace, but now with computers actually flying aircraft based on control input by the pilot, much can be done to alter the "feel" of the aircraft using software.
As a Rotorcraft CFII, I can assure you that every book I've ever read indeed mentions that a low-G power pushover can absolutely end in a severed tail boom. It could be an and/or situation, but regardless, if either of those fails it can be catastrophic. That said you CAN make a landing without a tailrotor by initiating an autorotation, as that removes engine torque. Not completely sure as to how the helicopter would maneuver if it lost both the tail rotor AND the horizontal/vertical stabilizer. Also, any helicopter instructor that actually "demonstrates" a low-G situation maneuver in the air by actually entering into a low-g condition shouldn't be instructing. Someone's going to get killed, and it sounded like he came close with that potential student. That student was right to walk away. Every text on the issue makes it clear that even experienced test pilots have been killed investigating the low-G condition and that no pilot should ever attempt to actually induce low-G in a Robinson or any other semi-rigid rotor system.
@@spider0804 They were the cheapest for a long time, that's the reason.
Knowledge is easy to pass on, Hard won experience and the intuition that comes from that is some what harder to pass on and usually goes with us when we pass on.
Day 1 in my helicopter training was to talk about Low-G and how dangerous it is. If they were practicing high altitude hovering and descending with power if you move the cyclic forward too fast this is what can happen. Really sad. Condolences to the families.
As a former part-time heli pilot, your analysis is spot on. Robbies are very fidgety and especially an R-22. I realize this was an R-44, but very similar designs. Cheers and RIP to the two pilots. Sad scenario.
Years ago I was talking to a helicopter pilot who flew in the military. He said if you try to pick up a stationary helicopter by lifting at the ends of the rotor blades, the blades will snap in half. It's the centripetal force of the spinning rotor that gives the blades the strength to lift the helicopter. I have never wanted to fly in a helicopter since.
He is correct..
No it’s CENTRIFUGAL force (not centripetal) that keeps the rotor blades of a helicopter rigid while spinning from the axis of rotation, thus giving the entire rotor disk the ability to produce lift as a whole.
Think of it like this. Take a piece of string about two feet long, tie a one pound weight in the center. Now, place a finger under each side of the string about six inches out from the weight and raise your hands. The string will slip off your fingers but, the weight will lift. Now, grab each end of the string and pull outward with about ten pounds of force and raise your hands. The string is now ridged and will lift the weight. The centrifugal force of the spinning helicopter blades make them ridged enough to lift the helicopter.
In your example the weight is entirely on the ends, where in reality the weight is distributed through the blade, and entirely on the shaft.
If you pick a 747 up by the wing tips it will snap too...
Your example is misleading.
Nice to see you're in my hometown. Be safe out there, cheers !
Good explanation Juan. Here in New Zealand we have a disproportionately high number of these tail boom accidents on R44 and R22 helicopters. We’ve even had Robinson send representatives out to address the issue here. Much of it has been put down to flying these in overly turbulent , mountain conditions which puts the helicopter outside of its design envelope. Unfortunately, the result of a tail boom strike, is also a resulting cabin strike at the other end for the helicopter which results it fatal injuries to the occupants.
In the Navy back in '73 I did time in line division in our SH2D Seasprite squadron. While getting trained up in the vagaries of ground directing helos, and specifically the SH2D, I was introduced to the "droop stops". It was explained that the droop stops were weighted, pivoting, locking levers on the rotor hub that, when the rotor spun up to a minimum RPM, would pivot, unlocking the rotor blades so they could free float in flight. It was further explained that one of my primary duties when directing was monitoring the transition of the stops from locked to unlocked on spin up, and unlocked to locked on spin down, signaling the pilot on their position when transitions occurred. The price of allowing the rotor RPM to spin down without all of the droop stops engaged was a boom strike. Naturally I asked, "What do I do if the stops don't lock in?" The answer was to signal the pilot to pick up his RPM again, run to the line shack and get the red broom handle standing in the corner behind the door, and go back out and give the offending stop a "whack" when it came by. I resolved at that time that if I ever had a stuck droop stop that I would run and get someone from the AF/PP shop instead. Thankfully, I never did.
