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Wildnoob
11-17-2009, 01:15 PM
Not related to the sim, but I was in a forum were a member said the 487 mph top speed stated for the P-51H is wrong, and actually it should be 450 mph. According to him, the speed was recalculated for 471 mph by North American with a clean wing. Then dropped for 450 mph supposedly due to hacks for bombs and rockets.

His source would be "engineers in a forum" (in which the link was not posted).

As I didn't manage to find anything about such claimed error, was wondering if this is a myth or not.

Wildnoob
11-17-2009, 01:15 PM
Not related to the sim, but I was in a forum were a member said the 487 mph top speed stated for the P-51H is wrong, and actually it should be 450 mph. According to him, the speed was recalculated for 471 mph by North American with a clean wing. Then dropped for 450 mph supposedly due to hacks for bombs and rockets.

His source would be "engineers in a forum" (in which the link was not posted).

As I didn't manage to find anything about such claimed error, was wondering if this is a myth or not.

Gibbage1
11-17-2009, 01:34 PM
http://home.att.net/~jbaugher1/p51_13.html (http://home.att.net/%7Ejbaugher1/p51_13.html)

But we dont have a P-51H. Does it matter?

M_Gunz
11-17-2009, 01:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wildnoob:
Couldn't find anything about this. I'd like to ask for the pony experts here if this is truth. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/88.gif http://forums.ubi.com/images/smilies/88.gif http://forums.ubi.com/images/smilies/metal.gif http://forums.ubi.com/images/smilies/88.gif http://forums.ubi.com/images/smilies/53.gif http://forums.ubi.com/images/smilies/88.gif http://forums.ubi.com/images/smilies/88.gif

JtD
11-17-2009, 01:57 PM
I think the guy has based his opinion on the data provided on the bottom of this (http://www.wwiiaircraftperformance.org/mustang/mustangtest.html) page. You can find 7 interesting documents there.

Gibbage1
11-17-2009, 02:07 PM
http://www.wwiiaircraftperformance.org/mustang/p-51h-booklet-pg12.jpg

Looks like it was still pulling over 475 with the wing racks.

Waldo.Pepper
11-17-2009, 02:33 PM
How come there is never a knock down drag out fight about the top speed of the PZL-11?

I heard if you remove the wheel spats you gain another 5 mph.

doraemil
11-17-2009, 02:49 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Waldo.Pepper:
How come there is never a knock down drag out fight about the top speed of the PZL-11?

I heard if you remove the wheel spats you gain another 5 mph. </div></BLOCKQUOTE>


in game ... i'm guilty of flying fast n close to the ground and bumping the wheels off the Stuka or P11 . . . or any sort of planes that have under carriage . . . just b/c they fly better . . .

Romanator21
11-17-2009, 02:58 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">How come there is never a knock down drag out fight about the top speed of the PZL-11?

I heard if you remove the wheel spats you gain another 5 mph. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif 50 pager for sure!

Wildnoob
11-17-2009, 03:06 PM
Hope things were clarifly now. Had issues with my conection, just could edit and let the topic intelligible now.

Kurfurst__
11-17-2009, 03:17 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wildnoob:
Not related to the sim, but I was in a forum were a member say the 487 mph top speed stated for the P-51H is wrong, and actually it should be 450 mph. </div></BLOCKQUOTE>

AFAIK he is right, the 487 mph top speed was an early calculation of performance, actual flight tests with the plane in operational conditions yielded around 450 mph.

Gibbage1
11-17-2009, 03:23 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
AFAIK he is right, the 487 mph top speed was an early calculation of performance, actual flight tests with the plane in operational conditions yielded around 450 mph. </div></BLOCKQUOTE>

Sources? The H had around 600HP more then the D, significantly lighter, yet it only gained 12MPH? I think your math is a little off.

Kurfurst__
11-17-2009, 03:37 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Gibbage1:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
AFAIK he is right, the 487 mph top speed was an early calculation of performance, actual flight tests with the plane in operational conditions yielded around 450 mph. </div></BLOCKQUOTE>

Sources? The H had around 600HP more then the D, significantly lighter, yet it only gained 12MPH? I think your math is a little off. </div></BLOCKQUOTE>

http://www.wwiiaircraftperform...ang/p-51h-64182.html (http://www.wwiiaircraftperformance.org/mustang/p-51h-64182.html)

Actual test, did 451 mph under normal clean fighter configuration (wing racks present).

Kettenhunde
11-17-2009, 04:12 PM
How many P-51H's ever ran at 90 inHG in service?

