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dravid kenyala

Trimming and how it is done.

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Hi all. At what point we do start trimming aircraft? When we will be knowing the aircraft is out of trim? When to stop trimming?

 

On what basis like either watching the fd bar to be on centre line of artificial horizon by trimming when it is not on the centre ( between blue and brown) of artificial horizon.

When you will know this time I have to trim up and k this time I have to trim nose down.

 

I know that I have to trim but I don't know when to trim and what to see to initiate manual trimming.

 

A lot of people said that to release the pressure on yoke and when you apply some force on yoke and when the aircraft is not responding as it should be we start trimming.

I haven't experienced with this. Even I trim or I don't trim I am manually landing the aircraft.

 

I have also seen the thread on trim on final? I couldn't find the answers.

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Take off and manually climb the 777. once established in a climb let go of the yoke. what happens? the nose will drop down because the plane has a tendency to reestablish straight and level flight

 

1. climb

2. let go of yoke

3. nose will drop (you dont want this) you want nose to stay up so it can climb but without pulling back on the stick 

4. apply elevator up trim and let go of yoke

5. when trim is applied correctly you can let go of the yoke and the 777 will climb by itself

 

do the reverse for descending

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Take off and manually climb the 777. once established in a climb let go of the yoke. what happens? the nose will drop down because the plane has a tendency to reestablish straight and level flight

 

1. climb

2. let go of yoke

3. nose will drop (you dont want this) you want nose to stay up so it can climb but without pulling back on the stick 

4. apply elevator up trim and let go of yoke

5. when trim is applied correctly you can let go of the yoke and the 777 will climb by itself

 

do the reverse for descending

This is going to sound very basic, but I tend to rely on autopilot way too much. When I turn off the auto pilot the plane stops its decent even if I idle the engines and I end up too high and having to force the nose down to drop for a hard landing. If I take the autopilot off at say 400ft do I need to adjust the trim to keep the plane on its decent path? I would love to do fully manual landings but always have difficulty getting the plane down in time. For takeoff I set my trim to the number in the FMC. At what point would I need to readjust my trim? Usually I just keep my hand on the yoke until I have climbed 1-2k and then switch on autopilot for the rest of the climb while I am raising flaps and running through radios/lights etc.

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the steps above are for use when not flying a flight plan. Its just for training.

 

In a flight with a flight plan the autopilot will trim the aircraft. If your established in a descent and you disconnect autopilot the plane in theory should be fully trimmed so you shouldn't need to touch the trim 

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For takeoff I set my trim to the number in the FMC. At what point would I need to readjust my trim?

 

Well as your speed moves up so does your lift and therefore as you speed up you should only have to trim down to counteract the lift produced from the speed.

 

For your question about landing.  On the NGX I use the trim a lot more then on the 777.  I takeover turning off A/P anywhere from 4000 to 2500 AGL for most my landings.  Sometime only once established on the LOC in lower visibility.  On the 777 I may only have to adjust trim just a few units during landing as the fly-by-wire is at work and seams to be modeled pretty well by PMDG.  Really for my 777 landing once I get the FD on point along with speed at Vref it takes little work and pretty much just holding it until flaring.

 

Of course if the speed moves +/- you may have to re-trim as speed and lift have a relationship together and therefore will always effect the other if you don't want a heavy/light yoke.

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Hi all. At what point we do start trimming aircraft? When we will be knowing the aircraft is out of trim? When to stop trimming?

 

On what basis like either watching the fd bar to be on centre line of artificial horizon by trimming when it is not on the centre ( between blue and brown) of artificial horizon.

When you will know this time I have to trim up and k this time I have to trim nose down.

 

I know that I have to trim but I don't know when to trim and what to see to initiate manual trimming.

 

A lot of people said that to release the pressure on yoke and when you apply some force on yoke and when the aircraft is not responding as it should be we start trimming.

I haven't experienced with this. Even I trim or I don't trim I am manually landing the aircraft.

 

I have also seen the thread on trim on final? I couldn't find the answers.

 

There are issues at the moment with the trim, and fly-by-wire.

 

PMDG have confirmed they are investigating.

 

It has been confirmed by real world 777 pilots on this forum, that the auto trimming phenomenon that occurs with elevator input is wrong. It shouldn't happen.

