USAF 1944: ideal multi-purpose 2-engined aircraft?

[tomo pauk]

Looking at capabilities of the USAF 2-engined combat aircraft, seems like they were hard pressed to deliver a combination of performance, punch, range and modest use of resources like Mosquito was offering. Admitedly, the USA was not that hard pressed to save the resources, so we can leave that requirement aside.
So: what should look like the feasible multi-role combat aircraft for the USAF for 1944, that wouldve used two US-built piston engines, being based on the aerodynamics construction techniques of the era, using US-built guns/bombs/radars/radios? Main jobs would be: night fighter, fast bomber, recon. The plane should beat the 400 mph mark clean for NF and bomber versions, the bomber version should carry at least 4000 lbs internally. Range of at least 1700 miles with 2000 lbs of bombs.
The design job should commence some time in 1941 so we can field the fighter with the beginning of 1944. Answers other than 'build the Mossie in the USA' are encouraged

 

[oldcrowcv63]

Grumman F7F Tigercat… JMO

400++ mph speed,
excellent climb and payload
light bomber
torpedo bomber
Nightfighter

 

[davebender]

Drop the fast bomber role. That's what A-26 is for.

F7F will work for recon and might work for night fighter if the aircraft has sufficient internal space for electronic equipment.

 

[tomo pauk]

Sorry, Dave, the rules are set

The F7F lacks the bomb bay and fuel to compete.

 

[oldcrowcv63]

VMF(N)-531 Night fighter squadron example used in Korea but original day fighter version apparently introduced in '44. Not sure of the numbers. Note RO's station behind pilot

 

[tomo pauk]

The F7F was introduced in 1945. I do love the Tigercat, but still cannot fulfill the requirements:

the bomber version should carry at least 4000 lbs internally. Range of at least 1700 miles with 2000 lbs of bombs.

The range was 680 miles with 4000 lbs bombs (1x2000 lbs + 2x1000 lbs), 1260 miles with a torpedo and 2x150 gal tanks. We can substitute a torpedo with 2000 lbs bomb (both go to the fuselage rack), but that's still circa 500 miles short of the mark. Even A-20K can reach 300 miles further.

 

[drgondog]

he XB-28 was the closest a/c the US considered in time for combat by 1943 timeframe

North American XB-28 - Wikipedia, the free encyclopedia

Not quite fast enough at 372 mph but met your other specs

 

[tomo pauk]

Looking at what J. Baugher has to say about the XB-28, and seem like only 1840 HP at hi-alt was used when XB-28 was tested (from here):

Engines: Two Pratt Whitney R-2800-11 air-cooled radial engines, rated at 2000 hp for takeoff and 1840 hp at 25,000 feet.

The P&W designation for the -11 engine was R-2800-AG - seems like either late 'A' series or early 'B' series (SR6, wuzak - help!). The XP-47B was using the R-2800-17, the P-47B/C/early D were using R-2800-21, a B series engine (2000 HP military power at 25000 ft)
About the XB-28A:

The second prototype was completed as the XB-28A reconnaissance version with R-2800-27s.

J.B does not state the speed of the XB-28A, however, neither is his surce, Ray Wagner.
So the B-28 with R-2800-21 and WI should be well capable for 400 mph? The NF version (maybe even the bomber?) would lack the turrets?

 

[davparlr]

B-42. Meets all the criteria, just start it earlier which should technologically be capable of being done. It also has a big plus in that it could replace the B-17/24 and cover the B-29. It could probably meet the criteria with less powerful engines which would be available earlier.

 

[tomo pauk]

Somehow I knew that you'd bring Mixmaster to the table

 

[Shortround6]

The plane should beat the 400 mph mark clean for NF and bomber versions, the bomber version should carry at least 4000 lbs internally. Range of at least 1700 miles with 2000 lbs of bombs.
The design job should commence some time in 1941 so we can field the fighter with the beginning of 1944.

Part of the problem is your specification.

What kind of 4000lb bomb load? A single 4000lb cookie or a single US 4000lb 'block buster' or four 1000lb bombs or eight 500lb bombs. 4000lbs worth of incendiary cluster bombs? Different sized bomb bays needed.

While you are starting your design process later than the Mosquito you are still starting it in the days of 100/125 octane fuel. And it took until the Mosquito got the 70 series Merlin engines for it to become a 400mph airplane. Range with 1000lb load was 1870 miles at 245mph using 788imp gallons (945 US gallons?).

Did the guns and gun turrets on the A-26 really cost 45-50mph in speed?
And if you use R-2800s for engines ( and what other choice do you really have) hitting 400mph+ with eight 500lbs inside is going to be quite a trick below 20,000ft. The F7F-1 just barley cracked 400mph below 20,000ft and the Mosquito MK XVI was good for around 386mph (without drop tanks) at it's peak speed below 20,000ft. In other words it was about 30-35mph faster than the A-26 at around 15,000ft.

Use R-2800s with two stage superchargers to hit 400mph above 20,000ft?



