Trim tab position in level flight on a 7A

[hecilopter]

Just wondering if anyone has noticed their trim tab position in level flight. I have always needed some down trim for level flight. On my Ray Allen trim indicator, I am 1 line of down trim above neutral. I left the trim alone after landing and verified that I have about 3/16" of down trim (trim tab up) as viewed from the trailing edge of the elevator. Is this normal for a -7A, constant speed, 180 HP O-360? It is like this whether it is me only or 2 people and full fuel or partial fuel. My CG worked out almost exactly in the middle of the range in the plans (slightly forward).

Thanks for replies, just curious.

 

[Walt]

I have almost the identical configuration on my 7A and my tab is within 1/16" of faired. I'm one of those guys who never trims for landing so I know exactly where it is all the time and it varies very little from perfectly faired. Just got lucky I guess!

 

[pierre smith]

Yes

Hi Rusty,
My 6A with an 0-360 and Catto three blade has a slightly down elevator in cruise and I asked the same question. The replies were "Yes" and that the manual says so as well. I didn't notice the trim tab as much as I did the elevator counterbalance by looking over my shoulder in flight.

As you probably know, a rearward biased airplane is faster than a nose-heavy one. Reason is simple.....the down elevator is carrying some of the load, freeing that amount off the wing and allowing a lesser angle-of-attack. An "up" elevator condition is pushing down, adding to the load that the wing must carry, slowing you down. When I can, I load to favor a rearward CG condition but keeping it within limits.

Why do I have a feeling that I'm starting some s***?

 

[robertahegy]

Trim for level flight is going to change with loads such as passenger, fuel and baggage, so, what might appear perfect under one condition may be slightly different with other load scenarios.

Walt, I'm curious why you would not trim for landing. Sure makes for lighter stick forces and easier to keep the nose wheel up when trim is used.

Roberta

 

[Walt]

I don't trim for landing...

Walt, I'm curious why you would not trim for landing. Sure makes for lighter stick forces and easier to keep the nose wheel up when trim is used.

Roberta

For a couple of reasons. Main reason is I don't feel it's necessary as the control forces are just not that heavy with cruise trim still applied. Second reason is I practice very short approaches on almost every landing so there is no time to trim. I kill the power abeam the numbers, turn base as the speed comes off, flaps start down and keep turning to final. Flaps full out and land without adding power (if I have to add power I miscalculated), so basically I do a 180 degree turn from downwith to landing. I do prefer a little stick pressure on landing for a better feel of the airplane and I have no trouble holding the NLG off with cruise trim. I usually let the NLG gear come down when she won't stay off any longer to avoid letting it "skip" when there is not enough elevator to keep it off any longer.

 

[cytoxin]

o k now i m curious

doesnt the trim reduce the load on all of the control linkages.in the unlikely event something were to break with no trim applied wouldnt you then be aikin to do a nosedive/pitchup. i know this is stretching it but thats how i operate

 

[Walt]

When I have to start worrying about....

my controls breaking then I need to sell the plane! If you build it right and do good maintenance then this is not an issue (maybe I should practice my loops and rolls using only trim so as to stress the controls to much) But really, it's not like I have both feet up on the panel pulling for all I'm worth, I could probably hold the back pressure with 2 fingers!