How do you trim for short field?

[DENNY]

Spinner2
yes it is a PA 18 160 hp. How hard do you break once you get on the ground? That is the reason for the nose up trim. As far as takeoff trim I don’t do full nose up. Depending on load and surface high may use a lot of nose down trim. However, If I am on smooth ground and have a clear runway ahead of me then it is nine turns back from full forward. I do not attempt to pick up the tail. I simply let the tail come up on its own, it will lift a few inches above the ground initially and then at around 35 mph it will start to lift again at that point if I hold the stick and pull flaps it flies off the ground smoothly. By using this technique it takes the pilot out of the equation and adjust for any headwind it will most always be the shortest takeoff. This works empty or with an average load. Some may ask why not lift the tail for a better view? This is a really good idea if you have rough terrain or need to maneuver around obstacles. However when you lift the tail you now squat the front tires this slows you a bit when you first start to roll and gives you more tire drag versus wind drag, It is noticeable if you are down to three psi. The second point is now it is up to the pilot to determine when to rotate, if you rotate too early and hit your tail wheel you are going to lose distance on takeoff. If you rotate too late you won’t strike your tail wheel but you will have given away ground. I’m an old guy so taking my decision out of the rotation and leaving it to the Aircraft to tell me when the wing it’s ready makes it more dependable. Hope that all makes sense to everyone. Every cub is going to vary some from the trim settings I mentioned. And once again for the lower time pilots neutral trim is fine on landing and throw some nose down for takeoff.
DENNY

[KevinJ]

Speaking of tire pressures Denny.....Do you change your psi between everyday use and STOL comps? More pressure gives less rolling resistance but more bounce if you land firmly and less contact patch while braking. Too little pressure lengthens t/o roll but helps on the backside. Am I over thinking?

[DENNY]

You’re thinking is spot on. The gear also becomes a factor with tire pressure. I change tire pressure a LOT! And takeoff the difference between 3 pounds and 5 pounds can be 20 to 30 foot. I used to run around 3 1/2 - 4 with bungees now that I have a AOSS I can run a little harder on takeoff because I don’t have the bungee bounce factor on landing. I normally run around 4 1/2 for competition now. I always carry a 1 pound electric compressor with me. If I am going to a new spot or soft spot I will air down to 3 - 3 1/2 pounds for landing once I can inspect the runway if it’s firm enough I will bring it back up to six for takeoff with the pump. For a normal flying known firm spots I run 6 to 8 psi.
DENNY

edit: If you’re not going to be flying for a while pump your bush wheels up to the max pressure listed on the side wall it is a lot easier on the tires and easier to push around.

[spinner2]

Spinner2
yes it is a PA 18 160 hp. How hard do you break once you get on the ground? That is the reason for the nose up trim. As far as takeoff trim I don’t do full nose up. Depending on load and surface high may use a lot of nose down trim. However, If I am on smooth ground and have a clear runway ahead of me then it is nine turns back from full forward. I do not attempt to pick up the tail. I simply let the tail come up on its own, it will lift a few inches above the ground initially and then at around 35 mph it will start to lift again at that point if I hold the stick and pull flaps it flies off the ground smoothly. By using this technique it takes the pilot out of the equation and adjust for any headwind it will most always be the shortest takeoff. This works empty or with an average load. Some may ask why not lift the tail for a better view?

DENNY

I like these type of discussions.

I brake with the tail up on almost every landing. I hold the tail down with elevator and sometimes power. The brakes are Grove 1.75” double puck, so plenty of braking power. Even when there is plenty of room to roll out I still pick a spot and stop with brakes. It keeps me sharp.

On skis, when I three-point land, I have plenty of nose down trim dialed in. Yesterday I pulled the 31s and put on straight skis since we finally got some valley snow.



You can see where my trim was after sliding up to the hangar.

On takeoff the tail pops up almost immediately trimmed like this and as the airspeed flashes though 25, with 2 notches of flaps pulled, I tug on the stick and up we go. I’m then taking the flaps out followed by trimming for neutral.

If I have full up trim dialed in it just seems to take forever to get airborne.

With up trim dialed in for landing, for me, it is harder to hit the spot and the AOA seems high with reduced visibility.

