What is P-FACTOR? | The Asymmetric Blade Effect
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- Опубліковано 30 вер 2024
- P-factor, also known as Asymmetric Blade Effect is an aerodynamic force that causes the propeller's centre of thrust to shift off-centre. Find out how it works in this video.
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#flightclub #pfactor #assymetricbladeeffect
Best verbal and visual description of P Factor I’ve seen. Excellent video.
Glad you liked it!
I think I could learn a thing or two from this channel. Thank you for being so short and clear.
Happy to help!
Ahh! Thank you!
Any time
more right r u d d e r
This content is clear and useful. Thank you very much! I really appreciate the new ones
I had to watch it a couple times to fully grasp the concept. It’s short, clear, and concise.
great explaination, I've always wondered about this effect!
Thank you! Cheers!
What about gyroscopic precession? Wouldn’t the increased force be applied 90 degrees later in the rotation?
Gyroscopic precession is only a factor when changing pitch or yaw (but you never notice it during yawing moments). Once you're on-pitch gyroscopic precession ceases. For example consider a helicopter going so impossibly fast that it's got retreating blade stall. Will the helicopter roll to the side of the stalled retreating blade? NO! It will pitch UP due to gyroscopic precession.
As an RC model plane builder and pilot in the 80’s I remember we countered this effect by building in the engine with some degrees of pitch and yaw
That's interesting that even at such small scale this effect is evident.
@@flightclubonline i think it has such an effect because the planes are so light
Oh I see. This makes sense. Thank you!
Pilot? Oh ok
@@kuartz.I think some planes actually did that (keyword: did, not anymore)
Another amazing video. Thanks a lot! One question, what does “P” stand for in P-factor? Propeller? Pitch? Something like this?
Bill Kershner defines P-Factor as "Propeller Disc Asymmetric Loading" in his book "The Advanced Pilot’s Flight Manual (6th Edition)". I am fairly certain that P stands for propeller as P-factor cannot exist without a rotating disc of some kind.
Another thing that I think it's a fun fact, is that P is one of the letters that isn't mirrored in any way.
So it could represent an unbalance
@@afoxwithahat7846 p and q are often depicted as perfect mirror images of each other in lowercase. My kid (and many others) initially had a very hard time seeing the difference between the two
@@afoxwithahat7846 interesting but i dont think someone thought that far 😁
@@afoxwithahat7846 P also is the first letter of Pilot, and they can be unbalanced sometimes. 😉
I now understand that the propeller contributes to the straight line.
Thank you very much.
Why would this not cause the aircraft to pitch downwards due to gyroscopic precession? Just like a helicopter where the cyclic pitch acts a quarter rotation after where it is applied? Is the rotating mass simply too small?
And I got it wrong yesterday exam. Wish I have watched it earlier.
Sorry to hear that.
A very pleasant voice. This girl must be very beautiful.
Thanks for the most simp and irrelevant comment on UA-cam.
Hi Flight Club! I am a student of Aerospace Engineering at Middle East Technical University. I am following your videos by having fun, I am also a voice actor. I want to voice your videos in the Turkish language because I want to teach young people and children who don't know English something about aircraft. Can I use your videos on my new youtube channel? I am waiting your reply.
Yes, of course you can. What is the name of your channel?
@@flightclubonline it will be "Emin Bayar" again.Thank you :))
Im new to the channel , the content is short but still convey'd enough knowledge for me to understand the situation , and to know what to research
I like it , thank you
That Propeller do be pushing the 🅿️
Thanks for clarification. When I was a young man, my father had friend who was a retired engineer for the Sperry Gyroscope Co. He applied for a patent for an airplane propeller that would develop vertical lift! While also providing horizontal thrust. The gentleman is unfortunately long passed, but I’m sure his patent survives. His name was Mr. John Ryan, he lived on Long Island, NY. The patent was filed in the mid 1950’s. I don’t know if it was approved and issued.
I have a question: At 1:30, what is the white line oriented at? At the down-going blade, it is perpendicular to the direction the plane/propeller points towards which makes somewhat sense to me, as the airflow will (mostly) be in that direction. But I dont get it with 1:30. Thanks for reading.
At 1:30, the white line is the up-going blade's relative airflow. The green arc (that looks like a line) is the up-going blade's angle of attack.
That's my fault. I should have made the images bigger.
@@flightclubonline No, the images are fine, I just did a little sketching of airflow and pitch myself and get it know.
This lady's voice makes me want to know more about anything she chooses to talk about.
her: "Today we are going to be learning about plate tectonics, it actually has nothing to do with aviation"
Me: Go on then, tell me more. Are these dinner plates or lunch plates?"
Should be called “ABE” Asymmetric Blade Effect. That would make way more sense than “P factor“.
