Yaw trim vs Roll Trim on Final

When lining up for final I always seem to drift one direction or another, very slowly, finding it difficult to keep aligned with the runway despite keeping the nose exactly lined up with the end of the landing zone. I have always used Yaw trim to correct this (with variable results) but was thinking perhaps I should be using Roll Trim (which I have never used) instead.

All my practice flights have been with ZERO wind and NO munitions.

I understand the difference between the 2 types in theory (Rudder Trim Vs Aileron Trim) but in practice because the drift in is so slight it's difficult to tell if it's because I'm rolling or yawing.

I'm assuming this affect is the result of changes in Power, and Prop Torque, as I adjust my descent rate, not sure if I should be using Yaw trim or Roll Trim to counter prop Torque?

I also understand that if I had an uneven payload of munitions on the wings I'd need to use Roll Trim and if the drift was due to wind I'd need to use Rudder trim to keep the nose lined up, but none of these 2 factors are relevant here.

Which trim do you use when on final to keep you lined up?

I mostly use the rudder trim, works fine for me. What you have to consider is, that you have, unlike the other warbirds we have in DCS now, wing tanks. If you don't use the fuel from both tanks equally by switching the tanks regulalry, you will get an uneven "payload". Then you need to use the aileron rim as well.

I mostly use the rudder trim, works fine for me. What you have to consider is, that you have, unlike the other warbirds we have in DCS now, wing tanks. If you don't use the fuel from both tanks equally by switching the tanks regulalry, you will get an uneven "payload". Then you need to use the aileron rim as well.

agree whne you drain left tank keeping right tank full it will become very dificulty to fly this plane no inter connectors between left and right tank so you have to switch every 15min manualy.

no wind dont make prop plane fly streight it will drift anyway due to prop effect and this drift will change with your airspeed, while slowing down it will require more and more stick and rudder intput to keep it streight this is not f-18 that you will trim for landing you have to do it manualy, p-51 trim for landing is only couple notches of elevator trim becouse plane become nose heavy with flaps and gear down rest of work is pure stick and rudder intputs.

At approach you want a little more speed to not sink your tail if doing so you may loose airfield from sight so 120-150 is good it very depends on your weight most of my flights i start at about 45-50% of fuel 68% is left/right wing tank full wich is way to much unless you want fly for more than 2 hours.

you will be touching down at about 90mph if 3 point all this speed drop will demand adjustment stick and rudder intput.

Any wind in the mission?

Any wind in the mission?

he mentioned it "no wind"

Ah, yes missed that.

Baz, have you a .trk file or a youtube video you could provide to show us what you mean?

Your description is good but given all the factors it's hard to pin down why you're experiencing what you are without seeing it ourselves.

As a rule the application of power has more pronounced effect on yaw, by the way.

That's because, whilst in the air torque will affect roll and yaw, P-factor, gyroscopic precession and spiralling airflow will have an effect on yaw also. As a rule any application of power will pull the nose left, any reduction right and you will have to coordinate the rudder controls appropriately to keep the ball centred.

Any wind in the mission?

Concerning aerodynamics/handling/performance etc., (steady) wind doesn't affect any airplane in flight. Only ground speed and ground track are changing according to the wind.

not exactly with crosswind you can expect excese lift from wind side

not exactly with crosswind you can expect excese lift from wind side

NO! For the airplane there is no such thing as a crosswind. The ground track changes and you must adjust the heading. That's all.

There's absolutely zero change in lift etc....

NO! For the airplane there is no such thing as a crosswind. The ground track changes and you must adjust the heading. That's all.

There's absolutely zero change in lift etc....

if you landing you have to locked on the ground so there is crosswind you need to adjust for or you will drift from your approach and when you about to touch ground you will get extra lift on the wind side wing.

im not expert but i do know that wind side wing can get extra lift after touch down and i was talling about it exactly

i agree that in normal flight wind speed doesnt matter you can fly even with 100kph crosswind without notice trouble start to happen when you will try to land it.

i was playing with strong winds in dcs sometime ago you can vtol p-51 heh :P

but you have to agree that crosswind forces aitional trimming in plane

Don't fully understand what you are trying to say. Again, I'm talking about the airplane in the air, not on the ground.

Don't fully understand what you are trying to say. Again, I'm talking about the airplane in the air, not on the ground.

im talkning about trasition from air to ground :)

you have to agree that crosswind forces aitional trimming in plane

No, since you don't use rudder and/or aileron trim during or for the flare!

Additional lift is only created when you are e.g. applying rudder to align the airplane longitudinal axis with the runway centerline after a crabbed approach, but this is also not wind related.

When you touch down, the upwind wing can be lifted due to the crosswind, but then you are not in the air anymore ;)

You should adjust your trim when entering the pattern and then typicality leave it alone. On final its power, stick and rudder. In crosswinds that are significant for the ac you are flying, (lighter ac being more susceptible to lighter crosswinds), you apply aileron to dip the upwind wing in the direction of the crosswind and you use rudder to keep your longitudinal axis centered on the runway center line. Or at least that's how it works in real flying. Crosswind landings in DCS are kind of underwhelming. hope that helps...

Los

No, since you don't use rudder and/or aileron trim during or for the flare!

Additional lift is only created when you are e.g. applying rudder to align the airplane longitudinal axis with the runway centerline after a crabbed approach, but this is also not wind related.

