Elevator Deflection

[timbodine]

While at Oshkosh this year I was parked by several other 170's. I noticed that my full up elevator position was noticeably lower than the others. Returning home, I asked my A&P to look at it. Sure enough, the elevator should move 26' (degrees) up and 20' down. Mine moves 18' up and 28' down. Inspecting cables, bellcranks, brackets, etc. shows all is normal. The elevator bellcrank hits the stops at full up and full down. We can find no adjustment except the stop blocks that can be rotated to make small (1') adjustments. The rod (tube) that runs from the bellcrank to the elevator control horn has no adjustment, but is a different part number for 170, 170A, and 170B. My airplane is a 170B. Part # 051011-2 for the 170 and 170A and part # 051011-5 for the 170B. I am unable to find dimensions of these parts to determine if the 170B part is the same length. A longer rod would solve my problem. This airplane has flown like this for at least 20 years without incident. There is no mention of any changes in the logs. Does anyone have info that would help.
Thanks
Tim

[c170b53]

If not the rod is the aft bellcrank in the fuselage is installed correctly? Guess we need a measurement to help you out.

[FredMa]

Sounds to me that you have confirmed you have the wrong elevator control link installed. Find a source for the correct part you need 0510111-5 and have them measure it before you buy it. You may want to verify your part numbers again, I believe you left a 1 out. The 170 @ 170 numbers are 0510111-2.

[Bruce Fenstermacher]

I'd be looking to see if the turnbuckle barrel and eyes are the correct length called out in the IPC as well.

Thinking this process through you would set the stop blocks so the elevator had the correct travel. Then adjust the turnbuckles so the yoke and associated parts forward don't restrict the travel.

B model elvator rigging.png (122.82 KiB) Viewed 28455 times

Set the stops first. If you can't adjust the stops to get the required elevator movement then you have the wrong control rod length.

[timbodine]

Thanks for the replies. We had considered everything you have suggested. The cables and turnbuckle are correct. Cable tension is correct. The elevator bell crank (part # 36 in your diagram) is hitting both the up and down stop blocks, yet the elevator deflection is up 18 degrees and down 28 degrees. (Would be great for inverted flight!). It looks to me like the elevator push tube (part # 37 in the diagram) is too short, or the elevator control horn is too long (unlikely). If anyone has an elevator push tube (part #37) where it could be easily measured, I would greatly appreciate the hole-to-hole measurement. There must be a reason for the different part number for the 170B part (you would assume).
Fred, I believe you are correct. I left out a "1" in the part number.
Thanks.
Tim

[Bruce Fenstermacher]

So Tim what your saying is with the cables disconnected, you would be unable to adjust the stop blocks to achive the correct elevator through.

If this is the case then I agree the control rod might be to short. Or there is something else drastically wrong though I couldn't think what.

[c170b53]

Other than item #36 being installed 180 out vertically

[Bruce Fenstermacher]

Jim, I don't think you could install the bell crank upside down and still connect the control rod to it. The IPC only shows a hole on one end for the control rod but we know IPCs aren't always accurate.

[jlwild]

Tim,

I recommend you pull the elevator bellcrank stops (parts Fig.25-11 and -12 in 170B Parts Book) and rotate them to a different position. Then recheck the up and down elevator deflections with the bellcrank to elevator tube (Fig. 67-37) disconnected. I would start by rotating one bellcrank stop at a time to see what the different readings are for the up position first. This procedure may help you eliminate some of the potential problem areas.

While you are inside the tail cone doing this, see if the longer end of the bellcrank (Fig. 67-36) points up or down. This will address Jim McIntosh's concern mentioned above. I will take a look inside my plane tomorrow and see which direction the long end points.

Don't know if this helps but it's my two cents contribution.

[bat443]

Hi Tim,
I wouldn't start by trying to adjust the stop blocks as your total travel is correct and your error in up and down travel is approx 8 degrees. Each block has 4 choices that change the setting by about 1 degree, otherwise the up travel adjustment tolerance would be greater than +1, -0. Also having adjusted those on my 55 170B I would try to rule them out before I created a situation where I had to crawl back in the tail cone and work with both hands over my head and my head tilted back again. As for the bell crank part #36, it may be possible to rotate it 180 degrees about the vertical axis, changing the position of the push tube attaching hole forward. I would check that out for you, but unfortunately I have sold my 170.

Tim

ps: Are you sure you are starting with the elevator fared with the horizontal stabilizer and not level for the neutral position? Level for neutral would make for about the 8 degree error you have. I only ask because with only 18 degrees of up elevator I am not sure you would have enough elevator authority to make 3 point landings.

[timbodine]

All
I had not considered the possibility of the bellcrank being upside down. If one arm is longer than the other, and if it could be installed 180 degrees out, it could be the cause of my problem. I'll have to look at that next time I'm at the airport. The adjustment on the stop blocks is insufficient to solve the problem. I still wonder if I could have the 170 / 170A pushtube (part # 37 in the diagram) instead of the 170B. Since they carry different part numbers perhaps the 170B pushtube is longer. I've not been able to find a reference which shows the length of the pushtubes. This is one of those problems I wish I had not discovered. I've owned the airplane for several years without incident. It flies perfectly. Ignorance was in fact bliss.
Thanks
Tim

[bat443]

As you can see from this photo of the tail cone of my former 170B the push tube is centered in a hole in the bulkhead. I think if the bell crank were inverted that the push tube would no longer be aligned with the hole.

Tim

[c170b53]

Oh boy, what I'm trying to say... item #36 not rotated horizontally 180 as there's only one hole for the push tube connection at the top but rather turned vertically 180. As some have pointed out the stop blocks have (when rotated) limited travel limiting adjustment effect...so either it's the rod, the crank and as this owner stated he could see a visual discrepentcy between like models...I'll guess it's unlikely an error in measurement technique but sometimes we see what we want to see...so we need a tube measurement.

[marathonrunner]

I am not near a 170 to look at but do have access to the online parts manual. Is it possible to misalign the pylon? I mean are there extra holes and it could be that the elevators are installed wrong to the bellcrank so to speak where they connect together? Just a guess as it sounds like plennty of travel but if off by being installed incorrectly that would account for the travel and for how it is neutral and has that much up and down. Tha part number I am referring to in the 170B manual is 0534107 on figure 16

[marathonrunner]

What I am saying is I think you are at the wrong end of the problem. You seem to have the correct travel but if the elevators were connected to the bellcrank or pylon as it is called in the IPC and the wrong holes used then when faired with the horizontal stabilizer and going stop to stop you would get the wrong travel.