Twin/three engined bomber for 2nd half of 1941: how would you do it?

[tomo pauk]

Another single-country, simple design could've been non-turboed P-38, like one French ordered from Lockheed (later tested by RAF and discarded).
The most conservative max speed figure I've found was 357mph (clean, of course; C series of V-1710); the highest figure was 400mph (very doubtful). Very problematic catch for Zeroes Oscars, even with 360 mph. The space weight of turbo accessories can be used for extra fuel tanks, while cutting down the armament to 3 .50cals enables more pilot armor to be added.
With 1300 HP Allisons from early 1943 on, it takes Hayate to intercept it
In same time, 4 instead of 2 inner pylons, please.

 

[Shortround6]

Hand held .50s don't actually do much. They are rather hard to aim.
It is not so much the weight of the turrets/gun positions that affect performance but the drag. I posted a link to an article with performance charts for the Lincoln bomber. In the middle of it's weight range, 63,xxxlbs vs 69,xxxlbs a 10% difference cruise speeds and top speed varied by less than 10mph.

If you are designing a bomber from scratch, not using turrets or defensive guns can save quite a bit. For the same bomb load/speed/range combination you can build a smaller plane, smaller wing, smaller fuselage, smaller tail, lighter landing gear, etc. The fuselage can be smaller and more streamlined. A more gradual taper towards the tail vs a cut of cigar shape.
As an example the Avro Lancastrian had a top speed of 310mph at 12,000ft at 53,000lbs, Max weak mixture cruise was 285mph at 17,500ft. Now if we can find the figures for a Lancaster at near that weight we have a basis for comparison.

If you just yank turrsts/gun positions out of an existing airframe and plate them over you aren't going to get a big performance increase. Bombload/fuel load can go up without exceeding Gross weight but

 

[Shortround6]

Question is how many BMW 132 could BMW make per month?
And by 1941 how much factory space that had been making 132s was now making 801s?

It is no good just saying an engine was in mass production and so we can have as many as we want.

Wright had built over 8 000 Cyclone engines from the late 20s until 1938 and so it could be said it was in mass production.
Wright built about 1800 cyclones in 1938 and in 1942 built over 9,600 but that required the purchase of 3 new buildings, may more workers and tools AND major subcontracting.

 

[Shortround6]

Ah, Tomo, putting fuel tanks were the turbos went means that they are aft of the center of gravity. This leads to rather different handling as fuel is burned off. There is a reason that many WW II planes had a lot of unused volume. Pulling weight from one location in a plane doesn't mean you can put it somewhere else.
Spitfires, when they were changed from the fixed pitch wooden propeller to the three blade constant speed prop had to have a ballast weight fitted in the tail. 109s with wooden tails had extra armor fitted to the oil cooler as ballast to keep the CG in place.

 

[tomo pauk]

We delete turbo AND accesories, as I've stated
That includes leading edge intercooler (cancels out partly the lack of turbo, CoG wise). We've deleted one HMG and cannon, both were more distant to the CoG/MAC than turbo itself is

BTW, do you have any info about performances of Lightning I RAF tested?

(the picture is 'taller' than 600 px - I'll cut it if it makes problems)

 

[Shortround6]

We delete turbo AND accesories, as I've stated
That includes leading edge intercooler (cancels out partly the lack of turbo, CoG wise). We've deleted one HMG and cannon, both were more distant to the CoG/MAC than turbo itself is

Then just stick the fuel tanks in the leading edge of wing like the "J"s did and have done with it. Using "C" series engines you aren't going to get off the ground with much more fuel than that any way. The Early P-38s without self sealing tanks carried 400-410 gallons. The "J" with the leading edge tanks went back up to 410 from the 300 gallons of the E-H. "C" series engine was good for 1040hp for take off compared to the 1150hp "F" series engines used in the P-38 until the "F" model. The plane without turbos is going to have the same problem as the P-40, engine peaks at 13,200ft at 1090hp and gets weaker the higher it goes.

 

[rank amateur]

Another single-country, simple design could've been non-turboed P-38, like one French ordered from Lockheed (later tested by RAF and discarded).
The most conservative max speed figure I've found was 357mph (clean, of course; C series of V-1710); the highest figure was 400mph (very doubtful). Very problematic catch for Zeroes Oscars, even with 360 mph. The space weight of turbo accessories can be used for extra fuel tanks, while cutting down the armament to 3 .50cals enables more pilot armor to be added.
With 1300 HP Allisons from early 1943 on, it takes Hayate to intercept it
In same time, 4 instead of 2 inner pylons, please.

