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Strange Aircraft Noises  
User currently offlineToering From United States of America, joined Jul 2005, 176 posts, RR: 0
Posted (8 years 1 month 1 week 2 days 14 hours ago) and read 4525 times:

After start-up and during taxiing to the runway, the NW A319 I was on had a some strange sounds coming from the under side of the aircraft. This odd sound, sounded like a screw or some jack below, intermittent, somtimes lasting anywhere from 5 seconds to 30 seconds. I have heard this sound before on A320- 319s but not this much. The pilot stopped the aircraft on the taxi way, and the FA were looking out the windows, over the wings, with a concerned look. We were there for a short while, took off, and I still heard the sound ..... even after we took off, but ended shortly after. No word as to what was going on. The passengers were making comments about the sound.
What was this sound? And why so much of it ( much more than I have ever heard)?
Can anyone discribe the different sounds that you hear on aircraft, ie, flaps, gear, cargo doors, midgits with hammers?
Thanks

20 replies: All unread, jump to last
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (8 years 1 month 1 week 2 days 14 hours ago) and read 4528 times:

Flap motor, hydraulic pumps.....


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 2, posted (8 years 1 month 1 week 2 days 13 hours ago) and read 4496 times:

They were probably taxiing on one engine, and you were hearing the PTU pump...this is the pump that keeps the other hydraulic system pressurized when one hydraulic pump isn't working. It should have gone away once the second engine was fired up, so if you were still hearing it after takeoff, I'm sure they may have been concerned that there was a hydraulic system problem.

To me, it sounds like the drill at the dentist's office. It starts and stops very abruptly (no spin-up or spin-down sounds) Big grin



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineTUSaadvantage From United States of America, joined Oct 2006, 160 posts, RR: 0
Reply 3, posted (8 years 1 month 1 week 2 days 7 hours ago) and read 4369 times:

I've had the exact same experience on A319s. A couple years ago I noticed it on a NW A319, and this summer on 2 BA A319s. That screwing sound makes me think the plane is not very sturdy. Not to bash airbus, but the engines on the A319 sound pretty whinny and pathetic as well. They sound like hair dryers.

User currently offlineFilton From United Kingdom, joined May 2006, 51 posts, RR: 0
Reply 4, posted (8 years 1 month 1 week 2 days 6 hours ago) and read 4334 times:

It's more than likely the Power Transefer Unit - a pump/motor combination located in the Main Landing Gear bay that transfers hydraulic power mechanically between the green and yellow systems, which are powered by different engines. It makes a terrible noise - no need to be concerned.

User currently offline757lgw From United Kingdom, joined Dec 2003, 152 posts, RR: 2
Reply 5, posted (8 years 1 month 1 week 1 day 13 hours ago) and read 4200 times:

are you sure its not more of a grinding sound, the A32s seems to make a grinding sound after/during engine start up, the weirdest noise ive heard is on the BAe 146 is some high pitch noise that starts when approaching the runway and stops after take off , and then starts again shortly before landing .

User currently offlineDl757md From United States of America, joined May 2004, 1562 posts, RR: 17
Reply 6, posted (8 years 1 month 1 week 1 day 12 hours ago) and read 4188 times:

Quoting KELPkid (Reply 2):
They were probably taxiing on one engine, and you were hearing the PTU pump



Quoting Filton (Reply 4):
It's more than likely the Power Transefer Unit

Probably not if it occurred during and after T/O. More likely the flap drive motor.

DL757Md



757 Most beautiful airliner in the sky!
User currently offlineYEGer From Canada, joined Aug 2006, 43 posts, RR: 0
Reply 7, posted (8 years 1 month 1 week 22 hours ago) and read 4077 times:

I fly A319/20/21s all the time--and this noise happens on almost all flights/airlines before/after takeoff. I finally asked a pilot one day what the noise was, and he said it was hydraulic equalization pumps.

I must say, the A319/20/21 is one wierd sounding bird. There are those screw/saw sounding noises, high-pitch squeeling noises, other odd noises. But they happen all on the ground. Once in the air, the bird is a fairly quiet machine. For this size of aircraft, I do perfer the 737NG series--seem a little more refined.


