I know right its sad that not enough RU-vid content that could be great for education is used for that. And getting a visual representation makes it so much easier to understand than if you just have a teacher talking. Sorry for going on a rant😅
The conclusion here is wrong, you need rudder on takeoff because counteracting the torque of the propeller uses aileron, and the drag of the aileron causes a yaw torque on the aircraft. As for the right side of the propeller having more lift, that is true, but due to gyroscopic procession, that torque is actually a pitch up not a left yaw.
If you are flying a tricycle gear plane then torque is about the only factor causing a yaw to the left, up until the point of rotation. Once you rotate P-factor occurs. On conventional gear planes P-factor sets in almost immediately until the tailwheel is rotated off the ground then diminishes. Basically anytime the plane is at a high AoA and power setting P-factor will occur.
That is how every single twin prop aircraft works. Aztecs, Barons, P-38’s etc. The issue at hand only applies to single prop aircraft, which would eliminate the P-38.
@@cmilburn26. Actually, that’s not always the case. There are many multi-engine aircraft that DO NOT have counter-rotating engines and propellers- including ones you mentioned. This is why such aircraft are deemed to have a critical engine with respect to aircraft handling in the case of an engine failure. www.faasafety.gov/files/notices/2015/Nov/FAA_P-8740-66.pdf
@@cmilburn26 Nope. Most twins have same sense rotating props. Too expensive to build engines for both senses of rotation. That's why twins have a so called 'critical engine'. If that fails, the P-factor of the remaining engine acts outboard, giving an even greater asymmetry of thrust. Except the P-38. They chose sense of rotation of the props such, that the P-38 had TWO critical engines...
@@egor_flipsYou could say that, but there are a number of exceptions. Ju-52, Ford Trimotor, numerous Italian ww2 bombers, or the Lockheed Tristar to name a few.
Helicopters also have an issue similar. The faster they are moving forward. The advancing side of the main rotor gets more lift than the retreating side of the main rotor. Then, the power stopping procession causes that change in force to be applied 90° around the spin axis.
This is called the Dissymetry of lift. Not really the same issue, but simmilar effect. The reason it happens is because you have an advancing blade ( the blade going in the same direction the helicopter is travelling) and a retreating blade ( the one going in the opposite direction in which the heli is travelling). Blades need airspeed to produce lift. More airspeed = more potential lift. The one going in the same direction of travel as the helicopter will have an effective airspeed which is equal to its own movement plus the forward speed of the whole helicopter. On the other side the retreating blade will have an effective airspeed equal to its own movement minus the helicopter's forward speed. Thus the two sides are producing unequal lift. The faster the heli flies, the greater the effect. This can be compensated for during its normal flight envelope, however when a heli reaches the critical airspeed where the retreating blade can no longer produce enough lift it will stall and its lift will dramatically reduce. This produces a large inbalance in lift. The force is displaced by 90° in the direction of rotation of the blades and causes the nose of the heli to pitch up violently. This phenomenon is called retreating blade stall. Basically it stalls because it flew too fast.
Right, except the end. The video assumes the propeller rotates clockwise (viewed from behind). For anti-clock rotation the effect is reversed, and rudder use would be opposite. This was the first effect a Spitfire pilot experienced when moving from Merlin to Griffon powered Spitfires, as the Griffon rotates opposite to the Merlin.
@@homestyle2000 US engines tend to rotate clockwise (when viewed from the rear). British engines tend to rotate anti-Clockwise (eg Bristol Hercules). Except the Merlin! There is no fixed rule though.
you should also look at adverse yaw. its the yawing effect that using the ailerons cause and the reason why coordinated turns are a difficult skill to develop for some pilots.
@@infotechsailorYou are referring to two different effects. P-factor is what is explained in the video. The slipstream effect is due to the spiralling propeller slipstream hitting the vertical surface of the plane (usually the vertical stab) on only one side, thus pushing it in a direction and yawing the nose in the opposite direction. The existance of the slipstream effect has been debated by aerodynamicists.
The P-factor. One of the causes of the left turning tendency, for those student pilots out there. Flight instructors don’t drill your head with “Right rudder! Right rudder!” for no reason lol
As far as I know, it's a combination of torque, spiraling slipstream, P-factor, and gyroscopic precession, not just the P-factor that turns the plane to the left for a clockwise rotating engine.
Gotta use the rudder while takeoff and slowly increasing throttle and go in a straight line slowly then increase speed so you won't spin out the moment you hit full throttle
And can't forget the most obvious problem with singular propellers is that the propeller itself is constantly pushing the whole plane to rotate to the opposite direction of wherever the propeller is turning at.
So why do they turn on the ground also if its the angle of attack when the planes level on the ground? The blades are spinning fast air moving fast wouldnt that push on the vertical stabilizer no matter what even level? This guys comment makes more sense then yours and tons of other peoples. Js
Even more complex than that. The air does not flow in a straight line, but in a spiral. It will hit the left side of the vertical stabilizer more directly than the right, thus acting like it is being given left rudder.
"By pointing the propeller slightly to the right, this effect is offset a little and the aeroplane becomes more balanced." I still come back to that video sometimes, just to calm my mind ❤
It took long time for me to understand this subject in order to pass my Principles of Flight exam. I studied long time to understand, just to know this subject in the video. I passed my exams with the help of flightclub. Thank you very much. I got excited when I got notification that flightclub uploaded a new video. I don't need this information now at all but I enjoyed watching it, without hesitating if I am going to be able to pass my next exam. Thanks a lot! I burnt my ATPL books but I will keep following your channel :))
But that's due to propeller slipstream going around the fuselage. I generally fly pusher airplanes and those require no rudder input during climb, descend, or any range of throttle input.
