Combat trim question

[Ack-Ack]

In my experience elevator trim does help you to turn faster.  Take a plane up and turn it till it slows enough ur not getting the blackout visual.  Then dial in elevator trim, you will see a return to blackout graphics for a bit.

It's all in your mind, cranking up the positive elevator trim will not make you turn tighter or give you any sort of advantage.  It's an Aces High urban legend that has been debunked many, many times over the years.

 

Its my understanding that on p38's the trim was rudimentary, on planes like some 109's, some trim functions were missing (elevators), on other planes they had full set of trim. 

According to the P-38 flight manual I have for the P-38-25-L0, it had a full set of trim controls and was pretty modern for the time period.


ack-ack

[prono]

It's all in your mind, cranking up the positive elevator trim will not make you turn tighter or give you any sort of advantage. 

ack-ack

Flying ki84 with with trim up I can black out when turning. This is not possible with auto trim. Don't tell me me " elevator trim will not make you turn tighter or give you any sort of advantage" 

[shiv]

I fly the F4U's exclusively for the most part.  I use CT for all "general" flying, and "low key" fights.  If the fight starts getting to the extremes of speed (<150, >450), or into flaps maneuvers, or into vertical roping-type flight, I shut off the CT and go to manual trim.

I also shut it off and go to manual for landing (so I don't need to fight the CT) and/or if I'm damaged and need to trim for that.

I use the X52, and have my trim mapped to the rotary dials, so I have my manual trim pre-set.  I switch off the CT, and the trim goes to where I have it ptre-set.  I also have small marks on the dials, so I can make sure the rotary dials are where I want them.  It's not that hard to tweak them a bit here and there too.

A few questions on this please if you have the time.  Is this for all three axes or are we just talking about elevator trim?  Or mostly elevator trim?   And with the flaps out and slow in the F4U when you shut CT off are you then trimming a bit nose heavy?

I've been experimenting with this again and I'm not at all sure I know what I'm doing.

Thanks.

[katanaso]

Flying ki84 with with trim up I can black out when turning. This is not possible with auto trim. Don't tell me me " elevator trim will not make you turn tighter or give you any sort of advantage" 

Would this be because you're already lifting the nose, so when you turn and pull back on the stick, you're closer to the max range of the elevator?

In other words, using arbitrary numbers, if the max elevator range is 10, and auto trim is at 5, you'd have 5 more steps to pull with the stick.

However, say you manually trim 'up' to 7, you'd only have 3 more steps to pull with the stick, hence the blackout.

Game mechanics folks -- does it work like that?


mir

[mtnman]

A few questions on this please if you have the time.  Is this for all three axes or are we just talking about elevator trim?  Or mostly elevator trim?   And with the flaps out and slow in the F4U when you shut CT off are you then trimming a bit nose heavy?

I've been experimenting with this again and I'm not at all sure I know what I'm doing.

Thanks.

I guess, technically, it's all three axis, simply because none of them are on "auto" anymore...  But in reality, I only adjust aileron and elevator on a normal basis.  There are times I'll adjust rudder as well, but the only time that comes to mind is when I'm damaged following a fight, and am RTB.  Damage may require me to adjust rudder.

My normal (non-damaged) trim adjustments are a bit of right aileron, and a bit of down elevator. 

I basically trim for hands-off level flight at about 275mph, and do that in a situation where fuel burn will not effect that in a L/R sense (i.e. my wing tanks are burned to where I want them, drops tanks are gone if I've taken them, and I've manually selected my main tank for the remainder of my flight).  My manual trims are mapped to rotating dials on my throttle, and I've used a "Sharpie" marker to mark where I like them to line up.  That allows me to pre-set my trims at a convenient time, or to visually verify that they're correct even if I'm in Auto-trim mode at that given moment.

[Zygote404]

It's all in your mind, cranking up the positive elevator trim will not make you turn tighter or give you any sort of advantage.  It's an Aces High urban legend that has been debunked many, many times over the years.

  
According to the P-38 flight manual I have for the P-38-25-L0, it had a full set of trim controls and was pretty modern for the time period.


ack-ack

http://www.simhq.com/_air/air_003x.html

Trim tabs on the leading edge adds greater area of elevator which should make you turn faster.  I might be wrong but my mind can't make my plane resume blackout when I add trim to the elevator.  

[BaldEagl]

http://www.simhq.com/_air/air_003x.html

Trim tabs on the leading edge adds greater area of elevator which should make you turn faster.  I might be wrong but my mind can't make my plane resume blackout when I add trim to the elevator.  

First of all the trim tab is on the trailing edge, not the leading edge.  Second, the trim tab deflects in the opposite direction of the control surface so if anything, it would reduce effectiveness of the control surface.  In reality, it helps because without the trim tabs aid the pilot wouldn't be able to move the control at all and once it is deflected the trim tab is now neutral to the airflow.  Go look at your own diagram again.

