Engine choices for P-51 mustang ?

[EwenS]

The Merlins were being manufactured in England and at the time, there was a real concern wether England might be next to fall under Germany's onslaught.

Nice to know that you consider the rest of the United Kingdom of Great Britain and Northern Ireland was safe from Hitler's predations!

The first German air raid on Britain on 16 Oct 1939 targeted RN ships in the Firth of Forth. Spitfires from 602 (City of Glasgow) and 603 (City of Edinburgh squadrons, based at Drem & Turnhouse respectively, were scrambled and succeeded in bringing down 2 German aircraft.

Rolls Royce had a shadow factory at Hillington, on the outskirts of Glasgow (in Scotland) from 1937, it completed its first Merlin engine about two weeks before the outbreak of WW2. It went on to produce about 14% of all Merlins produced worldwide as well as Griffons.

 

[GrauGeist]

Nice to know that you consider the rest of the United Kingdom of Great Britain and Northern Ireland was safe from Hitler's predations!

The first German air raid on Britain on 16 Oct 1939 targeted RN ships in the Firth of Forth. Spitfires from 602 (City of Glasgow) and 603 (City of Edinburgh squadrons, based at Drem & Turnhouse respectively, were scrambled and succeeded in bringing down 2 German aircraft.

Rolls Royce had a shadow factory at Hillington, on the outskirts of Glasgow (in Scotland) from 1937, it completed its first Merlin engine about two weeks before the outbreak of WW2. It went on to produce about 14% of all Merlins produced worldwide as well as Griffons.

Well, we knew for sure where England stood, but you had to keep an eye on those Irish (my Scottish ancestry *may or may not* have influenced my observation)

 

[PAT303]

When the BPC approached North American about manufacturing P-40's under license, it was a whole different world in Europe.
The Merlins were being manufactured in England and at the time, there was a real concern wether England might be next to fall under Germany's onslaught.

North American drew up a design using what was available, tried and proven. The V-1710 was a solid performing engine and was, in my opinion, the right choice.

We can look back and ponder what-ifs, but at the time, no one knew that there would be a need for long-range escorts battling at 35,000 feet and the early Allison powered Mustangs were also excellent performers at lower altitudes (including the A-36).

Lets be honest, without the Merlin the Mustang would just be another fighter but with it it became a legend. The Allison engined models were great aircraft but so were all the other low altitude planes, it's above 20,000ft were the men were seperated from the boys and where the air war ultimately progressed.

 

[GrauGeist]

Lets be honest, without the Merlin the Mustang would just be another fighter but with it it became a legend. The Allison engined models were great aircraft but so were all the other low altitude planes, it's above 20,000ft were the men were seperated from the boys and where the air war ultimately progressed.

Did they know that in 1940?

 

[drgondog]

The way i would have done it there would be NO aillson or merlin versions just sabres .

The problem with your view is that no magic wand existed to make your vision work. Neither re-design or priority access for Sabre or Griffon had the change been feasible. Further, neither were in position to produce for NAA. In other words, reognize that some really smart people - particularly NAA that designed the Mustang WITHOUT the constraints of Materiel Command burocracy dictat Specification, continued to improve on the performance .

The one time that NAA was Forced to make an engine change was when MC made the P-82 switch from Merlin to Allison ost WWII.

 

[PAT303]

Did they know that in 1940?

Well during the BoB Spit's and 109's were fighting all the way up too 30,000ft and over so I'd say yes. http://www.wwiiaircraftperformance.org/74-morrison-2nov40.jpg http://www.wwiiaircraftperformance.org/74-stephen-30nov40.jpg

 

[buffnut453]

Well during the BoB Spit's and 109's were fighting all the way up too 30,000ft and over so I'd say yes. http://www.wwiiaircraftperformance.org/74-morrison-2nov40.jpg http://www.wwiiaircraftperformance.org/74-stephen-30nov40.jpg

You're right to an extent...however, from the US perspective there wasn't an identified need at that time for a fighter that could operate at those altitudes and at long range, at least not in 1940. Even in 1942, the USAAF was hoping daylight precision bombing with unescorted B-17s and B-24s would do the trick.

