V-1650 powered P-40's

[tomo pauk]

Ah, guys, Packard delivered about 45 Merlins in ALL of 1941. While there may have been a few available for flight testing in a few air frames with 2/3 of production going to the British there would have been darn few American P-51s with Merlins before 1942. There were also only 138 P-51s accepted in 1941 compared to 2,246 P-40s and in 1942 the numbers went 634 P-51s to 3,854 P-40s. A big jumps in Mustang production came with the opening of the Dallas Factory and moving a lot of B-25 production to Kansas City.

It was also 'darn few' P-51s of any kinds before 1942, and none was in USAAC squadrons. None was also in 1942 (apart the A-36) - the 1st combat action of an USAAC P-51 unit was on April 9th 1943. The importance on the battlefield of the historical P-51, compared with other US fighters prior 1944, is only token.

A Merlin V-1650-1 wold have been better than an Allison powered one overall ( but not by much at certain altitudes depending which Allison) but it would not have been available in any numbers in 1942 or early 1943 and would only have been available at the cost of the P-40F which at the time was the second best Army altitude fighter available in any quantity next to the P-38. In 1942 early 1943 there were nowhere near enough P-38s to go around. Over 3600 P-40F-s were built along with 700 'L's. Granted near the end the V-1650-1 was competing for production with the V-1650-3 but allocation for raw materials and finished sub-contractor parts have to be months and months before a US plane ever saw combat.

P-51s with Allison engines amounted to 1080 pcs, + 500 in A-36 guise - that makes 1580 planes. Even if the input of 1650-1s remain the same, that would still leave 2720 of such engines for the P-40s production. Plus, of course, the V-1710s that are no more needed for P-51/A-36.
With Merlinized Mustang in late 1942 for USAAC (with Curtiss building a P-40-based dive bomber, so USAAC can have funds), that means a 400-mph single engined fighter - not yet another 370 mph one. Plus it has 20% more fuel internally to boost the range (along with far lower drag).
As for material part allocations, with a prototype P-51/Merlin flying early in 1941, there is plenty of time to allocate those. And allocations are already made both for P-51 airframe and V-1650.

 

[gjs238]

Ah, guys, Packard delivered about 45 Merlins in ALL of 1941. While there may have been a few available for flight testing in a few air frames with 2/3 of production going to the British there would have been darn few American P-51s with Merlins before 1942. There were also only 138 P-51s accepted in 1941 compared to 2,246 P-40s and in 1942 the numbers went 634 P-51s to 3,854 P-40s. A big jumps in Mustang production came with the opening of the Dallas Factory and moving a lot of B-25 production to Kansas City.

Which brings up another issue...
Should Curtiss have begun transitioning to manufacturing P-51's?

 

[wuzak]

By the time Packard was building enough V-1650-1s to consider putting them in P-51s wasn't the Merlin 60 being tested/put into production?

Was it better to wait for an even better engine than put in an interim engine?

 

[wuzak]

Which brings up another issue...
Should Curtiss have begun transitioning to manufacturing P-51's?

I believe they made P-47s, but probably not at the expense of P-40s.

I have also read that their P-47s were built with substandard quality. Which would be a concern for the P-51 since its laminar flow wing was very sensative to damage/imperfections.

 

[Shortround6]

One reason for the P-40R was the LACK of spare Merlin engines (and parts) allocated by US planners, there is some controversy about the number of "R"S but the British are supposed to have given the US over 400 Merlins (as many as 600?) in sort of a reverse lend lease to Keep Merlin powered P-40s flying in the MTO. either as direct engine swaps or as a source of spare parts. When planning engine production it was common to allocate 20-50% more engines than air frames as "spares". 20% "spares" often lead to shortages.
As for Curtiss switching over to P-51 production. the Curtiss contract for P-60s was canceled in Jan of 1942 and replace with a contract for P-47s. It took until Dec of 1942 for the first Curtiss P-47 to fly. I highly doubt that they were rolling them at the rate of dozens per week the first few months either. Not only did it take EVERY aircraft moths to reach anything like full production after the first one or two went out the door but Curtiss only managed to build 354 (?) P-47s in 15-16 months.

How many P-40s are you willing to give up in the 6 months to a year it takes Curtiss to build their first P-51?

The P-40K used the an engine rated at 1325hp for take-off even if it was not quite the same as the one in the A-36 . October 28, 1941 is when the first order for 600 is placed but the first one doesn't fly until August of 1942 by which time a total of 1300 are on order. Many are lend leased to China and while some go to England the majority of the USAAF ones go to the South Pacific and Asia. I hope you see what I mean about allocations. Ordered in October 1941, first production in August and a Plane in Buffalo New York is a long, long way from combat in Asia. Even with 1325hp for take-off and a WER rating of 1580hp at 2500ft the official bomb load of the P-40 K is the same as the P-40E.

