When the English got the 11 39s in Sept. 41, they were really disappointed. They found that the top speed was about 30mph lower than what they were lead to believe. Now, was it by reading specs or word of mouth I don't know but the bottom line was notsogood as far as expectations were concerned.
FWIW,
Good Hunting!

I think that the above posts on some planes being under a small percent and some over a small percent is where we run into alot of fm debates. Cube summed up some very valid points in his tests in this area.

The other thing I think needs mentioning is that the percentage is relative. That is 2% on the low side is not equal to 2% on the high side. 2% under 300 would be 6 whereas 2% under 700 would be 14. So if one plane is performing 14 less and one is performing 5-10 more we would start to see glaring advantages.

So if one is lower then all should be lower. Some parity is what is needed.


I would be very interested to see what the numbers turn out in the final release. I'm sick of flying just the G-2

Yep - compiling data must be a nightmare.
Do you choose :

(A) Factory specs or "Best Data" from performance honed prototypes/test aircraft knowing damn well they didn't perform like that in real life

(B) Test reports from captured aircraft with possible damage, derated engine, wrong (or not optimum) fuels and maybe a pilot who can't quite get the best out of an unfamiliar type

Or something in between ?

Great post JG5. I've read both & in most cases one would think they're 2 different planes.
FWIW,
Good Hunting!

Hmmm...

I'd say 3% to 5% could easily be defined as "human error".

Personally I've never understood the slide-rule mentality that seems to command the FM zealots...



http://www.SIMTweak.com

I've always thought the distilation of all the FM data to what's in the sim as two parts science and eight parts art.

First, the flight tests were done by pilots. Humans. Darned good ones at what they did, but still humans nonetheless. They did tests using their hands and feet on the controls, visually read instruments and stop watches.

Deviation is inherent automatically. Indeed, one wonders if test results could be changed by the pilot conducting the test. For example, what if I get Chuck Yeager to do the tests on a captured 109 and then later that day have Eric Hartman do the same tests in the same bird. Will they match exactly? How great will the deviation be?

Even if they follow the same procedures based on a rigid protocol, my money will say that their answers will be different.

There were no computer simulations of aircraft design, no printouts of pilot input to performance, and radar wasn't sophisticated enough for tracking single aircraft with the resolution we take for granted now. Look at the plots in the reports - they're hand drawn. Hint, hint. Lots of trial and error involved.

I'm not saying they didn't know what they were doing, just that they probably understood that the word definative didn't mean absolute.


What I would do as a sim designer is pick a middle of the road flight test and use it as a target for the FM. If what spits out at the end of the code is within the top and the bottom tests by halfway, it would be pretty much on the mark to me.

Ten thousand emails later I'd probably refine it a bit. But only the ones that showed my FM mark wasn't the middle one, but rather skewed up or down from there.

I'd also make my little slogan at the bottom of every one of my posts "Simulation is a fancy way of saying approximation."

Second, combat (even simulated) doesn't happen in a flight test. It's rare that someone enters into a clean sustained turn or a steady climb. These things are done at takeoff and in moving to the engagement area.

No, we zoom climb, corkscrew, hammerhead, slam from half to full throttle and back, roll with opposite rudder, dive in the vertical, and do all manner of inherently unsafe actions without a thought - unsafe without the aid of the enemy.

Yea, though I fly through the valley of virtual death, I have no fear, for I can restart.

Pilot accounts are somewhat misleading on this score, as only the unusual is recorded and made special note of.

Chuck Yeager's autobiography of how he became Ace in a Day and Bud Anderson's account of taking on a 109 are a great example of this.

Ol' Chuck writes that he just got up behind those boys and shot them down from close range. No detail of how his plane stacked up against the other guy's in performance or the edge given to him technologically. The reason for this is clear - it wasn't a factor in his victories.

Part of this, of course, is General Yeager's belief that in WWII there were no inferior aircraft flying either side, only unique challenges to a pilot's skill.

The greatest challenge being slightly better than the other guy. Spotting him first helped, so says he.

Bud Anderson's fight against the Fritz where they zoom climb against each other and he wins that score twice is the opposite. Here the FM mattered - and was so unusual that he vividly recalls it second by second.

actuallyn I've seen guys posting speeds for a plane X that I could beat easily, and by more than 5% margin, and others that I couldn't match by a bigger margin than that.

If you get 15kph difference around 700kph, it looks like a non significant error to me...

someone on ubi claimed the P51 was castrated because it couldn't go over 650kph max level speed... plane or pilot problem?

Must be within .0000000000000000000000000000001 of published flight data.

agreed...


er, just a second.. published by whom? US? germans? british? russians? constructors?

That's easy. For German planes, we use the official guide to German FM's written by Josef Goebbels and for the Russian planes we use the patriotic literature on FM's written by the great Stalin himself.