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

[pinsog]

Actually, the flaps on the SBD were the type of flap I was talking about installing on the P38. I also agree that the production line can't be shut down to do this. I thought/assumed that they could take older P38's and retrofit split dive flaps to them, not disrupting any production and mostly using P38D airframes.

Just curious, why would it take a redesign of the entire wing? Why couldn't it be added onto an existing aircraft? I get why it would have to be thoroughly tested, but I included that in my original idea.

 

[drgondog]

I meant don't build any 322's at all. Build them as standard P38's.

I would probably have used B17's in place of the photo recon F4's, but if you have them in New Guinea I guess you could either add dive flaps to the F4's and use them as bombers or deliver them as dive bombers and also do photo recon with them, or go ahead and build F4 recon aircraft.

When I said the "50 delivered to Pearl by February 1" I meant February 1942. It sounds like you are thinking I meant 1941.

It is not "some elaborate trap" at Midway. I would simply be replacing the unescorted Dauntless and Vindicators with something that had a prayer of getting through the Zero CAP and hitting the carriers instead of just giving the Zero's some live gunnery practice.

A Vindicator might be a great plane to train in, but actually flying it, unescorted into the Zero CAP of 4 Japanese fleet carrier's is akin to playing Russian Roulette with all the chambers loaded. We didn't know if Pearl Harbor would be attacked again or not, that is why I would have deployed these P38's at Pearl Harbor to train. When the Midway situation arose, it would have been a simple matter, with drop tanks, to let them self deploy to Midway just before the battle just as they did with the B17's, B26's and Avenger torpedo planes. If flown by well trained crews, such as the carrier based navy dive bomber pilots that actually sank the 4 Japanese carriers at Midway then I think they had a great chance of doing the same thing without the needless slaughter that happened to the guys that tried it in the Dauntless and Vindicators.

One shot deal? Great amounts of hindsight or retrospect? Not really. Someone says 'we have a big fast fighter that could carry a bomb, add dive brakes and use it for dive bombing' (I mean come on, the first P51's/A36's had dive brakes and were used as dive bombers so it isn't a huge stretch) They are training at Pearl Harbor and also there in case of another Japanese attack. They get deployed to Midway because they are there and they can. After the battle they fly back to Pearl Harbor. They would have a been a great help at Guadalcanal as well with drop tanks, being able to attack japanese carriers at great distance and having the speed to avoid the Zero CAP and accuracy of a dive bomber to actually hit the target, unlike B17's.

The chances - real world - of the USN getting any allocation of F4/P-38E/P-38F/P-38G were literally zero. Until the P-47C was operational in very late 1942 there simply was not another Interceptor deemed combat worthy for the purposes of Air Defense. Every Theatre in the US Army Command placed the highest delivery priority for P-38s because of range and high-low altitude performance. Until the dive flaps, first into combat in summer 1944, the P-38 was uncontrollable in a dive. The combat radius with bombs on was around 100 miles. The complexity of introducing an arresting hook on the fuselage boggles the mind, reorienting USN philosopy to avoid in-line engines and the necessary Prestone/coolant liquids detracts from the volume available for aviation gas.

Usually only a couple of barriers is all that is needed for AAF/USN to go their separate ways but each one on the list is a concept killer.

 

[Shortround6]

We have a number of issues.

Under technical feasibility;

1. Can you even modify a P-38 to undertake the specified mission?
2. How extensive is the modification?
3. Can the modification be done to existing aircraft in field work shops?

under financial considerations;
4. Do you have the money to pay for this program before Pearl Harbor?(funding was not unlimited after Pearl Harbor but there was a lot more money than before Pearl Harbor)
5. What other Army Attack aircraft might be cut from the budget to pay for it?

Tactical considerations

6. without using the retrospectroscope how much is the A/P-38 dive bomber going against then current Army doctrine?
7. Is it really going to work the way the proposal claims?


