How a Constant Speed Propeller Works | Commercial Pilot Training
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- เผยแพร่เมื่อ 8 ธ.ค. 2022
- Commercial Ground School is in session at flight-insight.com/commercial
A Constant Speed Propeller is able to change its blade angle to adjust to different loads so that it always stays at a desired RPM. It's great for efficiency of flight and is easier on the engine.
The engineers that came up with this system were geniuses.
Great explanation.
Totally agree. When I was researching it I found that it dates back to the 1800s and steam engines from Watt and Foucault. Really smart
What blows my mind is that this was developed only a couple years after the Wright brothers first flight. You'd think this was invented in like the 60s or something at the earliest.
The underlying negative feedback loop goes back to the earliest roots of automation, this is very fundamental stuff.
Can always tell too when someone gets their explanations from TH-cam University. They get the same things wrong, like "causing the shaft to speed back up". Not how it *actually* works but gotta start somewhere for the unenlightened.
Dan is outstanding with his explanations .... Flight School should adopt these programs to their PPL and Commercial schools....
The tutorial was great, I feel like it could be revised more to explain in detail with animations on a number of failures that could occur, it’s one thing to understand how things should work, but more in detail to understand what could happen upon a failure and to understand what to look for and interpret when your in that situation
The BEST explanation of a constant speed prop on TH-cam by far! This video just isn't for people who are getting their high-performance endorsement/commercial. I already have my high-performance endorsement and I still learned from this video. Somebody needs to contract this guy to make videos for large flight schools.
A constant speed prop is part of the complex endorsement, the HP is for engines rated at greater than 200 hp. -) Happy flying
I’m aware. However, some aircraft that fall under high performance have a constant speed propellor. For example, the airplane I got my high performance endorsement in was a 1972 Cessna 172, and it had a constant speed prop on it
@@matthewchapman3507 sure, in fact most HP planes have a CS prop, I was just referencing the use of the HP endorsement as it pertained to the constant speed prop, just nitpicking as a CFI, that's all, don't mean anything bad by it.
I gotcha! No worries, I didn’t interpret it that way.
i spent 2.5 years in the US Navy rebuilding and testing prop governors at AMD Component Repair Dep. NAS Norfolk, VA in the 1960's. This video is spot on, very informative, and accurate.
I believe many people are confused by the term manifold pressure since it seems to suggest that there is positive pressure in the manifold, when in reality anything below atmospheric pressure of ~30 inches is negative (vacuum) pressure. If you've ever hooked a vacuum gauge to an engine, you're just looking at the same measurement in reverse. You could make a clear gauge with a scale for vacuum pressure on one side and manifold pressure on the other. With the gauge unhooked the needle will point to zero on the vac side, while on the pressure (MAP) side it will read ~30 inches. If you hook it to a pump and pull a full vacuum, the vac side will read ~30 and the MAP side will read zero. Directly inverse.
Correspondingly, if you hook it to an engine, with the engine off the vacuum side will point to zero and the MAP side will read ~30. When you start the engine, you will develop a vacuum in the intake from the air being drawn into the engine, which will cause the vac reading to increase and the MAP reading to decrease a like amount. You will have the highest vacuum/lowest MAP reading at idle. As you increase throttle, vacuum pressure will decrease, and manifold pressure will increase.
Side note: When you see specifications for planes such as WWII fighters which have manifold pressures higher than 30, it's b/c they are supercharged, and their engines have air forced into them.
There is NO WAY to come from this video without a working understanding of the constant speed prop. Thank you!
Challenge accepted
@@LargetalonsI was about to say, I can fuck up and misunderstand ANYTHING, bro!
Good heavens. I just finished A&P school, and this is probably the best explainer video I have seen on aviation mechanics.
Hands down best video on this topic. Finally wrapped my head around this concept because of this video.
Thank you so much for this!! This is by far the best explanation of a constant speed prop. The visual aid helps so much as well. You’re the best!!
Perfect timing for these videos, about to do my checkride soon 🙏
This explanation is gold. The comparison with the bike made me understand the difference in pitch of the propeller, GREAT!! Thanks.
Keep the prop on top will now always stick with me. Excellent video!
Extremely helpful. I’m in A&P school and working on my powerplant rating. This was much needed 👍🏾
Thanks for making me understand what's happening in detail when flying in a prop plane - take care!
Always the best and most informative information! Very much appreciated!
