RV-6 Spins... Yeah this again.

[skylor]

Originally Posted by Foxmoth

Spin was IMHO very standard - at light buffet, full rudder and up elevator, the prop stopped as the aircraft autorotated, when I restarted it was at low power and recovered immediately on engine restart, following this I leaned the mixture and recovery was normal with engine at idle.

Just to clarify, you're saying that the -7 won't recover using the PARE method with the prop stopped, correct? How many turns before the recovery was attempted? Is this with a fixed pitch prop? I suspect that the difference between having some idle residual thrust and true zero thrust with the prop stopped makes just enough difference with rudder and/or elevator effectiveness, that more positive (than PARE) spin recover inputs are needed when the prop is stopped on this particular aircraft.

In my -8 with a fully developed (3 turns or more) spin to the right, using positive (opposite rudder) recovery techniques, I need the elevators farther forward than neutral to stop the spin.

Skylor

[RV7A Flyer]

Originally Posted by Foxmoth

This will NOT work for all aircraft, the dHC1 Chipmunk springs to mind, recovers fine using PARE but often will NOT recover until you have FULL forward CC!
Also of interest was the spin tests on our RV7, recovery was fine to the left, first spin to the right the prop stopped (at height with full rich mixture), recovery was not possible with ANY of the methods discussed with the engine stopped, as soon as I restarted the engine recovery was almost instantaneous!

Not sure I understand...are you saying that the engine stopped *during* the spin to the right? Or you had stopped the engine prior to entering the spin, and the prop windmilled when going to the left, but not to the right?

I can't imagine why the engine would stop during a spin...so I must be reading this wrong.

[luddite42]

Originally Posted by RV7A Flyer

I can't imagine why the engine would stop during a spin...

I only know of two reasons - one...that you are running a wood/composite prop and your idle setting is too low for the lack of relative wind through the prop to keep the prop windmilling. During a spin, the relative wind develops a higher angle of attack as the spin develops. Been there more than once. Two...that your fuel level in the wing tanks is insufficient to cover the fuel port as the fuel is forced outward during the spin.

[Foxmoth]

Just to clarify, you're saying that the -7 won't recover using the PARE method with the prop stopped, correct? How many turns before the recovery was attempted? Is this with a fixed pitch prop?

I am not saying the -7 will not recover, just that THIS -7 will not, I would be very interested if anyone else has had the prop stop on entry and the result! Recovery was initiated after 2 turns and took 12 and yes, a metal fixed pitch prop.

Not sure I understand...are you saying that the engine stopped *during* the spin to the right? Or you had stopped the engine prior to entering the spin, and the prop windmilled when going to the left, but not to the right?

I can't imagine why the engine would stop during a spin...so I must be reading this wrong.

Engine stopped as I entered, I just closed the throttle, I think it was probably a combination of airflow, spin direction and mixture setting (at 8,500' with full rich and partially leaning meant this did not happen on subsequent spins)

[ChiefPilot]

Originally Posted by RV7A Flyer

I can't imagine why the engine would stop during a spin...so I must be reading this wrong.

Fuel migrates to the outboard side of the tank, depriving the engine of fuel. This can result in the prop stopping, especially if a low mass (wood or composite) prop is installed.

Also, I think Ron asked why prop stopped or not would make any difference in recovery. Consider the gyroscopic precession forces associated with a spinning prop - I could see how such would have an impact on recovery.

[ronschreck]

I have recovered my RV-8 from spins with prop stopped due to fuel migrating away from pickups during extended spins. Recovery of MY airplane is same with prop stopped or with idle power. Not sure why your experience is different.

[ChiefPilot]

Originally Posted by ronschreck

I have recovered my RV-8 from spins with prop stopped due to fuel migrating away from pickups during extended spins. Recovery of MY airplane is same with prop stopped or with idle power. Not sure why your experience is different.

The side-by-sides are known to have different spin characteristics than the tandems, for starters. That combined with the lack of precession forces and/or the unique characteristics of a given airframe could very well present different spin characteristics.

[RV7A Flyer]

Originally Posted by ChiefPilot

The side-by-sides are known to have different spin characteristics than the tandems, for starters. That combined with the lack of precession forces and/or the unique characteristics of a given airframe could very well present different spin characteristics.

Different, maybe...but...unrecoverable with the prop stopped? That sounds not good to me. If that's the case, then the plane should probably be placarded for no aerobatics, perhaps?

[skylor]

Originally Posted by Foxmoth

I am not saying the -7 will not recover, just that THIS -7 will not, I would be very interested if anyone else has had the prop stop on entry and the result! Recovery was initiated after 2 turns and took 12 and yes, a metal fixed pitch prop.



Engine stopped as I entered, I just closed the throttle, I think it was probably a combination of airflow, spin direction and mixture setting (at 8,500' with full rich and partially leaning meant this did not happen on subsequent spins)

I'm still trying to clarify your answer: When you say your plane won't recover with the prop stopped, was that using only the Finnegan method (neutral controls) , or did you try anti-spin control inputs as well (PARE)?

Skylor

[ronschreck]

Originally Posted by RV7A Flyer

Different, maybe...but...unrecoverable with the prop stopped? That sounds not good to me. If that's the case, then the plane should probably be placarded for no aerobatics, perhaps?

+1. If it were my airplane I would ground it. Something definitely wrong with it.