Wasn't the P-51 the best escort fighter of the war?

IMO - Steve is correct. Pre-1939 all or nearly all fighter aviation was Pursuit/Interceptor -------------> fast, climb fast, turn tight to best the opposing challengers for battlefield superiority or air defense of the homeland.

Those design objectives dictated HP available to HP required and wing loading discussions - fuel was placed in the fuselage to optimize roll and armament options.

Long range escort was deemed impossible for single engine fighters because the necessary fuel fractions were too high to maintain climb and maneuverability goals with existing engines. High altitude performance objectives dictated turbo superchargers for AAF for Interceptor role, and basically ignored by USN as not necessary for fleet operations scenarios of the day. Two stage/two speed superchargers were conceptualized but not in practical stages of development.

The Mustang broke ground on fuel storage in the wings - not because of foresight but because the Meredith Effect advantages to drag reduction was a REQUIRED part of both the original P-509 proposal to AFPC but maintained center stage during the development of the NA-73 Specifications. No room for fuel in the fuselage (or so they thought) because the stability and control issues were deemed a major issue to successful development and acceptance from RAF.

That said, the RAF continued to press NAA for more range options leading NAA to develop auxiliary fuel cells to occupy the gun bay/ammo chute section of the wing. It was tested and put into production as kits for an extra $25/per aircraft. With the fuel cells and two remaining cowl mounted 50 caliber guns, the Mustang I was capable of 1500 miles straight line range, about a 50% increase over existing capability. Projected Combat Radius was London to Berlin (in 1940). Not very practical for intruder type missions but an excellent option for Recon. I have not found docs to support operational use as extended range recon but the installation and maintenance instructions were all in RAF Mustang I Maintenance Manuals.

IMO the RAF get perhaps a little too much credit for the design attributes of NA-73, but perhaps a little less credit than they deserve for the impetus of NAA to craft many improvements to the operability and handling qualities of the P-51 with constant flow of suggestions and issue documentation coming from RAE and combat ops experience.

Complicating things in 1936/37 were, for the British, the notion that fixed pitch props were good enough for fighters. For the Germans, they didn't have a 1000-1100 engine in service yet. They had two in development. For the Americans the Allison was very much in the development stage.
If through magic you had a Mustang airframe/aerodynamics in 1936/7 and tried to power it with a Merlin II/III (87 octane fuel) and the fixed pitch prop you would have had a real disaster on your hands.
Not only was the engine rated at 880hp for take-off instead of the 1150hp of the -39 Allison the fixed pitch prop crippled both take-off and climb, not only by being inefficient, but by being so inefficient that it required running the engine at 2000-2300 rpm for take-off and climb instead of the 880hp at 3000rpm rating or even the 2600rpm 30 minute climb rating. Unless you could lighten up the Mustang airframe by about one ton you might never get the plane out of a British 1936/37 airfield. The Mustang/early Merlin combination might be fast in a straight line (especially at altitude) but it's ability to actually fight may be suspect. Even changing to an eight. 303 gun armament, cutting fuel to 120 US gallons and getting rid of armor and self sealing tanks may not get rid of enough weight unless you make the structure lighter.

For the British by 1941 you had not only the Merlin 45 with several hundred more HP for take-off, you had the constant speed prop that allowed very good use of the power, for very little change in engine/powerplant weight.

This last and about 15,000 other posts by SR6 makes me believe he is a resuscitated incarnation of Kelly Johnson, Don Berlin, or Ed Heinemann.... just come back to haunt wannabes.

No disrespect meant to a few folks here who can draw on similar levels of experience, knowledge and analysis-ability, but rather "wow!" to you all!

Shortround6 said:

Complicating things in 1936/37 were, for the British, the notion that fixed pitch props were good enough for fighters. For the Germans, they didn't have a 1000-1100 engine in service yet. They had two in development. For the Americans the Allison was very much in the development stage.
If through magic you had a Mustang airframe/aerodynamics in 1936/7 and tried to power it with a Merlin II/III (87 octane fuel) and the fixed pitch prop you would have had a real disaster on your hands.
Not only was the engine rated at 880hp for take-off instead of the 1150hp of the -39 Allison the fixed pitch prop crippled both take-off and climb, not only by being inefficient, but by being so inefficient that it required running the engine at 2000-2300 rpm for take-off and climb instead of the 880hp at 3000rpm rating or even the 2600rpm 30 minute climb rating. Unless you could lighten up the Mustang airframe by about one ton you might never get the plane out of a British 1936/37 airfield. The Mustang/early Merlin combination might be fast in a straight line (especially at altitude) but it's ability to actually fight may be suspect. Even changing to an eight. 303 gun armament, cutting fuel to 120 US gallons and getting rid of armor and self sealing tanks may not get rid of enough weight unless you make the structure lighter.

