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Andy

ADI Pilot II Alt Hold Servo

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Hi Guys,

 

I went out to launch on a cross-country flight only to discover that the altitude hold servo on my True Track ADI Pilot II autopilot would not totally disengage, even with the circuit breaker popped. (It showed up as additional friction in the pitch control check and some slight noise and vibration.) We are working around the problem by removing the control rod from the servo to the flight control system in addition to keeping the CB open. From looking at the aircraft records, the unit has about 360 hrs on it.

 

Has anyone else seen this kind of failure signature? Other than replacing the servo (including discussing this with True Track to see if they'll do anything about it), is there any other approach to fixing this?

 

Thanks.

 

Andy

2006 FD CTSW

N547AW

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Andy, can't tell how much feedback you're feeling when you move the stick but my TruTrak always gives a feeling of grainyness or vibration when I move my stick in both pitch and roll when the AP is not activated. When it is activated, you have a setting which governs the amount of torque the servos supply and this setting allows one to control the effort needed to defeat the servos when the AP is engaged. What you're feeling may be normal? Call the guys at TruTrak to get accurate information.

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Andy, can't tell how much feedback you're feeling when you move the stick but my TruTrak always gives a feeling of grainyness or vibration when I move my stick in both pitch and roll when the AP is not activated. When it is activated, you have a setting which governs the amount of torque the servos supply and this setting allows one to control the effort needed to defeat the servos when the AP is engaged. What you're feeling may be normal? Call the guys at TruTrak to get accurate information.

 

Same with mine. If you are felling lots of drag then you have a problem.

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Same with mine. If you are felling lots of drag then you have a problem.

I know what you are talking about, and this was definitely abnormal. I've flown it enough with the autopilot engaged and not to know the difference, and the mechanic confirmed that the servo wasn't letting go. Does't look right now like anyone else has seen this problem.

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Servos do go bad and may need to be sent into the Mfg.

Yeah, that's the next step. My A&P thought it'd be a good idea to talk it first here to see what would pop up. I appreciate everyone's comments and will post my progress and resolution here, just in case it might be helpful.

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Servos do go bad. They can be anything from stiff controls, won't engage or release and hunts for position even after the torque is set. The other thing is if you hear what sounds like morse code in your headset send in the altitude hold servo to get fixed.

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Servos do go bad. They can be anything from stiff controls, won't engage or release and hunts for position even after the torque is set. The other thing is if you hear what sounds like morse code in your headset send in the altitude hold servo to get fixed.

Somewhat good news on the servo front. Had to delay the repair because of a couple of trips (one in the CTSW) but we removed the servo this morning and I got an RMA (Return Material Authorization) number from TruTrak and shipped it off. I spoke with their tech supervisor Lucas who said that their out of warranty repairs were flat rate and $200, which covered a complete rebuild and came with a one year warranty. So, now I'm just waiting until it gets back...

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What GREAT service from TruTrak! I didn't think a $200 was bad at all, but I found out this morning they repaired the servo for free (noting that there may be charges next time..which hopefully won't be for a long time) and only charged me for the shipping. Just waiting to get it back now and put it back in!

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One more note..I thought this might be of interest to some...I found a repair description on the packing list enclosed with the returned unit. It stated:

RECEIVED WITH: Shear screw broken upon arrival

CLAIM: UNIT HAS HIGH DISENGAGED RESIDUAL TORQUE

Claim CONFIRMED- Bad servo amp

Work performed: Installed new servo amp for blue motor; installed new amp case and cover; installed new shear screw; bench test within specifications.

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