Missed opportunity: US Navy land based P38D and P38E with dive flaps as a vertical dive bomber early 1942

[Glider]

There is a HUGE difference between firing at B26's at sea level doing torpedo attacks and shooting at SBD's diving from altitude. Shortround is correct that the Japanese had no AA between 25mm and heavy AAA. They had 0 quick firing medium range weapons such as the 40mm Bofors on their ships.

I certainly could be wrong but my belief is that the USN were basically in the same position at Midway. 20mm had been added and some had the quad 1.1in a weapon I once saw quoted as almost better than nothing. The HMG was a common aa weapon but people always seem to have a go at the Japanese forgetting that the 40mm was but a distant dream for most ships at that time.

The comments about the 25mm being nothing more than a revenge weapon also apply to the 20mm and as for performance, the 20mm was a better weapon certainly, but the 25mm was far from useless. It had a slightly higher MV and probably slightly better ballistics which tend to favour the heavier shell than the 20mm.

 

[tomo pauk]

I'd suggest modifying the undercarriage so it can double as a dive brake. Worked on F4U.

 

[Shortround6]

When you pull out at 300 mph at 500 feet or so, you pull up flaps and pin the throttle and run like mad.

When you pull out at 300 mph at 500 feet or so you will hit the water.
The higher speed airplane needs to start pulling out and releasing the bomb at a higher altitude in order to pull out safely.

If you drop from 2000ft your hit rate will be about 1/4 what it is if you drop at 1000ft. if you drop from 1400ft your hit rate will be just about 1/2 the hit rate at 1000ft.

This "assumes" same sight picture and drop conditions.

 

[Kevin J]

I'll go ahead and repeat that I agree that a P38 dive bomber would have been difficult or maybe impossible to build due to fitting true dive flaps big enough slow it down for proper dive bombing (same envelope as an SBD)

That being said, if by some miracle, some working monster sized dive flaps were attached that didn't hurt performance, here is how they, in my opinion would be used:

Take off, climb to 25,000 feet, cruise to enemy fleet at appropriate speed. Nearing enemy fleet, drop tanks are released, speed is increased to 350 mph. Instead of an asymmetrical bomb load, carry 2 500 pounders, one very tightly on each side of center nacelle. Doubtful Zeroes would be at 25,000 feet, if you see them, turn directly at them and make head-on firing pass. They can't turn around and catch you before your gone since you already have a speed advantage (350mph compared to 315ish at 25,000 feet). Cant see targets from 25,000? Cant pick out a target from 25,000? Ok, lower the nose and dive at a shallow angle down to 20,000 or 15,000 or 12,000, keep your speed around 400-425 mph whatever is controllable. A zero shouldn't be able to catch you. If they are lower than you, make a firing pass through them to scatter them, you are moving along at 400 plus, if they scatter they won't be able to catch you. pull out on the level at whatever altitude you want to dive from, pull back on throttles, flat pitch the props, deploy dive brakes while on the level until your speed is reduced to 300 mph, then roll over and dive on your target. The likelihood of a Zero being in the perfect position to intercept your group is very low since they don't have radar. Once in a steep dive (70 degree or whatever) you will make a difficult target for a Zero anyway. He can't roll at that speed so he will only have elevator and rudder to make corrections. When you pull out at 300 mph at 500 feet or so, you pull up flaps and pin the throttle and run like mad. A Zero making a run on you has to worry about the whole string of P38's behind you, remember, your in a fighter. A P38 had great vision everywhere but down left and right. If a Zero is diving on you, while your doing 300 mph or more, he will have to be exceeding that to catch you, you will be able to see him, he won't be able to roll or turn. He would be easy to avoid. (In trials a P38 could out turn a Zero at high speed). If he is anywhere in front of you, you turn into him (4 50's and a 20mm, bring on a head on pass. Great view ahead, bring on deflection shooting).

