Spitfire Mk.XIV vs P-51D Mustang

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RG this is so far from any other cruise speed info about the P-51D that i have ever read, so how can i trust that you havent messed around with these documents on your photo-program ?

I have never heard 425 mph cruise speed from any P-51 pilot, most veterans tell you that its "Max" speed was around 430 mph at 30,000 ft, and cruise speed wouldnt be close to that RG.

Every book and site about the P-51 will tell you the same:
http://www.wpafb.af.mil/museum/research/p51.htm
https://www.quicktechhobby.com/articles/history_of_the_p51_mustang.htm
http://www.daveswarbirds.com/usplanes/aircraft/mustang.htm


Come on! Give me a primary source document supporting this cruise speed, or at least a reputable source, not a warbirds fan site.
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Its not a Fan-site, just a warbirds site.

If you check the Fourth-Fighter Group pages, it says max sustainable cruise of the Spit XIV was 300 mph.
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Checked, 300 mph isnt mentioned.


RG the P-51 has laminar wings, wich means as soon as it does a high G maneuver, it losses speed extreemly fast, alot faster than the Spit ! So turning is an abslolute NO NO for the P-51.

Hey AFDU found out that the Fw-190A turned either tighter or equal to the P-51, and the Fw-190 isnt known for its turning ability


How did you find out this was untrue ?


You suspect ? Is there no clear indication ?
 
The information I've recieved from P-51 pilots (I'm not finished looking for the truth) is that high speed cruiseis not used, even on light (no guns, ammo or fusalage tank) fully restored P-51s the normal cruise speed is 210 to 265mph depending on Plane/prop/engine setup/pilot.

Acording to RR the merlin would fail at the RPMs required for 390mph if extended runs were undertaken. This was fixed after the war for merlins used in commercial aircraft requiring "extended high cruise RPMs".

FYI Allison rods are used in hopped up Merlins as is a Very heavy bottom end main bering girdle to rienforce the block.

I will accept that the P-51 had a better fuel management system than the P-38. It fell into the WPBs refusal to allow Lockheed to install one.

I also believe the Extra thrust ov the weaver effect is mostly theroretical. As I showed (in your other thread) In average conditions the P-38 and P-51 use the same hp/lbs to achieve the same relative top speeds. This would not be true if there was 300-400hp extra being produced by the P-51s radiator.

The fact is that the only extra thrust is produced by the heat exchange of the radiator. The expansion of that air (heated) is the only added thrust. Just like a jet engine Compress the air entering, inject fuel and ignite to provide heat expansion then it exits at a higher velocity producing thrust. That maybe more efficent in the P-51 because of the reduction of air velocity due to the expansion chamber allows a more efficient heat transfer but the difference in the added thrust (over other aircraft) is ONLY the added efficency of the heat exchange. That all of this equipment fills in an area of high drag thus eliminating it is more important than any thrust expelled or created.

The therory that slowing the air then squirting it through a smaller exit creating thrust is Crap it only works porportionaly to the heat added.
 
Soren said:
RG this is so far from any other cruise speed info about the P-51D that i have ever read, so how can i trust that you havent messed around with these documents on your photo-program ?
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So now you are accusing me of modifying the pages from the P-51 pilot's handbook to lie to you about the cruise speed? Jeeze! As soon as someone came up with the original don't you think my rep would be pure mud?

Here, download the .pdf file for yourself: http://www.lanpartyworld.com/ww2/files/air-manuals/usaaf/P-51D PDF/

You owe me an appology dude.


None of which dispute the given cruise tables - they just choose one entry according to their own criteria of selection. Clearly "most economical cruise" settings come from Collumn V. If your definition of cruise speed is maximum distance coverage, this collumn would be the one you'd use.

Sure the cruise speed could be close to that, it just has to be at an output level that the P-51 can sustain continuously.

I really don't see how you can argue with the 1945 revised P-51D/K pilot manual as given to the pilots and mission planners. The first printing might have incorrect info in it, but the 2nd printing includes adjustments for actual combat experiances.


