steve murray

steve murray

Well Known Member
I have been slowly working on my aerobatics. On my simple aileron rolls (no rudder, no elevator, simple pitch up an roll) Seems like aileron rolls to the right result in the nose dropping further than rolls to the left.

Is this only me or my imagination or is this to be expected?

Steve
RV8
 
Steve,

That's about what I have found on my -9. Only one thing, don't forget to neutralize the elevator before putting in the aileron.

In short, pitch up, stick to neutral, then aileron. If you still have back stick when you roll it over, I have found the nose to be a bit lower than desired on rollout.

The most G's I've pulled in this maneuver is 1.3 and that was on an over aggressive pull up.

Oh, and you aren't supposed to roll a -9 BTW.
 
I have noticed the same behavior.

I surmised (perhaps incorrectly) that it's due to the rotation of the prop. The torque of the prop makes the roll to the left go faster and the roll to the right go slower. Since the turn to the right takes longer, there's more time for the nose to drop.

Who knows...maybe I'm way off base here, but at least the theory makes sense.
 
Thats exactly

Whats happening.

The RV will roll more quickly to the left than it will to the right for the same amount of stick input...due to the engine torque of course.

The trick is to ease forward on the stick sligthly when inverted...(You can also add top rudder at the 90 and 270 degree positions..This is what you do in a slow roll or hesitation roll if you have inverted fuel and oil...But that is tricky to get right without LOTS of practice)...Anyway a small amount of forward stick will prevent the nose dropping so much.

Frank
 
aileron rolls

A true aileron roll is done with neutral elevator and just a touch of coordinated rudder. It is possible that on the roll to the right you are allowing the aircraft to yaw slightly to the left before starting the roll. Torque is a misnomer. The force involved is p-factor. If the pullup is too aggressive a bit of gyroscopic force is involved. Most all airplanes with clockwise rotating engines(as viewed form behind propeller) slow roll better to the left and snap/spin better to the right.
 
P-factor

JRS writes: The force involved is p-factor.

And that makes sense. It's the same reason that you need right rudder when you nose up for landing flare.
 
Not Just P-Factor

jrs14855 said:
... The force involved is p-factor...
Click to expand...

Actually, the four major forces here are torque, p-factor, corkscrew slipstream and gyroscopic force. The relative importance of each depends on several factors.

P-factor is a function of angle of attack. It is relatively independant of power, and will reverse itself with a negative angle of attack. It produces mostly yaw (with some roll coupling).

Torque is the reaction to the engine spinning the propeller. Its effects are greater with high engine power, and more torque is produced with reduced RPM at a given power setting. It produces mostly roll with some yaw coupling.

The action of the propeller imparts a 'corkscrew' vortex to the propeller slipstream. This is again dependant mostly upon power, and the uneven forces (mostly on the tail surfaces) cause both yaw and roll forces.

The spinning propeller imparts gyroscopic forces on the airframe whenever the plane of the propeller is changed (including pitch changes for take-off and landing). Lightweight propellers and reduced RPM will reduce gyroscopic forces. Rolling will not cause any gyroscopic reactions, but yawing will cause a pitching force on the airplane, while pitching will cause a yawing force.

As you can see, manuevering flight will change the magnitude and sometimes even the direction of these forces - they will not be constant. Most pilots develop a 'feel' for how to counteract these forces, but understanding them helps to learn the 'feel.'

Pat
 
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