Hello Plurb,
yes alter the T1505 table in .air.
See for details
http://www.avhistory.org/scripts/MegaBBS/thread-view.asp?threadid=2743&MessageID...or for a quickey:
Originally written by fturner on 25/7/2004 3:02 PM
I've been doing some more "experiments" on 1505 and it just clicked in....... There is a time constant factor in here that was pointed out along time ago.
True, slope of TBL 1505 affects the current 'spool up rate'. However, it has definetly been shown to control the "Corrected Fuel Flow" parameter available to gauges.
Recent Aired.ini files give the 'Theta - Delta' factor to convert CFF to 'uncorrected fuel flow' (pph). That factor is typically 0.5 at cruise. 1.0 at SL ISA. Meaning the cruise CFF of 6600 pph comes to 3300 pph after being un-corrected to real flow.
By adjusting TBL 1505 I've been able to get a changing TSFC that is lower (better) for TO and low altitudes/speeds than at cruise. In fact, my XML Jet Test gauge displays this new SFC, and Specific Range based on it.
However, the 'uncorrected pph' doesn't drain the tanks, so it's mainly for testing and experimentation at this time.
fuel_flow_scalar DOES NOT change this new pph. However, moving the 'x' value in TBL 1505 does (based on current CN2).
FS updates everything at 18 ticks per second (unless of course your computer is overloaded). This goes for almost ALL calculations in FS so therefore almost everything in the airfile that requires a time constant is based on 18 ticks per second.
While C Token Variables and XML Parameters are updated 18.25 times per second, there is no reason to believe the internal flight model is. Note FPS can easily exceed 20, and a flight model generally runs at several times the visual frame rate.
However, I don't know what rate the FM code iterates at. Some calculations could be limited to 'one per tick'. Possibly gauge related parameters.
....
here comes the cruncher. The fuel_flow_gain in the aircraft.cfg file is the value used to adjust the slope based on your throttle setting and how far away CN2 is from that throttle setting, hence the faster spool up when the throttle is slammed wide open, and the slower spool up encountered with a gradual increase in throttle. At this moment until I test further, I am not sure if the slope indicates the fastest change possible with 100% throttle (I'm leaning this way as I get more accurate spool times to what I specify when building the slope), or the fastest change possible with the throttle at 0% (seems to take longer than I specify when building the slope within that CN2 range)
I figured the fuel_flow_gain represents the 'gain' of the fuel flow controller in a turbine. Higher values set a 'tighter' N2 control loop, so response is faster. Though, the slope of TBL 1505 is also involved.
Ian
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