For the British by 1941 you had not only the Merlin 45 with several hundred more HP for take-off, you had the constant speed prop that allowed very good use of the power, for very little change in engine/powerplant weight.

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Steve - I don't disagree your point about 1940/1941 Mustang airframe being underpowered in 1937. That said, the NAA 'Mustang' would have looked very much like the P-509 at 6000 pounds, smaller airframe - with same in-line engine cooling scheme that led to the Mustang I. It would have been more like the XP-46 or XP-36 if using the radial. There were PD's on both in 1937/1938 but no internal funding to build on spec.

Of course, d-dog being among the, perhaps not so, "few" and worthy of his own .

Not being shy about my own poorly informed state and perhaps for the benefit of others who may be similarly disadvantaged, I will ask, "what is a P-509?"

drgondog said:

Not entirely true - recall that even with the Allison F3R the Mustang I was quite bit faster than the Spit V, and with the Merlin 61 dropped in it was quite a bit faster than the Spit IX - same engine. No Mustang could turn with either the Spit or Hurricane - or A6M. But speed, acceleration, zoom climb and dive advantage usually presents favorable conditions in a fight. P-51 fight Spit - don't get into turn or climb fight -

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I was just saying you cant just confer properties from aircraft from a different era. If you could give the Mustang airframe to the British in 1936 you also need to give the engine prop and fuels available in 1940. The Spitfire and Hurricane were supposed to be interceptors and the design started before the Chain Home radar was planned. Take of and rate of climb was more important than combat ability, after all it was thought impossible to escort a bomber from Germany to UK. Obviously things like variable pitch and C/S props were being considered as were improved fuels but they weren't there in 1936. Similarly with the 109, to have much more internal fuel it would have to have it and been up to the job required with the engines fitted in the early models with circa 650HP.

oldcrowcv63 said:

Of course, d-dog being among the, perhaps not so, "few" and worthy of his own .

Not being shy about my own poorly informed state and perhaps for the benefit of others who may be similarly disadvantaged, I will ask, "what is a P-509?"

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The P-509 was the Allison Powered High Speed Pursuit preliminary design that went to AFPC in mid march 1940 along with the specifications that became the NA-73 after a month of idea exchange between RAF/BAM and NAA. In other words the 'baby Mustang'

Brother, can you quit it with the fantastical what ifs?

pbehn said:

if war came in 1938 not 1939 it possibly wouldn't have.

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pbehn said:

If you allow a 1940 Bf109 to have a Mustangs

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pbehn said:

If the P-51 ( if a time machine donated its aerodynamics) .

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pbehn said:

And what if the RAF had 1000 trained pilots

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I'm all for discussing hypothetical occurrences based on actual available tech and events, for example, had HMS Glorious survived, would Captain D'Oyly-Hughes have been executed like Admiral Byng, dismissed from service, acquitted at courts-martial. But when you're introducing time travel we're entering the real of the stupid. We have a place for this, the what'if forum.

One position is that the Mustang was the best escort fighter of the war. Is it necessary to rely on time travel and what'ifs to have an alternative position on the Mustang?

Wasn't the P-51 the first one to cover the bombers all the way to Germany and back on their flights. I believe it was, that was the best plane for it.
why is this post putting it down at dec. 9, 2019. when it is May 7,2020.

Said the pot. LMAO

Admiral Beez said:

Brother, can you quit it with the fantastical what ifs?
I'm all for discussing hypothetical occurrences based on actual available tech and events, for example, had HMS Glorious survived, would Captain D'Oyly-Hughes have been executed like Admiral Byng, dismissed from service, acquitted at courts-martial. But when you're introducing time travel we're entering the real of the stupid. We have a place for this, the what'if forum.

One position is that the Mustang was the best escort fighter of the war. Is it necessary to rely on time travel and what'ifs to have an alternative position on the Mustang?

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I was responding to your "what if" about a Bf109 having the range of a Mustang in the Battle of Britain. It requires the transfer of technology from 1940 to 1935, it also requires the prior implementation of the philosophy of protecting bombers into the LW. The LW suffered huge losses of bombers in its campaigns for all sorts of reasons from the start in Poland, its strength was at a peak before the invasion of France and after that it declined through the war. Goering didn't insist on close protection of his bombers as a military strategy, he insisted on it because he was running out of bombers and crews. That was actually the crux of the battle whether the LW ran out of bombers and crews before the RAF ran out of front line pilots. The fighter to bomber ratio on the raids on London was huge, but only because the LW had lost much of its bomber force and consolidating what was left into single raids with one objective was the only option.

