Elevator trim tab?

Haydon · Post by **Haydon** » Thu Apr 05, 2007 6:06 pm

Howdy All,

The annual is due on my '49 170A at the end of the month. I have noticed for awhile

, that the trim tab on the elevator had a little play in it. I did not think much about it....until I read that the tab can "flutter" and cause control problems....This a problem ! Further inspection of the horn on the tab indicates that the bolt and nut are secured properly. The "play" in it seems to be from an elongated attachment hole in the "control horn". (not you George

) It has been suggested to me to drill and place a bushing in this elongated hole. This seems to be ok to me. Is this a proper repair? Is this a common problem in our old planes? Advice and suggestions would be much appreciated. Thank you....

Richard.....

Post by **GAHorn** » Thu Apr 05, 2007 10:20 pm

Bushing the the elevator tab is one way to make the repair. Another is to fabricate a new control "horn".
(I am out-of-control...or hasn't anyone noticed?)

HA · Post by HA » Thu Apr 05, 2007 10:34 pm

it would have to be a lot of slop to flutter at the breakneck speeds these machines attain

but it will only get worse as it works and elongates more, so you should fix it

an oversize bushing is easy and good, but (gasp) not approved that I know of unless offered by Cessna in a kit. of course the proper way to fix it is a new part if you can find or fabricate one.

late night sims George?

Post by **GAHorn** » Thu Apr 05, 2007 10:41 pm

Ha, HA.

(You must have noticed the time-stamp on some of my recent posts.)

Haydon · Post by **Haydon** » Fri Apr 06, 2007 2:33 pm

Thanx for the info....repair in progress.....Richard.......

pdb · Post by **pdb** » Sat Apr 07, 2007 6:45 pm

HA wrote:it would have to be a lot of slop to flutter at the breakneck speeds these machines attain

but it will only get worse as it works and elongates more, so you should fix it

Scariest flight, bar none, that I ever had was on an old 65HP T-Craft. I had just taken off from Merrill Field in Anchorage headed south when all of a sudden, the control wheel started slamming in and out of the panel.

It was moving so hard that I could not control it and I had no idea what was going on. I tried to jam my arms in a way to stop it but I wasn't strong enough. I felt like a jack hammer was connected to the wheel.

I slowed up immediately just above the stall and it abated somewhat but I still could not stop the control wheel from bouncing in and out. There was a small field, O'Malley air strip, straight a head and I went in immediately, fully expecting the back end of the plane to snap off before I got there.

I landed, pulled over and got out, seriously considering taking up golf. I was that scared. After, more than 30 years, I am still embarrassed about that (the golf business, not being scared.)

The push rod to the elevator trim tab bad just broken off, fatigued. It had apparently caused flutter in the whole elevator. Very, very bad news indeed.

Fixing this is a good iead.

cfiatzph · Post by **cfiatzph** » Tue Apr 10, 2007 5:05 am

Flutter is'nt a joke. I had a Seneca I flew 135 for. A few months prior to starting the season they removed the de-ice boots and painted the stabilizer. One day I took of (135) 1/4 and about 300 overcast. Upon rotation the whole damn airplane started to shake, I delcared a emergency and did a ILS on about a 2 mile final, I really thought I was going to lose the tail. Alot of stuff to add but the mechanic that had been "laid off" called me and told me about how he kept tell them that hte hinges and the tail were a little toooooo loose. A 170 is a different animal but still when it happens it will get your attention. The other suspect was that when painted since I flew in rain alllll day long that day that because of the de-ice boot and the paint they thought that that the painting may have covered "some" of the drain holes. I still have nightmares about this. Give me any scenerio but not a tail coming off! When this happened I had a copilot with twice the time in the Seneca and she just froooze. We kept looking at each other and asking whats that noise? Why is the a/c shaking? She looked back and saw the tail and said, look! It took about 2 secs to turn around and declare a emergency! I don't think you could talk a 170 into doing (speed) it but if you did, you'd probably never want to fly one again!!!!

Post by **GAHorn** » Tue Apr 10, 2007 6:12 am

Where did I recall in my studies that 160 mph (140 kts) is the speed above which even slight imperfections in flight controls becomes critical? (Moral: stay away from high speeds in old airplanes with worn flight controls. Do not "pulse" flight controls at high speeds.)
Anyone who has taken a 170 up to redline will hopefully recognize the needlessness of the excersize.