Hi Tomo, Do you mean a non turboed p38 used as high speed bomber. This thread is about bombers is it not?

 

[tomo pauk]

Then just stick the fuel tanks in the leading edge of wing like the "J"s did and have done with it. Using "C" series engines you aren't going to get off the ground with much more fuel than that any way. The Early P-38s without self sealing tanks carried 400-410 gallons. The "J" with the leading edge tanks went back up to 410 from the 300 gallons of the E-H. "C" series engine was good for 1040hp for take off compared to the 1150hp "F" series engines used in the P-38 until the "F" model.

I'm fine with just the LE tanks

The plane without turbos is going to have the same problem as the P-40, engine peaks at 13,200ft at 1090hp and gets weaker the higher it goes.

That kind of engine performance is decent for a bomber/ground attack plane; we can use those extra 2 x 100 HP already in 1942 then.

 

[tomo pauk]

Hi Tomo, Do you mean a non turboed p38 used as high speed bomber. This thread is about bombers is it not?

Correct on both accounts

 

[Shortround6]

That kind of power is crap for bomber/ground attack plane in 1941 let alone 1942, especially one with a 327 sq ft wing. A-20s were rolling of the lines in the fall of 1940 with 1600hp engines and the ability to carry 2400lbs of bombs 525 miles. 10 months before the second British 322 flys. The B-25B model is coming of the line in Aug of 1941, range 2000 miles with 3000lbs of bombs. P-38s with under wing racks didn't become common until the "F" model with 1325hp engines.
What does it bring to the table that a pair of P-40C's don't?
To get a plane off the ground with a big load you need either a big engine or a big wing or both. A P-38 with a pair of "C" series Allisons doesn't have either.

 

[davebender]

This aircraft gets my vote for a U.S. light bomber. It was faster then many fighter aircraft. In the Pacific it could probably operate without escort as it can easily out run the IJA Ki-27. Put 100 A20 skip bombers on Luzon with competent leadership and they might derail the December 1941 Japanese invasion by sinking the troop transports.

 

[tomo pauk]

That kind of power is crap for bomber/ground attack plane in 1941 let alone 1942, especially one with a 327 sq ft wing. A-20s were rolling of the lines in the fall of 1940 with 1600hp engines and the ability to carry 2400lbs of bombs 525 miles. 10 months before the second British 322 flys. The B-25B model is coming of the line in Aug of 1941, range 2000 miles with 3000lbs of bombs. P-38s with under wing racks didn't become common until the "F" model with 1325hp engines.
What does it bring to the table that a pair of P-40C's don't?
To get a plane off the ground with a big load you need either a big engine or a big wing or both. A P-38 with a pair of "C" series Allisons doesn't have either.

P47D: 2000 HP, 300 sq ft wing, empty weight 12000* lbs, T/O weight 14500 lbs, max T/O weight 17500 lbs.
Lightning I: 2100 HP, 327 sq ft wing, empty weight 10000 lbs, gross weight 14500. We can add some 200 lbs for additional fuel tanks, perhaps another 300 lbs if we want them to be self sealing. Lets add another 500 lbs of armor. Makes 11000 lbs empty.
Both planes carried about the same 'quantity' of fuel internally ( + 20-30% of fuel for 'my' version of P-38 ).
In my eyes better than P-47D (in bomber role), 3 years earlier.

Addition of pylons is not something to quarrel about if we want LightniBomber.

Compared with 2 x P-40C - uses 2 times less pilots for same amount of bombs delivered **
Compared with proper US bombers, the advantages would be less cost, crew needed, plus greater speed vs. B-26. A tougher to catch for Axis fighters?
Since we compare it to US bombers, we can compare it with nations that would've likely received it: UK/Commonwelth SU. So we find Blenheims, Beuforts, Beaufighters, SB-2s, very small number of Pe-2. Also Hurricanes in bomber role, Il-2 (single seaters). Only Beaufighter Pe-2 stand out here, so there is a role for the P-38 as a bomber.


*added: another number I've found states it was 10K lbs empty
**added: the bomb load for the P-40C was 500 lbs - or that was the number I've been able to found. How about 2000 lbs for this kind of Lightning - so 1 Lightning carries 2 times as much as 2 x P-40Cs.