Would happen on the Wessex now and then, especially in the tropics where the grease on them would get gunked up due to the high humidity.
I worked on the NZ Navy SH-2G(NZ)s. We were also taught to direct the pilot to increase RRPM if a droop stop failed. If a stop didn't engage on the second RRPM decrease, the solution was to get a fire truck out to hit the stop with high pressure water from the truck's foam cannon. If that failed, the next step was to strap a bed mattress to the tai, hoping that the blade would bounce off it as it drooped when it passed over the tail boom.
@@theedmancometh6991 Good thing nobody knows how unsophisticated we were...Oh crap.
I still remember the Droop Stops in/out marshalling signal from my days in the Royal Navy, Fleet Air Arm, last century...... I never used it though as the Rotary Aircraft type I worked on had an unarticulated Main Rotor Head.
Called out droops in/out when I was a crew chief on H3's. Happened to me a handful of times. Just spun up and tried again. We used light lubricating fluid on the droop hinges. Very rare occurrence of a droop refusing to come in.
That's exactly how I understand how the robinson rotor system works. Frank Robinson came to our country and we explained how we use his helicopters and he was horrified
Mast-bumping was a big problem with Hueys during the war in Viet Nam. There is an Army video on UA-cam which addresses the need to keep the rotor loaded during terrain-following flight.
@Sam Samuels - This is a video I recall watching years ago when exploring the concept of mast slap.
I believe they had another one about LTE landings that showed the front flip and resultant crash and burn that stuck with people
I bop around for work a lot, mostly 185s and Beavers, but increasingly in R44s seems like every place that is allowed to use them is getting one. And now I am scared.
I don't like the haughty cowboy attitude of some of the pilots, but don't know enough about flying in order to determine if they are good(safe) pilots or not. You have made me want to turn down rides, but i don't really have much of a choice without changing not just jobs, but careers. Damn.
Thanks for the great info, hope you aren't covering me some day.
If you ever saw what the guys in South TX do while herding cows (and sometimes deer) it would blow your mind. I don't blame you for being nervous one bit.
Interesting comment Rhane.
I last flew with my father when he worked for Hughes in the 1970's. I was never scared because I was a kid (7-11). I haven't had the opportunity to fly in a helicopter since, and now at 56 I'm scared enough to avoid them but will jump at any opportunity to fly in any single or multi engine fixed wing aircraft.
That being said, is there a tactfully correct way Rhane Pfeiffer can screen the pilots (avoid the cowboys) he must fly with without offending them or losing his job (career).
Stay with those 185's bro
Control smoothness is much more important in helicopters and negative gs are no nos. We Army helicopter pilots developed a bad habit of fast approaches in Vietnam to reduce the enemies time to target us going into hot LZs. Absolutely not necessary in normal conditions. The big safety advantage of helicopter is that we can approach slow, shaking slow, and see every wire and every obstruction in the LZ clearly. Watch the rate of closure with the desired touchdown spot. Far back it appears to close at a brisk walk, same as in your auto coming to an intersection. Your helicopter pilot should decelerate on short final enough to keep that spot closing at what appears to be a brisk walk, just like when decelerate into an intersection with your auto. Fuss at him if the apparent rate of closure appears to speed up. Things appearing to speed up is scary in your auto. It is scary in an aircraft as well, especially the helicopter that can decelerate a bit more than the airplane. Just a note, the 185 and Beaver should decelerate as well. Yes, the apparent brisk walk rate of closure. The helicopter can get shaky slow and it will appear to be no apparent rate of closure at all.
A construction Company i worked for had a new Bell Jet Ranger and an experienced Vietnam pilot. My clients liked to fly over their projects and I had to accompany them. Hated every minute I was in the thing. Even more than when I was in the military and had to fly in them as an artillery forward observer. I’m a private pilot so flying doesn’t scare me but a seat in a helicopter does.
I could of miss-heard you, but when RPMR is low and loaded, the blades cone up. The phenomenon called settling with power or vortex which is based off the main rotor, LTE in the tail. Though vortex/lte can literally the same EP and avoidable. Move fwd and reduce power if able. SWP is harder to detect right away but LTE typically has warning signs and you can maneuver to get the wind in your favor. Fly low, draw fire.
