Sunken_Lunken
Topic Author
Posts: 87
Joined: Sat Jul 07, 2001 2:48 am

Jungle Jet (EMB-145); Pulsing Apu?

Sat Oct 05, 2002 2:07 am

I was a passenger on an EMB-145 a while ago. When we exited the plane at the gate, I heard a recurring noise that sounded like the APU was cycling on and off. There were several seconds between cycles, but it seemed pretty frequent.

Can the APU on this plane be set to cycle on and off like this? If so, what is the reason?
 
AA777-200
Posts: 305
Joined: Mon Jul 12, 1999 2:58 pm

RE: Jungle Jet (EMB-145); Pulsing Apu?

Sat Oct 05, 2002 2:16 am

What you are hearing is the heat exchangers/air packs down under the wings. They are in an annoying cycle that goes then stops for a few seconds and comes back on. It is a high pitched noise and gets annoying when your working around the aircraft.
 
Sunken_Lunken
Topic Author
Posts: 87
Joined: Sat Jul 07, 2001 2:48 am

RE: Jungle Jet (EMB-145); Pulsing Apu?

Sat Oct 05, 2002 2:32 am

Thanks for the info AA777-200.

I was only around the plane for a minute or 2. I can imagine how annoying that would be hearing it for longer periods several times a day.
 
jetdoctor
Posts: 220
Joined: Wed Aug 08, 2001 2:16 pm

RE: Jungle Jet (EMB-145); Pulsing Apu?

Sat Oct 05, 2002 1:49 pm

Wow you were actually on a 145 with a working APU???

AA777 is correct in stating what you proabaly heard. When the packs are first selected, they cycle up and down until stabilized. Once they are going for a few minutes, they are ok, unless the cabin/cockpit temp is changed, or they are reset.

And AA777, you should be wearing your company appointed orange headgear!!
Remember noise is the invisible hazard!!

RT
Break ground, and head into the wind. Don't break wind and head into the ground.
 
ramper@iah
Posts: 236
Joined: Mon Dec 24, 2001 7:23 am

RE: Jungle Jet (EMB-145); Pulsing Apu?

Sun Oct 06, 2002 2:15 am

Jetdoctor,

Out of curiosity, are the APUs installed on the Embraers at your company considered unreliable? We use the Sustrand C-14 and C-11 models, and have had very little trouble with them. The C-14s tend to get hot during engine starts, but other than that, they work like a charm.
 
jetdoctor
Posts: 220
Joined: Wed Aug 08, 2001 2:16 pm

RE: Jungle Jet (EMB-145); Pulsing Apu?

Sun Oct 06, 2002 4:59 pm

Ramper@iah

Yes, we also use the Sundstrand C11 and C14 APU's on our fleet. Through my experience on aircraft, they seem to be a very unreliable unit, as compared to say a Garrett APU. We are seeing a lot of improvement with the C14, primarily because it is a FADEC controlled unit, but we still have uncommanded inflight shutdowns and numerous APU fails.

Now with winter coming, we get to look forward to glycol ingestion, which really isn't the APU's fault. More like an intake design problem, and a lack of knowledge of the deicing crews (who seem to like to spray glycol directly into the intake)

I am assuming you work for ConEx, and maybe your operating climate is better suited for the APU. Just a thought.

Regards
RT

Break ground, and head into the wind. Don't break wind and head into the ground.
 
AA777-200
Posts: 305
Joined: Mon Jul 12, 1999 2:58 pm

RE: Jetdoctor

Mon Oct 07, 2002 1:12 pm

Soo that means when I deice this winter and fill up the APU with glycol you get to fix it huh?  Acting devilish Yeah yeah I usually wear my nice bright orange ears...but sometimes I forget to grab them ( hope them auditors dont come looking for me)
Brad

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