How to Fly with a Constant Speed Prop | Transition to Complex Aircraft
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- Опубліковано 3 чер 2024
- Here are the basics we teach all pilots who are new to operating an aircraft with a constant speed prop.
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My favorite flight instructor reminded me on multiple occasions that most engine failures/issues occur on the first reduction of power. I thought that was cool you included that here.
Wouldn't the first reduction of power be right after runup?
@@zachansen8293 my instructor mentioned this in context of power reduction following a full power take off in light SEL aircraft.
The engine has no load as it rests on the ground. At lift off it now has the full load and runs free for seconds after power is reduced. This is where bearing tolerance is exhibited and why one wants some altitude prior to power reduction,a safe distance above the ground in the event of power loss.@@zachansen8293
Got to fly a 182 Turbo Retractable yesterday for the first time, so this video helped bring all the concepts together. Thank you!
I transitioned from a C172M to a C172XP with a constant speed prop. It sounded more complex than it actually is. You get it all together really quickly and easily.
This is one of the few tutorials that actually explains how the 3 engine controls should be used.
GUMPICSS: gas, undercarriage, mixture, prop, instruments, carb heat, switches and seat belts. ( Some items may not apply).
How many nm from the airport do you start the crosscheck?
@@riod43 when you get ready to descend, you use your decent checklist. With simple airplane sometimes it is only three obvious items like reduce power enrich mixture and a target airspeed. Usually if I am VFR and I am in the pattern I start my GUMPICSS check on downwind. If I’m flying on instruments once I am within 3 miles of my final approach fix inbound and I am stabilized I can run through the check one final time. Then when I cross the fix, I pitch to my dissent rate on the VSI and I adjust power as needed to maintain desired air speed. Sounds backwards from the way you learn it, but when you are instruments, you have to pitch to the glideslope, not the airspeed indicator. Profile flight is the most consistent and result in near perfect landings every time.
Please send gum pics
What about cowel flaps? I’m partial to BCCGUMPS: boost pump, carb heat, cowel flaps, gas(tank selector), undercarriage, mix, prop/power, switches/seatbelts
I was always taught to cycle the prop 3 times: 1. Rpms go down. 2. Manifold pressure goes up. 3. No oil on the cowling. And by doing it 3 times it "cycles" oil through the prop. Now you are all warmed up!
Yes that's correct, I was taught the same!
Hands-down, these two videos on constant speed propeller of yours are the best out there. I’m about to purchase an airplane that has that scary blue lever. This has helped immensely. Question: what are the advantages or disadvantages of the two different prop options for a given power setting. 65% in your example.
Decided to start renting a C172RG, this video definitely helped in getting the complex endorsement. Thanks for making this!
Extremely well explained video. Learnt a lot, thanks.
Wow this video could not have been uploaded at a more perfect time. I just passed my instrument checkride and I'm preparing for the commercial written!
My point of view and method for remembering the correct actions is like this: For me, the throttle is the analog of the accelerator pedal of my car. The prop control is the dearbox of my car. If I have to drive up a hill (climb in the airplane) I first select a lower gear (prop control forward) and then press the accelerator pedal (throttle). If I am rolling down the hill I usually do not change gear but just release the accelerator pedal.
That makes sense!
Your explanation and quality of videos are amazing. Why I couldn’t find these more earlier!
Yet another terrific video Dan! It was definitely more interesting than I expected on what “seems” like such a simple topic. Thx
I love all of your videos, and this video could not have been more perfectly times because I'm starting my commercial/multi-engine!
I'll be flying the PA-44-180 which has a full-feathering prop, so lower pressure increases prop pitch instead of high pressure in the Arrow.
Best video I've seen on this subject. Thank you 👍
best video I've ever seen on Constant Speed operations.
Great video! Thank you for uploading this.
Where were you when I was was taking my training? This stuff is so much more understandable.. Another good video.
Thanks for the schooling. Excellent video.
Great explanation. Thanks Man.
How have I missed this channel? Invaluable.
As usual, you explanations and graphics are top rate. Taking up flying after 25 years off and your content has been very helpful. Thank you!
Excellent video-well done.
Fantastic video... like the previous ones! Keep up the great work...
Good video, you caught everything.
Good content, very well presented. Thx
Was there another video before this one that would help me understand how the constant speed prop works?
