B777 vs B747

[cyyap3]

Dear all,

I would like to ask anybody out there if they can help me on the differences between the B777 and the B747 landing gears??



Thanks and Best Regards,

[mach 84]

B 747 18 wheels, B 777 14 wheels, otherwise no differences. both are operated by hydraulic. if you put the gear lever down they extend on both types if you move it up they retract.:ok:

[cyyap3]

Thanks there!! That was what I thought too but apparently there are more difference to it. What about the steerable outer wheels on the main landing gear of the B747?

[showtime777]

The rear most axle of both the 777 MLG bogeys steer when nose gear steering angle steered exceeds 13 degrees to prevent tyre scrubbing.

On the 747 believe the whole body gear bogey steers.

[on_the_right]

The 777 Landing Gear is unlocked by hydraulics, and it free falls to extend !

[A-V-8R]

I'm dating myself here, but on the Rope Start 747's there was an intermediate position of the landing gear called Speedbrake.

I'm older than dirt and have forgotten more than I know about flying, but I think just the center gear came down when the handle was placed in Speedbrake.

Never saw it used in the 3 years I was on the aircraft.....

Nothing like that on the 777 I fly now.

[point8six]

A-V-8R - that's a new one on me! Do you mean body-gear when you say centre-gear? The only positions for the gear lever that I know are "up-off-down". The earliest 747 I flew had it's first flight in May 1970 and I have not heard of a section of landing gear usable as Speedbrake. Are you sure that you are referring to the B747? Of course it may have been customer-specific and perhaps "modded-out" at a later date.
To answer another query, the body-gear has steering capability - it turns the wheels in the opposite direction to the nose-wheel, thereby reducing the turn radius. It is selected by the crew on the -100/200/300 and automatically on the -400.

[tom744]

one big difference you find in the cockpit;
unlike other airplanes, where you find the "up", "off" and "down" position of the landing gear lever the 777 hase only 2 positions, "up" and "down"; means it depressurizes the system automatically after retraction.
I'm not rated on the 777 just saw it when I was dead heading on a company ship; maybe 777 drivers can expain it better.

[showtime777]

you are right about the automatic depressurization of the landing gear hydraulic system. your words seem to be taken right out of the FCOM. :ok: only thing to add would be that this occurs after the doors are closed as well. Any anomalies in retraction times would be flagged out as GEAR DISAGREE on the EICAS.

[in FACT is]

st777, is it correct that 777 have an auto rudder, I don't know what you call it to correct the yawing effect in case of engine failure, is it for both rudder upper/lower

[showtime777]

the auto rudder you speak of is controlled by the yaw damper which provides turn coordination and dutch roll damping.

the yaw control for an engine-out situation is provided by the TAC (thrust asymmetric compensation), also effecting the rudders.

the above are two different systems which put in rudder inputs automatically without pilot intervention.

[Flaperon777]

"The rear most axle of both the 777 MLG bogeys steer when nose gear steering angle steered exceeds 13 degrees to prevent tyre scrubbing."
Just like what S777 said except that the MLG bogey steering primary purpose is to reduce turning radius,especially in the much longer -300ER's.More importantly is the fact that the rearmost axels of both MLG bogeys turn in the OPPOSITE direction to that of the nose wheel.This,once again is to compensate and enable a smaller turning radius...
Happy taxying....

[in FACT is]

Thank's for info, have nice flight:ok:

[747dieseldude]

In a 747, if either the wing or body gear fails to extend, you're ok.
In a 777, if half the main landing gear fails, you're going to scratch the paint off an engine.

[BelArgUSA]

A-V-8R -
xxx
You are correct about 747 gear speed brake position.
Intermediate position between OFF and DN existed in old 747-100s.
It was used to extend the body gear only, as an aerodynamic brake.
xxx
Never used it - was before my days...
But flew old planes where I could see position markings painted over.
xxx
Position deleted when VLO (EXT) increased from 240 to 270 IAS in early days.
Seen early emergency descent ck-lists. It included extension of body gear.
Then they changed to "extend gear" (all of them)...
And finally, came the option, emergency descent gear UP, or DN.
xxx
:8
Happy contrails

[Maple Leafs]

The 777 can withstand a landing of over 2.5 g’s without the gear being changed or bending the fuselage. Trust me I know. Ouch.:{