The 1949 standard service performance notes do not show that rating....

http://www.wwiiaircraftperform..._-_22_March_1949.pdf (http://www.wwiiaircraftperformance.org/mustang/F-51H_Mustang_SAC_-_22_March_1949.pdf)

Gibbage1
11-17-2009, 04:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
How many P-51H's ever ran at 90 inHG in service?

The 1949 standard service performance notes do not show that rating....

http://www.wwiiaircraftperform..._-_22_March_1949.pdf (http://www.wwiiaircraftperformance.org/mustang/F-51H_Mustang_SAC_-_22_March_1949.pdf) </div></BLOCKQUOTE>

We have numbers ranging from 411mph to 487. Thats quite a range. Who knows the truth? Well all that I see is the "accepted" top speed of the D was ~430MPH, and the H was lighter, cleaner, had 600HP more, yet can only manage less or 20MPH more? Seems kinda odd. Thats all im saying.

Kettenhunde
11-17-2009, 04:35 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">yet can only manage less or 20MPH more? Seems kinda odd. </div></BLOCKQUOTE>

Not considering power is cubed, bud.

Gibbage1
11-17-2009, 04:41 PM
Not just power, but weight and drag. I know weight has little effect on tops speed other then how long it takes to get there, but still. I would expect more then 20MPH. Is there something compairable like the Griffen Spit upgrade that also got a big bump in power, but little gain in speed?

Kurfurst__
11-17-2009, 04:47 PM
Not sure if that +600 HP was also true at altitude... I suppose it was only true at low altitudes, considering it was 'boosted' output with ADI. What was the output of the -7 at 67" and the -9 at 90" at critical altitude? From that on you can get fairly good apprx. numbers using cubic relations between speed and power.

Probably true that at low altitude, it may have been much faster than just 20 mph. (under identical conditions, that is).

Gibbage1
11-17-2009, 04:49 PM
Thats true. It seems that the 2200HP was limited to low alittude. After 9000ft (?) it looks like it was pumping 1700, and thats not a big improvement. Ill look better once I get home, but I think thats the key.

M_Gunz
11-17-2009, 04:54 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">yet can only manage less or 20MPH more? Seems kinda odd. </div></BLOCKQUOTE>

Not considering power is cubed, bud. </div></BLOCKQUOTE>

Numbers vs Math there. You're dealing with some who can tell a bigger number from a smaller one and even tell the
difference though it might require a calculator but CUBES? I doubt they know the curve at all.

Buzzsaw-
11-17-2009, 05:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
How many P-51H's ever ran at 90 inHG in service?

The 1949 standard service performance notes do not show that rating....

http://www.wwiiaircraftperform..._-_22_March_1949.pdf (http://www.wwiiaircraftperformance.org/mustang/F-51H_Mustang_SAC_-_22_March_1949.pdf) </div></BLOCKQUOTE>

Once again, we have an example of Crumpp not actually reading the document he is linking.

P-51H's would not routinely use 90 inches in peacetime 1949, neither did the British use max. boost levels for their fighters postwar. Why unnessesarily stress an expensive component when you are not in a combat enviroment?

90 inches boost was planned for those P-51H's going into combat versus the Japanese, and required the use of the newly formulated 115/145 American fuel, which was much more resistant to pre-ignition at low cruise speeds, a problem with the British formulated 100/150 octane.

The 1949 Pilot notes in fact do actually show clearly that the aircraft was authorized to use over 80 inches MAP.

Once again the link:

http://www.wwiiaircraftperform..._-_22_March_1949.pdf (http://www.wwiiaircraftperformance.org/mustang/F-51H_Mustang_SAC_-_22_March_1949.pdf)

Nowhere does the document mention boost levels. But we can estimate boost by looking at a couple of related notations.

First of all, the document notes that water injection is used. Only V-1650-9's had water injection available. Horsepower is noted at 2250, pretty closely matching horsepower figures for boost seen below for the V-1650-7 WITHOUT water injection, at +28 lbs boost. That shows max horsepower at just below 2200.

http://www.spitfireperformance.com/merlin66hpchart.jpg

From that comparision, we can see the V-1650-9 is producing more than the 1650-7 at 28 lbs, obviously it is running higher boost, combined with water injection. The reason the V-1650-9 produces more horsepower, is obviously, because it had the higher boost, and water injection, better combustion resulting from the additional oxygen being introduced into the mixture, hence the max. horsepower figure of 2250 shown in the 1949 Pilot notes.

Exactly what the boost level of the 1949 Mustang allowed is not clear, we can only estimate, probably it was up around 85 inches. Again, lower than wartime rating, but the aircraft was more than capable of using the higher boost levels at a moments notice. The supercharger regulator settings could be adjusted in an afternoon.