Addressing 1 and 7 the Dauntless achieved it's accuracy in part due to the dive angle it used and the dive speed it used. Dive angle gets a bit confusing as the dive attitude of the plane (angle of the planes axis from the earth's surface ) and the angle of the dive path are not the same for most aircraft. Due to the wing providing lift the planes path is is being displaced in an "upwards" direction (in relation to the canopy/pilots head). Unless you can get the modified P-38 to dive at pretty close to the same angle and speed as the Dauntless you will have poorer accuracy even using the same pilots. The 250mph dive speed with brakes out allows for more time to correct aim and for a low altitude pull out. Most fighters, even they dove at a steep angle had to release their bombs and start their pullout several thousand ft higher than true dive bombers. Putting dive brakes on a P-38 may allow you to get closer to the Dauntless dive characteristics but are you going to match them? A 20% increase in dive speed (to 300mph) means a 44% increase in the energy the plane has and much more than just a 20% higher altitude pull out.
An SBD actually has a wing with 1% of the area of a P-38 wing.

The P-38 used Fowler flaps which increased the wing area when deployed. You might have a lot trouble attaching dive brakes to the existing flap mechanism.

The flaps moved back, and then started to angle down and it the final travel were angling down much faster than they were sliding rearwards.
Messing with the P-38s flaps is not going to help it's landing (or even take-off ) performance. I am not sure how well landing flaps full of holes work

Maybe you can use something like the dive brakes used on the A-36.

It leaves the existing flap arrangements alone. Lets also remember though, that the A-36 was pretty much a funding trick to keep North American's workforce intact and help fund factory expansion. The Army had no more money for fighters but had left over money for Attack Aircraft (dive bombers?) in the budget. However I doubt that a small set of fences/slats are going to give the speed reduction needed on a P-38 to get the bomb release altitude down to were you need it to rival the Dauntless.

Please note the Army had purchased a small quantity of Dauntless in Sept, 1940 (delivered starting June of 1941) and they ordered more (or joined navy orders later). By Dec of 1940 the Army had also placed an order for 100 A25-A ( Army Curtiss Helldiver) although these would take quite a while to show up. The whole A-25 saga is long and sad. You still had dive bomber advocates fighting it out with level bombing advocates.
I would note that a Curtiss Helldiver was supposed to be able to"cruise" at just over 300mph while carrying a 1000lb bomb inside the bomb bay at around 14-15,000ft with engine running at max continuous (not Military) power. Range was pretty short doing this but it's ingress/approach speed wasn't too bad. This is actual performance and not estimated performance before the plane flew.

 

[Shortround6]

Usually only a couple of barriers is all that is needed for AAF/USN to go their separate ways but each one on the list is a concept killer.

The Army and the navy had tough time trying to both use Dauntlesses, Helldivers, B-25s and B-24s.
I don't know about later but early in the war the Army and Navy didn't use the same radios (among other things) which means hours of work to convert one airframe from "Navy standard" to "Army Standard"
or vice versa even if the changes didn't show on the outside and made no difference to speed, climb, range, etc.
Army didn't even use the same tires on the A-25 as the Navy did on the SB2-C including the tail wheel tire.

 

[pinsog]

The chances - real world - of the USN getting any allocation of F4/P-38E/P-38F/P-38G were literally zero. Until the P-47C was operational in very late 1942 there simply was not another Interceptor deemed combat worthy for the purposes of Air Defense. Every Theatre in the US Army Command placed the highest delivery priority for P-38s because of range and high-low altitude performance. Until the dive flaps, first into combat in summer 1944, the P-38 was uncontrollable in a dive. The combat radius with bombs on was around 100 miles. The complexity of introducing an arresting hook on the fuselage boggles the mind, reorienting USN philosopy to avoid in-line engines and the necessary Prestone/coolant liquids detracts from the volume available for aviation gas.

Usually only a couple of barriers is all that is needed for AAF/USN to go their separate ways but each one on the list is a concept killer.

