Hi all,

 

I'm  an airbus Enthusiastic, but for now there is no complex Airbus Add on, so while i am waiting for FSLAB A320 or QPAC Plus/Prenium verison on xplane (or maybe a future a320 by PMDG but I guess I'm dreaming ) I started reflying the PMDG NGX. As I'm used to the C* law, and haven't had the chance to fly a GA aircraft yet, I really have a hard time trimming the NGX.

 

i usually keep pressure on the yoke until i get the flight path i want, then i adjust speed with thrust and then trim, so that i can release the yoke and only make small ajustement. But when I release the yoke, the plane will just keeps pitching up or down, and i need to make lots of trim ajustment before getting a steady flight path when i release the stick. Besides when I watch video of B737 NG, PF barely trims the aircraft and doesn't need to give lots of correftion in order to maintain the desired flight path.

 

Another question, IRL, is the wheel trim linked to the yoke, I mean if you are keeping back pressure on the yoke and then trim, will the yoke get into the neutral position as yopu're trimming so that you know when the aircraft is correctly trimmed or compensated or you need to release the stick and watch if the A/ C pitches up or down

 

Thanks

 

Camille MOUCHEL-BLAISOT

France

 

 

and haven't had the chance to fly a GA aircraft yet, I really have a hard time trimming the NGX.

 

Seeing you write that, it makes sense.

 

Trimming an aircraft, originally (and as you'd see if you'd flown a GA aircraft) is to relieve the pressure on the yoke.  In order to pitch up or down, you push or pull the yoke, and in doing so, offset its position.  Trimming allows you to relieve the pressure you'd be holding on the yoke to make it continue doing what you're asking it to do (climb or descend, and when changing speeds).

 

So, the general rule of thumb is:

Establish yourself in the condition you want to be in (e.g. a climb at 250 knots, pitching to maintain that speed), and then trim to the point where you don't need to put any pressure on the yoke (and yes, it will return to the neutral position when you do this).

 

 

 

Another question, IRL, is the wheel trim linked to the yoke

 

Yes and no...

The trim wheel is linked to the elevator (or horizontal stabilizer, depending on the aircraft), and the elevator/stabilizer is attached to the yoke.  When you trim, you're adjusting how the elevator/stabilizer behaves in the air passing the aircraft, which then lessens the pressure needed to hold it in a particular position, which then means the yoke will act accordingly.

It's very hard to judge the amount of trim being used from a video. Pilots trim as out of trim column forces change, such as with speed or thrust. Attitude changes should not produce much if any trim change. Waiting till everything is stable then trimming out means you have more trimming to do at once. Trimming in FSX is not that different to trimming in the aircraft. Things are different with helicopters but that's not the issue here.

 

The trim in the 737 is not connected to the yoke. The neutral position of the column does not move as the trim wheel rotates. No different to the situation with a sim yoke or stick in fact. The trim wheel on the 737 moves the horizontal stabiliser which changes the pitching moment. That allows the aircraft to be in trim at the new condition with the column at the neutral force position.

thanks for the explanation

 

 

 

Camille MB

France

It's very hard to judge the amount of trim being used from a video. Pilots trim as out of trim column forces change, such as with speed or thrust. Attitude changes should not produce much if any trim change. Waiting till everything is stable then trimming out means you have more trimming to do at once. Trimming in FSX is not that different to trimming in the aircraft. Things are different with helicopters but that's not the issue here.

The trim in the 737 is not connected to the yoke. The neutral position of the column does not move as the trim wheel rotates. No different to the situation with a sim yoke or stick in fact. The trim wheel on the 737 moves the horizontal stabiliser which changes the pitching moment. That allows the aircraft to be in trim at the new condition with the column at the neutral force position.

 

 

thks for the explanation, I quite agree with you concerning the video, but I meant is that I need to trim every 5 secondes, maybe because i'm use to fly virtually in normal law (C*) where the A/C is always autotrimmed, I can't help myself from trimming the A/C until i only need to perform small input on the yoke

Using AT might make trimming a bit harder, because it's constantly changing the equation. If you really want to hand fly the NGX, go full manual. Trimming will be much more stable, and work as expected.

 

In a way, AT kinda works like auto trim. If you trimmed the aircraft for say 250kts, when you pitch up, the AT will try to maintain airspeed. And since the plane is trimmed for that speed, it will sort of keep pitch.

 

And if you want to fly the NGX like an Airbus, there's always CWS mode.

 

 

The trim in the 737 is not connected to the yoke. The neutral position of the column does not move as the trim wheel rotates.

 

The feel and centering unit neutral position changes as stabilizer attitude varies. Variations in
stabilizer attitude are transmitted through the neutral shift mechanism to rotate the feel and centering
unit about the lateral axis.

 

 

I'm trying to remember how this is all linked, and I guess I don't think about it when I'm flying. The yoke (or the center point) does move. I think you really only see that effect airborne, though.

Another question, IRL, is the wheel trim linked to the yoke, I mean if you are keeping back pressure on the yoke and then trim, will the yoke get into the neutral position as yopu're trimming so that you know when the aircraft is correctly trimmed or compensated or you need to release the stick and watch if the A/ C pitches up or down

 

Thanks

 

Camille MOUCHEL-BLAISOT

France

The control yoke only controls the tiny elevator, the pitch trim controls the horizontal stabilizer, which is different from the typical single engine GA aircraft. In the ga aircraft, the yoke controls the elevator, and the trim wheel controls a trim tab on the elevator.

