My analysis of the FBW Sytem of the Boeing 777

00:00 – Introduction
01:50 – FBW Philosophy on the 777
03:43 – System Description
10:36 – PMDG FBW bug on the PFD

12:50 – Trim Change in Normal Law (constant Thrust)
15:50 – Trim Change in Direct Law (constant Thrust)
17:54 – Thrust Change in Normal Law (constant Trim)

21:45 – Roll in Direct Law
23:25 – Roll in Normal Law

25:37 – Lowering the Landing Gear in Normal Law
27:17 – Lowering the Landing Gear in Direct Law

31:11 – Approach to Stall in Normal Law
37:58 – Stall in Direct Law

41:17 – Failures (Secondary Law, Non-Normals…)

LinkedIn related article:

References:
– FCOM Vol. 2 Flight Controls:
– PMDG Tutorial 1 – Fly-By-Wire Flight Control Systems, Major J.P. Sutherland (1968): www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0679158
– The Avionics Handbook, Ch. 11 – Boeing 777 FBW Flight Controls, Bartley: www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf
– More info on the TAC:

Relevant Avsim Threads:

DISCLAIMER: I don’t claim to be an expert on the FBW, The Boeing 777 or any aspect of life for that matter. I really just “learn by doing” and like to share my findings with the community because sometimes they happen to be useful to other people as well. If you happen to find inaquracies, inconsistencies or outright false statements, I’d very much like you to let me know them so that I can correct them.

16 COMMENTS

  1. Sorry. How is it that with the PFCs disconnected you still get the AT protections for overspeeding after applying downward trim? I don't get it.

  2. What is really unnerving is that the plane seems to not apply the trim setting you select until you let go of the yoke, even if you trim in the same direction you pull, this is why its hard to trim by feel in normal law in pmdg 777. Flying without the fbw bug is like riding on bumps, you let go of the yoke completely, look what the nose is doing and then reapply the yoke fast. Flying the 737 or 747 is buttery smooth by comparison

  3. Nice video! Fun to watch thanks.
    I have one question.
    Shouldn't phugoid motion also happen when aircraft is in direct law? I'm curious why aircraft's pitch angle does not change as the speed changes around 17:35. As long as i know, pitch up moment occurs as the aircraft gains speed, and vice versa. This is the nature of phugoid motion, and this motion happens naturally even without the aid of computers. But according to the video, it seems phugoid happens only in normal law, not in direct law.

  4. hey…
    can u tell me which game this is ?
    i play flight sim X , but it does not provide as many features as the game u r playing

  5. Thanks for your fast reply Jamie. I made some manuel landings after your videos. Yes you are right. Its enough to follow Flight director to catch the GS path. Thanks again. I am waiting for your other helpful videos…

  6. Hi Jaime,

    First thanks for this very explainatory video. Everything related with B777 FBW is so clear now. I have newly purchased this great addon and I am trying to familirize the FBW.

    I am trying to make manuel landing with AP off but A/T on. So I am trying to use only trim operation to follow GS line. COuld you please share us with a manuel landing video with these conditions. (A/P off A/T on)

    Tjanks again

  7. Gracias Jaime, muy bien explicado el FBW. Mucho más claro que algunos textos explicativos que sin embargo a veces lo dejan a uno más confundido. Saludos desde México!

  8. Great video ! Can you tell me how is a boeing 777 fly by wire system different from an airbus fly by wire system? I know that in the 777 the pilot can override the FBW and in an airbus it cannot be overridden by the pilot . Are there any more major differences between the 777 and airbus FBW ?

  9. Random fact: Each PFC has 3 microprocessors: Intel 80486, Motorola 68040 and AMD 29050.
    The Motorola belongs to a family of processors also used for video-consoles such as the Sega Saturn. The AMD was widely used in laser printers.The Intel was also used in video-gaming.

    The PFCs are programmed with 132000 lines of Ada code.

  10. +jibeneyto Hi, this is a very good video and I learned so much from this. Do you mind if I use your video as a reference for my video project on Boeing fly by wire system? And maybe I will take a bit of your video or your explanation in this video to compile with mine. Is that alright? Of course I will give you credit for that.

  11. +jibeneyto

    Hi, Jaime
    Great and awesome, as always the case with you're videos 😉

    Two things I noticed. When you disconnected the TAC system though there was quite a lot of symmetry thrust , we didn't see a significant yaw movement to the left.
    Second one is that the elevators while having air flow over them, should not drop completely down even in the presence of a flight control or hydraulic failure. With the elevators we saw in the simulator after 4 ACE failures, the aircraft would have been in a very rapid dive. It is true though in the absence of the airflow, as we see in the videos when pilots do the walk around the elevator is always deflected downward.

    If you agree with disclaimers above, then I think we should inform the PMDG staff. Maybe the would fix it in an upcoming SP.

  12. My analysis of the FBW Sytem of the Boeing 777

    00:00 – Introduction
    01:50 – FBW Philosophy on the 777
    03:43 – System Description
    10:36 – PMDG FBW bug on the PFD

    12:50 – Trim Change in Normal Law (constant Thrust)
    15:50 – Trim Change in Direct Law (constant Thrust)
    17:54 – Thrust Change in Normal Law (constant Trim)

    21:45 – Roll in Direct Law
    23:25 – Roll in Normal Law

    25:37 – Lowering the Landing Gear in Normal Law
    27:17 – Lowering the Landing Gear in Direct Law

    31:11 – Approach to Stall in Normal Law
    37:58 – Stall in Direct Law

    41:17 – Failures (Secondary Law, Non-Normals…)

    References:
    – FCOM Vol. 2 Flight Controls: http://www.smartcockpit.com/aircraft-ressources/B777-Flight_Controls.html
    – PMDG Tutorial 1
    – Fly-By-Wire Flight Control Systems, Major J.P. Sutherland (1968): http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0679158
    – The Avionics Handbook, Ch. 11 – Boeing 777 FBW Flight Controls, Bartley: http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf

    DISCLAIMER: I don't claim to be an expert on the FBW, The Boeing 777 or any aspect of life for that matter. I really just "learn by doing" and like to share my findings with the community because sometimes they happen to be useful to other people as well. If you happen to find inaquracies, inconsistencies or outright false statements, I'd very much like you to let me know them so that I can correct them.

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