A-20 with torpedoes

[muskeg13]

Rather than hijacking the similar P-38 thread, does anyone have info on adapting the Douglas A-20 for torpedoes?

I know it's alternate history, but I've wondered "what If" Hawaiian Air Force A-20 torpedo bombers had been able to follow the second wave back to their carriers? To having survived the attack, perhaps the Havocs had all been posted away to remote Barking Sands Field on Kauai to practice their torpedo skills. This would also place them closer to the Japanese fleet.

 

[gjs238]

Maybe just as well as the B-26 Marauders equipped with torpedoes performed at Midway.

 

[tomo pauk]

Soviets fancied attaching torpedoes on the A-20s. This might be a good start.

The A-20s with torpedoes would wreak havoc with the IJN carriers, provided that they are able to find them, fly close to them (the A-20s were pretty short ranged in mid 1942) and that torpedoes worked, of course.

 

[muskeg13]

Thanks Tomo. Interesting lead, and it explains why Wikipedia lists the A-20 as a torpedo plane, but I've never heard of it being used by the USAAF for that purpose. It was adapted for that use by the Soviets for their Lend-Lease aircraft, but never picked up by the USAAF. Too bad.

As for comparisons between the A-20 and the B-26 as torpedo launching platforms, I think the A-20 would have performed better. It was faster, more maneuverable and presented a smaller target profile. However, the real keys to success are properly training the operators to accomplish that mission and then properly defending them as they make their attack.

This is not to talk bad of the few B-26s that executed torpedo attacks at Midway. These brave crews who nearly succeeded, were only 4? to begin with, had only very rudimentary torpedo engagement training before having to execute this dangerous and complicated mission in combat, and they had NO, NONE, ZERO overhead fighter support.

A faster and more maneuverable A-20 may have done better, especially with more crew training on torpedo attacks.

 

[GrauGeist]

Add to the fact that American torpedoes had some of the worst performance profiles of the early stages of the war...

 

[Shortround6]

A-20G was "equipped" to carry the US torpedo (and was the Version adapted by the Russians). Perhaps earlier versions could have been adapted but the carriage of the torpedo required the removal of the bomb bay doors and the torpedo carried in a nose down position with the nose extending slightly below the bottom of the fuselage ( Soviet torpedo may have been completely external?). Slight reduction in range?

The big limitations for using the A-20 as a torpedo bomber in Dec 1941 and through a good part of 1942 was the torpedo itself. The low drop speed and low drop altitude were major restrictions. Even when dropped correctly the torpedo often ran erratically and the exploders (fuses) were also far from reliable.

 

[tomo pauk]

Soviet torpedo was carried externally, 'hanged' to the spar and supported by the fuselage, in an asymetric position. Both USSR and UK used longer (but more 'slender') aerial torpedos, making it impossible to carry those in bomb bays of most of the US bombers. People might want to check the link I've posted.
It would be interesting to know whether Soviets carried any fuel in, now vacant, bomb bay of their A-20s.

 

[Shortround6]

From Tallinn to Stockholm is 235 miles and from the Coast of Latvia (Liepaja) to Rostock Germany is 386 miles. Rostock is just over 80 miles from the current Polish border.

Russians didn't need bomb bay fuel tanks for most missions in the Baltic.

Also please remember that the A-20 could carry 140 gal in two tanks or 325 gal in three tanks in the upper bomb bay without affecting it's ability to carry bombs. These were self sealing tanks.

Four non-self sealing tanks could be fitted in the bomb bay (replacing bombs) for ferry purposes with 676 gallons and bring total allowable fuel to 1316 gallons. But since this is about 5500lbs of fuel over and above the 400 gallons in the wings ( and does not include the weight of the tanks) one might be excused for thinking that this option would not be used for combat even with external stores.
There was a Non-self sealing belly tank of 374 gals that fit on the bomb bay doors that was supposed to allow for the carriage of bombs while increasing total fuel load to 1199 gals (carriage of bombs may reduce fuel capacity.)

Weight of belly tank without fuel was 375lbs.

