Why aircraft is power up by 115V 400Hz on ground?

Question

Why aircraft is power up by 115V 400Hz on ground?

Answer 1

The question, which wasn't answered above, is why is the aircraft powered on the ground. The electrical systems on the aircraft are powered by the generators that run only when a least one engine or the APU is running. In order to have things like interior lights so you can find yor seat, and to have the aircraft navigation systems ready to program the next flight information into, the aircraft has to be powered on the ground. Also, many aircraft need electrical power to open and close the cargo doors to load and unload baggage.

Answer 2

Drw2 stated "Nowadays, the APU doesnt provide for pneumatic air directly, tho some of the older designs still do. The APU is quicly becoming an electrcial source only."  Not entirely accurate.  Our new 777-200 has an APU that is such a powerful pneumatic source, that it can start BOTH engines at the same time.  HUGE volume of air.  Not just for electrical.

The weight savings is the thing.

Answer 3

Richard nailed the 400 hz requirement.  lighter cable weight for smaller wires.

the hierarchy for engine ops:  two mains in flight. one main during taxi and the APU for ops at the gate.  

if the gate operations are to be extended and power is locally available (not a start cart) then plug it in.  The APU accrues hours like a main engine and burns at least 400 pph for the small RJ's and 1100 pph for things like the A380 and 787.

Nowadays, the APU doesnt provide for pneumatic air directly, tho some of the older designs still do.  The APU is quicly becoming an electrcial source only.

Funny but there are only 1 or 2 that provide electrical power with modern power supplies.  Almost all use the old Lucas style generators or generator/constant speed drive systems (to maintain that 400 hz output).

wer

Answer 4

Don't know if its true but in one of our training we talked about that and the instructor told us that the only reason they made the freq 400Hz is  so that the aircraft instruments couldn't be use at home (stealing it). Otherwise the fence market will be flooded with aircraft parts for home use.

Though there is an outlet for aircraft cleaners use for their vacuum cleaners and its 110v 60Hz.

Answer 5

Higher than usual frequencies, such as 400 Hz, offer several advantages over 60 Hz – notably in allowing smaller, lighter power supplies to be used for military hardware, commercial aircraft operations and computer applications. As aircraft space is at a premium and weight is critical to aircraft engine thrust and fuel burn (and thus the aircraft range and engine horsepower per pound), 115 volts at 400 Hz offers a distinct advantage and is much better than the usual 60 Hz used in utility power generation.