Colkid said:

Wasn't the P-51 the first one to cover the bombers all the way to Germany and back on their flights. I believe it was, that was the best plane for it.
why is this post putting it down at dec. 9, 2019. when it is May 7,2020.

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Actually the P-38H was the first to escort into Germany, to the target and back to RV in November 1943.

drgondog said:

Steve - I don't disagree your point about 1940/1941 Mustang airframe being underpowered in 1937. That said, the NAA 'Mustang' would have looked very much like the P-509 at 6000 pounds, smaller airframe - with same in-line engine cooling scheme that led to the Mustang I. It would have been more like the XP-46 or XP-36 if using the radial. There were PD's on both in 1937/1938 but no internal funding to build on spec.

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I would certainly agree that North American would have schemed a different plane 2-3 years earlier to suite engine power availability and expected war load (guns/ammo. armor/protection)

The point I was trying to make was that in 1936/37 it was not possible to make a viable long range single engine escort fighter due to other considerations than simply desire to do so and streamlining/drag-fuel capacity.
Many of these considerations are overlooked by some of our modern day armchair air marshals
British, as I have said multiple times, shot themselves in both feet with their propeller selection. If you can't get the airplane off the ground with a fixed pitch prop without crashing into the trees at the end of the field it doesn't matter what the theoretical range is. The two pitch prop helped with take-off but the plane was still at a severe disadvantage in combat. The prop was shifted to high pitch as soon as the airspeed hit about 140-160mph (?) in the climb out and stayed fixed until the plane was approaching the landing field.

See: Spitfire Mk I K.9793 Trials Report
With a two pitch prop the engine was never run at more than 2400rpm when climbing in coarse pitch, despite the engine being rated at 2600rpm for 30 minutes. If you run the engine faster the prop is running at too high an rpm for the pitch and you don't get anymore thrust.

100 octane fuel, constant speed propellers and better engines/superchargers allowed for much greater power/thrust for a relatively small increase in weight, the air fields were made bigger and even allowable landing speeds were increased allowing for heavier aircraft.

At what point a viable escort fighter became possible I don't know but you are going to need the constant speed prop and the better engines/fuel.

Shortround6 said:

...
The point I was trying to make was that in 1936/37 it was not possible to make a viable long range single engine escort fighter due to other considerations than simply desire to do so and streamlining/drag-fuel capacity.
Many of these considerations are overlooked by some of our modern day armchair air marshals
British, as I have said multiple times, shot themselves in both feet with their propeller selection. If you can't get the airplane off the ground with a fixed pitch prop without crashing into the trees at the end of the field it doesn't matter what the theoretical range is. The two pitch prop helped with take-off but the plane was still at a severe disadvantage in combat. The prop was shifted to high pitch as soon as the airspeed hit about 140-160mph (?) in the climb out and stayed fixed until the plane was approaching the landing field.
...

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We can note that British were making a long range bomber powered by a single Merlin II and a 2-pitch prop by 1936. It managed to take off with 200 gals of fuel and 1000 lbs of bombs from the runaways of the day, in normal service.

If the current doctrine prescribes that something can't be done, it will not be done, at least not in a timely manner.

tomo pauk said:

We can note that British were making a long range bomber powered by a single Merlin II and a 2-pitch prop by 1936. It managed to take off with 200 gals of fuel and 1000 lbs of bombs from the runaways of the day, in normal service.

If the current doctrine prescribes that something can't be done, it will not be done, at least not in a timely manner.

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The Battle couldn't perform without a variable pitch prop which was by de Havilland, single engine aircraft could. The difference is the declaration of war. Wiki says there were 175 Spitfires which is approximately how many were produced up to the declaration. RR and Bristol had formed the ROTOL company to develop propellers in 1937 and the Merlin started to be fitted with an agreed standard drive to do it, the question is which one and when. The requirements of the Battle were pretty much the same as a civilian passenger plane in terms of speed range, but different from that of a fighter.

Shortround6 said:

At what point a viable escort fighter became possible I don't know but you are going to need the constant speed prop and the better engines/fuel.

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At what point was it ever considered? The early variants of the B-17 were considered good enough to operate without escorts but comically later ones weren't. The turret armed Wellington was going to shoot down defenders as quickly as they were sent up. I often wonder who tested these theories out, if indeed they did at all.

pbehn said:

The Battle couldn't perform without a variable pitch prop which was by de Havilland, single engine aircraft could.