Yep. Miss heard part of what you said.
Sorry to hear about this crash and your loss.
Good review. I enjoy your flights with Pete and James
in Ercoupe. Has there been an update on Tango and Juliet
crash in Cessna 140 at Williams, AZ? Bill
Interesting fact, Frank Robinson never built or designed this Helicopter to be a training platform. It was meant as a commuter for a businessman similar to the Cessna 150 Commuter advertising campaign.
Most rotary wing aircraft masts are hollow; more like a pipe than a solid axle shaft. It only takes a small dent or deformation to jeopardize the structural load bearing capability of said mast. By way of demonstration, you can place a cinder block carefully atop an empty beer can and it will support the weight. Now, tap the side of the can with a metal ruler and see what happens; crunch! While the term used is mast bump-ing, in truth, it is more like mast bump. Smoothness on the controls and a loaded rotor head (no zero or negative G maneuvers) will reduce the likelihood of mast bump in a two-bladed underslung system.
I don't really know anything about this stuff I just wanted to understand in a nutshell what happened here and you hit the nail on the head quickly and efficiently. Thanks!
I did the helicopter add on after flying fixed wing for 20 years. ASMEL/COMMERCIAL/INSTRUMENT. I flew the Schweitzer 300C, which is a fine heli, and not hard to fly. A heli is fantastic fun. In my opinion, since I can drive a car with a clutch, and motorcycles with twist throttles, I did not find it difficult to learn the helicopter. Our young people now have missed out on the background we older folks have.
I instructed in both. The 300 was slow but far better imo.
Hi Juan. There has been a heli crash in Melbourne Australia for your information. Five pax deceased. Rest in Peace.
Well defined and described Juan. Have always wanted to transition over from fixed wing PPL to rotor wing endorsement. Some how time passed by faster than I was motivated to do so.
Same here. Funny thing is, I started flying helicopters before fixed wing. I flew some 20 hours in a Bell 47 and was instantly in love. But life happened, money became short, had give it a break. When I had the chance to start flying again, it had to be fixed wing (less than 1/2 of the cost in my region). So I became a pilot, fixed wing, but 30 years on, never lost the profound admiration for helicopters.
My fix: started flying RC helicopters, which is the next best thing.
R22 and 44, Bell 47 and 206 rated, and the R44 scares the sh1* out of me every time. I love the 206, I hate the Robinsons.
A couple sites including a MSM site were alarmed at the Robinson "safety" record. Thanks , Juan for your rationality on this.
Robinson’s safety record is great…. If the PIC obeys the limitations of the aircraft. The problem is, people exceed the aircrafts limitations and break the rules as set for the safe operation of a Robbie. Plain and simple.
@@colt10mmsecurity68 Agreed. you can screw up in a Piper J-3,or Cessna 150/2 .
limits is the key.
Don't listen to the know it alls and arm chair pilots Juan. Your explanation was spot on. I started my training in 1981 when the R22 was just being introduced in Canada. I did the 60/40 commercial, the 40 on a Bell 206. I found the R22 to be a good trainer. One thing that was consistently drilled into us was the low rotor inertia and the importance of maintaining proper rotor rpm. When doing simulated engine failures/autos, getting the collective down quickly was paramount. I can't recall any mention of mast bumping during training, even on the 206. We had around 12 students and several Robinsons. We had one accident, a dynamic roll over on a snow covered lake. No other accidents in the 6 months I was there and we flew six days a week. The R22 was demanding and unforgiving of mishandling but I liked it. Transitioning to the 206 was a dream and it was more forgiving. Autorotations were a non event, even full ons. Thanks for your efforts and stay safe.
At age 68 I decided to add a helicopter rating to my CSEL, CSES and CG ratings. I did one lesson in an R22 and went home, googled it and saw the accident rates in the Robbies. The rest of my lessons were in a Guimbal Cabri G2. I had no intent of instructing or flying tours, just wanted to learn to fly a helicopter which I accomplished. Frank Robinson himself said the Robinson was never meant to be a training helicopter yet it is the most used for instruction in the USA and elsewhere.,
from what i have heard and read. train over deep enough water to save your life. that is what we did when learning how to get out of an induced stall first experience. river pond lake
Great advice to follow to increase chance of drowning in an training accident.