User currently offlineKelebek From Austria, joined Oct 2006, 60 posts, RR: 0
Reply 8, posted (8 years 1 month 1 week 21 hours ago) and read 4038 times:

the terribles sound I ever notices is the gears-sound on a Canadair Reginal Jet. (OS operates some of them).
When they extend the gears before landing it does a crack that you think for a second the plane lost a wing or something like that. Terrible.
And you don't just hear it you also really feel it.
I guess it's when the gears are unlocked from stewing position etc.
First time I was really concerned, but kept cool cuz of the F/As not reacting at all about the noise.
Actually they are always a very good indicator for me.
Once I went into Mallorca/Spain and we had to do 2 go-arounds and after the second the F/As really got cream-faces and worrying - this wasn't a too good feeling for me..


User currently offlineEGNR From United Kingdom, joined Feb 2004, 513 posts, RR: 0
Reply 9, posted (8 years 1 month 1 week 21 hours ago) and read 4011 times:

My experiences so far...

Britannia Airways B762- No odd noises
Dan-Air BAC 1-11-500 - The engines were incredibly loud, and would likely have drowned out any other noises if they did happen
British World Airlines BAe 146-300 - flap operation generated a loud squeal/whirr sound above my head, and there was a sound like a big spring letting go under the floor during the flight
Transwede MD-87 - no odd noises
Flying Colours B752 - no odd noises (brand new aircraft at the time)
Air 2000 B752 - engines sounded like chainsaws during takeoff (this was a relatively old B752)
Flying Colours B752 - no odd noises (older than frst Flying Colours aircraft I flew on - purchased used)
easyJet B733 - no unusual sounds (4 flights on these aircraft)
Ryanair B738 - no unusual sounds, but I expected it to be quieter in the cabin than it really is... (4 flights on these aircraft)
SAS MD-87 - ovens being switched on made a noise like an air-raid siren
SAS A343 - eerily quiet and no odd noises at all



7late7, A3latey, Sukhoi Superlate... what's going on?
User currently offlineF9Animal From United States of America, joined Dec 2004, 5120 posts, RR: 28
Reply 10, posted (8 years 1 month 1 week 21 hours ago) and read 3994 times:

I think you are talking about the sound of the hydraulics. It almost sounds like an alarm under the floor, but at the same time, a drill of some sort. I always hear it on Airbus planes. It sounds like it is coming from the wing area. Sometimes it has a small thump sound with it.


I Am A Different Animal!!
User currently offline113312 From United States of America, joined Apr 2005, 576 posts, RR: 1
Reply 11, posted (8 years 1 month 1 week 20 hours ago) and read 3982 times:

In the early days of airline travel, all of the sounds associated with the airplane were considered unusual to the mostly novice passengers. Thus, pilots made a lot of announcements explaining the noises that would be heard and similar information was provided in booklets for the passengers.

Now, nearly everyone has flown and most people are completely disinterested and unconcerned about the various sounds.


User currently offlineCYatUK From United Kingdom, joined Apr 2006, 811 posts, RR: 0
Reply 12, posted (8 years 1 month 1 week 19 hours ago) and read 3932 times:

Quoting TUSaadvantage (Reply 3):
That screwing sound makes me think the plane is not very sturdy. Not to bash airbus, but the engines on the A319 sound pretty whinny and pathetic as well. They sound like hair dryers.

I can't really understand yor comment. To me it seems like a usual "lets bash Airbus and their engines" comment.

Even if they were like "hair dryers" that would be a BIG advantage for Aribus and IAE for manufacturing silent engines !!!



CY@Uk
User currently offlineTom_eddf From Germany, joined Apr 2000, 452 posts, RR: 0
Reply 13, posted (8 years 1 month 1 week 14 hours ago) and read 3831 times:

Quoting CYatUK (Reply 12):
I can't really understand yor comment. To me it seems like a usual "lets bash Airbus and their engines" comment.

Even if they were like "hair dryers" that would be a BIG advantage for Aribus and IAE for manufacturing silent engines !!!

Well, I think it's not unusual passengers who don't fly more than once a year or so are irritated by the PTU noise during engine startup, as it sounds like some system ist trying to do something but not working properly. I heard passengers talking about it, speculating something maybe wrong with the cargo doors or the brakes.

Other than that, I always found the A320 family extremely quiet for its class, IAE powered aircraft more than CFM powered, as they don't have this chainsaw whine caused by the tips of the fanblades going supersonic on the CFM.


User currently offlineLASOctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Reply 14, posted (8 years 1 month 1 week 13 hours ago) and read 3787 times:

Quoting 757lgw (Reply 5):

it could be the clamshell in the back below the tail.



