You have timing and program momentum affecting decisions.
A very simplified time line of British involvement goes something like:
Feb 1940-fabrication of on the 13 YP-38s is started.
March 1940, the British order 143 model 322s without turbos.
June 5 1940, US Approval is given for an additional 524 Lighting MK 2s for the British.
Aug 30 1940 the US orders 607 more P-38s than it had on order originally.
Sept 16 1940 First flight of a YP-38.
April 8 1941, British test a YP-38 at Wright Field Ohio, informally.
AUg 1941 sees 5 of the British 322s roll out the door, this does not mean delivered to the British.
Dec 1941 sees first British 322 arrive in England.
April 1942 has 3rd 322 arrive in England.
July 1942 has the 4th (and last) 322 arrive in England.
Aug 1942 sees the British Cancel the Lightning IIs.
Indeed, hence my initial comments regarding all that being moot with the P-38's existing development timeline. They'd need about a year earlier in timing there to really make this feasible. (otherwise you end up with Lightnings of any sort reaching England in number scarcely before the Mustang I)
Same problem with supplemental non-turbo P-38s for use anywhere. By the time the testing is done and production capacity is there, you've lost most of the advantages of a turbo-less P-38 anyway. Aside from maybe optimizing it as a moderately lower cost (maintenance included), lighter weight alternative to the P-38J/L for use as a low/medium altitude fighter, fighter/bomber, and intruder aircraft with better range and load than the P-47. (plus potential as a ground attack aircraft with cannon armament, especially interesting if the M9 37 mm cannon was fitted with rather useful anti-armor performance as well as ballistics and flight time better matching the .50s and better air to air/soft target accuracy than the low velocity M4 or M10 -and the P-38 should be heavy/powerful enough to carry it, unlike the P-63)
Timing is one of the big things that makes a V-1650-1 (or Rolls Royce Merlin XX) powered Mustang also impractical. Unless they'd started testing a single-stage Merlin prototype version of the P-51 and making production plans for it pretty much from the outset, it wouldn't have been fielded in time to make much/any difference.
Several Luftwaffe pilots have credited the P-38 for out-performing German fighters. But very few American pilots who served in North Africa had any previous contact with the enemy.
Sustained turning ability and ability to turn into a high-speed stall without spinning (due to balanced toque and gyroscopic stability effects) were very useful aspects of the Lightning from what I understand. The high lift airfoil, high aspect ratio wing, and twin prop wash (and maneuvering flaps) all helped with this in spite of the high wing loading and without the loss in lift:drag performance at high angles of attack suffered by the use of slats on the 109. (albeit pulling into a high-speed stall would intentionally be forcing excess drag, but without torque roll issues the 109 would have to deal with)
Roll rate and aileron stick forces would be the big limiting factor for the P-38 prior to the hydraulic boosting arriving part way into P-38J production. (the use of a yolk rather than stick may not have helped matters there either, and I know it made the already cluttered instrument panel more difficult to see)
The B-series turbos weighted some 135-145 lbs (
link). Deleting two of them per each 'P-38 minus' saves 270-290 lbs, plus some plumbing and controls/regulators. However, the '(turbo-)supercharging' group in the P-38J weight breakdown is at 613.5 lbs. So we'd probably save some 400-450 lbs vs. earlier aircraft, and those ~600 lbs vs. later aircraft. We should also save a bit of drag because the top of the nacelle would've been devoid of small air intakes, just covered with sheet metal. Also the ram air intake would've gone from the side of the boom to the top of the engine.
You should also be able to retain the smaller oil coolers and radiators of the P-38D-H, reducing drag somewhat there, and with the weight reduction concentrated to the outboard nacelle/wing portions, there should have been an appreciable improvement to roll rate as well.
Once the engines with 1200-1325 HP for take off are to be available, we'd might also add leading edge fuel tanks; fuel system of the P-38J was at ~506 lbs empty, with capacity for 410 US gals.
