Non functioning APU
 

:) Hey all

Just wondering...is it safe to fly if the APU is not working?:)

Normally quite OK, however...MEL restrictions might apply.
For example, with the L1011, flights more than 400 NM offshore are not allowed.
In addition, there is normally an MEL time limit on APU unserviceability...ten calendar days in the case of our aircraft.

Yes, perfectly safe.

It is just a little annoying when it comes to engine start (no compressed air available directly) and air conditioning in very hot conditions (the ground supplied air is usually rubbish) or when there is no ground conditioned air available.

To start the engines without the APU we would get the groundcrew to hook up a unit that supplies us with high pressure air. We use this to start an engine, then push back, rev the running engine a bit and use 'bleed air' from the running engine to start the other engine (talking A320, I'm sure it applies to most jets).

:{ had a bad flight last night with angry pax...stuck in the cabin until the GPU could get the engines started..it konked out and we were stranded onboard in the heat for almost an hr.....:sad: I wish it would just get fixed!!!!! how long is the repair time? on a 737?

The repair time depends on what is wrong with it. It can vary from component change to a complete APU replacement.

In the days when you could be a 'Flight Deck Groupie', I was chatting to the FC of a BA 757 from Arlander to LHR. Apparently the APU was inop and they had to start on the shore line. Ordinarily not a problem, they said, but there was a deal of ice about and the tug couldn't push us back without a lot of difficulty. :uhoh:

ROger.

BTW, you will also need an electrical source:E
(at least on the aircraft I've flown):O
Cheers

Colocolo

Lots of drift. Yes an aircraft operates safetly w/o an APU. It is only an aux source of power if all engines fail or their source of electricty fails. There are backups in thi scenario. To worry about flying in an aircraft W/O an operative APU is not worth the effort.

tiggerpurrrz,

As far as despatch and in-flight is concerned, the APU is a source of AC power along with each engine driven generator. It is a requirement that at least two source of AC power are available. With most twin engines aircraft, if the APU is inop and an engine driven generator fails in-flight then there is only one source of AC power remaining. It is a requirement to divert to the nearest suitable (suitable = performance, facilities and weather) airport.

For most twin engined aircraft with an APU inop on a standard short haul operation with nearby enroute alternates available, it is perfectly safe to depart and perfectly legal. For an oceanic/ETOPs flight it is not safe and I would have thought not legal.

A rather dramatic statement about safety.
As for legality, it is based on the specific airplane equipment. Just check the MEL.

DJ.

Safe but potentially inconvenient and there may be restrictions. For me the biggest issue is during the late spring and summer months when a lack of APU often means no air conditioning. So if it is hot and sunny (remember those days?), I'll only board if I can ventilate the cabin. Otherwise I'll either not take passengers or not take the plane.

PM

Not true. Depends on the aircraft.
A B777 can operate ETOPS with an inop APU, but does have two generators on each engine.

The problems with inop APU are mainly cabin cooling. When I worked for Gulf Air we had a house rule. With APU inop you tried to fix it on the first nightstop. If you failed, you changed it on the second.

The problem here in the frozen North is the difficulty in pushing back an aircraft with engines running over an icy ramp.

[quote]Not true. Depends on the aircraft. A B777 can operate ETOPS with an inop APU, but does have two generators on each engine.[/qoute]
I was careful to say "most" ;) As the 777 was designed with Early ETOPs out of the box I should have known :\

Just out of interest, how many gens does the A340 have? My understanding it is a generator in each of the inboard engines.

:confused: Also noticed on this AC that there was water dripping from above the pax to the left of the control panel for reading & call lights, was only in one location..but could this be condensation and related to the APU inop?

That really depends on the aircraft. The APU isn't available for inflight operations in all aircraft.

Be careful without conditioned airflow with a cabin full of pax. This situation can quickly become an acute health hazard, especially in hot climates. If you can't get ground air conditioning within 15 minutes at places like Jeddah in summer, it's an emergency situation and time to get the pax off the airplane. :ooh:

Yes and no. On a humid day it is common to develope significant condensation in the cold air ductwork. Please give up your obsession with an inop APU. I have personally seen passengers come off an airplane who forced a return to the gate due to condensation dripping out of their air vents HOGTIED!

hmmm...sorry..was not obsessed!!!!..just wanted an answer to a question. I don't think you need to be nasty. I am thinking safety ok.

4, 1 per engine.

A330 can be dispatched on an ETOPS sector with an inop APU as well.

You can't even bring the APU electrics on-line when airborne in a B747-400, so certainly not required.

Four paralled electrical systems - without equal.

I am surprised that the L1011 is SO inferior. Tsk, tsk, 411A, what were Lockheed thinking about - you usually suggest that they are infallible - limited to 400nm from the coast - or did you mean an airport?