Why would you want an arresting hook on a land based plane? Re-read the title.
Drop tanks in addition to the bombs to increase range.
Technically if you sink their carriers first there may be little need of interceptors.

But Shortround already said hanging the dive flaps on it wouldn't be feasible so that appears to be the end.

I suggested navy pilots because they already had well trained dive bomber pilots. After what Shortround has said about not being able to hang true dive flaps on it, I would just give it to army pilots, hang a 500 pounder on the centerline and let them do a lower level run from 5,000 feet or so.

Anyway, fun discussion

 

[GrauGeist]

For what it's worth, Pappy Gunn was having tremendous success with his B-17s and B-25s in high-speed, low-level skip bombing attacks against Japanese shipping.

His tactics gave him an advantage over dive-bombing for the fact that a dive bomber, once committed to it's bombing run, is completely vulnerable to enemy CAP or shipboard AA.

Pappy's skip-bombers would come in low and hot, emerging out of the haze and in many cases (depending on the ship and or weapon) the ship's AA guns couldn't depress low enough to get accurate fire on them.

 

[Shortround6]

You might be able to get true dive flaps (or larger ones than the A-36 used) but it is not going to be a field refit with a parts kit.

The Dauntless used the perforated flaps to land

But how flaps actually worked (what they did aerodynamically) actually varied quite a bit. On a lot of planes they simple added lots of drag and steepened the glide slope.
Early Hurricanes and Spitfires worked this way. They did not provide any extra lift. The Flaps on the P-38 did provide extra lift.
I am guessing the lower flaps on the Dauntless acted as drag flaps for landing (when landing the upper sections stayed down.) With most of the fuel gone a Dauntless had a wing loading in the Mid 20lb/sq/ft area, even carrying a 500lb bomb back on board is only going to change things by about 1 1/2 lb/sq/ft.

A P-38 has to be running awfully light to get under 40lbs/sq/ft.


And if you have to slow down to somewhere between 250-300mph to bomb accurately (or pull out without hitting the ground or water) it doesn't matter if you did approach the target at 330mph +. You are just as vulnerable to AA and CAP fighters once you start the dive and for 1-2 minutes after pulling out as the regular dive bombers while you accelerate back up to speed.

 

[GrauGeist]

Something else to consider: *if* Dauntless-style dive flaps were applied to the A/P-38, how would the flap's surface (retracted) affect the airspeed?
The Dauntless' dive flaps had baseball sized holes in it (as seen in the photos posted above) and when retracted, the irregular surface would not lend to clean airflow.

 

[special ed]

In post 11, the comment "we have a big fast fighter that could carry a bomb" didn't work too well for the Me-262.

 

[wuzak]

Maybe they could have converted the Fowler flaps to the Fairey-Youngman type flaps, which could double as dive brakes.

That would, however, possibly lead to a loss in performance in the fighter role.

 

[Ivan1GFP]

There is another very basic problem with the idea of using a P-38 Lightning airframe as a dive bomber and I believe Shortround6 has already hinted at it.
Note what happened when the A-36 got its dive brakes. The stress of deploying those dive brakes was high enough that some aircraft hand wing failures and eventually the dive brakes had to be wired shut.

The SBD Dauntless was actually stressed for much higher G than a typical fighter. This was an advantage that Swede Vejtasa used when he managed to dogfight and win against A6M2 fighters that had every other advantage.
This kind of G is expected when pulling out of a dive after dropping a bomb.
Stuka pilots even had a device to ensure a successful recovery even if the G load blacked out the pilot.

If the P-38 is designed to the typical 8G maximum load with ultimate failure at 12G, it needs a lot of beefing up and structural redesign for use as a dive bomber.

Yet another factor to consider besides the Dive RECOVERY Flaps not having been invented yet for the P-38 is that even when they did exist, they were not intended for a controllable vertical dive. They were intended to Recover from loss of control (Nose Tuck or pitch down) due to compressibility effects and would pitch the aircraft up.