You are always posting exactly the stuff I’m working on.
Working on my Complex Aircraft Endorsement currently; this video is fantastic- thank you!
As BOTH an AME and Pilot - this is a GREAT simple explanation on how the system works.....You could quickly bring this up a level with reference to Turboprop aircraft as well!
As always the best explanations in aviation.... thanks.
What a great video! Accurate and well-explained.
Great info on comparing to the multi engine with feathering. I only few multi engine with constant speed and learning to fly the 207 now, makes a lot more sense how it’s different with the oil pressure in the propeller now. Thanks!
i have not understood this system at all until i watched this video, all the others i watched either overcomplicated it, or didn’t explain it very well. thank you so much!
You are a sky god. Best explanation and illustration I've seen.
Excellent content. Thank you!
Excellent video as always. Look forward to the follow up
very good explanation. extra thanks showing the flyweight mechanism in actual assembly!
Great job sir. Thank you!
The best overview of the Constant Speed Prop I’ve come across - thank you for the great and clear walkthrough. I’ve never been mechanically minded, so I have to watch this a few times for it to all sink in, but it’s a fantastic description 👍👍👍
I needed this for my Powerplants test/certificate. Barely passed with 72 on mock test at Baker's. Thanks for the visuals.
Def the best overview out there...
Fantastic, thank you!
Thanks! Great explanation!
This channel is so underrated...
Amazing explanation. Never really understood it up until now
outstanding explanations ! YOUR THE BEST
Excellent explanation thx. It makes me clearly understand why RPM should not be lower than the manifold pression too.
I had to add this to my new Arrow Playlist! Great Job. My life just got more complex..
4:19 - Ideally, instantaneously. In reality, this feedback, does take some time (lag), and it takes a bit of engineering to keep it stabile, and performance acceptable.
Great explanation! Waiting for next videos.
THANK YOU omg...trying to learn this on paper when you have never even sat in an airplane with a blue MP leaver was agony. This helped so so much. I don't understand why ground schools (the few in Canada there are) refused to spend time and money on visual aid like this.
An excellent video.
Wow, wonderful explanation 👏
Good video. From a CFI and A&P/IA, may I make one suggestion. You mentioned that the oil pressure is supplied by the engine driven pump. Actually, the engine pump does get the oil to the governor, but nominal engine oil pressure (say about 75-80psi) is not near enough to actuate a constant speed prop under air loads. An important component of the governor is it’s own internal pump, which kicks the oil pressure well above 200psi. Just like the engine oil system, the governor’s oil pump is a twin-gear type pump and has its own pressure-relief valve. Still, as you said, a loss of engine oil pressure will create a starvation of oil to the governor, which will keep a single engine prop to maintain maximum fine-pitch blade angle. Cheers!
This makes sense as to why “over stress” is an important consideration when we’re already talking about base operating oil pressures orders of magnitude above engine press.
CFI/CFII next please! Would absolutely buy from you for my CFI! Absolutely love your work!
incredible explanation i love this channel
I’ll give this a 9/10. There’s one key piece omitted: The high MP and low prop RPM condition isn’t just bad for the prop (which it is), but also has the potential for causing massive damage to the engine itself, especially in the rod bearings. There’s also potential for triggering abnormal combustion of the fuel-air mix. All bad and definitely to be avoided. Otherwise, very nicely done! Gene, ATP A320 FO at major US airline.
Really well explained ! Made so simple ✌️
That bike gear analogy 🤯
Have to credit my old DPE Frank Phillips for that one
I compare these videos to the Cessna Pilot slide show series I studied in 1984 for my PPL and Instrument. It’s a whole different aviation world on so many levels but since getting back into flying after 38 years, these videos really help. Many thanks.
Greatr video! Thanks!
Every time I'm not sure of something in my flying, it seems like there is always a flight insight video there to explain it clearly. Keep up the great work!
Outstanding presentation
Excellent illustration, many thanks for this.
Make the next video about settings. This is the most informative avation channel on TH-cam
This video is a gift from God
This is a great video, but what you failed to mention is that the prop taking a big bite is required at altitude because of lower air density.
However: 10 out of 10. This is the content I come to TH-cam for.
epic, now waiting for part 2!
My ground school is VERY verbose and teaches largely through slideshows and whiteboard drawings. Seeing things in an animation helped so much
Very detailed ! Thank you for the content👍🏽 perhaps post a video on part 135 oral/flight.