Very good! Thank you!
good work
Terrific content on this channel, really enjoy your uploads. Keep up the good work!
i live for these flight sim explanations
Love this!!!
Gas should include fuel pump on for low wing aircraft that I have flown, great video
Me this morning: I need to find out how a constant speed prop works
This is the first video recommended by UA-cam when I logged on 😂
What about teaching spin recovery ? I did my first and last spin in 1968 when I got my PPL.
It was in a tandem fabric airplane with a WW2 pilot instructor from Slatington PA airport.
We were at 2500 feet and he said let's go up to 3,000 feet and do a spin.
Always refer to AFM and perf charts and dump the "pilots self made assumptions" - Hey even AFM are ways off for some of the Piper Arrows I think, most notably for the Turbo Arrow IV.
Thank you for the slow and calm narration. Not sure why most av guys yell. Must be the hearing loss from jet noise.
This is the video I've been waiting for. I got my complex endorsement nearly 20 years ago but the ideas never really 'stuck' - thank you for this.
great video + you sound like Jack Black :D
Nice tutorial, well done. If you get the same power (65%) from 24.7 MAP @ 2200 RPM vs 22.8 MAP @ 2500 at 4000', how do you choose between those two settings?
Much quieter at 2200
I like to use the lowest RPM and highest MP that will give me the desired power. Lower RPM results in less noise, lower fuel consumption, and fewer hours on the tach.
The lower RPM. Quieter, less frictional loss, better volumetric efficiency, and reduced EGT.
And remember, it's not really just two options. That's just a simplification for tabular presentation. In reality, it's an envelope.
wonder how it works on a turbo when the pressure is likely always higher than the prop rpm
Flying multinengine airplanes and before landing running the props to full foward when operating outside of the governing range.
You should of used the A2A Comanche. Way more realistic engine behavior than any other GA aircraft out there.
Does higher manifold pressure mean more torque/thrust?
Yes, higher manifold pressure means more power while the engine is running, so more torque, though piston engines don't have a torque gauge.
The Map pressure is very important flying helicopters
I'm having a hard time wrapping my head around the idea that at idle, vac is low. In a car, vac is high until you open the throttle. Is the gauge behind the throttle butterfly or before?
Coming from a car guy background I had the same issue as you regarding this. Car gauges read PSIG thats the absolute measured air pressure plus a 14.7 PSI offset for atmospheric pressure. So if its dropping to less than 14.7 PSI pressure in the manifold the gauge will start reading increaseing higer vacuum numbers with a theoretical maximum of 14.7 under heavy engine braking. If the manifold pressure is higher than 14.7 PSI then your turbo/supercharger is producing more air than your engine can draw in naturally and we start to experiance forced induction (boost).
Plane guages read PSIA, or absoloute pressure with no offset. So with the engine off it reads ambient airpressure (about 14.7 PSI or 29.97 or 1013 depending on who you ask!). When you start the engine in a plane, your gauge will drop in pressure, because with the throttle closed and the engine running you are creating a partial vacuum in the manifold. This is opposite what you would see in a car. Then as you open the throttle in the plane, more and more air is able to natually flow into the manifold until its basically at ambient pressure or close to it. So in this case, as you open the throttle, the pressure reading increases.
Google PSIA VS PSIG for some graphics which help explain this a lot more. But basically in the vacuum range of engine operation, cars and plane guages work in opposite directions even though what the engine is doing is identical. Its simply a different way of displaying the data.
If you are thinking about it in a boosted context, the plane method works better in my opinion. I.E, going from 25 to 35 on your manifold pressure makes logical sense, higher number = more air & power. In a car this would read XX mm/hg vac to XX PSI boost, why use two different units for what is really just a linear change in air pressure?
I hope this helps I have had to break a lot bad habits when it comes to thinking about manifold pressure moving from cars to planes!
I don't want to be picky and I know youre using a sim but does the concept of overspeeding the prop not apply here? on take off and on climb, the rpm was past the red. Am I missing something regarding this? honest question
Past the red it short but not sustained periods generally in climb when need high power, but never in cruise
Depends on the aircraft - the two I've flown, one is full power until safe altitude (even if past redline) then reduce to 2500 for the rest of the climb. The other specifies max 2400 for take-off which requires a few cm of adjustment to keep it below redline.
