1936 to mid-42: fast 1-engined bombers instead of slow types?

tomo pauk said:

P-35 (no suffix) is also faster, by 20-25 mph.
The P-30 will also be faster, but at greater altitude, allowing a shallow dive to pick up speed.

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a lot depends on altitude. At 10,000ft the P-35 will be faster by about 40mph.
" Maximum speed of the P-35 at 10,000 feet was 282 mph."
The Battle was good for 240mph at 10,000ft.
Max speed for the Battle is usually give as 257mph at 15,000ft and one source 250mph at 20,000ft.
Max speed may have been around 17,000ft?
hitting max speed over 1000ft lower than the FTH of the engine seems a bit strange.

P-35 used a R-1830-9 which was good for 850hp at 8,000ft. It is slowing down the higher it goes over 10,000ft.
The P-35A of 1939-40 used a R-1830-45 of 1050hp at 7200ft.

Now the chances of hitting anything less than a town at 15,000 to 20,000ft with 4 bomb salvo is pretty small so best speed may have to be sacrificed for accuracy.

If you are 20mph faster you need 3 minutes to gain 1 mile Granted neither plane will be at full speed until the sighting/s are made.

Obviously the Battle is not a good choice for a high speed bomber, but in the mid 30s it wasn't that bad.
The Fairey P.4/34 was 26mph faster with the smaller wing, smaller fuselage and inward folding landing gear. Problem here is that the bombs (two 250lb) were carried outside so max speed maybe without bombs?

part of the Problem here is that a the simple nip and tuck (or not so simple) isn't going to do the trick when the British still want an under 60mph stalling speed (Wiki says 55mph-who knows) once you can use a higher stalling speed (smaller wing) you can do some more nip and tuck.

Maybe German fast single engine bomber can use the rockets the Ju-88s were using in 1940 to get off the runways?

For a P-40 take-off chart see http://zenoswarbirdvideos.com/Images/P-40/P-40TOCLC.pdf

Now a P-40D/E needed 1300ft take off at 8100lbs (clean) and 2200ft to hit the 50ft clearance line.
A P-40 (no letter) needed 721ft run at 6655lbs and 1201ft to hit the 50ft clearance line. ( I have no idea how they measured the 1 foot) and the P-40 had about 100hp less than the P-40D/E had.
The P-40 was using 15 degrees of flap.
Strap the belly tank or 500lb bomb under the P-40E and you need another 500 feet to clear the tree line.

One source says a Curtiss SB2C-2with a 1700hp engine needed 1135ft to take-off (no obstacle) with zero wind and 330 gallons of fuel and a 1000lb bomb. Add another 110ft for the 1600lb bomb.
The SB2C-2 is neither sleek or particularly fast.
But if you want to carry bombs fast and far (more than over the horizon) with a small wing you have some thinking to do.

Aichi B7A but land-based .

Shortround6 said:

part of the Problem here is that a the simple nip and tuck (or not so simple) isn't going to do the trick when the British still want an under 60mph stalling speed (Wiki says 55mph-who knows) once you can use a higher stalling speed (smaller wing) you can do some more nip and tuck.

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Just like the Luftwaffe penchant for dive bombing, some RAF penchants could've used some scrutiny

Shortround6 said:

But if you want to carry bombs fast and far (more than over the horizon) with a small wing you have some thinking to do.

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This is the task in, at least for Europeans, fighter-bombers are not the proper tool - range was okay for frontline job, but not for bombing something that was hundreds of miles away from their own air bases.

