New thread on TRIM

[LYNX]

Now, I ask you this in all honesty and curiosity. If an aircraft has trim tabs, and the elevator is in the full up position, would not raising the trim tabs change the elevator effectiveness?

regards, teshaw
 

Not sure if my understanding is correct but I believe all you would get is lighter feel on the stick.  The elevator cannot go any further than the manufacturers full stop.

Folk also have to realise that once off combat trim you have to keep trimming by hand.  If your con dives low you'll quickly have to trim down or level or put combat trim on.  Some folk use a notch of flaps or two and trim nose low to compensate for the bouncy nose up feel.   All to fiddly in a multi con situation for my liking. Press this press that watch this watch that when all the time trying to pull a lead or deflection shot.  But hey...different strokes for different folks. 

[BaldEagl]

Roger that, BaldEagl.  We were posting simultaneously.  If one thinks it through to the logical extreme, for the tab to give an added aerodynamic boost, it would have to be trimmed in the opposite direction.  That is it would have to be trimmed to increase the force on the stick, requiring greater effort to pull back on the the stick.  There may be a point where the force on the stick might exceed the pilot's ability or the strength of the linkages between stick and elevator.

No, I think that's backwards.

Think about a compressed dive.  The airstream is providing greater force then the pilot can overcome by pulling back on the stick, thus the elevators are locked.  When the pilot trims up the trim tab is deflected down into the airstream providing an upward force on the elevator which is transferred to the stick thereby assisting the pilot in pulling it back.

The pilot can trim in this instance because the trim tab is relatively small compared to the elevator itself so forcing it into the airstream is relatively that much easier.

[RufusLeaking]

No, I think that's backwards.

Think about a compressed dive.  The airstream is providing greater force then the pilot can overcome by pulling back on the stick, thus the elevators are locked.  When the pilot trims up the trim tab is deflected down into the airstream providing an upward force on the elevator which is transferred to the stick thereby assisting the pilot in pulling it back.

You are right.

What I am saying about the logical extreme is that to pull the nose up at the maximum rate is to deflect the trailing edge of the elevator up.  The little trim tab is on the trailing edge of the elevator, and, when trimmed in the full nose down direction (opposite), the trailing edge of the trim tab would also be deflected up and act as a much smaller elevator on the actual elevator.

The mental and physical efforts would make this plain silly in Real Life. 

Regarding changing trim in combat, I doubt it was a widespread practice.  While training in the USAF, I had to demonstrate proficiency in certain maneuvers, such as the split S, Immelman, full loops, etc.  One trimmed to the point of entry and then just went through the maneuver with what one had.  The 'feel' of the stick was often a good clue to one's flight situation.

In AH2, is there a feedback option?  I do not have a force feedback on my stick.  So, a lot of this discussion is probably not useful in game.

[Wreked]

Thanx for the explanaitions folks - This is all starting to make sense (note I said starting) - so help me out here:

When in a dive sometimes I "run out" of stick sometimes and can not keep the nose down - hammering on the trim "I" key will bring it back - what is this all about? why is it happening? and can it be avoided all together??

cheers eh!

[TEShaw]

Wreked,

Don't hijack this thread with your 'lift' issues.

regards, teshaw

[BaldEagl]

Thanx for the explanaitions folks - This is all starting to make sense (note I said starting) - so help me out here:

When in a dive sometimes I "run out" of stick sometimes and can not keep the nose down - hammering on the trim "I" key will bring it back - what is this all about? why is it happening? and can it be avoided all together??

cheers eh!

That happens because you are trimmed for level flight.  In level flight there's always a slight nose-up elevator deflection.  As the airstream forces become greater in your dive the nose up elevator deflection becomes more pronounced, thus you need to trim down to release pressure on the stick.  Some planes are affected by this more than others.

