APU

[Four Fishes]

Quick question from SLF (PPL trainee). Does the APU on a 737-700 form part of the MEL? We flew out of ABZ last week on a GSM flight that had earlier in the day been delayed due to the aircraft going 'technical' for about 8 hours. As we boarded via the rear steps the APU sounded awful making almost 'surge' or 'back-firing' noises. After push-back, the pilot announced that we were going to be moved back towards the stand and the engines fired up using an external cart due to problems with the APU. I was somewhat uneasy about all of this - we duly took off and continued on our way to PMI uneventfully.

Any comments?

[BOAC]

No, not required on voyage unless going ETOPS ie USA (from Aberdeen!?). Just nice to have.

[mutt]

According to the FAA Master MEL, the APU is dealt with as follows:

APU
Number Installed = 1
Number required = 0 providing that:
a) Extended Range Operations are not conducted.
b) Procedures do not require its use
c) Visual inspection is conducted of the exhaust area for possible damage.

So its actually a nice to have item, rather than a need to have!

Mutt

[K.Whyjelly]

Never flown a 737 but I would wager my months salary, lets make that my years salary, that the APU is in the MEL.

Speaking for my own type, the MEL states that one is installed and it is acceptable to dispatch the aircraft with it in an unservicable state.....(except for ER Ops with one exception. Depending on the rectification interval i.e B,C or D it can dispatch with a number of provisos including up to 138mins ETOPS dispatch with a u/s APU).

Starting engines is then just a simple case of connecting external pnematic power and then once the engine is safely turning disconnecting the external power and doing a crossbleed start. Can take a while to cool the cabin down in these circumstances unless a/con has been connected during the turnaround.

At the other end it's very important to ensure that the GPU is plugged in before stopping the engines on stand ( which is why you sometimes pull onto stand and sit for a few minutes with the seat belt sign illuminated and twiddle your thumbs wondering why. I tend to let the pax know about this beforehand).

[Pilot Pete]

And it is always worth checking before dispatch that your down-route airfield(s) have a serviceable ground air start machine if the APU is u/s.......;)

PP

[aidoair]

A few times i have been on a 733 or other A/C for that matter with U/S APU's.

As been said its good to have the GPU connected and started on arrival before the engines are shut down, so it doesn't plunge into total shutdown especially at night :cool:. It happened to me before in PMI where the engines were shut down and all the electrics went off as the GPU decided it wanted to play up for a for a few minutes :}.

[ciampino]

Need the APU genny if one engine genny is u/s