Elevator trim and turning, myths and facts

[2bighorn]

Some people don't know how trim is modeled in AH, and some believe that trimming elevator manually full up will help them turn their plane tighter.

It is easy to check how trim works in relation to stick and control surface (elevators in this case).

Park the plane on tarmac, turn engine off and switch to external view (F3 is available offline, in DA and TA). Zoom in so you clearly see the elevator. Now manually trim elevator up and down. You'll see considerable deflection in either direction.

Now pull stick fully (elevators up) and repeat trimming. You'll see that trim does not deflect elevator in either direction. Hence, no matter how much you trim elevator up (or down), you won't get more deflection.

If you push stick (elevators down), you'll see you can still trim it in that position. What exactly that means in certain conditions, full flaps, CT trim on (fully up), push on stick, it's up to you to test it 

So, in conclusion, you can't get more positive elevator deflection and you won't turn better if you manually trim. This is true for every situation where AH allows you to fully deflect elevators.


Above changes somehow in some planes at higher speeds.

AH simulates control heaviness and limits elevator deflection in relation to speed, yet it does not limit trim in that range.
Combat trim will usually trim elevator down at those speeds, and you won't get full (allowable) elevator deflection. If you manually trim elevator to neutral or positive position, you will be able to use 100% of allowable elevator deflection at that speed.

To check that, take a plane which has heavy controls at speeds (in particular elevators). Ki-84 is very good example.
Get the plane fast (350mph), leave the CT on, switch to external view, zoom to elevators and move the stick. You'll see how little elevators will deflect, even when you fully pull on stick.
Now manually trim the elevators to neutral and pull on stick. You'll clearly see that you get more elevator deflection, hence you'll turn better at that speed if you manually trim elevators.

You can repeat the same procedure for aileron and rudder trim. It'll give you a clearer picture how trim works and if manual trim is necessary in order to get the most out of your favorite ride.

[Sweet2th]

So, in conclusion, you can't get more positive elevator deflection and you won't turn better if you manually trim. This is true for every situation where AH allows you to fully deflect elevators.

You won't get more deflection, but by using manual trim it cause's  the deflection reaction to be faster than with combat trim and faster reaction is better than slower reaction IMHO.

[2bighorn]

You won't get more deflection, but by using manual trim it cause's  the deflection reaction to be faster than with combat trim and faster reaction is better than slower reaction IMHO.

I just tried to explain in very basic terms, aimed at the beginners, the limitations of elevator trim and how it relates to maximum elevator deflection. For lecture about when, how and why to use MT/CT, there are more qualified people than myself, so I'll leave that to others. 

For what is worth, I've found that in type of fights I like, there's not much difference between combat and manual trim and that I don't have time to trim anyways, so I just use CT.

[Sweet2th]

 
For what is worth, I've found that in type of fights I like, there's not much difference between combat and manual trim and that I don't have time to trim anyways, so I just use CT.

I use trim full time from take off to landing, except when afk or typing, but generally full time. It has taken me a while to be able to judge where the elevator is at without looking at the gauge(therefore losing SA in the process) and more time looking around.

[BnZ]

Uh...

Maybe I'm not understanding how it works propery here, but it seems like most of the time in most planes, unless you've had an elevator shot off, you have more than enough elevator authority to pitch the wing up above the crtical AoA, and don't need full elevator deflection to get as much lift out of your wing as possible, much less trying to add any elevator.

[Sweet2th]

Uh...

Maybe I'm not understanding how it works propery here, but it seems like most of the time in most planes, unless you've had an elevator shot off, you have more than enough elevator authority to pitch the wing up above the crtical AoA, and don't need full elevator deflection to get as much lift out of your wing as possible, much less trying to add any elevator.

to see the difference try this,  fly level at about 5-K, then go  straight up with combat trim on.

now do the same thing as before but put the elevator trim in the full up position and then go straight up and you'll see the difference.

[Anodizer]

I absolutely understand what you are saying about trim not increasing your control surface deflection..  But, putting that aside, why does manual trim work to get you out of a compression dive(as well as pitching you up so fast you nearly black out if you're not careful) in a P-38 when simply pulling back on the stick should produce the same result, yet it does not..

Some people don't know how trim is modeled in AH, and some believe that trimming elevator manually full up will help them turn their plane tighter.

It is easy to check how trim works in relation to stick and control surface (elevators in this case).

Park the plane on tarmac, turn engine off and switch to external view (F3 is available offline, in DA and TA). Zoom in so you clearly see the elevator. Now manually trim elevator up and down. You'll see considerable deflection in either direction.

Now pull stick fully (elevators up) and repeat trimming. You'll see that trim does not deflect elevator in either direction. Hence, no matter how much you trim elevator up (or down), you won't get more deflection.

If you push stick (elevators down), you'll see you can still trim it in that position. What exactly that means in certain conditions, full flaps, CT trim on (fully up), push on stick, it's up to you to test it 

So, in conclusion, you can't get more positive elevator deflection and you won't turn better if you manually trim. This is true for every situation where AH allows you to fully deflect elevators.