[NOT IN SERVICE] {WEStJet}
User currently offlineMD88Captain From United States of America, joined Nov 2001, 1337 posts, RR: 20
Reply 15, posted (8 years 1 month 1 week 13 hours ago) and read 3770 times:

I had a FO who would make a similar noise when you pulled his finger. But I wouldn't say it was an unusual noise.

User currently offlineN587NK From United States of America, joined Jun 2005, 302 posts, RR: 1
Reply 16, posted (8 years 1 month 1 week 10 hours ago) and read 3718 times:

pax comment on it all the time, that gets old lol

for the most part though the pax just ask what "that noise is" most of the time they make jokes about it.

I've heard comments like "get that noise fixed" but one time I had a pax say "well I'm sure your aware of the problem with the plane?" I'm like what problem maam, she says "that awful noise" I said oh dont worry its completly normal...then she started arguing with me saying thats not normal(this was during deplaning) I said its completly normal and there is nothing to worry about. She said "THAT IS NOT NORMAL"

What I said to her next was "OK thank you maam, have a good day"
What I wanted to say to her was "Well since you know this aircraft better than we do, can you tell us whats wrong with it? or maybe you can fix it for us?" LOL

Some people honestly believe there is something seriously wrong with the aircraft


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 17, posted (8 years 1 month 1 week 8 hours ago) and read 3673 times:

Quoting N587NK (Reply 16):
She said "THAT IS NOT NORMAL"

I often service cargo aircraft that are carrying horses and the accompanying stable hands and vets. Quite often, these stable hands and vets will be on the ramp with the horses to keep them calm.

The engines on these freighters have fan blades with mid span-shrouds, which makes a very loud and annoying metallic clanging noise when the engine windmills.

I have quite often been pulled up by one of these stable hands or vets who have expressed their concerns with these noises. This is understandable; as apprentices, we were taken to tour the maintenance base for the first time, and we also expressed surprise and concern when we heard those noises.



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTheweave33 From United States of America, joined Jan 2006, 41 posts, RR: 0
Reply 18, posted (8 years 1 month 1 week 5 hours ago) and read 3640 times:

Quoting Kelebek (Reply 8):
the terribles sound I ever notices is the gears-sound on a Canadair Reginal Jet. (OS operates some of them).
When they extend the gears before landing it does a crack that you think for a second the plane lost a wing or something like that. Terrible.

Yeah, I agree.

I was flying with a group of kids once and one of them announced to the passengers just after T/O that we had lost the landing gear.

By the way, I've noticed in the CRJ that halfway through the take off roll there is a seemingly second spin-up (sorry can't remember the correct term at the moment) of the engines. I can't think of what this could be. Maybe the tires?

And another question. My first trip on a Dash-400 was kind of freaky since the engine noise on takeoff reverberated between the rear galley and the front. I can't imagine working on those for a living. Anyway, before takeoff I noticed since it was quite obvious, that the pilots would increase the propeller speed and then suddenly decrease it causing the plane to jerk forward. I noticed this also with other propeller planes. Why do they do that?

And just on a side note, those times when I have those nervous moments on an aircraft knowing that it is nothing, I can't help but to think to myself about those who probably had those kind of moments and didn't live through them. I think recently of the Comair disaster, the GOL crash, the Russian TU-154 accident, and the recent Nigerian crash. In all those incidents, the passengers must have had those initial fears only to have them validated. To me that is such a terrible thing.


User currently offline757lgw From United Kingdom, joined Dec 2003, 152 posts, RR: 2
Reply 19, posted (8 years 1 month 1 week 2 hours ago) and read 3573 times:

Quoting LASOctoberB6 (Reply 14):
it could be the clamshell in the back below the tail.

but its a continuous noise for few miniutes and continues through the take off roll


User currently offlineCharliejag1 From United States of America, joined Aug 2006, 240 posts, RR: 0
Reply 20, posted (8 years 1 month 6 days 20 hours ago) and read 3486 times:

These noises are the auxiliarry hydraulic pumps. These pumps are electric and boost pressure in the systems when it falls just a little bit below the threshold. That is why you hear it on and off. These pumps are switched on anytime on the ground or in a critical phase of flight. Nothing to worry about, I just with the geniuses at Airbus would have placed them somewhere more distant from the cabin floor.

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