Buzzsaw-
11-17-2009, 05:31 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:

http://www.wwiiaircraftperform...ang/p-51h-64182.html (http://www.wwiiaircraftperformance.org/mustang/p-51h-64182.html)

Actual test, did 451 mph under normal clean fighter configuration (wing racks present). </div></BLOCKQUOTE>

It's amazing that Kurfie can actually post this with a straight face.

The aircraft in this test is tested at 67 inches MAP, a level of boost which the USAAF stopped using in its combat Mustangs in July of 1944, when 100/150 octane came into general use. After that, even P-51B's were authorized to use 75 inches MAP.

yuuppers
11-17-2009, 05:42 PM
When one reads the stats for airspeed is this Indicated airspeed or True airspeed?

Buzzsaw-
11-17-2009, 05:46 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by yuuppers:
When one reads the stats for airspeed is this Indicated airspeed or True airspeed? </div></BLOCKQUOTE>

Are you talking about the 1949 pilot notes?

In that case, it is TAS. In knots.

412 knots max, or 475 mph in Interceptor mode with wingracks. That at my estimated 85 inches MAP.

The version at 90 inches MAP hit 487mph TAS in clean condition.

Kurfurst__
11-17-2009, 05:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Buzzsaw-:
It's amazing that Kurfie can actually post this with a straight face.

The aircraft in this test is tested at 67 inches MAP... </div></BLOCKQUOTE>

Yup, because unlike you, I can even read... http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

It reached 451 mph at 90 inches at ca 21k feet, and 408 mph at 67 inches at the same altitude.

Sections D2, D3.

BillSwagger
11-17-2009, 05:58 PM
it doesn't surprise me that there would be a significant speed difference.

Most planes are tested with a clean configuration. With planes like the mustang, which rely more on their profiles to get performance, it wouldn't surprise me if the pylons or wing racks slowed it down more significantly than planes that use a lower power to weight ratio/ or was it higher....
I might have these backwards, but i'm speaking from the top of my head.

someone can clear that up for me.
Which planes are more senstive to drag, higher or lower power to weight?


thanks



also keep in mind the faster a plane goes, the less available thrust. +600hp, might translate to more acceleration before it makes a bigger gain in top end performance.

Bill

Buzzsaw-
11-17-2009, 06:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Buzzsaw-:
It's amazing that Kurfie can actually post this with a straight face.

The aircraft in this test is tested at 67 inches MAP... </div></BLOCKQUOTE>

Yup, because unlike you, I can even read... http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

It reached 451 mph at 90 inches at ca 21k feet, and 408 mph at 67 inches at the same altitude.

Sections D2, D3. </div></BLOCKQUOTE>

Salute Kurfie

Yes, you caught me there, congratulations I thought you were referring to another test.

However, I am going to catch you again now that I have had a chance to look over your test.

Your claim that that the aircraft was 'clean' except for bomb/tank racks is false.

The test you are referring to was flown in 'standard' fighter configuration for 1946, which was with BOMB and ROCKET racks.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
IV Condition of the Aircraft Relative to Tests

A. The P-51H differs from earlier models in that the fuselage lines are somewhat cleaner, the wing has been redesigned for lower drag, the empennage section has also been redesigned and the airplane is equipped with four bladed Aero Products propeller

B. All tests at the fighter configuration (bomb and rocket racks only) were flown at a take-off weight of 9544 lbs. and approximately 25.4% M.A.C., wheels up, and 25.9% M.A.C., wheels down. This included ballast for 1820 rounds of 50 caliber ammunition, six 50 caliber guns, and a full supply of fuel, oil, and water.
</div></BLOCKQUOTE>

As we all know, the additional drag added when HVAR rocket racks are present is enough to impose a significant penalty.

So your attempt to suggest that a 'clean' P-51H was limited to 451 mph is completely false.

First of all, a plane with bomb racks is not 'clean', and one with BOTH bomb and rocket racks is certainly not.

Wildnoob
11-17-2009, 07:02 PM
Thank you all for the soberb informations. http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

horseback
11-17-2009, 07:11 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Waldo.Pepper:
How come there is never a knock down drag out fight about the top speed of the PZL-11?

I heard if you remove the wheel spats you gain another 5 mph. </div></BLOCKQUOTE>Only if you didn't take off from a muddy field--and there seems to be a lot of squabbling over what 5 mph translates into in kph...are those nautical miles or statute miles, and does Kurfy have a chart revealing a direct correlation to the superior performance of the Bf 109C in either standard?

cheers

horseback