Author Topic: It's official... (Read 8767 times)

Widewing · « **Reply #60 on:** December 17, 2005, 12:04:38 PM »

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Originally posted by Kurfürst
From what I have seen the P-51D Cd0 was around 0.0170, the P-38J's - 0.0270 Add the fact that the P-38 had much higher wing area with what you have to multiply the Cd0, and there's absolutely NO WAY the P-38 could be claimed a 'drag racer', esp. compared to the Mustang. Powerloading, dunno, the P-38 has about twice the weight, and twice as many similiarly powerful engines, so it could cancel it out.

Francis Dean provides calculated data in America's Hundred Thousand that shows the P-38L with about an 8% advantage in acceleration rate over the P-51D. He used the following data for his calculation.

P-38L 3,200 hp 16,880 lb weight 3,840 lb thrust 1,676 lb drag

P-51D 1,720 hp 10,208 lb weight 2,064 lb thrust 845 lb drag

His calculation resulted in an acceleration rate of 4.13 ft/sec/sec for the P-38L, and 3.85 ft/sec/sec for the P-51D (difference equal to 7%). If the P-38J/L accelerated 7% faster than the P-51D in the game, it would turn in a time of 32.84 seconds in my acceleration test, instead of 36.53 seconds.

By the way, I also tested the 109G-14 to determine best speed and best altitude. I measured 401 mph @ 21,000 feet, with 1.42 ata. Still too slow, but a bit better than some have stated.

My regards,

Widewing

Nashwan · « **Reply #61 on:** December 17, 2005, 12:08:01 PM »

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This is exactly why things are out of whack in AH world. Whose modification can make it into the game as substitute for standard.

It's not a "modification". Spitfires were usually fitted with mirrors. Certainly all the VIII/IX tests I know of had mirrors fitted.

AH does not model mirrors. Should they model the drag of something that isn't fitted?

Crumpp · « **Reply #62 on:** December 17, 2005, 12:08:04 PM »

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Francis Dean provides calculated data in America's Hundred Thousand that shows the P-38L with about an 8% advantage in acceleration rate over the P-51D. He used the following data for his calculation.

Have you checked out the TAIC tested results, Widewing?

All the best,

Crumpp

Crumpp · « **Reply #63 on:** December 17, 2005, 12:09:50 PM »

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Should they model the drag of something that isn't fitted?

They don't model the effect's of subzero winter temperatures either.

Should all the Luftwaffe planes have to carry around over 100 lbs of winterization gear all the time??

Facts are it came on the aircraft and should be modeled.

All the best,

Crumpp

Kev367th · « **Reply #64 on:** December 17, 2005, 12:38:54 PM »

RE: BS539
Two gun ports covered with hemispherical blanks - Should be, was standard fit, this was where the 50cals 'would' be.

All remaining gun ports sealed off - Assuming they mean the 4x.303 ports, yet again whats so unusual. Spits on takeoff had the infamous red patches covering the .303 gun ports to prevent icing prior to initial firing.

It also states mirror was fitted.

So we still have Spit LF IX with normal span wings and a sea level speed of 336mph with a Merlin66.

As per the other report, clipping the wings had the effect of increasing roll, increasing low alt speed, but at the detriment of turn radius.

So I don't see where the extra 7mph is a problem, clipped wings difference?

Widewing · « **Reply #65 on:** December 17, 2005, 12:53:28 PM »

Quote

Originally posted by Crumpp
Have you checked out the TAIC tested results, Widewing?

All the best,

Crumpp

I don't recall if I've seen it or not. I have seen the report from the P-51B, P-38J-10, P-47D-10 and P-39Q-5 comparison test done at Eglin. The P-38J was clearly better in climb and acceleration to the other three. I may have a photocopy from Bodie in my files... I'll have to look.

My regards,

WIdewing

Squire · « **Reply #66 on:** December 17, 2005, 01:06:45 PM »

Alfred Prices book indicated a "slight speed increase" from the clipped wings, I beleive it was 5 mph, but I don't have it in front of me.

As if it makes any real difference, but that wont prevent a 400 post thread on it I guess.

Fix the Spit PYRO, it doesn't bleed E!

There ya go. Happy to be of service.

KurfÃ¼rst · « **Reply #67 on:** December 17, 2005, 01:24:06 PM »

Crumpp is correct about BS 543, it was some early prototype for the IXLF from 1942, and differed considerably from the production plane in engine and propellor. It had an experimental screw, type XH54D-RM-S5, which did not see service.

It's engine was also in the early development stage, and was rated higher than the production Merlin 66 was. It's readily appearant if you look on the climb curves that 543's early development Merlin 66 had a rated altitude for climb of 18000 feet, and 22 000 feet for speed run.
That's 2000 feet higher rated alt for the engine that what was standard for the production Merlin 66, ei. 16/20 000 feet.

Compare :

Prototype : http://www.spitfireperformance.com/bs543climb.gif
Note 18 ft rated altitude.

Datasheet : http://www.spitfireperformance.com/spitlf9ads.jpg
Note the production Merlin 66 has 16 000 feet rated altitude.

Prototype speed : http://www.spitfireperformance.com/lfhfspeed.gif
Note it's 22 000 feet rated alt.

Production Engine rammed power :http://www.spitfireperformance.com/merlin66hpchart.jpg
Note it's 20 000 feet.

Obviously, an engien with a higher rated altitude will produce greater speed because of the thinner atmoshpere. That explains why BS 543 obtained slightly higher speed than the officially accepted speed as per the IXLF datasheet (404mph) : they were different type of aircraft and it's not valid to compare results to it.

