Fast bombers for 1938-42

[wuzak]

Should be faster. The V-3420 was not a thing in this timeframe, though.

It was and wasn't. Prototypes were being built in this timeframe.

I should have said that the early V-3420s had 2,300hp, not 2,600hp as I said earlier.

OTOH - how about a DB-7 with V12 engines?

Could do well. V-1710 with low altitude rating would make for a fast low level bomber.

 

[tomo pauk]

Could do well. V-1710 with low altitude rating would make for a fast low level bomber.

V-1710 made much better power than what the French-used DB-7s had with their R-1830s. These DB-7s were making 300 mph, and were noted as survivable in the demanding environment of West Europe in May-June 1940. British received better R-1830s for some of their DB-7s, I'm not sure about the speed figures of these.
The V-1710s add more power at any flying altitude, will cut a bit of the drag and add more exhaust thrust. They will also add more weight.
A Merlin is even better bet, although the availability is tricky. Turboed V-1710 or R-1830 again offer better performance.

 

[tomo pauk]

To move away from the West, let's take a look at the East.
Yokosuka made the D4Y, a fast bomber on engine no better than DB 601A. Good for ~335 mp/h, with excellent range, although fragile due not having the self-sealing tanks in a heavily contested environment. With better engines, it did ~360 mph. Carrier- and dive-bomb capable, with Fowler flaps.
No great secrets wrt. why it was reasonably fast - it was a small bomber, with a bomb bay.

 

[Dimlee]

What about Fokker T.V.
But with improved aerodynamics (nose section especially), the crew reduced to 3 and with more powerful engines.
R-1830 at first and R-2800 later?
The bomb bay was spacy and probably could be enlarged if required.

 

[Dimlee]

To move away from the West, let's take a look at the East.
Yokosuka made the D4Y, a fast bomber on engine no better than DB 601A. Good for ~335 mp/h, with excellent range, although fragile due not having the self-sealing tanks in a heavily contested environment. With better engines, it did ~360 mph. Carrier- and dive-bomb capable, with Fowler flaps.
No great secrets wrt. why it was reasonably fast - it was a small bomber, with a bomb bay.

In service from mid-1942. Not too late?

 

[Dimlee]

Aero A.300.
"Almost" in service to the Munich.
Up to 1,000 kg internal. Needs better engines if developed further.

 

[tomo pauk]

In service from mid-1942. Not too late?

A tad too late, indeed.
What set it apart from other 1-engined bombers was it's trim size (= lowered the drag, thus had a better speed), not some kind of next-gen engine - that was 3-4 years late behind what Western aircraft were using.

 

[tomo pauk]

What about Fokker T.V.
But with improved aerodynamics (nose section especially), the crew reduced to 3 and with more powerful engines.
R-1830 at first and R-2800 later?
The bomb bay was spacy and probably could be enlarged if required.

Aero A.300.
"Almost" in service to the Munich.
Up to 1,000 kg internal. Needs better engines if developed further.

Aero A.300 - not faster than Blenheim? Will need Merlin or something like that.
T.V. - bigger than B-25, with half the engine power? R-2800 will be required, indeed.

 

[Dimlee]

Aero A.300 - not faster than Blenheim? Will need Merlin or something like that.

Aero A.300 with Bristol Mercury IX (according to that article):

• Cruising speed : 430 km / h at 5,960 m
• Top speed : 456 km / h at 5,960 m
• Climb rate : up to 4,000 m 7 min (9.5 m / s)
• up to 1000 kg of bombs in the bomb bay

Blenheim Mk.IV which entered service later with Mercury XV (Wiki again):

• Maximum speed: 266 mph (428 km/h, 231 kn) at 11,800 ft (3,600 m)
• Cruise speed: 198 mph (319 km/h, 172 kn)
• Time to altitude: 6,500 ft (2,000 m) in 4 minutes 10 seconds
• 1,200 lb (540 kg) total
  • 4 × 250 lb (110 kg) General Purpose bombs or
  • 2 × 500 lb (230 kg) GP bombs internally and 8 × 40 lb (18 kg) GP bombs externally

In those articles, Mercury IX is rated at 830 hp (2750 rpm, 4,400 m) and Mercury XV at 930 hp with no rpm/alt info.
The latter with 100 octane, probably? This site gives 995 hp to Mercury XV with 100 octane:
Bristol Engine Co: Mercury - Graces Guide
Could Aero A.300 reach 480-490 km/h with 995 hp, what do you think?

 

[tomo pauk]

In those articles, Mercury IX is rated at 830 hp (2750 rpm, 4,400 m) and Mercury XV at 930 hp with no rpm/alt info.
The latter with 100 octane, probably? This site gives 995 hp to Mercury XV with 100 octane:
Bristol Engine Co: Mercury - Graces Guide
Could Aero A.300 reach 480-490 km/h with 995 hp, what do you think?

