Autopilot Settings for an RV10
Having replaced the cracked capstan and working with David Brown to tune the autopilot, I can report that the autopilot is now performing outstanding with only a half bar-width deviation on final approach. David and I now have almost identical settings, having come from different directions.
SOLUTION:
- • Slop must be removed, as you know.
- 1. Mine was coming from a cracked capstan.
- 2. Thank you to Steve who told me to set the autopilot on “level” and manipulate the elevator. That’s how I found the cracked capstan (it was so simple).
- • There are two important trim settings that must be addressed before dealing with autopilot settings (thanks to David Brown for identifying these and getting our two planes on the same page):
- 1. The trim tab set up should be checked and set according to the procedure posted in Matronics on 2006.
- 2. The TRIM speed settings must be right to allow the autopilot auto-trim to be fast enough and not fight the autopilot. The settings David gave me (for both pitch and roll) are:
- ♣ 105 Kts – 100%
- ♣ 130 Kts – 35%
- • Then I re-ran the in-flight tuning (for the millionth time), resulting in sensitivity 13, pitch gain 1.5, altitude gain 0.9. This was fine enroute, but terrible on LPV glide slope (VNAV setting).
- • Finally I flew many LPV approaches, testing pitch sensitivities from 13 to 20. For each, I would then test pitch gain until I found the maximum gain that would fly an approach without any oscillations. To do that, I would push the stick to try to induce oscillations at each gain setting. Pitch sensitivity of 17 worked best for me, with a pitch gain of 1.5, and altitude gain has been set at 0.9 from the tuning results. All other numbers are default. David is now at 16, 1.5, 0.9 (only one digit off); he is planning on trying my settings 17, 1.5, 0.9. Nonetheless, we were very far apart and now we are almost identical in our settings.
OBSERVATIONS:
- • The autopilot is a completely different animal as soon as VNAV engages, so flying some VNAV coupled LPV final approaches is a necessary part of in-flight tuning.
- o Meeting the in-flight tuning criteria alone results in a sloppy coupled approach
- o Setting the autopilot pitch just short of “twitchy” (in in-flight tuning) results in a rough, oscillating coupled approach.
- • FYI, the in-flight tuning guide IAS Hold Procedure does not allow the possibility of reducing pitch gain below 2.0! This is because the default (starting) gain is 2.0, and the flow chart never suggests a reduction in gain!
Here are the settings David and I are using:
Dynon default Rick David
ROLL
sensitivity 10 14 14
gain 0 0 0.3
PITCH
sensitivity 10 17 16
gain 2 1.5 1.5
altitude gain 0.6 0.9 0.9
pull rate 1 1 1
VSI gain 1.5 1.5 1.5
g-error gain 1 1 1
g-error limit 0.25 0.25 0.25
Rick Solana
RV10, N804RS
