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54th Fighter Squadron received its first P-38Es in February 1942. It deployed to Alaska in late May. Flew the first operational mission on 3 June, a local patrol over Cook Inlet near Anchorage.The P-38 was in combat or in combat areas in Aug of 1942.
July 31st the 27th squadron stays in Iceland as a defensive unit, relieved by the 50th Squadron Aug 26th and continues on to England.
Aug 9th two P-38s claim to Japanese flying boats in the Aleutian Islands.
Aug 22 the 67th squadron with a mix of P-38s and P-39s arrives at Henderson Field.
Aug 31st 164 P-38s have crossed the Atlantic by air.
P-38 recon planes were already in Australia.
So when the war started the USN, with its lower tech approach, which the USAAC had given up on with the XP-41, that was ready to fight at higher altitudes.
that single-stage supercharger could hurt an aircrafts performance at low altitudes. IIRC, it was because the compressed air would become hotter, not a problem high-up where it is cold, lower down though, it apparently caused issues (pre-ignition?
I am not a technical minded person sadly, but what I take from this is that " single stage single speed superchargers is that they can only be optimised for one altitude". Though two questions:A difference was the two stage supercharger in the F4F was good for 1000hp at 19,000ft. The same P & W R-1830 when given a turbocharger (and using the same engine driven supercharger) was good for 1200hp at 25,000ft in the last versions of the P-43. It did require a bit more weight and bulk and the turbo (and controller) wasn't really ready for front line use.
The problem with single stage single speed superchargers is that they can only be optimised for one altitude. The Best engine I know of for illustrating this is the Merlin. The Merlin III used in the Hurricane I Spitfire I and a several other British aircraft would hold 6lbs of boost (around 42in ) to 16,250 ft with the engine turning 3000rpm which spun the impeller at 25,764rpm.
Please note that anytime the engine was doing 3000 rpm the impeller was spinning at 25,764rpm regardless of altitude. The air at 16,000ft is at 16.21 inches of Hg so the Merlin supercharger was compressing almost 2.6 times. If the throttle had been opened all the way at sea level the supercharger might have been able to produce 77in of manifold pressure which would have certainly either caused massive detonation with the fuel available or destroyed the engine even without detonation. By restricting the amount (volume of air) coming into the supercharger at sea level the engine made 880hp for take off at the same 3000 rpm and same 6lbs of boost (some books give 6 1/4lbs).
There are two sources of heat rise in a supercharger. One is the simple heat rise of the work of compressing the air/intake charge even assuming the compressor is 100% efficient.
The other is the fact that most pre-WW II and WW II superchargers were not very efficient. If 70% of the power applied to the input shaft of the supercharger actually went to compressing the air it was a very good supercharger indeed in early WW II. The other 30% of the power didn't just disappear. All but a tiny percentage (under 1% for friction) went into heating the air over and above the heating done in actually compressing the air. You wound up with some very hot air going into the engine.
A supercharger that was 65% efficient saw 35% of the power applied to the input shaft turned into excess heat of the intake air/charge and so on for lower efficiencies.
the power needed to turn the supercharger impeller was proportional to the speed of the impeller (or more properly to the speed of the tips but if we are talking about the same supercharger the impeller speed will do). Obviously reducing the impeller speed will require much less power and also much less power going into heating the intake charge.
The supercharger on the Merlin VIII engine was the same as the Merlin III except it used a set of 6.313 gears instead of 8.588 gears the overall change was an increase in take-off power 50 1080hp at 3000rpm using 5 3/4lb boost. Less power used to turn the supercharger, throttle plate open further reducing pumping loss and a much cooler/denser intake charge. trade of was engine topped out at 1275hp at 3000rpm at sea level suing 9lbs of boost.
The heat of compressing the air, especially when factoring in the waste heat, rose faster than the outside air temperature dropped with rise in altitude.