Now, who would rather plod into the same scenario in an SBD (it was a great aircraft) at 180 mph? Zero see you before pushover point, they are already above you, if not they have time to get there if they are in any reasonable position. (If they can't get into position to attack an SBD then they sure as heck won't do it on a P38) They have plenty of time to make multiple attacks before you dive. You dive and pull out. What is max speed of an SBD at SL? 225 mph? I know it was 255 mph at 14,000. Would you rather run from a Zero at 225 mph or 340 mph? Would you rather do a head on attack with 2 50's or 4 50's and a 20 mm? How about a deflection shot?

In reality the dive bomber P38 wasn't built, may have been difficult, may have been impossible, but if it had been, that would be the way to fly and attack in it.

SBD-3 had a terminal dive speed of 740 kmh as opposed to an A6M2 of 660 kmh so as I see it a Dauntless should be able to evade a Zero using its dive speed until its escorts came to the rescue.

 

[Shortround6]

On the Japanese 25mm AA gun.

From Wiki, take it as you will.

"The Type 96 was most effective when used at ranges of 1,000 meters or less. The Japanese military estimated that it required an average of 1,500 rounds to shoot down an aircraft at a height of 1,000 meters and a range of 2,000 meters, and that fire beyond that range was completely ineffective. "

This supposed to be from a Japanese evaluation.

Later"

1. Elevation and traverse were too slow, even with powered mounts;
2. The sights were ineffective against high speed targets;
3. Firing the multiple mounts caused excessive vibration, which reduced accuracy and prevented effective target tracking;
4. Too little ammunition in each magazine resulted in a low overall rate of fire.

Drawing of the single 25mm

It was heavier and harder to aim than a single 20mm but perhaps not as bad as as a twin 20mm?
However it fired at about 4 rounds per second and the magazine held 15 rounds.
The 20mm fired at 7-8 rounds a second and had a 60 round magazine.
A hit from the 25mm was much more effective but was going to be harder to achieve.
The twin mounts were all hand crank operated. The triples were some hand crank and some powered.
Rate of fire for the middle barrel might be less than the outside barrels?

The trouble with dive bombers is that their path is pretty predictable once they start the dive. They don't often turn much until the worst of the G load on the pull out is over.

 

[Shortround6]

SBD-3 had a terminal dive speed of 740 kmh as opposed to an A6M2 of 660 kmh so as I see it a Dauntless should be able to evade a Zero using its dive speed until its escorts came to the rescue.

trouble is that is NOT the speed used in the attack. Once the attack is over the Dauntless is at less than 1000ft of altitude making top or terminal dive speed rather pointless. How long will it take for the Dauntless to climb back up to height at which it can come close to even 600kph in a dive? and while climbing it is going how fast?
Dive bombers stay on the deck, bob and weave and hope rear gunners can discourage pursuit.

 

[pinsog]

When you pull out at 300 mph at 500 feet or so you will hit the water.
The higher speed airplane needs to start pulling out and releasing the bomb at a higher altitude in order to pull out safely.

If you drop from 2000ft your hit rate will be about 1/4 what it is if you drop at 1000ft. if you drop from 1400ft your hit rate will be just about 1/2 the hit rate at 1000ft.

This "assumes" same sight picture and drop conditions.

I meant level off at 500 feet, not start your pullout at 500 feet.

I went back and edited my previous post to explain that I meant start pullout at 1800 and level out at 500 feet

 

[Shortround6]

If you use a higher dive speed you will have to start the pullout sooner. See the diagrams posted earlier. I am not saying that the theoretical diving P-38 has to dive at 340mph but it is not likely to dive at around 250mph either like the SBD. The earlier SBD diagram had a 4 G pull out, the diagram for 340mph is using a 5 G pull out.

There are going to be several minutes where the P-38 is going slow enough for the Zeros to catch it if the Zeros are in close proximity. You do have a greater period of immunity both before and after the actual attack. You will, however, need more planes in the attack to get the same number of hits.