@@zzodr well if you cant swim go ahead and follow what these two. they ended up making the right decision.
When you see the areal shots of the crash site, it’s amazing that it came down in an open lot, instead of on surrounding buildings.
BTW, the collective knowledge demonstrated in the comments on this channel is greatly appreciated.
I notice there is much discussion concerning VRS vs SWP. When I was a student in helicopters (long ago and far away) the only term used was SWP. I can see why there is now confusion on this subject. I understand now that the term SWP can be used to describe "inadequate" power to arrest descent rate. Additionally, SWP can also result from VRS. When I was discussing VRS (aka SWP) with my students I related it to prop cavitation in a boat prop, at least to those who operated powered watercraft! In any case, we still do not know what initiated the event that led to this tragedy. My heartfelt condolences to the families and friends of these aviators. Great work Juan. I really enjoy your videos.
I think the confusion arose from difference in navy/marine/army manuals.
.Vortex ring is the preferred term now
.settling with insufficient power should be the other term
@@dpeagles Next subject must be dynamic divergent excitation! lol
Another super informative video, thanks Juan !!
I think the problem with the R-44 is that while cheap and simple enough as a trainer, unlike say a cessna 172 which is built like a tank, the r-44 isn’t. Obviously as a selection bias (statistical) training craft are more likely going to be involved in accidents simply because their prevalence in training, but 172s don’t stand out since they just take abuse
We live in Rowlett, what a crazy event. The even crazier thing is that it landed in an empty field next to many stores and a busy street, Lakeview parkway.
Inertial Sensor Modules (IMUs) have used in motorcycles for 10 years now. Motorcycles are subject to yaw and roll axes, lacking only the z (altitude) axis of aircraft. Riding motorcycles near the edges of the performance envelope is easier with IMUs and software that control brakes, throttle and suspension on sketchy surfaces. After listening to comments from helicopter pilots about how easy it is to mishandle the controls, I'm wondering why IMUs and software-aided controls are not incorporated in helicopters like they are in Airbus planes?
Your crazy, motorcycle and Helicoters are apples to oranges
I've never seen an IMU in a motorcycle but hobby 'drones' all use them for stabilisation. Without an IMU they are impossible to fly, even for experienced model pilots. Human reactions simply aren't fast enough. With an IMU a 10 year old can fly one. For full size helis the limiting factor is cost. It is hugely expensive to certify fly by wire controls.
One reason: certification cost.
You did your usual great job of explaining a complicated subject in easy to understand terms. Most helicopters don't "like" to have the rotor system unloaded. Almost all control inputs in helicopters need to be small and smooth or they can get away from ya in a hurry. Always hate to here of fatal crashes, condolences to the families of the victims.
i live in rockwall, about 3 miles from rowlett. pretty sure that's the same heli i always see circling about in town, a white r44. sad to hear it's gone.
You did a pretty good job covering this without being a rotary pilot (I could be wrong!)... I did my transition to rotary at first with the R44, and then I went to the Enstrom, for this very reason. I'm not going to put my heli instructor on the spot, but this apparently is/was a known flaw. Living in the Dallas area, I saw this right after it happened, and it took my breath away. I'm not an aeronautical engineer, but there should be limits on what I was brought up to call a "Boom Strike".. It's the same thing, and when you trash the blades, you will never be able to do a successful auto... I don't care how much time you have. This is a ride into the ground that gives me shivers.. I don't recall what I read a long time ago, but the state this woman put this helicopter in was recommended by an outside contractor who "specializes" in this situation... It has been a long time but there is partial ring state issues in this.. Just, personally, and again, I AM NOT an engineer, but I damn sure will never fly in a helicopter again that I can jerk on and cut my tail off... I DO NOT like the high masts of the Robinson, and while I have had great experiences in the Enstrom, I don't like these types of helicopters... However, have fun if you wanna go cheap. This beautiful lady crashed near my proverbial back yard. I can ONLY imagine what she (and her student) were going through trying to regain control while lawn darting into a fireball... How about you? SAD... Don't create a fatal friggen fail...
