B737 shutdown checklist question

[Nigel C]

One for the jockeys...

When the B737 parks on the bay and the engines are shut down, the anti-collision beacons are usually left on for typically a lot longer than other aircraft types.

Is this just where the 'flick beacons off' part of the shutdown checklist is located, or is there an operational reason for leaving them on longer compared to other aircraft types?

Cheers.

[Mick B]

We wait til the engines spool down below 15% N2 before turning the beacon off.

As far as I'm aware, most other aircraft turn the beacon off almost immediately after the engines are shutdown.

And yes, I agree it does seem like a long time.

[Nigel C]

Thanks Mick,

Is there a particular reason for waiting for it to spool so low?

[Philip Argy]

Just my speculation, but could it be that the B737 is so low to the ground that sufficient danger exists around the intakes until they've spooled down, so the beacons help ground staff know when it's safe to approach the vicinity of the engine nacelles?

[Mick B]

Is there a particular reason for waiting for it to spool so low?

I've wondered that myself, and I was of the same belief as Philip, that the engines are closer to the ground and therefore prevent more of a hazard.

Not sure what the A320 checklist calls for, but given that the CFM56 is fitted on some of these, it would be interesting to see whether the same procedure is followed, even though they have a higher ground clearance.

[D Chan]

I think Philip is on the right track with lower ground clearance of the engines - recall seeing the graphic images of the Continental 737 engine at El Paso.
http://www.boeing.com/commercial/aer...icle_04_1.html
http://www.airliners.net/aviation-fo...d.main/160175/

[Philip Argy]

I see from the full article that Boeing recommends that ground personnel stay outside the ingestion hazard zone for at least 30 seconds after the engine lever has been placed in the cut-off position. It sounds to me as though 30% spool rate would be a close approximation and therefore leaving the beacons operating until that point has been reached is actually a neat way of communicating to ground staff when the ingestion hazard has been reduced to an acceptable level.

[Kurt A]

...to an acceptable level of ingestion, lol

[Trent C]

Mick

A320 beacon is left on until 30sec after shutdown. 30 sec equates to N2 about 10% so I usually wait until it's been thirty seconds AND both N2 indications are below 10%.

[Philip Argy]

Originally Posted by Kurt A

...to an acceptable level of ingestion, lol