Fast bomber for USAAC: how would've you done it?

[davparlr]

I do not think any of the above configurations offered near the performance potential as the XB-42 type pusher.
• Empty weight 20,000
• Max takeoff weight 37,000
• Power plant 2 x V-1710-49/53 1325 hp at take off, 1150 hp at 25,000 ft.
• Max speed 380-390 mph at 27,000 ft, 310 mph at SL
• Cruise speed 312 mph
• Range w/bomb load 1800 mi.
• Bomb load 8000 lb
Built with basically off-shelf-technology, this plane, in 1942, would be faster than the Mosquito, carry a heavier load farther than a B-17E, and would be nearly or as fast as the Bf-109F/G and Fw-190A-3 at 27k. It certainly would have a formidable capability.

 

[tomo pauk]

If you want 1710-49/53 on-board, those can make 1325 HP @ 25,000 ft @ MIL. Those being turbocharged, still think Packard Merlins would've been better choice.

Just wondering, how good would've been a single-engined pusher, with the biggest available radial mounted? That means 1700 HP in 1941, 1850 early in 1942, 2000 later in 1942 atc? Sorta child of Northrop Black Bullet and Douglas Mixmaster?

 

[wuzak]

If you want 1710-49/53 on-board, those can make 1325 HP @ 25,000 ft @ MIL. Those being turbocharged, still think Packard Merlins would've been better choice.

Just wondering, how good would've been a single-engined pusher, with the biggest available radial mounted? That means 1700 HP in 1941, 1850 early in 1942, 2000 later in 1942 atc? Sorta child of Northrop Black Bullet and Douglas Mixmaster?

I would think you would need two radials, unless you use an R-4360.

The Black Bullet performed way below expectations. Part of that was due to the engine installation. Not sure how two fat radials will fit inside the Mixmaster and get cooling air. Note that in the XP-56 the R-2800 had to be backwards in order to drive the pusher prop, and that P&W had to redo the cooling arrangements, as the air flow was back to front and had to use a fan. It also took some time for P&W to come up with the drive arrangement (probably because they were ever so slightly busy at the time).

 

[wuzak]

I do not think any of the above configurations offered near the performance potential as the XB-42 type pusher.
• Empty weight 20,000
• Max takeoff weight 37,000
• Power plant 2 x V-1710-49/53 1325 hp at take off, 1150 hp at 25,000 ft.
• Max speed 380-390 mph at 27,000 ft, 310 mph at SL
• Cruise speed 312 mph
• Range w/bomb load 1800 mi.
• Bomb load 8000 lb
Built with basically off-shelf-technology, this plane, in 1942, would be faster than the Mosquito, carry a heavier load farther than a B-17E, and would be nearly or as fast as the Bf-109F/G and Fw-190A-3 at 27k. It certainly would have a formidable capability.

That would make it about as fast as a Mosquito BIV, albeit with a larger load and longer range. But it is a substantially larger airframe.

 

[tomo pauk]

I would think you would need two radials, unless you use an R-4360.

The Black Bullet performed way below expectations. Part of that was due to the engine installation. Not sure how two fat radials will fit inside the Mixmaster and get cooling air. Note that in the XP-56 the R-2800 had to be backwards in order to drive the pusher prop, and that P&W had to redo the cooling arrangements, as the air flow was back to front and had to use a fan. It also took some time for P&W to come up with the drive arrangement (probably because they were ever so slightly busy at the time).

But, I've specified 'one radial'
Last time Black Bullet was discussed here, no cooling problems were mentioned - none were encountered, hence P&W and Northrop were doing a good job re. cooling?

Anyway, a 2-man crew, hull akin to Avenger (TBM; crew in front, one behind another, bomb bay fuel tank at center, divided by wing spars, engine aft) wing of the size shape as Hellcat's (or P-47's wing look-alike, for really high speed) and here we go

A light/attack bomber to complement the heavier ones.

 

[wuzak]

In the XP-56 the airflow was back to front for the R-2800. The flow came in from the supercharger end of the engine and exited near the nose case. It could not be done with normal ram air (like on conventional aircraft) and required an engine driven fan to work. I can't recall if the XP-56 had issues with cooling, but the cooling flap exits, the wing/fuselage interface and the shape of the fuselage (because of the size of the radial engine and its closeness to the tail) were suspected of creatin turbulence in front of the prop, destroying the efficiency of the prop and reducing the top speed from the predicted over 400mph to in the low 300s.

 

[tomo pauk]

Hmm, then 'my' bomber would have to include cooling fan too, but also a geared elevated (so the prop is not about to hit the land) drive shaft (5-6 ft long?). Also, the exit duct should not be annular anymore, but bifurcated, or, maybe, channeled under the hull, so the cooling air is as much away from the prop disc as possible?

 

[wuzak]

I think for the bomber the engine would further away from the prop and the extension shaft longer. Which would make the problem less.

But I still think you'll end up with an unacceptably fat fuselage.

