My Analysis of the Boeing 777 FBW System

[Alpha Floor 237]

Awesome topic! Thanks for sharing the video

 

Danke sehr Klaus! Glad you liked it!

[Alpha Floor 237]

I'm sure this pitch compensation is supposed be modelled but I haven't tried it much myself. A lot depends on how stabilised you are before starting the turn and whether you make any inadvertant pitch inputs while making the roll input. Increasing the FBW pitch deadband in the CDU might help.

 

 

I'm pretty sure the aircraft will descend if it's rolled, but I will try it out again as you say incresing that deadband to be certain. I also encourage you to try and share your findings!

 

So, I've been running further tests and must conclude that there IS turn compensation. The aircraft might not maintain the altitude EXACTLY and you might observe some vertical speed. HOWEVER; you can see the STAB TRIM adjusting to contain the altitude loss/gain.

 

Also, if you roll into the turn smoothly the system will have more time to adjust than if you roll the aircraft abruptly.

[Alpha Floor 237]

Things that remain unanswered:

• Why doesn't the RUDDER TRIM indication cross out in amber on the synoptic when all systems, and the rudder as well, are failed (see image below)?
• Accuracy of the external model with failed hydraulics/ACEs. I'm inclined to believe this is an FSX limitation. In any case, as long as the aircraft behaves as it should I don't care too much about the exterior model. I fly the plane from the cockpit anyway.

 

Things that remain to be tested:

• Spoilers 4 and 11 operation with all hydraulic systems failed. These spoilers are mechanically linked to the control wheel and, together with the STAT TRIM through the ALTN TRIM on the pedestal would render the plane somewhat flyable in a full hydraulic loss together with RAT failing to deploy. Now, I can't seem to test this for 2 reasons: 1) Failing all four ACEs won't do it because the linkage of spoilers 4 and 11 still requires ACE operation, and 2) Failing all hydraulics will deploy the RAT and I can't seem to prevent the RAT from unlocking.

 

Some odd behavior I just discovered. Playing with the failures, I got to this point. Wheel fully deflected to the left, no. 4 spoiler fully up both in the synoptic and on the external model, but the aircraft is NOT rolling at all:

 

[Lashrathius 49]

Great video! And thanks for all the explanations! This cleared a lot of confusions I had regarding the FBW system on the 777. 

[Alpha Floor 237]

Great video! And thanks for all the explanations! This cleared a lot of confusions I had regarding the FBW system on the 777. 

 

Thank you for watching! Glad you liked it!

[jcomm 5,926]

Another Superb video Jaime!

[Alpha Floor 237]

Another Superb video Jaime!

 

 

My pleasure!

[Alpha Floor 237]

For everyone interested, I wrote an article regarding the 777's FBW on my LinkedIn page here. I think people that followed this thread will enjoy my article.

 

It should be publicly accessible, but if not, I will upload it somewhere as .pdf and post a link.

[jcomm 5,926]

Will certainly give it a read!

 

Your contribution has been, just for itself and the enthusiasm and dedication you have put on it, the single reason for me to re install FSX, and the PMDG 777 :-)  - this, from someone that mainly uninstalls.... means a LOT :-)

 

Thank You Jaime! Keep the excellent work!

 

[Alpha Floor 237]

Thank You Jaime! Keep the excellent work!

 

Thanks José! But I'm much afraid that from now on till November or so I won't, or at least shouldn't, devote so much time to "playing in the sim" because university (hahaha)

 

Thanks again!

[jcomm 5,926]

Yep, University AND girlfriend always in the very 1st place !!!! ( at least we try... but these damn flightsims are soooo addictive :-/ )

 

We want an aeronautical engineer with a special interest in flight simulation - who knows we can have a future "new Bruce Artwick" ? :-)