Elevator Deflection

[c170b53]

The answer to the secret of the universe is 29.25 for a "B" hole centres. I'll post a pic of install in question but safe to say they madeit almost fool proof

[n2582d]

The answer to the secret of the universe is 29.25 for a "B" hole centres. I'll post a pic of install in question but safe to say they madeit almost fool proof

Jim,
I must live in an alternate universe! My pushrod from a '52 170B measures 29.125" between hole centers. I also have a pushrod that I got from Don Harrell which measures 28 9/16" between the centers of the holes. You're right -- It is virtually impossible to get the installation of the bellcrank reversed. The hole circled in red is for one of the control cables. Notice that if one flipped this 180 degrees on the vertical axis the control cable attachment would interfere with the flange on the bellcrank. It appears that the only thing asymmetrical about this is that the flange is shorter on the forward edge than the rear edge.

Click to enlarge

[marathonrunner]

I still think that he has the correct travel overall but, if the elevators are attached incorrectly at the tail to the bellcrank, if this is possible, then you get the movement he has. I just wish I was somewhere where I could visually verify this. No 170's where I am currently located.

[n2582d]

I still think that he has the correct travel overall but, if the elevators are attached incorrectly at the tail to the bellcrank, if this is possible, then you get the movement he has. I just wish I was somewhere where I could visually verify this. No 170's where I am currently located.

It seems clear to me that he has p/n 051011-2 (the pushrod for the C-170A) installed where he should have p/n 051011-5 (the pushrod for the C-170B) installed. His pushrod is around .5625" too short. This would account for getting too much down travel and not enough up travel.

[Bruce Fenstermacher]

It seems clear to me that he has p/n 051011-2 (the pushrod for the C-170A) installed where he should have p/n 051011-5 (the pushrod for the C-170B) installed. His pushrod is around .5625" too short. This would account for getting too much down travel and not enough up travel.

Where have we established the length of Tim's pushrod currently installed? We have Jim's, and Gary's not Tim's.

[Bill Hart]

I may have missed something in an earlier post but my IPC for an A model shows this as a 0510108 part number.

[n2582d]

I may have missed something in an earlier post but my IPC for an A model shows this as a 0510108 part number.

Bill,
I was copying Tim's p/n's in his original post. I think p/n 0510108 you wrote of might be the front pushrod which connects to the control tee. Now in looking at the IPC it appears that Tim and I left out a "1" in the part number. For the C-170 and C-170A the correct part number for the rear push-pull tube is 0510111-2 (See fig. 43-10 for the C-170 and fig. 47-2 for the C-170A). For the C-170B the correct p/n is 0510111-5. (fig. 67-37).

[n2582d]

Where have we established the length of Tim's pushrod currently installed? We have Jim's, and Gary's not Tim's.

If I was an engineer I would say, "Elementary, my dear Watson." Unfortunately I'm not an engineer. But wouldn't it be easy to figure out the length of Tim's pushrod without looking at it? His travel is 8* less at the top and bottom of the travel than what he should have. The arm of the control horn on the elevator is roughly 6". The arm on the rear elevator bellcrank is around 5.87". How much too short is Tim's pushrod?

[timbodine]

Again, thanks for all the good info. Measuring the length of the pushrod while it is installed is not as simple as you would think. I'll try it again tomorrow with some help. I'm convinced that the length of the pushrod must be the problem. I see no way to incorrectly install any of the components in the tail. Everything forward of the elevator bellcrank is functioning correctly in order to allow the bellcrank to strike the "up" and "down" stops. The problem must be the length of the elevator pushrod. The approximate 1/2" too short that Bruce estimates is what I also estimate. From your measurements, it appears a "B" pushrod should be 29.125" to 29.25". I'll let you know what I find.
Tim

[marathonrunner]

If the elevators cannot be misaligned with another hole...I have seen that before on other aircraft, then the rod seems to be the only other culprit. Umm it is pretty easy to remove and if it is wrong has to be removed anyway. Then you can get a very accurate measurment

[timbodine]

Sorry, but I just don't see how the elevators could be misaligned with another hole. What other hole are you referring to? In which part?
Tim

[timbodine]

Back to the airport today. Re-measured everything. My elevator pushrod is 29 3/16" between hole centers. Looked at 2 other 170's (A models) on the field and cannot find anything different with my 170B, except the elevator deflection. So, the problem is not the pushrod. We will now do a thorough search of the logs and any 337's to see if there was damage to the tail at some point. Someone suggested there may be an L-19 (Bird dog) part in the mix. I don't have any sources of info on the L-19. I know they are basically a 170, but I don't know how (or if) they were changed in the tail area. This airplane has been flying like this for at least 20+ years.
Thanks again for the help and advice. I'll post here if I find the problem.
Thanks
Tim

[canav8]

Tim, I had the same travel problem. The problem is in the trim system not the elevator. Go through the entire trim system rigging first. The jack screw is not being centered on its throw. The jack screw should be equal number of turns out as in. It is hard to explain and I am not near the aircraft to take any pictures. If you release the trim on the elevator you should be able to get full throw. It took me a while to figure it out because there is nothing on the 100 series manual on this but I had a restricted up elevator travel also when I bought the 170. Have a look there after you put your aircraft back to gether. I will check back here in a couple days. I am in Miami and the airplane is in Las Vegas. You can call me if you want to talk or maybe someone on here can also discuss this phenominon. (Seven zero two)499- 498Niner. Doug

[timbodine]

Doug
Thanks. I've forwarded your comment to my A&P. I don't really understand how the trim could affect the elevator throw, but we'll take a close look at it in a few days. I live about 50 miles from the airport and can't get there every day. I'll get in touch if we have any questions. We are pretty frustrated with it right now.
Tim

[c170b53]

Tim and Doug, I was thinking the problem was an aft bellcrank/ aft bulkhead problem as I was thinking that your deflection measurements were made with the aft bellcrank against the stop. If that's not the case then we're going to need more darts.