 

[tomo pauk]

From Tallinn to Stockholm is 235 miles and from the Coast of Latvia (Liepaja) to Rostock Germany is 386 miles. Rostock is just over 80 miles from the current Polish border.

Russians didn't need bomb bay fuel tanks for most missions in the Baltic.

Agreed.

Also please remember that the A-20 could carry 140 gal in two tanks or 325 gal in three tanks in the upper bomb bay without affecting it's ability to carry bombs. These were self sealing tanks.

Four non-self sealing tanks could be fitted in the bomb bay (replacing bombs) for ferry purposes with 676 gallons and bring total allowable fuel to 1316 gallons. But since this is about 5500lbs of fuel over and above the 400 gallons in the wings ( and does not include the weight of the tanks) one might be excused for thinking that this option would not be used for combat even with external stores.

I've remembered (here)
The 325 gal self sealing tank was introduced with the A-20G-20 ( from early 1944); it is very much likely that earlier versions received that one, too, once more were available.

There was a Non-self sealing belly tank of 374 gals that fit on the bomb bay doors that was supposed to allow for the carriage of bombs while increasing total fuel load to 1199 gals (carriage of bombs may reduce fuel capacity.)

Seems like that before the 374 (or 375) gals tank, the one with 342 gals was used. The 374 gal tank was probably introduced with the G-20 sub-variant.
The British list the bomb load of 2000 lbs when 605 imp gals (725/726 US gals) was carried, ie. wing tanks for 400 US gals and bomb bay tank with 325 US gals. Extra ~470 US gals would mean extra 2840 lbs of weight - very unlikely that any bomb would be carried while 1199 US gals was aboard. In case 4000 lbs of bombs was carried, the fuel was 400 gals only.

Weight of belly tank without fuel was 375lbs.

Thanks.

 

[Shortround6]

The upper bomb bay tanks rather take away the need for extra in wing tanks on the A-20. Initial French and American bomb bay design called for numerous small bombs in tubes arranged vertically and for the bomb to clear the tube/s before hitting the slipstream. Larger bombs would be carried below the tube arrangement which made for a tall bomb bay. British wanted horizontal bombs only and due to the greater length of the British bombs the bomb bay had to be extended about 1 foot.
Plenty of room in the upper bomb bay area were the tubes used to be for fuel tanks without redesigning the wing.

 

[tomo pauk]

Didn't know that British requirement - thanks for sharing that.

The upper bomb bay tanks rather take away the need for extra in wing tanks on the A-20.

You know me...

 

[Shortround6]

You know me...

AN A-20G was good for about 10,000lb payload from empty to max overload. More normal combat loading's were closer to 24,000lbs rather than the almost 27,000lb overload. 7000lbs pay load? 400 gallons is 2400lbs. crew 600lbs, 23 US gallons of oil per engine, guns ( A-20 G could have 9 .50 guns) ammo ( 3300 rounds if 6 50s in the nose (990lbs?) etc. 2000lb bomb load? even another 140 gal is 840lbs and 325 gals is 1950 lbs (not including weight of the tanks.)

 

[davebender]

This problem has little to do with aircraft types.

USN and US Army had a huge fight over whether USN could have land based maritime attack aircraft. US Army won the fight. However US Army didn't take the mission seriously. Hence WWII era USA had nothing comparable to IJN 11th Air Fleet.

If USN had been allowed land based maritime attack aircraft the A-20 would have been a good choice if it could carry enough internal fuel. Otherwise the relatively long range B-25 might be a better choice even though aerial performance (and survivability) were considerably worse. Of course USN would also need to take aerial torpedo development seriously. Otherwise the USN maritime patrol bomber would be reduced to using bombs only.

 

[Shortround6]

The A-20 would have been a lousy land based maritime attack aircraft for the US and quick glance at the Japanese aircraft will show why. They had much bigger wings and much normal fuel capacity, this meant lower speed but you can't have everything.

 

[tomo pauk]

The A-20 with bomb load of 2000 lbs and extra 325 gals in bomb bay have had the range of 1500+ miles (with 75-80 gals of allowance). The US aerial torpedo weighted about 2000 lbs. So in case the USAF and Douglas are quicker to introduce a good bomb bay tank, the capability is surely there.
Yet, the B-25 might be closer to the Japanese A/C, but sturdier than those.