 

[Glider]

What would be interesting would be the impact on performance of all this additional weight let alone the drag from the bombs and presumably drop tanks. Speed would presumably be well down and range. Any advantage over the light bombers significantly reduced.

The A 20 would be a class act for this period and another often overlooked aircraft would be the Baltimore.

 

[Shortround6]

P47D: 2000 HP, 300 sq ft wing, empty weight 12000* lbs, T/O weight 14500 lbs, max T/O weight 17500 lbs.
Lightning I: 2100 HP, 327 sq ft wing, empty weight 10000 lbs, gross weight 14500. We can add some 200 lbs for additional fuel tanks, perhaps another 300 lbs if we want them to be self sealing. Lets add another 500 lbs of armor. Makes 11000 lbs empty.
Both planes carried about the same 'quantity' of fuel internally ( + 20-30% of fuel for 'my' version of P-38 ).
In my eyes better than P-47D (in bomber role), 3 years earlier.

The depend on source and what is meant by "empty". America's Hundred Thousand gives the empty weight of a YP-38 as 11,196lbs and a P-38J as 12,780lbs. These weights do not include the gun installation, armor, trapped fluids and some other details. Of interest to you is that while on the YP-38 the turbos are added in to the engine accessories weight they are listed separately for the "J", 613lbs. The "J" used a slightly different turbo charger than the early planes. also of interest is the fuel system weights, 121.4lbs for the YP-38 and 505.8lbs for the "J" with the leading edge tanks. Just under 11,000lbs? Moving on to the "basic weight" (empty weight plus trapped fluids, guns, gun sights, armor, oxygen,etc) we have for the "J" (YP-38 weights not given) 80lbs trapped fluids, 303lbs oxygen equipment (not needed in your "bomber"?) 245lbs of armor and BP glass and few other bits and pieces, including 56lbs for drop tank provisions. Getting to the guns we can leave out the 20mm and cut the weight of the four .50s from 425lbs to 318lbs? SO our basic weight is now up to about 11,600-11,700lbs. moving on to our "useful load" we have 200lbs of pilot, a minimum of 128lbs of oil, How much ammo? 400rpg for three guns is 373lbs. 410 gals of gas is 2460lbs. we are up to 14,750lbs easy and we haven't hung a bomb on the plane.
By the way, there is a manual for the Lighting I in the manuals section of this site. Tare weight (British empty) is 11,445lbs. with an all up weight of 14,445-14,573lbs depending on guns and ammo. Those weights are for 300rpg of .50 cal ammo.

I am not sure you really want to use the P-47 as an example of a bomber. The early versions at 15,000lbs needed 3500ft to clear a 50 ft obstacle on take-off at zero degrees C with a 10% increase in distance for every 10 degrees C above zero on a hard runway. 15,000lbs is about right for the 305gal internal fuel, a 75 gallon drop tank and two 500 bombs. Blenheim was practically a STOL plane in comparison. Take-off run (not to 50 ft) of 888ft, temp not given. 1600-1700hp but a 469 sq ft wing. An A-20B at 22,000lbs needs 2300ft to clear 50ft at 0 degrees C and at sea level.
To have a useful bomber/ground attack plane in the early part of the war, you need a plane that can survive to make it to the target and back. The Blenheim has problems here. But you also have to be able to take off from existing airfields or slightly modified ones and have the range to carry the bombs to the target. Failure at either one of those means no mission at all regardless of the survivability of the plane.

Addition of pylons is not something to quarrel about if we want LightniBomber.

It is not but it might mean something if the older, lower powered planes didn't carry underwing loads for a reason.

Compared with 2 x P-40C - uses 2 times less pilots for same amount of bombs delivered **
Compared with proper US bombers, the advantages would be less cost, crew needed, plus greater speed vs. B-26. A tougher to catch for Axis fighters?
Since we compare it to US bombers, we can compare it with nations that would've likely received it: UK/Commonwelth SU. So we find Blenheims, Beuforts, Beaufighters, SB-2s, very small number of Pe-2. Also Hurricanes in bomber role, Il-2 (single seaters). Only Beaufighter Pe-2 stand out here, so there is a role for the P-38 as a bomber.

