I was reading the "trimming for level flight" thread and it started me thinking. Yeah, i know, dangerous huh. If you trim for level flight and then reduce throttle to come in for a landing you need to slow the plane also. Just by reducing the throttle you start to decend but at the same airspeed, so you pull back on the stick to slow down some while still decending. So at this point you are holding the stick back to maintain proper air speed and should be adjusting the throttle to maintain proper altitude. Am i correct so far? In 100% scale (full size) planes you reduce throttle and adjust trim to maintain desired airspeed and then adjust engine rpm to maintain proper glideslope until your flare. Does any one do this on your models? That way proper airspeed could be maintain at all times without having to hold the stick back and possible stalling by slowing too much without noticing. To put it simply, reduce throttle to say 1/4(what ever works out to be the best), then pull the pitch trim back so many clicks to set up a set glide slope angle and only use the throttle to adjust altitude until you need to flare.

skeeter

There is no need to adjust the trim for landing.

When you decide to land, you reduce the throttle. This will cause the plane to slow down and therefore, lose altitude. The plane will assume a slight nose-down attitude to maintain flying speed.

The trick is to reduce your power at a point where you meet the ground while you are over the runway.

If you are too high, you'll have to go around. If you are too low, you'll need to increase throttle to make it over the threshold.

What you need to do is to fly the plane to the runway. If your plane needs 1/4 power to keep it flying with out the desire for it to stall, then set up your approach and fly the plane right onto the runway. As you cross the threshold cut your power and let it touch down. Most scale planes require this type of flying and approach. Good Luck, Dave

I agree, use trim to get the model to fly straight and level at your choice for a cruising throttle setting. When I reduce throttle to start setting up for a landing, I use back pressure on the stick to control airspeed and throttle to control descent.

Once you get past the basic trainers (which by design are speed sensitive in pitch), then all trimming for landing is done with balance and engine thrust angles. If you have a model that is hard to land, yet flys well under full power, those are the areas you need to examine and adjust.

skeeter_ca,
Trim for landings.
Good luck,
Darrol

there is very little point in trimming for landing with a model airplane due to the fact that your in a turn most of the time and havig to carry back pressure anyway. I would suggest slowing the plane down to a good approach speed on an upwind leg and then going into your landing pattern, maintaining your approach speed with elevator and controlling your decent with your throttle and fly it to the runway. Alot of full scale thinking does not translate well to models. In the end, it all boils down to letting your subconcious reactions take over, If you need to think about what your doing, your behind the plane and in trouble. I suggest as I have done, go fly a whole bunch of landing on a sim and find out what works best for you.

Here is how I was taught to land.
I'll bet most of us learned this way and teach this way.
At cruise speed (level flight speed) make lower and lower passess. In a manner of speakig this is flying the plane to the runway.
At the time when the student can consistently make straight and level passes at 3 or 4 feet off the runway have him reduce throttle and the plane lands. Sometimes the student sees this coming, sometimes not.
I remember doing endless 4 foot runs down the center of the strip before I landed. Many students are not given the opportunity to gain some accuracy in their landings.
Now years later it is relaxing to make one wheel touch and goes and spot landings.

oz


I practiced approaches over and over with my instructor. Then
out of the blue he said that approach looks good, as I cleared the
threshold I hear " go ahead and land". There was no time to over think
or panic. I trim for level flight at 1/2 throttle BTW.


Bob

As said above, a lot of 1:1 actions don't transfer to models well. Have someone go out with a stopwatch and time how long it takes your model to get from down wind to touch down. I think you'll find you almost don't have time to retrim the model. The negative side to trimming a model to land is that if you have to punch it, you now have to fight the ballooning model by holding nose down and trying to retrim.

Not that is isnt wrong to do it, just it takes more time than it's worth.

MTC
YMMV
Been teaching folks to fly since 96

Yeah, let's add another brain function while landing. Think about it. Major T said it, and I will elaborate a bit.

Once you get trimmed for a comfortable flight at whatever throttle you use you fly and do your thing. Ok. Now it's time to land and the landing process starts. You start at the downwind leg, and may last about 10 to 20 seconds. During that time, you are slowing down by reducing throttle. What are you going to trim for? Level flight? I don't think so because the process, by design, is to reduce speed and thus altitude.

Next, you reach your downwind altitude and your downwind speed, you maintain a lower altitude at that throttle setting. Ok.. no trim needed there, but do you have time to think about trim?

Now you make the turn to base then reduce throttle more. Trim again? in that 2 or 3 seconds of base flight? Again, I don't think so.

Now, you are turning to final. Reduce throttle the aircraft begins to descend. The rate of descent is determined by the throttle setting. Trim again? Trim for what? Level flight? Do you have time? Aren't you trying to reduce speed and altitude?

Now you are over the runway centerline (I certainly hope that's your goal, and if you did everything properly, you probably are..) and during the time from turn to base then turn to final, and landing, did you have time to think about trim adjustments? Is any needed? No, again, I don't think so.

Now you are very close to the ground and you "tap" the elevator to reduce speed yet more, then nose up, flair, and landing. Trim? Ummm... what for?

No trim adjustments needed during the process of landing, which begins at the turn to your downwind leg.

Hope you didn't take me wrong CGR,

I do not trim for landing. Just for level
flight.

Bob

Gotcha, Bob. I just wanted to make clear what I was taught and feel is the proper approach (pun intended)...

Some people tend to make it more difficult than it really is. For most of the flyers out there, the planes they build will pretty much do what they want them to do, within reason. If the plane is mechanically sound (meaning all surfaces are properly under control and properly trimmed (whole different game than the trim we're talking about here, but the same thing.. if you get my meaning) then landing comes in as a step by step process with a lot of observation and keeping away from over-correction. Trying to trim during landing is both unnecessary and distracting. Neither of which is a good thing during the most "dangerous" part of the flight (an awful lot of unavoidable crashes happen during landings due to stalling, over correction, and losing focus).

CGr.

The big thing in a real plane is you can have you hand on the trim and the controls. Unless you are flying a Kraft Signature,Ace R/C or a Proline from the 80s you cant do it. Also if you had to do a go around or touch and go the plane would be out of trim at a high power setting; also at reduced power it is more natural to modulate up elevator. Digital trims you could do a quick 2 click to help but manual trims like most trainers have would have you concentration in the wrong place.

Like have been said, there is no need for trim when you are landing any model, also take note that there is a difference between trimming and a landing condition which is a preprogrammed situation on the radio which deploy flaps and give some effect on elevator for a hot plane (or WWII, or other scale plane) to land.
The use of new computerized radios which have many features, give you the easiness of a landing condition to ensure a safer landing assuming that the plane needs flaps to guarantee enough low speed vs. stalling.
Those features may be set in almost all type of plane that uses separate servos for ailerons and are controlled by separate channels.
In a regular basis, talking about trainers and sport planes there is no need for trim when you are approaching to land, but also take note that when your plane is descending then your throttle stick becomes the elevator and the elevator stick becomes the speed control.