[Rolex]

Trim tabs are a located on the trailing edge of a control surface.
They were not extensions, but embedded into the control surface and did not add surface area.
Trim cannot make you turn faster.
Blackout correlates directly to G's only.

Here is a P-51 horizontal stabilizer, elevator and trim tab arrangement:

[Zygote404]

Okay well I was in a rush.  I think its obvious from the diagram I meant trailing edge rather then leading.  Have a look at the diagram whats the trim tab doing? Generating? What happens if you adjust its angle to be more in line with the elevator surface?

[InCrypt]

I will tell you this tail about Manual trim. I am one of those guys who does manual trim ALL the time. The only time I am not in manual trim is when I’m doing auto climb, or auto level. And I only use Auto level after I’ve trimmed the aircraft for level flight – this way I don’t have any jarring control inputs when I switch off auto-level, to say, engage a bandit. I’ve been flying in AH for 7 months now, and trimming the plane has become second nature. I’ve got the X52 and have the rotor dials and slider set up for all three trim axis. (I’ve since put a yolk into service and use the nice big red lever, from the yolks throttle quadrant, for elevator. I still use the two rotary knobs on the X52 throttle for elevator and rudder, the slider is now for Zoom)

Several of my squaddies have mentioned that they thought I was nuts for using manual trim all the time, they questioned what benefit I could get out of it. It’s not very useful tactically, as I’m usually too busy with other major control surfaces to try and hit elevator trim in a combat situation. But last night a squaddie and I took up 262’s. We lifted at the exact same time, performed the same maneuvers in welded wing. I was the trailing wing partner so I should use more fuel to keep in position. He used combat trim and I used manual trim. Over the course of 6 sorties a pattern emerged were at the end of the flight I always had two to five MORE minutes of flying time than he did. So, by not using manual trim, you may have to “fight” the CT a bit and throw more control surface into the slip stream to get the plane to do what you want. This induces drag that you have to overcome with thrust, burning more fuel.
In a combat situation, with two identical planes and two pilots of equal skill, the manual trim can give you an advantage as your plane will induce less drag and  you can retain more E. Now, we are not talking a lot here. Maybe 2 to 5 miles an hour at best. And You have to be an EXPERT at the manual trim. Because while the CT may not be as efficient, it will not err. The Manual trim is one more thing a new pilot will have to manage, thus increasing workload. It’s also possible to enter in the wrong trim input and actually hurt your E.

The other thing about Manual trim. Do not think of Trim as a set of “Bonus Control surfaces”. This is a common mistake, and people will “Fly” with trim. Use Rudder trim to help hold the ball in the center. Use elevator trim just to remove bank pressure. But elevator trim is a unique case. Think of it as a speed governor. You set the elevator trim to hold a speed, and then use the engine to climb or descend. I’ve recently been flying the Piper Cub by A2A in MS FSX. This aspect of elevator trim is VERY pronounced in this simulator, and it has taught me a lot on how to use the trim in AH.

[Mace2004]

Okay well I was in a rush.  I think its obvious from the diagram I meant trailing edge rather then leading. Have a look at the diagram whats the trim tab doing? Generating? What happens if you adjust its angle to be more in line with the elevator surface?

First off, the intent of trim is to relieve the pilot's need to maintain a control input.  That's all there is to it.  Without trim an aircraft's flight controls would only be "trimmed" correctly under one set of circumstances of speed and load.  Once the aircraft moves away from that trimmed speed the pilot will need to apply control forces and hold them to maintain the new condition.  

Say your aircraft will fly level with hands off the controls at 190mph.  190mph is its trim speed.  Now decelerate to 160mph and try to stay level.  What happens?  The main wing will generate less lift due to the decreased speed and the aircraft will descend. Since you're trying to stay level you have to pull the stick aft to increase aircraft AoA to generate enough lift to stay level, the problem is that now you have to hold it aft to stay level at 160mph.  

Moving the stick aft means the elevator trailing edge moves up just as shown in your picture.  The trim tab on the trailing edge of the elevator (as your picture depicts) can be set to generate a force on the trailing edge of the elevator, just as the elevator generates a force on the horizontal stab.  Moving the trim tab down (again, as in your picture) increases the camber (curve) of that portion of the elevator and generates an upward force on the elevator.  By correctly adjusting the trim the upward force of the trim tab will hold the elevator in the correct trailing edge up position so the pilot doesn't have to hold the stick back.  The stick will still be further aft when trimmed but the pilot doesn't have to hold it, the trim tab does it for him. Once this is done, the new trim speed is 160mph.

