The Grumman F4F Wildcat was first to utilize two-stage supercharger.

[Shortround6]

A number of C-47s did get two stage engines, they were used to "fly the Hump" into China.

 

[RCAFson]

The F4F-3 and the F4F-4 did.

The F4F-3A, the FM2 and most of the British Martlets did not. They did have two speed superchargers though.

In comparative testing the USN found that the F4F-4B (Martlet IV, IIRC) performed slightly better under 15K ft and was 240lb lighter. See page 3, paragraph 5:

http://www.wwiiaircraftperformance.org/f4f/f4f-4-02135.pdf

 

[PStickney]

I think that the Wildcat was the first military production aircraft to have a two-stage supercharged engine.

Either the F4F-3, or the PB2Y Coronado.
(The Navy's B-17) The Coronado's main role initially, wasn't long range patrol, like the PBY and PBM, but to drop armor piercing bombs (Most notably the US 1600# AP) on the decks of armored ships. (Just like the B-17). In order to get maximum striking velocity, the bombs had to be dropped from altitude, so the PB2Ys up through the PB2Y-3 had 2-stage engines - the Navy not being so hot on turbosuperchargers.
Note that the externally driven Aux Stage used on the P&W engines (R1830 and R2800) had 3 drive settings: Neutral (No power), Low, and High, effectively making the installation a 3-speed system -
Neutral - Engine stage only, Low - Aux Low + Engine Stage, High - Aux High + Engine Stage.

 

[PStickney]

A number of C-47s did get two stage engines, they were used to "fly the Hump" into China.

2 Speed engines, but not 2 stage. Postwar, most C-47Ds (With the 2-Speed R1830-90) had the high gear locked out, making them essentially identical with the single-speed R1830-92s of the C-47A.

 

[ThomasP]

Hey PStickney

While the PB2Y was designed to have level bombing capability, it was not with the 1600 lb AP - at least not unless the bomb it was intended to drop lagged behind in development by 4-6 years. The 1600 lb AP did not enter service until 1943 (I think). I may be misremembering, but I do not think the US had a proper AP bomb bigger than 500 lbs(?) in service before the war.

Also, although there are many inspirational stories (propaganda) saying otherwise, after pre-war testing of the Norden bomb sight by the Navy, it was determined by the Navy that it was virtually impossible to hit a stationary capital ship sized target from more than about 10,000 ft when level bombing.

 

[PStickney]

Hey PStickney

While the PB2Y was designed to have level bombing capability, it was not with the 1600 lb AP - at least not unless the bomb it was intended to drop lagged behind in development by 4-6 years. The 1600 lb AP did not enter service until 1943 (I think). I may be misremembering, but I do not think the US had a proper AP bomb bigger than 500 lbs(?) in service before the war.

Also, although there are many inspirational stories (propaganda) saying otherwise, after pre-war testing of the Norden bomb sight by the Navy, it was determined by the Navy that it was virtually impossible to hit a stationary capital ship sized target from more than about 10,000 ft when level bombing.

You're pretty much correct - I was running from memory, and got things a bit muddled.
The 1600# AP did exist prewar - it's included in the June 1942 TM9-1980 "Bombs for Aircraft".
But, the PB2Y didn't carry it - checking the Pilot's Handbook, the wing cells/bays were sized for the 1000# AP. in the prewar series. It seems it could also carry torpedoes - either 4 Mk 13 aerial torps, or (astonishingly) 4 Mk 15 heavyweight destroyer torpedoes. I haven't seen any reference to any air-dropped Mk 15s before this. The idea of a PB2Y making a torpedo run is mind boggling.
In addition, there were a number of odd-sized AP bombs, which appear to be 12" and 14" battleship AP shells fitted with carrying lugs and tails.
I'd like to see the reference for the Navy evaluation - the initial intention was that ships would be attacked by pattern bombing from a formation of bombers, and thus saturating the error circle.
In the event, though, that tactic was never actually implemented - in the early days, there were too few high altitude bombers in the Pacific, and carrier aircraft - Dive Bombers, and, after the issues with dropping the Mk 13 were sorted out, Torpedo Bombers proved more than capable of doing the job.

 

[RCAFson]

Hey PStickney

While the PB2Y was designed to have level bombing capability, it was not with the 1600 lb AP - at least not unless the bomb it was intended to drop lagged behind in development by 4-6 years. The 1600 lb AP did not enter service until 1943 (I think). I may be misremembering, but I do not think the US had a proper AP bomb bigger than 500 lbs(?) in service before the war.

Also, although there are many inspirational stories (propaganda) saying otherwise, after pre-war testing of the Norden bomb sight by the Navy, it was determined by the Navy that it was virtually impossible to hit a stationary capital ship sized target from more than about 10,000 ft when level bombing.

The USN had no AP bombs in service in 1942 and the USN dropped none in 1942 (IIRC) according to their stat summary.

 

[ThomasP]

Hey PStickney,

As far as I am aware RCAFson is correct. The only proper AP bombs (ie not converted costal mortar rounds) in-service/dropped through the end of the Guadalcanal campaign were 500 lb SAP. The 1000-1600 lb AP bombs may have been developed by sometime in 1942, but they were not deployed until 1943.

As far as the torpedo carrying ability is concerned, the lightest of the pre-war models of the Mk 15 torpedo weighed in at ~3800 lbs. The Mk 15 would not have been able to survive the drop into the water from 50-100 ft at 100 knots or more. Maybe it was possible to carry them for resupply purposes, disassembled, with the torpedo bodies carried in/under the wings and the warheads inside the fuselage? But that would still be lifting off with 15,200 lbs of cargo for 4 torpedoes, I do not know if the PB2Y could do that, even with a reduced fuel load.

re: "I'd like to see the reference for the Navy evaluation..."

Somewhere on the internet.... I will see if I can find it again, plus I may have downloaded the memo so I will also see if I can find it in my files.

 

[soulezoo]

I dread to think what people will be reading in 100 years time. There is an article doing the rounds showing 50% of people killed in the blitz on London were killed by British artillery, based on a study in 1938.

It has to be true... The article used Wiki as a primary source. *sarcasm*

 

[pbehn]

It has to be true... The article used Wiki as a primary source. *sarcasm*

Much worse, the studies at the time were genuine, but they took a few incidents from WW1 using ship guns used in land, counted the casualties from enemy action and defensive fire then extrapolated all that to the blitz. The whole point of the article was to hold Churchill responsible for half the deaths in 1940-41 to discredit him.

 

[soulezoo]

Much worse, the studies at the time were genuine, but they took a few incidents from WW1 using ship guns used in land, counted the casualties from enemy action and defensive fire then extrapolated all that to the blitz. The whole point of the article was to hold Churchill responsible for half the deaths in 1940-41 to discredit him.

The politics never really change, do they?