nagpaw
SOH-CM-2022
Greetings, Gang! I've fallen hard for the LDR Navion. I'm not sure how I missed this little gem in the library, but that's water under the bridge. Now here's two questions for the flight dynamics guys and gals.
For where I mostly fly in the American West, the Navion's normal aspiration is kind of a drag. Here's an airplane that cries out for a turbocharger! So I figured I'd go off the reservation and try my hand at modifying the engine/propeller dynamics by editing the .cfg file. So far everything has worked fine, with one notable problem.
The LDR Navion normally uses a non-turbocharged 300 horsepower IO-550-B. She kind of putters out above 6,500 feet. So I'm trying to simulate fitting a 350 horsepower TSIO-550-B to the airframe. I called up the TCDS for that engine and made the following changes:
1) Increased the aircraft empty weight by about 77 pounds to account for the engine's increased weight
2) Edited the [piston_engine] section with the following text:
max_rated_hp= 350.0
turbocharged= 1
max_design_mp= 38.0
min_design_mp= 1.0
critical_altitude= 12000.0
So far, so good. What a hoss! Now she'll maintain nearly 1,500 feet per minute at 110 KIAS to at least 10,000 feet. The problem is that the propeller becomes basically uncontrollable above about 29.5" manifold pressure, the original IO-550's red line. I pull the MP to about 25" and set the prop to 2300 RPM. As I advance the power the prop maintains 2300 RPM until I surpass 29.5" MP. If I push the MP higher, the prop begins to slowly increase RPM in direct relation to the throttle like a fixed pitch prop.
So, any ideas where the problem lies? If it's something buried in the .air file, I'll just forget the whole thing! Although I suppose the other option is to just strap a turbocharger to the original IO-550 and not try to fiddle with the horsepower. I'm not searching for hyper-realism. Just a little better performance through the Rockies! Thoughts?
Thanks for the help, guys!
For where I mostly fly in the American West, the Navion's normal aspiration is kind of a drag. Here's an airplane that cries out for a turbocharger! So I figured I'd go off the reservation and try my hand at modifying the engine/propeller dynamics by editing the .cfg file. So far everything has worked fine, with one notable problem.
The LDR Navion normally uses a non-turbocharged 300 horsepower IO-550-B. She kind of putters out above 6,500 feet. So I'm trying to simulate fitting a 350 horsepower TSIO-550-B to the airframe. I called up the TCDS for that engine and made the following changes:
1) Increased the aircraft empty weight by about 77 pounds to account for the engine's increased weight
2) Edited the [piston_engine] section with the following text:
max_rated_hp= 350.0
turbocharged= 1
max_design_mp= 38.0
min_design_mp= 1.0
critical_altitude= 12000.0
So far, so good. What a hoss! Now she'll maintain nearly 1,500 feet per minute at 110 KIAS to at least 10,000 feet. The problem is that the propeller becomes basically uncontrollable above about 29.5" manifold pressure, the original IO-550's red line. I pull the MP to about 25" and set the prop to 2300 RPM. As I advance the power the prop maintains 2300 RPM until I surpass 29.5" MP. If I push the MP higher, the prop begins to slowly increase RPM in direct relation to the throttle like a fixed pitch prop.
So, any ideas where the problem lies? If it's something buried in the .air file, I'll just forget the whole thing! Although I suppose the other option is to just strap a turbocharger to the original IO-550 and not try to fiddle with the horsepower. I'm not searching for hyper-realism. Just a little better performance through the Rockies! Thoughts?
Thanks for the help, guys!