 

[pinsog]

I certainly could be wrong but my belief is that the USN were basically in the same position at Midway. 20mm had been added and some had the quad 1.1in a weapon I once saw quoted as almost better than nothing. The HMG was a common aa weapon but people always seem to have a go at the Japanese forgetting that the 40mm was but a distant dream for most ships at that time.

The comments about the 25mm being nothing more than a revenge weapon also apply to the 20mm and as for performance, the 20mm was a better weapon certainly, but the 25mm was far from useless. It had a slightly higher MV and probably slightly better ballistics which tend to favour the heavier shell than the 20mm.

Most of what I read about the US 1.1 inch AA gun wasn't very good, but I read 1 place where a guy said that they worked fine in combat and never gave them trouble. Another guy said they never worked in peacetime but worked flawlessly during the Pearl Harbor attack.

I agree with you about US Navy in the same boat, they removed the 50's and replaced them with 20 mm.

One other thing on the 1.1 inch, USS South Dakota during the Guadalcanal capaign was credited with breaking up the attack on the Enterprise. The Japanese variously describes her as "a ring of fire" and "a volcano" and this was before 40mm and 5 inch proximity fused ammo. One of my favorite quotes came from this fight, talking to the Wildcat CAP "stay away from that big bastard she's shooting down the sky". I guess radar giving you the range to set your fuses on your 5 inch would help.

 

[Shortround6]

My take on the US 1.1" was that it required more maintenance than some other guns, this may have actually been the powered mounting rather than the gun/s? It was only ever used as quad with power traverse and elevation. Big ships will have more senior personnel in maintenance. Small ships (DDs and DEs) will have a pretty thin crew for maintenance, not to mention the guns/mounts being closer to the water and catching more salt spray. Experience with the gun and mount could vary with the ship, the weather conditions, and the experience of the crew.
The British 2pdr had a reputation for being a bit fickle
The main failing of the 1.1" was that the mount was too heavy for the effectiveness of the guns. The quad mounts went 4.7 to 6.25 tons and that was too much weight for the weight of shell/ rate of fire/ range combination.

 

[pinsog]

If you use a higher dive speed you will have to start the pullout sooner. See the diagrams posted earlier. I am not saying that the theoretical diving P-38 has to dive at 340mph but it is not likely to dive at around 250mph either like the SBD. The earlier SBD diagram had a 4 G pull out, the diagram for 340mph is using a 5 G pull out.

There are going to be several minutes where the P-38 is going slow enough for the Zeros to catch it if the Zeros are in close proximity. You do have a greater period of immunity both before and after the actual attack. You will, however, need more planes in the attack to get the same number of hits.

We can nitpick the hypothetical P38 that never existed with hypothetical setups where hypothetically a Zero in exactly the right place at exactly the right time without radar direction and without a radio to get direction from the ship might be in a position to get a shot at a an engressing, diving or fleeing P38 that didn't exist because we don't know how fast it would dive, top speed or anything else.

But, I think I can sum this up: if you were a German pilot in 1945 attacking a US held bridge in europe, would you rather be in a Ju87 Stuka or an Arado 234 jet? Yes, a few times, Mustangs and Thunderbolts were in the perfect position and power dived down on an Arado 234 and managed to shoot it down. There weren't very many of those times. In 1945 an Arado 234 was essentially, except for dumb luck, untouchable. A super duper hypothetical non existent P38 dive-bomber in 1942 would essentially be in the same position when attacking non radar equipped Japanese carriers being covered by non radio equipped Zero's. If you are actually worried about the P38 dive bomber getting intercepted then send half a dozen down low at wave top height without bombs about 2 minutes in front of the dive bombers to suck the Zeros down low thinking they are torpedo bombers. In 1942 they wouldn't know what they are, just a bunch of big twin engine planes hauling butt at wave top height, must be torpedo planes. Without bombs they would be extremely hard to catch and if they did, congrats Mr Zero, you just caught up to the greatest anti Zero aircraft of the war when your both doing well in excess of 300 mph where even the P38 can out turn you... and the low level fight starts, clearing the way for the dive bombers to make their run unhindered.