One reason the US 1600lb bomb was so popular for listing in spec sheets, it was smaller in diameter than 1000lbs, in fact it was only about 1 in bigger in diameter than a British 500LB GP bomb and a bit over 1 foot longer than the un-cropped tail fin models.

 

[davparlr]

Somehow I knew that you'd bring Mixmaster to the table

Yeah, I like the concept. It eliminates the form drag and interference drag of pod mounted multiple engines and allows clean wings. I think it was basically solid with no real breakthrough design issues. The only risk items I see are, the gear box, which is simplified due to individual engines driving individual props. This seems to have been adequately addressed. Also, cooling, which would have needed to be carefully addressed as found out by the Germans on the He 177s. Maybe a Mustang like design. Finally, maintenance issues of primarily access, which I think could be mitigated by a proper maintainability program which I am not sure existed then. All in all, I think it was technologically feasible with reasonable risk, and provides significant performance improvement possibilities.

 

[Rick65]

I thought of an earlier produced P-61C, using external bombs in bomber mode, but it doesn't have the range on internal fuel.

 

[MikeGazdik]

Blow the dust off of the A-20 Havoc. Equip it with either R2800s, or Turbo Allisons from the P-38J/L. I don't know any of its payload or range data.

 

[tomo pauk]

Yeah, I like the concept. It eliminates the form drag and interference drag of pod mounted multiple engines and allows clean wings. I think it was basically solid with no real breakthrough design issues. The only risk items I see are, the gear box, which is simplified due to individual engines driving individual props. This seems to have been adequately addressed. Also, cooling, which would have needed to be carefully addressed as found out by the Germans on the He 177s. Maybe a Mustang like design. Finally, maintenance issues of primarily access, which I think could be mitigated by a proper maintainability program which I am not sure existed then. All in all, I think it was technologically feasible with reasonable risk, and provides significant performance improvement possibilities.

An additional electric blower, that would be switched on/off with undercarriage being down/up - might help cooling the engines when on ground and when on low speed in general?

I thought of an earlier produced P-61C, using external bombs in bomber mode, but it doesn't have the range on internal fuel.

As a bomber - ditch the cannons, turret and gunner, use that space for bombs and some more fuel? The turbo-P-61 (even if not the P-61C) should be pretty fast.

Blow the dust off of the A-20 Havoc. Equip it with either R2800s, or Turbo Allisons from the P-38J/L. I don't know any of its payload or range data.

Maybe the two stage Packard Merlin (no need to install the turbo and associated plumbing), or the two stage V-1710 (somewhat less powerful than V-1650-3/7, but there is no intercooler to install)? The later A-20s were quite rangy - 2000 lbs of bombs up to 1570 miles with additional fuel in bomb bay (726 US gals total), or 4000 lbs to 710 miles on 400 gals. The V-12s should give far better mileage, but they are some 15% down with take-off power. Since we start in 1941, that would give enough time to incorporate better flap system?

 

[wuzak]

The P&W designation for the -11 engine was R-2800-AG - seems like either late 'A' series or early 'B' series (SR6, wuzak - help!). The XP-47B was using the R-2800-17, the P-47B/C/early D were using R-2800-21, a B series engine (2000 HP military power at 25000 ft)

The -11 was an A series, according to White.

Rated at 2000hp @ 25,000ft with turbosupercharger.

 

[tomo pauk]

The -11 was an A series, according to White.

Rated at 2000hp @ 25,000ft with turbosupercharger.

Thanks for checking that out. The US engines tables indeed state the R-2800-11 as a turbocharged engine. 2000 HP was achieved on 2700 rpm, contrary to 2600 rpm what other A series were doing, the reduced supercharger gearing (6.44:1 vs. 7.60:1 and higher) enabling for this?
Corrections/explanations welcomed

Part of the problem is your specification.

What kind of 4000lb bomb load? A single 4000lb cookie or a single US 4000lb 'block buster' or four 1000lb bombs or eight 500lb bombs. 4000lbs worth of incendiary cluster bombs? Different sized bomb bays needed.

Eight 500 lbers should be nice, upwards to 2x2000 lbs.
Edit: actually, 4x1000 lbs should simplify the bomb-bay, vs. 8x500 lbs. Four 500 lbs should be carried for really long distances, like above 1300 miles.

While you are starting your design process later than the Mosquito you are still starting it in the days of 100/125 octane fuel. And it took until the Mosquito got the 70 series Merlin engines for it to become a 400mph airplane. Range with 1000lb load was 1870 miles at 245mph using 788imp gallons (945 US gallons?).

With 2000 lbs in the bomb bay, it was 1795 miles with 536 imp gals internal + 100 imp gals external (763 US gals total) for the Mossie with 70 series Merlins.

Did the guns and gun turrets on the A-26 really cost 45-50mph in speed?

Don't know - more likely 15-20 mph?

