Aces High Bulletin Board

General Forums => The O' Club => Topic started by: Manedew on August 27, 2003, 11:14:20 AM

Title: Trim Causeing crash
Post by: Manedew on August 27, 2003, 11:14:20 AM

http://www.capecodonline.com/cctimes/pilotcited27.htm

Never heard of this .. Would some RL pilots like to give some info about "runaway" trim?

Poor fellas :(

Title: Trim Causeing crash
Post by: AKWeav on August 27, 2003, 11:18:31 AM

I believe that Alaska Airlines crash a couple of years ago was due to trim malfunction. Something about improper grease to lube the jack screw.

Title: Trim Causeing crash
Post by: GtoRA2 on August 27, 2003, 11:20:24 AM

It used to happen on F4u-5 corsairs, since they went to electric trim tabs on that model, the connectors would corrode, and then you trim nose down the connection sticks and then your in trouble.

Title: Trim Causeing crash
Post by: funkedup on August 27, 2003, 11:34:08 AM

Quote

Originally posted by AKWeav
I believe that Alaska Airlines crash a couple of years ago was due to trim malfunction. Something about improper grease to lube the jack screw.

Yep when you don't lube a ballscrew properly, they fail.  I believe the trim on that plane "ran away" first and then eventually the nut seperated from the screw.  After that they were just passengers.

Funny thing is that the organization I used to work for was responsible for the design of the original DC-9 trim actuator.  Another company outbid us to build our own design on the MD-8X/MD-9X/717 so it was out of our hands long before this accident happened.

Title: Trim Causeing crash
Post by: nuchpatrick on August 27, 2003, 11:39:17 AM

What happened to The Alaska A/C was a failure of the shaft that (looks like a screw) failed due to material quality the Elevator because usless. Trim tab's were not a issue in that crash.


Scary way to go..

Title: Trim Causeing crash
Post by: Waffle on August 27, 2003, 11:52:27 AM

Quote

Yep when you don't lube a ballscrew properly, they fail.

Had that happen a few times.........

Title: Trim Causeing crash
Post by: Dinger on August 27, 2003, 12:14:58 PM

Out-of-trim conditions can be lethal.  Not all of them are caused by mechanical malfunction. I think it was on a china airlines A320 a few years back where the pilot on approach threw the wrong lever and kicked the plane into Go-Around mode.  Threw hte lever back and tried to continue the approach.  The plane thought otherwise and continued to apply up trim to override the pilot's inputs, until it succeeded.

Title: Trim Causeing crash
Post by: funkedup on August 27, 2003, 01:19:34 PM

Quote

Originally posted by nuchpatrick
What happened to The Alaska A/C was a failure of the shaft that (looks like a screw) failed due to material quality the Elevator because usless. Trim tab's were not a issue in that crash.


Scary way to go..

It wasn't material quality, that caused the screw failure, it was improper lubrication.

Title: Trim Causeing crash
Post by: udet on August 27, 2003, 02:33:08 PM

I fly a 152, most of the time I don't need to use trim :)