PPRuNe Forums - View Single Post - PA-31 lost due to mis-installed trim tabs
Old 9th Dec 2021, 13:35
  #24 (permalink)  
Pilot DAR
Moderator
 
Join Date: Aug 2006
Location: Ontario, Canada
Age: 63
Posts: 5,623
Received 64 Likes on 45 Posts
The prevailing design requirement says:

Sec. 23.685

Control system details.

........
(d) Each element of the flight control system must have design features, or must be distinctively and permanently marked, to minimize the possibility of incorrect assembly that could result in malfunctioning of the control system.
But, that doesn't prevent it happening.

In addition to confirming the correct direction of motion of each flight control following any maintenance, it's also important to confirm the correct range of motion (travel stops and freedom). I've had a few post maintenance (and radio installation) planes where full control travel was not available - obstruction behind the panel. I also test flew a C 206 once (which I'd flown lots prior to the maintenance) with a serious mis rig. The elevator trim tab moved the correct direction, which I visually confirmed myself before flying. But, its travel stop limits had been reversed. Being as they are 5 and 25 degrees, I had 4 degrees where I should have had 25 degrees, and the nose up control force was barely manageable for a terrifying circuit. The maintenance manual for that 206 was somewhat ambiguous, later Cessna service manuals for the 206 are very bold about this, as I know I'm not the only pilot to blunder into this very unsafe condition.

So, if you're doing the first flight post maintenance, you would like the maintenance staff to demonstrate to you that the control and trim tab travels are all as per the type certificate data sheet specifications. If you're not sure, keep asking until you are, this is not complicated stuff!
Pilot DAR is online now