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

[flyguyMN]

Everytime I fly an NWA DC-9 before the powerback, there is a Whoop Whoop sound heard throughout the cabin. The same noise can be heard afterwards when the engines starting up. Why is this?

 

[jumppilot03]

I deadhead more than i want to on NWA. I think what you are hearing are the igniters on the engine during the start.

 

[turbinej]

The best thing that I can tell you is it is the ignitor box. Turbine/jet powered airplane and two ignition systems A and B. For starts they are both going on. You here this coming through the PA systems probably. Its just the ignitors lighting. This is all I can say. I hear this in some pax turboprops that I use to fly. I do hear this as well when I fly on the DC-9 as well.

 

[JediNein]

I thought it was the FA and the Captain..What?

Oh, nevermind.

 

[PhatAJ2008]

Why would the engines need to be ignited during flight? Are they shut down?

 

[AlabamaMan!!]

Too insure an ignition source due to low power settings......most if not all jets (never flown a t-prop) are like this. Maybe someone has a better answer though.

 

[LarryinTN]

The ignition on the DC9 is on for start, takeoff, landing and when flying through heavy rain or very strong turbulance.

 

[pilotyip]

You could be hearing the Hyd Alternate Motor pump; it is a Left/Right System mechanical transfer of Hyd pressure as a system back up. On the ground before the engines are started, the Elec. Aux. pump powers the left system and the Alternate Motor pump transfers pressure to the right side.

 

[NuGuy]

I deadhead more than i want to on NWA.

You are free to find your own way to your next flight then...try Greyhound.

Nu

 

[A Squared]

Everytime I fly an NWA DC-9 before the powerback, there is a Whoop Whoop sound heard throughout the cabin. The same noise can be heard afterwards when the engines starting up. Why is this?

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