I've posted the data tables for Blenheim marks at another thread here.
The Blenheim I was supposed to do 286 mp/h. Blenheim IV grew in weight by a good deal, an probably in drag. Mercury VII, VIII, IX and XV share the same power chart, the 100 oct fuel will indeed give more power under the rated height, for a bit better speed.
Drag is the killer for Blenheim, Beaufort, Fokker T.V, Hampden, He 111, Il-4, Wellington, Do-17, Battle, Avenger, Il-2, G4M, B-26 as it grew bigger and more cluttered...

 

[Dimlee]

Aero A.300 - not faster than Blenheim? Will need Merlin or something like that.
T.V. - bigger than B-25, with half the engine power? R-2800 will be required, indeed.

It is interesting to compare them.

T.V vs B-25H (sorry, just Wiki again):
Same length, almost the same wingspan, wing area 66.2 sqm vs 57.4 sqm.
Empty weight 4,650 kg vs 8,836 kg.
I'm a dummy in aerodynamics, but I note that both have the same airfoil in the root.
2x930 hp vs 2x1,700 hp.
Max speed: 417 km/h (alt unknown) vs 438 km/h (at 4,000 m)
Cruise speed: 335 km/h vs 370 km/h
Range: 1,550 km vs 2,170 km
Bombs: 1,200 kg vs 1,360 kg
I understand that the comparison is not totally fair, since B-25H's empty weight most probably includes 75mm cannon and 0.5" battery.
However, T.V does not look bad with the engines much weaker. I wonder what speed it could achieve with twice the engine power and other developments. Weight will grow up. The wing should be strengthened, most probably.

 

[tomo pauk]

The 1st B-25s were lighter and faster. The B-25J (a late model) data sheet by USN notes 255 kt, or 472 km/h. 1800 kg of bombs was the max for non-gunship versions. T.V. does not look bad, but it is probably a wrong choice for this thread.

 

[Shortround6]

I think we are falling into the famous wiki trap of listing the max everything of plane A (max range, max speed, max bombload) and not on plane B.
we also have the problem of the text not matching the specification list.

from Joe Baugher's web site for the B-25D but edited.
"Engines: Two Wright R-2600-13 Double Cyclone fourteen-cylinder air-cooled radials, each rated at 1700 hp each for takeoff, 1500 hp at 2400 rpm.
Performance: Maximum speed 284 mph (457kph) at 15,000 feet.
Cruising speed 233 mph (375kph) at 15,000 feet.
Range 1500 miles with 3000 pounds of bombs.
Weights: 20,300 pounds empty, 34,000 pounds maximum loaded.
Fuel: The fuel capacity consisted of four tanks in the inner wing panels, with a total capacity of 670 US gallons. In addition, a 515-gallon tank could be installed in the bomb bay for ferrying purposes, bringing total fuel capacity to 1255 US gallons. Later versions had additional auxiliary fuel tanks in the outer wing panels. Later versions could also have 125-gallon tanks fitted in side waist positions, a 215-gallon self-sealing fuel tank installed in the bomb bay, and provisions could be made for a droppable 335-gallon metal bomb-bay fuel tank.
Armament: Two 0.50-inch machine guns in dorsal turret. Two 0.50-inch machine guns in retractable ventral turret. One 0.30-inch machine gun in flexible mount in the nose. Starting with B-25D-5 the 0.30-inch nose gun was removed and replaced by a flexible 0.50-inch machine gun in the extreme nose and two fixed 0.50-inch machine mounted in the nose and firing through holes cut into the side of the Plexiglas glazing.
Normal bomb load was 3000 pounds but could be increased on the B-25D-1-NA with external underwing racks to a maximum of 5200 pounds."

Sometimes the bomber version B-25s were rated at 5200lbs with a pair of 1600lb AP bombs and torpedo, at totally useless combination that was never used in service.

If the above data is true then the B-25 could carry 3 times the bomb load of a Blenheim over the same range (I am not going to argue over 100 miles out of 1400-1500) and do it faster.

Chances of the Fokker T. V. even being close are about zero.
Nice cut away here.


but raises a bunch of questions, Co-pilot manned the dorsal gun? Radio man left his radios and was responsible for both side window guns and the ventral gun?
This thing did NOT have a small fuselage and the drag would be fairly high, you are going to need a LOT of power to get it to go very fast.

