Hi I would like to take time to address this forum, I have several thousand hours on the 767, 757 and 777...real aircraft, I am a real world current captain on the aircraft now.

 

I have had the PMDG 777 installed now for the last few days test flying it in many different configurations, weights, and speeds flying manually to investigate the trim issues noted on this thread. I am not a beta tester, or a developer, just another flight sim fan. I have a well aged CH flight sim yoke, throtttles, and pedals, and have my FSX running with realism sliders set to full and no additional FSUIPC intervention, though obviously it is installed.

 

I am happy with the way the aircraft handles in general, and to me seems quite true to the real airplane. In fact the real aircraft I would say is even more sensitive to trim and yoke inputs, such as those seen on days where I have done approaches in mild orographic turbulence, or taken off in the same conditions.

 

The feeling of the weight of the aircraft is very well simulated. The only thing i find not so well simulated is the delayed response of the the thrust which I believe is slower then the real thing. I have flown the 200 LR, and all varients of the 777 now for over 6 years and this has been my experience.

 

I want to thank the PMDG team for such a remarkable product. I loved the PMDG 737 (even though I have no time on the real aircraft), and must say the LEVEL D 767 really set the bar for all others, but really the PMDG team have lived up to my expectations on this product, and I hope that says something. Sure their are a few small things that are a bit off, but generally speaking at least with my simple set up, the aircraft behaves much the same way the real one does, albeit a litte lazier in pitch and thrust control. Amazing when you think of it really, that you can sit at home and even some what reproduce the feeling of flying this incredible machine.  

 

I am surprised no one has mentioned the incredible ECL, as for me in real life, this is the most revolutionary part of this aircraft. Hope you all enjoy it and feel very happy to be part of such an interesting community of fellow flight simmers!

 

Cheers,

 

K

Hi pilotresponse.

 

Thank you very much for yor intervention.

 

Only one question for you.

 

Is the real 777 having this kind of auto-trim when in Normal mode during pitch and/or speed changes when hand-flying it?

 

Thanks in advance.

 

Best regards

I flew the 777 between 220 and 320 knots and back to 220 on AP watching how the trim responded. While speed changed the trim moved a little, but at the stabilized speed there was very little difference in trim position. This may be why some people don't need to trim throughout a flight. The problem, if there is one, may be with the flight model itself, not the FBW speed trim.

I flew the 777 between 220 and 320 knots and back to 220 on AP watching how the trim responded. While speed changed the trim moved a little, but at the stabilized speed there was very little difference in trim position. This may be why some people don't need to trim throughout a flight. The problem, if there is one, may be with the flight model itself, not the FBW speed trim.

Hi Kevin....can you do another real world 777 college a favour?

Do the same maneuver with AP disengaged please.

 

Level flight,5000ft or so trimmed for 220kt.

 

Now dont touch the trim switches at all please!

 

Just maintain 5000ft or whayever with the yoke

 

Now set 320kt and let the AT accelerate the plane.

when stable at 320kt (without ever having touched the trim, this is critical!) let the plane go.

What does it do?

Shoot up like a rocket or does it stay at 5000ft pretty much?

(mine stays there and it should not since it is trimmed for 220kt))

 

Please let us know.

 

Our problem here is with manual trim, not with how the AP trims, that is why I ask you to disconnect the AP.

 

Regards and Thx :-)

Hi Kevin....can you do another real world 777 college a favour?

Do the same maneuver with AP disengaged please.

 

Level flight,5000ft or so trimmed for 220kt.

 

Now dont touch the trim switches at all please!

 

Just maintain 5000ft or whayever with the yoke

 

Now set 320kt and let the AT accelerate the plane.

when stable at 320kt (without ever having touched the trim, this is critical!) let the plane go.

What does it do?

Shoot up like a rocket or does it stay at 5000ft pretty much?

(mine stays there and it should not since it is trimmed for 220kt))

 

Please let us know.

 

Our problem here is with manual trim, not with how the AP trims, that is why I ask you to disconnect the AP.