 

[Shortround6]

Trouble with this comparison is that the Arado never performed a vertical or near vertical dive and never slowed down during it's attack to 2/3rds or so of it's max speed.

Your whole premise is that the US somehow missed an "opportunity" to start designing/ developing/ deploying a special aircraft or tactic that was pretty much only suitable for the battle of Midway a year before Midway happened and not only that, 4-6 months before Pearl Harbor Happened.

Twin engine planes doing 300mph plus at sea level weren't going to fool many people into thinking they were torpedo bombers. Not until later in the war when improved, strenghtened torpedoes allowed higher dropping speeds.
And at that speed they don't have to worry about shooting them down. They will run out of fuel.
The early P-38s (D & E) could hit about 295-300mph at 0-3000ft at max continuous with under wing loads, they burned about 180 gallons an hour doing it. They needed over 40 gallons just to start the engines, warm up, taxi and take off.
Attributing performance of later P-38s to these early P-38s doesn't help figure out what they were capable of.
The combat flaps that allowed the later P-38s to turn so well were not introduced until the F model in Feb 1942, This combat flap setting has nothing to do with the anti-compressibility flap fitted later. Perhaps it is a simple conversion for an existing aircraft, perhaps not, the D model, the E and the British 322s did not have it.
The D and E had 1100hp engines, that is it, case closed. No WER. The F got 1325 hp engines (but only 1240hp for take-off). Max continuous power was 1000hp for the early engines.
Squadron use of higher power is at the pilot's peril as Allison only started using the nitrided crankshafts around Dec of 1941, none of the Ds probably had them and availability for the E's would be spotty.
Since none of the Ds and very few of the Es (or F4s) went overseas the use of higher than recommended power settings was probably not great. It was the stronger crankshaft and stronger crankcase that allowed the engines in the F and G to be rated at higher powers.

The US already had a number of high performance planes in design/development/deployment in late 1941 and early 1942 that would have seen a modified P-39 as a redundant back up.
Granted a lot of these aircraft failed to show up on time but that doesn't mean there was enough money or engineering talent sitting around doing nothing that they could afford back up aircraft to back up aircraft to back up aircraft.
The US Navy's Bureau of Aeronautics had started a program in early 1939 for new, larger, faster dive bombers. The Douglas SBD was supposed to be an interim aircraft while these planes were developed. Both the Brewster Buccaneer and the Curtiss Helldiver (monoplane) first flew by the summer of 1941, both needed a lot of work, an awful lot of work. Vultee started work on the Vengeance in 1940 for the French, it actually beat the Brewster and the Curtiss into the air.
See also the Vought Seawolf which was designed to the same specification as the Avenger (also early 1939) and while judged superior when it finally flew Dec 1941 found itself without production facilities (Vought being heavily committed to the F4U by this time) and while the design was handed off to Consolidated, they too, had no production facility available and a new one had to be built.
Don't forget that both the B-25 and B-26 were supposed to carry a torpedo even on the early models. The Lockheed Ventura was being built for the British with 1850hp P &W engines.
the number of different dive bombers, torpedo bombers, high performance medium bombers almost staggers the imagination.
In fact Edward Heinemann and crew had come up with the proposal for the A-26 in Jan 1941 and had a mock up ready for inspection in April of 1941.
Tensions may have been rising but without an actual war the chances of modifying the P-38 to any additional roles are thin, like transparent thin.

 

[pinsog]

You really think that Zeros that have no radio are going to look down on a twin engine fighter they've never encountered before from 5,000 feet above that is as big as a medium bomber and say "nah, they aren't a threat, they are going too fast to be carrying a bomb or torpedo"?

No, here's what they will say "OMG!!!! TWIN ENGINE TORPEDO BOMBERS HEADED TOWARD CARRIERS!!!! GET THEM!!!"