 

[tomo pauk]

Max width of Avenger's fuselage was 60in - 5ft. That's not too fat

 

[Conslaw]

I agree that the A-26 was the ape of twin-engined bombers. What I would have done differently is cleared all of the crap out of the procurement process. That plane should have been widely available by early 1943. Whereas the AF moved heaven and earth to get the B-29 in production despite its faults, they kept fiddling with the A-26 before moving it into large scale production.

 

[Conslaw]

apex not ape, sorry.

 

[timmy]

I always wondered if Bell could have placed a couple of small Radials (R-1830 ?) in the front of the Bell Airacuda Nacelle's
To make it a 4 engined high speed bomber in the push/pull configuration

Better than those stupid manned cannon pods

 

[Shortround6]

I am still baffled by why people think the "push-pull" concept is so great. In the Do-335 they got it to work with props over 40 ft apart. In a number of aircraft built from WW I into the mid-30s with much less distance between the propellers they found the rear prop suffered in efficiency due the disturbed air from the front prop. More often than not the rear engine had cooling problems to boot. Front engine planes have a certain amount of cool/cold air flowing through the engine cowling helping to cool off spark plugs, magnetos and a few other accessories (in fact some planes have specialized small scoops directing airflow at some of these components.) the rear engines in some push-pull configurations suffered from not having this cooling airflow which is different from the airflow through th e radiators and oil coolers.

 

[timmy]

I am still baffled by why people think the "push-pull" concept is so great. In the Do-335 they got it to work with props over 40 ft apart. In a number of aircraft built from WW I into the mid-30s with much less distance between the propellers they found the rear prop suffered in efficiency due the disturbed air from the front prop. More often than not the rear engine had cooling problems to boot. Front engine planes have a certain amount of cool/cold air flowing through the engine cowling helping to cool off spark plugs, magnetos and a few other accessories (in fact some planes have specialized small scoops directing airflow at some of these components.) the rear engines in some push-pull configurations suffered from not having this cooling airflow which is different from the airflow through th e radiators and oil coolers.

I always wondered why they never went push/pull for bombers..now I know.

 

[GrauGeist]

The XB-28 would have probably fit the bill as a twin-engined, high-speed bomber.

It was powered by two P&W R-2800-27 engines, carried a 4,000 (1,800kg) payload and had a top speed of 372mph (599kph). It had an empty weight of 25,575lbs. (11,600kg) and a loaded weight of 35,740lbs. (16,210kg). With a pressurized cabin, it was capable of a max altitude of 33,500ft. (10,213m) with a range of 2,040 miles (3,280km).

The design called for a crew of 5 and had remote controlled top, belly and tail turrets, but these could have been removed to save weight and improve speed.

Even though the XB-28 was offering superior performance, it had been designed for high-altitude bombing and was cancelled in favor of other, existing medium and high-altitude bombers.

 

[tomo pauk]

It is interesting to see how much of 'useful load' the P-38J has been able to lift in the air with 2 x 1425 HP for take off. 620 lbs of guns and almost 7000 lbs of fuel. In case max fuel was carried, no ammo was aboard (up to 610 lbs worth)? I'd love to see a 'classic twin (ie. not a twin boom design) with a decent bomb bay.
7600 lbs of payload can be divided in several ways. 3600 lbs of fuel is 600 US gals, 4000 lbs for bombs. When carrying the cookie (4000 lbs), the Mosquito carried 500 imp gals of fuel - 600 US gals. Engine power 2 x 1390 HP for TO.* The A-20G-20 was carrying 725 US gals and 2000 lbs of bombs, total 6350 lbs. Or 400 US gals and 4000 lbs, total 6400 lbs.
The early turbo V-1710s were good for 1150 HP for take off, so the payload would be cut down, maybe 5500-6000 lbs total. Once 1325 HP for TO is available/allowed (summer of 1942), the payload can be upped to 6500-7000 lbs. The low-tech (ie. no 2x turbo - saves 600+ lbs - a better better than turbo until mid 1943) version would be also good - 1150 HP from early 1941, 1325 HP from mid 1942. Should be also cheaper than turboed versions, easier to produce and purchase, so the Allies can use them, too.

*later versions also carried 2 x 500 bombs on 2 x 1390 HP for TO. B.Mk.XX

 

[m37b1]

This is an interesting topic. One that I've pondered many times. I'd say the best move would have been to upgrade the Martin B-26.
Turbocharged P&W -2800-59 series (2300-2800 HP), making it a high altitude/high speed bomber.
Additionally, the nacelles could have been cleaned up, ducting all cooling air and exhaust out the back as was done with the Republic XF-12. (Main gear would have to be changed. Maybe bicycle, like the B-26H? Or into the side of the fuselage, like an amphibian?)
Additional clean up could have been achieved with a streamlined top turret, as that tech became available, and removal of the blister guns.

A couple of questions about the actual B-26.
First: Why was it so slow to begin with? Best speed I've ever seen listed is, 326 mph. Seems the the sum of the parts should be faster.
Second: I once read that it had a much heavier gauge sheet aluminum used for it's skin than other bombers. This was detailed as one of the reasons it had a low loss rate. Anyone know the details of this?

