Jet Questions

[P2T2]

Couple of quick questions for those in the no from someone who isn't!

1. What is the fuel flow on the A340 and 747- 400, and how is it measured (S.G.R, S.F.C
etc)?

2. How is power set on the A340 and the 400
ie EPR, N1 etc?

3. How many spools/fans etc are in the A340
and 747 engine?

Any info on the above or any additional info on the above aircraft engines and their operation would be greatly appreciated (for CX interview).

Cheers and Beers...

[BN2A]

Can answer Q3 for you...
It depends on who makes the engine. GE and P+W make 2 spool engines, RR make 3 spool engines.
http://www.pprune.org/ubb/NonCGI/cool.gif

[Tom Cat]

Answers to the questions regariding the A340:

The A340 engine is the CFM56. It is a twin spool engine. Power is set with reference to N1. There is no EPR guage for the CFM56 engine.

[P2T2]

Thanx guys, that's helped heaps! Any takers for the fuel flow?

Cheers and Beers...

[QAVION]

"1. What is the fuel flow on the A340 and 747- 400, and how is it measured."

Any particular phase of flight??? T/O? Climb? Cruise? Descent? Fuel burn varies dramatically from phase to phase. Since fuel burn is sort of programmable through the Flight Management Computers, this also dramatically affects fuel flow. You could set up the aircraft to give you max economy....or minimum time to destination.

On glass-cockpit aircraft, units of measurement are optional (the display computers are simply reprogrammed as required). Fuel flow can be lbs/hour or Kg/hr.

If by "how is it measured" you mean what kind of mechanical/electrical device is used to measure fuel flow, then...

On some aircraft, a sort of mini propellor is stuck in the fuel pipe going to the combustion chamber. The greater the fuel flow, the faster the propellor turns. The rpm is converted to a theoretical fuel flow value for display in the cockpit.

Rgds.
Q.

[jtr]

QAVION, ATFQ!

The cruize f/f on the 340 ranges from 8t/hr at the for a heavy wt/lowish level cruize, to 6t/hr for opt alt/light wt. As for the -400, I think its around 9-12 t/hr. Measured in kg/hr in CX. There is a kg/anm (or something like that) on the flight plan, but with all the electronic wizardy available for opt alts etc, it is not refered to that often.

340 = N1/2 spool
-400 = EPR/3 spool as with most rollers

Read the `Green Book`, apparently it has most of the up to date info. Or tell me your e-mail, and I`ll fill in any gaps for you.

As an aside, on the 330`s which basically have big RB211`S (400 donks) most guys set thrust ref N1 anyway, EPR is non~sensical.
I know 95% N1 means a lot of noise, but what the hell is 1.15 EPR?



[This message has been edited by jtr (edited 18 September 2000).]