The math behind carrying bombs far and fast is easy: not just for the needs of this thread, the bomber need to be reasonably streamlined, with modern engine, and with enough fuel. We can take a look at 1-engined A/C with a lot of fuel, like the Fulmar (155 imp gals in the fuselage in the s-s tank, not a drop in the wing), early Mustang (220 US gals if the wing guns were omitted and aux fuel cells were installed instead), recon version of the F4F (the -7, with 555 gals of fuel in the 'wet wing', per AHT), P-39C etc. Granted, for European needs, going with 150 US gals / ~600 liters for the 1000+- HP engine - similar fuel tankage per engine as it was the case with Bf 110C - gives a lot of coverage vs. the neighboring state that we don't like.
Americans and Japanese will probably look at 170-180 gals if the engine is V-1710 or Kinsei?
Yes, the D4Y carried 275 US gals in it's unprotected wing tanks (+ 160 in drop tanks), not a good idea when going against the enemy that has you over-matched in all aspects. Granted, Asia and Pacific were and still are big place, so we can understand Japanese eagerness for very long range aircraft.

Shortround6 said:

Obviously the Battle is not a good choice for a high speed bomber, but in the mid 30s it wasn't that bad.
The Fairey P.4/34 was 26mph faster with the smaller wing, smaller fuselage and inward folding landing gear. Problem here is that the bombs (two 250lb) were carried outside so max speed maybe without bombs?

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Agreed that Battle was not a good choice for this. It's availablity for the mid-30s is iffy, the 1st squadron service was in mid-1937.
For the Fairey P.4/34 (and the Fulmar, as well as the other similar A/C), I'd suggest carryng bomb(s) just behind the radiators.

tomo pauk said:

Agreed that Battle was not a good choice for this. It's availablity for the mid-30s is iffy, the 1st squadron service was in mid-1937.
For the Fairey P.4/34 (and the Fulmar, as well as the other similar A/C), I'd suggest carryng bomb(s) just behind the radiators.

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I may have pushed it a bit.
Unfortunately the Battle was hindered by production problems. They had ordered the first 155 in Sept 1935 ensuring that 200 Merlins would be available before the Hurricane ans Spitfire got any for production.
But the Merlin was not quite ready. According to an old book things went like this.
A Merlin F engine was delivered in Nov 1935 for ground running and system function tests.
By March of 1936 a Merlin G (970hp) had been delivered and this is what they used for the flight tests at Martlesham Heath in July.
Hurricane production was delayed 6 months when they found that the rocker box design of the early Merlin's was unsuitable but RR was busy making the Merlin Is for the Battle and production of the Merlin II was delayed. By the end of 1937 they had 5 squadrons converted to Battles and by the 136th airframe they switched to the Merlin II engine because considerable trouble with the Merlin Is in service. Splitting Merlin II production between the Battle and Hurricane caused further delays in the Hurricane program but they got it sorted out the spring/summer of 1938 with Merlin production reaching over 100 a month in the summer.


It seems we are trying to design aircraft that will go fast and then trying to figure out what to do with them.
The Mission is following the airplane instead of the airplane suiting the mission requirements.

I am using the Battle as a example. In the middle 1930s the RAF thought that 250lbs were about all that was required for most work. A lot of design work went into holding the greatest amount of 250lb bombs. The P.4/34 had a single 250lb under each wing and the Henley did NOT carry a single 500lb bomb, it carried a pair of 250lbs in the bomb bay.
It may not have been a big deal to change either one. But was the British thinking of the time.

So we not only have to figure out the fast bomber, we have to figure out what to do with it.
The Battle was compromised by trying to be a strategic bomber. While it was supposed to dive (and did) it was actually level bomb from medium heights. It was too big and not quite maneuverable enough for low altitude tactical work or I should say not optimum.
The P.4/34 and Henley not only carried 1/2 the bomb load, they carried less fuel and less attention was paid to the level bombing role. if it was intended to do level bombing the rear seater may have done the bomb aiming?
For Germany your intention seems to be to replace the JU 87 with a faster dive bomber/close support aircraft and for the Germans that is going to mean a single large bomb or combination of one large and several small.
The US Army had no use for a high speed single engine bomber, US doctrine called for air cooled engines for protection against ground fire and went to twin engine aircraft for redundancy in any case. And the US army wanted a wheelbarrow load of small bombs since they wanted to attack troops in the field and not production centers or even choke points like bridges. Because of economics the Army only purchases 13 A-18s (ordered on July 23, 1936) and then waited several years before having the Attack bomber competition In Early 1939. When things went to pot the Army agreed to take Navy single engine attack planes as sort of "off the Shelf" planes rather than try to design any of their own, at least for the short term. Army may have meddled with the Curtiss A-25 (Helldiver) design a bit (?).
So far we have 3 different different missions requiring different ranges and different types/sizes of bombs.