Above changes somehow in some planes at higher speeds.

AH simulates control heaviness and limits elevator deflection in relation to speed, yet it does not limit trim in that range.
Combat trim will usually trim elevator down at those speeds, and you won't get full (allowable) elevator deflection. If you manually trim elevator to neutral or positive position, you will be able to use 100% of allowable elevator deflection at that speed.

To check that, take a plane which has heavy controls at speeds (in particular elevators). Ki-84 is very good example.
Get the plane fast (350mph), leave the CT on, switch to external view, zoom to elevators and move the stick. You'll see how little elevators will deflect, even when you fully pull on stick.
Now manually trim the elevators to neutral and pull on stick. You'll clearly see that you get more elevator deflection, hence you'll turn better at that speed if you manually trim elevators.

You can repeat the same procedure for aileron and rudder trim. It'll give you a clearer picture how trim works and if manual trim is necessary in order to get the most out of your favorite ride.

[BnZ]

I absolutely understand what you are saying about trim not increasing your control surface deflection..  But, putting that aside, why does manual trim work to get you out of a compression dive(as well as pitching you up so fast you nearly black out if you're not careful) in a P-38 when simply pulling back on the stick should produce the same result, yet it does not..

I believe in this case the control forces have gotten so heavy at high speed that the simulated pilot lacks the physical strength to deflect the elevator, so the trim is the only way to move it.

In the standard flight envelop with most planes it seems to me you can easily deflect the elevator enough to either 1. Stall 2. Black out. 3. Rip the wings off.

[BnZ]

to see the difference try this,  fly level at about 5-K, then go  straight up with combat trim on.

now do the same thing as before but put the elevator trim in the full up position and then go straight up and you'll see the difference.

I did this experiment:

I took off in a Spit9 with 100% fuel. I left the combat trim on and accelerated to 200mph IAS. I fully deflected the stick quickly and did an accelerated stall instantly.

I then trimmed the elevator full up, flew level at 200, and deflected the stick fully and did an accelrated stall instantly.

I did the same thing at 300mph IAS with similar results. Momentary black out, flollowed by accelerated stall. So that quick little experiment didn't reveal any signifigant seeming difference in elevator deflection speed or authority. Of course, this was at airspeeds where the Spit does not suffer from elevator stiffness.

The only two eccentricities I've personally noted in relation to combat trim are in vertical zooming and flap usage. In a perfectly vertical zoom, it wants to pull you back over like a loop. You have to hold the stick a little forward to keep the zoom going perfectly vertical until you run out of airspeed with the CT on. And flap usage with the CT on causes the airplane to have a pitching-up tendency which must be countered with forward stick.

[Sweet2th]

you should try it with a different fuel loadout, say 50% just to see the effects more clearly.

[Murdr]

You won't get more deflection, but by using manual trim it cause's  the deflection reaction to be faster than with combat trim and faster reaction is better than slower reaction IMHO.

No it doesn't.  There are no trim tabs in Aces High.  Trim is simulated by moving the "resting point" of the virtual stick in the cockpit in relation to your joystick center.  That's all it does.  Deflection response resides in your joystick operation.

[2bighorn]

Maybe I'm not understanding how it works propery here, but it seems like most of the time in most planes, unless you've had an elevator shot off, you have more than enough elevator authority to pitch the wing up above the crtical AoA, and don't need full elevator deflection to get as much lift out of your wing as possible, much less trying to add any elevator.

My post was solely for those who believe manually trimming elevators up will make their plane turn better/tighter. And you're right, for most of the times you don't need full deflection and when you do/can, manual trim won't help it increase.

But as always, there are exceptions, like in my Ki-84 example and is fair to mention it.

[Sweet2th]

No it doesn't.  There are no trim tabs in Aces High.  Trim is simulated by moving the "resting point" of the virtual stick in the cockpit in relation to your joystick center.  That's all it does.  Deflection response resides in your joystick operation.

 

just because it doesn't work for you doesn't mean it will not work for someone else.

[Anodizer]

I believe in this case the control forces have gotten so heavy at high speed that the simulated pilot lacks the physical strength to deflect the elevator, so the trim is the only way to move it.

In the standard flight envelop with most planes it seems to me you can easily deflect the elevator enough to either 1. Stall 2. Black out. 3. Rip the wings off.

Wait, this doesn't make sense for several reasons..  First, in a P-38, the control surfaces still move while in a compression dive...  They are just not effective due to the turbulent air both over and underneath the wing surfaces...  So, technically, not amount of trim should work..  Also, even if the speed at which the plane is moving negates movement of the elevators because the pilot can't pull the yoke/stick hard enough, how would he be able to do so with a little trim wheel?  Unless the pulley system used for the trim wheel uses a compound pulley system which is "stronger" than the one connected to the stick/yoke/rudder pedals (which wouldn't make sense)..  I dunno...Just brainstorming why stuff works the way it does...

[hlbly]

Great Post Bighorn . I think I am finally beggining to understand trim with this help