Once again I will call to attention the fact that an Allison powered P-51 could hold it's own against either Bf 109s or or FW 190s better than a Merlin powered P-40 could and much better than a an Allison powered P-40 could. While the V-160-1 powered P-51 would be even better it reduces the TOTAL number of fighters judged capable of fighting German aircraft in the planners minds of the time. The P-40E being judged NOT capable of performing the air to air duty. I know that they did score many successes but it is also true that in many operations they were given "top" cover by other fighter types. I believe it was thought that the P-40F wouldn't need other fighters to give it top cover. This "plan" may have been thrown a curve with better German aircraft becoming available.

 

[Ratsel]

" I believe it was thought that the P-40F wouldn't need other fighters to give it top cover. This "plan" may have been thrown a curve with better German aircraft becoming available. "

The Palm Sunday massacre were P-40F's from behind with Spitfire top cover. Classic pinch. The JU52's, -109's had nowhere to go. Element of suprise won that one imo.

 

[tomo pauk]

By the time Packard was building enough V-1650-1s to consider putting them in P-51s wasn't the Merlin 60 being tested/put into production?

Was it better to wait for an even better engine than put in an interim engine?

Merlin 60 was indeed in production, but not by Packard; the 1st P-40 with Merlin was flown in June 1941 with British engine on board. Too bad NAA didn't made the similar experiment in summer of 1941.
As for waiting, that was not a 2, or 3 months of waiting, but something along 20 months - 1st production Mustang occurred before 1942, 1st production P-51Bs are 'being readied for shipment to UK' in Aug 1943. NAA was faster in building airframes than Packard was to build two-stage Merlins ( 534 P-51B airframes vs. 173 merlin received by July 1943), not the case for single-stage variant (13000 pcs produced in 1942 and 1st seven months of 1943 - some 4000 of those was to be for the USA?).

...
The P-40K used the an engine rated at 1325hp for take-off even if it was not quite the same as the one in the A-36 . October 28, 1941 is when the first order for 600 is placed but the first one doesn't fly until August of 1942 by which time a total of 1300 are on order. Many are lend leased to China and while some go to England the majority of the USAAF ones go to the South Pacific and Asia. I hope you see what I mean about allocations. Ordered in October 1941, first production in August and a Plane in Buffalo New York is a long, long way from combat in Asia. Even with 1325hp for take-off and a WER rating of 1580hp at 2500ft the official bomb load of the P-40 K is the same as the P-40E.

I agree that allocations of 'full' planes needed to be made prior the deployment, same holds true for all the hardware. P-40 P-51 alike.

Once again I will call to attention the fact that an Allison powered P-51 could hold it's own against either Bf 109s or or FW 190s better than a Merlin powered P-40 could and much better than a an Allison powered P-40 could. While the V-160-1 powered P-51 would be even better it reduces the TOTAL number of fighters judged capable of fighting German aircraft in the planners minds of the time. The P-40E being judged NOT capable of performing the air to air duty. I know that they did score many successes but it is also true that in many operations they were given "top" cover by other fighter types. I believe it was thought that the P-40F wouldn't need other fighters to give it top cover. This "plan" may have been thrown a curve with better German aircraft becoming available.

In this case of 'early Merlinized P-51' scenario, P-40F still gets built, though in less examples; the balance receives V-1710s.
As for the 'planers' really believing that a 370-mph plane is a viable option to fight 400-mph planes (while a 360 mph plane is not), that statement would require some good data confirming such a believe. RAF was not very convinced in that anyway, so they went for a 400 mph plane of their own, in service in the very 1942.

 

[Shortround6]

In this case of 'early Merlinized P-51' scenario, P-40F still gets built, though in less examples; the balance receives V-1710s.
As for the 'planers' really believing that a 370-mph plane is a viable option to fight 400-mph planes (while a 360 mph plane is not), that statement would require some good data confirming such a believe. RAF was not very convinced in that anyway, so they went for a 400 mph plane of their own, in service in the very 1942.

If you are a time traveler and know exactly when not only your own planes and engines will be be made and upgraded (WER settings) but ALSO know when the enemy's planes and engines will be be made and upgraded then it is quite possible to juggle things around. Without that type of knowledge trying to predict exactly what type of aircraft would be needed 9-15months in future and in what numbers gets much more difficult.

As for the 370mph vs 360mph P-40s that isn't quite the comparison they were thinking about. at 20,000ft the Merlin powered P-40 was over 30mph faster than the Allison powered "E" and at 25,000ft the difference was over 50mph. The "operational" ceiling (altitude at which climb was still 1000ft per min) was also going to favor the Merlin powered P-40 by 4-6,000ft. Now I will admit that even the P-40F was maxed out somewhere between 20,000 and 25,000ft which gives the advantage to the 109 Fs and Gs but Allison powered P-40s would have no hope against them without another type of fighter covering them. The P-40F was not their equal but at least had a chance at the 15,000-22,500 altitudes.
Allison Powered Mustangs remained useful much longer, in British service 5 squadrons were still in use on D-Day with MK Is and IAs. A squadron with MK IIs was still flying recon missions in April of 1945 in Europe.
What "mix" of Allison and Merlin powered P-40s and Mustangs gives you the Largest numbers of useful fighters in a European context in 1942-43?

