David Culp writes:
> I asked a 747-400 pilot what was the fuel flow per engine at
> cruise. He said about 6000 lb-per-hour. Assuming a TSFC of 0.5
> (I've seen 0.318 and 0.348 for the PW4060, but I don't trust these
> numbers) that would mean each engine is developing 12000 pounds of
> thrust. Therefore the total drag on the airplane at cruise is
> 48000 pounds, and total fuel flow is 24000 pph.
>From looking at the code, I've discovered that YASim assumes a
thrust-specific fuel consumption of 0.8 by default, so there's your
problem. In fact, the following comment appears in Jet.cpp:
// Initialize parameters for an early-ish subsonic turbojet. More
// recent turbofans will typically have a lower vMax, epr0, and
// tsfc.
You can tune these with attributes on the <jet> element in the
YASim config file. For example, in $FG_ROOT/Aircraft-yasim/747.xml,
you can change
<jet x="-10.43" y="16.26" z="-1.20" mass="8000" thrust="63737">
<control-input axis="/controls/throttle[0]" control="THROTTLE"/>
</jet>
to
<jet x="-10.43" y="16.26" z="-1.20" mass="8000" thrust="63737" esfc="0.4">
<control-input axis="/controls/throttle[0]" control="THROTTLE"/>
</jet>
and effectively double the 747's range (repeating for all four
engines). Here are all of the attributes Andy uses for the <jet>
element, together with defaults where I could figure them out:
x
y
z
mass
thrust
afterburner [0]
rotate [0]
n1-idle [55]
n1-max [102]
n2-idle [73]
n2-max [103]
tsfc [0.8]
egt [1050]
epr [3.0]
exhaust-speed [800]
Play with these, and you should get the engine of your dreams.
All the best,
David
--
David Megginson, [EMAIL PROTECTED], http://www.megginson.com/
_______________________________________________
Flightgear-devel mailing list
[EMAIL PROTECTED]
http://mail.flightgear.org/mailman/listinfo/flightgear-devel