Why doesnt the Force have a Gyroscopic effect? souldnt the Airplane pitch up, as the force acts 90° of its origin?
Sorry but one blade cannot travel further and not go faster through the air than the other one as mentioned at 1:39! What happens is that due to the difference in angle of attack the "bite" of one blade pushes more air mass than the other one and that is why it has more thrust not because it goes faster nor further! can you imagine the blade that goes further and faster getting ahead of the one that goes slower like in the cartoons? Keep in mind the propeller blades "push air mass!" So if the angle of attack is very different when facing the airflow then one blade will push more air mass than the other one but no blade cannot go faster than the other one just simply because they are attached to the same "object" moving at the same speed! Please make sure you guys use the proper terms when explaining these things because you can just cause confusion to the people and it misleads the people rather than helping them to understand! Also using the proper terms will help you to understand the physics of it!!! I am a student pilot and you can watch few of my videos in my channel but also I am an Engineer and I learnt physics at school!
This is the first time P-factor has been explained in understandable terms. I am an instrument pilot and have only ever heard instructors say stuff like up and down blades, but never explaining that the down blade gets a bigger bite and more thrust. I actually think most instructors don't understand this but just repeat an explanation that they've heard. So, bigger bite and more thrust on the down blade; step on the right rudder pedal.
I still don't understand how the AOA is being increased, it's a fixed pitch. The AOA is from the chord line to the relative wind. But as you climb, it appears the blade becomes more laminar to the airflow. If you compare this to helicopter Disymmetry of lift (or Helicopter P-Factor). It explains that the advancing blade (Descending) blade is slower. You have headwind + the movement of the descending blade that goes against the wind = slower. The Ascending (retreating blade) moves faster. Everyone explains it the same way. The....the descending blade takes a bigger bit of air... get it? Please help, not connecting the dots.
You are right. This video’s explanation is wrong. Both ascending and descending blade’s AOA are not that different. The only thing changes remarkably by P-Factor is each blade’s strength of the relative wind. As the descending blade’s relative wind, which is perpendicular to the propeller shaft, is combined with the airspeed(airplane’s relative wind), the descending blade’s AOA decreases and its relative wind vector increases. On the other hand, the strength of ascending blade’s relative wind doesn’t change that much while the AOA decreases. As a result, AOA on each side of the propeller remains similar but the descending blade’s strength of relative wind becomes bigger. I don’t know if you could check my writing but i can e plain it with a picture if you message me.
Thank you! I've heard of this since my flying lessons back in High School...I knew it happened but never understood exactly why ...
Thank you!!
Amazing, it’s like you read my mind with the timing of posting your explanations! Thank you so much
You're so welcome!
Excellent! I'd been struggling to get what this so-called P-Factor really is, till I came across this video, which took all my doubts away. Thank you!
Glad it helped!
🅿️ factor
I would think that the force applied there would transfer 90 degrees ahead as it is being applied to a spinning object. Kind of like how helicopters cyclic stick changes the pitch 90 degrees around the disk to where you think it would change the pitch.
The force (really) moment on a spinning object isn't transferred 90 degrees ahead. That's a misconception about how gyroscopic motion works. For a free (or nearly free) rotating body, like a helicopter rotor, the spinning body precesses when a torque is applied. It's a nice mnemonic to say that the force is transferred 90 degrees ahead, and that gives the right prediction of which way the body will precess, but it's not that the force is somehow redirected. For example, if you were to attached the axle of a bicycle wheel to a rigid load cell (a sort of electronic scale), and applied a force to the rotating wheel, the load cell wouldn't measure the force as occurring 90 degree out of phase with the application, it would measure it as occurring just where it was applied. But if you were to hold the axle in your hand, and apply a torque to the axle, the wheel would precess in a direction apparently 90 degrees out of phase with the application of the force. In the case of a propeller aircraft, if the pilot applies controls to keep the nose pointed in a fixed direction, there is no precession, and so all the forces must be in equilibrium. That means that an aerodynamic moment (right rudder) must be applied that exactly counteracts the P-factor.
From this thing I realized that little thing can make a huge impact to another. I am curious whether gravity force also making a significant role in this situation? Thank you
Thank you for this video. I've always thought it was an effect related to the engine itself and not to the blades.
Glad it helped
"... in addition to this [the angle of attack], the down-going blade travels further and therefore faster through the air than the up-going blade. These two effects combined cause the down going blade to produce more thrust than the up going blade and cause the airplane to yaw to the left." After a chat with GPT and rewatching this section several times, we are both confused by this. Is this inaccurate? It seems that both blades travel the same distance.
If the prop shaft is tilted upwards, the down going blade does travel further. Greater the angle+airspeed greater the thrust difference
Again, excellent, thank for sharing.
What about propellers with more than 2 blades? And helicopters blades? And when combined with the torque effect?