No that's from the spiraling slipstream and torque effect. What is described in the video is P-Factor, which would be most pronounced with a high "deck angle" but level flightpath (like slowflight). In theory a taildragger could experience P-factor during the takeoff roll, but it is not even perceptible at low airspeeds. Before the airspeed would be high enough to make it effective, the tail would be raised already eliminating any P-Factor.
Ya this is false. That may be true after you rotate and you’re climbing, but on the takeoff roll, we use right rudder to counteract the propwash hitting the vertical stab, as well as the torque from the engine.
Here's an interesting propeller story: The early Battle of Britain Spitfires lacked a device to provide variable propeller pitch, which pilots felt was seriously hampering dogfight performance. Supermarine rose to the challenge and working round the clock, had a working system ready for retro fitting to Mk.1's within weeks. Even Supermarine's managing director donned his overalls, loaded his Bentley with the new kits and took it on himself to do on site retro-fitting work at front line RAF bases. This was wartime and such a bureaucray busting go for broke attitude was essential for victory. Indeed, it wasn't until years later that Supermarine realized they had forgotten to invoice the RAF for the cost of the variable pitch upgrade kits and retro fitting.
Fascinating how so many tiny but crucial details like this hide in almost every bit of technology. Humanity has many flaws but damn is it cool how a bunch of self-replicating fermionic matter has managed to bend nature to its will.
Another reason for aircraft yawing to left is spiral effect. Where the airflow or thrust produced by propeller goes clockwise around the air plane's body or fuselage and hits the vertical stabiliser which makes aircraft yaw to the left.. You can read more up on this in principle of flights.. I cleared my technical thanks to you. 👍
Awesome explanation!!! That is why we always add a small amount of side thrust to counter this effect. All the while I thought its only for countering the torque generated by the spinning propellor.
@@ErimTuna172 The Rolls Royce Griffon spins counter clockwise, it apparently caused problems for pilots in Griffon engined spitfires as the merlin engines in earlier spitfires spun clockwise so pilots had to learn to apply rudder the opposite way for take-off.
It makes a huge difference in RC airplanes. The trust-to-weight ratio is higher. Those of us who still scratch build them put down and to the right angles on the firewall. It is a small adjustment that makes a huge difference.
Yep, that thrust to weight ratio is a lot higher on RC planes and tail draggers are really affected by this left turn tendency on the takeoff roll. Do you think that’s more from torque, or because tail draggers are pitched up a little (like on the vid) while on the ground? I always thought we offset the centerline of the engine to compensate for torque or gyroscopic effect (I’m not sure what the correct term is) of the engine rather than differing levels of thrust from the different sides of the prop. Really interesting though.
"Aircraft propellers are more complex than you think" For one, they have varying angle of incidence over the radius. I understand it makes it clearer to show the concept you want to demonstrate here to have a flat blade, but damn, that weed cutter looks strange.
It's even more complicated for rotary wing aircraft. Huey pilot I know said once that there are 3 P factors involved with copters. The advancing blade on a chopper is the reason the aircraft commander sits on the right in a helicopter. Fixed wing aircraft have the command pilot sit on the left...mostly for visibilty in the pattern.
Interesting. I was told that the plane yaws left because the prop wash flows around the plane and pushes on the tail fin. , I guess it's a combination of both
And that’s talking about fixed pitch props, constant speed props are so much more complicated, I remember learning it for the first time and thinking it would be easy
Well, what is the airspeed? While on the runway it changes from 0 to 80 knots. So when the plane starts to roll the angle of attack is the same for up- and downstroke. That changes gradually with increasing speed. And with that the plane lifts the tail first before it rotates. Means the airflow before take-off is again in line with the propeller's axle.
With at least 15,000 flight hours on a power Lazy Boy recliner, I finally see something that is explained in the most simple way that makes a lot of sense. Since my recliner is single engine only, is the reason why dual engine aeroplanes have propellers that spin in opposite directions to counter act the torque pull from the propellers?
It's one of the reasons, yes. Another would be that both engine's torque basically cancels itself out, so changing the throttle input won't make the plane want to roll
Boats have the same issue and it's called prop walk/paddle effect. You have to know your boat's character and how it affects it in order to manouver in small spaces during leaving or mooring. Unlike aeroplanes, for which its just a small effect, in boats it's one of the fundamentals of navigating and used heavily, either to your advantage or disadvantage.
This is the reason why aircraft carriers have the island on the starboard (right) side of the ship. Having the island on starboard side was key to save pilot lives in WW2 when pilots had abort landing. Today they still have the island on this side just because this historical reasons
I was taught the airflow corkscrews around the body of the airplane and hits the tail fin on one side causing yaw to change with power settings. Honestly that explanation never really rung true for me, but I guess I sorta just accepted it. The effect is quite noticeable though. You have to add a good bit of rudder when you pile on the throttle during a go around for example
I may not understand it that well, but I feel this fails to mention the higher thrust on the right side means the center of lift moves right as well - less lift on the outer left and inner right of the wings, & more lift on the inner left and outer right.
The effect is 90° after of where the propeller produce more foce due to the higher angle of attack. That will not turn right, but in that example want to pitch up. The turning effect is due to engine torque specially in high power manovra like take off.
So, if you have two of them hanging from the wings, you can prevent the plane from turning to the left by simply letting them spin in different directions?
Maybe I'm missing something but when the aircraft pitches or yaws in any direction isn't the flight path changing also. I mean thats the whole purpose of pitch and yaw.🤷🏻
I remember something about being told not to yank on the elevator until after the aircraft has enough speed for liftoff. It seems to be an especially noticeable problem with high pitch blades.
Because that only comes into play when changing your pitch at high rpm. This video is about a single "left turning tendency", and one of the more difficult ones to understand. There are torque effect and spiraling slipstream also not mentioned making 4 in total.