 

IRL you'll be holding the control yoke and you trim using feel until you don't feel the control forces anymore. Sometimes when it's really subtle I'll let go of the controls to see what the plane does, if the plane's attitude doesn't change then it's trimmed.

 

But it's all transitory, when you're flying you're pointing the airplane where you need it to go and you're continually trimming. It subconscious you don't think about it, you just do it.

 

You don't want to hold the control yoke to the point where you have an unusually large control force to trim out. On one particular airplane I've flown if the control forces got too large, the trim motor was unable to overcome the aerodynamic forces exerted on the stab to trim the horizontal stab. When that happens and you keep trying to trim, you'll end up locking out the pitch trim system for the rest of the flight and now you have no pitch trim control, so the aircraft is trimmed to the last airspeed the stab is stuck at.

 

 

Steve w.

A real handy-dandy add on I use is

RealTrim - Version 1.2

 

It's a small .dll you drop into your Modules folder, and, in the easy to understand instructions for use from the author...

 

Activate the trimming-feature via button while moving the joystick from deflection
to neutral. The movement of the joystick is  converted into the opposite amount of
movement of the trim-wheel. This matches real-life where the pilot trims out force
felt on the yoke in ONE smooth operation: moving the trim-wheel.

 

I use it all the time on almost all aircraft.

It may be of use to you or not

It can be found both here and on Avsim...realtr12.zip is the file name I downloaded.

Hope it helps out a little bit Sounds to me like what you are looking for.

Pat☺

I'm trying to remember how this is all linked, and I guess I don't think about it when I'm flying. The yoke (or the center point) does move. I think you really only see that effect airborne, though.

I realised stab trim position was an input to the elevator feel mechanism but I didn't know it could move the neutral point. I can't say I've ever noticed it happen whenever I've flown a 737 FFS, but then again I've never been looking for it.

 

I use it all the time on almost all aircraft.

It may be of use to you or not

It can be found both here and on Avsim...realtr12.zip is the file name I downloaded.

Hope it helps out a little bit Sounds to me like what you are looking for.

Pat☺

Have you been able to use RealTrim successfully with the 737NGX?  I have RealTrim version 1.7 and it does not work on the NGX, apparently because PMDG bypassed the standard FSX trim system.

Thx,

Al

Have you been able to use RealTrim successfully with the 737NGX?  I have RealTrim version 1.7 and it does not work on the NGX, apparently because PMDG bypassed the standard FSX trim system.

Thx,

Al

 

Short answer: NO.

Long answer: I have no payware aircraft, therefore, I have never tried it in the NGX 737. It DOES work wonderfully in the TDS B737-600, however I apologise, if I implied that it works perfectly, if at all, in all aircraft. I can say it works for a treat in Kunzori Ito's fa-18s, F-4's, and so on, in fact, every free ware plane I've ever had starting in F- ..., all of Mike Stone's birds, and so on. It is most asssuredly NOT for helo's though. HTRv1.5 fills that niche perfectly. It works in freeware Pipers, Beech and Mooney's, not to mention Cessnas, altho they are generally stable enough not to need it. Yes, I could tweak the [Flight_tuning] of the aircraft.cfg files, but this software add-on seems to me a lot easier. Basically, they've already done the work, so I can just sit back and enjoy my flying! The freeware P3 I've tried in responded wonderfully. And so on and so on.

I hope that little bit of long windedness answers the question adequately, Al (my father's name, btw Alfred in fact)   Any more please feel free to ask, I am an open book. Unfortunately I think the index fell out along the way someplace...

 

Pat☺

Short answer: NO.

I agree RealTrim is a great addon that works on all the default FSX a/c that I've tried, and on some payware a/c as well. Apparently the 737NGX has a lot of special non-FSX standard coding in the quest for accuracy and realism, and so it is not surprising that some existing software that assumes standard FSX coding won't work.

Al

To each their own I suppose, but realtrim doesn't sound very realistic to me. More of an aid to make life easy, like autorudder. Sure it's a quick and precise way to trim, but there's no substitute for learning how to do it properly. I thought that was the main purpose of flightsim as a hobby.

It sounds quite useful for a helicopter sim though, as that's more like how trim works in that case.

To each their own I suppose, but realtrim doesn't sound very realistic to me. More of an aid to make life easy, like autorudder. Sure it's a quick and precise way to trim, but there's no substitute for learning how to do it properly. I thought that was the main purpose of flightsim as a hobby.

 

It sounds quite useful for a helicopter sim though, as that's more like how trim works in that case.

RealTrim is realistic in the sense that it lets you trim the plane while smoothly returning a spring loaded yoke to it's neutral, no force position. This simulates adjusting RW trim so there is no force on the yoke. I find this better approximates my RW experience then repeated "guessing" on how much trim to input since there is no force feedback provided as in the RW.  With RealTrim you can still make minor trim inputs as you would do without RealTrim. As you said, to each his own.

Al

I have to agree with Al on this. By "zeroing" the forces acting against an off-center yoke/stick in one, smooth operation, it's about as real as it gets. Press the trim button (in military birds, it's the "hat" switch, btw) and relaxing the pressure against the return  or "feel" springs is very realistic. Maybe not how the civilian airliners do it, and if that's so, then more power to em, but for military birds with a stick, it's 100% accurate.

 

Pat☺