 

[tomo pauk]

If you are a time traveler and know exactly when not only your own planes and engines will be be made and upgraded (WER settings) but ALSO know when the enemy's planes and engines will be be made and upgraded then it is quite possible to juggle things around. Without that type of knowledge trying to predict exactly what type of aircraft would be needed 9-15months in future and in what numbers gets much more difficult.

There is no need for a time traveler here.
In early 1941 people that mattered in the USA knew for a fact:
-P-51 is faster than P-40, on same engine similar armament; it also has 20% more fuel internally = better combat ferry range
-a Merlin XX that is going to be produced by Packard develops same HP at 6-7000 ft higher altitude, when compared with V-1710 to be produced in 1941-42 (F series)

Those two (airframe and engine) put together seem like a winner to me. Even without gambling on where or if the WER is to be allowed for.

As for the 370mph vs 360mph P-40s that isn't quite the comparison they were thinking about. at 20,000ft the Merlin powered P-40 was over 30mph faster than the Allison powered "E" and at 25,000ft the difference was over 50mph. The "operational" ceiling (altitude at which climb was still 1000ft per min) was also going to favor the Merlin powered P-40 by 4-6,000ft. Now I will admit that even the P-40F was maxed out somewhere between 20,000 and 25,000ft which gives the advantage to the 109 Fs and Gs but Allison powered P-40s would have no hope against them without another type of fighter covering them. The P-40F was not their equal but at least had a chance at the 15,000-22,500 altitudes.
Allison Powered Mustangs remained useful much longer, in British service 5 squadrons were still in use on D-Day with MK Is and IAs. A squadron with MK IIs was still flying recon missions in April of 1945 in Europe.
What "mix" of Allison and Merlin powered P-40s and Mustangs gives you the Largest numbers of useful fighters in a European context in 1942-43?

We could 1st declare what range of performance (speed 1stly; neither P-40 nor P-51 were that good climbers compared with main adversaries or concurents). For Europe I reckon you mean ETO (german-occupied part of France in 1940-42 and northern from that)?
In 1942 the main adversaries were Fw-190A (A-3?) and Bf-109F-4 - both very much capable to do 400 mph @ 20K, and very good climbers. The P-40F can do circa 360 mph at same altitude (10 mph less than Spit V (w/ Merlin 45). Since Spit V was considered as outclassed vs. those adversaries at most altitudes (RAF hastily went for the 'interim' Spit IX), there is no point to consider P-40F as a viable fighter vs. German opposition. BTW, finding informations about P-40F operating from UK is pretty hard - can someone shed some light about that?
So I'd go for some 1600 pcs of P-51 with V-1650-1 (= all non-Merlin Mustang/P-51/A-36 airframes), as many of those to operate from UK as possible (rest of the engines can go for P-40).

 

[Shortround6]

Most P-40Fs went to North Africa, not Northern Europe but not the Pacific either, which is were the majority of the P-40Ks (next Allison powered model after the "E")went, which indicates to me that the planners were interested in the best altitude performance they could get at the time against the Germans. The Majority of the P-38s available were also being marshaled for the North Africa Invasion. The Transfer of the P-38s delayed P-38 escort of the Eighth Air Force bombers.

In summer/fall of 1941 when the production decisions were made the abilities of the 109F-4 and the 190A-3 were not as well known as later. In some factories the 190A-2 only preceded the P-40F into production by 3-4 months.

Without a major re-adjustment of the P-51 production schedule you aren't going to get the majority of your 1600 planes until late 1942 or early 1943, if then. Getting them into service would take months longer. The First 620 planes are to British contracts placed on may 29th 1940 (320 planes) and Sept 1940 (300) planes. in all of 1941 there are 128 Mustangs built and 68 of them are in December. Remember that Packard only built 45 engines in all of 1941. Packard Merlins simply are not available for the first few hundred Mustangs unless you hold the British air frames at the factory until engines become available, first 320 may have been paid for cash and carry and not lend/lease which makes the US air force getting hold of them rather difficult. First Mustang reaches England in Oct, 1941. First Operational use isn't until May 10th 1942. This is a busy time for the Mustang. In the previous month (April 1942) the contract is placed for 500 A-36 dive bombers, perhaps at this point the contract could have substituted the Merlins? On May 29th 1942 the first flight of a P-51 (Mustang IA) with 4 20mm cannon takes place. the order for 150 was placed back in July of 1941, these are definitely lend lease aircraft and 57 stay with the US Forces. In June of 1942 another order is placed for 1200 P-51A aircraft, this contract is cut back to 310 aircraft in Dec 1942 with the remainder to become part of the P-51B order. The last of the 620 plane British order rolls out the door in in July of 1942, the same month a contract is placed for the conversion of two lend lease P-51s to XP-78 standard (XP51-B) with two stage Merlins. Work is started on the P-51 order. Sept of 1942 sees the first flight of the A-36, one month after the first order for 400 P-51Bs is placed, one month before the first British conversion flies and less than 3 months before the first North American XP-51B flies.