That's what a "fan" site is. A sight that an individual who is a fan of WWII aviation has put up with their interpretation of whatever sources they have access to. There are several classes of sources:

1) Primary source documents - these are always the best. They include actual test documents involving the aircraft in question. Often these are found on military sites complying with the FIA (freedom of information act), or on fan sites where the author has access to primary source documents and provides that info - usually through scans or photo's of the originals.

2) Manufacture's documents - sometimes these are very good, sometimes not so good. You have to watch out for companies which try to make thier accomplishments look more significant than they really were, and the quoting of special case data as normal case data.

3) Books - these are only as good as the primary source documents and the reading/interpretations upon which they are based. Often mistakes in books become "facts". For example -

JANES "All the World's Aircraft" - lists the top speed of the F4U-4 as 425 mph, when we know in fact the top speed was 464 mph. 425 mph was what the USN published back immeadiately after WWII, and this speed was intentially mis-reported.

Francillion's "Japanese Military Airfcraft of WWII" - lists the Ki-44II as having mounted 4 x Ho3 20mm cannon. But we know this is infact impossible as the only feeds for this weapon were round drum magazines and their is no way they could have been fit into the Tojo's wings. Most likely this was a translation or reading error. In Japanese the Ki-44 was the "Type two single seat (or engine?) fighter", where the Ki-45 was the "Type two two seat (or engine?) fighter". The Nick could support four Ho-103's, but there is no way the Tojo could.

4) Air Museums - sometimes these are good, but usually they are of very limited depth. It depends on the level of devotion of the particular museam historian to WWII aircraft in particular. Usually, these just regurgitate the most readily available data, usually from the most popular book sources - i.e. Jane's Warplanes or Francillion.

5) Fan sites - these usually just regurgitate data from other sites or books, but occasionally one of merit can be found, such as the fourth-fighter Group or Mark's pages, or especially RING'S PRO DOCS site (see my new post), which offer primary source documents.

6) Pilot accounts - you have to be careful about thes as pilot memories are often poor w.r.t. the actual details, pilot bias is always a huge factor, and pilots often were not given much technical data during the war and what they were given was often incorrect. And also there are a suprizing number of fakes out there - you have to really double check to make sure a pilot you meet at an airshow was really a pilot and not the tow vehicle driver or gas pumper on the airbase. Also, I've met WWII pilots who also flew in Korea who really cannot distinguish one war from the other - they talk about Mig's in WWII!


This is not true. The laminar flow wings involve what is know as the "laminar flow bucket" (why it's called this I don't know). At angles of attack within the "bucket", there is almost no E loss. This allows moderate turn angles which at very high speed can exceed 5 G's, with almost no E loss.

Soren said:
Hey AFDU found out that the Fw-190A turned either tighter or equal to the P-51, and the Fw-190 isnt known for its turning ability
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Actually it was. The FW190A was known to out-turn the Spitfire at higher speeds - this was one of the reasons it was so dangerous.


Because I found there was a fuel nozzle change in Spring 1944, as listed below. This is what caused them to change the way power was managed on the P-51 from the traditional "auto-lean" and "auto-rich" pilot controls to the "RUN" setting.


Why it was not applied to the larger engines is not mentioned. But I know that in about late Summer 1944 there was a sort of a "lock" on production modifications. Unless it was crutial, changes were not made that would slow production levels. The tooling changes needed to apply the new nozzle technology to other engines (which would require bigger nozzles) was probably deemed not worth the hold up in production. Kinda like the decision on the P-38K - where it was descided that a two week hold up on the P-38L production line was not acceptable even given the performance improvement of the new prop design. We were in the "home stretch" and since we had no pressing need for further performance increases, quantity was stressed over additional quality. Thus my speculation on the reason it was not applied to the larger engines - but there may have been some other reason?

