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BoeingGuy

Boeing 777 High-Pitched Whirring Noise

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Hello everyone,I've been watching a bunch of videos of Boeing 777s landing and taking off. What is the high-pitched whirring noise that starts during the takeoff roll, ceases during climbout, starts again during approach, and, most interestingly, starts up again immediately before touchdown?I thought it may have been the flaps motor, but that is a much deeper sound.It's not much different from an Airbus A32X PTU sound, in my opinion.Thanks in advance! :)


Regards,

BoeingGuy

 

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Guest HealthyOne

Example? I can't hear anything unusual having just watched an Air Austral 777 video.

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If it was a BA flight, then here's your answer...What's the difference between a British Airways flight attendant and a jet turbine? A jet turbine stops whining when it gets to the gate. :( Al


Alan Bradbury

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Example? I can't hear anything unusual having just watched an Air Austral 777 video.
During approach you hear it sporadically, and then what puzzles me the most is why it sounds at 6:19 into the video, I hear that in every 777 landing video.
During takeoff, you hear it from 0:48 into the video until about 1:33.
If it was a BA flight, then here's your answer...What's the difference between a British Airways flight attendant and a jet turbine? A jet turbine stops whining when it gets to the gate. :( Al
:( :( B) That was brilliant, Al! I haven't heard a good aviation joke in years! That was it right there! Thanks for the laugh!

Regards,

BoeingGuy

 

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Guest Zingiber

Thanks for providing an example. The sound you hear is the hydraulic system demand pumps which have been activated by the control logic for a high-demand situation (like takeoff and landing). These engage during specific situations, but I can't recall the exact requirements for activation as it has been a long time since my studying of 777 systems.

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Okay, so I wasn't hearing things. I know in one of my videos that I recorded six years ago, I heard something like that in the landing video, but you could barely hear it. Then again, I was sitting much farther from the wing, compared to where the passenger in those videos was sitting. Wasn't sure what it was.


Captain Kevin

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Guest sjfdkw

I think it is the electric motor driven pumps assiting the engine driven pumps during high demand periods of landing gear and flap retraction/extension, braking, etc.I once got a seat just behind the right wing on a vir a346. I couldnt notice such noise though but the flap motor sound was really cool. The right landing gear was close to my location, I felt and heard the thud of closing bay doors and touchdown clearly. I never thought the doors shut so hard against the fuselage.

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Thanks Zingiber,I looked up "777 hydraulic demand pump" and found many answers, all relating to this same whining noise. Do all large jets make this noise, or is the 777 just so large that even its own hydraulics "demand" that much from it?


Regards,

BoeingGuy

 

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Guest sjfdkw

If you looked up you must have found 777 and 744 etc use a third kind of pump called the air driven pump which uses compressed bleed air from engines. It has noisy operation as in air(pneumatic) motors. 744 has it in the engine pylons so not audible.So it depends, if an plane has air driven pumps which are placed in fuselage you will hear the noise.it is not that 777 is large for its pumps. to make things failproof smaller pumps running on different sources are prefered and to maximize aircraft efficiency are used according to demand.

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