B777 Single engine Take-off
 

A few months ago a BA 777 in Riyadh had an engine failure during the take-off roll which was obviously past V1 as the aircraft went airborne. A few guys on board swore that they felt that the thrust of the good engine was reduced as they got airborne. This has caused quite a bit of banter as to if this happened or was perceived to have happened due to lack of cabin noise
My question is does the B777 automatically compensate for asymetric thrust by reducing thrust on the good engine when past V1?
Any B777 guru's answer this one!
Cheers

Adds a whole possible new dimension to the briefing.

"In the event of an engine failure, we always have the option of reducing power on the remaining engine...."

Could the reduction of cabin noise be due to reduced air flow from the air conditioning system? With one engine out, the air flow halves immediately (hence the reduced noise), then as the system stabilize, air flow recovers gradually to "high" flow a while later?


I am on the B747. I am just guessing here.

The aircraft doesnt automatically compensate by reducing thrust, the only immediate automatic reaction AFAIK is compensating for the yaw by use of the rudder.
Although RUH is a pretty high airport, it isnt surrounded by any obstructions, the MFRH surrounding this airport is therefore 400 feet, i dont know what the MFRH BA uses, but it is possible that the aircraft transitioned from a takeoff attitude to an acceleration attitude which would resemble a loss of thrust due to the decrease in climb rate.

Cheers

Mutt.

The answer to the question is: Yes, the B777 does compensate for yaw automatically during a power loss. Actually, there need only be a 10% power loss between the left and right engine to affect thrust assymetry compensation.

The amount of rudder supplied is about 90%, leaving some room for the flight crew to 'fine tune' the final trimming.

I'm not sure of BA's SOP regarding their engine failure procedure, thus can't answer for a possible thrust reduction.

If the aircraft was flown in VNAV, there are several automatic functions that take place during the flight profile and it wouldn't be fair to make any guesses of the flight crew as to what was happening on their aircraft. Suffice to say, the airplane is a breeze to fly when all the automation is working correctly.

"Engine Failure?......Ho Hum...ring the bell and ask for another cup of coffee while this thing sorts itself out"!

OK I know I'm gonna sound ignorant here but what's VNAV (and is this related to something I've heard called LNAV)

VNAV LNAV
 

VNAV = Vertical Navigation. LNAV = Lateral Navigation.

LNAV is illuminated when pushed. Arms or engages LNAV mode. If armed, LNAV is annunciated in white on primary flight displays. Active roll is not affected. If LNAV is armed and the airplane is above 50ft and within 2.5 NM of the active leg, LNAV engages.

Thats a few...

Now VNAV...If VNAV is armed and the airplane is above 400ft with the FMC (flight management computer) Perf Init page completed (Performance Initialisation), LNAV in engaged. Thus, VNAV SPD, VNAV PATH, or VNAV ALT is annunciated on the PFD's (primary flight displays) in green. When VNAV is engaged, the system commands pitch to maintain FMC altitude...

Again, a few...

This is 747. I presume it is the same for Airbus?


Smooth skies
:D

Yes in broad terms. No in detail.

Thanks :D

Simplicity really IS the key to genius then :p

Smooth skies.

The 777 does not reduce thrust to compensate for an engine failure. Among other things, this goes against common sense. During an engine failure, when there is a significant difference in thrust, the TAC (Thrust Assymetry Compensation) automatically applies sufficient rudder in the appropriate direction. The engine thrust will remain at the pre-programmed value unless the auto-throttle is disconnected and the thrust levers are physically moved. Once the aeroplane is at acceleration altitude and clean (gear & flaps up), the thrust will reduce to maximum continuous thrust (MCT) as the aeroplane climbs to the next altitude either in the FMC or the MCP altitude window.

The reduced cabin noise is likely to be due to half the original amount of bleed air being pumped through the air-con and half the engine noise!!

In the meantime, well done to the guys concerned. The outcome was never in doubt.