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Gregg_Seipp

Low cruise speed on J41

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Hi all,

 

I've had the J41 for about two weeks. All in all it's going pretty good but I do have a question:

 

Sometimes I get the normal 240KIAS and can run 70% power.

Sometimes, however, all I can get a cruising speed of about 190 KIAS with EGT sitting right at MAX. Engine icing is off and haven't been any icing conditions. I'm having to set power to 57% because of the EGT. Nose is about 3% up from the horizon. What could be causing the difference?

 

Same airport, pretty much the same conditions. Flaps and gear are up. I have all failures turned off. As an aside, once I began decent, I cycled the engine icing on and then back off and my normal power came back and I was able to run more than 74% on the power without approaching MAX EGT and 225 KIAS. (I was approaching the point where I had to throttle back to 190 KIAS so I just left it there...I could have gotten faster if I wanted.)

 

Any ideas?

 

Thanks,

Gregg

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This issue happens with me every once a while as well. It seems like the engine's are cooked and not producing power. I think it has something to do with the engine anti-ice as you mentioned. Maybe the engine model gets a little confused with people cycling the anti-ice quick.

 

For me, sometimes playing with the Eng Anti-Ice helps. Other times, I have to reload the aircraft.

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Yeah,

 

My first thought was to cut back power and cycle the Engine Anti-icing at altitude but I was already down to 54% and 190 KIAS so I just decided to ride it out until descent.

 

I also considered that the model *thought* I had ice in the engine.

 

Then I thought that maybe I was on the 'back of the envelop'...flying nose up using thrust for lift. Can't exclude that idea either and it would have also reduced air flow through the engine which would have added to the heat. Anyway, since I did decend (using the opportunity of the lower EGT to cycle the anti-ice) it would have gotten me out of that situation as well.

 

The aircraft, I thought, was behaving a little odd after takeoff. I engaged the autopilot after departure at 190 for a slow climb...full power, 98% RPM, I armed IAS and ALTSEL for 3000 but it insisted on holding altitude and started descending. I tried twice but ended up giving up and flying it by hand until I was ready to turn on LNAV. After that, I remember being uneasy about the climb. It just didn't seem strong...climbing slow even at 180 KIAS. I thought that maybe it would accelerate at altitude...but I doubted it...and it didn't. Still haven't figured out the right way to handle the autopilot on these short situations. Maybe that's a clue and maybe that's where I got outside the basic model. I turn on HDG so the aircraft can manage the turn but if I manually nose up at all (ALT and ALTSEL are NOT selected) it just disengages completely. Maybe I'm misunderstanding there.

 

I'll admit that this is the first time I've had a chance to actually think it through with my limited experience. Incredibly fun and challenging aircraft to fly...I'd just like to get a solution without having to restart. I can't imagine (in my imagination situation), explaining to the passengers how we just transported from 16,000 ft. back to the ramp. LOL.

 

 

Sorry for the long post.

 

Gregg

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Hi Gregg,

 

Where you flying on line using FSInn Wx? If so, that could have been your problem. That Wx engine keeps altitude temperatures way warmer than actual.

 

Too bad we do not have performance charts that would give you what IAS/fuel burn/TAS to expect at different altitudes, weights and temperatures.

 

At 21,000, -19c, 18,000lbs, 60% torq, and 10c below max I am getting 220 IAS and 308 TAS

 

Regards

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Hmmm...interesting. I'll redo the flight and gather some stats. I don't us FSInn (absolutely hate that app) but I may have been using static wx since I'm trying to have a stable environment while I'm learning the aircraft so I may be able to replicate it. I'll let you know.

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