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Mithras

Power Check

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Lovely aircraft, my favourite at the moment, certainly knocking my Realair Duke and Milviz Baron off their top spot.

 

I was conducting a power check last night, though, and noticed that when I pulled the prop levers back, the manifold pressure and the rpm did not budge. Is this right? I should see some sort of drop, shouldn't I?

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My error, I wasn't giving it enough power before pulling back the prop levers.

 

Love this aircraft, it has fantastic STOL performance - I've just gone back to some Idaho dirt strips I tried with the Cessna 185 before Christmas and with care the Aztec can handle some of these, the large flaps mean I can drop onto the runway at just over 55/56 knots. Fantastic - a twin bush plane!

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After staring into the aircraft.cfg file, noticed the min governed speed for the prop is 1900 rpm, so unless you carry out a power check over this, you wont see much. Not too sure this value is correct but cant find any contrary gen yet.

Also not sure the MP is right. Its a turbo engine, yes? My Aztec F 250 POH shows a 34" turbo cruise at 2400 rpm. Not sure this truck will do that unless its very low! Also have a warning note saying not to exceed 39.5" below 18,000ft, 37.0" up to 20,000, 34.0" up to 22,000 and 31.0" up to 24,000ft. Setting the max MP to 39.5 in the cfg file results in some pretty fierce acceleration (and noise!). Feels like it needs some mods...

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The "F" was normally aspirated. Piper also sold a "Turbo Aztec", which was basically a F with Garret turbos. The Alabeo model is clearly not a turbo, in neither performance nor instrumentation.

 

I have the same problem with run-ups though. From memory (a bit unreliable ... it was a while ago) we did them at 1800. I'll see if I can find my old checklists...

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Interesting that the performance is, yes, similar to a normally aspirated aircraft BUT the cfg file clearly shows its turbocharged in the engine and performance text areas! -

 

performance="Maximum Speed\t\n213 kts\t245 mph\t394 kmh\n\nCruise Speed\t\n170 kts\t196 mph\t315 kmh\n\nEngine\t\nTurbo charged TIO-540-C1A\t250hp\n

And the engine shows turbocharged=1 (true) with a critical altitude of 22000.

 

Either way, something doesnt feel 'right' with it.

 

Mithras, for info the POH I have from the web shows run-up carried out at 1500rpm for feathering (max 500rpm drop) and 2200rpm to exercise prop (max 300 rpm drop) and mags. mag drop will be the usual tiny FSX 50rpm drop on both mags.

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Easily you can change the engine TC for the normal aspirated, changing some parameters of the aircraft.cfg, but besides the aircraft.cfg show that this F supposes to be a TC the plane have the SAME feel and behavior and the flight dynamics that the F aspirated. The engine loose MP while gain altitude like a aspirated engine, so alabeo put wrong the description of the plane in the aircraft.cfg maybe.

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That is strange as I have not changed any .cfg settings from initial installation and I see 34" of manifold pressure at takeoff power from sea level all the way up to 22000 feet in a test I did the other day.On the other hand the climb performance was let's say enthusiastic, it held the same rate of climb all the way up which I doubt is realistic at altitude.It does not lose MP with altitude increase so there must be an option to change powerplant versions that was not mentioned.

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If the MP don't drop when you climb that say that the engine it's TC like the aircraft.cfg says!! If loose MP and you need too lean the mixture to recover MP when you climb the engine it's aspirated, I still don't own the aircraft, but still there's a confusion between if the plane is aspirated or is TC.

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I see the handbook (mine is for the 250 C dated 1968) says run ups should be done at 2200 rpm.

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