 

Manual trimming is tricky too. It should feel no different to trimming any aircraft. It does. 

 

As yet, nothing has appeared in PMDG's pinned bug list.

 

I'd say we are due an update on this issue.

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I was told by Support that the Autotrim/Trim System on the 777X is completely rewritten right now so you shouldn't try to cope with/get used to it right now too much. At the moment, there is actually no manual trimming necessary (except for TO of course) - just keep the pitch you want and the Autotrim will do the rest - might not be realistic but that is how it works for now....

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I was told by Support that the Autotrim/Trim System on the 777X is completely rewritten right now so you shouldn't try to cope with/get used to it right now too much.

 

Oh right, that's great news Chris. Glad to hear it.

 

Thanks for that.

 

:smile:

 

Would be nice if PMDG updated the pinned bug tracking list though to keep us in the loop.

 

That's what it's there for.

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I was told by Support that the Autotrim/Trim System on the 777X is completely rewritten right now so you shouldn't try to cope with/get used to it right now too much. At the moment, there is actually no manual trimming necessary (except for TO of course) - just keep the pitch you want and the Autotrim will do the rest - might not be realistic but that is how it works for now....

 

You mean PMDG just done an airbus :P 

Airbus X auto trim sucks........hope PMDG will do an airbus oneday~

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Boeing does not embrace the Airbus auto-trim philosophy. Neither the 777 or 787 fly by wire systems have auto-trim. In all my flights, trim has worked as expected by adding "bias" to the control input such that pitch would remain as desired without control input. Don't know what you guys are talking about.

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Boeing does not embrace the Airbus auto-trim philosophy. Neither the 777 or 787 fly by wire systems have auto-trim. In all my flights, trim has worked as expected by adding "bias" to the control input such that pitch would remain as desired without control input. Don't know what you guys are talking about.

 

What we are referring to, and why PMDG has "apparently" rewritten the code, is in regard to the following...

 

Configuration changes in the real T7, for example flap deployment and thrust increases, are trimmed out automatically by the fly-by-wire. However, just like any other aircraft, speed changes need to be trimmed out manually by the pilot.

 

In the PMDG 777 the above is not the case. It's possible to hand fly, change speed, and not bother to trim at all. As speed changes, and elevator input is used to maintain flight path, we find ourselves magically in trim as soon as the new speed is established. This is wrong. Speed changes should  require manual trimming when hand flying.

 

In addition, when we do trim manually, nothing happens initially, and then it over trims. Trimming should feel just the same as trimming any airliner.

 

Rob, a real world 777 pilot, on a previous flight, hand flew the real aircraft and confirmed that in reality, it doesn't function the way the T7 does in the sim.

 

This should help you see the issues.

 

http://forum.avsim.net/topic/419407-hand-flying-tips/page-7

 

Post 20 from Rob.

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This is so weird. Ever since the release there's a group of people saying that PMDG is wrong, and another group saying the PMDG is right... and there are real 777 pilots in both groups!

 

So now I hadn't been flying the 777 very much because I'm afraid to learn it incorrectly.

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I have flown about a hundred hours in the PMDG 777. Except for the first couple of hours I have not touched the trim button except to set initial trim setting. 

 

I apply gentle yoke pressure in the appropriate direction depending on take off or landing. The aircraft trims and will remain so until I command otherwise with the yoke.

 

Judging from the discussions indicating that it may not be correct or that it is being rewritten, this may be an incorrect procedure. Currently, it seems to work. 

 

I await definitive and authoritative information from PMDG.

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This is so weird. Ever since the release there's a group of people saying that PMDG is wrong, and another group saying the PMDG is right... and there are real 777 pilots in both groups!

 

So now I hadn't been flying the 777 very much because I'm afraid to learn it incorrectly.

Just go by the manuals as they are the final authority a forum is not the best place to learn about this plane unless the poster is a VERIFIED rw pilot.

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the steps above are for use when not flying a flight plan. Its just for training.

 

In a flight with a flight plan the autopilot will trim the aircraft. If your established in a descent and you disconnect autopilot the plane in theory should be fully trimmed so you shouldn't need to touch the trim 

 

I have to ask: Where did you find connection between flight plan and trimming an aircraft?   :blink:

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