Elevator trim adjustment problems?

[canav8]

Rigging is done with elevator faired. End limits if I remember are measured with full deflection in both directions. the reason why you rig with the elevator in the faired position is to get the threads correct for full deflection limits. If you take it apart and play with it, it is easier to understand what we are trying to type. D

[GAHorn]

The elevator trim tab is set with the elevator in the NEUTRAL position. Here are the instructions for rigging:

8. ELEVATOR TAB

(a) C-170 & C170A
1. The elevator tab is actuated by a cable which has a chain incorporated in each end. The chain in front is actuated by the fingertip tab control, and the one at the rear operates a screwjack, which mounted in the right half of the stabilizer. The travel is 10 degrees up and 27 degree down plus or minus 1 degree.
2. Turn the tab control wheel to the full forward position, and the screwjack to the full up position. Then turn the screwjack back ½ turn. Set the chain on spockets at each end, allowing ½” to 1” overlap in the direction of travel. Tighten the cable tension to approximately 30 lbs.
3. To set the tab travel the elevator must be in neutral position.
4. Turn tab control to full forward position, disconnect the push-pull tube from taband adjust it to hold the tab approximately 11 degrees. This can be done by screwing it in or out. Connect the push-pull tube to the tab and turn the tab control to the full rearward position. The tab should be approximately 28 degrees.
5. Set the stops between first and second bulkhead rear of the baggage compartment on the cables for correct travel, which is 10 degrees up and 27 degrees down.


(b) C- 170B
1. The elevator tab is actuated by a cable which has a chain attached to each end. The chain in front is actuated by the fingertip tab control, and the one at the rear operates the crew jack, which is mounted in the right half of the stabilizer. The travel is 12 degrees up and 25 degrees down, plus 1degree or minus 0 degree.
2. Turn tab control wheel to the full forward position and the screwjack to the full up position. Then turn the screwjack back ½ turn. Set the chain on the sprocket at each end, allowing ½” to 1” overlap at each end in direction of travel. Tighten the cable to approximately 30 lbs.
3. To set the tab travel the elevator must be in neutral position.
4. Turn the tab control to full-forward position, disconnect the push-pull tube from the tab and adjust to hold the tab at approximately 13 degrees. Reconnect the push-pull tube to the tab and turn the tab control to the full rearward position. The tab should be approximately 26 degrees.
5. Set stops between the first and second bulkhead rear of the baggage compartment on cables for correct travel, which is 12 degrees up and 25 degrees down.

[MoonlightVFR]

What a wonderful question.

This is the essence of what the cessna170.org forum is all about.

Just think, a 60+ year old aircraft design, older than most GA pilots, and the end user owners are able to discuss the finer points of rigging flight controls.

C170; perhaps the best all metal single engine aircraft ever!

Happy Landings

[mdpesky]

With elevator faired my measurement following the settings listed in the operators manual was set up at 13 degrees. Unfortunately we did not measure the up trim before we disassembled the tail. Now clearly I'm finding for wheel landings this 13 degrees is not enough, expecially the more flap you add even with the C of G dead centre of the envelope. One member PM'd me and advised he found his at 18 degrees and is very happy with how that works!

My question is, can other members please measure their aircraft max up elevator trim tab and advise even by private mail what measurements they find their aircraft set up at? I highly suspect the 13 degrees is incorrect and that there must be some other written instruction that contradicts what the Opertaor Manual states????

Someone out there must have some experience on this, who would that be?

All help appreciated.

[n2582d]

Could it be that your Horton STOL kit affects your plane's landing attitude as the cord line has been modified? It would be interesting to compare it to other 170's with STOL kits.

[ghostflyer]

Most ipads have a feature [App] of "measurement" and in this App there is a item called "handy level". I use this a lot of the times when doing a quick level check on a aircraft . I carry my ipad at all times. We checked the pads accuracy on a Flat bed used for calibration of tooling and its spot on .tried other ipads with the same result.

[daedaluscan]

If you swipe right on the compass of an iphone there is an inclinometer.

[mdpesky]

Thank you all for the great feed back. We are certainly baffled by this change in trim characteristics since removal of the tail. Being there is no horizontal stab adjustments and that it went on exactly like it came off we are stumped by the shortage of forward(up trim tab) adjustment, even though we do have the required 13 degrees as called for in the operators manual.

This does raise concern that somehow through all this process the horizontal stab position did get changed but so far we are unable to determine what that change/difference is?

The comment regarding the installation of the STOL kit makes total sense, the only offsetting argument is I flew it for 20 years with the STOL kit and never had the issue, then again we have no idea what the original up trim setting was before tail removal?

If other members would continue to verify their up trim settings it would be interesting to see how consistent the data is. Secondly, if any members have any experience with such issues I'd sure like to hear about it, perhaps someone is aware of a potential error in horizontal stab installation that could happen we missed???

Once the issue is resolved I will certainly post the findings for all. Thanks again to all for the great feedback, please keep it coming.

[hilltop170]

I have not heard of any horiz stab incidence changes on the C-170. However, I have seen and measured a difference of 5/8" in the leading edge of the horiz stab on early vs late C-195s. According to Mort Brown, Cessna production test pilot, the production line was physically moved to a new location late in the production run and the millwrights did not properly survey-in the fixture in the new location which caused the horiz stab incidence to be off a little. I'm wondering if the C-170 line was moved at the same time?

[johneeb]

Mark here are some pictures you were asking for. They trim tab is as close to book as I could make it when I did the restoration. The airplane flies nice with these settings and I do not have any problem with having enough elevator however (like you I do have a stol kit) we are not a good comparison as I do have an anvil in the engine compartment.

Angle of faired elevator

elevator faired.JPG

Angle of elevator trim tab faired to faired elevator

elevator trim tab faired (0 degrees).JPG

Trim indicator to faired elevator trim tab

0 turns elevator trim.JPG

Elevator trim tab full down (12 degrees)

elevator trim tab full down (12 degrees).JPG

Trim indicator with full down elevator trim tab (1.25 turns from 0 degrees)

1.25 turns dwn elevator trim.JPG

[johneeb]

Elevator trim tab full up (26 degrees)

elevator trim tab full up (26 degrees).JPG

Trim indicator with full up elevator trim tab (3.75 turns from 0 degrees)

3.75 turns up elevator trim.JPG