You glossed over something very important at 12:00. A lot of pilots keep the prop back until on ahort final. The problem with that is if you lose the engine, there may be very little pitch adjustment with which to stretch the glide. Prop forward abeam the numbers on downwind gives you a LOT of glide stretching in the event of a power loss.
I don't understand your comment. Prop forward increases the drag, no? Why would it stretch the glide?
Glide performance increases as the blade is coarsened. You’ve got it the wrong way around. The reason we are taught to increase the prop to full fine before landing is to facilitate a possible go around.
@@z120p I don’t think I had it the wrong way around. Your first comment is very confusing but I think I understand what you meant. Either way, I think sticking to the POH and GUMPS is the best advise.
@@z120pThis is correct, to stretch glide pull the prop out to coarsen prop pitch.
@@Virtualmix im not the original poster, and I wasn’t responding to your comment at all. I was responding to the original post that said that glide performance is better with fine pitch.
OK I’m probably going to get a dozen or more opinions on this question. You look in the POH and you decide that you’re going to fly with 65% power. There is a table that gives you a bunch of manifold, pressure and rpm combinations at different altitudes. OK, let’s say you decide you’re gonna fly at 6000 feet. The POH gives me beautiful pressure and rpm at that altitude starting with 2200 RPM, 2300 RPM, 2400 RPM at 2500 RPM. Each one of these speeds has a respective manifold pressure setting. Each one is supposed to give you 65% power. Which rpm dental pressure combination is going to give you the best performance, the best speed, the best fuel burden, and the least amount of engine wear? Is it a higher manifold, pressure with a slower rpm, or a lower manifold pressure with a higher rpm? I also noticed a POH’s does not give you specific airspeed for every combination. It just gives you air speed at brake horsepower.
The fact your using 65% power at 6000ft indicated results in a slower speed at a fuel saving using the POH settings for that altitude ie go further for time not distance depending on wind direction, but there's a difference between indicated altitude, while the engine/prop should be adjusted on the Density Altitude ie not the same!
@@TheCruizer21 I guess you’re not following me or I’m not making the question clear. At any given altitude, the POH gives you different power settings with different RPMs. It’s still represents the amount of brake horse power for any given setting. What is the determining factor that would let you run the prop at 2300 versus 2400? in other words, what is the benefit of the slowest RPM with the highest pitch versus a lower power setting with a finer pitch. I would think with a constant speed prop you would want the lowest RPM to minimize wear and tear while still being able to move the airplane through the air at the same speed for that altitude.
@@aviatortrucker6285It gives you two because it's defining an envelope related to power. But there are other considerations that favor the lower RPM: less noise, less frictional loss, better volumetric efficiency, and lower EGT.
3:10 I guess testing it with todays LED lights wouldn't deflect the needle much.
lower rpm less stress on engine, only thing missed here is how/when to lean
7:58 Wrong. It's not about overstressing the prop, it's about generating too much pressure (and therefore temperature) in the cylinders.
The problem with extreme settings of high MP and low RPM is higher intracylinder pressures (ICP) and a corresponding rise in cylinder head temperatures (CHT). You're feeding the engine a more dense fuel/air charge while simultaneously slowing down the power stroke. Peak pressures increase in magnitude, and occur closer to top dead center. Near TDC the piston is driving directly down into the crankshaft and you have lost all mechanical advantage; you're putting excessive force loads on these engine components and asking them to do way too much work. Instead of a bullet (piston) being smoothly accelerated down the rifle barrel (cylinder) you have created a pipe bomb. The real stress is inside the cylinder, on the piston and connecting rod. The danger is pushing these cylinder components to their temperature limits, resulting in detonation.
Extremes of very low MP and very high RPM are also bad. In this case there is insufficient positive pressure on the piston to keep it seated, allowing piston ring "flutter", leading to scraping and scouring of the cylinder walls.
The bottom line is do what the manual says, not what some clueless 19 yo CFI tells you. (ie oversquared old wives tale BS) The engineers who created those tables and charts know about all this stuff.
I've never flown a constant speed prop. How do people cruise in these things? Do you always have your POH out to reference the cruise numbers? What happens if you don't follow the recommended numbers? Do you have your favorite numbers just memorized?