Shortround6 said:

It seems we are trying to design aircraft that will go fast and then trying to figure out what to do with them.
The Mission is following the airplane instead of the airplane suiting the mission requirements.

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It is the bombers we're discussing, these are not exactly epitomes of pacifism
RAF will indeed want to bomb something beyond the Channel. Preferably something expensive, like a factory or similar asset. Luftwaffe will want to bomb French and Polish military assets - not just troops at the front line, but also stuff that goes towards the frontlines, like the truck convoys or rail traffic. Both the air forces will also probably try to attack enemy airfields.
French and Polish will try to do same to the Germans. Soviets and Japanese are wary of Western countries (for reasons invented or real), they will need aircraft to cover greater distances vs. what is expected from Ger/UK/Fr/Pol bombers.

Similar for the Americans. Eg. they can use the wing similar to that of Hurricane, with good thickness so the small bombs can be also carried in the wing. Not that far fetched, Americans tried that with XF4U-1 (but to bomb enemy aircraft). Wing still remains not too big, ~65% of what Battle had, or 20% smaller than what SBD had. If the radial is preferred (and it is likely it will be in the specified time frame), the bomb bay can be more voluminous without messing with streamlining so the wing bomb bays can be omitted; we might end up with something that looks like an F4F - not bad.
USAAC is not that demanding on the take-off distances

1936-to-mid-42-fast-1-engined-bombers
RAF will indeed want to bomb something beyond the Channel.

For the RAF from 1936 to May of 1940 the goal was beyond the Rhine .
forget Berlin
In May/June of 1940 an awful lot changed for RAF.

tomo pauk said:

Luftwaffe will want to bomb French and Polish military assets - not just troops at the front line, but also stuff that goes towards the frontlines, like the truck convoys or rail traffic. Both the air forces will also probably try to attack enemy airfields.
French and Polish will try to do same to the Germans

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It is around 320 miles from Berlin to Warsaw. It is around 50 miles from the center of Berlin to the German border. The Germans and the Poles can use shorter range aircraft than the British could regardless of the targets.
Same thing for the Germans vs the French. Munich was less than 200 miles from the French boarder. Stuttgart wasn't even 80 miles, Nuremberg under 170 miles.

Paris was about 200 miles from the closest point in Germany. Bourges was about 250 miles. And so on.

For the Soviets a short range bomber may work for them. Basically because they can bomb any of the eastern countries bordering them (forget trying to fly over Poland to bomb Germany in 1936-39) and the distances in Asia (trying to bomb anything Japanese) are beyond the technology of the time so tactical targets as the only things possible.

For the US, there wasn't a lot you were going to do a lot with.

even if you stuck a Twin Wasp in the nose. Especially once the customers decided they actually wanted to see out of the cockpits.

Actually for the US the power plants were a problem. Unless you can speed up Allison production (or use Wright R-2600s) you aren't going to make a "fast" bomber unless you are satisfied with scattering a few hundred pounds of small bombs on the 'target'.
Spec sheets for the F4F-3 (not actual test results, this is what they were guaranteeing the production planes would do or at least get within a few percent)
http://www.wwiiaircraftperformance.org/f4f/f4f-3-detail-specification.pdf

Please note that the "bomber" column is for a pair of external 100lb bombs, only 110 US gallons of fuel and with only a single .50 cal gun in each wing.
Speed at sea level was 278mph in the clean fighter version. Fuel was under the cockpit.