=S=

Lunatic
 

Well, sure, those private P-51's are not going to push the engine. In WWII, the expected life of a P-51 was only 50 sortie hours - they didn't care if the engine burned out after 100 hours. But for existing P-51's, they do everything they can to keep the plane airworthy. Aside from racers using modified engines, they don't even go over 300 mph to preserve the engine.

wmaxt said:
Acording to RR the merlin would fail at the RPMs required for 390mph if extended runs were undertaken. This was fixed after the war for merlins used in commercial aircraft requiring "extended high cruise RPMs".
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The RPM's required are shown in the chart. 2450-2700 rpms was not excessive for a Packard Merlin. Also, Packard Merlins were known to be more durable than RR Merlins - they used superior alloys, superior rings, and were built to more exacting tolerances. RR was much more stressed to pump out engines as fast as possible - many of the tolerances were very rough and the insides of the blocks were often not polished out at all.

I really don't see how you can argue with the chart used by actual WWII pilots and planners to determine range/speed settings for actual combat missions.


wmaxt said:
FYI Allison rods are used in hopped up Merlins as is a Very heavy bottom end main bering girdle to rienforce the block.
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So? Those planes produce what - 3000 HP?


The P-38 was slower. Only if you use data from Lockheed's internal tests does the P-38L have a faster top speed. Actual speeds were ~415 for the P-38L, ~437 mph for the P-51D according to the USAAF.

But that is not the proper comparison. The proper comparison is the P-51B vs the Spit IX with the Merlin 66. The engines are of the same HP and the blower gearing is about the same. The Spit IX enjoys about 1000 lbs less weight and is aerodynamically cleaner in the wind-tunnel - yet the P-51B is a good 35-45 mph faster!



The air is slowed to increase its pressure and contact time as it passes through the radiator.

The concept of thrust is not crap. Heating the air causes it to expand and this can either be regulated by the pressure nozzel to maximise pressure and therefore thrust, or it can be let to run free stream which will not maximize pressure/thrust. Holding the air in the compression chamber means that the energy of the expansion occures within that chamber and is applied against the plane when it is vented, rather than occuring after it has been expelled and thus not generating thrust.

=S=

Lunatic
 
The P-38 speed again is back to the METO 414mph? How come the P-51 people always have to handicap the P-38 to prove their point.

Try the WEP 443mph if you want to compare them or at least use the same configuration and power setting. Just because it's realese was from Lockheed and was late in the 80's and by a third party at that doesn't make it wrong. It is common knowledge that the P-38 specs are METO throttle settings and the P-51 are WEP.

The thrust is only proportional to the heat generated period. The thrust effect is not in pratice significantly greater. the Mustange ie better at managing the boundry layer and the actual heat transfer but it never translated into 300/400hp thats more thrust than a V-1! The heat transfer energy is not that high no matter how efficiently it's managed.

You have a theory and a statement that I can't find any verification outside of your posts and only partialy in 2 out of ~50 other references that either one was really effective or utilized to the extent you propose. But I have read they were not.

I will continue to look into this and I'll change my mind If I come up with some convincing data. So far I've much more against it than for it.
 

Im not accusing you of anything RG, im just asking as its so far from any other cruise speed data about the P-51 that I've ever read. And it is also not what an WW2 veteran P-51 pilot will tell you, he will tell you that cruise speeds never exceeded 300 mph.

But I appologize if i have offended you, as it wasnt intended to be an offensive question.


And the speed in this collum, is the speed in wich the P-51 will be engaging the Spit with then.


No arguing, just a tad of disbelief as this is something I've never heard before.


That RG, is for very high speed only ! The P-51D's laminar flow wings lowered the drag, but this came at the cost of lower lift, especially under high G loads !

Actually it was. The FW190A was known to out-turn the Spitfire at higher speeds - this was one of the reasons it was so dangerous.
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Yes the "Dora" was, but not the "Anton", the "Anton" series only roll'ed better than the Spitfire.

It was an A4 wich was tested by the AFDU against the P-51, and it could follow the P-51 in low-speed turns, and outturn it in High-speed turns.
 