Me and a buddy just closed on a new (to us) Diamond DA40-180, so this is very pertinent. Also, easier to get my head around this concept than the VOR concepts in your IR module. Gotta go back a third time on that one, lol. Not to suggest that your IR stuff isn't great -- it is. I am just a little thick sometimes.
Thanks for the video however I'd like to have a clarification on the mixture.
Let's assume I'm cruising at 7000' and need to climb 9000'. Won't the mixture set to full rich degrade the performance of the engine?
What would be the consequence of doing right to the left, i mean prop full forward then throttle full without touch the mixture especially during a climb.
Cheers
The answer is it depends. Full rich in a climb is more likely to apply with a turbocharged airplane. In your example my airplane would already be below 65 percent power in which case you can use any power/mixture setting you want without fear of damaging the engine. The important thing to pay attention to in that scenario is CHTs.
@@utah20gflyer76 Thank you, I really appreciate this clarification 🙏
You forgot engine start? youre video started with the engine running
I’m still trying to find where the key goes to start it 🤣
wow, only 0.1 hours on the hobbs!
How do you get different aircraft types and models in x-plane? Checked my version and I’m not seeing this one
Nobody ever explains how you chose what RPM to set. So for 65% power, you can operate at 2200 or 2500 rpm. Or anything in between, interpolating MP to suit. Why would you chose one or the other? Presumable 65% power gives you the same (ish) speed whatever you chose? Are some RPMs more fuel efficient than others? Does it matter what height you're at? How do you chose???
Yes you have a choice of rpms that provide the same brake or shaft horsepower. Power is torque times rpm. Pistons do not generally have a torque gauge so MAP is used as a proxy.
The engine will be most efficient around its best torque rpm. However, the prop has its own efficiency curve and the airplane has its drag curve. The most economic cruise rpm depends on how the airplane designer has matched them all up. Hence the only generic answer is to use the performance tables of your POH to choose the best rpm.
Any given power such as 65% is the theoretical percentage of rated engine power at the crank, or % of rated bhp. As such, although it will give similar airspeed in the cruise, it will not be exactly so because the prop efficiency (hence thrust horsepower) varies with both rpm and airspeed.
There is a rational method to choose the most efficient cruise altitude for a piston. You decide the percentage power you wish to cruise at, for instance 75% for a fast cruise or 55% for range. The concept is to climb to the altitude where full throttle will only just maintain the required MAP (critical altitude). Throttling losses are minimum at this altitude. Obviously you need some reserve power for manoeuvre so you will choose no higher than the next lowest cruising level. You will effectively be at operational ceiling for the cruise power desired.
@@XPLAlN You say "Hence the only generic answer is to use the performance tables of your POH to choose the best rpm." But how? Those tables only tell me which options are available, not which are better.
@@matthewwilliams2128 the POH may provide the range by % power and rpm, in which case you just choose the best for range. The range tends to go up as rpm goes down. If the POH does not specify, then the best range is likely to occur at the lowest rpm (that is both approved and achievable) for the % power you intend to use.
Squeaking parachute dropping lol
Don't quite understand what you mean by 'prop on top,? On top of what? This stuff does my head in 😅
Prop always forward compared to throttle.
Why do you have to check the fuel tank so much? Does the knob easily jump out of position?
I could see if you are running low on a tank just before landing so you won't run out of gas.
Are you just burning in GUMPS in your brain? I can see it only takes seconds to do GUMPS and youd hate to skin over something that was not set after doing your first GUMPS check.
Not a pilot, but I like watching the videos.
thanks
Full Gumps Check
Gas - on fullest tank
Undercarriage - three green down and locked
Mixture - full rich
Prop - full forward
Pump - fuel pump on
Seats - belts on
switches - lights all on
Just bought into a partnership on an Arrow. It has the same orange interior as yours, just uglier. Great plane but I’m changing the interior asap. Thanks for the vid, it seems I’m flying it correctly. Instrument rating next.
One thing to remember, is that if you fly with the manifold pressure higher than the RPM, even if it says, you can do so in the POH, many times, due to harmonics the plane will develop a nasty vibration or rumble. This could be compared to driving your car with a manual transmission and you are in a higher gear and you step on the gas pedal abruptly. Instead of increasing speed right away, the car will vibrate and make rumbling sounds. As a general rule, it is probably most safe to get the same percent horsepower by getting as close to square as possible. That is in the example of 24.7 manifold pressure at 2200 RPM yields 65% power. It probably has a listing for 23 square. The noise level will be higher like a fixed pitch propeller, but it is easier on the engine and the propeller. It may also keep a few rivets from vibrating loose.