Even on the draggy SBD, a dive bombing run would typically result in speeds in the 400 MPH range (IIRC) when goin vertical,
On a nice sleek aircraft like the P-38, a LOT bigger Dive Brakes would be needed to keep the speed down especially considering that the Compressibility Limit for the P-38 airframe isn't very high to begin with.

- Ivan.

 

[GrauGeist]

In regards to the A-36's brakes being wired shut, this has grown into somewhat of a myth.

The only time the brakes were wired shut, was with a training unit state-side. The brakes were wired shut until modifications could be made to strenghten the hydraulic actuators.

In the case of wing failure, this was due to an accumulated dive speed in excess of 450 mph and the result was a restricted dive angle not to exceed 70° with a release altitude between 2,000 and 4,000 feet depending on target environment.

A great book that covers the A-36 (including the brakes issue) in great detail, is "Fighting Mustang: the Chronical of the P-51" by William Hess.

 

[pinsog]

In post 11, the comment "we have a big fast fighter that could carry a bomb" didn't work too well for the Me-262.

You are correct, the Me 262 didn't do well as a fighter bomber. Didn't a pair of 550 pound bombs drop it down below the speed of Mustangs and Thunderbolts?

I believe a P38, especially above 15,000 would still outrun a Zero while carrying a single 500 or 1000 pound bomb

 

[P-39 Expert]

I think this could be a viable mission. Most on here know that I am no fan of the P-38, but I believe it could:

Cruise a long way at high speed at 25000' especially with a 300gal drop tank on one pylon and a 1000# bomb on the other. I know tanks would cross-feed, but would the one external tank feed both engines at the same time?

The actual dive bombing would need to be done at a relatively low altitude after dropping the empty tank. And certainly not at the angles that SBDs dove at, much more shallow, almost glide bombing. P-38s (and P-39s) conducted sporadic dive bombing missions with good results with little or no training after planning it the night before. With Navy dive bomber training their accuracy should improve greatly.

If they survived the dive and release then they could cruise on home at high altitude/high speed making Japanese interception difficult.

But rigging up a P-38F/G with some kind of dive flap/brake in order to dive near vertically from 25000' to accurately deliver a bomb would not be a mission I would want to be assigned.

 

[drgondog]

There is another very basic problem with the idea of using a P-38 Lightning airframe as a dive bomber and I believe Shortround6 has already hinted at it.
Note what happened when the A-36 got its dive brakes. The stress of deploying those dive brakes was high enough that some aircraft hand wing failures and eventually the dive brakes had to be wired shut.

Not quite so. The structural failures were caused when the pilot failed to follow specific NAA pilot handbook instructions to ONLY open dive brakes Before initiating the dive. As for second claim - partially true as AAF suggested that they be wired shut, but most combat pilots in 27th, 86th and 311th ignored the advice and achieved excellent results. The first structural failure of the wing was traced to a.) opening dive flaps After initiating dive run with 2x500 # bombs, b.) entering a dive that exceeded 90 degrees when pilot was trying to get a/c back on target, c.) attempting to roll out to recover (at approx. 380mph TAS) and d.) pulling estimated 15G's. Usually one of those will hurt you.

The SBD Dauntless was actually stressed for much higher G than a typical fighter. This was an advantage that Swede Vejtasa used when he managed to dogfight and win against A6M2 fighters that had every other advantage.
This kind of G is expected when pulling out of a dive after dropping a bomb.
Stuka pilots even had a device to ensure a successful recovery even if the G load blacked out the pilot.

If the P-38 is designed to the typical 8G maximum load with ultimate failure at 12G, it needs a lot of beefing up and structural redesign for use as a dive bomber.

True - but like the Mustang the 8G/12G was for Gross Weight of the Initial design XP-38. By the time 1943 rolled around the limit loads were closer to 6+ G with full internal fuel.