 

[SaparotRob]

"The bomber will always get through."

 

[drgondog]

You're right to an extent...however, from the US perspective there wasn't an identified need at that time for a fighter that could operate at those altitudes and at long range, at least not in 1940. Even in 1942, the USAAF was hoping daylight precision bombing with unescorted B-17s and B-24s would do the trick.

In fairness, in 1939 Arnold was aware that unescorted bomber concept was trashed in Spanish Civil War and personally changed the ranked priorities of the Emmons Board. The "4. Long Range Fighter with 1500 mi Range" was moved by him to 1. While Arnold took personal responsibility for AAF not buying the Mustang sooner, in fairness the critical path to P-51B combat ops was Packard's gestation issues with 1650-3. That said, Col, then MG Oliver Echols was singularly responsible for rejecting the NA-73 when it was abundantly clear that XP-46 was a total failure - and NA-73 was superior AND in production at same time XP-46 first flew. Echols was forced by Gen Fairchild and HQ-Planning and Requirements to buy the A-36, then run over again when he tried to stop NA-99 (P-51A) and NA-102 (P-51B) from being let, favoring shutting down Mustang and diverting production capacity to B-25s. I haven't found documents to support Arnold's command infuence - but certain that it existed, and equally certain that he was impressed by the work efforts at R-R in June 1942 to instqll the Merlin.

"Hoping" that long range escort would do the trick in 1942 was a good way to sum it up. That said, the 8th AF TO&E called for lng range escort (P-38F) FGs in original plan. From that point, when the P-38s were removed to Africa and Spitfire/P-47 replaced them, the "hope' quotient went up.It became abundently clear even to Eaker and Spaatz that daylight stategic bombing entered the Crisis Zone from BLitz Week in July 1943 through Tidal Wave August 1.

Eaker's plea in June 1943 for long range escort was heard and jolted several actions. First Arnold diverted deployment of 55th and 20th FG (P-38) to ETO immediately, arriving in August. Second, the pressure on increasing intenal fuel for P-51B, P-47D and P-38J ratched up (MG Giles), and finally Col Bradley finally unbloked Echols resistance to P-51B at Materiel Command.

 

[Shortround6]

The way i would have done it there would be NO aillson or merlin versions just sabres .

Trouble is you need a Tardis (time machine).

The first flight of the first Typhoon prototype, P5212, made by Hawker's Chief test Pilot Philip Lucas from Langley, was delayed until 24 February 1940 because of the problems with the development of the Sabre engine.

The Purchasing Commission approved the resulting detailed design drawings, signing the commencement of the Mustang project on 4 May 1940, firmly ordering 320 on 29 May 1940. Prior to this, North American only had a draft letter for an order of 320 aircraft.

Talks had started earlier, Jan 1940.

If you are getting information from Wiki, be very, very careful. Somebody editing Wiki really hates the Merlin engine.
"The first Sabre engines were ready for testing in January 1938, although they were limited to 1,350 hp (1,000 kW). By March, they were passing tests at 2,050 hp (1,500 kW) and by June 1940, when the Sabre passed the Air Ministry's 100-hour test, the first production versions were delivering 2,200 hp (1,640 kW) from their 2,238 cubic inch (37 litre) displacements.[7]​ By the end of the year, they were producing 2,400 hp (1,800 kW). The contemporary 1940 Rolls-Royce Merlin II was generating just over 1,000 hp (750 kW) from a 1,647 cubic inch (27 litre) displacement."

In reverse, in 1940 the Merlin II had been out of production for several years. The Merlin III had been approved for around 1300hp using 100 octane fuel. The First Merlin XII's were delivered to an RAF squadron in July/Aug of 1940, The Merlin X had been in production since 1939 and the first Merlin XX engines were delivered to a Squadron in Sept 1940.
Why the writer is ignoring engines in service and going into service with an engine that passed it's type test is disinformation.

