Hi all,

 

I recently acquired the excellent Realair Lancair Legacy. While I enjoyed it in its 'stock' form, I decided to modify it to enhance the cross country performance.

 

The primary modification I made was to add a turbocharger. I initially added the following variables to the aircraft.cfg file, under the [piston_engine] section.

 

turbocharged=1 // was zero

max_design_mp=30 // was zero

min_design_mp=6 // was zero

critical_altitude=12000 // was zero

 

This gave me the desired performance boost up to max MP for cruising at 12000 feet. After some successful flight testing I decided to see how far I could push things.

 

I bumped critical_altitude up to 22000ft and the aircraft provided satisfactory (and reasonably realistic) performance up to that altitude, although I noticed that at higher speeds I was losing control of the RPM using the blue propeller control. As the speed increased the RPM would gradually creep up until it was redlining. I could pull the propeller lever all the way out and it wouldn't make a difference to the RPM.

 

In this configuration I settled on 24 inches MP and 2400RPM as the tipping point before things got out of control. This equated to a cruise at the top of the green arc of the ASI so it all seemed to work out about right.

 

When I decided to push the turbo critical_altitude up to 30000, this seemed to exacerbate the problem though, and I found that about 22 inches MP was about as much power as I could use while still keeping the RPM under redline. This equated to about 180 knots IAS, well short of the top of the green arc.

 

I'm wondering if the fine folks on this forum might be able to give me a pointer as to which variables I could work with to retain control of the RPM under these circumstances. My aim is to get the aircraft to cruise at 300 knots true at FL280-300. A forum search has left me more confused than when I started!

 

Thanks in advance.

Hi all, any takers on this question? Further experimentation has failed to produce any results. I'd be most grateful if anyone could assist.

 

Thanks again.