Very good explanation... this made me think of a video I saw where a CH 53E Sea Stallion chopped off it's own refueling probe...I'm wondering if the same thing happened in that case...
No
Enjoyed this insight, Juan-thank you…from everything I’ve read, sounds like 2 very good people were lost in this unfortunate training accident. If it were easy, everyone would be a pilot…..Condolences 🚁🙏🏽
I have never flown a R44 but being a Bell guy (OH-13,Huey,OH-58, Cobra,Bell 47,Bell 205,206,212,and 412), I wonder if that goofy offset cyclic system makes it more difficult to correct( or over correct) a student pilot on the controls in the right seat.The left cyclic,instead of being in the conventional position between the pilots legs, is at an angle and quite a bit higher.
One of the things we train for is to correct students while the cyclic is up in the air. Starting in CFI with an instructor all the way to internal recurrent training.
It is goofy, but you get used to it. If I’m flying, or have to take the controls from a student, I position the cyclic against my thigh again for better control authority. I never demo maneuvers with it in the air, safety and aircraft control comes first.
@@alwaysoutoftrim8649 Thanks for the reply.
I used to live in Garland, next to Rowlett Texas. Flew out of DFW for 11 years. Sad.
Back in the late 80s I was working working on my helicopter add-on. On my first lesson in the R22 me and the instructor were flying along and the machine started vibrating and the instructor took the cyclic and went aft then forward. This happened a couple of more times, the instructor explained that the blades were flapping and if you let it go unchecked that it could strike the tail boom and that was just straight and level flight. It was a design flaw that has since been overcome. I had some scary moments with the Robinson's and I personally refuse to fly in one. I ended up getting my training and rating in a Hughes 269. Unless they have changed their rules the FAA will not allow their people to do check rides in a Robinson.
They do. There is now an extra piece of FAA certification (SFAR 73) for flying a Robinson aircraft, to be hyper-aware of low G situations and to pull back on the cyclic to load the rotors, to avoid flutter which can damage the rotor mast, or indeed chop your own tail off. It's required of everyone who even takes the controls of a Robinson R22 or R44, so the pilots would have been certified. They may have been attempting another training manouver and accidentally exceeded design limitations in this way, perhaps the pilot routinely flew different aircraft and was less familiar with the Robinson, but I'd say it's hard to imagine it wasn't pilot error in this case.
Juan, look up the SFARS specific to the R-22 and R-44.
We got it on the MV-22 osprey when I worked on it in the marine corps. A real helicopter might be different, however when it happened to us it was often called a “swashplate overtilt”. Granted we did have sensors all over the place on the aircraft. If a pilot would ever push in power to much when landing in helicopter mode, sometimes we would get “flapping critical or caution high hot”. Which meant one of the rubber bearings within the hub cracked in half. It’s very interesting how a normal helicopter operates and it’s even more interesting how the osprey operates.
Rubber bearings? Ok warrior
I am not coordinated enough to fly helicopters. I'll stick with a Skyhawk. I understand that the Russian Hind helicopter is very prone to tail boom strikes during maneuvering. Good explanation of what may have happened with this incident.
It's surprising that if they know that abrupt movements cause the rotor to strike the tail, that they wouldn't change their design to prevent that. Surely it wouldn't be a difficult thing to implement. Maybe add tension on the controls so that you can't push them so quickly.
Another excellent explanation.
The maneuver they were doing i believe,, is also referred to as Settleing With Power.
In many cases, Mast Bumping will ressult in Main rotor separation.
This happened with Air Evac Lifeteam out of Vilonia, AR. A few years back.
I had been a mechanic on that aircraft earlier and the Flight Nurse was a friend.
I am a helicopter mechanic/pilot and this is always in the back of my mind.
Settling with Power is essentially the same thing as VRS - though this is widely debated and has caused god knows how many arguments and lost friendships over disagreements.
the true terminology that separates VRS/SWP is "Power Settling"
Settling With Power and VRS are the same thing, you have power applied and the rotor is losing its ability to keep the aircraft afloat, this is inherently due to VRS where the descent is over coming the velocity of the rotor downwash and the aircraft is recycling its own wake. VRS Occurs in a very specific region of hovering.
