C208

[ParaMan 53]

A bit of a strange problem. I'm using the Saitek yoke and throttle, and when I fly the c208 the mixture doesn't seem to work. It's mapped, and when I use the Mooney I have no issues, it seems to be only an issue with the c208.

[eslader 1,784]

The 208 doesn't have a mixture control. It's a turbine. It has a condition lever which has three settings. Cutoff kills fuel to the engine. Low idle gives you a low base RPM for the prop. High idle gives you a higher base RPM for the prop. Low idle should be used when taxiing, and high idle should be used for flight. I haven't flown the 208 since the sim was pretty new, but I seem to vaguely recall it was improperly labeled as a "mixture" lever. Perhaps it still is?

At any rate, the slider I use for mixture does not work for the condition lever either, so there's nothing wrong with your Saitek.

 

Edited October 29, 2021 by eslader

[ParaMan 53]

Awesome, thanks for your help

[Glenn Fitzpatrick 3,798]

Yeah the mouse over that says "mixture" in the C208 is a bug. It is a condition lever.

Mixture is something you have on an engine with pistons.

There are no pistons in a C208 engine - it is one of the ubiquitous Pratt and Whitney PT6A you come across everywhere - a reverse-flow dual shaft free-turbine with a separate 3-stage-axial-flow + 1-stage-centrifugal-flow compressor. See the video.

 

 

Edited October 29, 2021 by Glenn Fitzpatrick

[MarcG 2,996]

3 hours ago, eslader said:

Low idle should be used when taxiing, and high idle should be used for flight.

Oh really?! I've been doing the opposite for months 😄 never noticed any issues though, flies lovely for me🙂

[Glenn Fitzpatrick 3,798]

Good link about how to start a PT6 as well.

http://airplanepilot.blogspot.com/2005/07/starting-pt6.html

Ignore the bit about squirrels I think she made that up.

Edited October 29, 2021 by Glenn Fitzpatrick

[Ixoye 1,822]

2 hours ago, MarcG said:

Oh really?! I've been doing the opposite for months 😄 never noticed any issues though, flies lovely for me🙂

I know, I forgot to set the condition lever to the top position once, and it worked just as well anyway 😄

[eslader 1,784]

5 hours ago, MarcG said:

Oh really?

Yep.

5 hours ago, MarcG said:

I've been doing the opposite for months 😄

Then you've been doing it wrong for months. 😉

 

5 hours ago, MarcG said:

never noticed any issues though, flies lovely for me🙂

Yeah, you probably wouldn't, unless you needed to go around, and then it takes longer for the engine to spool up.  Full disclosure, I have no idea if the sim accurately models this. But if you poke around discussions of real 208 fliers, this is a common debate. Some leave it in low idle all the time because then they aren't moving the lever backwards after landing, which prevents the possibility of moving it too far back and into cutoff. Others point out the issue of spool time when you need faster engine response. The POH calls for high idle in flight.

 

[MarcG 2,996]

I wonder if the 208 mod makes more "realistic" use of this perhaps.

[Dominique_K 10,150]

This is my understanding of how the couple throttle/condition lever works. Quite logical.

At low idle and high idle the turbine rotates respectively at  a minimum of 52 % and 69 % of its maximum  when the throttle is at idle.

You can use HI to start to taxi a « sticky » bird but then better switch back to LI to avoid a runaway.

As your throttle is not at idle during a cruise, it does not really make a difference.

Better have it at HI to minimize the spooling lag during the descent in case of a need to urgently stop  it and climb again or initiate a GA during a botched approach.

 

 

Edited October 29, 2021 by Dominique_K