Running an Electric A H and aerobatics

[Dave Cogan]

I have put a R C Allen electric artificial horizon in my RV7a.
(Model RCA26AK-3).
It is fine with loops but topples on loops.
It has a knob that says "pull to cage".
I thought you might be able to lock it in the caged position but you can't.

Will it end up damaged from tumbling it during loops?
What if I pull the circuit breaker prior to aeros, would that protect it better?

Are there attitude indicators (electric) that allow you to fully cage it for aeros?

Any thoughts?

[Mark Albery]

I used to fly a DH Chipmunk with cageable gyros and it was always part of the HASELL check to cage gyros before manoeuvres. But that was early post-war technology. The gimbals can't allow a full 360 degrees of movement on all axes, so as soon as one hits its stop, then you will tumble it.

My preferred solution is the fibre-optic gyros in the latest AHRS systems. No moving parts, so no wear or damage from exceeding the limits. In principle they could be tumble free, but in practice you can exceed their response rates doing aeros and they will start to lag and need re-erecting.

[Mel]

I had one of these AH in my -6. I made a "lock" from a small piece of tubing that would snap around the shaft and hold the cage knob out. It worked fine.

[Doug Knab]

Dave
I had an RC allen electric gyro in my RV-6 and always caged it while doing acro. I made a U shaped device out of a block of UHMW that sliped over the Pull to cage stem. It worked great. I kept the gyro caged whenever it was not being used.

[AlexPeterson]

Your best solution is to turn it off. Clamping down a spinning gyro will put enormous loads on the bearings. Keep in mind it will spin for a long time after being shut down - you can listen on the ground to see about how long. Best is to not start it for those flights.

There is a "conventional wisdom" that says gyros do better during aerobatics when spinning. Bunk. That defies all physics, and I'm still waiting for a reasonable explanation as to why it could be the case.

[Mel]

While I agree with Alex that the gyro should not be running, it still needs to be caged. Otherwise it will still "bang" against the stops during acro.

[AlexPeterson]

Mel is correct.

Worst possible case: caged and spinning
Best case: caged and not spinning

My opinion is that the other possibility, not caged but not spinning is most of the way towards the best case. Hold a non spinning gyro in your hand sometime, and move it through motions simulating aerobatics at the same rate. Unless you are Sean Tucker or any of his copycats, the motions are quite mild.

[Dave Cogan]

Many thanks.
I will pull the C B prior to start up and make up a bit to hold the knob out.
Cheers.