Credibility

[DweebFire]

I've done some research on the Spitfire's weights recently, and reading up on SgtPappy's posts, I've come to the conclusion that the weights posted at Spitfire Performance may have some errors. If this really is the case, how credible is the rest of the site?

Don't get me wrong it's a great, well-putogether site, but some data seems misleading.

[Widewing]

Originally posted by DweebFire
I've done some research on the Spitfire's weights recently, and reading up on SgtPappy's posts, I've come to the conclusion that the weights posted at Spitfire Performance may have some errors. If this really is the case, how credible is the rest of the site?

Don't get me wrong it's a great, well-putogether site, but some data seems misleading.

What do you have access to that is more reliable than the data and tests presented on that website? I mean, that data is what Historians classify as Primary Source Documents.

Please tell me you're not using a commercial trade book for comparison.

My regards,

Widewing

[Guppy35]

Will...not...make....smart... .aleck.....remark......will not....!  

Oh but it's so tempting.....

And yeah I'm with Widewing on this one.

[Ack-Ack]

Originally posted by Guppy35
Will...not...make....smart....aleck.....remark......will not....!  

Give yourself to the Dark Side...


Darth Ack-Ack

[Squire]

Kind of hard to reply when you don't really say anything specific. I certainly wont be naive enough to think there is no possibility of a few errors on any document (to err is human after all), but you have to at least make a case first.

[C(Sea)Bass]

Originally posted by Ack-Ack
Give yourself to the Dark Side...


Darth Ack-Ack

Come to the Dark Side...... We have cookies:D

[DweebFire]

Sorry I left it out all.

No, no, I'm not saying its a horrible site, I should rename the thread. Hah. I feel bad now. There's no other site that has been more credible to me actually.

Anywho, we got one small example. Likely would not counter the credibility of the rest of the site, but there's often experimental error in many tests.

One of the tests I found was the Corsair tests I've seen stated before in these forums. For one thing, there are the F4U tests sheets stated on the bottom of F4U Performance Summary has some weird results. The British 100 octane was the same as 100/125 US grade right? The tests have some weird figures., rarely going over 400 mph on the FAA tests.

Other random figures includes the Spitfire weights. Like Pappy once stated, the weights are iffy. He just wants me to restate it while I'm here since we're using the same comp.

Spitfire VIII: full ammo, full fuel (123 Imp. Gal): 7807 lbs. / 25% fuel, full ammo: 7137 lbs. / no fuel, no ammo: 6678 lbs

Spitfire IX: full ammo, full fuel (85 Imp. gal): 7303 lbs. (7445 lbs. on the site) / 25% fuel, full ammo: 6843 lbs. (6986 lbs from calculations based on site) / no ammo, no fuel: 6455 lbs. (6590 lbs. from calcs)

The tare weights for both planes are 5931 lbs. (VIII) and 5749 lbs. (IX). The VIII has everything the IX has but more.. i.e. more hydraulic fluid, more fuel, etc. Nothing that I know of is subtracted. Their tare weights differ in 182 lbs. When you get their weights based on the website and subtract fuel and ammo weights (based on the site as well) you find that their weights only differ in 88 lbs.

So I'm assuming that there's a problem with something.. and I'm finding a problem with what I should trust on the site and what I shouldn't. A weight diff. in 88 lbs. vs the in-game 223 lbs is a little weird. maneuverability change is a big difference with such weights.

[Widewing]

Originally posted by DweebFire

One of the tests I found was the Corsair tests I've seen stated before in these forums. For one thing, there are the F4U tests sheets stated on the bottom of F4U Performance Summary has some weird results. The British 100 octane was the same as 100/125 US grade right? The tests have some weird figures., rarely going over 400 mph on the FAA tests.

Specifically, which test are your referring to? URL is? There are many reports jammed into the summary page.

My regards,

Widewing

[Guppy35]

Go through Spitfire the History.  There are all kinds of different 'test' Spits listed and finding two from the same mark that aren't off in weights by a bit is hard.

Did the VIII in the tests have a broad chord rudder or the early rudder?  Did it have the pointed tips, normal span wings or clipped?

Was it an early IX without the tropical filter?  Did it have a Universal wing or E wing?  Did it have the pointed rudder or rounded one?  Did it have clipped, normal or pointed long span wings?  

It goes on and on.