Older engines (aside from the long-nosed C series of the Lightning I and Tomahawk) should get up-rated take-off and emergency ratings as well, bringing the older V-1710-39 (F3R) of the P-40D and E up to par with the later 8.8:1 supercharger engines like the -73 (F4R I believe) though the maximum WEP boost pressure eventually ended up higher on the -73 in terms of official USAAF/Allison specs. (overboosting in the field went further, but how much detriment to engines there was is unclear; it might be notable that in their cautionary citations towards overboosting, Allison cited only the 60" Hg boost limit for the 8.8:1 supercharged engines including the -39 and -73, rather than a lower value specific to the older -39, though they did mention the use of 66" and 70" pressures in the field was risky had had not -yet- been cleared by testing while 56" was a more solid limit for the 9.6:1 engines due to detonation issues -at least with 100/130 fuel used in tests -I haven't seen any mention of testing with late war 100/150 fuel)
Fuel system wise, the weight gained on the P-38J over H would be more significant to consider. (if it's relatively small, then the added capacity would easily outweigh any light-load performance advantages, aside from potentially producing both and allowing field retrofits like the P-39N did -except being long vs very long range rather than short vs medium range)
Air Ministry didn't have to say no very loud. I may be reading the story wrong but it looks like the request for P-38s came at the end of 1942 (or beginning of 1943?) which a number of months after they (Air Ministry) had "canceled" the order for MK II Lightnings (relinquished to the Americans might be a better term) so the Air Ministry had no Lightings to give Coastal Command and very little likelihood of getting any. Unless they could show an overwhelming need their 'request' would have gone to the bottom of the lend lease stack and delivery scheduled for months if not a year down the road.
By that time, I believe any of the follow-on developments of Gloster Twin engine fighters was also discontinued in favor of focusing on their jet projects. (Wiki lists termination in May 1941) Leaving only the Mosquito and Beaufighter. (neither of which capable of performing the single seat fighter roles the P-38 could and Gloster twin might have)
Now how many people believe that the same number of P-39 or P-40 squadrons with pilots of the same experience would have done any better against the Germans in North Africa?
Certainly not, but 'P-38-minus' aircraft may have done rather well over North Africa, possibly better than the turbocharged instances in some cases (particularly if overboosting was exploited to similar levels as on the P-40 prior to formal WEP ratings).
Another question to pose would be: how well would turbo-less P-38s manage in place of P-40D-Ns and P-39D-Qs (possibly P-63s) if produced on the same number of available engines (ie pretty much exactly half the number of complete aircraft)? The Tomahawk production likely wouldn't change, and perhaps still a run of some Kittyhawks before production could be restructured. (so making the assumption/condition that Lockheed SOMEHOW managed to get the P-38 fully tested and mass production ready to the point of the P-38E by the end of 1940, and contracts for P-40 and P-39 production largely curtailed in favor of greatly accelerated expansion of P-38 production)
Hello Glider
I mostly agree but Fulmar did some good work against Italians in MTO and RN needed something to replace Skua, Sea Gladiator climbed rather well but was even slower than Fulmar and lacked range. Fulmar had loiter time and lots of ammo, so it could fly long CAP sorties and so partly compensate the lousy rate of climb, escort strike a/c and act as a recon plane. Ans the Sea Otter, I don't know much on it, other than was designed as a successor of Walrus and had somewhat better performance which didn't mean much. But British needed a ASR amphibian, was there any other candidates and RN probably wanted a amphibian catapult plane. Over 200 were built, so not so big consumer of resources.
Navalize the Hurricane. It won't cover everything the Fulmar can do but it's better in pretty much every useful way except wingspan than the Gladiator. (without introducing folding wing-tips of course)
That or the Gloster F.5/34. Much better armament and performance than the Sea Gladiator on the same engine. (and potentially the same engine as the Skua as well)
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