Spit 1a

[IvanK]

I have spent hours in the National Archives chasing original source performance stuff. With respect to DH 2 Pitch prop there was little to find, though I am yet to exhaust the contents of the archives . The only solid data I have found (so far) with regards DH 2 Pitch performance was some trial data of tests on a Spit IA with a "conformal" tank on the port wing. So obviously inferior performance to a clean IA. Even the Motherload document Avia 18/682 doesn't have much in this regard.

Here is the data for what its worth:







The interesting thing is Max Speed is being achieved at 2700 -2900RPM which implies Full Fine to me. its also 87Octane at 61/4Lbs Boost
At FTH 17,900ft its still getting 352MPH TAS at 3000RPM and 6.2Lbs Boost

[ATAG_Dutch]

Originally Posted by Plt Off JRB Meaker

Well done Dutch,got there before me,top job

Thanks Meaks!

It doesn't explain the performance at sea level though.

If the 2-bladed fixed pitch prop achieved 295 @ 2000ft, 250 for the 2-pitch prop at sea level seems a bit dismal.

Can anyone find any figs/graphs? Most google references point to either 1C or Ultrapack!!

[Blackdog_kt]

Almost everything except the Spit Mk.II is slower than it should and that's what Luthier probably referred to when talking about FM fixes (i think he was replying to a thread about this very issue).

With that out of the way and without going into the octane/boost levels debate at all, the root cause of the problem is the fact that most people are not really familiar with how prop pitch works and are getting confused with the two-speed prop.

The trick is simple but a little time consuming, however it should be no big deal for any dedicated Spit drivers until we get a Rotol (constant speed) variant:
start a free flight mission and just fly for half an hour with the sole aim of seeing how much you can get away with without frying the engine.

I'm almost not flying the Spit at all but i have no problem getting 250mph IAS at medium altitudes (which would translate to about 300 mph) with very conservative cruise power settings: no over-boost, just maximum continuous power (the white triangle marker in the instruments red zone), coarse pitch and being careful to trim well and minimize radiator use.

The problem many people have is that they don't know much about how the propellers really work and what that means for ease of maintaining performance. It's no biggie, i didn't know either, there are a load of articles on the web and after some reading my handling with all aircraft improved considerably.

I've seen three excellent articles posted here some time ago, some of it might be too technical (actually the mixture article is mostly about modern civilian prop-aircraft from a point onwards) but it's a worthy read. Just take your time when reading it and don't rush through it, you'll see a lot of mysteries getting explained

Here are the links
manifold pressure: http://www.avweb.com/news/pelican/182081-1.html
propellers: http://www.avweb.com/news/pelican/182082-1.html
mixture: http://www.avweb.com/news/pelican/182084-1.html

[Al Schlageter]

How did these screwed up FMs get by initial testing?

[Blackdog_kt]

I think it's more due to the new engine modeling. The FMs feel fine in terms of handling, i can't quite put my finger on it but it feels like an improved IL2 experience, it just feels more fluid and less on rails.

The performance issues seem to be tied to power output from the engines (top speeds/ceilings/climb rates) so i guess the new CEM is where the tweaking needs to happen. The fact that the AI has to use simplified routines without cheating makes it all the more complicated (it costs about 10 FPS per aircraft to enable the new CEM, so it's only used for the player aircraft and the AI ones use simpler models), not to mention that most players are not up to it yet (lot's of variation between what each pilot can achieve).

That being said, i'd rather have this new feature with a couple of inaccuracies to be corrected as time goes by, rather than go back to IL2 style engine modeling.

[ATAG_Dutch]

Originally Posted by Dutch_851

Interestingly, she really wanted to climb so lots of down trim was needed. Might test the altitude again to see if anything has changed.

I thought the altitude capability may have improved, but tried this out this afternoon.

Started with the same 500kph@6000m in FMB, and kept the climb rate at 1000ft per min or below.

It took a long time, but got to 25,500ft. There may have been more to come, but progress was very slow by this point.

Here's a screenshot of the instruments for those who're interested in such matters.