Against the P-40s, your version of the P-38 may carry more bombs (or maybe not) but you are bringing one fewer .50cal guns and eight fewer .30 cal guns for ground strafing. You have 205 gallons of fuel per engine vs the P-40s 135-162 gal?, advantage Tomo P-38. take offs may be close depending on P-38 load.

Against the US bombers you have speed but payload and range are rather lacking. The B-25A could carry 3000lbs 1000miles at a 265mph cruise speed later versions were slower. Maxim bomb load was 5200lbs but the combination of weapons to reach that total was rather stupid. How much cheaper is the P-38 bomber if it either can't reach the target or needs two planes to carry the same bomb load as a single B-26? As for the other planes, same arguments. Payload vs range and field performance.

Take off performance for a P-38D/E was 1680 ft to 50 ft at 15,000lbs, 2250ft to 50 ft at 17,000lbs and 2920ft to 50ft at 19,000lbs. The plane with the "C" series engines will have about 10% less power and again add 10% to the distances for every 10 degrees C above 0. Distances are for hard surface runways. soft surface can add 100ft at 15,000lbs and 300ft at 19,000lbs.

 

[davebender]

Bomber aircraft have a gyro stabilized bomb sight and dedicated bombardier for a reason. Could a P-38 or P-47 fighter aircraft bomb as accurately as an A20 light bomber? Personally I have my doubts. The size of the bomb load means nothing if it cannot hit the target.

 

[tomo pauk]

The depend on source and what is meant by "empty". America's Hundred Thousand gives the empty weight of a YP-38 as 11,196lbs and a P-38J as 12,780lbs.

I've received the Holy Book today

These weights do not include the gun installation, armor, trapped fluids and some other details. Of interest to you is that while on the YP-38 the turbos are added in to the engine accessories weight they are listed separately for the "J", 613lbs. The "J" used a slightly different turbo charger than the early planes. also of interest is the fuel system weights, 121.4lbs for the YP-38 and 505.8lbs for the "J" with the leading edge tanks. Just under 11,000lbs? Moving on to the "basic weight" (empty weight plus trapped fluids, guns, gun sights, armor, oxygen,etc) we have for the "J" (YP-38 weights not given) 80lbs trapped fluids, 303lbs oxygen equipment (not needed in your "bomber"?) 245lbs of armor and BP glass and few other bits and pieces, including 56lbs for drop tank provisions. Getting to the guns we can leave out the 20mm and cut the weight of the four .50s from 425lbs to 318lbs? SO our basic weight is now up to about 11,600-11,700lbs. moving on to our "useful load" we have 200lbs of pilot, a minimum of 128lbs of oil, How much ammo? 400rpg for three guns is 373lbs. 410 gals of gas is 2460lbs. we are up to 14,750lbs easy and we haven't hung a bomb on the plane.
By the way, there is a manual for the Lighting I in the manuals section of this site. Tare weight (British empty) is 11,445lbs. with an all up weight of 14,445-14,573lbs depending on guns and ammo. Those weights are for 300rpg of .50 cal ammo.

I can agree with numbers you've presented.
If we continue with 14500 lbs as normal TO, then mount wing shackles and 2 x 1000 lbs bombs, it's 17K lbs now - within what P-47 was capable with 10% less wing area and 5% less power.

I am not sure you really want to use the P-47 as an example of a bomber. The early versions at 15,000lbs needed 3500ft to clear a 50 ft obstacle on take-off at zero degrees C with a 10% increase in distance for every 10 degrees C above zero on a hard runway. 15,000lbs is about right for the 305gal internal fuel, a 75 gallon drop tank and two 500 bombs. Blenheim was practically a STOL plane in comparison. Take-off run (not to 50 ft) of 888ft, temp not given. 1600-1700hp but a 469 sq ft wing. An A-20B at 22,000lbs needs 2300ft to clear 50ft at 0 degrees C and at sea level.

To have a useful bomber/ground attack plane in the early part of the war, you need a plane that can survive to make it to the target and back. The Blenheim has problems here. But you also have to be able to take off from existing airfields or slightly modified ones and have the range to carry the bombs to the target. Failure at either one of those means no mission at all regardless of the survivability of the plane.

It is not but it might mean something if the older, lower powered planes didn't carry underwing loads for a reason.

Using a converted fighter to carry heavy bombs is not ideal, I agree. Blenheim was able to carry just above half of those 2000 lbs, though.

