Generic Airliner APU Question

[kijangnim]

Greetings,
B777 is approx 340 Kg/H

[mwaugh]

Re: APU cycle cost.

Four words "Power by the Hour".

The bean counter mentality is that if shutting down and starting the APU isn't costing them any more money why worry about it. Now, when the contract comes up for renewal they'll be crying all the way to their bonus, but for now it has "no cost".

[TopSwiss 737]

Greetings Cyclone733;

For us on the B747-400 the flight planning section in our OM-B states:
"Average APU fuel flow rate under normal operation on the ground is 300 kg/hr."
No specifics on the influence of load on fuel flow though.
For example 1 or 2 generators on line (not much difference on the freighter I guess as normally gen 1 is the only one on line. Gen 2 is then used for main deck cargo handling) or 1/2/3 airconditioning packs running... I reckon bleed demand has the biggest impact on fuel flow.

Other aircraft:
MD-11: 200 kg/hr on the ground
150 kg/hr at altitude
B767-300: 115 kg/hr

TS737

[Cyclone733]

kijangnim and TopSwiss 737,

thanks for the replies. Higher fuel burns than I'd expected. I wonder if the A380's APU is a more modern design than the 747's with an increase in fuel efficiency or if APU design is a reasonably static element

[ATP_Al]

Dash 8 300 - APU cannot be used in flight. Burns 100lbs/hour. Shut down once both engines have been started, but company policy is to use ground power instead if our handling agents provide it at no extra cost