cmh
Posts: 2
Joined: Thu Jul 22, 2010 4:08 pm

ERJ145 "Hairdryer" Noise During Taxi

Thu Jul 22, 2010 4:24 pm

I've wondered for years what this noise is - Embraer RJ-145, and just after coming into ORD yesterday, I hear the captain shut down one engine during taxi, and then I hear a hairdryer-like noise somewhere in the belly, but it changed pitch up and down quite a bit - think of a hairdryer with some massive voltage fluctuation. I thought it might be the APU, but it was clearly coming from underneath instead of the back, and an APU wouldn't change pitch so wildly. All of the flaps and slats were already returned, so it wasn't that either. Ideas?
 
citationjet
Posts: 2251
Joined: Sun Mar 09, 2003 2:26 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Thu Jul 22, 2010 6:10 pm

Quoting CMH (Thread starter):
then I hear a hairdryer-like noise somewhere

It must have been an A340 taxiing by.......
     


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maddogjt8d
Posts: 207
Joined: Wed Oct 21, 2009 3:37 pm

RE: ERJ145 "Hairdryer" Noise During Taxi

Thu Jul 22, 2010 6:12 pm

LOL CitationJet, that was awesome!  
 
DashTrash
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Joined: Mon Aug 21, 2006 8:44 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Thu Jul 22, 2010 6:21 pm

That's an aux hydraulic pump.
 
bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Thu Jul 22, 2010 6:52 pm

Quoting DashTrash (Reply 3):
That's an aux hydraulic pump.

   Yup,
Because

Quoting CMH (Thread starter):
the captain shut down one engine during taxi

and so some of the hydraulic system has to be powered by an electric pump.
Position and hold
 
Western727
Posts: 1426
Joined: Wed Jan 03, 2007 12:38 pm

RE: ERJ145 "Hairdryer" Noise During Taxi

Sun Jul 25, 2010 1:52 pm

Sorry to go somewhat OT but I've noticed a high-pitch noise in the MD-80 (incl. the -88) and the DC-10 while at the gate, though the MD-80's seemed to be of a higher pitch. Electric hyd pump? Thanks in advance.
Jack @ AUS
 
mrocktor
Posts: 1388
Joined: Mon Jan 24, 2005 12:57 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 1:34 pm

Quoting western727 (Reply 5):
Electric hyd pump?

Very likely, if not the APU itself.
 
pilotpip
Posts: 2820
Joined: Fri Sep 19, 2003 3:26 pm

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 5:05 pm

The captain shut down the #2 engine. The result is the electric driven hydraulic pump for the #2 system turning on to power the nose wheel steering. Quite annoying isn't it?
DMI
 
jetdoctor
Posts: 220
Joined: Wed Aug 08, 2001 2:16 pm

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 6:56 pm

Indeed it is the #2 hydraulic pump, and the fluctuation in sound is the demand on the pump, either being the nose wheel steering or brake operation.
I personally find the noise very annoying, and often wonder if the fuel savings from single engine taxi outway the additional hours on an electric backup pump. #2 pumps are always going bad and have to be replaced.

Regards,

Jetdoctor
Break ground, and head into the wind. Don't break wind and head into the ground.
 
ThePinnacleKid
Posts: 497
Joined: Wed Feb 23, 2005 9:47 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 7:49 pm

Quoting pilotpip (Reply 7):
The captain shut down the #2 engine. The result is the electric driven hydraulic pump for the #2 system turning on to power the nose wheel steering. Quite annoying isn't it?

Ummm... actually, that should be the #1 that was shut down... Most people that commute will single engine taxi on #1 because it is quieter in the back for the people because the engine driven hyd. pump would be running and not the elec. pump under the cabin... it is the #1 hyd. system that controls the nose wheel steering and also the culprit with the noise around mid cabin on the 145...

That said, a lot of guys like to single engine taxi on #2, and #2 is started first (during pushback) because when the engine is turning and the eng. driven hyd. pump is running it does NOT power the steering, there by allowing for simultaneous pushback operations... unlike starting #1 which must be done AFTER pushback... when on a towbar type push (non-electro)
"Sonny, did we land? or were we shot down?"
 
pilotpip
Posts: 2820
Joined: Fri Sep 19, 2003 3:26 pm

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 8:18 pm

It's been a while. That's one of the things that's different on the 170.
DMI
 
ThePinnacleKid
Posts: 497
Joined: Wed Feb 23, 2005 9:47 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Mon Jul 26, 2010 10:52 pm

Quoting pilotpip (Reply 10):
It's been a while. That's one of the things that's different on the 170.

I figured as such... hehe... just had to harass a fellow Jungle Jet driver =P safe flyin' mr.
"Sonny, did we land? or were we shot down?"
 
N243NW
Posts: 1597
Joined: Thu Jul 24, 2003 4:29 am

RE: ERJ145 "Hairdryer" Noise During Taxi

Tue Jul 27, 2010 7:29 am

ThePinnacleKid has it spot-on. I've heard the noise many times from the rear of the 145 series, and often I'll try to book a seat farther forward simply to avoid it. Sometimes even a couple rows can make a huge difference.

And yes, it appears that the protocol with many pilots is to taxi out on #2 to enable engine start during pushback and to taxi in on #1 to reduce passenger annoyance.
B-52s don't take off. They scare the ground away.

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