Hello everyone. I was thinking today about the concept of trim adjustments on aircrafts. Would it be possible to get rid of trim if yokes on planes didn't return to it's original position after being moved? For example, let's say you've reached your flight level, and you pushed the stick forward to level off. Once you level off, you could let go of the yoke, and it would remain in that position, not snap back. I don't know too much about physics or exactly what trim is, but it seems to me like that could be a solution to planes drifting off once pressure on the controls is released. Thoughts?

What you're talking about would be getting into the,  "fly by wire"  arena.. and without a computer to monitor it all, you'd have to have some sort of friction arrangement to "hold" the controls wherever it is put them.. taking away all "feel" for the pilot.

All that tradiational trim does, is to change the aerodynamically neutral state of a control surface, to match a desired attitude.

Pre-Selecting the Altitude and Heading, followed by switching on the Radio Autopilot (if fitted) should achieve a stable hands-off flight controlled automatically by the servo-motors....

...otherwise the Manual Trim will always be necessary to ease the pressure on the controls...

Paul...G-BPLF....

What you are describing is, in effect, a "fly by wire" system, where the pilot lets the autopilot fly while pretending he's flying by using yoke and rudder pedals to tell the AP what he wants to do, instead of pushing buttons and turning knobs.

I get the idea- eliminate the need for the pilot to make trim adjustments- but heck, that's what autopliots are for. Why not just engage the AP and tell it what heading and altitude you want?

  If you are operating the trim system correctly- regardless of what type it is- the stick or yoke should not move from its new position anyway. Why make it more complicated?
 



The idea with trim, particulary with airplanes that have some sort of mechanical connection between controls and flight surfaces, and moving trim tabs, is not to "fly with trim", but to put the controls where they need to be, then trim until you can let go and they will stay where you left them. Works fine without any additional machinery moving the controls. When you add servos to move the yoke, etc. what you have is an autopilot.

Has everyone forgot about the new Dassault Falcon 7X?  This feature IS ON THIS AIRPLANE!  The 7X's advanced flight control system eliminates trim, you point the aircraft where you want it to go, and it goes there, regardles of speed or configuration.  Its amazing!  Read about it.

http://www.dassaultfalcon.com/7x/

-Crossfire- wrote on Nov 29^th, 2009 at 11:18pm:


It's impressive, no doubt about it. But...

A Cub will do the same thing, but you will have to move the trim a little. 

The reason this is not standard for all planes is because nobody will be able to enter the field, and thus keep the entire industry alive, if there are no planes that cost less than a million dollars. 

its a real bad idea.. namely because many aircraft including jets have a trim system that moves the entire horizontal stabilizer instead of just a tab on the tip of the elevator/ aileron and in these aircraft if u dont trim your plane correctely and end up with excessive drag from the deflected elevator u could end up with real marginal performance esp on a single engine! we actually use this technique to bleed speed in real dornier 228s on landings or even in the air.. as far as i know even fly by wire systems have a force feedback system on the stick.. u cant really go eliminating the trim .. it can be automated - like a trim coupling system whhen u raise or retract flaps but overall its a senseless idea - it doesnt really hurt anyways.. many aircraft have trim operated by an up down switch so no big deal anyways! hope it answers the question.