Why the whoop whoop noise on NWA's DC-9's

[NuGuy]

Why would you be starting engines *after* powerback? Seems a powerback would be much more sucessful with the engines running.

Sometimes one is shut down on the taxi out after the power back. That whole gas saving thing.

In other gas saving news, NWA is investigating having the first officers fitted with horse yokes and pulling the aircraft out to the runway.

Nu

 

[PA31Ho]

i hear the same thing on the B1900 when starting the engines, always wondered what that was

 

[atpcliff]

Hi!

Would it be the GPWS self-testing when it is powered up? The engines start and the generators come on line, so the GPWS automatically does that? I don't have any GPWS on the plane I fly, so I don't know that much about how they work.

On another note, I read a memo from the CEO of US Air to some ground guys at Philly. They had a -767 going to Europe, and the tugs were broken at 2am. So, they got a bunch of ground guys and physically pushed back the -767 out of the gate!

Have A Nice Day!

Cliff
ABY

 

[PA31Ho]

atpcliff - the sound I am talking about isn't a woop woop as in "woop woop pull up pull up" - not sure exactly if i'm hearing the same noise they are talking about though.

 

[B727-100QF]

What you are hearing is the alternate hydraulic pump. It makes a whining sound as it reaches full pressure and cycles.

 

[PhatAJ2008]

On another note, I read a memo from the CEO of US Air to some ground guys at Philly. They had a -767 going to Europe, and the tugs were broken at 2am. So, they got a bunch of ground guys and physically pushed back the -767 out of the gate!

Must have been interesting to see.

 

[PA31Ho]

why would i hear it through the headsets?

 

[PCL_128]

What you're hearing is the igniters. You'll notice that you only hear it when the PA is being used by the FAs. If they stop using the speakers, then the noise stops. It's due to the low shielding that the speaker wires have, and they pick up the distortion from the high-power electricity coming from the igniter boxes. I used to hear the same thing in the BE1900 when I was wearing a headset during engine starts.

 

[Gorilla]

It is the igniters, not the hydraulic system. DC-9 igniters are badly shielded and bleed through pretty much any headset cable in the airplane. IIRC it is a big capacitor which is charged prior to delivering its jolt through the combustion chamber. Think of a camera strobe charging prior to its flash... same deal.

 

[GINCHBLASTER]

What you're hearing is the igniters. You'll notice that you only hear it when the PA is being used by the FAs. If they stop using the speakers, then the noise stops. It's due to the low shielding that the speaker wires have, and they pick up the distortion from the high-power electricity coming from the igniter boxes. I used to hear the same thing in the BE1900 when I was paying to wear a headset during engine starts.

Fixed it for you.