 

[Shortround6]

It is interesting to see how much of 'useful load' the P-38J has been able to lift in the air with 2 x 1425 HP for take off. 620 lbs of guns and almost 7000 lbs of fuel. In case max fuel was carried, no ammo was aboard (up to 610 lbs worth)? I'd love to see a 'classic twin (ie. not a twin boom design) with a decent bomb bay.
7600 lbs of payload can be divided in several ways. 3600 lbs of fuel is 600 US gals, 4000 lbs for bombs. When carrying the cookie (4000 lbs), the Mosquito carried 500 imp gals of fuel - 600 US gals. Engine power 2 x 1390 HP for TO.* The A-20G-20 was carrying 725 US gals and 2000 lbs of bombs, total 6350 lbs. Or 400 US gals and 4000 lbs, total 6400 lbs.
The early turbo V-1710s were good for 1150 HP for take off, so the payload would be cut down, maybe 5500-6000 lbs total. Once 1325 HP for TO is available/allowed (summer of 1942), the payload can be upped to 6500-7000 lbs. The low-tech (ie. no 2x turbo - saves 600+ lbs - a better better than turbo until mid 1943) version would be also good - 1150 HP from early 1941, 1325 HP from mid 1942. Should be also cheaper than turboed versions, easier to produce and purchase, so the Allies can use them, too.

Designing with hindsight?

You KNOW you will get a 1425hp engine in early 1943 so you design and build a bomber in 1939-41 using 1150hp engines so you will be ready when the 1425hp engine shows up?

Payload of the P-38 was actually higher as there were several hundred pounds of guns mounts, bracing, ammo boxes and chutes, of course the P-38 was a single seater and the "bomber" should have a crew of at least two so you add back in 200lbs for the second crewman and ????pounds for his work space (the piggy back arrangement used by P-38 night fighters was hardly suitable for a bombardier/navigator).

Your estimate includes 620 gals of fuel carried in 310lbs worth of drop tanks. To get the fuel (or bombs) inside you need a bigger (much bigger) fuselage and/or wing (combining the two booms won't quite get you there)

There is not a lot of "boom" once you get passed the landing gear bays and radiators.

How big is the desired bomb bay?
we have been over this before and while a 4000lb "cookie" can fit into a rather small bomb bay six 500lb bombs do not.

Without the turbo the proposed plane falls well behind the Mosquito. The 1325hp take-off version Allison falls to 1150hp at 12,000ft and there is no hope of WER at that altitude. Merlin XX/21/V-1650-1 gives 1240hp/11500ft/9lns boost in low gear or 1120 hp at 18,500ft. Using 16lbs boost on the Merlin the and Allison has about 80% of the power of the Merlin at 12,000ft or so. The Merlin can run at 1010hp at 18,000ft until the fuel runs out. An Allison with 7.48 gears and 1325hp for take-off (as used in the A-36) gives about 800hp at 18,000ft (no ram) at 3000 rpm and a max cruise of around 675hp at 18,000ft at 2600rpm.

 

[Shortround6]

This is an interesting topic. One that I've pondered many times. I'd say the best move would have been to upgrade the Martin B-26.
Turbocharged P&W -2800-59 series (2300-2800 HP), making it a high altitude/high speed bomber.
Additionally, the nacelles could have been cleaned up, ducting all cooling air and exhaust out the back as was done with the Republic XF-12. (Main gear would have to be changed. Maybe bicycle, like the B-26H? Or into the side of the fuselage, like an amphibian?)
Additional clean up could have been achieved with a streamlined top turret, as that tech became available, and removal of the blister guns.

A couple of questions about the actual B-26.
First: Why was it so slow to begin with? Best speed I've ever seen listed is, 326 mph. Seems the the sum of the parts should be faster.

The -59 engine didn't go much above 2300-2500hp and that was with water injection, the 2800hp engines were "C" series engines and don't show up until late 1944.

B-26 had enough trouble landing without trick narrow track landing gear. Proof of concept landing gear is one thing, using it in service on crappy airstrips in bad weather is another thing.

Please note that the 1850hp "A" series engines were actually good for around 1500hp at 14-15,000ft and the 2000hp "B" series engines were good for 1600hp at 13,500ft. Merlins used in Mosquitoes could pull 1435-1490hp at at around 11-12,000ft if allowed to use 16lbs of boost.

B-26 was actually pretty zippy for it's size/weight in the early versions. 28,367 pounds gross, 33,022 pounds maximum. for an B-26A

 

[m37b1]

Agreed on the R2800's. If we did use the Turbo -59's development could have paralleled that of the P-47. 2800 HP "C" by late 44.

I though the same about the bicycle gear, hence the thought of alternative design.

Any thoughts on what kind of speed could have been achieved with the changes I proposed? 350 - 370 mph at 20 - 24K ft, maybe? (dependent on load).