It is easy to fall into routines and established patterns. So a couple of years ago I re-tried it all, after wondering if my nose down trim was really helping me. Neutral trim, some up trim, full up trim, changes in flaps and flap timing. I’d pace off my distances after landings. Same with takeoffs. I did the same on skis on a big reservoir where I could make dozens of landings and takeoffs in virgin snow and see without a doubt where there were ski tracks and where they ended.

With me in my Cub there was no doubt what worked the best.

When I had my 160 hp PA18 I made similar tests and got started on using some nose-down trim. With this Cub I worked on refining my technique.

This is my experience with thousands of landings FWIW.

[CamTom12]

I have significantly less experience, but I use nose down trim for my landings and take offs too.

[Steve Pierce]

Speaking of tire pressures Denny.....Do you change your psi between everyday use and STOL comps? More pressure gives less rolling resistance but more bounce if you land firmly and less contact patch while braking. Too little pressure lengthens t/o roll but helps on the backside. Am I over thinking?

Making fun of my first landing at the last Hondo even I see. I tried a little extra air and it bounced big time.

[KevinJ]

Making fun of my first landing at the last Hondo even I see. I tried a little extra air and it bounced big time.

I figured your auto inflation/deflation malfunctioned when you were in the pattern. Between your nitrous shot on takeoff and your flap dump switch, you’ve got a lot of buttons to push.

[DENNY]

Spinner2
I have experimented with trying to blow the tail down as I was braking hard right at the end of the rollout, it worked but lengthen my landing a bit. Something good to have in the back pocket if you felt it going over! bit of thread drift, what cowling do you have? It looks great! Is the engine/ motor lowered?
DENNY

[spinner2]

Denny I sent you a PM.

[don d]

Empty, what should my 1200# Cubs tail weigh?

[DENNY]

Depends on a lot of factors. Are you talking 3 point or in level flight/What type of gear (stock, 3x3, ect)/ Tire size/how much weight on the nose (180HP, club prop or cato, ect). All the factors combine to affect the weight of the tail at a given position. Basic cub with 31 inch tires, 160hp, Borer, stock gear in level flight should be around 80 lbs give or take 10 lbs when the cub is static. Once you add airflow, you add another long list of factors.
DENNY

[don d]

Thanks, Denny

[JacobM]

Finally got to get some practice in this weekend, thanks for all of the input everyone.

I had always trimmed a two or three cranks up both for takeoff and landing and when I was trying to land short I was holding a lot of back pressure. So after much experimentation the best I could do is to trim for hands off at the slowest speed that I still had some safety margin. That ended up being almost all the way nose up, I'm sure in part because I'm so heavy, but after trying the full nose down trim that my new friend was telling me about I'm certain that's not the way to go for my particular airplane/situation. I had cones set out and I'm happy with the distances I'm getting for now but I need practice on hitting the spot with this new (to me) approach having the nose so much higher.

[CamTom12]

Glad you’re finding what works best for the you/your airplane combo!

[aktango58]

Finally got to get some practice in this weekend, thanks for all of the input everyone.

I had always trimmed a two or three cranks up both for takeoff and landing and when I was trying to land short I was holding a lot of back pressure. So after much experimentation the best I could do is to trim for hands off at the slowest speed that I still had some safety margin. That ended up being almost all the way nose up, I'm sure in part because I'm so heavy, but after trying the full nose down trim that my new friend was telling me about I'm certain that's not the way to go for my particular airplane/situation. I had cones set out and I'm happy with the distances I'm getting for now but I need practice on hitting the spot with this new (to me) approach having the nose so much higher.

Some planes, (O-550 Maule for instance) beg for weight in the tail. As you practice, put some weight in the back (5-10 lbs, more?) and try it. Might change the dynamic for landing.

[Olibuilt]

Someone on this forum told me to trim full nose up for landing, and nose down for takeoff.
Advice I try to follow on every flight, for STOL operations.

[JacobM]

Someone on this forum told me to trim full nose up for landing, and nose down for takeoff.
Advice I try to follow on every flight, for STOL operations.

Thanks Oli, I enjoy watching your videos, that's a pretty great ride you've got.

I haven't tried that for take off, what is your technique there? Let the tail raise on it's own and full flap/back still when it's ready? I assume the theory is that getting the wing to a low angle of attack quickly reduces wind drag? I'll have to do some more experimenting next time I get out.