In the Summer of 1940 the Americans and British were ordering P-40D & E fighters with Allison -39 engines that were rated at 1150hp, they wouldn't show up until the summer of 1941 and that is a reason you cannot compare engines that are in development with engines that were going into service.

First Typhoon prototype was lost when it's engine seized.
Early production Sabre Is were being pulled at 25 hours of use for major inspection.
The Sabre II was introduced into production in Jan 1941 but since testing has to be done, first installation in a Typhoon was June of 1941, At this time major inspections were changed to 50 hour intervals.

However, from "Old Machine Press"
"With production engines in production airframes, Sabre reliability issues were soon encountered. After running for a few hours, sometimes not even passing initial tests, Sabre engines began to experience excessive oil consumption and sleeve-valves cracking, breaking, seizing or otherwise failing. Examinations of numerous engines found sleeves distorted or damaged."

At this point NA was gearing up Mustang production, 2 in Aug, 6 in Sept, 25 in Oct, 37 in Nov, 68 in Dec.

You can't stick a Sabre in a Mustang airframe. You could build an airframe to hold the Sabre using some of the Mustang Ideas.
You are also going to be late with airplanes showing up, your airframes are going to be more expensive (heavier) and the Sabre engines are going to be around 4 times as expensive per engine at a minimum. (sleeve valve engines were roughly 2 times more expensive than poppet valve engines per Horsepower at best, and since you want an engine with twice the power of the Allison?)

 

[Shortround6]

You're right to an extent...however, from the US perspective there wasn't an identified need at that time for a fighter that could operate at those altitudes and at long range, at least not in 1940. Even in 1942, the USAAF was hoping daylight precision bombing with unescorted B-17s and B-24s would do the trick.

Yes, no, maybe.

In 1940 the US was building the P-38, early versions had 400 US gallons of fuel in non-self sealing tanks. When self sealing tanks were fitted fuel capacity fell to 300 US gallons and dropped considerably.

March of 1939 had seen 13 YP-43 fighters ordered but they don't show up until Sept 1940. By which time they are no longer wanted, even the 80 P-44s with turbo R-2180 engines are not longer wanted (ordered Sept 1939). Army orders P-47Bs by the hundreds but the engines and airframes are not going to be ready so Republic is given an order for 54 P-43s to give Republic something to do, (keep work force together and enlarge it)

YP-43s had 200 gallons of internal fuel in integral tanks and that didn't work so well.

There were a number of fighters in the design stage in 1940 that were supposed to fight at high altitudes. Like the XP-50 and the XP-49. However most of the experimental engines fell by wayside stopped the planed aircraft. The Bombers managed to outplace the development of the fighters with the B-17 and B-24 and it took a while for the fighters to catch up.
That is were the high altitude part came in. They were certainly planning on it.
The Range part gets a bit iffy. The fighters were not going to fly as far the bombers even without self-sealing tanks.
Now at what point did the US decide to fly the bombers in the low 20,000ft range?
If they had kept them high (30,000ft) they might not have needed escorts in 1943/43.
However the oxygen systems, crew heating systems and other systems turned out to be unable to support multi hour flights at 30,000ft and when the operating altitudes of the bombers came down the need for escorts went way up. Which caused a scramble to fit aux tanks to the existing high altitude fighters to cover the gap.
None of the proposed "escort" fighter ever made it past prototype stage and they were all late.

A few people in the US may have seen a need for a high altitude escort fighter in 1940, but unless somebody like NA pulled a rabbit out of hat anything they were thinking off in 1940 would not be in production until 1943 (you needed new engines to go with the new airframes) even if everything went well. It didn't and most of the P-51 and up fighters flopped.
That leaves the bombers on their own while people scrambled to modify the P-51 and earlier fighters into escort fighters. Putting drop tanks on the P-38 and P-47 helped but until the internal fuel was expanded the P-38 and P-47 would never come close to having enough range.
Now go back to 1940 and look at the P-38 and the P-47 and look at the engines they were planning on using. Now look at the engines they were using in the fall/winter of 1943/44 to lug the extra fuel. They never did an escort fighter into service using the engines that they had available in 1940. They got escort fighters into service with improved engines that used improved fuel.