No the USAAF speed figures are for the P-38L at wep power, as tested. Where those Lockheed figures come from, and what the plane conditions actually were, is anyone's guess. I can reference NAA P-51 tests showing speeds in excess of 450 mph, but those are not the relevant figures for comparison. And even USAAF figures are understated - the tested speed of the P-51D was 443 mph @ 25k, 438 mph @ 30k.


The P-51B generated about 1000 lbs of thrust off the prop, and about 350 lbs of radiator thrust, and about 400 lbs of cooling system drag at 25,000 feet at full speed, and weighed about 8500 lbs. The V1 generated about 660 lbs of thrust and weighed about half as much, and had NO cooling system drag. It's not unreasonable at all.



My only difference with the explanation quoted above is that I think that overall effect was due to "thrust" and parasitic drag reduction, rather than thrust alone.

=S=

Lunatic
 

Not at all. That is the speed the P-51 would use to cross friendly territory on the way to the combat zone. Once it reached the area where it expected to encounter the enemy it would begin sweeps at the highest possible continuous cruise speed - but proably a cruise speed taken from column II rather than column I.


Well I've given you the link to the manual's PDF file, and many other manuals can be found on RING's PRO site (see my new post with main entry points).


The lift is uneffected until the bucket is exceeded. At high speeds (in excess of 300-350 IAS) the P-51 could hold a high speed turn w/o loosing E and gain advantage against it's foes - if the pilot was experianced enough and cool enough to exploit this.


No, at speeds above about 300 IAS the Anton out-turned the Spit. It used sort of a dish turn to do so (relatively mild bank angle) quite successfully.

Soren said:
It was an A4 wich was tested by the AFDU against the P-51, and it could follow the P-51 in low-speed turns, and outturn it in High-speed turns.
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P-51 pilots consistantly report they could out-turn the FW190 at high speeds.

=S=

Lunatic
 
If it were one pilot, or just one account, perhaps.

But it is consistant. P-51 pilots reported that they could easily out-turn the 109 at high speeds, and that they could also out-turn the 190 but not so easily.

=S=

Lunatic
 
RG_Lunatic said:
If it were one pilot, or just one account, perhaps.

But it is consistant. P-51 pilots reported that they could easily out-turn the 109 at high speeds, and that they could also out-turn the 190 but not so easily.

=S=

Lunatic
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I hope you don't mind me using one of your previus comments, but:

THAT IS PURE POOP !

In all German tests and mock dogfights the 109 ALWAYS outturned the 190 !

And let me remind you that 109 pilots found it quite easy outturning a P-51 and P-47 at all speeds ! Even a Three cannon G6 would outturn a P-51 !

The "Anton" wouldnt outturn a Spit, only at speeds in excess of 400 mph ! Your stats are for the "Dora's", wich could happily make a dish turn against a Spit and come out the victor, and even more easely do it to a P-51.

P-51 pilots consistantly report they could out-turn the FW190 at high speeds.
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FW pilots consistantly report outturning and outmaneuvering the P-51's and P-47s very easely at high speeds, especially the "Dora" pilots. And the AFDU's tests confirm this.

Whenever a "Dora" was in the proximity, the escorting P-51's should be very careful not to attract attention ! If seen the P-51 could forget all about dogfighting the "Dora", as the "Dora" was superior in every aspect of flight except diving !

As for the P-51.... RG there is no way that a P-51 can maintain a 5G turn with NO E loss, its simply impossible ! The Laminar wings from the start simply produced to little lift, and this would get worse if the AoA increased. Also the P-51 didnt have either good Wing-loading or Power-loading to start with, so there's simply no way that what you said is true RG.
 
RG,

You have my respect but here I think your off track.

The V-1 comparison was ment to be toung in cheek - my bad.

The P-38 speed of 414mph when listed with horse power is stated at 1,400 to 1,475. This is Normal full throttle or METO. the P-38J is listed by both Lockheed and Allison at 1,600hp and the L at 1,750hp WEP.

