Elevator up-travel

[hotrodmac]

Hi all, relatively new member/owner here. I bought my ‘46 140, affectionately known as “Yellowbird” back at the end of August, and flew her halfway cross country from Oklahoma City to Charlotte, NC. It was a great trip, and I’m having a blast getting to know the airplane!

I have a question about up-travel on the elevator. When I come in to land three-point, I run out of up, and have a devil of a time breaking the glide to flare. I’m normally full flaps and full up trim. Not real sure on airspeed, because my ASI is screwy, and a whole nother topic. According to the association technical manual, up elevator is supposed to be set at 20 degrees. What is that measured relative to? I put a protractor on mine, and full up is 10 degrees relative to the the horizontal stabilizer. The up stop bolt is run all the way in, so I can’t change that. Any thoughts?

Also, it’s all I can do to get the airplane to break into a stall. Is this normal for the type, or possibly relates to my elevator setup as well?

[6643]

20 degrees is the angle between the chord of the elevator and the chord of the stabilizer. If yours is set to half that, I'm surprised you can get it to stall at all.

If yours is hitting the stop and the stop is all the way to the up end, then something ain't right. Maybe installed incorrectly, maybe the wrong part, or damaged. Is it possible the rear bellcrank could be installed backwards? I can't really imagine how you could otherwise loose half the travel...

[6298]

I agree that it should be 20 degrees up. Also, if you are using full up trim, it decreases the effectivity of the elevator. In other words the tab is down to force the elevator up, so the elevator lost some surface area flat wise.
When I was a 93 lb kid, I flew a Cessna 206 quite a bit. I found I had more elevator control for landing if I put the elevator trim in the down position. Gave me more elevator authority. With only one person in there it was nose heavy.

[6597]

Just to be sure, does your elevator horn look like this one?

[2066]

John wrote: " Is it possible the rear bellcrank could be installed backwards?"
I had not thought of that, but with a quick look I do see that it's a definite possibility...attaching holes will likely line up & it isn't symmetrical. Thanks for helping Lance with his super nice "new" 140, John, Randy & Dave! Now, I'm wondering, too, do you guys know if there may be any other models bellcranks that might have been "substituted" and that "almost" fit? Mac

[hotrodmac]

20 degrees is the angle between the chord of the elevator and the chord of the stabilizer. If yours is set to half that, I'm surprised you can get it to stall at all.

If yours is hitting the stop and the stop is all the way to the up end, then something ain't right. Maybe installed incorrectly, maybe the wrong part, or damaged. Is it possible the rear bellcrank could be installed backwards? I can't really imagine how you could otherwise loose half the travel...

Thanks for the input guys, I'll try to get to the airport tomorrow before it gets dark, no lights in the hangar. Didn't cross my mind that the bellcrank could be on wrong. Not sure how much I'll be able to see with the rudder installed, but I'll check it out!

L.

[2066]

IMG_1348.JPG (143.29 KiB) Viewed 7436 times

Push the rudder to the stop with your knee...still kinda difficult to see and "measure" (unless you have the rudder off & can view...as in Dave's pic of his incredibly clean tail post area ). There does seem to be a slight difference in profile and thickness and that just could be the issue as John suggests. Like most of our planes, that area has probably been R & R'd a few times over the years...easy to pick up a part & put it on wrong if it'd fit "backward"(?). Mac

[6597]

Here's what the parts book shows...

[2066]

CESSNA 140 BELLCRANK ELEVATOR EBAY 10 21 2019.jpg (23.44 KiB) Viewed 7400 times

Here's a photo (...Ebay)...hard to actually see how much dimensions are different up/down(?), but still assume that they are. ...also whether or not bolt holes line up either way, 'though it appears that they do(?). Could there be an issue with the forward push/pull tube and bellcrank that we're failing to consider? (The fact that Lance reports that the elevator up movement hits the stop bolt head certainly seems to indicate the issue @ rear, however.) ...just thinking out loud. Mac

[6597]

Check the bolts that connect the cables to the elevator bellcrank and thay they are not too long and hitting the side of the tailpost bulkhead where they enter.

Working on this plane today, notice that the castlenut/cotterpin needs enough clearance going into the bulkhead or you will lose quite a bit of travel.