Crumpp · « **Reply #68 on:** December 17, 2005, 01:37:06 PM »

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So we still have Spit LF IX with normal span wings and a sea level speed of 336mph with a Merlin66.

It is however clearly on the upper scale of performance and is no different from "normal" FW-190A6's doing 580kph on the deck. All are within manufacturer's tolerances.

None represent the middle of the road performance however.

I am not even advocating that modeled performance needs to be "average". I do advocate that performance can adjusted within tolerances to best reflect an aircraft's historical balance within the planeset.

Would it be correct if I posted flight tested data from 5 different aircraft in which three of them were above Focke Wulf's listed specifications and started claiming the FW-190 should be faster than those specifications always? They are simply possible performance within a normal range.

I mean come on. As much as some folks would love for it to be, the Spitfire was not running all over the skies during WWII outrunning, outdiving, outclimbing, or outturning all planes at all times. Like every other design it was about the engineering trade offs. Just as there are "Lemons" there are exceptional examples of any manufacturered product.

We can take selected data though and make charts all day long showing our favourite plane as the "uberfighter" proving it's prowness to ourselves.

All the best,

Crumpp

Nashwan · « **Reply #69 on:** December 17, 2005, 01:38:29 PM »

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Facts are it came on the aircraft and should be modeled.

Oh, I agree, but I believe the graphics hit is the reason they didn't model it. I don't think they'd model the drag for someting that isn't fitted.

Kev367th · « **Reply #70 on:** December 17, 2005, 01:50:27 PM »

Quote

Originally posted by Crumpp
It is however clearly on the upper scale of performance and is no different from "normal" FW-190A6's doing 580kph on the deck. All are within manufacturer's tolerances.

None represent the middle of the road performance however.

I am not even advocating that modeled performance needs to be "average". I do advocate that performance can adjusted within tolerances to best reflect an aircraft's historical balance within the planeset.

Would it be correct if I posted flight tested data from 5 different aircraft in which three of them were above Focke Wulf's listed specifications and started claiming the FW-190 should be faster than those specifications always? They are simply possible performance within a normal range.

I mean come on. As much as some folks would love for it to be, the Spitfire was not running all over the skies during WWII outrunning, outdiving, outclimbing, or outturning all planes at all times. Like every other design it was about the engineering trade offs. Just as there are "Lemons" there are exceptional examples of any manufacturered product.

We can take selected data though and make charts all day long showing our favourite plane as the "uberfighter" proving it's prowness to ourselves.

All the best,

Crumpp

Exactly, and HT doesn't model lemons.
If he did he would include the poor build quality of late war LW rides, and such things as aircraft being delivered minus some instruments.

I believe I have already stated I don't believe the XVI is the uber fighter some seem to think it is.
However for the MA environment, it and the VIII are the two best Spits out there.
Why the XVI more popular - a) Clipped wings, b) 50 cals

If anything I think the VIII is slighly under performance specs, seems more like the data came from a extended wing Spit VIII, not a normal span one.

Crumpp · « **Reply #71 on:** December 17, 2005, 02:04:14 PM »

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Exactly, and HT doesn't model lemons.

That is a pretty good deflection, Kev.

Your correct HTC is not modeling Lemons in the case of Spitfire Mk XVI. They have been duped into modeling cherry picked upper end performance.

What do you think the performance should be?

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If he did he would include the poor build quality of late war LW rides, and such things as aircraft being delivered minus some instruments.

Yep it happens. However all in all the Luftwaffe actually kept things together pretty well. Some things fell through the cracks as can be expected under those circumstances. To characterize "poor quality" builds or incidents of gross negligence on the part of the inspectors as hardly typical is not correct. Unless we are talking the last week or so of the war.

The discussion is on the Spitfire Mk XVI especially sense I would hardly characterize the Luftwaffe data HTC uses as "cherry picked". We have an FW-190A5 modeled on a captured FW-190G they attempted to cobble together as a fighter. Our FW-190A8 data does not appear to have any positional error corrections applied.

All the best,

Crumpp

Crumpp · « **Reply #72 on:** December 17, 2005, 02:28:30 PM »

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If anything I think the VIII is slighly under performance specs, seems more like the data came from a extended wing Spit VIII, not a normal span one.

It should be fixed then.

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Oh, I agree, but I believe the graphics hit is the reason they didn't model it. I don't think they'd model the drag for someting that isn't fitted.

Kind of a freebie for the Spitfire. Seems like a signicant gain for mirror though. I don't think the ETC 504 rack caused that large a performance change.

All the best,

Crumpp

Squire · « **Reply #73 on:** December 17, 2005, 03:06:35 PM »

Tested the VIII. 401 mph TAS at 22,000 ft. on the dot. Clean, achieved in level acceleration at max boost.

Thats within 6 mph of the AFDU tests, and you guys all know enough about a/c test regimes that when you start quibbling over an error of 1 percent, that thats close enough.

Seems fine to me.

The XVI is 3 mph faster at 19,900 ft.

Could be any # of things to account for that. Clipped wings, or anything else.

Seems fine to me.

PYRO is not about to revisit a FM over microscopic #s quibbles. Nor should he.

As for the roll rate of the VIII, I have seen no hard data on that to indicate there is even a problem, it would require some very precise tests, and FM data from the AFDU to back up the claim of the error. I find it unlikely thats going to happen.

...but who knows.

straffo · « **Reply #74 on:** December 17, 2005, 03:29:31 PM »

As I fly mostly 190 I'll be pretty pissed to see my favorite target perked.

If you have trouble with the spit ... LEARN don't ask for it be perked.