Author Topic: Energy effects of Trim and stick positioning (Read 467 times)

Simaril · « **on:** September 03, 2007, 04:09:36 PM »

Simple question.

A real trim tab is a miniature control surface, for conteracting flight effects so the stick remains centered in neutral flight. So, having too much up on the elevator trim could be countered by pusing the stick forward, but at the cost of increased resistance and energy loss.

Is that the case in AH? My impression is that AH trim sets default positions for the actual primary control surface, not a "tab." IF so, that would make the combination I described above neutral in energy effects, and so it wouldnt matter if you set things that way as opposed to more tightly trimming all the time.

(I hope there's a good answer to this, because it -- and my stupidity -- cost me an AFK death....)

Murdr · « **Reply #1 on:** September 03, 2007, 08:45:55 PM »

I think your real plane premiss is off. The majority of your drag is going to come from your AoA, along all your surfaces that are not oriented edge on into the airflow. The little bit of drag caused by pushing either just the tabs, or the elevators into the airflow, should be negligible as long as you are using it to hold =>1G. Either method (trim or elevators) should affect the net pressures around the tailplane the same, and I would think that the drag created at the tailplane would be roughly the same in either case?

But to answer your question, in AH it wouldn't matter if you are using stick or trim to keep a neutral nose since either method has exactly the same results on the control surfaces in AH.

Simaril · « **Reply #2 on:** September 03, 2007, 08:58:07 PM »

Thanks.

Hazard69 · « **Reply #3 on:** September 04, 2007, 10:09:31 AM »

Actually, the trim tabs are basically there to keep the control surfaces slightly deflected, without the pilot having to keep it held up/down. The effect is the same as keeping the control surface deflected. So there isn't much of a energy saving issue there, (unless you looking at stabilizer trim which they have on larger hi-speed aircraft these days. Now there is a difference in trim drag generated. They definitely didn't have that system IIRC in WWII).

kvuo75 · « **Reply #4 on:** September 04, 2007, 04:42:02 PM »

Quote

Originally posted by Hazard69
Actually, the trim tabs are basically there to keep the control surfaces slightly deflected, without the pilot having to keep it held up/down. The effect is the same as keeping the control surface deflected.

yea. the tabs actually move the surface, they're not "little" versions of the actual control surface. they move opposite. ie: for "down" elevator trim, the tab goes up, to push the elevator down.

Simaril · « **Reply #5 on:** September 05, 2007, 12:05:44 PM »

Thanks a lot guys. I learn something every time I come here.

Donzo · « **Reply #6 on:** September 05, 2007, 04:14:51 PM »

On some planes (the ones with yolks or sitcks modeled in the cockpit) you can see the stick/yolk move as you adjust the trim.