 

[Dimlee]

I think we are falling into the famous wiki trap of listing the max everything of plane A (max range, max speed, max bombload) and not on plane B.
we also have the problem of the text not matching the specification list.

from Joe Baugher's web site for the B-25D but edited.
"Engines: Two Wright R-2600-13 Double Cyclone fourteen-cylinder air-cooled radials, each rated at 1700 hp each for takeoff, 1500 hp at 2400 rpm.
Performance: Maximum speed 284 mph (457kph) at 15,000 feet.
Cruising speed 233 mph (375kph) at 15,000 feet.
Range 1500 miles with 3000 pounds of bombs.
Weights: 20,300 pounds empty, 34,000 pounds maximum loaded.
Fuel: The fuel capacity consisted of four tanks in the inner wing panels, with a total capacity of 670 US gallons. In addition, a 515-gallon tank could be installed in the bomb bay for ferrying purposes, bringing total fuel capacity to 1255 US gallons. Later versions had additional auxiliary fuel tanks in the outer wing panels. Later versions could also have 125-gallon tanks fitted in side waist positions, a 215-gallon self-sealing fuel tank installed in the bomb bay, and provisions could be made for a droppable 335-gallon metal bomb-bay fuel tank.
Armament: Two 0.50-inch machine guns in dorsal turret. Two 0.50-inch machine guns in retractable ventral turret. One 0.30-inch machine gun in flexible mount in the nose. Starting with B-25D-5 the 0.30-inch nose gun was removed and replaced by a flexible 0.50-inch machine gun in the extreme nose and two fixed 0.50-inch machine mounted in the nose and firing through holes cut into the side of the Plexiglas glazing.
Normal bomb load was 3000 pounds but could be increased on the B-25D-1-NA with external underwing racks to a maximum of 5200 pounds."

Sometimes the bomber version B-25s were rated at 5200lbs with a pair of 1600lb AP bombs and torpedo, at totally useless combination that was never used in service.

If the above data is true then the B-25 could carry 3 times the bomb load of a Blenheim over the same range (I am not going to argue over 100 miles out of 1400-1500) and do it faster.

Chances of the Fokker T. V. even being close are about zero.
Nice cut away here.


but raises a bunch of questions, Co-pilot manned the dorsal gun? Radio man left his radios and was responsible for both side window guns and the ventral gun?
This thing did NOT have a small fuselage and the drag would be fairly high, you are going to need a LOT of power to get it to go very fast.

You are right about "the trap", of course. That's why I said that my comparison was not completely fair. Thank you for adding more data (and thanks to Tomo).
Why I find T.V vs B-25 comparison interesting... T.V was introduced 3-4 years earlier and with worse aerodynamics and much weaker engines was not so much behind B-25 in speed and internal bomb load.
T.V fits one condition set in the start topic "Service use is at least by the time of Munich crisis..." So, I wonder, could it meet another condition of "their speed is at least 90% and preferably 95+ % of speed of the current fighters" in that early period if:
- Given more powerful engines available. R-2600 was produced since 1938, if I'm not mistaken.
- Fuselage streamlined. There were probably limitations due to mixed construction, but the nose section could be changed, at least? Something like DB-3 to Il-4 transformation but executed more effectively and without the empty weight gain.
- Other improvements?
And I assume that "speed of the current fighter" is not the speed of the fastest fighter in the service but some average value, around 500 km/h in early period.

 

[Shortround6]

Why I find T.V vs B-25 comparison interesting... T.V was introduced 3-4 years earlier and with worse aerodynamics and much weaker engines was not so much behind B-25 in speed and internal bomb load.

The first 24 B-25s were supposed to do 322mph, BUT they had no armor, no self sealing fuel tanks, a single .30 cal in the nose, a single .30 cal gun out the top, much like the Fokker (no turret) a single .30 cal that could be shifted side to side in windows in the fuselage and a single .50 cal in the tail operated by a man laying prone.
Stating with the 25th plane they got armor and self sealing tanks. Internal bomb load was 3,000lbs. speed dropped to 315mph. B-25A
On the 65th plane the top and bottom turrets show up, the tail gun disappears as does the waist gun. Speed drops to 300mph. B-25B

Try to bring the T.V up to the standards (armor and protected tanks) of late 1940 and see what happens to speed/range/bomb load.

 

[Dimlee]

The first 24 B-25s were supposed to do 322mph, BUT they had no armor, no self sealing fuel tanks, a single .30 cal in the nose, a single .30 cal gun out the top, much like the Fokker (no turret) a single .30 cal that could be shifted side to side in windows in the fuselage and a single .50 cal in the tail operated by a man laying prone.
Stating with the 25th plane they got armor and self sealing tanks. Internal bomb load was 3,000lbs. speed dropped to 315mph. B-25A
On the 65th plane the top and bottom turrets show up, the tail gun disappears as does the waist gun. Speed drops to 300mph. B-25B

Try to bring the T.V up to the standards (armor and protected tanks) of late 1940 and see what happens to speed/range/bomb load.

