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Model Forum / Radio Controlled / Air Models / August 2007noob Q: does torque make aircraft bank more readily one way vs. another?
my left turns are good. smooth. well coordinated. same plane. same radio. same thumbs. my right turns are really bad. poorly coordinated, blah, blah, blah. does the torque from the prop have anything to do with this? or do i just need to practice more right turns? w Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: > my left turns are good. smooth. well coordinated. > [quoted text clipped - 5 lines] > > w You need to practice more right turns. The torque (or "P" factor) only comes into play on take off. Once you are flying any torque is not noticeable. This is presuming you have a single engine plane - twins are another story altogether where the torque does factor in, especially if the engines are not in sync or one engine dies. > Ted shuffled out of his cave and grunted these great (and sometimes not > so great) words of knowledge: [quoted text clipped - 10 lines] > You need to practice more right turns. The torque (or "P" factor) only > comes into play on take off. P factor is not torque. Its gyroscopic precession. Torque maintains its effect throughout flight. > Once you are flying any torque is not > noticeable. It bloody well is if you slow down.. > This is presuming you have a single engine plane - twins > are another story altogether where the torque does factor in, especially > if the engines are not in sync or one engine dies. "When the blind leads the blind, they both shall end up in the ditch." >> Ted shuffled out of his cave and grunted these great (and sometimes not >> so great) words of knowledge: [quoted text clipped - 12 lines] > >P factor is not torque. Its gyroscopic precession. Ummm, no. P factor is an offset of the effective thrust line that occurs at high angles of attack, when the descending prop blade is at a higher AOA, and therefore develops more thrust, than the ascending blade. It's why a taildragger wants to turn left early in the takeoff roll. Gyroscopic precession exists only when the orientation of the prop axis is changing: i.e., when the airplane is rotating in pitch and/or yaw. It occurs as you raise the tail, and ends when that pitch motion stops. In light airplanes it's hardly noticeable because it starts just as the P factor is going away -- if there were no gyro precession and the P factor lasted just a bit longer, it would feel the same to the pilot. rj > > Ted shuffled out of his cave and grunted these great (and sometimes not > > so great) words of knowledge: [quoted text clipped - 25 lines] > > "When the blind leads the blind, they both shall end up in the ditch." Four factors that pull an airplane to the left on takeoff: 1.Torque. The torque reaction of the prop rotates the fuselage the other way, putting more weight on the left wheel and increasing its drag. 2. Gyroscopic precession, notable when the tail is raised and in turns. 3. P-factor, the assymetric thrust when the engine's axis is tilted higher than the airplane's flight path so that the downgoing blade's AOA is higher and the thrust is offset to that side. Noted in takeoff, climb and slow flight. 4. The swirling prop blast that strikes the fin on the left side and pushes the tail right. Noted at low speeds and higher power settings. The air coming off the prop has an angular component to it, a result of the drag of the prop blade. All from flight training textbooks. Dan >>> Ted shuffled out of his cave and grunted these great (and sometimes not >>> so great) words of knowledge: [quoted text clipped - 33 lines] > The air coming off the prop has an angular component to it, a result > of the drag of the prop blade. 1 and 4 are components of the same thing really. the 'spirality' of the airstraam implies a torque moment. Any bits of the aircraft that straighten the 'spirality' out introduce a reverse torque. > All from flight training textbooks. > > Dan > my left turns are good. smooth. well coordinated. > [quoted text clipped - 5 lines] > > w Engine torque makes too little difference. It's the gyroscopic precession generated by the propeller in the turn that makes the right turn more difficult. In a left turn the precession helps keep the nose up; in the right turn it pulls it down, and more back pressure is needed. And if you are a bit clumsy with the rudder, the turn won't be constant and neither will the precession forces, and you'll be all over the sky. Dan >> my left turns are good. smooth. well coordinated. >> [quoted text clipped - 15 lines] > > Dan Dan nailed it perfectly. During left turns, the nose rises (with a counter clockwise rotating prop viewed from the front). With the same prop rotating in the same direction, the nose will tend to drop during right turns, making the pilot carry a bit more of "up" elevator in the right turn than in the left turn. Ed Cregger >> my left turns are good. smooth. well coordinated. >> [quoted text clipped - 15 lines] > > Dan Gyroscopic precession is not generally an effect you notice unless its a VERY high powered machine. Torque is very noticeable particularly with large diameter propellors (D>25% of span) > Dan_Thomas_nos...