 

[GrauGeist]

Plus, the Sabre was a large engine:
46 inches high by 40 inches wide, where the V-1710 was 37 inches high by 29 inches wide.

In order to stuff a Sabre into a P-51 airframe, you'd have to enlarge the cowl considerably, ruining the P-51's aerodynamics in the process.

It would be easier to fit a Sabre into a P-47 - the R-2800 was 52 inches wide.

 

[Deleted member 68059]

What you really want requires "alternative history" levels of change.

1) RR invite Allison engineers to England to help fix the useless Merlin Mk1 engine ramp head
2) Allison give them the pent-roof chamber and roller-rockers they`ve designed
3) RR pass on test data on high pressure cooling to Allison
4) A collaborative partnership emerges
5) RR, grateful, and Allison receptive - RR call Allison in 1940 to ask if they want "in" on the new 2 stage project

I think you can imagine the rest, this is totally fanciful and utterly against the corporate attitudes of the time
and would never ever have happened. But....

 

[Thumpalumpacus]

You are going to wind up with a lot more dihedral on wings after you land than when you took off

Well, you have to break-in any piece of machinery, why would high-performance fighters be any different?

 

[Thumpalumpacus]

In fairness, in 1939 Arnold was aware that unescorted bomber concept was trashed in Spanish Civil War and personally changed the ranked priorities of the Emmons Board. The "4. Long Range Fighter with 1500 mi Range" was moved by him to 1. While Arnold took personal responsibility for AAF not buying the Mustang sooner, in fairness the critical path to P-51B combat ops was Packard's gestation issues with 1650-3. That said, Col, then MG Oliver Echols was singularly responsible for rejecting the NA-73 when it was abundantly clear that XP-46 was a total failure - and NA-73 was superior AND in production at same time XP-46 first flew. Echols was forced by Gen Fairchild and HQ-Planning and Requirements to buy the A-36, then run over again when he tried to stop NA-99 (P-51A) and NA-102 (P-51B) from being let, favoring shutting down Mustang and diverting production capacity to B-25s. I haven't found documents to support Arnold's command infuence - but certain that it existed, and equally certain that he was impressed by the work efforts at R-R in June 1942 to instqll the Merlin.

"Hoping" that long range escort would do the trick in 1942 was a good way to sum it up. That said, the 8th AF TO&E called for lng range escort (P-38F) FGs in original plan. From that point, when the P-38s were removed to Africa and Spitfire/P-47 replaced them, the "hope' quotient went up.It became abundently clear even to Eaker and Spaatz that daylight stategic bombing entered the Crisis Zone from BLitz Week in July 1943 through Tidal Wave August 1.

Eaker's plea in June 1943 for long range escort was heard and jolted several actions. First Arnold diverted deployment of 55th and 20th FG (P-38) to ETO immediately, arriving in August. Second, the pressure on increasing intenal fuel for P-51B, P-47D and P-38J ratched up (MG Giles), and finally Col Bradley finally unbloked Echols resistance to P-51B at Materiel Command.

"Jesus Christ, give us fighters" is the quote that springs to mind from this post.

 

[drgondog]

What you really want requires "alternative history" levels of change.

1) RR invite Allison engineers to England to help fix the useless Merlin Mk1 engine ramp head
2) Allison give them the pent-roof chamber and roller-rockers they`ve designed
3) RR pass on test data on high pressure cooling to Allison
4) A collaborative partnership emerges
5) RR, grateful, and Allison receptive - RR call Allison in 1940 to ask if they want "in" on the new 2 stage project

I think you can imagine the rest, this is totally fanciful and utterly against the corporate attitudes of the time
and would never ever have happened. But....

And still, R-R and Packard strke a deal because Allison still doesn't have capacity in R&D to accelerate implementyation of the improved Allison V-1650-1& -3 as the bull headed Echols is still pushing the Allison V-1710 with single stage to supply Army needs.