There is actually only a small window of time when there would be enough Packard built Merlin's available to make such a project worthwhile and when such a project would delay the introduction of the P-51B. Put that together with which Allisons were available when (or promised, there were several projects in the works for high altitude engines in late 1941). I would note that the final 310 Allison powered Mustangs got improved engines that cut the difference in altitude performance between the older Allison engines and the V-1650-1 about in half.

The fact that the Mustang has less drag than a P-40 also means it can climb better at the same weight because less power is going into forward flight, leaving more power for climb.

The US Government (AAC) did not allow WER ratings until Dec of 1942. What combat units did seems to have been a different story.

 

[tomo pauk]

Most P-40Fs went to North Africa, not Northern Europe but not the Pacific either, which is were the majority of the P-40Ks (next Allison powered model after the "E")went, which indicates to me that the planners were interested in the best altitude performance they could get at the time against the Germans. The Majority of the P-38s available were also being marshaled for the North Africa Invasion. The Transfer of the P-38s delayed P-38 escort of the Eighth Air Force bombers

.

So by 'European context' you mean MTO in this case - okay, we can consider a historical situation re. P-40F as 'almost none for ETO'.

In summer/fall of 1941 when the production decisions were made the abilities of the 109F-4 and the 190A-3 were not as well known as later. In some factories the 190A-2 only preceded the P-40F into production by 3-4 months.

We can take another approach as to what kind of threats USAAC is to expect from LW: in 1940 (or - even in 1939) it was known for fact that LW fields the 370 mph fighter. Should the USAAC brass expect that Germans will not move forward, to introduce a plane capable to do 400 mph within 18 months ( or -10 months from BoB it was) - in time P-40 with V-1650 is in service (or - make it a full year before P-40F)?

Without a major re-adjustment of the P-51 production schedule you aren't going to get the majority of your 1600 planes until late 1942 or early 1943, if then. Getting them into service would take months longer. The First 620 planes are to British contracts placed on may 29th 1940 (320 planes) and Sept 1940 (300) planes. in all of 1941 there are 128 Mustangs built and 68 of them are in December. Remember that Packard only built 45 engines in all of 1941. Packard Merlins simply are not available for the first few hundred Mustangs unless you hold the British air frames at the factory until engines become available, first 320 may have been paid for cash and carry and not lend/lease which makes the US air force getting hold of them rather difficult. First Mustang reaches England in Oct, 1941. First Operational use isn't until May 10th 1942. This is a busy time for the Mustang. In the previous month (April 1942) the contract is placed for 500 A-36 dive bombers, perhaps at this point the contract could have substituted the Merlins? On May 29th 1942 the first flight of a P-51 (Mustang IA) with 4 20mm cannon takes place. the order for 150 was placed back in July of 1941, these are definitely lend lease aircraft and 57 stay with the US Forces. In June of 1942 another order is placed for 1200 P-51A aircraft, this contract is cut back to 310 aircraft in Dec 1942 with the remainder to become part of the P-51B order. The last of the 620 plane British order rolls out the door in in July of 1942, the same month a contract is placed for the conversion of two lend lease P-51s to XP-78 standard (XP51-B) with two stage Merlins. Work is started on the P-51 order. Sept of 1942 sees the first flight of the A-36, one month after the first order for 400 P-51Bs is placed, one month before the first British conversion flies and less than 3 months before the first North American XP-51B flies.

Thanks for the insight about Mustang's historical time line.
What can (good or bad) happen for Mustang, with Brits supplying the NAA with a Merlin XX in late 1940? The engine is installed flown within 4-6 months, and brass both at RAF USAAC are satisfied, and both British contracts for Mustang are altered for V-1650 instead of V-1710. USAAC wants the plane (so both Packard NAA get higher on a priority list), but will wait that RAF gets their order 1st.
1st Mustang reaches UK in Oct 1941 (with British engine), 1st operational use in July 1942.
USAAC places an order for P-51 in Jan 1942, the plane is 1st flown in June 1942, with 1st combat use in Feb 1943.

There is actually only a small window of time when there would be enough Packard built Merlin's available to make such a project worthwhile and when such a project would delay the introduction of the P-51B. Put that together with which Allisons were available when (or promised, there were several projects in the works for high altitude engines in late 1941). I would note that the final 310 Allison powered Mustangs got improved engines that cut the difference in altitude performance between the older Allison engines and the V-1650-1 about in half.

The window of time could span to some 10-12 months for USAAC, so not really small time. The delay for historical P-51B was due for numerous things - low availability of 1650-3 is the main thing. The success of the V-1650-1 powered Mustang would get people thinking even more: we just can't wait to fly it with two-stage inside!

The fact that the Mustang has less drag than a P-40 also means it can climb better at the same weight because less power is going into forward flight, leaving more power for climb.

Agreed.

The US Government (AAC) did not allow WER ratings until Dec of 1942. What combat units did seems to have been a different story.