@yahoo.com wrote: > >> my left turns are good. smooth. well coordinated. [quoted text clipped - 22 lines] > Torque is very noticeable particularly with large diameter propellors > (D>25% of span) Gyroscopic precession shows up in all full-scale airplanes, even in those low-powered machines with wooden props turning rather slowly. It's a factor in steep turns as well as any rapid pitch changes. In a model with a light prop but with the much higher RPM it WILL be a factor. Even the engine's rotating mass will have its effect. Dan >> Dan_Thomas_nos...@yahoo.com wrote: >>>> my left turns are good. smooth. well coordinated. [quoted text clipped - 25 lines] > > Dan It has an effect, but not as much as the torque....although it depends on the way the model is set up. I fly a lt of small electrics, and mostly they are large diameter slow revving stuff. Those are monumentally subject to torque..a full power on stall will always flip the left wing down.. OTOH a smaller model with a huge brushed motor and loads of power into a small prop showed none of that, but curiously in turbulent weather, it would 'wag its tail' over the bumps. I eventually worked out that the rapid pitch changes were introducing yaw due to precession.. > Dan_Thomas_nos...@yahoo.com wrote: > >> Dan_Thomas_nos...@yahoo.com wrote: [quoted text clipped - 32 lines] > monumentally subject to torque..a full power on stall will always flip > the left wing down.. There's another cause for that wing-drop. The air coming off the prop is angled upward on the left, downward on the right, and this changes the angle of attack at the wing roots. The left side has a higher AOA than the right, and the stall starts sooner o that side. Even full-scale, relatively underpowered airplanes will do that. It's called a departure stall and gives new students the willies when we demonstrate it. Dan bingo! the nose drops when i turn right. and, yes, i am all over the sky! ;-) i'm getting better, though...practice, practice, practice. w On Aug 27, 10:36 pm, Dan_Thomas_nos...@yahoo.com wrote: > Engine torque makes too little difference. It's the gyroscopic > precession generated by the propeller in the turn that makes the right [quoted text clipped - 3 lines] > constant and neither will the precession forces, and you'll be all > over the sky. >my left turns are good. smooth. well coordinated. > [quoted text clipped - 3 lines] >does the torque from the prop have anything to do with this? or do i >just need to practice more right turns? I never worried about exactly "WHY" right hand turns are different than left hand turns, I know that there is a difference, but trained my thumbs to compensate for the difference without thinking about it. Whatever you do, do NOT think of right hand turns as being "harder" than left hand turns, different, yes, but not harder. My instructor when I learned to fly, taught me that the two were different, and I have never had a problem with the right hand turn. Over the years, I have seen an amazing number of RC pilots who can not or will not set up and land in a right hand pattern, They are intimidated by a right hand turn on final, and will resort to doing a "fishhook" approach so the last turn can be to the left, I even saw a "hot-shot" who could hover his plane ad-nauseam, but could NOT do a right hand turn to land. He walked across the active runway, faced into the setting sun, and landed his plane (from his left) all to avoid doing a right hand turn on final. >>my left turns are good. smooth. well coordinated. >> [quoted text clipped - 29 lines] > his > plane (from his left) all to avoid doing a right hand turn on final. UGH! In most cases those fishhook turns wind up with the aircraft being behind the flight line and *I* really really really hate that. This is one reason I use the horizontal figure 8 in training. Hard to do with turns only one way... Jim AMA 1428 >UGH! > [quoted text clipped - 3 lines] >This is one reason I use the horizontal figure 8 in training. Hard to do >with turns only one way... It makes me shudder just thinking about it. I don't venture out into the airplanes space, and I really don't like it when the airplanes come into MY space either. My instructor made me do left hand approaches, right hand approaches, figure 8 patterns, AND obstacle avoidance, The field where I started had a TALL chain link fence topped with 3 strands of barbed wire about 20 feet from the end of the runway, as a bonus feature, there was an old dragline type crane whose usual parking space was about 50 feet on the other side of the fence and more or less in line with the runway. never bothered me, because my instructor refused to let it bother him. A good instructor is worth his weight in gold. he will NOT let you slide by with poor performance, he will make you learn to fly. |
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