 

[Shortround6]

Early B-25 was supposed to go 2000 miles with a 3000lb bomb load. Given the size of the United States and the size of it's coast line and overseas "possessions" (Panama Canal, Caribbean Islands, Pacific Islands, etc) which plane gives the most "coverage" ( covers the most area with the same number of planes)? Given that prewar (PH for the US) and early war the primary search device was the eyeball, MK I using a plane that several more sets of said 'devices' for maritime patrol would be an advantage. Given that even a Martin B-10 could exceed the drop parameters of the MK XIII torpedo on the attack run what advantage does the A-20 have?

 

[tomo pauk]

Problem was the torpedo, not the aircraft. I'm not trumpeting the A-20 as a king of torpedo planes anyway.
It was a mistake, however, that fuel loads of 700-750 gals were not introduced once the DB-7 moved on from R-1830s to R-2600s.

 

[Shortround6]

Perhaps, but I don't know what modifications were made to the A-20 as it progressed, but the gross weight went from 17,031lbs on some of the R-1830 models to 19,322-19,750lbs on the early R-2600 models to 21,000lbs on the B C (with 23,800-24,500lb max overload) to 24,000lb on the G (with 27,000-30,000lb max overload) with the G,J &K getting 1700hp engines and 27,000lb max overload.
I don't know what allowed the higher weight ratings of the later models. Structural strengthening? different tires? different brakes? different landing gear struts?
Since the early R-2600 powered planes gained 2274 to 3600lb of empty weight and only gained 2300-4000lbs of normal gross weight there doesn't seem to be any allowable weight for a big increase in fuel until the higher weight ratings came along.

For all I know it was a "paper" exercise, a recalculation of the structural strength after the plane had been in service for a while. There were changes in structure between the R-1830 and R-2600 versions. But I am not sure any of the older planes were allowed to operate at the new, higher weights ( at least officially?).

 

[tomo pauk]

I don't know what allowed the higher weight ratings of the later models. Structural strengthening? different tires? different brakes? different landing gear struts?

I don't know either. J. Baugher lists empty weights like this, in lbs; quotes are also form his site:
-A-20A: 15,165
-A-20B: 14,830 (delivered from late 1941 to early 1943)
-A-20C: 15,625 (in production from early 1941 ??; from J.B:"he last 433 A-20C production aircraft were fitted with an extra 140-gallon self-sealing fuel tank in the bomb bay, which raised the total fuel capacity to 540 gallons. All A-20Cs could be fitted with a ferry tank underneath the belly."
-A-20G: 17,200 (= Boston IV; 1st A-20G was delivered in Feb 1943; "With production block A-20G-20-DO.... Also introduced on block -20 was a pair of bomb racks stressed to carry 500-lb bombs underneath the outer wing panels. Internal fuel capacity was increased from 540 US gallons to 725 gallons, and provision was made for the mounting of a 374-gallon drop tank underneath the fuselage.", seems all were with 1600 HP engines; then this: "1675 hp war emergency"??; improved armament)
-A-20J: 17,117 (a rework of the -G, to serve as formation leader for the -Gs; 4 crew members)
-A-20K: 17,266 (Boston V; the only version with 1700 HP engine?; worse mileage than Boston IV)

 

[davparlr]

Maybe just as well as the B-26 Marauders equipped with torpedoes performed at Midway.

The B-26 performed quite well as a torpedo bomber at Midway. Three of the four bombers made it to torpedo dropping distance to the carriers, one flying down the deck of the Akagi strafing the carrier. Two of the four make it back to base, although barely. And, as mentioned before this was without any escort support. The crews were surely poorly trained although incredibly brave and the torpedoes were despicable. According to "Shattered Sword" the B26s were blazingly fast and difficult to bring down.

The A-20s were faster than the Zero, certainly below about 15k ft. If they could a accommodate a streamlined semi-conformal torpedo that could be dropped at 200 mph and a reasonable height, and worked, it could have been devastating against the Japanese. Extended range would have certainly been helpful/required.