Of course; the 'push' for the Allisons did made the fighters with those quite the performers between deck and 10-15K (depending on the model)

 

[Shortround6]

.So by 'European context' you mean MTO in this case - okay, we can consider a historical situation re. P-40F as 'almost none for ETO'.

First "F"s went to Egypt in July of 1942, six months after production starts, they are in combat in August, 57th fighter group goes into action in Aug 1942. In the summer/fall of 1942 North Africa is where the Western Front is. The P-40s don't have the range to operate over France and Low Countries much better than the existing British aircraft and German fighter opposition is just a few Groupes. With the coming of the NA invasion on Nov 8 1942 NA really became the center of effort in the west. With some convoys sailing in the middle of October this meant that ship loadings and force allocations had been made weeks earlier.

It had to be expected that the P-40s would operate against German aircraft.

We can take another approach as to what kind of threats USAAC is to expect from LW: in 1940 (or - even in 1939) it was known for fact that LW fields the 370 mph fighter. Should the USAAC brass expect that Germans will not move forward, to introduce a plane capable to do 400 mph within 18 months ( or -10 months from BoB it was) - in time P-40 with V-1650 is in service (or - make it a full year before P-40F)?

The P-40 was never intended to be the US premier fighter. It was ALWAYS the second best fighter BUT the low risk fighter that could be built in large numbers while the better fighters were developed and put in production. in 1942 there wee 3854 P-40s built compared to roughly 4740 P-38s, P-39s, P-47s and P-51s (of all kinds) built combined. Counting the Mustang out as a British plane (from the USAAC brass point of view) they were planning on the P-38 and P-47 to take care of the German 400mph fighters.
The P-40F served two purposes. It gave the US somewhere to stick the 1/3 of Packard production that was agreed to in the original 9000 engine contract and it offered a useful boost to P-40 performance to help "hold the line" while the P-47 and P-38 got over their initial troubles and got into full production. Please note that while the contract was placed in Sept of 1940 Packard doesn't really hit it's stride until April of 1942 when production tops 500 engines a month, later in the year they go to over 800 a month.

Thanks for the insight about Mustang's historical time line.
What can (good or bad) happen for Mustang, with Brits supplying the NAA with a Merlin XX in late 1940? The engine is installed flown within 4-6 months, and brass both at RAF USAAC are satisfied, and both British contracts for Mustang are altered for V-1650 instead of V-1710. USAAC wants the plane (so both Packard NAA get higher on a priority list), but will wait that RAF gets their order 1st.
1st Mustang reaches UK in Oct 1941 (with British engine), 1st operational use in July 1942.
USAAC places an order for P-51 in Jan 1942, the plane is 1st flown in June 1942, with 1st combat use in Feb 1943.

A. You are modifying the time line so that the Mustang prototype is given a new engine just before it flies, First flight with Allison was Oct 26th 1940. Three more flights are made in Nov but the SOLE prototype crashes on the 5th flight, it is later repaired. This delays things a bit. Modifying the contracts means the British have to supply the engines for the first few hundred aircraft. Packard isn't ready. Packard was already high on the priority list, as an example Allison was 800th on the list and in 1941 Allison engines were being rationed to Lockheed, Bell and Curtiss because Allison couldn't build them fast enough (another reason for the P-40F) Without some real evidence there is no reason that a magic wave of the "priority" wand would have changed things much. Which British aircraft don't get their Merlins so that the Mustang project can proceed?

The window of time could span to some 10-12 months for USAAC, so not really small time. The delay for historical P-51B was due for numerous things - low availability of 1650-3 is the main thing. The success of the V-1650-1 powered Mustang would get people thinking even more: we just can't wait to fly it with two-stage inside!

How much of a "success" is the V-1650-1 powered Mustang? It still can't fly top cover for the bombers. For that you need performance at 25,000-30,000ft. the single stage Merlin won't provide that, while better than the Allison powered Mustang the V-1160-1 is about 400hp down at 23,500 compared to a V-1650-3 or later Merlin. For escort service you need more range, the Early Merlin Mustang is good but but again with the Early engine (which is 150-200lbs lighter + prop weight) putting in a rear fuselage tank gets very iffy. After the Dec of 1942 the V-1650-1 shows no advantage at low altitude compared to the Allison powered planes ( the change to WER) which may have been done sooner by some service squadrons.
For the low altitude attack or photo recon Missions the V-1650-1 version doesn't really have a big advantage over the Allison powered versions.

 

[tomo pauk]

How much of a "success" is the V-1650-1 powered Mustang? It still can't fly top cover for the bombers. For that you need performance at 25,000-30,000ft. the single stage Merlin won't provide that, while better than the Allison powered Mustang the V-1160-1 is about 400hp down at 23,500 compared to a V-1650-3 or later Merlin.