[JacobM]

Some planes, (O-550 Maule for instance) beg for weight in the tail. As you practice, put some weight in the back (5-10 lbs, more?) and try it. Might change the dynamic for landing.

I think for now I'm going to work on getting more consistent and pilot weight reduction. I'll give this a shot when I feel like I've got the technique dialed in.

[stewartb]

Technique varies with conditions. A steep approach over obstacles on a gusty crosswind day is different than a calm day to a flatlander strip. Power off, power on, obstructions, bumps, traffic, aircraft weight and balance, etc all factor in. I always trim for airspeed but my flap settings, airspeed, and glide slope aren't always the same. Don't get stuck in one setup.

[exhaust]

Maybe I’m missing something here. 300hrs and 1800 landings? That’s like a landing every 10 seconds? I’m a low time
Cub pilot but I have been told by those with 10s of thousands of cub hours that a shorter strip needs a longer set up. Make it right. Maybe take some more time on your approach if your doing a landing every 10 seconds. (Or tell me
to go back to math class...which is possible too lol)

[hotrod180]

Maybe I’m missing something here. 300hrs and 1800 landings? That’s like a landing every 10 seconds? I’m a low time
Cub pilot but I have been told by those with 10s of thousands of cub hours that a shorter strip needs a longer set up. Make it right. Maybe take some more time on your approach if your doing a landing every 10 seconds. (Or tell me
to go back to math class...which is possible too lol)

That's one landing every ten minutes.
Back to math class for you....

[DENNY]

Go back to math class. One landing every 10 seconds is 360 in one hour. With your math it would only take 5 hours for 1800 landings. DENNY

[DENNY]

A short strip should not need any longer setup then a long one if you have good technique. A three mile 747 approach is of little use in a cub.
DENNY

[stewartb]

When I do the math it's one landing every 10 minutes.

To the original topic, I had a conversation recently with a guy about my electric trim. In my Cub the electric trim allows me to fly differently than I would with manual trim. I take off with full nose down trim. Add power, the tail instantly comes up, roll a little, pull back... I'm flying. With a touch on the thumb switch I trim to climb-out airspeed very easily. For landing I use full nose up trim. I haven't had any problems other than modulating throttle just a little stops a descent and makes the plane climb, but that's a pilot-induced problem. I'm not sure what I'll do on a cross windy day. Land diagonally... wrestle with the wind... turn tail and run... it'll depend on the day. It's all fun. Until it isn't.

[exhaust]

Hahaha see I warned ya!! In my defense I did get 10 I just read it as seconds not minutes.
so one every 10 minutes. Got it. Gonna go print up some flash cards or download some math apps off my kids iPad...maybe it on on some zoom meeting math classes with my 12 year old.

[tempdoug]

1 landing every 10 minutes is still amazing, cant be done, frozen 300 mile long lake with skis, maybe?

[exhaust]

1 landing every 10 minutes is still amazing, cant be done, frozen 300 mile long lake with skis, maybe?

I was wrong with my first post and didn’t wanna push it. But I had the same thought. Small pattern and all a guy does is pattern work or lake skipping I can see it. I’ve done 10 landings or so in a row on skis with a long lake but I’m a long way from a landing every 10 min.

[DENNY]

When I am training for STOL comp I can usually do a pattern with full stop in 3 1/2 min. After 1/2 hour ADD kicks in and I stop or go to some high stall work. If others join the pattern it can take longer. DENNY

[mam90]

If we’re going to call out every pilot that embellishes a little, well....... What’s that saying, “I’ve told you a zillion times not to exaggerate!”

[exhaust]

If we’re going to call out every pilot that embellishes a little, well....... What’s that saying, “I’ve told you a zillion times not to exaggerate!”

lol truth. Pilots all started as fisherman I think....

[tempdoug]

I was wrong with my first post and didn’t wanna push it. But I had the same thought. Small pattern and all a guy does is pattern work or lake skipping I can see it. I’ve done 10 landings or so in a row on skis with a long lake but I’m a long way from a landing every 10 min.

just trying to think how you could do the most takeoffs and landings in a short time and say get above 50 ft and thats the quickest way i can think of is with a long lake and skis.

[dgapilot]

When I was towing gliders all the time, easy to do 6 tows an hour to 2000 ATL with a PA-18-150, 8 tows an hour with the Pawnee. No issue doing a take off and landing every 10 minutes. I’ve had days where I did 42 tows or more.


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