Trim elevator on landing or not

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plowboy
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Trim elevator on landing or not

Post by plowboy »

I saw on another post a Maule flyer bragging that as he had full down trim on the elevator it worked like a flap hanging down. I have also heard that one is not to use the trim tab on landing as it looses you elevator surface at low speed, just when you need it most. So from the experts here which is it, adjust the trim on landing or muscle it.

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andy
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Re: Trim elevator on landing or not

Post by andy »

The problem with using trim on landing is that you will run out of elevator effectiveness just when you need it. I set my elevator trim for level flight in the pattern and don't touch it after that. It requires a little muscle but not long enough to tire you out.
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drak130
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Re: Trim elevator on landing or not

Post by drak130 »

I am by no means an expert. I fly a M7-235 so it tends to be nose heavy when flown solo. As speeds slow enough to 3 point and trimmed for 55mph i would indeed run out of elevator effectiveness. Following advice from other on this site I roll the trim to the takeoff mark on final with much better results. I think someone else said like 1/2 inch nose up from the T/O mark. Wheel landings at a higher speed and less of a pitch change required may not need this technique but i still do it as part of my habit pattern.

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andy
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Re: Trim elevator on landing or not

Post by andy »

My MX-7-180 isn't as nose heavy as a 235 hp but the tail on all Maules is heavy and doesn't produce any lift, since it's not an airfoil shape. Elevator effectiveness is due to air pressure differences on the top and bottom of the horizontal stabilizer. When I slow down on final to 55 or 60 mph, the tail wants to droop. If I applied nose down trim to compensate, then the elevators would deflect down. When the mains touch down, I quickly apply forward yoke to bring the nose down, reduce angle of attack and keep from bouncing. If the elevators were already at or near their downward deflection limit, I wouldn't be able to bring the nose down and I would bounce. The geometry would be slightly different in a 3-point landing since I wouldn't move the yoke forward after touchdown. If the nose was heavier, like it is with a 235 hp engine, then the tail wouldn't droop quite so much on landing and I would need less nose-down trim. But the problem would still exist for a wheel landing. The tendency for the tail to droop is also aggravated by the downward deflection of air from the tailing edges of the high-lift wings onto the horizontal stabilizer. Using full flaps on landing increases the downward deflection of the air.

The weight of the tail and downward deflection of air onto the horizontal stabilizer can be compensated by making a shorter, steeper approach. It takes practice to determine where to start the descent to landing on a short, steep approach. It's affected by wind and weight. The heavier you are, the closer you need be to the touchdown point due to a faster rate of descent. You might need a shot of power to arrest the descent rate for touchdown to avoid a hard landing. If there's a headwind, you'll need to be closer to the touchdown point and you'll need more power to maintain your aiming point.
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wtxdragger
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Re: Trim elevator on landing or not

Post by wtxdragger »

I have a long wing M7-235 with the 3 blade MT and I'm in the trim for level flight and leave it alone until takeoff school.

From this trim setting it's not a problem to 3 Point or Wheel land as the need arises.There is a bit of pull on the Yoke needed to maintain stabilized descent, and at first it seems awkward and will get your arm tired. After working for awhile on improving the landing skills though, the seemingly hard pull turns into a true feel for the Maule.

I also feel that what I learned from Patrick Romano's videos,"BackcountryAviation" on YouTube, Jeremy Ainsworth's tips, and the teachings of Jim Dulin, "Contact Flying", really helped me get comfortable with landing anywhere.

https://youtu.be/CrPJac80W9Y

https://youtu.be/2tZQKOJhfas
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Mark - AK
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Re: Trim elevator on landing or not

Post by Mark - AK »

I wanted to expand on Andy's last paragraph a bit. Probably the most difficult approach and landing is a short runway with high trees at each end, so this is what works for me. This applies only to M-7 235 with long wing and long flaps, with VG's wing and bottom of the elevator, and 48 degrees of flaps (the VG's bottom of the elevator are important for this). For this approach you must be stabilized on short final and the aircraft will be about the same AOA regardless of weight so the difference will be in your speed. For me, I find that I end up with full up trim at forward CG and use slight power variations will keep the pitch control feel neutral. It doesn't take much power to bring the elevator into effectiveness and the small amount of power will not affect glide path since you are so far on the back side of the power curve. More power and the descent rate decreases but elevator pressure forward is needed... less power and up elevator is needed. If you pull power too early - like before the flare, it is bad because you can't keep the nose up. On touchdown the flaps must come up and the plane just squats right there. If you are a little late pulling the last bit of power it's no big thing touching down with a little, just don't forget to pull it off. If you have to go around be careful to add power slowly and reduce flaps because the nose will want to pitch up and you will need LOTS of forward pressure - so it's something important to practice. Practice this technique at altitude to feel how the elevator pressures change with power. I have never practiced a go-around with full flaps and full nose down trim and the very thought scares me so that is something I will try on my next flight. Note: This is not safe for use going into snow of unknown depth and serves no purpose on floats or on a normal paved runway. Also, if there is much crosswind swirling across the trees consider coming back another day. This is just a technique and it works for me...experiment and find out for yourself what works best for you. Long winded - sorry for that.
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Kirk
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Re: Trim elevator on landing or not

Post by Kirk »

Another advantage to not trimming nose up as you slow in the pattern is control on a go-around. 235+HP Maules especially, pitch nose up considerably when max power is pushed in, creating a far higher deck angle than you want for establishing climb speed.

But we all already know this because we regularly practice go-arounds and stalls... right?

Seriously, go out and practice. Even better if you have a savvy CFI to help you out.

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Re: Trim elevator on landing or not

Post by VA Maule »

Speaking of elivator authority particularly when slow and in need of all you can get. Maybe not as effective as getting your trim just right is that your horizontal stabilizer/elivator gap seals are in good shape ( and equally attached on both sides :roll:
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Andy Young
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Re: Trim elevator on landing or not

Post by Andy Young »

I’m not sure if it’s a difference in my plane, or a difference in my technique, but I’ve never experienced the loss of elevator authority that seems so common with the heavier engines. It doesn’t feel like I’ve ever even come close to that, as I don’t feel like I’m pulling very far back on the yoke to land; there always seems to be lots of stroke left that I’m not using. This includes when approaching fairly slowly (50-55 mph) to get into very short spots (400’ being short for me).

My plane is an M-6-235, with the original M-6 wing (tapered droop tip). I have VGs on the wing and under the horizontal stabilizer.

I trim about 3/4 of the way back (nose up) for landing, which still leaves some significant pull required on the yoke. I don’t trim all the way back, due to what I’ve heard about losing effectiveness, but I should try it and see if it feels different.

I do pretty much always carry a little bit of power right down to touchdown, so perhaps that is the difference??

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