The heat rise of a Merlin XX engine with Hooker supercharger (more efficient than earlier models) was figured to be 148 degrees centigrade at 3000rpm in high gear almost regardless of altitude. at 35,000ft the intake charge temperature in the intake manifold wass about 95 degrees centigrade. In part due to the fact that much less work was being done. Only 84.5lbs of air and fuel per minute going through the supercharger ( and outlet pressure of 26.56 in) compared to the 144lbs at 20,000ft and the output pressure of 48.24in.
I hope this isn't too confusing. But superchargers, despite only having one moving part are not always simple to figure out
Regarding the P-38 there were a few P-38s on station around the world in the last half of 1942, but most historians say that Operation Torch in November '42 was their European debut. They began operating in strength in the Pacific in December '42. Vast majority of 1942 was fought with the P-39, P-40 and F4F.The P-38 was in combat or in combat areas in Aug of 1942.
July 31st the 27th squadron stays in Iceland as a defensive unit, relieved by the 50th Squadron Aug 26th and continues on to England.
Aug 9th two P-38s claim to Japanese flying boats in the Aleutian Islands.
Aug 22 the 67th squadron with a mix of P-38s and P-39s arrives at Henderson Field.
Aug 31st 164 P-38s have crossed the Atlantic by air.
P-38 recon planes were already in Australia.
How???
remove armor?
Not fill fuel tanks?
Take out guns & ammo?
remove electric starters and fit smaller batteries?
a reason they were heavier than British and Axis fighters was that they carried more fuel and a heavier weight of guns and ammo. This heavier payload required a heavier structure which unit mechanics would have difficulty modifying.
but the added guns, armor, and folding wing mechanism increased the weight by over 500 lbs. The Navy pilots were most upset about the decrease in firing time from 34 second to 20 seconds. The FM-1 and FM-2 returned to the four gun armament
According to figures in AHT the F4F-4 gained almost 300lbs in the wing alone.
I have no idea
There is always the question of how a plane is loaded. Geoff Fisken reported that to improve the chances of survival in the Buffalo, they stripped them of all excess weight and reduced the ammo to about 5 seconds worth. They had learned that they were only going to get one pass at the enemy, and adapted accordingly.The benefit of the four gun armament in the F4F and perhaps the P-40 rather depends on how the planes were loaded.
The F4F-3 was listed as having 286lbs worth of guns with 360 lbs of ammo (300rpg) 'standard' and 516lbs of ammo (430rpg) in overload condition.
The F4F-4 was listed as having 288.7lbs worth of guns (four guns )with 240 lbs of ammo (200rpg) 'standard' or 422lbs worth guns (six guns) and 432lbs of ammo (240rpg) in overload condition.
Please note that an F4F-3 with 430rpg was carrying about 54 lbs less weight than an f4F-4 with six guns and 240rpg.
The P-40D was likewise designed with a ridiculous amount of ammo capacity, but since only about 30 were built ( I don't know how many British planes showed up with only 4 guns)
we have a weight of 256lbs for 4 guns * and 300lbs for 250rpg designed weight capacity but the ammo bins would hold 738lbs of ammo (620 rpg) in overload condition.
The P-40E had a design load of 384lbs worth of guns (six) and 423lbs worth of ammo (235rpg) amd an overload of 561lbs of ammo (1870 rounds total).
Please note the "design" fuel load (for design gross weight) was 120 US gallons of fuel while overload included both an extra 25.5 gallons in the fuselage tank plus the drop tank.
Please remember that both the F4F-4 and the P-40D/E were ordered in the summer of 1940 and the high rate of fire M2 gun had not yet been approved.
For the WIldcat if you pulled the two extra guns but loaded in the extra ammo to extend the firing time you are not going to see much of change in performance.
Some of the light weight P-40s resorted not only to four guns but 235rpg or even 201 rounds per gun. Which is why they gained weight in squadron service. By the time they were in service they were no longer tasked (at least not often) with the high performance interceptor role.