Half the time pilots in combat can't tell the difference between s Fockewolf 190, a P47 an Me109 or anything else. How many times did pilots in Pacific or China theater report engaging Me109's? You could fly a hang glider down on the deck in this situation and the Zeros would be all over it.

I've already said it didn't happen and maybe it couldn't , but thinking the Japanese could handle it if it did happen is total BS. We had radar and let Kate torpedo planes blow right past F4F's on the deck as well as Val's blowing right past F4F's at altitude. A P38 over a Japanese fleet with no radar and no radios in their Zeros would be a field day for the P38's period.

 

[pinsog]

The Japanese don't know everything we have or what it's capable of. They also have 0 idea that our torpedos are complete junk. So when they see a flight of 6 P38's on the deck at high speed, they can only assume it's a torpedo attack because it's what they would do.

Only good at Midway only? What about the entire Guadalcanal campaign when their carrier planes sank the Hornet and damaged Enterprise. That might have been a great time to have a big long range twin engine un-interceptable dive bomber.

By mid 1943 it didn't matter what your bombing with since they were being escorted by real P38's, Hellcats and Corsairs

 

[Shortround6]

What I wrote was

Twin engine planes doing 300mph plus at sea level weren't going to fool many people into thinking they were torpedo bombers. Not until later in the war when improved, strenghtened torpedoes allowed higher dropping speeds.

few, if any countries had torpedoes that could survive being dropped at 300mph in 1942. The Japanese didn't get that capability until 1943 with the 4th version of the Type 91 aerial torpedo. Seeing a small group of planes at high speed close to the water doesn't usually mean torpedo bombers.

The P-38 was hardly the size "as big as a medium bomber" Unless you know some really small medium bombers.

The early P-38s were good for about 290-300mph at sea level max continuous while carrying under wing loads. full military power moved that up about 10-15mph at low levels. You are very difficult to intercept but not impossible.

However if you are carrying under wing bomb loads on both stations you don't get both long range and high speed. You have 300 gallons without drop tanks. you need over 40 gallons just to get off the ground and get to 5000ft. but we will call it 40 gallons for now, You need 180 gallons an hour to do that 290-300mph speed and just 5 minutes at military power burns 19 gallons. Just about 240 gallons for a 150 mile radius with 60 gallons left over? you should have 17-19 gallons (20 minutes) left in the tanks for the reserve for the return, finding the airfield due to weather/wind changes, poor navigation,minor battle damage and just waiting for your turn to land if you arrive in a group. But you don't need to do 300mph unless you are near the enemy ships.
So let's work it another way, 40 gallons for take off, 20 gallons for combat, 20 gallons for that 20 minute reserve, you have 220 gallons. lets say you want to do that high speed cruise when you are within 60 miles of the expected location of the Japanese ships. That is about 70 gallons for 60 miles in and 60 miles out. you have 150 gallons left. 80 gallons an hour will get you just about 235mph at low level. So you have a radius of about 225-295 miles depending on where the Japanese ships really are in relation to Henderson field. Can you fly a straight line to and from? will you have to search? or even dog leg based on updated radio reports? which way are the prevailing winds and how strong (that 20 gallon reserve may not be enough) using a single 75 gallon drop tank buys you something with a single bomb on the other side. With two 75 gallon tanks the radius goes up but you are now a decoy, you can;t hurt the ships, just suck the CAP out of position, a lot of effort for the results?

Now just for laughs how about we consider the A-20B as tested in the fall of 1941. max speed using Military power at 5,000ft in low blower was 333mph. Max speed at 12,050 ft was 349mph using military power in high blower. The A-20B carried 400 gallons in the wings and at 278mph at 5000ft in low blower on 400 gallons was supposed to have a calculated range of 610 miles using auto lean and 673 miles using manual lean.
You want a a high speed, land based plane for ship attacks, that might be a good place to start, except the A-20 was considered to be short ranged for the South Pacific.

 

[wuzak]

Maybe another option was to convert the 1,600lb AP bomb to a 2,000lb AP spin stabilised rocket projectile.

