Go Back  FlyerTalk Forums > Travel&Dining > TravelBuzz
Reload this Page >

strange noise from a 777

strange noise from a 777

Old Dec 20, 11, 7:44 am
  #1  
Original Poster
 
Join Date: Aug 2009
Posts: 368
strange noise from a 777

Very often, when my AF 777-300 arrives at the gate and shuts off engines, I hear a strange noise for about 20 seconds. I can only describe this as someone sawing wood or running a zipper back and forth.


Any explanations out there?
ente_09 is offline  
Old Dec 20, 11, 7:58 am
  #2  
 
Join Date: Nov 2006
Programs: Flying Blue, easyJet Plus (!)
Posts: 1,762
You get this on Airbus A320 series aircraft as well, mainly when only one engine is running. It's a device that equalises pressure between the multiple hydraulic systems.

http://en.wikipedia.org/wiki/Power_transfer_unit
pacer142 is offline  
Old Dec 20, 11, 9:30 am
  #3  
 
Join Date: Mar 2011
Location: YOW
Programs: AC SE, SPG Plat, FPC Plat, Marriott Plat, Hilton Diamond, Hyatt Diamond
Posts: 552
LOL I always wondered the same thing. Another useless fact for me
YOWzer is online now  
Old Dec 20, 11, 10:15 am
  #4  
A FlyerTalk Posting Legend
 
Join Date: Apr 2001
Location: NYC
Posts: 69,156
Another possibility is the opening (or closing) of cargo doors. Those are often controlled by a screw drive and the amount of time the sound is being heard is about the same as what it takes to get the door open.
sbm12 is offline  
Old Dec 20, 11, 11:12 am
  #5  
 
Join Date: Aug 2009
Location: ATL
Programs: DL PM
Posts: 64
I can only describe this as someone sawing wood or running a zipper back and forth.
Excellent description of the noise! . . . I knew immediately exactly what you were talking about.
rmalamud is offline  
Old Dec 20, 11, 11:18 am
  #6  
FlyerTalk Evangelist
 
Join Date: Nov 2003
Location: Frisco, TX
Programs: The Airline Run by Doug P
Posts: 17,962
Interesting. I've never heard that noise on a Boeing aircraft. Thought it was indigeneous to Airbii only. Guess not!
enviroian is online now  
Old Dec 20, 11, 2:17 pm
  #7  
FlyerTalk Evangelist
 
Join Date: Nov 2004
Location: ORD
Programs: UA 1K
Posts: 15,960
Originally Posted by enviroian View Post
Interesting. I've never heard that noise on a Boeing aircraft. Thought it was indigeneous to Airbii only. Guess not!
I also though it was Airbii only, and the linked wikipedia article even mentions this:

The PTU on the Airbus A320 family of aircraft makes a distinctive noise resembling a barking dog or sawing, and is quite audible from inside the cabin. Passengers on board A320-family aircraft are therefore very familiar with the sound of the PTU, but few know what it is.

I've never heard it on a 777 or any Boeing AC for that matter.
milepig is offline  
Old Dec 20, 11, 2:36 pm
  #8  
FlyerTalk Evangelist
 
Join Date: Nov 2003
Location: Frisco, TX
Programs: The Airline Run by Doug P
Posts: 17,962
Originally Posted by milepig View Post
I also though it was Airbii only, and the linked wikipedia article even mentions this:

The PTU on the Airbus A320 family of aircraft makes a distinctive noise resembling a barking dog or sawing, and is quite audible from inside the cabin. Passengers on board A320-family aircraft are therefore very familiar with the sound of the PTU, but few know what it is.

I've never heard it on a 777 or any Boeing AC for that matter.
Interesting. Come to think of it I've only have heard it on a 320. I've been on the 318,319, 321, 340, 330...nope never heard it either.
enviroian is online now  
Old Dec 20, 11, 6:42 pm
  #9  
TA
 
Join Date: Nov 1999
Location: if it's Thursday, this must be Belgium
Programs: UA 1K MM
Posts: 6,128
http://www.flyertalk.com/forum/unite...ics-sound.html
TA is offline  
Old Dec 20, 11, 6:43 pm
  #10  
 
Join Date: Jan 2005
Location: yyz
Programs: Non-Rev Lifetime
Posts: 1,918
Originally Posted by sbm12 View Post
Another possibility is the opening (or closing) of cargo doors. Those are often controlled by a screw drive and the amount of time the sound is being heard is about the same as what it takes to get the door open.
Bingo!
PropWasher is offline  
Old Dec 20, 11, 7:28 pm
  #11  
FlyerTalk Evangelist
 
Join Date: Jun 2002
Location: n.y.c.
Posts: 13,362
Originally Posted by sbm12 View Post
Another possibility is the opening (or closing) of cargo doors. Those are often controlled by a screw drive and the amount of time the sound is being heard is about the same as what it takes to get the door open.
Sounds similar to the screw drives in the wings?
nerd is offline  
Old Dec 21, 11, 6:03 am
  #12  
 
Join Date: Nov 2006
Programs: Flying Blue, easyJet Plus (!)
Posts: 1,762
Originally Posted by enviroian View Post
Interesting. Come to think of it I've only have heard it on a 320. I've been on the 318,319, 321, 340, 330...nope never heard it either.
Happens on all EZY A319s and 320s.

Neil
pacer142 is offline  
Old Dec 23, 11, 8:12 am
  #13  
 
Join Date: Oct 2010
Location: CLT
Posts: 181
Originally Posted by nerd View Post
Sounds similar to the screw drives in the wings?
I'll guess you are thinking of the flap and slat drive systems...

Depending on design (electric or hydraulic driven), you might hear the motor drives for these when the flaps/slats are extended/retraced. This will depend on ambient background noise levels though.

For the OP, I would agree with the other posters about the sound being the cargo door operating system
CLTmech is offline  
Old Dec 23, 11, 10:42 am
  #14  
 
Join Date: Aug 2008
Location: ABQ, LAX, ORD, TLV and beyond
Programs: Mostly a free agent nowadays: UA,AA, LH, DL; Starriott (er, Bonvoy); Hilton; Amex Plat
Posts: 1,581
Cranky Flyer once likened the sound to a "dying seal."
zcat18 is offline  
Old Dec 27, 11, 4:49 pm
  #15  
 
Join Date: Jan 2005
Location: yyz
Programs: Non-Rev Lifetime
Posts: 1,918
Other noises to listen for

One thing about older B-747's there was no visible indication at the door switch for the ground person to confirm the door was latched. You had to listen for it.

Just because the door was flush didn't mean it was latched.

A motor rotates the cams around the pins, securing the door. A ground worker depresses a lever on the outside of the door, which mechanically swings the eight lock sectors into place over the latch cams, blocking them from rotating open. The sequence, which takes less than 30 seconds, is reversed to open the door.
http://community.seattletimes.nwsour...3&slug=1307064

I'm still not convinced the door in the above example was properly latched.

On Feb. 24, 1989, the front cargo door of United Flight 811 tore off in flight near Honolulu, sending nine passengers, including 24-year-old Lee Campbell and 61-year-old Mary Handley, to their deaths. The plane was a 19-year-old 747-100 with weak lock sectors, scheduled to be changed sometime in the next 18 months. After that accident, the FAA ordered steel locks installed on all 747s within 30 days.

Last edited by PropWasher; Dec 27, 11 at 5:23 pm
PropWasher is offline  

Thread Tools
Search this Thread