 

[buffnut453]

In fairness, in 1939 Arnold was aware that unescorted bomber concept was trashed in Spanish Civil War and personally changed the ranked priorities of the Emmons Board. The "4. Long Range Fighter with 1500 mi Range" was moved by him to 1. While Arnold took personal responsibility for AAF not buying the Mustang sooner, in fairness the critical path to P-51B combat ops was Packard's gestation issues with 1650-3. That said, Col, then MG Oliver Echols was singularly responsible for rejecting the NA-73 when it was abundantly clear that XP-46 was a total failure - and NA-73 was superior AND in production at same time XP-46 first flew. Echols was forced by Gen Fairchild and HQ-Planning and Requirements to buy the A-36, then run over again when he tried to stop NA-99 (P-51A) and NA-102 (P-51B) from being let, favoring shutting down Mustang and diverting production capacity to B-25s. I haven't found documents to support Arnold's command infuence - but certain that it existed, and equally certain that he was impressed by the work efforts at R-R in June 1942 to instqll the Merlin.

"Hoping" that long range escort would do the trick in 1942 was a good way to sum it up. That said, the 8th AF TO&E called for lng range escort (P-38F) FGs in original plan. From that point, when the P-38s were removed to Africa and Spitfire/P-47 replaced them, the "hope' quotient went up.It became abundently clear even to Eaker and Spaatz that daylight stategic bombing entered the Crisis Zone from BLitz Week in July 1943 through Tidal Wave August 1.

Eaker's plea in June 1943 for long range escort was heard and jolted several actions. First Arnold diverted deployment of 55th and 20th FG (P-38) to ETO immediately, arriving in August. Second, the pressure on increasing intenal fuel for P-51B, P-47D and P-38J ratched up (MG Giles), and finally Col Bradley finally unbloked Echols resistance to P-51B at Materiel Command.

As always, things were more complicated than my rather glib comment. The first flight of the XP-38 on 27 Jan 1939 preceded Arnold's decision, so clearly there were moves afoot. The XP-38 was followed by production of 15 YP-38s but progress was incredibly slow despite Arnold's prioritization. The first YP-38 only flew in Sep 1940 and last was delivered in Jun 1941, with the first operationally viable production airframe (a P-38E) rolling off the production line in October 1941, with several months to follow before a viable force was in existence.

In reality, the P-38 arrived on the scene barely in time to support US entry into combat theatres. Obviously, USAAF planners made use of the platform...but I sense this wasn't the most thought-through of procurements, and that a lot of luck was involved with the P-38 being ready in time.

 

[Thumpalumpacus]

In reality, the P-38 arrived on the scene barely in time to support US entry into combat theatres. Obviously, USAAF planners made use of the platform...but I sense this wasn't the most thought-through of procurements, and that a lot of luck was involved with the P-38 being ready in time.

... and they used the best available engine they had at the time for the mission profile that dictated the design. It bears noting that for a high-speed interceptor with good climb, even Johnson decided that two 1710s would be needed.

As it turned out, the platform was useful in so many other roles that it stayed in production throughout the war, but whether that was for engines, airframe, or the combination of the two could probably benefit from some disambiguation.

My own opinion: properly blown, it was damned good. Raw P/W ratio vs Merlin, well, the Merlin has the edge, I think, as shown by P-40s with the two different engines. And of course the altitude thing.

I think it took some time for American engineers to realize that the Merlin was a superlative powerplant -- and there's little shame in that, considering supply-chains and such. You dance with who you brung, better late than never, yadda-yadda.

 

[drgondog]

As always, things were more complicated than my rather glib comment. The first flight of the XP-38 on 27 Jan 1939 preceded Arnold's decision, so clearly there were moves afoot. The XP-38 was followed by production of 15 YP-38s but progress was incredibly slow despite Arnold's prioritization. The first YP-38 only flew in Sep 1940 and last was delivered in Jun 1941, with the first operationally viable production airframe (a P-38E) rolling off the production line in October 1941, with several months to follow before a viable force was in existence.