Wonderful job as always! I'm very thankful for these videos and your ability to teach.
This is so cool! Who even thought if designing this? That's so clever!
en.wikipedia.org/wiki/Variable-pitch_propeller_(aeronautics)#History
The best explanation I've seen on the internet! Great job!
thanks I didn't know how the constant speed propeller worked but do now
also with this engine type, the pilot leans out the fuel for better range did know that,
my father used to fly me in a Piper Cherokee, young at the time but have learn't about
over the years, he says it had no CSP.
There are ELECTRIC constant speed props too. The old C-130 uses them STILL on it's turbo-props.
Some good information here but the propeller governor and flyweights are not in the prop spinner assembly. It is generally mounted on the left side of the engine below the front cylinder.
7:40 - Actually high MP in combination with low RPM mainly can cause engine knocking or worse, pre-ignition.
Hey Dan. Commented and Liked
Your commercial videos on TH-cam have made you a leading contender for my commercial rating (I’m almost done with instrument). I used a well-known online school for private and loved it. Used it again for instrument and found it lacking. So I’m shopping around now!
Glad we're in the running!
Dude, whoever or whatever committee designed this was absolutely BRILLIANT. I understand that all technology ultimately comes about through evolution and the effort of hundreds, even thousands of people. But whoever landed on this particular solution…wow…
Very cool
How to study to my theory aviation exams: wtch these videos! Thank you for the good work!
Interesting. The type of operation this is supposed to not like is the type of operation the engine would love for efficiency
Great video!!! I can already tell this is going to help me out with my Bachelors of Aviation. Thanks! Looking forward to the next video discussing settings and how/why they work in the way they do.
Excellent video, I'd love to see you make one for feathering props as well but I'm glad you touched on it.
We really want to do a multiengine series in the not so distant future. Feathering will certainly be part of it.
Great 😊
When I got into a 182, my flight instructor said that I would never want to fly a 172 again. He was bloody right.
Why? Can you elaborate?
@kcaz94 The room inside it, the speed of the airplane, and with the extended range 80 gallon fuel tank, the airplane will go further than your bladder ever will.
Even though a 172 has 4 seats, you'll be a fool to try and take off with them all occupied. Especially in the summer. A 182, no problem. Unless you're try to get 3 linebackers off the ground. )
The fly weights for the governor remind me of the gentleman who was constructing a anti gravity machine with flywheels, and gyroscopes
Many thanks from a rusty CPL!
I've been reading the AMT for hours trying to wrap my head around the full function of the governor, I should've just watched 9 minutes of a FlightInsight video on the same topic.
Excellent explanation! One time during training, I was out on a solo flight to a practice area. After takeoff and while climbing out, I changed the prop setting but the RPM didn't change. I played around with it for a minute or two, but still no change. It was a winter day, so the likely explanation was that something in the governor mechanism was too cold, but it could also have been due to an oil leak, as the video mentions. Even thought the oil pressure gauge was steady, I decided to return rather than take the chance that it was nothing. On the ground there was no evidence of an oil leak, but it was better to find out there rather than at 3,000 feet and miles from a runway! 😀
Great explanation Dan. I miss the blue knob.
Me too. Though in the cardinal now ours is black, haha
@@flightinsight9111 I'd sneak in in the dark of the night and paint it prop knob blue.
Flyweight governors are awesome. When I did my first conversion onto a PT6 driven type, trying to understand the FCU system sent me in circles
You can thank James Watt for that!
This is a very helpful video. I’m starting my Multi Add-On, and didn’t have the best understanding of a Constant Speed Prop. Ever since the FAA allowed commercial applicants to substitute TAA time for complex time, I skimmed over constant speed props with not the best understanding.
very well done!
Excellent instructional material. Probably the best I've found. I read some articles promoting running an engine over square (higher MP and lower RPM) in cruise flight. What are your thoughts? Keep up the great videos!
We get into this in the course in depth, but there is no real reason to avoid a so-called "over-square" condition with higher MP than RPM. MP and RPM use completely different units (inches of pressure versus revolutions) so it's purely coincidental that the numbers themselves are even close to each other. Consider that in metric, with millibars, the idea of having the MP and RPM equal is meaningless. So yes, agree with the articles, and most POHs will have recommended settings that have the MP higher than RPM.
@@flightinsight9111 Just as long as you keep it above the placarded RPM for any given MP!