He specifically addressed this myth in the video. This is the first time I've heard "harmonics" as the justification for the myth, though. Most pilots who believe this think it's to "avoid stressing the engine" or something.
So you know better than the manufacturer? Just fly ANY aircraft the way the manufacturer recommends and not the way some "amateur" thinks is best.
So what would happen if your manifold gauge was calibrated in millibars instead of inches of mercury? Now what?
@@dragoclarke9497 I agree you need to always consult the POH as the primary source. But consider that the engineers wrote what they thought was best practice when this plane was brand new with comparitivley few hours flown on the design. The author is now writing with, for all you know, decades of experience flying constant speed props. Its worth considering that best practises can change as millions of combined flight hours are analysed on a particular model.
A good example can be seen in AOPA's most recent video where a pilot took off on a high density altitude day. All passengers were weighed, all preflight calcs correctly performed, all run ups were carried out. But the plane DID NOT perform as described under the conditions as stated in the POH. The plane continually stalled after takeoff and eventually crashed into a residential area, killing some and injuring others. This is one clear example where a POH was actually a contributing factor to aviation fatalities. Its worth noting there were other contributing factors as well like most aviation accidents.
One other example that many instructors teach their students which is not in the POH but does seem to work is the trick of 'hopping' an obsticle in the event of a forced landing. The POH will state a clean best glide speed and tell you to stick to that. But real life experience shows that if you pop in extra flaps right before you are about to touch down into a fence or just clip a tree line, you will momentarily rise and then decend more steeply after you clear the obsticle. You wont find this in a POH, but it does seem to work. Also check out 'free pilot training' on UA-cam for a video where he shows that you can climb out even steeper than the Vx stated in the POH by using a ground effect 'zoom' climb. Again, this works well for clearing runway obsticles and you wont find it in most POH's.
In aviation you need always need to remain humble that others may know something you dont know. And that even the engineers who wrote the POH probably have not delivered a 100% perfect document the first time it was handed down at the beginning of an aircrafts life. In the commercial aviation sector (I.E Boeing, Airbus, etc) we see constant updates to operating and maintenance documents through the life of the aircraft. Unfortunately, this does not seem to happen to the same extent in GA planes.
Be kind and remember as pilots we remain life-long students of aviation 🙂
@@HiddenWindshield I speak from experience. I flew in arrow once with high manifold, pressure and low rpm. The airplane vibrated badly. All I can say is try it for yourself. One more thing to consider is generally your true airspeed will be slightly slower, and your fuel burn will be slightly higher with a higher manifold, pressure and lower RPM. I specifically speaking about a naturally aspirated engine.
I could not hear what you were saying over that VSI yelling around 6-7min mark
I don't want to fly a plane with those three colored push/pull rods for the engine. Give me a throttle that says "more power/less power" and let the computer figure out the rest. This isn't 1950.
Roll and status of the Captain and the First Officer, approach without briefing which had increased workload, combined with the notorious circling approach had led to this disaster.
more ads ... aargh
Wait now? College Park Maryland? Figures?
Yeah I used to live there. My husband worked there. Both as a cop and as an air traffic controller after the military. And I was in broadcasting. All the traffic planes flew out of College Park. That's the civilian class airport for Washington DC's suburbs. But make sure you don't make the mistake of trying to fly over the White House. It won't go well.
So is all very funny. Say hello to the numerous, Dave Johnson's I all know. I know so many Dave Johnson's. They all seem to live around Washington DC for reasons unknown? I know 2 or 3 of them. I have lost track. Of how many Dave Johnson friends I have? It can be very confusing. Some are drummers, carpenters, pilots, sports puppies. All walks of, wasted life. To be sure. But not me! Nope. I am simply a natural born loser. That I don't have to work at and need no help with. You will see.
Now when in doubt do as the Romans did. Love a person of the same sex as you. To prove you know how to love without attachments.
We can work this out in reverse. Worrying not to.
RemyRAD