I notice that even though the US had 20mm and 37mm aircraft guns, they seemed to prefer the .50 caliber; why is this, when you’d think the heavier calibers would be more effective ground attack guns?
At a guess: more ammo by weight. It’s better to be able to shoot for 3 minutes than for 1, even if the shots that manage to hit their targets don’t do as much damage.
Also cheaper/easier to manufacture both the gun and the ammo in bulk, since they were the exact same .50 cals carried by infantry or mounted on pretty much anything with wheels and/or treads. Makes logistics easier, too: even if you ship the wrong ammo crates to the wrong location, no problem, somebody can use that !
When it came to airborne weaponry, the US armed services tended to evaluate in terms of air-to-air combat rather than air-to-ground. For that purpose, the .50 was judged to be the right balance between projectile weight and rate of fire.
IIRC, some aircraft were fitted with 20mm cannon later in the war (after the opposing air forces were beaten down sufficiently that ground attack became more practical). But that’s as large as they got. My impression is that the USAAF’s experience with the Aircobra pretty much soured them on anything bigger.
The P-38 had a single 20mm cannon and the P-61 Black Widow had 4. The P-61 was designed as a night fighter, so by definition it would be shooting at bombers in its primary role where the greater punch of the 20mm would be the most useful. One other minor advantage of 6 or 8 .50 machine guns over half that number of 20mm cannons is jamming. When a round misfires, the pilot of the fighter obviously can’t just walk out onto the wing and clear the round. AFAIK neither was more prone to jamming, but the loss of one 20mm to jamming was a greater loss of total firepower than the loss of one .50.
There’s a big gap between one side losing air supremacy and the other gaining it. By the time the Luftwaffe was completely rolled up, the Eastern Front had already been decided on the ground, so we never got to see the impact that a heavy tactical air presence could make in a pitched battle of the era. The Il-2’s never got to act with strategic impunity until well after the point that it still mattered.
This is something of a holy war still being argued to this day. There were a lot of stated reasons: a greater rate of fire and quantity of projectiles helped compensate for the poor aim of the typical inexperienced pilot, no need for heavier weapons due to little enemy heavy bomber presence, easier supply and standardization with a tried and tested weapon, you name it. Both arms of US air power were in love with the .50 and confident in that selection…but nobody else in the world agreed with them. Every other air force was continually moving towards heavier and/or more numerous cannon over the course of the war, even the RAF, which was operating exactly the same kind of combat.
A great example of the difference in opinion is the case of the P-39: the only major American fighter based around a heavy cannon. It was not well-loved by US forces, considered a dog due to its performance at high altitude or high speed and even its armament was not appreciated - the different weapon trajectories was considered a weakness! The Soviets, however, received rather a lot of P-39s through the lend-lease program, and preferred them greatly over any other American design, as the only one that had maneuverability and firepower. They loved the things and used them right up through the end of the war.
To put the German navy build up into a more modern context.
Imagine if France decided to build a fleet of vessels designed to do nothing but sink aircraft carriers.
Who is likely to become alarmed at a policy that is solely aimed against them, and no-one else?
Germany had no real use for a navy, so the construction of a powerful fleet had only one implication.
While that’s true, some aircraft came closer than others. The P-47 Thunderbolt could carry two 500-pound bombs and deliver them with some semblance of what passed for accuracy in the day, which approaches a strategically useful payload.
In Hell Hawks, a mission is described in which 36 P-47s were sent against a German railroad bridge. They swooped in at almost 400 miles an hour and each one dropped two 500-pounders. Sure, a lot of them missed outright; but tactical dive-bombing was accurate enough that seventy-two 500-pounders obliterated the bridge.
The P-47 did such good work in the ground-attack role that it’s often forgotten that it had excellent performance at high altitudes (due to the huge engine, the “paddle” style improved prop, and the massive supercharger). Counterintuitively, at extreme altitudes, it’s been described as the most maneuverable fighter of the war (possibly because its powerplant continued to perform while others gasped, and of course in thin air the fat jug shape was less of a hindrance? I don’t know the technical reasoning).
…bugger, wrong thread
Sorry, not to be argumentative, I’m just confused. The entire payload of the mission was 72 bombs, two per plane. And “a lot of them missed outright”. So how many bombs on target did it take to actually obliterate the bridge? I’m thinking not so many.
I think the accuracy of tactical dive bombing might be more fairly judged by a comparison of the number actually needed to effect destruction versus the number thrown in the bridge’s general direction.
I don’t follow what you’re asking here.
I wasn’t making any attempt to analyze the accuracy of dive bombing – I take it s a given, from everything I’ve ever read.
“Lots of bombs missed,” but the target was hit == highly accurate for the day and age (a typical high-level bombing mission result was “No bomb fell within 5 miles of the target.”)
My point was mostly that the use of 36 aircrew, 36 engines, and 72 bombs to take out a strategic target was highly efficient compared to a typical 4-engine-bomber strategic raid…and thus there’s some grounds for the OP’s argument.
Low-flying aircraft take more AA fire and so have to be very robustly survivable against damage. With that and carrying specialized ground-attack weapons means that fighter-bombers and ground attack aircraft still suffer from the weakness that they are at a disadvantage against dedicated air-superiority fighters. So you still need air superiority or at least very good escorts. It’s sort of like how dragoons were effective against foot troops but outclassed by true cavalry.
Sailboat, thanks, I understand your point now and cannot disagree.
That’s not comparing apples to apples, though.
It goes without saying that a low diving attack will net greater accuracy than a high altitude lob. The reason that strategic raids used the high altitude profile was because it was the least costly way to attack very heavily defended targets. A low altitude attack against heavy air defense, even with faster, smaller aircraft, invariably resulted in ruinous attrition. The Germans, Russians and Japanese all took heavy losses in their tactical attack wings learning that lesson.
If you’re going for a poorly defended target, however, a heavy bomber on a low profile is just as capable of accurately delivering a much larger payload. The RAF did a fair bit of use of medium and heavy bombers in low-altitude roles, and chalked up quite a few successes with only a handful of bombers per target.
Tell the P-47 jockeys they and their mounts weren’t equal to, or better than, their opponents.
Yeah, the Thunderbolt was a first-rate air-superiority aircraft when properly used.