And if you use R-2800s for engines ( and what other choice do you really have) hitting 400mph+ with eight 500lbs inside is going to be quite a trick below 20,000ft. The F7F-1 just barley cracked 400mph below 20,000ft and the Mosquito MK XVI was good for around 386mph (without drop tanks) at it's peak speed below 20,000ft. In other words it was about 30-35mph faster than the A-26 at around 15,000ft.

Use R-2800s with two stage superchargers to hit 400mph above 20,000ft?

Single stage engines won't cut it here.

One reason the US 1600lb bomb was so popular for listing in spec sheets, it was smaller in diameter than 1000lbs, in fact it was only about 1 in bigger in diameter than a British 500LB GP bomb and a bit over 1 foot longer than the un-cropped tail fin models.

Thanks, the 1000-lbers will doo for most of the targets.

 

[Shortround6]

US bomb sizes;



type.............................actual weight.................AOL length...................diameter.............max over tail fins.........HE Content

250lb GP AN-N57................252lb...........................47.8in...........................10.9in.................14.9in.......................122.5lb
300lb GP M31....................261lb...........................50.8in...........................10.9in.................14.9in........................-------
500lb GP AN-M64...............512lb...........................59.16in.........................14.18in................18.94in......................262lb
1000lb GP AN-M65.............999lb...........................69.5in...........................18.8in..................25.4in.......................530lb
2000lb GP AN-M66............2053lb..........................92.83in..........................23.29in................31.6in.......................1061lb
4000lb GP AN-56..............4201lb.........................117.25in..........................34.25in...............47.62in......................3245lb

500lb SAP AN-M58A1........502lb............................57.8in............................11.8in..................16.2in......................144.5lb
1000lb SAP AN-M59..........990lb............................70.4in............................15.1in..................20.72in....................303lb
1000lb AP AN MK 33......1008lb............................73in...............................12in....................16in.........................140lb
1600lb AP AN MK 1....... 1575lb........................... 83.5in............................14in....................20.6in.......................216lb

a few assorted bombs
325lb depth bomb..........325lb...............................51-53in..........................18.44in................18.44in.....................221lb
650lb depth bomb..........729lb...............................70in...............................17.7in.................-------.....................464lbs
Adapter,cluster M6........500lb (?)..........................42.78in...........................12.63in W...............14.3in H.................128 4lb incendiary
Adapter,cluster M6........500lb (?).......................... 58.88in..........................17in W....................12.8in H.................60 6lb incendiary

There are lots of other but these are the main ones.

Please note that using two 2000lb bombs side by side requires a bomb bay about one foot wider than a bomb bay sized for 1000lb bombs with the 1000lbs either behind in pairs or stacked in pairs. Granted the 4 1000 lb bombs need either a longer bomb bay or a taller one.

How big do you want that bomb bay for 4000lbs?

Please note that using two 2000lb bombs side by side requires a bomb bay about one foot wider than a bomb bay sized for 1000lb bombs with the 1000lbs either behind in pairs or stacked in pairs. Granted the 4 1000 lb bombs need either a longer bomb bay or a taller one.

B-25s could hold ONE 2000lb bomb, TWO 1600lb AP, THREE 1000lb, SIX 500lb.

 

[oldcrowcv63]

Tomo, I still think the Grumman F7F might have been developed along the lines you indicated. It was introduced as a night fighter (F7F-1N) in small numbers (34) in 43-44. An upgrade to F7F-2N appears to have been produced in slightly larger numbers (65) in '44 thru '45. If the need to meet the specs you outlined had arisen in 1941, I expect a design similar to the F7F could have evolved to meet your performance specs or come close to them.

Source:

Tigercat

 

[tomo pauk]

Cool, many thanks SR6

How big do you want that bomb bay for 4000lbs?

The A-26B was capable to hold a 1000 lb bomb on each of 4 bomb racks inside the bomb bays (=4000 lbs total), so it's bomb bay size should be okay?

edit: The 2000 lb should be a tricky bomb to install there, I agree. Maybe staggering them - the front bomb attached to the left-side rack, the rear bomb attached to the right-side rack? Racks being suitably strong, of course.

Hi, oldcrow,

Tomo, I still think the Grumman F7F might have been developed along the lines you indicated. It was introduced as a night fighter (F7F-1N) in small numbers (34) in 43-44. An upgrade to F7F-2N appears to have been produced in slightly larger numbers (65) in '44 thru '45. If the need to meet the specs you outlined had arisen in 1941, I expect a design similar to the F7F could have evolved to meet your performance specs or come close to them.

We'd 1st need a sort of a bomb bay - maybe 2 cells, one after another, each holding 2 x 1000 lb bombs one above another. Each cell having a 2000 lb bomb, or alternativelly 2 x 500 lbs bombs. Scratch carrier compatibility requirement. Use two-stage R-2800 B series, instead of single stage R-2800 C series - the C series is not available for 1944 battles.
NF version relocates fuel tanks into bomb bay, so the radar the operator can be located as historically?