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I'm not quite following you there...

The difference is the declaration of war. Wiki says there were 175 Spitfires which is approximately how many were produced up to the declaration. RR and Bristol had formed the ROTOL company to develop propellers in 1937 and the Merlin started to be fitted with an agreed standard drive to do it, the question is which one and when.

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Air ministry can buy a batch of Hurricanes and/or Spitfires with a 2-pitch prop well before ww2 starts. Just like they bought Battles and Blenheims with 2-pitch prop.
(seems Wikipedia is convinced that Battles have had a variable-pitch prop, so I'd ask people to shed some light on this matter)

The requirements of the Battle were pretty much the same as a civilian passenger plane in terms of speed range, but different from that of a fighter.

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I'd venture to say that a 2-pitch prop, as fitted not just on Battle but also on many other British bombers, was a better deal vs. a fixed-pitch prop, as fitted on 1st Hurricanes and Spitfires. That were still very useful fighters even with such a prop.

tomo pauk said:

I'm not quite following you there...
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Sorry typing too quickly, I meant single engine fighters. If the Battle had a fixed pitch prop it would have to be so fine to get it off the ground it wouldn't have got far.

tomo pauk said:

Air ministry can buy a batch of Hurricanes and/or Spitfires with a 2-pitch prop well before ww2 starts. Just like they bought Battles and Blenheims with 2-pitch prop.
(seems Wikipedia is convinced that Battles have had a variable-pitch prop, so I'd ask people to shed some light on this matter). I'd venture to say that a 2-pitch prop, as fitted not just on Battle but also on many other British bombers, was a better deal vs. a fixed-pitch prop, as fitted on 1st Hurricanes and Spitfires. That were still very useful fighters even with such a prop.
.

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But why? Without a war you don't need them to train pilots but the Blenheims and Battles couldn't get off the ground. I agree, but without a war you don't need them, as soon as war was declared they started to be fitted, same for 100 octane fuel, armour protection and self sealing tanks.

pbehn said:

Sorry typing too quickly, I meant single engine fighters. If the Battle had a fixed pitch prop it would have to be so fine to get it off the ground it wouldn't have got far.

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I haven't suggested fitting a fixed-pitch prop on Battle.

But why? Without a war you don't need them to train pilots but the Blenheims and Battles couldn't get off the ground.

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My English is failing me here.

I agree, but without a war you don't need them, as soon as war was declared they started to be fitted, same for 100 octane fuel, armour protection and self sealing tanks.

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It does not go that way.
You start pouring 100 oct fuel in the tanks of your aircraft when the fuel is available in good quantities and on reasonable price (and when the engine can put it in a good use), not when a war starts. Armor protection predates ww2 by several years.
Planning to install armor and/or self-sealing tanks when war starts is bad planing - either you have them and install them, or not.

tomo pauk said:

1. I haven't suggested fitting a fixed-pitch prop on Battle.

2. My English is failing me here.

3 It does not go that way.
You start pouring 100 oct fuel in the tanks of your aircraft when the fuel is available in good quantities and on reasonable price (and when the engine can put it in a good use), not when a war starts. Armor protection predates ww2 by several years.
Planning to install armor and/or self-sealing tanks when war starts is bad planing - either you have them and install them, or not.

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I edited your post just with numbers for understanding in the reply

1. was just saying it had to have a variable pitch prop, it just wouldn't work without one.
2 Your English is fine, my point was that without variable pitch props the RAF didn't have a bomber force for an air display let alone a war, but it did have fighters that could get off the ground. There were all sorts of things that possibly could have been done to the many fighters and bombers produced between 1918 and 1939 but weren't, simply because there wasn't a war to make it a necessity. Similarly if the war hadn't come when it did RR and Napier may have sorted the Vulture and Sabre and Hawkers may have sorted the Typhoon/Tornado sooner without the distractions of the war, or just a short time later all would have been centred on jets. It was the declaration of war that changed things.

3 The need for armour and self sealing tanks was seen as soon as combat was started, you don't notice it in peacetime war games because you didn't actually fire live ammunition. Use of 100 octane fuel is a story as involved as the development of the Merlin itself. It was more expensive and caused more engine wear due to the increased power. Why advise your enemy that you are using it in France when a plane is captured? Standardising what was "100 Octane" was an issue. It is one of the strange quirks of history that Henry Tizard of the Tizard committee was one of the people involved in the development of "Octane ratings"