Yet another factor to consider besides the Dive RECOVERY Flaps not having been invented yet for the P-38 is that even when they did exist, they were not intended for a controllable vertical dive. They were intended to Recover from loss of control (Nose Tuck or pitch down) due to compressibility effects and would pitch the aircraft up.

Even on the draggy SBD, a dive bombing run would typically result in speeds in the 400 MPH range (IIRC) when goin vertical,
On a nice sleek aircraft like the P-38, a LOT bigger Dive Brakes would be needed to keep the speed down especially considering that the Compressibility Limit for the P-38 airframe isn't very high to begin with.

- Ivan.

The structural requirements for dive bombing did result in beefing up the NA-83 wing test bed for the production of the A-36. Successful dive bombing tests were carried out by Chiltion with 1000 pound bombs - the the AAF did issue a memorandum to restrict the load to 500 ponders.

The structural mods were carried forward to the P-51A, then beefed up again to accommodate 10,12, 15 degree aileron deflection for the P-51B-1 (from 10 degrees only for all previous Mustang versions)

 

[drgondog]

I think this could be a viable mission. Most on here know that I am no fan of the P-38, but I believe it could:

Cruise a long way at high speed at 25000' especially with a 300gal drop tank on one pylon and a 1000# bomb on the other. I know tanks would cross-feed, but would the one external tank feed both engines at the same time?

Not as designed but doable - that said, even the initial P-38J-15 switch controls for fuel selection in cockpit for the 55 gallon leading edge tanks was a Kluge. The asymmetrical load of taking off with a 300 gal (1900 pound) tank on one side and a 1000 pound bomb on the other, lends a new nuance to 'awkward'. Op procedure would limit TO conditions to 150 gallons and then constant and increasing trim needs to be applied as fuel is drained. When the tank is punched the yaw forces would increase even more due to the drag of the bomb. The cruise speed would be perhaps 40mph less due to the combination of control trim and bomb. Entering a dive in that condition lends another nuance to 'awkward' and perhaps 'extremely dangerous' to the pilot's lexicon. Now try to conceive holding the pipper on the target from the yawing airplane at high speeds while one hand on rudder trim?

Change the definition from Doable to Infeasible?

The actual dive bombing would need to be done at a relatively low altitude after dropping the empty tank. And certainly not at the angles that SBDs dove at, much more shallow, almost glide bombing. P-38s (and P-39s) conducted sporadic dive bombing missions with good results with little or no training after planning it the night before. With Navy dive bomber training their accuracy should improve greatly.

Glide bombing not very accurate with asymmetrical forces either... or with completely trimmed airplane. Would love to see statistics for glide bombing (without napalm) on targets smaller than a football stadium under best of circumstances?

If they survived the dive and release then they could cruise on home at high altitude/high speed making Japanese interception difficult.

Imagine the mission briefing as this tidbit is conveyed to the 'eager' pilots who are designated to fly the mission?

But rigging up a P-38F/G with some kind of dive flap/brake in order to dive near vertically from 25000' to accurately deliver a bomb would not be a mission I would want to be assigned.

For Any of the above reasons, it is a mission that Never would be designed for.

 

[special ed]

If you want to use a P-38 for bombing, skip bombing is better suited. My ex father in law told me something I had never read. He was a 19th bomb group crew chief, top gunner, and explained some pilots used the B-17 for skip bombing. Those so inclined, painted two white lines on the pilot's half of the windshield, one for 500 pound and the other for 1000. When the proper white line for the bomb size was on the ship's waterline, at the set speed, and the ship filled the window, the bomb was released.

 

[Barrett]

(Quote about Thach did not transfer.) FWIW: actually Thach shot down 3 e/a (two shared) during Lexington's 20 Feb thrust toward Rabaul (Butch O'Hare figured prominently.) So Midway was not repeat not his first combat.

 

[Kevin J]

Dumbest idea I ever came across. If I was flying a dive bomber then I'd want a big chunky radial in front of me, not a twin with liquid cooled engines and leading edge condensers.

 

[Shortround6]

leading edge condensers

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