Should I equip my new T.V with 75 mm or 12 x 0.50"? Decisions, decisions...
I agree with everything you say. But I'm just trying to imagine what T.V could do if modernized as I mentioned above. Could it meet the criteria set in the Tomo's start topic. B-25 was just for a reference.

 

[Koopernic]

Compared to what? The Ju 88 had a maximum speed of over 290 mph, there weren't many other bombers capable of that speed in 1939/1940. 'Fast bomber' is a relative term and therefore in the time period Tomo stipulates, 250 to 280 mph is considered fast, especially when the fastest already in service in the mid-30s could just exceed 200 mph. Before the He 111, Do 17 and Ju 88, the Ju 86 couldn't even exceed 200 mph and the Ju 52 bomber transport, couldn't exceed 120 in level flight. Before the Whitley, Hampden and Wellington the RAF had the Overstrand, at a paltry 140+ mph maximum speed, still faster than the Ju 52/3m mind you.

The Bf 162 anyone? It was certainly fast, but could only carry 750 kg of bombs.

The aircraft's first flight was made by the prototype Ju 88 V1, which bore the civil registration D-AQEN, on 21 December 1936. When it first flew, it managed about 580 km/h (360 mph) and Hermann Göring, head of the Luftwaffe was ecstatic. It was an aircraft that could finally fulfil the promise of the Schnellbomber, a high-speed bomber. The streamlined fuselage was modelled after its contemporary, the Dornier Do 17, but with fewer defensive guns because the belief still held that it could outrun late 1930s-era fighters. The fifth prototype set a 1,000 km (620 mi) closed-circuit record in March 1939, carrying a 2,000 kg (4,400 lb) payload at a speed of 517 km/h (321 mph)

In October 1937 Generalluftzeugmeister Ernst Udet had ordered the development of the Ju 88 as a heavy dive bomber. This decision was influenced by the success of the Ju 87 Stuka in this role.

So this is another case where promising aircraft were compromised by the demands of dive bombing. This was with DB600 engines (likely 850 or 900hp) at the time.

Ideally the Ju 88 would have remained a fast bomber and received a mid wing layout and a bomb baby so it could carry bombs larger than 70kg. A Ju 88S1 could do 600kmh/372mph at 20,000ft and 610kmh/378mph at 26,000ft with GM-1 but had to carry its bombs externally. Probably would loose 13% speed so 325mph with bombs.

Had the Ju 88 remained as a fast bomber it would certainly have outrun the Hawker Hurricane.

 

[tomo pauk]

The aircraft's first flight was made by the prototype Ju 88 V1, which bore the civil registration D-AQEN, on 21 December 1936. When it first flew, it managed about 580 km/h (360 mph) and Hermann Göring, head of the Luftwaffe was ecstatic. It was an aircraft that could finally fulfil the promise of the Schnellbomber, a high-speed bomber.
...
The fifth prototype set a 1,000 km (620 mi) closed-circuit record in March 1939, carrying a 2,000 kg (4,400 lb) payload at a speed of 517 km/h (321 mph)

That is from English-language Wikipedia, per Winchester's book from 2004.
German-language Wikipedia gives 450 km/h for the Ju 88V1, and 465 km/h for the V2. Third prototype was powered by better engines than the V1, the 5ft had even better ones
Granted, going from a streamlined cockpit to a draggy one, while adding the bomb racks, guns, cammo paint, radio aerials, dive brakes etc. will put a dent on speed figures.

 

[Shortround6]

But I'm just trying to imagine what T.V could do if modernized as I mentioned above. Could it meet the criteria set in the Tomo's start topic. B-25 was just for a reference.

By the time you have a fuselage that will hold a crew of 5-6 you probably have too much weight and drag to hit the fast bomber speed numbers.

B-25s had engines that would give 1450hp at 12,000ft. in high gear.
The Martin B-26 could get into the 320s in early versions, small wing, few guns, under 500 gals of fuel and only 2000lb of bombs and they had engines that gave 1500hp at 14,000ft.

The T.V may have had an engine that gave 925-930hp at 10,000ft but only 835hp for take-off with 87 octane fuel?

 

[muskeg13]

Why wouldn't the early B-17s qualify as fast bombers? According to joebaugher.com, at 25,000 ft the Y1B-17A of 1938 had a max speed of 295 and cruise of 230. For the 1941 B-17E, the numbers are 318 max and cruise of 195-223, and the B-17F that began production in 1942 had a max of 299, war emergency speed of 325, but the cruise had dropped to 200.