2.29 Many of my add-on piston aircraft veer off the runway - is this reality?
From FlightSim
Q:
MANY OF MY ADD-ON PISTON AIRCRAFT VEER OFF THE RUNWAY IF I DON'T USE THE RUDDER, EVEN WITH NO WIND, WHEN THE REALISM TAB IS SET FOR "REAL". LAST NIGHT THE PROBLEM WAS PARTICULARLY BAD WITH A CAMEL. IS THIS REALITY?
A:
Yes, all prop driven A/C are subject to torque effect. You should get it with turbo props too. Stand on right rudder to correct. One twin Piper, Seneca ?? had counter rotating props that should have neutralized torque effect. Same thing applies to boats.
Jim McCarthy
Could be that torque was overdone. All prop aircraft will turn in the direction
opposite the direction the propeller/engine turns due to torque effects. It's
the equal and opposite reaction physics deal. The Camel should have some real
nasty torque effects if modeled "realistically" as this aircraft has a rotary
engine in which the entire engine rotates at the same speed as the prop.
That's a lot of mass spinning around out in front that will cause the plane to
turn in the opposite direction of the rotation especially at high RPM low
airspeed situations such as initial takeoff roll. I don't know if MS modeled
such effects into this plane. or if it's even possible to do so but the torque
effect is real and does effect prop planes.
Dave
Torque and propeller effect (P-effect) are very real in propeller-driven a/c.
In U.S. built engines it normally results in a left-turning tendency that must
be corrected with right rudder (US-built, because there are some manufacturers
in other countries whose engines, therefore propellers, turn the opposite
direction). This should be easily correctable with a bit of right rudder
pressure. It should be less noticeable in twins, but uneven thrust can cause
all kinds of yawing tendencies.
But it's more than torque. Gyroscopic precession and "propeller effect" also play a part. Torque tends to roll the a/c. The other two yaw the a/c.
Anything that rotates acts a bit like a gyroscope; the more massive it is, the more pronounced the effect. A gyro is a bit like a toy top, the spinning keeps it stable. Gyros are used, for example, in the artificial horizon instrument (excuse me, that is now the attitude indicator), the direction gyro (gyro compass) and the turn coordinator or turn and bank instrument. Gyros are also a major component of an inertial navigation system.
The precession comes with an attempt to "tilt" the gyro -- it resists this, and translates the motion to a different axis 90 degrees away from the attempt, thus raising the tail on a tailwheel a/c is resisted by the propeller/engine rotation (gyro effect) and causes a yaw. In US built engines (they rotate clockwise as seen from the cockpit) the yawing tendency is to the left.
So with any or the rotary engine a/c from the WW I era, the tremendous rotating mass would cause a MAJOR yawing effect. Many of the high power fighters from the WW II era had tremendous torque, some to the point that pilots couldn't really apply full power until they had enough speed for the control surfaces to fight the torque. It's my understanding that there were a few instances of such fighters actually being rolled over on their backs from applying too much power too soon.
Propeller effect comes from the fact that the propeller is an airfoil, just like a wing, and each blade generates "lift" in a forward direction that results in effective thrust. However, at any time that the relative wind is not precisely perpendicular to the rotational axis of the prop, the blades have an uneven angle of attack, therefore generate differing amounts of thrust.
Picture the a/c in a climb: the relative wind is coming from below the nose, thus the downgoing blade (let's limit this for the moment to a 2-blade prop) has a higher angle of attack (thus more thrust) than the upgoing blade. Since the downgoing blade on a US built engine is on the right, it tends to cause yaw to the left.
A/c designers compensate for these effects, usually optimized for anticipated cruise speeds, with offsets of the vertical fin, offsetting the engine mounting, and even, on some a/c, a different angle of incidence on each wing. This is a far from comprehensive list of the compensations and compromises, but is likely far more than most people wanted to know in the first place.
Larry N.