 

Regards and Thx :-)

Hi Rob,

 

I have already done something similar, which is why I tried doing it again with the AP.  I agree with you that at the higher speed it is trimmed just as it was at the lower speed, so it stays level when released. That doesn't surprise me now I see that the stab trim position is the same for both speeds. This is probably a problem with the pitching moment model. I believe this is the cause of the trim problem, not a flaw with the FBW, which may well be trimming for the new speed but the trim is the same. The sim has neutral longitudinal static stability, therefore trimming at a new speed is not necessary.  At least that is how it appears to me.

 

Kevin

That explains it!! Without flying the raw FS flight model of the 777 it is hard to tell, but generally FS aircraft are far too stable, and very insensitive to speed changes. I guess the 777 is no different here. :(

 

Best regards,

Robin.

777 simmer I tried your test and got a completely different result, with the trim behaving just as it does in the 200 LR's I fly. AP off with AT engaged and speed changes with out of trim conditions resulting. Maybe a problem with your joystick setup?

 

kind regards,

K

Cowl the FBW system on the 777 does not trim for speed changes only for configuration changes. This was an intentional design concieved to give the pilot a feedback response from the aircraft to changing the flight path of the aircraft. Configuration changes are not intended to change flight path and therefore are trimmed out automatically by the FBW system. The design is true to the real airplane I can assure you.

 

regards,

K

Ok, I seem to have been messing up who is who here.

I confused Kevin for K (pilotsresponse)

 

Kevin, ar you a rw 777 pilot as well?

I did not notice the actual tab trim values are the same at both 220 and 320kt.

Good find!

I will take a look at that too.

 

The test I asked you to was actually for K.

but thanks anyway :-)

777 simmer I tried your test and got a completely different result, with the trim behaving just as it does in the 200 LR's I fly. AP off with AT engaged and speed changes with out of trim conditions resulting. Maybe a problem with your joystick setup?

 

kind regards,

K

Cowl the FBW system on the 777 does not trim for speed changes only for configuration changes. This was an intentional design concieved to give the pilot a feedback response from the aircraft to changing the flight path of the aircraft. Configuration changes are not intended to change flight path and therefore are trimmed out automatically by the FBW system. The design is true to the real airplane I can assure you.

 

regards,

K

 

 

Cowl the FBW system on the 777 does not trim for speed changes only for configuration changes. This was an intentional design concieved to give the pilot a feedback response from the aircraft to changing the flight path of the aircraft. Configuration changes are not intended to change flight path and therefore are trimmed out automatically by the FBW system. The design is true to the real airplane I can assure you.

 

We are already aware of that.

 

777 simmer I tried your test and got a completely different result, with the trim behaving just as it does in the 200 LR's I fly. AP off with AT engaged and speed changes with out of trim conditions resulting. Maybe a problem with your joystick setup?

 

Doubtful it's our controllers, several of us have this issue all with different controllers.

 

In your test, when you increased speed, did you maintain zero vertical speed with elevator input? If you do, you will find that once the speed is stabilised, it's magically in trim. There seems to be an automatic trimming effect with elevator input, without the pilot having to adjust trim as the speed increases. This we believe is wrong.

777 simmer I tried your test and got a completely different result, with the trim behaving just as it does in the 200 LR's I fly. AP off with AT engaged and speed changes with out of trim conditions resulting. Maybe a problem with your joystick setup?

 

the 777 does not trim for speed changes

 

The design is true to the real airplane I can assure you.

 

regards,

K

Thx for doing this test K.

I fly the 777-200ER but I am pretty sure they work the same haha.

Things are however getting more confusing now I am afraid and I must ask you to do the test again and reply in an absolutely definate non confusing way.

(not saying your reply was not ok.....I just need it even simpler)

 

when you say...."AP off with AT engaged and speed changes with out of trim conditions resulting"

 

That means you do have to trim.

And it means you DID trim!

I/we all here want to know what happens if you do not trim please.

 

Please, I need a reply to the following question.

And the reply must be either;

a) yes it shoots up,

or

b ) no it stays right there in 5000ft

 

 

No other answere please (as it confuses things).

 

Here is the question/scenario again.

Do the maneuver with AP disengaged please.

 

Level flight,5000ft or so trimmed for 220kt.

 

!!!!Now DO NOT touch the trim switches at all please!!!!

