View Full Version : RPM not adjustable following power scaler increase

October 19th, 2008, 20:57
<SPAN lang=EN>Iím trying to tweek the cfg file in fs9 for a commercial Cessna skymaster to more closely reflect the performance of the Riley Super Skyrocket conversion. Iím tweeking the file for my own use.

I needed to change the performance of the a/c to match real world values, which have much higher rates of climb and cruise speed and take off performance. I have adjusted several of the piston engine and flight values in the cfg and have flight tested the a/c through several adjustments and have achieved the proper performance.

//power_scalar=1.0 //Piston power scalar
power_scalar=1.5 //Piston power scalar
//cylinder_displacement=60.0 //Cubic inches per cylinder
cylinder_displacement=80.0 //Cubic inches per cylinder
compression_ratio=7.5 //Compression ratio
number_of_cylinders=6 //Number of cylinders
//max_rated_rpm=2800.0 //Max rated RPM
max_rated_rpm=2500.0 //Max rated RPM
//max_rated_hp=210.0 //Max rated HP
max_rated_hp=310.0 //Max rated HP
fuel_metering_type=0 //0=Fuel Injected, 1=Gravity Carbureter, //2=Aerobatic Carbureter

AS I see it, the only problem is that the prop control is not working as usual. At a high cruise MP setting of 32, the RPM registered 3074 where set previously. When I adjust the prop there is no gradual change, the prop lever simply is pulled back with no change in the RPM, until finally the prop is feathered and I have to immediately increase the prop pitch to keep flying.

Any ideas.


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October 20th, 2008, 10:50
Turbocharged IO 360? delivering 300 HP? On a light twin?

If you don't have it, get the AFSD utility from Herve Sors, or the test panel from Jerry Beckwith's mudpond site. You will be able to measure HP, thrust, MP, prop pitch values, RPM and a host of parameters. Sounds as if the prop pitch governing and RPM limits are off.

Feed us some more info and we will see what we can do to help.


October 20th, 2008, 14:03
The simulated power output is determined by a combination of air file parameters and the engine parameters in the aircraft.cfg file, so it's difficult to know exactly what the power output is after this set of changes. Of the things you changed, only power_scalar, cylinder_displacement, and max_rated_rpm will affect power output.

The other half of the equation is the propeller. The ability of the prop to absorb power and convert it to thrust are also simulated through tables in the air file. Just as in the real world, the prop may need to be changed to handle the change in RPM and power.

October 22nd, 2008, 14:29
You might want to have a peek at Spark's Airwrench. It will adjust the engine and prop parameters to meet the specifications you desire through and ability to fine tune in the air. file according to the measured performance parameters such as observed through Jerry's test panel or AFSD.

The engine parameters can be adjusted manually through the relevent airfile tables, using hex, and aired, or airfile manager (in base ten). Still much testing is required to achieve accurate results.

Cheers: T.