mfleming

mfleming

Well Known Member
Patron
I'm posting this because it surprised me on how easy and incipient it was. These RV are slippery...I know this and you know this but when it happens it can happen without warning.

Here's a link to a flight I made this morning. Headed to the WAAAM Museum for their annual Fly-in. Level at 8500', cruising at 163 KTAS and on the autopilot. The smoke has been bad in Oregon and on this flight it was OK until it wasn't. Decided to descend from 8500' to 6500' and do a 180. The autopilot was commanded to descend at 500'/m. After telling center that I was reversing course, I switched from NAV mode to heading mode and punched in 080°. The AP started a turn to the right and continued to descend. I'm flying VFR so my eyes are outside, not much of a horizon and I didn't notice that the bank angle was increasing and the autopilot was struggling to follow the flight director. Just as I noticed the upset, the airspeed warning started annunciating. Autopilot off, wings level and raise the nose...already too late, Vne busted!

Move ahead on the timeline until about 07:43 that's when I commanded the AP to descend. At about 07:45:50 I command the AP to fly 080°. It's all over about 07:48
 
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That is scary!
My only suggestion is to be religious about your scan beyond just traffic. Yes, head outside, but don’t forget about scanning your instruments. A panel scan might have given you a clue in time to question what’s up.
Look on the positive side, you passed a flutter test ;) .
No harm no foul. Now time to dig into what’s up with that auto pilot!
 
Thanks for the write up. You made the Mach club. I used to reduce the RPM by 200-300 prior to descend when using the autopilot. Not sure if this is the way to do it but I guess it is muscle memory from flying non-autopilot airplane.

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By the way, good call on turning back. Visibility from smoke can change really quickly and unpredictably.
 
mfleming said:
I'm posting this because it surprised me on how easy and incipient it was. These RV are slippery...I know this and you know this but when it happens it can happen without warning.

Here's a link to a flight I made this morning. Headed to the WAAAM Museum for their annual Fly-in. Level at 8500', cruising at 163 KTAS and on the autopilot. The smoke has been bad in Oregon and on this flight it was OK until it wasn't. Decided to descend from 8500' to 6500' and do a 180. The autopilot was commanded to descend at 500'/m. After telling center that I was reversing course, I switched from NAV mode to heading mode and punched in 080°. The AP started a turn to the right and continued to descend. I'm fly VFR so my eyes are outside, not much of a horizon and I didn't notice that the bank angle was increasing and the autopilot was struggling to follow the flight director. Just as I noticed the upset, the airspeed warning started annunciating. Autopilot off, wings level and raise the nose...already too late, Vne busted!

Move ahead on the timeline until about 07:43 that's when I commanded the AP to descend. At about 07:45:50 I command the AP to fly 080°. It's all over about 07:48
Click to expand...
Good catch.
Have you set Max and minimum speed in your A/P settings? Most A/P have the max and minimum airspeed but it seems something serious has gone wrong in your A/P as at some point you had nearly 4000 fpm descend rate.
 
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in addition to airspeed limits there are bank limits to set. at a minimum, it certainly looks like you need to go through the A P tuning procedure that Dynon publishes. If you can‘t pass that there is a problem with the installation or AP.
 
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