Damn now I know why I was landing sideways … THANK YOU
Does gyroscopic precession not have an effect here? If there is more thrust produced on the right side during a nose up attitude, why wouldn't that force take effect 90 degrees later in the plane of rotation causing the nose to pitch up more?
It actually does. When you apply higher power settings in order to accelerate but still at a low speed the gyroscopic effect is amplified
Excellent description. Keep up the great work. February 14th 2022
Thank you kindly!
wow, thanks
👍
Magnifique. Merci.
Is there any way to manipulate the pitch of individual blades to make the trust more effective?
I had such a hard time trying to figure out why the p-factor occurred, until I watched this video. My checkrides in a few days, thanks for the help!
Glad it helped! Good luck.
That's too bad. No student pilot should ever have to endure a flight instructor who can't explain something as BASIC as p-factor.
nice but, what does the nose up have to do with the amount of air that is displaced by a propeller? The helicopter is displacing air downwards and the angle of the aircraft does not change the amount of thrust. The angle of the plane with respect to the earth does not change the amount of air particles displaced backwards by each side of the propeller... but from your explanation, it does. Why?
It seems it has to do with the plane's fly path. If it's not perpendicular with the motion of the propeller, there's a difference the angle of attack due to different airspeed. An airplane doesn't always travel in the same direction of it's propellers. As for the helicopters, they can alter the pitch of the blades with the cyclic to correct any imbalance. 1:07
I"m not a former aerospace engineer, but I think this phenomenon has more to do with the gyroscopic energy.
It is when the plane it self traveling horizontally but the nose is pointed up. (In reality when going slow the nose is gonna be pointing higher the the direction of travel) Helicopters have something called swashplates what account for movement which automatically changes the angle of attack of the blades to avoid it
I don't think that it changes based on the direction the plane is flying, but during the moment in which the airplane is changing its pitch angle. We know that the tendency of the airframe is to rotate around its CG, therefore the bottom blade will travel a longer distance when pitching up, or a shorter distance when diving the airplane. The moment that the rotational movement around its CG stops, the blades will match the AOA once again.
@@DiamondBlade_101 the helicopter compensates for the forward speed. The advancing blade will travel through the air faster than the retrieving blade. The system compensates for the difference by increasing the angle of attack of the retrieving blade, otherwise the helicopter would have a tendency to roll left the faster it goes.
Great explaination!
Great explanation in a version of English I understand.
Thank you so much for your feedback.
Great explanation, often the faster descending blade is missed from this explanation.
I learned about P-factor 40-years ago while training to fly ultralights.
Right ruddddder!
p power pushin p
👌👌👌
Excellent
Ooook, that was interesting microburst of information.
Never knew this was a thing.
And now I understand it too. :)
I love applied physics. Want asymetric? Check out the setup of NASCAR or Indy car for oval tracks. That's asymetric. With a LOT of parameters. I rather stick with good old road and track.
can you also explain gyroscopic precession?
For "youre right guy", his mom, and Richard Moore, propeller has left yaw tendency due to torque, same for ships turbine etc. This is the origin of "youre right". Because your scouting division has no mission. Nobody bothers to explain anything to your Top Gs.
It's even worse for helicopters... bigger blades, actually rotary wings.... being horizontal one wing is traveling forward at it's speed + aircraft speed, the opposite wing travels rearward, at it's speed - the aircraft's forward speed. End result, one wing creates significantly more lift, (asymmetry of lift) trying to spin the aircraft over.
reality check the Theory discussed in this video is Specious/false .!!!
1) p-factor is always present. 2) p-factor is the feedback torque that comes from a CW rotating prop.!!! 3) p-factor is most noticeable, and dangerous, during a take-off. 4) p-factor occurs because (at take-off) the wing is not yet fully 'flying'. meaning, the 'normal' zones of pressure around the wing are not at full strength. (the term p-factor refers to an 'unscheduled turn to port'.
It is crazy that people in ancient china didn't discover this simple effect.
There is third effect coupled to the two effects nicely addressed in this video. The propeller causes the air to spiral in the same direction it turns. Using the same example, where the propeller turns clockwise when seen from behind, the air swirls so that it moves downward at the right side and upward in the left side of the aircraft. The air going down passes "clean" under the fuselage, crossing the airplane's belly from right to left. The air going up meets its fuselage, vertical stabilizer and rudder crossing the airplane's top from left to right. So it attacks those surfaces at an angle, thus generating lateral lift, pushing the tail to the right. This effect decreases as the airspeed increases.
While you did a good job explaining the spiraling slipstream cause of left turning tendency, it doesn't belong here as P-Factor and Spiraling Slipstream are entirely different causes of left turning tendency.
By tilting the prop like that you increase the chance of a stall.
Horizontal velocity is the most efficient way to produce lift.