So take the F4F-3 take out the wing fold, yank the guns or fit a pair of .30 cal, move the fuel tanks out into the wings, put the bomb bay under the cockpit, add 2nd cockpit?
Get rid of the 2 stage supercharger (doesn't make any difference until you get closer to 20,000ft) ?

Now figure out how fast you want to "cruise" at and what kind of bomb load you can actually use.

Americans (and others, of course) can have two separate designs for the role - one entering production by 1936, another entering production in, say, 1940.
The SBN - the bomber whose prototype (SBA) - is depicted at the above picture, went as fast as the Battle despite the measly 750 HP radial. Yes, it carried less, 500 lbs.

tomo pauk said:

Americans (and others, of course) can have two separate designs for the role - one entering production by 1936, another entering production in, say, 1940.
The SBN - the bomber whose prototype (SBA) - is depicted at the above picture, went as fast as the Battle despite the measly 750 HP radial. Yes, it carried less, 500 lbs.

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The SBN is a bit of a puzzle. The HP figures are bit off, The production aircraft got a nice increase in power over the prototype and different accounts will list the take-off power OR
The normal (mac continuous) but often not both at the same time.
The prototype with low canopy had the 750-770hp for take-off and 675 hp normal R-1820-4 engine (?)
the production aircraft got R-1820-22 engines with 950hp for take-off and 850 normal in low gear (two speed supercharger)
They picked up a few more mph but then they picked up more drag too.

Taller canopy they could see out of and a taller vertical fin and rudder. Also please note no forward firing gun.
Figures in Wiki might need to be looked at Gross weight of 3,759 lb ???? might need an extra 3000lbs ???
Accounts can't even agree if it was a two man aircraft or a 3 man aircraft.
I am also having doubts about the range figures. It was US navy practice to trade bombload for fuel for the scout mission.

Could the SBN really fly 1000 miles with a 500lb load? An SBD carried 140 US gallons with a 500lb bomb with unprotected tanks, You could put a lot more fuel in the SBD if you went into overload and/or you took the bomb off.
Battle needed over 200 Imp gallons to carry 1000lbs 1000 miles.


Another thing that is interesting is the SBN used the same engine as the Buffalo fighter prototype and managed to be about 10mph faster. After a trip to Langley they got another 27mph out of it.


I would note that the Battle performance figures may have been obtained with a very Early Merlin and not with a Merlin II or III,

In case you have not seen this:

Thank you.

I don't see the good of the longer-range mission. Britain is going to bomb the Ruhr 1,000lbs at a time from presumably Lincolnshire? By day? Or by night? How is this going to advance the Allied cause? What the RAF needed, although it didn't know it, was a tactical bomber capable of supporting the army wherever it was engaged. In that war, the desert. Which you might achieve with a Defiant with no turret and maybe a handheld rear 303, although I'd make do with just the pilot and escorts rather than rear defence. Put the guns in the wings, of course. But really, was there a dedicated single-engined bomber other than for ground attack unless it was carrier-borne, where two engines were too much? Oh, did I forget Ki-32, Mary? That is an example of how useful and effective the concept is.

tomo pauk said:

Nothing was preventing people from making streamlined tactical and/or dive bombers.

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Well, you don't want a dive bomber that builds too much speed at a too fast pace if you want that the pilot is able to pull it out of the dive. So an unstreamlined plane with fixed uc makes some sense.

As said upthread, different countries, different needs.

The Battle must reach Germany from UK, so long range is needed.

Germany, SU, France need CAS aircraft to support the army, so range is less important.

A one fits all plane categorie won't be useful for many air Forces in preWW2.

The SBN-1 information kindly provided ThomasP shows how quickly things can go out of date and sometimes how difficult it may be to upgrade.

The figures for the SBN-1 were very good for 1937-38, however they didn't place the production contract until Sept 1938 and the Naval Aircraft Factory didn't deliver the first one until April of 1941. At which point the plane was certainly 2nd rate. However they were also trying to straighten out some handling issues.

