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Old 23rd Feb 2015, 18:45
  #30 (permalink)  
AAKEE
 
Join Date: Jan 2009
Location: Sweden
Age: 56
Posts: 224
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I know there was a discussion some time ago here on pprune about shutting one engine off if in an fuel emergency at sea. Dont remember the helo type though...

If the 'shut-one-down' was for economy it would be a total other angle about it.
All helos i ever flown( military, different sizes), the fuel is a very little part of the total cost. Only have one FM here so I used it for this example(but from memory, about the same proportions for the other Twins, from qiute small to big): I picked a normal weight, about standard day at 3000'.

(Fuel-) Economical cruise 135kt @ 550kg/h
Max cont cruise AEO: 153kt @ 690kg/h
Max cont cruise on one Engine: 107kt @385kg/h

At 5000E/h; The cost for flying 135Nm(equals 1h economical crusie):
Economical Cruise = 5000E
Max Cruise = 4400E + 72E(72L extra) = 4472E
Max single Engine = 6300 - 80E(80L minus) = 6220E

Seems obvius to keep the speed up. As I said, the other twins had about the same proportions.

If development proceeds(which I doubt) , I guess it would be possible to save some Money on the enginge shut down, but not as much as it differs. I also guess the quick start system would add some weight, both slowing single engine cruise and payload...

[Edit] The helo in the example above does about 4.1kg/Nm in economical cruise and 3.6kg/Nm in single engine so in fuel emergency over sea, I see the Point !

Last edited by AAKEE; 23rd Feb 2015 at 18:48. Reason: Add fuel saving value on single engine
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