Thats why its called a 'plane', and not a helicopter.
Tilting the prop is equivalent to putting a ramp on your runway / aircraft carrier.
So would there be any P factor for a single blade propeller? (Yes that is a thing. It was fairly common on aeronca’s and early cubs)
First of all, your videos are absolutely clarifying and fantastic, but in this one I've noticed something wrong: when you explain the changing of plane of rotation since the nose pitches up, you consider, for the downgoing blade, the angle of incidence not the angle of attack, because you're keeping in the video the angle between the chord line of the blade and the rotation plane (for definition is the angle of incidence) and not the angle between the chordline and the relative airflow (angle of attack)...for this the red slice of angle should be smaller in the rappresentation, but however it would always be smaller than the angle of the upgoing blade.
Maybe i'm wrong, I look forward to your reply. thaaaanks!
I always thought P-factor was the effect the corkscrew propeller turbulence placed on the left side of the vertical stabilizer.
For all people who are watching:
_NO ITS NOT THE PP-FACTOR_
thanks this made so much sense
If you're ̶h̶o̶m̶e̶l̶e̶s̶s̶ P-factoring.... just by a ̶h̶o̶u̶s̶e̶ a second engine (duh).
Oops this does not pass CFI cross-examination. No mention of angle of attack or of how p-factor switches sides when decelerating and descending.
Thank you so much. Marvelous explanation🎉🎉🎉
Thank you for the kind words.
This effect only applies to taildragger aircraft and not tricycle landing gear aircraft during takeoff and Landings. but as both aircraft encounter the same angle of attack while in flight the p-factor is negated.. .
aaahh, is this why the plane wants to turn left when speeding up on the run way?
Not a pilot, just a virtual pilot. Figured i'd steal a plane one day if they are all grounded.. 😅😅 I'm bored and i miss travelling.
What doesnt make sense to me is how the propeller's relative airflow changes in angle. How can the down going blade have a different relative airflow angle with the up going blade if they are already both equal when levelled. Why doesnt that stay constant although they are still spinning the same motion. How do we know what is the correct angle of relative airflow between each propeller? At 0:42 and 1:24 how can the arrow change.
If the blades are rotating on a variable axis yes.. but when on a fixed axis ie a propeller shaft, the blades will not vary on their pitch.. only helicopters have blades that have variable pitch because this p effect is what you use to fly the thing.. if a plane had variable pitch and was flying with a front facing prop and it decided to change the angle of its dangle it would rip the blades off or cause the motor to stall out..
Why di she measure the down going angle of attack from the base of the propeller and she did not measure the up going from the base?
This is 2d. In a 3d world the angle of attack does not matter its omnidirectional. The p factor is the differential of the aircraft rotating around the propeller centerline against the drag of the propeller. The airplane wants to lift one wing increasing its speed and yawing the aircraft against the direction of travel. 😊
Precisely why when you put an engine into a single-engine aircraft, you actually set it about an inch forward on the left side than on the right, or opposite that if the engine rotates counterclockwise from the aspect of the pilot. Where this affect becomes most pronounced is on twin engine aircraft and you have an engine go out where the pee effect is on the outside of the engine that still running. Which is why twin engine aircraft should actually have counter rotating props.
so, while pointing nose down in a descent P factor affects the opposite blade right?
I wonder if contra-rotating propellers (2 propellers stack on each other rotating in opposite directions) negates the P-factor
Great explanation. I subscribed.👍🏻
Awesome, thank you!
perfect demonstration
Just learned something. Hmm. I subscribed.
OMG, I always thought it was pee-factor!
Thank you so much
You're most welcome
OOPs! I thougth I was going to see a video about statistics and P-value 😊
Awesome content
Way too unnecessarily complicated explanation.
And this is part of the original reason why aircraft carriers have the island on the starboard side.
I always thought is was a gyroscopic effect. Thanks
So this is why it's impossible to get a plane straight in the takeoff in SB war thunder
When I soloed,
precession almost wiped me out.
Why isn't gyroscopic precession a factor?
This is why you only want to use rocket engines when you want to fly in a straight line. Airlines only choose cities that are on a curved line to each other.
But air everywhere is the same, and blades symmetrical...
Boat props do the same thing, pull a little to one side. Dual props rotate opposite direction to equalise that
.au ? Als erster Schaetzung kann angenommen werden: bei 1500 N Schub und 15 grad Flugzeug-anstellwinkel etwa 200 Nm effect. Also Mzz = 200 N.m und das ist Wechsel-biegung auf die propellerpachse, also Wohler-biegung.
You wrote the clip, so I hope you understand the values.
I thought P Factor was the degree of urgency a pilot has to urinate.
Thank you
You're welcome
And in helicopters, the effect much greater.
Great explanation ! Thank you
Thank you for your feedback.
amazing!
Thanks!