Combustion engine idle speed

[Ray207]

I often start a new combustion aircraft and the engine doesn't come alive. Throttle up and nothing happens. The only cure seems to be to apply nearly all throttle trim (which start the plane going down the runway ), or re-calculate the sticks every time the engine stops.

Maybe we could wish for an idle speed control for combustion engines in the next version??? Anyone else experience the same ??

Thanks

[Looee]

Hi Ray,

If we could get one of the Moellers to explain the function of the engine friction constants in the .PAR file I think some progress could be made. The engine PAR adjustments include lots of interaction between the four data lines below the, "COMBUSTION----------- // Type (-/COMBUSTION/ELECTRO)" data line.

There's the cylinder displacement, always in cubic centimeters, fuel consumption at full throttle, and the two engine friction constants, which are totally Greek to my understanding.

Another thing to consider is the size of the propeller. I've noticed that some folks will put a larger than normal prop for the engine size, and since this a simulation, the engine will spin it despite it being too large for reality. Try decreasing the prop size and increasing the engine fuel consumption at full throttle. Do it in small amounts and make a backup of the original if the prgram freezes or blue screens.

[Lindsay]

I had cause to re-calibrate and my planes would then 'conk out' at idle. I fixed it by putting throttle trim up and re-calibrating till it got it right. It is fine now.

[TreeHugger]

Hi,

here is a simple workaround: Go to menu "Simulation", under "Options" you'll find an entry "Simulate empty tank". Remove the hook and the engine never stops. Not beautiful, but effective.

Regards,
Frank

[Ray207]

Well, Frank's right... SADLY because I like feature of running out of fuel when you lease expect it or forget to watch your time. I think that engine friction might have something to do with it, but I would almost bet that it is a minor programming glitch. Why else would unchecking the simulate empty tank function remove the challenge.
HEY ANYWAY GREAT RESPONSE FROM YOU GUYS -- THANKS MUCH

[Lindsay]

On the subject of empty tank options, what happens when the tank gets to empty? I ask because I have had the option ticked and now and then a plane will just stop in mid-air and re-initialise itself. Is this the empty tank syndrome? Or what?

[TreeHugger]

Hi,

with "tank empty" the engine should quit and force you to perform a deadstick landing - just tried it, works OK. The decisive factors for flight time seem to be "fuel consumption at full throttle" and "tank size".

Re-initializing in mid-air is a bit peculiar...

Regards,
Frank

[Lindsay]

That makes a lot of sense, Frank.

Yes, the mid-air stopping is very strange behaviour. It doesn't happen very often and I can see nothing to trigger it. Guess it will have to remain one of life's little mysteries!

Lindsay.

[Looee]

I've had the chance to twiddle the friction constants in a turbine jet I modeled. You can, in theory reduce the second motor friction constant down to about 0.28 and get less internal engine friction.

My problem with the jet was increasing the rotation moment of inertia to simulate the rather long spool-up and spool downs of a true turbine engine, and of course the rather small outlet size of the engine was modeled too. I had to make 2 PAR entries for the engine with LEFT entered in the second one to counter the extreme gyroscopic forces of the first RIGHT rotating engine. The problem with reducing the friction is that the engines, once spooled up, are reluctant to spool back down again. I ended up having to come in hot from the north of the larger valley in the Switzerland .scn and hold a high alpha flare nearly the entire length of the scene just to land. So I've modeled BIG spoilers on this model.

Remember we're just spinning electrons here, the constants for FMS PAR file have a huge amount of flexibility and you can get over 22Kgs. of thrust out of a theoretical 100 cc engine with a 5" diameter, 6 bladed propeller disc that has over 40 grams per second of fuel fed into it. There you go, virtual internal combustion jet turbine, just add proper .WAV file and go shred some atmosphere.

Lewis