In reality, the P-38 arrived on the scene barely in time to support US entry into combat theatres. Obviously, USAAF planners made use of the platform...but I sense this wasn't the most thought-through of procurements, and that a lot of luck was involved with the P-38 being ready in time.

Fair - but the Emmons Board set the R&D priorities and the desired fighter was to be Single engine with 1500 mi range. The P-38 was established via RFP as a 'T/E Interceptor', ditto the P-39, arising from CP38-608 and 609 respectively, The Emmons Board was fully aware that the envisioned P-39 with Turbosupercharging would have inadequate range. Lt. Ben Kelsey project managed both Circular Proposal RFPs and always considered the XP-39 to be the 'smaller solution' then became MC Project Manager for P-38, (Price for P-39), the Kelsey took over Fighter Projects in 1940-1941.

To your point regarding 'P-38 arrived on the scene barely in time'. I agree 100% and lay the fault tothe Wright Field practices and focus n 'can it fly', rather than 'what can it do' - the current split of Edwards AFB vs Eglin AFB reflects AAF finally awakening to the issue as otherwise fine aircrad=ft such as P-39, P-40, P-47 were dispatched to combat ops with a myriad of operational issues that required Dept level mod in-Theatre.

The Brits KNEW what they were doing, had received oversold/over optimistic versions of the Hawk 75, the P-400 and P-322, and were dtermined to nip the discovred issues in the bud with the NAA NA-73. They baked their own knowledge int the NAA/RAF secificificatio and test cycles for NA-73.

I have issues with Ben Kelsey and his post warwar remembrances of his personal contribution to NAA and the Mustang, but I give him this - he worked cleverly and tirelessly with Lockheed to improve the P-38 - incuding the most important project, namely provisioning the P-38E with external bomb rack (no resistance from AAC/AAF at MC) but unknown to higher command he also fo und a way to fund internal plumbing for the bomb racks and develop capability for external fuel tanks of far higher capacity thanin Army inventory for Ferry purposes. That said, Wright Field sucked at discovering potential operatioal problems and bridging fixes with the manufacturers.

Many changes, subtle and not so subtle, were made by the Boss - Gen Hap Arnold,beginning early 1942 and escalating into mid 1943. I devoted a lot of ink on this subject.

 

[Shortround6]

At the 1939 fighter trials there were (or planed to be) 3 fighters with turbo charged Allison's. The XP-38 didn't make it in time and neither did the XP-39.
Also on the no show list was the YP-37. The turbo XP-37 was in existence but I don't know of it made it for a 4th but obsolete turbo charged plane.
Present was a turbo charged Seversky fighter, predecessor to the XP-41 and P-43.
Also present was a Seversky using a two stage mechanically supercharged R-1830 engine that would be developed into the engine used in Grumman F4F.
Also present was a Curtiss 75 fighter using the same two stage R-1830 engine.

This was the competition that was won by the XP-40.

There was obviously a very strong interest in high altitude planes. However the practical experience was that weren't ready to be introduced into squadron service. Of the 13 turbocharged YP-37 that started showing up in March of 1939 the airframe that had the most hours before retirement to airframe school was 212 hours. Many of them had much less.

P&W did a fair amount of tweaking to the two stage supercharger and got it to make more power higher up than the test engines but the version used in the first F4Fs also needed further refinement.

The US fighters did not have the range to accompany the bombers in 1939-40 but US fighters had 50-100% more range than British, German, French, Italian and Russian single seat fighters did (at least pre self sealing fuel tanks).

Please remember that fuel was problem for developing long range aircraft. Higher octane fuel could support higher compression ratios in the engine and offer better fuel economy.
The Allison at cruise settings used around 8% (?) less fuel than the Merlin for the same HP per hour as one example. And this was with both engines using 100 octane fuel.
The XP-58 was started in 1940 as an escort fighter using two Continental engines but they were considered not powerful enough and the XP-58s journey through the land of failed/canceled engines started and ended up with 600sq ft wing, twin V-3420 engines and an empty weight of over 31,500lbs.
Be very careful of what you asked for in 1940 for an escort fighter