P-51 Was capable of 396 mph at 1150 at 12600 ft (MIL power; static mil power was @ 10800 ft, so the gain via ram effect is 1800 ft)
P-51A was capable to make 408 mph at 1125 HP at 17500 ft (MIL power; static MIL power maximum was @ 14600 ft, so the gain via the ram effect is 3000 ft).
V-1650-1 was offering 1120 HP @ 18500 ft already, no ram (static). Think that we can expect the dynamic (ie. with ram effect) MIL power to be attained at circa 22 000 ft; that should give us about 415 mph there?
Further: P-51A was still doing 395mph at 25000 ft - so I see no problems for 'my' Mustang to attain the same speed some 3-4000 ft higher.

For escort service you need more range, the Early Merlin Mustang is good but but again with the Early engine (which is 150-200lbs lighter + prop weight) putting in a rear fuselage tank gets very iffy.

No need for the fuselage tank here - P-51D with 184 gals in wing tanks + 150 in drop tanks is credited with combat range of 460 miles; P-51D/K are the draggiest heaviest of the breed? The 1650-1 Mustangs would be both lighter and more streamlined, so we can extract another 5% more.

After the Dec of 1942 the V-1650-1 shows no advantage at low altitude compared to the Allison powered planes ( the change to WER) which may have been done sooner by some service squadrons.
For the low altitude attack or photo recon Missions the V-1650-1 version doesn't really have a big advantage over the Allison powered versions.

Unless the RAF properly boost their mounts already in 1942 (we in RAF need something both fast reliable to catch those pesky Fw-190s down low) show the USAAC the way. Even without that, having a plane capable doing 400+ mph from 20-25k, with great combat range, with low price, from beginning of 1943 was not something USAAC was enjoying as an asset. In my eyes that's better than what they were doing with non-Merlin Mustangs in the same time frame.

You are modifying the time line so that the Mustang prototype is given a new engine just before it flies, First flight with Allison was Oct 26th 1940. Three more flights are made in Nov but the SOLE prototype crashes on the 5th flight, it is later repaired. This delays things a bit. Modifying the contracts means the British have to supply the engines for the first few hundred aircraft.

I don't see any problems Brits delivering a hundred of engines in late 1941, but even with waiting for Packard to deliver them I've already moved the 1st combat use from May 1942 to July 1942.

Packard isn't ready. Packard was already high on the priority list, as an example Allison was 800th on the list and in 1941 Allison engines were being rationed to Lockheed, Bell and Curtiss because Allison couldn't build them fast enough (another reason for the P-40F) Without some real evidence there is no reason that a magic wave of the "priority" wand would have changed things much. Which British aircraft don't get their Merlins so that the Mustang project can proceed?

No need for magic - instead of delivering one engine in late 1940/early 1941 (for Curtiss that is), Brits deliver 2 engines - one for Curtiss, another for NAA. NAA mount is found to offer better performance, so the brass wants it. The P-40F founds itself at second place on the priority list for engines produced by Packard, for US.

The P-40 was never intended to be the US premier fighter. It was ALWAYS the second best fighter BUT the low risk fighter that could be built in large numbers while the better fighters were developed and put in production. in 1942 there wee 3854 P-40s built compared to roughly 4740 P-38s, P-39s, P-47s and P-51s (of all kinds) built combined. Counting the Mustang out as a British plane (from the USAAC brass point of view) they were planning on the P-38 and P-47 to take care of the German 400mph fighters.

I'm glad we agree that brass was planning for adversary 400 mph fighters after all. That would mean that none P-40 (-F included) was NOT a viable fighter to combat that threat.

The P-40F served two purposes. It gave the US somewhere to stick the 1/3 of Packard production that was agreed to in the original 9000 engine contract and it offered a useful boost to P-40 performance to help "hold the line" while the P-47 and P-38 got over their initial troubles and got into full production. Please note that while the contract was placed in Sept of 1940 Packard doesn't really hit it's stride until April of 1942 when production tops 500 engines a month, later in the year they go to over 800 a month.

P-51 seems like a vastly better 'place to stick 1/3rd of Packard production' than a P-40 to me (even if that's only 15%) - as cheap as P-40, yet as capable as future P-38 -47. Win-win situation both for people that will fly it and those to pay for it? It would take 1/2 time to build one vs. P-38, 30% less than for a P-47? After all, US is going to fight almost 2 wars from Dec 1941.

First "F"s went to Egypt in July of 1942, six months after production starts, they are in combat in August, 57th fighter group goes into action in Aug 1942. In the summer/fall of 1942 North Africa is where the Western Front is. The P-40s don't have the range to operate over France and Low Countries much better than the existing British aircraft and German fighter opposition is just a few Groupes. With the coming of the NA invasion on Nov 8 1942 NA really became the center of effort in the west. With some convoys sailing in the middle of October this meant that ship loadings and force allocations had been made weeks earlier.

It had to be expected that the P-40s would operate against German aircraft.

The necessity that P-40 will encounter German aircraft does not mean that P-40 is a 'viable counter for LW mounts', but simply that they were available.
As for where the Front line is - the aerial front line was very much between continental Europe an the UK, so that one can be called Western front? Exactly where 1st Mustangs were historically tested in combat, and found to be great planes, but under 15000 ft.