 

Just maintain 5000ft or whayever with the yoke

 

Now set 320kt and let the AT accelerate the plane.

when stable at 320kt

 

!!!!!without ever, not even once, having touched the trim, this is critical!!!!!

 

let the plane go.

What does it do?

Shoot up like a rocket or does it stay at 5000ft pretty much?

(mine stays there and it should not since it is trimmed for 220kt)

 

Thx for taking the time.

What are the best settings for Saitek flight yoke? More sensitive or less? I don't find anything about this in the documentation. At Airbus from Aerosoft, you must set it to extreme sensitive that fly by wire work well. What is the best setup for my Yoke?

 

PS: On final i use only throttle to get more VSPEED or less. Like a fighter pilot. Works pretty cool.

Question:

 

If i make an attitude of 5° nose up and i fly a left or right turn, the 777 will not hold this 5° like an airbus. Same if i reduce throttel. The nose goes down. Is that ok? Sometime i set 5° and the nose is going down and up and down and hold then 5° seems like to pending to 5°. Are this all things normal?

Question:

 

If i make an attitude of 5° nose up and i fly a left or right turn, the 777 will not hold this 5° like an airbus. Same if i reduce throttel. The nose goes down. Is that ok? Sometime i set 5° and the nose is going down and up and down and hold then 5° seems like to pending to 5°. Are this all things normal?

The 777 assists you in trying to maintain your flight path.

Not necessarily pitch attitude.

 

So in a left or right turn it "knows" you need more pitch to maintain your for example level flight and adds a little pich automatically.

That is normal.

 

Boeing is different from airbus.

 

I dont quite understand you thrust problem I am afraid.

Thanks for your answer.

 

I know 777 FWB is not equal Airbus FWB. But i must understand this how it works and at the moment i have a feeling to fight with plane not flight the plane. At final approach i can work with this plane like a fighter pilot... Its very stable and with reduce or increase thrust i can reduce or increase vertical speed. I love this.

 

My thrust problem is answered i think. At Airbus you set pitch of 5° and a bank of 5°. If you reduce or increase thrust, airbus FBW will hold both. Only thing is that VS goes less or more. 777 don't do this. If you reduce thrust nose go down... What my experience are, that the nose is wiping up and down. The trim number i see via FLTC is the same the number goes up and down. I don't know if this is normal.

777simmer and other friends, my experience is exactly as the FCTM says, that the FBW system "minimizes the airplane pitch response to thrust changes, configuration changes" I think minimizes is the key word here, it's not intended to take all the response out, but to minimize.

 

Here is the confusion you may have.

 

Thrust changes do not mean speed changes. As in the real airplane when you add or decrease thrust at a constant speed, you must apply control column pressure to maintain attitude, but you will notice minimal change in trim. For example, If you apply pressure on the control column to hold a level attitude, as you add and take away thrust the FBW system will help you in maintaining a constant attitude as advertised and minimizes pitch changes, minimizing change in trim.

 

Once you reach a new target speed you are no longer adding thrust or removing it, that is why your attitude remains constant and the FBW helped you achieve this with minimum pitch change as you held the yoke at constant pressure. Now you are at your new speed, and are NOT changing speed, so this is not an out of trim condition for the FBW. You are instead flying a constant speed (albeit a new one) and the FBW worked as advertised by helping you as you applied pressure on the column to get there with a minimum pitch response, and you are in trim.

 

Now, on the other hand if you let go of the control column in level flight and accelerate the aircraft, thereby changing thrust and speed the FBW will try to MINIMIZE the impact of the trust change which would otherwise cause a large pitch up moment. You are not helping now so there is only so much it can do, and it will not assist in trimming the A/C AS IT CHANGES SPEED, thereby you will notice the aircraft pitch up and stay up as the aircraft losses trim.

 

A telling statement in the FCTM reveals why the system is designed this way, it states "The pilot still needs to trim for speed changes. Column forces increase when out of trim to provide the conventional speed error cue." The dumbed down FBW is a safety feature which helps pilots be aware they are speeding up or slowing down by feel even if they haven't noticed it by sight!

 

How cool is that,

 

Cheers,

K