The SBN-1 was powered an G series R-1820 and while it did have a two speed supercharger in did not have a reduction gear for the propeller. This did mean the engine only weighed just over 1100lbs and the 9 ft 1in prop (constant speed) would work in the power/speed range desired. An SBD-2 used a G100 engine and with reduction gear (certainly not the only change) the G100 engines were about 140-150lbs heavier ( a 1200hp G200 engine would be another 50lbs heavier) SBD used a 10 ft 10 in propeller.

Also look at the range figures. The SBN-1 can stretch it's 136 gallons pretty well, if it goes slow enough. a bit over 950 miles if flying at 149mph with bomb.
Flying at 223mph drops the range to 519miles. Flying at 248mph (max continuous ?) needs 90 gallons an hour.

9 cylinder radials are NOT the engine of choice for fast single engine bombers.

Shortround6 said:

Indeed the Battle would have been a speed demon in the Spanish Civil war. Or at least part of it.

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However, this relative performance was against biplane fighters, and was only achieved by leaving things like self sealing fuel tanks, armour and a realistic defensive armament out.
And this was the sacrifice all these 'fast' pre war light bomber designs suffered from, they were all terrible vulnerable against even fairly pedestrian fighters come 1939.

Shortround6 said:

9 cylinder radials are NOT the engine of choice for fast single engine bombers.

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By winter of 1938/39, that is certainly true. OTOH, Americans (as well as some other people) can use 14 cyl radials or V12 engines on a fast bomber by 1939. Already the 850-950 HP R-1830s are a step in the right direction, and so is the V-1710 and R-2600 from 1940 on.
Americans also can whip up a fast bomber with a turbo, their P-30 2-seater was flying with it in mid-1930s. British, French and Germans can try to 'militarize' the 2-stage engines from the same time and make bombers around these.
Preferably on a new design, not just slapped on some the legacy airframe.

Going back to one of my favorite airplanes to show the difference between radials and V-12s at this stage of development.




At 15,000ft the R-1830-17(single speed supercharger) wouldn't make any more power. The engine was not rated to use take-off power as military power.

Note that at 285mph the P-36A was using 30 more HP than the P-40 was using to go 310mph.
Note that at 285mph the P-36A was using 25% more power than the P-40 was.
Note that at 264mph the P-36A was using 25% more power than the P-40 was to go 258mph.

See the other thread about "what's in a name" to see the cowls and extension shafts that Curtiss, Sikorsky and Vultee were trying to use to reduce the drag of the R-1830, which was was smaller than the French, Italian and Soviet radials were to begin with.

Japanese didn't have much for options. Until they can build the DB 601 the Kawasaki (old BMW V-12) wasn't going to do the job. Radials or nothing.
Italians are in a similar place.
French need a new version of the H-S V-12.
For the French this was as good as it got.

Flown a few times (?) before it was hidden from the Germans. Reappeared after the war and worked on/flown but it was trying to compete with jets.

Shortround6 said:

For the French this was as good as it got.
View attachment 692121
Flown a few times (?) before it was hidden from the Germans. Reappeared after the war and worked on/flown but it was trying to compete with jets.

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What is that?

Loire-Nieuport LN.42.

A much improved LN. 401/411

Since they started building these with the small H-S X engine (670-700hp?) things did not go well.
The crews fought bravely but they didn't last long.
"One attack on 19 May resulted in the loss of 10 out of 20 dive bombers committed, while seven of the survivors were sufficiently damaged to be no longer airworthy."

Shortround6 said:

Loire-Nieuport LN.42.

A much improved LN. 401/411
View attachment 692128
Since they started building these with the small H-S X engine (670-700hp?) things did not go well.
The crews fought bravely but they didn't last long.
"One attack on 19 May resulted in the loss of 10 out of 20 dive bombers committed, while seven of the survivors were sufficiently damaged to be no longer airworthy."

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They should have tried to improve its looks while they were at it.