Author Topic: Trim, and the merits of manual trim (Read 741 times)

SpinDoc1 · « **on:** January 06, 2003, 09:58:29 AM »

Would someone be so kind as to post the pluses and minuses of using manual trim as opposed to auto combat trim. I have experimented with this as a second stick set, to use my hat as view in set 1 and trim in set 2 with another button to switch sets. It was very handy for switching modes, but is there a better way? Thanks in advance!

jonnyb · « **Reply #1 on:** January 06, 2003, 10:30:11 AM »

Using the auto-trim function of AH can be helpful in certain situations. For example, it can help you during takeoff, auto-climb and level flight. It's downsides are that it attempts to adjust your control surfaces based on a set of tables with entries for things like airspeed and altitude. This can present multiple problems in a combat situation, including stallouts and compression.

I will use the combat trim only when flying to target, or on return home. In combat, I manually trim my plane to adjust for the needs of the situation.

SpinDoc1 · « **Reply #2 on:** January 06, 2003, 05:01:16 PM »

JohnnyB, what needs would those situations present? I appreciate your advice so far, but I'm also looking for more specific examples of how to employ manual trim. Case in point, I was fighting the F4U-1 in my 109G10, and I tried using some elevator trim to pull a harder turn on the opponent, but the result was stalling out of the sky miserably from the increased drag and slower speed. I understand the G10 is far from a great turn fighter in the first place, but the plane just felt twice as sluggish as normal while using manual trim. Any more suggestions? Also, does the stick set idea sound right?

crowbaby · « **Reply #3 on:** January 06, 2003, 05:14:58 PM »

>>Would someone be so kind as to post the pluses and minuses of using manual trim as opposed to auto combat trim<<

Basically, what jonnyb said: Combat trim will continually trim your plane for the speed which it is at.

For example, if you're making a single sharp turn, you'll bleed off a little speed initially, Combat Trim will retrim your nose (elevator trim) up for the new speed. This doesn't allow you to pull more Gs, or get a tighter turn than a plane that's been manually trimmed properly. What it does do is put your plane in a configuration where it WANTS to fly at the slower speed. To do this it will tighten the turn (slowing you more) and then when you roll level, instead of returning to your initial speed, the plane will want to climb. This means that you've got to correct by pushing the nose down.

If you went into the same turn manually trimmed for, say, 200mph, things would be different. First you'll bleed off the initial speed, but your plane will want to return to its trimmed speed, so you'll fly through the turn, actually accelerating again as your wing loading increases. You'll loose a little altitude, but this is normal, efficient behaviour for an aeroplane. When you roll wings level your plane will naturally want to return to its trimmed speed.

Now, these two cases aren't hugely different, you could say it's a matter of preference, whichever one you're used to using will be the easier. However, when you include rudder and aileron trim into the equation, it can become far more difficult to overcome the Combat trim and force the plane back to the speed and direction you want it at. Given the extreme torque produced in most of our planes, aileron and even rudder trim can change a lot at different speeds.

Again, if you're used to combat trim you won't notice this, you just force the plane in the direction you want it to go, and as you speed up or slow down, it'll retrim for you. No big deal, but it's my feeling that the planes fly more cleanly and respond far better without it. Even if you don't retrim during a fight, you know what speed you were trimmed for going in, so you know how your plane will behave. In AH the stick range is such that you can maneuvre pretty well at 200mph even if you're trimmed for 300, you've got to compensate, of course, but i find that a lot more natural than trying to figure out what combat trim thinks it's doing.

I'm not knocking Combat Trim. It's an excellent system, and it makes it possible to hop in the planes and fly them. I think, though, that once you're established on the learning curve, it's much better to turn it off.

crowbaby · « **Reply #4 on:** January 06, 2003, 05:31:14 PM »

Oops, just seen your second post.

I understand what you say about the plane feeling sluggish when manually trimmed as opposed to using CT. This is because, if you're manually trimmed for 250mph, then the plane wants to stay at that speed, and when you're maneuvring you've got to pull or push it away form the speed it's configured at.
What it does mean, though, is that you're more aware of the speed you're at, because you'll be physically yanking the plane away from its trimmed speed. I don't know much about the 109G-10, but if you've got to turnfight in it, then first find its best corner speed. Trim for that speed. Then, as you turnfight, your plane will want to climb or sink to maintain that speed, which should suit you perfectly.
Basically, i feel speed is critical in combat, far too important a thing to let Combat Trim take care of for you. I find that if i fly with CT, then i have huge excursions from my intended airspeed. There's no speed feedback in a computer with out looking at the dial, so it's very easy to turn and burn a while, then find that combat trim has changed your speed, most often to well below your best maneuvring speed.