 

[wuzak]

Since the Fw190A was not a great altitude fighter woldn't the performance of the P-51A be sufficient to counter them in most situations?

 

[gjs238]

How much of a "success" is the V-1650-1 powered Mustang?

Wouldn't it be more successful than the other single-stage supercharger powered fighters? A V-1650-1 powered Mustang should out perform a V-1650-1 powered P-40, Hurricane, and offer far greater range/endurance than the Spitfire.

 

[gjs238]

P-51 seems like a vastly better 'place to stick 1/3rd of Packard production' than a P-40 to me (even if that's only 15%) - as cheap as P-40, yet as capable as future P-38 -47. Win-win situation both for people that will fly it and those to pay for it? It would take 1/2 time to build one vs. P-38, 30% less than for a P-47? After all, US is going to fight almost 2 wars from Dec 1941.

Seems the USAAC was not very eager to accept the P-51. This has been discussed in other threads, but it seems that the P-51 could have entered service earlier had there been more US support.

 

[tomo pauk]

Since the Fw190A was not a great altitude fighter woldn't the performance of the P-51A be sufficient to counter them in most situations?

I was proposing the same previously, but, ahem... was not allowed

Here is what kind of performance the Allied planes in 1943 should expect from Fw-190 (attached an excerpt from the manual that covers the A5 A6). Max speed at Notleistung (3 min) is 410 mph at 20300 ft, 'combat' ceiling 31000 ft, service ceiling 33340 ft (for P-40F 34300 ft, Hurri II 35000, P-51A 35100 ft). P-51A was allowed 15 min for MIL power (408 mph @ 17500 ft), ditto for V-1650-1 (FTH with ram effect in Hurri II was 22000 ft)?

For the Bf-109G-6, I've been able to find 620 km/h (w/ gondola 20mm cannons, maybe 630 km/h without - Ratsel?) at 6500m (385 or 391 mph at 21000 ft). Not sure if thats with 1,42 ata or less?
edit: 1,30 ata that was; with 1,42 ata that should yield 640-650 kmh (circa 400 mph) for a plane without gonolas, allowed only from November 1943?

 

[Shortround6]

Wouldn't it be more successful than the other single-stage supercharger powered fighters? A V-1650-1 powered Mustang should out perform a V-1650-1 powered P-40, Hurricane, and offer far greater range/endurance than the Spitfire.

It would, if you had enough engines, or if you accept that the fighters you take the two speed engines from either don't exist or become much less capable themselves if built with single speed engines.

The "problem" with the British supplying 2 speed engines until Packard gets going is that the British didn't have enough of the 2 speed engines to begin with. While I am sure one or two could have been pried loose for testing please remember that the Spitfire NEVER got the two speed, single stage engine (except for a prototype or two). The British gave priority to the Hurricane for the two speed engines because without it they thought the Hurricane would have been less capable than even the MK II turned out to be. They thought the Spitfire could "make do" with the single speed engine (Merlin 45, 46, 50). They were looking at the largest number of usable fighters to made with the engines available (bomber command sucking up the majority of two speed engines). They thought they could not afford the loss of production while trying to switch from making Hurricanes to another type of fighter.
As it turns out with the main use of Hurricanes in ground support perhaps the Hurricanes should have gotten the single speed engines and the Spitfires gotten the two-speed engines (might have reduced the advantage the FW -190s had).

The US was in the same position. In 1941 and 1942 the P-40 was being built in by far the largest numbers of any American fighter. New Factories are being built and equipped to expand production but they will not be ready until 1943-44. The British knew the limitations of the Mustang when they ordered it but figured the Spitfires would take care of the high altitude fighting anyway. Since it was ordered instead of additional P-40s (with Allisons) which were low altitude fighters anyway there was no change in British planning for how may squadrons got which level of fighter.
As it turned out the Allison powered Mustangs could just about hold their own against the Fw 190s in 1942 and early 1943 in the cross channel raids.

P-40F's were being built in parallel with the end of P-40E and then P-40K construction. P-40K production actually stopped before P-40F Production.

It wasn't just getting the MOST capable fighter in small numbers, it was getting the MOST capable fighters in large numbers.

 

[Shortround6]

I was proposing the same previously, but, ahem... was not allowed

Here is what kind of performance the Allied planes in 1943 should expect from Fw-190 (attached an excerpt from the manual that covers the A5 A6). Max speed at Notleistung (3 min) is 410 mph at 20300 ft, 'combat' ceiling 31000 ft, service ceiling 33340 ft (for P-40F 34300 ft, Hurri II 35000, P-51A 35100 ft). P-51A was allowed 15 min for MIL power (408 mph @ 17500 ft), ditto for V-1650-1 (FTH with ram effect in Hurri II was 22000 ft)?