I feel like this does a great job explaining the mechanism of the constant-speed prop, but some more "why" or what's happening aerodynamically with the prop might be beneficial: isn't this basically a thing to compensate for changes in airspeed (rather than aircraft pitch attitude as described)? I don't fly planes, but it seems similar to the concept of induced flow in helicopter rotors: the faster the air comes in from ahead of the prop, the lower the prop's angle of attack becomes (assuming a fixed-pitch), so the more RPM is required to restore AOA (and then once RPM is maxed-out, the faster you go, the lower the blade AOA becomes until you don't make thrust anymore). It seems like the constant speed prop is there to allow you to run reduced engine RPM for cruise flight while maintaining adequate blade AOA at higher airspeeds by giving you a blade pitch angle increase. I assume at very high speeds you run into the same problem we do with induced flow: the more pitch angle you add to the blades to compensate for increased forward speed (even if blade AOA stays constant), the less thrust component you get from the total aerodynamic force on the blades, while drag on the engine continues to increase?
Testing for Instrument 20 Jan and then I’m getting this course.
Nice video and basic explanation. However, regarding the power settings, if running a lot of MP with low prop RPM is more likely to be tough on the cylinders/engine. I doubt that the prop cares. But most GA engines are so low performance I doubt that there is much to worry about (unless with a turbo perhaps). Also, running for extended periods of time in cruise at low RPM was probably never tested by the manufacturers and they are probably more worried about propeller/engine harmonics, that is any resonances that may develop, than anything else. Thank you for the video, though.
Only one question, from the beginning of the video you combine the AOA with the pitch angle. These are not the same thing. Since the plane will be moving the AOA of the prop changes with the airplane's speed. So you want the low AOA on takeoff, but then as you go faster you have to increase the pitch to maintain a good AOA with the new speed.
7:12 OK this is completely wrong. The issue is not that the propeller or spring mechanism are being stressed.
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. The engineers who created those tables and charts know about all this stuff.
The Beaver has a pratt whitney R985 Radial
cruise is 1900RPM 29 manifold
climb 2000rpm 30manifold
prop on top doesnt apply everywhere?
I thought it was a viscous coupling similar to center shaft of a Subaru or like a automotive cooling fan clutch that would engage more when he did respond faster? So you were saying that this angle changes. I thought it was possible for the angles of the blades to change like on a helicopter
Nice! Mechanical negative feedback loops
How do you go about determining how to structure the information when youre making a video like this? I am still trying to figure out how to flow through information in a more logical way when I am explaining things to students. I use your videos as a guide for myself all the time to review before lessons.
Fantastic work done and so easy to understand. what software is use to illustrate this video and some of your other videos.
by FAR the best explanation video i’ve found regarding constant speed prop operation. thank you!
there is one question i have that wasn’t answered tho, and perhaps you can help me find the answer. what “manifold” is the manifold pressure gauge referring to? if, for example, at full power we’re sitting at 24inHg, is that referring to intake manifold vacuum? i’m having a hard time with that one because typically high manifold vacuum would correspond with the throttle plate being closed, no wide open. any insight?
High manifold vacuum = LOW manifold pressure
Though I'm not too sure how applicable this is to the average CPL seeking pilot, I believe most of the commercial manuevers for the then PTS were based on flying a complex airplane (with a constant speed controllable prop) allowing for executing manuever without rpm/power change that have climbs and descents (say for example the lazy 8s and 8s of pylons) much easier than what many applicants go through now with a fixed pitch prop.
Ingenious, but more moving parts.
How fast do you want to go?
🔊
I would think that on newer airplanes the mechanical governors could be replaced with electronic prop pitch control. The current engine speed and the desired engine speed commanded by the pilot are fed into a computer, which then automatically controls the oil pressure going to the prop hub to control the prop pitch. A system like that could even calculate the best prop pitch and best engine speed for the current flight conditions without any input from the pilot at all. Sort of like what autopilot does.
This does already exist. This is what full Fadec does on newer aircraft. I believe cirrus have this as well as some newer diamond aircraft. There is no “Blue” lever just one “power” lever.
and maybe better not use constant engine speed, just like car using high gear and low engine RPM to save fuel, with this set high blade angle and lower engine RPM would probably save some fuel too. When accelerating at full power the engine run at max power RPM constantly, and the blade angle changes gradually like car CVT transmission, so the blade angle maintains for the maximum efficiency.
Do high performance aircraft also have a co-pilot valve?