[CAP1]

Thanx for the explanaitions folks - This is all starting to make sense (note I said starting) - so help me out here:

When in a dive sometimes I "run out" of stick sometimes and can not keep the nose down - hammering on the trim "I" key will bring it back - what is this all about? why is it happening? and can it be avoided all together??

cheers eh!

i've done that in lancs......dive, full forward stick......fll down trim changed nothing...the nose still came up.

[Wreked]

Wreked,

Don't hijack this thread with your 'lift' issues.

regards, teshaw

Thanx shaw - I do indeed appreciate your polite words of help - however by "lift" if you are referring to gravity then I'm clueless - isn't that something best overcome with a wand and 2 pinches of newt navel lint??

cheers eh!

[RufusLeaking]

When in a dive sometimes I "run out" of stick sometimes and can not keep the nose down - hammering on the trim "I" key will bring it back - what is this all about? why is it happening? and can it be avoided all together??

Lift is a function of airspeed.  For a given airfoil (chord, camber, etc.), as airspeed increases, lift increases.  At least until shockwaves start forming, at which time all bets are off, along with some plane parts.

It looks like in the modeling, the increased lift exceeds the elevator authority to keep the nose down.  To keep beating a dead horse, trim won't give any more deflection on the elevator.

Personally, I have never encountered this in real life.  Then again, there are many actions in AH2 that I haven't done in the real world.

[FireDrgn]

What is the reason for trimming a plane? Is it just a necessary evil of turning Combat trim off..... Is it not true that all 38 jocks trim their planes? and fly with combat trim off.

<S>

[Stoney]

Because, simply stated, an aircraft will only be stable in a specific configuration at a single speed and/or center of gravity.  Any change in speed and/or center of gravity will make the plane want to climb, descend, roll, yaw, etc.  Trim allows the pilot to decrease his workload by making fine-tuned adjustments to control surfaces that will "balance" (for lack of a better term) the controls for the specific configuration he's in.  Ultimately, a perfectly trimmed aircraft will fly "hands-off".  For maneuvering flight, adjusting trim makes certain control inputs easier--i.e. they require less force from the pilot, reducing the effort required, and reducing fatigue over the long term. 

Since speed is a function of pitch, the elevator trim is often the most used trim control in the aircraft, since the most common configuration change in an aircraft is speed.  Even the most simple planes will typically have pitch trim.  Some more sophisticated aircraft have pitch, aileron, and rudder trim.  Some WWII aircraft had all three, and some did not.  The Bf-109 series, for example, did not have adjustable rudder trim tabs.  Aileron and rudder trim are typically only seen on higher performance aircraft.

[Shuffler]

Is it not true that all 38 jocks trim their planes? and fly with combat trim off.

<S>

I'm no 38 jock but the answer is "No".

[kvuo75]

I found this:

When a trim tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down.


This would explain why they have no ability to improve turn performance and it also explains why they are so effective in overcoming control stiffness.

if you'll notice, the ailerons on the f4u's in game have servo tabs as described..

[Stoney]

if you'll notice, the ailerons on the f4u's in game have servo tabs as described..

They're modeled, which gives me hope that someday we'll actually have the aerodynamic model reflect trim tabs versus the partially deflected control surfaces.  Until then, we'll just have to make do...

[Cobra516]

I found this:

When a trim tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down.


This would explain why they have no ability to improve turn performance and it also explains why they are so effective in overcoming control stiffness.

I was about to post that.  I've never been a believer of trim helping the airplane do anything better (turning, rolling, etc).

The only reason trim exists is to relieve the control pressures felt during flight at a given airspeed/configuration.

The Super Cub, and some other airplanes use a jackscrew in the tail to adjust the pitch of the horizontal stabilizer, basically changing the angle of attack of the horizontal stabilizer to increase/reduce lift and in turn changing the stick pressures felt. 

Also, in Aces High, there isn't an airplane in the game that I don't have the elevator authority to pull it into a stall at any speed.  So adding nose up elevator trim would be useless, because you couldn't use that extra elevator to pull the nose around any faster after you've exceeded the wings critical angle of attack.