> This is probably obvious, but according to my study materials for the
> instrument rating, the efficiency of a jet engine depends on the
> temperature differential between its combustion and the outside air
> temperature -- that's why jets are very efficient flying near the
> tropopause at around -60 degC, but burn more fuel for less power in
> warmer temperatures (i.e. lower). Is YASim taking that into account?
Being a physicist, not a pilot, I would have thought that air pressure
has a much larger effect. After all, the temperature change is rather
small compared to the temperature difference: outside air temperature
changes by maybe 75K between ground and cruise altitude, the
temperature inside the combustion chamber is something like 1500K (or
at least of that order of magnitude, I haven't got figures). Pressure,
on the other hand, changes by a factor of 4 between sea level and
37000ft.
That makes me think -- how come jet engines are so much more efficient
at altitude? Most modern airliners use turbofans with high bypass
ratios, and the bypass part should become less efficient at lower air
pressure! In any case, I think it's more a question of
drag-to-efficiency ratio than efficiency alone, so it gets a bit more
complicated...
> > You could also check the throttle setting in the cruise parameters. I
>
> The 747 YASim config file has the throttle at 0.75.
Cruise parameters? How do they affect my flying if I control
everything by hand?
Andras
===========================================================================
Major Andras
e-mail: [EMAIL PROTECTED]
www: http://andras.webhop.org/
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