Boeing 777-300ER Noisy Hydraulics

[bantios]

Ive travelled on many 777's but everytime im on an Emirates 777-300ER the hydraulic noises are very loud. Sounds like 2 cats fighting. It usually happens just before takeoff and about 50ft before we touch down. Is this normal?

Why doesnt the same sound happen on a Singapore 777-300ER?

[Joetom]

Guess you sitting in about same location on these aircraft.

The 777 has two hyd demand pumps (air driven/noisy) near the left wing root, in normal life, they operate if centre hyd press is low and they will run when they see flaps/gear selections, 3 pos switch, off/auto/on.

Auto is the norm position of the swiches, so would expect noise to be similar on all 777, may be the cabin carpet is thicked on the quiet 777, may be some pilots switch them on for T/O and landing.

If my memory right, the 747SP auto switched on (and stayed on) similar if flap setting/position was big, normal landing pos i think.

[Old Smokey]

It's the Air driven Demand Hydraulic Pumps, which, as the name indicates, operate to augment the Engine Driven and Electrical hydraulic pumps during high demand.

Prior to Takeoff, there's a lot of demand, Flaps being set, Braking, Stabilisers being set, and finally the full control check to the limit of their travel.

I can't for the life of me think why it should be noticeable during the landing flare, there's only the Elevator operation, and perhaps a bit of rudder and aileron operation in a Cross-Wind. Perhaps, as Joetom has suggested, Emirates operate with their pumps in the ON position which could account for it. We (SIA), use the Auto position which, with the possible exception of One Engine Inop landing, place very small demand on the system.

Perhaps an M-Rats pilot can shed light on their SOPs.

FYI, the highest hydraulic demand is during gear retraction, but other considerable ambient noise might disguise your hearing it at this time. The ADP contribution during gear retraction is considerable, with one Centre system pump inoperative (allowed), gear retraction is noticeably slower causing a fairly significant 1st Segment Climb penalty.

Actually, I was tempted to say that the B777 cat's fighting were only in response to the hydraulic dogs barking in the adjacent Airbus, but decided to go with a more sensible answer ..... It's a real animal jungle out there!:E

Regards,

Old Smokey

[Khaosai]

Hi,

auto position for the demand pumps here in EK.

Rgds.

[gas path]

Both ADP's run during takeoff to provide rudder authority (thrust assymetry protection in case of engine failure) and again for gear retraction.
One ADP will run during approach for gear and flaps extension and just before touchdown (30ft??) ready for speedbrake deployment.:8
That's for the -200 and I don't see why the -300 should be any different...but!?

[bvcu]

always the possibility you were flying on one with a fault , which would require one being set to 'run' as per MEL . Not totally unknown on 777. couse if you buy a ticket for the front end you dont get disturbed by these noises...........

[bantios]

Thanks ADP u answered my question.

[bantios]

YouTube - Landing in Dubai on Emirates 777-300ER (http://www.youtube.com/watch?v=2C8O6ppKJwQ)

here u can hear it just before touchdown

[sb_sfo]

I ran into a situation where C/As mentioned a vib/noise just before landing, and we found a bad center ACMP.

[msybdin]

Ive travelled on many 777's but everytime im on an Emirates 777-300ER the hydraulic noises are very loud. Sounds like 2 cats fighting. It usually happens just before takeoff and about 50ft before we touch down. Is this normal?

Why doesnt the same sound happen on a Singapore 777-300ER?

I may say it's sound like a werewolf howling tho