0:51 Juan, there is a aerodynamic phenomenon that occurs when the helicopter reaches Vne. As you increase collective and push forward on the cyclic to increase airspeed in flight, it moves the tail of the helicopter closer to the main rotor path as speed increases. One of the few situations in which a tail could be severed off of a Robinson.
When you encounter gusts of wind at higher airspeeds, its possible to enter a tail strike scenario with the main rotor because the flight procedure requires you to decrease airspeed when encountering strong winds at high airspeeds (aft on cyclic lower collective and left pedal to counter the torque of the main blades. The spin on this section of flight is if you are in a strong climb (however lower airspeeds) and encounter the gusts of wind it is possible to want to nose forward and enter low-g mast bump/rotor strike on the tail scenario which would explain the folded main rotors.
Strange things happen to helicopter airframes when stress tolerances are overloaded or you input the wrong control during a critical moment.
So, the nose would have a tendency to tuck under in a gust? Interesting. I know of a crash involving a Sikorsky S-76 that tucked its nose and chopped off the tail boom when a float bag accidentally inflated at significant airspeed.
It's called retreating blade stall. In this case the R44s airspeed was very low.
I always felt safe in the Hughes 300C.
The 3) bladed rotor system.
Keep up the good work. Thank you.
Correction: During Blade Coning the Rotor RPM speeds up instead of slowing down. Think about a figure skater bringing her arms in, the speed of the spin increases. It’s called the Law of Conservation of Angular Momentum.
Blades cone up during low-RPM as the centrifugal force that normally holds the blades "flat" is reduced, and the lift produced by the blades pulls them up.
@@ganthrithor that doesn’t make any sense. Have you seen the blades on a CH-47 chinook? When the blades are not turning the blades are drooped. The moment the RPM is increased, they rise. The faster it spins (higher rpm) the more it cones.
@@pnorva There's no lift when the helicopter is sitting flat-pitch on the ground. Blades going straight out to the sides perpendicular to the axis of rotation is not coning. Drooping is coning in reverse. When you pull pitch, the blades lift up and cone. When you pull pitch while decreasing RPM, they cone higher.
@@ganthrithor That’s not what I meant when I said coning. When you pull pitch, yes it cones because the weight of the helicopter is now affecting it. The load on the blades causes it to cone. If you pull aft cyclic during a high G maneuver, it adds even more load and cones. As it cones, the RPM speeds up not slows down. If the blades are unloaded, let’s say on a neg G maneuver, the blades will be flatter and RPM will decrease.
I too got my rotorcraft license (in an R-22) as an add on after about 1000 hours flying fixed wing aircraft. I had always wanted to fly a helicopter but my wife at the time forbade it. The first thing I did post divorce was take rotorcraft lessons. It was tough to master but SO much fun to fly once mastered. Anyway, I have not flown a helicoper in quite a while but have about 250 hours in the R-22. One thing that was drilled into my head regarding the R-22 (which also applies to the R-44) is to NEVER do any low g manuvers as this can easily be the result. In a fixed wing, pushing the nose over is a non-event so I had to completley change my way of thinking when in the R-22. Just my opinion but I think it very likely this is what occured here. It would take only mere seconds in a low g manuever to cause the main rotor to contact the boom. It would have happened so fast that the instructor would have had no chance to correct it.
It seems odd to me that the rotor did this. The rotor blade runs "parallel" to the boom, and if it were to torque enough to contact, the damage seen would be at more of an angle. This damage seems to run perpendicular to the boom. My first thought when I saw the video of the man carrying the tail section, I assumed the damage was caused by the drive shaft failing inside the boom at the point of the break.
What a tragic one. You point out what many of us have often thought, when looking at accident reports. (not referring to this one, since we don't know the specifics yet) Knowing "how to fly" an aircraft is not enough. Pilots should all be aware of the design limitations and all the quirks of their aircraft. (I also think that all pilots of fixed-wing aircraft should know their reduced-power, and power-off glide ratios. These things (and much more, of course) need to be part of all new pilots' education, and shouldn't be lost, just because people are rushing to fly right now.
It doesn't help that in the helicopter world, the vehicle that is popular as a trainer because it's cheap wasn't designed to be friendly or forgiving to pilots not experienced with its quirks, ie pilots in training.