You can see from this that trim doesn't effect the aircraft's turn performance since it doesn't affect the total amount of elevator movement, it just affects the force the pilot needs to apply.  Now, there is a condition where trim can affect pitch and that's when the aircraft is fast enough that the airload on the elevator makes it impossible for the pilot to apply enough force to move the elevator through its full range of motion.  Trim can help by adding additional force to help the pilot move the elevator but this is a very limited condition.  This is what happens with the 109 in a high-speed dive but, again, this only applies in a very narrow range of very high-speed flight, not in typical turn fights.

[Mace2004]

But last night a squaddie and I took up 262’s. We lifted at the exact same time, performed the same maneuvers in welded wing. I was the trailing wing partner so I should use more fuel to keep in position. He used combat trim and I used manual trim. Over the course of 6 sorties a pattern emerged were at the end of the flight I always had two to five MORE minutes of flying time than he did. So, by not using manual trim, you may have to “fight” the CT a bit and throw more control surface into the slip stream to get the plane to do what you want. This induces drag that you have to overcome with thrust, burning more fuel.
In a combat situation, with two identical planes and two pilots of equal skill, the manual trim can give you an advantage as your plane will induce less drag and  you can retain more E. Now, we are not talking a lot here. Maybe 2 to 5 miles an hour at best. And You have to be an EXPERT at the manual trim. Because while the CT may not be as efficient, it will not err. The Manual trim is one more thing a new pilot will have to manage, thus increasing workload. It’s also possible to enter in the wrong trim input and actually hurt your E.

Interesting ideas InCrypt but not really valid.  Trim tabs are very small surfaces and don't contribute substantially to overall drag and, quite frankly, I doubt HT actually bothers to model their drag at all.  Also, not all trim systems use tabs, some use an adjustable bungy and servo system that simply holds the stick in the right position.  Trim simply relieves the pilot of the need to hold control inputs and the control inputs remain whether they're held in position by a trim system or the pilot so manual or CT trim is irrelevant to overall drag.  You're "throwing" no more control surfaces in the wind either way.  This is even truer with AH which simply models a "trimmed" control surface position based on a lookup table of speed.  I think what you're seeing is simply related to your throttle control versus your lead's.

I'm not saying that flying manual isn't a good idea, it can be, but for different reasons than drag.

Where you run into problems with CT are those conditions that are different than the assumptions made in the look-up table.  For instance, say the 109 look-up table says that the airplane needs 4degrees of nose-up trim at 100mph.  Fly level at 100mph and yep, it works but what if you're in a vertical zoom?  You start at 300mph with 0 trim and as your airspeed bleeds down and you slow through 100mph CT is dutifully dialing in more and more nose-up trim giving you 4 degrees.  What does the airplane want to do?  It'll want to pitch over on its back because of the nose-up trim but since you want to keep going pure vertical you have to counteract the CT by pushing forward on the stick.  This is a case where CT is working against you. 

A similar thing happens when you're slow and want to accelerate.  You're in a turn fight at 100mph with 4 deg of nose-up trim again.  The trim doesn't really both you much right here since you're turning but then you want to unload and extend to regain E so you lower your nose to accelerate away but now CT wants to keep your nose up so you're fighting it again and have to push over harder to overcome that 4 deg of nose-up trim. 

Also, CT doesn't take flaps into account.  In a turn fight this doesn't matter much since you're turning although it can exacerbate the problems with vertical moves and extensions as you get even more nose-up trim than needed with the flaps.  It is very noticable though in some other conditions like landing.  Say you're on approach to the CV and start dropping your flaps.  What happens?  Your nose come up and you begin to balloon and have to counteract it by pushing forward stick to keep coming down, definitely NOT what you'd actually be doing. 

[Ack-Ack]

Flying ki84 with with trim up I can black out when turning. This is not possible with auto trim. Don't tell me me " elevator trim will not make you turn tighter or give you any sort of advantage" 

I will tell you that using elevator trim to make yourself turn tighter is just a myth because it is.  Any percieved increase in turning is all in your mind and nothing more.  As I said, this myth has been busted many times over the years that I'm frankly surprised that people still think using elevator trim to turn tighter works.


ack-ack

[ImADot]

I will tell you that using elevator trim to make yourself turn tighter is just a myth because it is.  Any percieved increase in turning is all in your mind and nothing more.  As I said, this myth has been busted many times over the years that I'm frankly surprised that people still think using elevator trim to turn tighter works.


ack-ack

You're wrong.  I'm weak and can't yank my joystick all the way back, so elevator trim up lets me turn tighter because I don't have to pull my joystick back so far.      

[katanaso]

You're wrong.  I'm weak and can't yank my joystick all the way back, so elevator trim up lets me turn tighter because I don't have to pull my joystick back so far.      

hehe Actually, how you're describing it has you still turning the same, but you just have less throw in the stick to achieve it.

That's what I was asking about in my previous post, and if it's the way it works in the game...



mir