In the end a Spitfire VIII totally empty with tropical filter, broad chord rudder and normal span wings vs a Spitfire IX with a tropical filter, broad chord rudder and normal span wings is going to be the difference of the retractable tail wheel and the two inner wing fuel tanks.

[DweebFire]

Guppy,

Thanks for clearing that up. The VIII used in the tests were the old rudder, the normal filter (like the ones on Mk.V spits) and Mk.VII wing tips.

The IX was Merlin 61 engine, regular rudder, likely a Mk.V filter as well since the test was during 1942.

That however is almost exactly the same as our Mk.IX in game and our weights are still off by some 140 + lbs.

Widewing,

I'm not sure about my figures,but it's widely published that the F4U-1 series Corsairs have speeds of at least 417 mph on 100/130 octane.
The tests here  yield much different results. I know this has been shown this before.

Lastly, I have come to the conclusion that the Bf 109K's ang G's late in the war (fitted with Nitrous Oxide boost) could produce in excess of 2000 hp. Our figures don't seem to show that. I could be wrong, but the boost is supposed to raise performance levels by a higher percentage than planes with standard or water-injected WEP... but it all seems like regular WEP on Gonzo's charts.

[leitwolf]

I'm not 100% sure about the K4, but in general AH's 109s dont have NO boost, just regular water/methanol.

[TUXC]

Originally posted by DweebFire
Lastly, I have come to the conclusion that the Bf 109K's ang G's late in the war (fitted with Nitrous Oxide boost) could produce in excess of 2000 hp. Our figures don't seem to show that. I could be wrong, but the boost is supposed to raise performance levels by a higher percentage than planes with standard or water-injected WEP... but it all seems like regular WEP on Gonzo's charts.

G-14 and K-4 in game both have MW-50 (water methanol injection) and perform very well. G-14 is a little slow at altitude, maybe 10mph, but so are a few otherr planes  we have (F6F comes to mind). As for GM-1 (nitrous oxide), 109s were being fitted with MW-50 instead by 1944 due to less weight of the system and the introduction of the DB 605AS and DB 605D engines. These engines gave good performance at altitude without having to resort to nitrous oxide.

Nitrous oxide could only be used above the rated altitude of the engine. I believe 1000m above rated alt for first stage of GM-1 boost, but I'd have to check on that. In a Bf 109g-6 for instance you could not engage GM-1 until around 26000-27000ft or so.

As for spitfireperformance.com., all the actual tests and their data are taken from period documents, and many times scans of the original documentation are included. In cases where the scans are not included I believe that Mike Williams has listed the references. I don't know how much more credible you can get than that. Interpreting the data is a different story since different weights and configurations can have significant effects on performance as has been stated already.

[Squire]

Weight comparisons between the VIII and IX will also differ based on wing armament and wing tips, tail type, ect. Radio model installed? different tires?

The 100 pound discrpancy could be any # of things. Its a very small ammount after all, 1.2 percent? of the 7300 lb weight.

It could be anything.

Also, in AH, you cannot get a weight the weight of an a/c with no oil and hydraulic fuel, only avgas and ammo. There could be a flaw in that calculation as well.

[Widewing]

Originally posted by DweebFire
Widewing,

I'm not sure about my figures,but it's widely published that the F4U-1 series Corsairs have speeds of at least 417 mph on 100/130 octane.
The tests here  yield much different results. I know this has been shown this before.

There's no doubt that there are some rather odd test results found in some war-time test results. But, that doesn't reflect on the website, because Mike and Neil provide a chart showing these differences..



My regards,

Widewing

[SgtPappy]

Another point is that the different aircraft are not always submitted to FAA tests in completely 'new' condition. Gages may also have been faulty or misread, as it was not uncommon. If you take a look at the last test on the Corsair IV, you'll notice its speed as 415 mph. About 10 away from the recorded F4U-1D speed of 425 mph. This may be due to rocket/bomb tabs/hardpoints or other drag causers. no plane was the same.. not even 2 Corsairs built side by side.

In Australia Spitfires were delivered with lots of faulty equipment.

Squire, I think Dweeb stated before about the Spits' configs. Though I'd like to add to his statement that the Mk. VIII and IX both had TR.1133 VHF radio sets at the time. Also, both had identical C-type wings... one difference was that the Mk.VIII had shorter ailerons... not sure if that factors in any weight differences.