Why would the P-51 be derated and not the P-38? As you noted the 450mph P-51B (The faster of the P-51B/D/K line) was at a 5/1 lbs/hp weight not the 5.6/1 of the Mil/Average of the normal statistics a significant difference. AND it's still slower than your claims and under weight!

Why would Lockheed internal tests be weighted unequaly - my understanding is that these aircraft were set up Mil/average expected conditions.

I think your just keeping the discussion heated up/going!
 

Sure, because just like the British turn's were tested at speeds of 250 IAS or below.

Soren said:
And let me remind you that 109 pilots found it quite easy outturning a P-51 and P-47 at all speeds ! Even a Three cannon G6 would outturn a P-51 !
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Pure poop. 109's turned badly at speed. Even your own source you claim says otherwise actually claims this is so when put in context.

Soren said:
The "Anton" wouldnt outturn a Spit, only at speeds in excess of 400 mph ! Your stats are for the "Dora's", wich could happily make a dish turn against a Spit and come out the victor, and even more easely do it to a P-51.
Click to expand...

What evidence do you have that the Dora could out-turn the Anton? It could power through a turn better, but its raw turn rate was worse.

P-51 pilots consistantly report they could out-turn the FW190 at high speeds.
Click to expand...

Soren said:
FW pilots consistantly report outturning and outmaneuvering the P-51's and P-47s very easely at high speeds, especially the "Dora" pilots. And the AFDU's tests confirm this.
Click to expand...

No the AFDU test does not say this at all. See my other post in reply to your out of context quote about the 109's turn.

Soren said:
Whenever a "Dora" was in the proximity, the escorting P-51's should be very careful not to attract attention ! If seen the P-51 could forget all about dogfighting the "Dora", as the "Dora" was superior in every aspect of flight except diving !
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Says who?


Do you realize how wide a 5G turn at 400 mph is?

=S=

Lunatic
 
Sure, because just like the British turn's were tested at speeds of 250 IAS or below.
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No RG, thats not the case.

Pure poop. 109's turned badly at speed. Even your own source you claim says otherwise actually claims this is so when put in context.
Click to expand...

Now thats pure poop.


What evidence do you have that the Dora could out-turn the Anton? It could power through a turn better, but its raw turn rate was worse.
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Wrong again RG.

It is commonly known that the "Dora" turned alot better than the "Anton" at all speeds, and this is also confirmed several times by Hans Werner Lerche, and ALWAYS by FW pilots ! (Mock dogfights were carried out)

No the AFDU test does not say this at all. See my other post in reply to your out of context quote about the 109's turn.
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Yes it does RG, but not the one with the 109 offcourse. I said "FW" pilots remember !

Says who?
Click to expand...

The pilots and the Spec's RG.


Do you realize how wide a 5G turn at 400 mph is?
Click to expand...

Do you realize how much 5G is ?
 
At 200 mph the amount of turn required to achieve 5 G's is substantial. The plane's ability to turn is usually the limiting fact on actual turn radius.

By 400 mph the amount of turn required to achieve 5 G's is relatively slight. The pilot's G-tolerance is usually the limiting factor on actual turn radius.

=S=

Lunatic
 
the spitfire in my mind is a beautiful a/c and so is the p 51 mustang.

"So wich one would you bet your money on in a clash between the two"

if you are british the spit ,hurricane, avro lank are part of our folklore ,these are the a/c that saved us from the evil nazi swarm that tryed in vain to destroy our
infrastructure and moral, and leave us open to invasion.

leaving that aside, any machine is only has good as the person in control ,no matter what cannons ,303's .50 it sports or how fast it turns, if he hasn,t had chance to hone is skills, and the opponent has ,then my moneys on the opponent.
if on the other hand both pilots were experianced, the spit would have the advantage but the outcome would still depend on other factors.

they main difference between the two planes was range. which made the p51 a very useful a/c in its own right.
 
The thread... IT IS ALIVE


P-51 D because it was available and more reliable, safer and with excellent range and overall the best fighter of the war.
 
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