That way the P-38 could go into a shallow dive, fire off its one RP (having fuel on the other pylon) and then recover to altitude.

That way you don't have to modify any P-38s, and don't have to dive it at angles that would have quickly put it into compressibility problems.

 

[GrauGeist]

There is a HUGE difference between firing at B26's at sea level doing torpedo attacks and shooting at SBD's diving from altitude. Shortround is correct that the Japanese had no AA between 25mm and heavy AAA. They had 0 quick firing medium range weapons such as the 40mm Bofors on their ships. At least one of the Japanese carriers at Midway couldn't even fire directly upward, essiently if an SBD was diving on that carrier nothing besides maybe 25mm could even fire at it. 25mm AA guns on a ship are revenge weapons, the bomb has already been dropped. How do you know who killed that B26 that almost hit Nagumo's ship? The pilots may have been incapacitated by a Zero before the 25mm opened up in the final seconds. What is the reasonable range of a 25mm firing at a plane? 1000 yards? 500 yards?

During the all the attacks on the cruisers Mogami and Mikuma I believe they shot down exactly 1 Vindicator, not exactly a screaming success for the AA crews of 2 heavy cruisers and multiple destroyers.

Yes, the last torpedo strike at Midway pulled the Zeros down to low level, that is what the hypothetical P38 dive bomber would be about, avoiding Zeros. Japanese AA was a nuisance at best but not something that would stop a group of US Navy dive bombers.

Look, I understand that you're trying to hold a point, but we have to be realistic here. The Japanese AA was did take it's toll on Allied aircraft. Yes, it had it's shortcomings and yes, IJN AA policy was atrocious for a 1939/1940 world power, but the fact remains that it WAS there, it WAS capable of damaging/downing attacking Allied aircraft. To say otherwise is not doing the conversation any good.

And NO the B-26 was not damaged by an A6M it took severe damage from the Akagi's defensive fire - plenty of authentication and can be referenced in books like "Shattered Sword", for example. You have to understand that the A6M was an impressive machine, but it could not by everywhere at once (like at Midway).

 

[swampyankee]

I'd suggest modifying the undercarriage so it can double as a dive brake. Worked on F4U.

It would be far easier to modify the wings with upper and lower surface airbrakes. While at it, don't forget to beef up the booms and wing spars, upgrade the hydraulics and electricals, improve the corrosion protection, and spend enough time training the pilots.

 

[drgondog]

And bombing Europe in '44 was hardly comparable to bombing Japanese ships at sea in '43. Those lightinigs cruising at 25000' at 350mph would have been near impossible for 330mph Japanese planes to intercept.

Highly unlikely that a.) P-38 could 'economically' cruise faster than 220-250 mph TAS with a 2000 pound external bomb load, and b.) that it would plan a flight inbound and out higher than 15,000. If range was not a factor, then it could fly higher and even at the lower cruise speeds it would be fairly tough to intercept with A6M. But Why Bother ?? there were Never enough fighter/interceptor versions to meet AAF theatre demands until late 1944 when the P-51D and late model P-47D largely replaced them in ETO/MTO.

 

[Ivan1GFP]

I'd suggest modifying the undercarriage so it can double as a dive brake. Worked on F4U.

From what I remember, the main gear on the P-38 (Mostly the Doors) was a pretty complicated setup.
I don't believe this would be an easy task.

In general, this discussion is getting to be pretty amusing.
We are still trying to figure out how an aircraft that was for all practical purposes unavailable to the Navy could have been modified to perform a very specialized task that it was basically unsuited for.

If by some amazing circumstances, P-38s had become available to the Navy and pilots were trained to fly them why not just hang a couple really large drop tanks on them and use them as escorts for the SBD?
If you absolutely MUST have the P-38 as an attack aircraft, then perhaps swap out the 20 mm and a couple of the .50 cals for a 37 mm or perhaps even something bigger.

- Ivan.