As for the Hat on your joystick, that's exactly what i use. I now know how many 'button presses' i need to change trimmed speed in my favourite planes, and it's become fairly intuitive. Mind you, i did fly the P-38 a lot to start with - it mostly only needs elevator trim changing because of its counter rotating props.

SpinDoc1 · « **Reply #5 on:** January 06, 2003, 06:22:21 PM »

Thanks for that wonderful explanation, I see your point is using trim and I think some experimentation would do me well. I would like to see how this affects turn fighters in particular. Thanks again, crow and johnny!

crowbaby · « **Reply #6 on:** January 06, 2003, 06:23:58 PM »

Glad to be of help. I'm sorry if my posts were a bit wordy, that was as clear as i could make myself without getting tied in knots.

jonnyb · « **Reply #7 on:** January 06, 2003, 07:15:15 PM »

lol crow...I started to reply, but realized you hit everything I was going to throw out there. Nice job in your explanations.

BDBAL · « **Reply #8 on:** January 12, 2003, 02:25:37 PM »

I have been flying AH for about a year now, and recently mapped trim to my hat (stick 3 of all things.) I am trying to get greater performance from the aircraft now, and survive wing tip loss lol. I dont understand what is meant as trimming a plane for a specific speed, for example 250 mph, etc.

So here are some questions: 1. When trim is set do the trimmed surfaces stay in that configuration regardless of manuevers? 2. Where and when should trim be set? (altitude, attitude, speed) (level fast, slow?) 3. When manuevering and modifying trim simultaneously what are some characteristics to look for to get best performance (ie hard breaking turn to create overshoot?) 4.Where is information for trimming configerations per plane, or is it a trial and error thing.

Lastly, my aircraft of choice recently have been the 51b and FM2, any specifics would be helpful.

Thanks for all your help.
BDBAL

Innominate · « **Reply #9 on:** January 12, 2003, 02:53:24 PM »

Quote

Originally posted by BDBAL

So here are some questions: 1. When trim is set do the trimmed surfaces stay in that configuration regardless of manuevers? 2. Where and when should trim be set? (altitude, attitude, speed) (level fast, slow?) 3. When manuevering and modifying trim simultaneously what are some characteristics to look for to get best performance (ie hard breaking turn to create overshoot?) 4.Where is information for trimming configerations per plane, or is it a trial and error thing.

1. Yes, once you set trim(assuming combat trim is off) it stays there untill you move it to something else.
2. Trim should be set any time you're trying to fly in a straight direction and dont want to have to handle the stick.
3. The only time trim helps maneuvering is when control surfaces on your plane are frozen due to over-speed. However, combat trim can impair maneuvering by adjusting the trim by a large amount while you're trying to maneuver, forcing you to correct for it as it changes.
4. You trim your plane untill it's flying straight and level without touching the stick. You can use the auto-trim functions to assist in this. (with auto-combat trim off, hit x, and it'll trim you for level flight)

Eagler · « **Reply #10 on:** January 12, 2003, 03:25:24 PM »

always manual trim, easy with X45 rotors

always have to trim as usually in a 109

BDBAL · « **Reply #11 on:** January 12, 2003, 04:12:48 PM »

Another question on trim, go figure. After trimming up the aircraft if you hit x for autopilot or alt x to climb, when you exit the auto system are your previous trim settings still active? Thanks again.

BDBAL

Innominate · « **Reply #12 on:** January 12, 2003, 04:26:45 PM »

Quote

Originally posted by BDBAL
Another question on trim, go figure. After trimming up the aircraft if you hit x for autopilot or alt x to climb, when you exit the auto system are your previous trim settings still active? Thanks again.

BDBAL

The autopilot isnt really an autopilot, it's AutoTrim. You can fly level with autopilot, turn it off, and the auto-trim settings remain, giving you an ideal trim.

Xjazz · « **Reply #13 on:** January 13, 2003, 01:35:02 AM »

S!

Combat Trim (ct) is good only for cruising purpose (imo).

During hard combat maneuvering ct try to follow changing flight envelope and adjust trim settings all the time. This could give annouing feeling like somebody else is flying your plane and mixing your inputs.

About FM2:
This funny plane needs a lot of left feet to keep slip ball center.

akak · « **Reply #14 on:** January 13, 2003, 01:54:43 AM »

Read Lephturn's article on Trim. It will pretty much answer any questions you have on the different modes of auto and manual trims.

I myself manually trim my plane since it's rather easy to do in the P-38L. The only trim I have to adjust is the elevator trim because the counter-rotating props negate any engine torque from the twin engines. When you read Lephturn's article, you'll see that Combat Trim can be beneficial in some planes while having detrimental effects in other planes.

As for the auto trims, I usually only use the auto-climb and auto-level. Auto-climb to get to my cruising alt and then auto-level to trim out at speed. After that it's all manual trim.

ack-ack