Adahars Failure?

[resojames]

On my last flight in my RV 6 the autopilot started going crazy in pitch. During experimentation I found the pitch bar would show as much as 15 deg of nose up pitch when the plane was in fact pitch level as indicated by back up indicator and visual cues. This happened a number of times and then it would go back to normal indication. Airspeed and bank indication worked fine. The autopilot has worked fine for 2 years so I don't think it is a A/P problem. Is there anything other than adahar failure that can cause this?

 

[resojames]

Thanks for the reply. That sounds pretty similar to my problem. I fly a fair amount of IFR so it is some what concerning. I do have a independent back up indicator, but I could see how this could be exciting in actual. I am waiting to hear from Dynon to make sure I am not overlooking something.

 

[Marc_J._Zeitlin]

Thanks for the reply. That sounds pretty similar to my problem. I fly a fair amount of IFR so it is some what concerning. I do have a independent back up indicator, but I could see how this could be exciting in actual. I am waiting to hear from Dynon to make sure I am not overlooking something.

For VFR flying, ADAHRS failures are a Minor failure. For IFR/IMC, they are a Major failure (and I use "Minor" and "Major" in the System Safety Analysis meaning, determined by severity of the failure).

You don't note what type of "independent back up" you have, but this is why having two ADAHRSs is necessary when flying IMC - with two Dynon ADAHRSs, you'll get an ADAHRS miscompare error message if they're saying different things, and then you can use the rest of your instrumentation (IAS, altitude, VSI, T&B, etc.) to determine which one is correct, then tell your system to use the correct one.

I've had that happen once (in VMC) - one ADAHRS thought I was in a 10 degree bank when I was straight and level. The 2nd Dynon ADAHRS was correct, as was the Garmin G5, so I switched to ADAHRS #2. ADAHRS #1 needed to be sent in for repairs.

 

[CanardMulti]

I 100% agree w/ Marc.

If flying IFR, dual ADHARS is a must for safe operations. I consider a standby ADI, such as a G5, a D10, a D30, or similar to be essential as well. There needs to be a referee to as to which of your disagreeing ADHARS is telling the truth in a timely manner.

An IFR setup with just a single ADHARS and a standby ADI sounds good at first and is certainly better than no backup, but IMHO it could lead to a false sense of security. A subtle progressive failure of your one and only ADHARS while in IMC could easily lead to spatial disorientation at best, and departure from controlled flight at worst, before the necessity to recover on the standby ADI becomes apparent to the pilot.

Ken

 

[porterjames]

I also agree 100%
I had a failure in MVFR. I have since installed a second Dynon unit.
I point out that the failed ADAHRS drives your Autopilot, and even if you have a backup instrument, unless you have it driving your autopilot you will have to hand fly the airplane.
Installing a second ADAHRS is fairly simple and the second unit is a little cheaper than the primary unit.