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Engine performance, critical altitude


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Since buying the Dimona, she grew to become one of my favourite planes. The only downside I've discovered isn't a real downside, the engine is too strong at altitude.

I had a chat with Joachim about this a while back in another thread and he mainly explained that the aircraft.cfg entry reflects a turbocharged setting (turbocharged = 1) for the reason that the non charged entry resulted in a wrongly performing engine. He is right of course and you can try that by setting that parameter to 0 and watch how the engine performs. You may not like it, hence his decision to leave it like that. Perfectly reasonable!

Now I've stumbled upon this turbocharged 'issue' because I could climb on engine power to well over 13.000ft or something and the MP (Manifold Pressure, whereas the pressure may be misleading, it's more of a suction) didn't decrease at all. So I would have enough engine power to go even higher or just go very fast at 13.000. Looking at the aircraft.cfg entry, the critical altitude is set to 15.000ft, which means that you will achieve some 29.92 (sea level) MP until 15.000 and then slowly lose MP while climbing. Expect some one inch loss per 1000ft altitude gain.

So while the real plane with the Limbach L 2000 EB 1C 80HP engine isn't turbocharged, the sim rendition is (which makes sense with Joachim's statement in mind) but runs full MP up to 15.000ft. I guess the real plane would like that.

While one can manually retard the throttle when climbing, I was looking for a way to achieve this automatically, just like you would with a non turbocharged engine. Well, that's the intention of this thread, to present one way of doing so.

In more detail, you will have to look at the critical_altitude = 15000 setting in the aircraft.cfg and alter it to e.g. 1000ft. What this means is that anything over 1000ft will decrease the achievable MP with altitude gain. So the Dimona's engine will behave like a non turbocharged one while climbing, but will also maintain it's characteristics, as planned by Joachim. Perhaps even 0 or 1ft works, but I was happy with 1000 so far.

Since I only flew some flights with that setting and since I'm not the dev of this fine ship, I'm open to discussions of course. You don't alter much on the plane's FDE and it's well tuned gliding performance and drag values. You also don't raise unnecessary support tickets due to serious user mods. You just adjust the way the engine loses power with altitude, to avoid the mentioned 'overpower' situation.

What do you think? :)

Reverting back is easy of course. Either you make a backup of the file or you just re-establish those 15.000ft.

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