Against the P-40s, your version of the P-38 may carry more bombs (or maybe not) but you are bringing one fewer .50cal guns and eight fewer .30 cal guns for ground strafing. You have 205 gallons of fuel per engine vs the P-40s 135-162 gal?, advantage Tomo P-38. take offs may be close depending on P-38 load.

Against the US bombers you have speed but payload and range are rather lacking. The B-25A could carry 3000lbs 1000miles at a 265mph cruise speed later versions were slower. Maxim bomb load was 5200lbs but the combination of weapons to reach that total was rather stupid. How much cheaper is the P-38 bomber if it either can't reach the target or needs two planes to carry the same bomb load as a single B-26? As for the other planes, same arguments. Payload vs range and field performance.

Again, I don't think that P-38 bomber was to be ideal, nor that it would've been better than any plane designed as bomber from day one. What ever advantage 'proper' bomber has vs. P-38 in bomber role applies equaly in P-38'b' vs. adapted SE/TE fighter in bombing role. And those fighters were used in almost all air forces, despite that.

Take off performance for a P-38D/E was 1680 ft to 50 ft at 15,000lbs, 2250ft to 50 ft at 17,000lbs and 2920ft to 50ft at 19,000lbs. The plane with the "C" series engines will have about 10% less power and again add 10% to the distances for every 10 degrees C above 0. Distances are for hard surface runways. soft surface can add 100ft at 15,000lbs and 300ft at 19,000lbs

.

I'm glad to see the 2250 ft @ 17000 lbs - comparable with A-20B figures and much better that P-47 at only 15000 lbs. Even if we stretch those 2250ft for another 20% (because we use 1050 HP V-1710s), we're still better then P-47. And we have twice the bomb load than Jug Or we go for same bomb load (2 x 500 lbs) and achieve 2000 ft to clear 50ft obstacle - under 60% of what P-47 needed.
P-47 has advantage of 5 more HMGs - that's quite a lot. We'll wait another two years for that, though.

 

[tomo pauk]

What would be interesting would be the impact on performance of all this additional weight let alone the drag from the bombs and presumably drop tanks. Speed would presumably be well down and range. Any advantage over the light bombers significantly reduced.

Indeed, those things hamper the performance.
We can try out a comparison with Ju-88 - a fast bomber that carried bombs externally more times than not. I someone has speed figures about the Junkers, please enlighten us about how much Junkers lost speed with bombs under wings.

The A 20 would be a class act for this period and another often overlooked aircraft would be the Baltimore.

Both were cool aircraft. A-20 especially.

 

[tomo pauk]

Bomber aircraft have a gyro stabilized bomb sight and dedicated bombardier for a reason. Could a P-38 or P-47 fighter aircraft bomb as accurately as an A20 light bomber? Personally I have my doubts. The size of the bomb load means nothing if it cannot hit the target.

Think you've said in this thread that level bombers (= bombers employing bombardiers and giro sights) were utterly inacurate. I agree.

A-20 was bombing precisely if flying 50 ft over surface - within scope of what most of ww2 planes were capable to do.

 

[davebender]

Think you've said in this thread that level bombers (= bombers employing bombardiers and giro sights) were utterly inacurate.

Not exactly what I intended.

Bombing accuracy of B-17 and B-24 groups in WW2
An average B17 group could place 32.4% of its bombs within 1,000 feet of a factory building. B24 groups averaged 30.4%. But these level bombers were flying at 25 to 30,000 feet.

Accuracy is far better at low altitude. An A20 light bomber should be level bombing at about 3,000 feet. Just above the height of small arms fire. In the anti-shipping role it would be skip bombing or torpedo bombing from an altitude of maybe 150 feet.

 

[tomo pauk]

Subject of the thread is medium/twin engined bomber - the type flying against factories, but also against far smaller targets, like trucks, bridges, cannons, tanks etc. Bomb landed at 500, 300, even 100 ft near the target just won't cut it.
A-20 (or whatever) flying at 3000 ft just cries for 20mm to be trained against it, plus the plane is much more likely to be spotted than one flying at 150-200 ft (50 ft from post above is to be read as 50m - sorry). Trust the trained AA crew member (loader at 1st, shortly an aimer, than a commander)
In skip-bombing role bomb aimer is redundant too - pilot can just press the button to release the bombs.