When you touch down, the upwind wing can be lifted due to the crosswind, but then you are not in the air anymore ;)

i meant for crusing not for landing :P

no in tail dragger after touch down you are still flying the plane touch down is just begining :) especialy in strong cross wind situation

Having just received my taildragger certification...

Put your control stick over into the direction of the crosswind (Eg if wind is coming from your direct left then put the stick over to the left) after you land to avoid any unpleasant issues with crosswind. And keep the stick back after landing to keep the tail down.

Of course a Mustang is a lot heavier than say an A1c husky so ymmv. :joystick:

Los

Thanks for all your help everyone.

So what I am understanding (apart from the physics are complicated!) is that I shouldn't be focusing on trim too much but be using the stick to control the aircraft? Or rather, I should expect an appropriately trimmed aircraft to still need stick input, even when lined up, despite there being no wind/munitions effect.

Fuel in the wings is an interesting one I hadn't considered, though not sure it's having an affect here as I am just spawning in 2km from the runway to practice landing.

1. I shouldn't be focusing on trim too much but be using the stick to control the aircraft?

2. I should expect an appropriately trimmed aircraft to still need stick input, even when lined up, despite there being no wind/munitions effect.

3. Fuel in the wings is an interesting one I hadn't considered, though not sure it's having an affect here as I am just spawning in 2km from the runway to practice landing.

1 Exactly :) You don't control an aircraft with trim. With trim you are only 'trimming away' the force required to constantly apply elevator/rudder/aileron.

2. Once you are trimmed for your approach speed and you don't need apply any power changes, you 'theoretically' don't need to trim anymore.

But as soon as the speed starts to decrease/increase, or you need to climb/descend, you would need to re-trim. Since these changes are only short term changes, you don't need to trim.

Furthermore we are talking about an high performance prop fighter which is by far less stable than e.g. a C172 so you can expect that it will never fly perfectly straight and level for a prolonged length of time.

3. Fuel doesn't have any effect in such a short time span. Not even during a complete pattern.

Generally you should basically use aileron (trim) to correct a lateral imbalance and rudder (trim) for power changes.

One last item; on final a few miles out I usually neutralize rudder trim since I'm going to land power off, and I want that my plane flies in straight line in this case.

That said, 2km from the runway is a very short distance and very little time to get the airplane trimmed out.

At this point my rudder trim is usually already at neutral and an imbalance isn't a factor, so you only have to fly the airplane the last few seconds...

edit: just re-read your assumptions in your initial post are all correct. :) Just don't assume that a P-51 will continue on its approach track indefinitely on it's own.

Even the slightest change in power and/or pitch would require re-trimming, but see above concerning short term changes.

NO! For the airplane there is no such thing as a crosswind. The ground track changes and you must adjust the heading. That's all.

There's absolutely zero change in lift etc....

In RL take off and landings with cross wind, a small wing down trim into the crosswind is required (most of the time)

I don't know why it is (I'm not a pilot) but a friend of mine is and when I asked him for a crosswind procedure, he told me they always have to apply a bit of wing down to the wind in the A320 when taking off on crosswind.

Now on the OP problem with the Mustang, as long as you have prop traction, you will always have a bit of slip, and the mustang is famous for being very nervous on the changes of throttle.

I usually use direct rudder on take off and landings to counter the small adjustments on throttle. Trim is not fast enough.

1. In RL take off and landings with cross wind, a small wing down trim into the crosswind is required (most of the time)

 

2. I don't know why it is (I'm not a pilot) but a friend of mine is and when I asked him for a crosswind procedure, he told me they always have to apply a bit of wing down to the wind in the A320 when taking off on crosswind.

Please re-read what I wrote several times. I'm talking about the airplane in the air, not on ground!

1. On ground you need aileron into the wind to avoid the wing being lifted, but definitely no aileron trim, since the effect is gone as soon as wheels are leaving the ground.

2. See point 1. That's only applicable on ground during the takeoff run.

Btw in planes without FBW you also have to apply aileron into the wind immediately after touchdown during the landing run for the same reason.

What's so terrible about keeping the aircraft trimmed all the way in?

Maybe its because I don't have rudder pedals and have to use the z axis on the stick, but....

If you don't have the ball centered, you lose lift in the Mustang (unlike other aircraft, a LOT of lift). Then you have to add more power, and even a little bit more power will throw the ball around even more. And if you're correcting with a bunch of rudder (for the ball), elevator (loss of lift because ball not centered), and aileron, then you're creating drag; then you gotta increase power because you're coming up short and then all that crap happens again.

IMO, avoid stick inputs and use trim because the aircraft is very delicate in the glide slope. Unless you're very experienced, you'll very slowly lose or gain some speed in the glide slope and have to do a slight engine adjustment, which should be done very slowly and delicately. And even with a slight throttle adjustment you'll need to do a rudder trim adjustment or you could lose a significant amount of lift.

This also seems like the easiest way to adapt to landings with lots of turbulence. Otherwise you'll not be able to discern what the air is doing from what your aircraft is doing.

tl;dr is - keep the rudder trimmed in the glide slope. As long as the ball is centered the aircraft will fly itself in.

As for myself, the only major stick inputs I make in a landing are when I cut power for the flare at the runway threshold.

Good points Theodore, but remember 1 thing, the amount of rudder input to center the ball is the SAME whether you use TRIM or the rudder peddles. The difference is control load the pilot experiences. Since we virtual pilots do not experience the true forces happening on the control surfaces, we can get away with not trimming.

Yes, trim your aircraft to reduce control loads, but it does not give you any more control then what you already have with stick and rudder.