A problem for trying to figure out performance of the P-40F vs the Allison powered models and the performance of the Allison powered P-51s and hypothetical Merlin XX P-51 is that not only are there 3 different Allisons in each type of airplane but WER came into use during the time periods they were in combat. These do not affect performance much, if any at high altitudes though. The next point of confusion is that the British and Americans didn't always agree on what the allowable boost settings should be for WER or combat power for both the Allisons and the MK XX Merlin. Or they may have eventually wound up at the same boost settings but did not always agree on a time line leading up to the eventual top rating. The Americans tended to stick with the 9lb boost rating or perhaps 10.5lbs/12lbs WER for the V-1650-1 while the British went fairly quickly to 12lbs and eventually hit 14lbs in low gear and 16lbs in high gear. Later versions of the two speed engine British engines were allowed to use up to 18lbs in either gear. Again, any performance gains would be below FTH.

The Allison did seem to handle increased boost at least as well at low altitudes as the "early" Merlins. While some squadrons did use "unapproved" boost levels to rather high levels the "approved" ratings were usually between 56 to 60 inches, or 13-15lbs boost. Granted the official approval comes at a time point when the decision to build a Merlin XX powered Mustang would already be past. How much of this "un-official" boosting in actual combat affected the results of the combat reports I don't know.

I would be highly suspicious of a Hurricane claiming a FTL of 22,000ft. that is 3,500ft higher than the NO Ram rating (?) and the Hurricane was not a fast airplane. In fact one chart shows the FTLs for the P-40F as 18,500ft with Ram but it may be in error. Another chart shows and improvement on a P-40N of 2,000ft (from 15,000 to 17,000ft) with Ram.

Another complication is when did each step in engine performance become known, as in when could the planners feel sure a promised performance boost would actually become available, or in some cases were they surprised by quicker than expected developments. Consider the fuel situation. In 1940, when according to this scenario, the British are supposed to ship a Merlin XX to North American for testing in the first or second P-51 air frame 100/130 fuel does not exist. 100 octane American and 100 octane British fuels are not the same and in early/mid 1940 nobody even really knows what the measurable differences are. At some point the Americans come up with a 100/125 standard (which several Allison types are tested with) but the British and Americans do standardize on the 100/130 fuel which allows those big increases in power, subject to the basic engine being able to stand the strain. Both companies instituting changes to the basic structure of the engine to allow full use to be made of the better fuel.

Another thing to consider when comparing performances is that the British and Americans measured climb performance differently. For instance in a US test the P-51 (no letter) had a max climb rate of 2940fpm at 10,000ft. while a British test says 1,980 feet/minute at 11,300 feet. The difference is that the Americans used full military power (but not WER) for the climb test for the first 5 minutes of the climb and then throttled back to maximum continuous for the rest of the climb test. British procedure was to use a 30min rating or max continuous rating for the entire climb. British climb figure was achieved at 2570rpm and 36.9in of manifold pressure. American climb figure was at 3000rpm and full boost (44in or close to it). What an Allison powered Mustang could climb like at 5,000ft using 3000rpm and 56in of boost I don't know?

Rolls Royce did a paper study of installing a single stage Merlin in the summer of 1942 at the same time they did the study on the 2 stage engine. Initial report showed a speed of 441mph at 25,500ft using the Merlin 61 (calculated) vs 40mph at 18,600ft for the Merlin XX. a few weeks later the speeds had been revised downwards to 432mph for the Merlin 61 and 393mph for the Merlin XX. Granted this performance could have been done earlier if the V-1650-1 had been fitted but 393mph at 18,600 ft isn't much different than what the last 310 Allison powered Mustangs could do. Thus my comments about how much improved the single stage Merlin Mustang would be.

 

[tomo pauk]

The WER rating for P-40s and P-51s will made the impact for plane performance under 15000 ft, but from my posts it's clear that I'm gearing the plane to be a strong performer at 20-25 kft (and still good one from 15-20K and from 25-30K). I's pretty clear, too, that such a plane is not intended to be the best climber, but again to be quite fast plane at those altitudes.

As for when Brits shoul've sent the Merlin XX for the NAA - I've written twice that's late 19440/ early 41 I'm talking about, not unlike they did for Curtiss. So no early '40, nor mid '40.

For Hurri IIA/B maxing it out at 22kft, here is chart:

http://www.wwiiaircraftperformance.org/hurricane/hurricane-II-raechart-level.jpg

I'm with odds why would RR expect the P-51/Merlin XX would be capable only to elevate the FTH for just a 100 ft? To say nothing about the two stage in the plane - real world P-51B was having FTH equal to 32000 ft at high speed (= plenty of ram), MIL rating; static FTH (= no ram) being 26400 ft. In other words, due to the speedy potent engine/airframe combo, P-51B was gaining 5600 ft to it's FTH at second gear.
Perhaps the people at RR were talking about WER, or what ever over-boost? Then it would be useful to know how much HP they were expecting from both engines?
added: if that was WER in the equation, it means maybe 1300 HP at the those 18600 ft - notably more power, but lower speed vs. real P-51A. Again, not very likely.

(table posted previously by krieghund )