Steamed_Banana
Staff Sergeant
- 1,144
- Sep 29, 2025
What effect if any did wind tunnel work with the engines have on the 12Y or 14N development?
Advanced French Fighters vs 1942/1943 contemporaries (6 Viewers)
Yes, that is exactly right.
Specifically regarding the 12Z 17, the power curves I provided in post #678 show that a manifold pressure of 140 to 143.5 *pièzes* - a rather peculiar unit of pressure that enjoyed a brief period of prominence in France during the 1940s, one being equivalent to 7.50 mm Hg - could be maintained up to an altitude of 5,850 to 5,900 meters.
I.e. a manifold pressure of 1075 mm Hg at an altitude where the local pressure is 359 mm Hg. The supercharger multiplication factor is therefore 1075/359 = 2.99—nearly 3.
Not too bad....
Shortround6
Lieutenant General
It is one thing to take planes out of crates and give them to units that have been flying the same planes for 2-4 months. They know what to look for and how the plane should handle. Giving them to experienced air and ground crews with experience on other types is going to need a learning curve. Giving them to new units with only a sprinkling of experienced pilots and mechanics is not going to go well.
That is very, very true. However, that is not what was believed by the bombing adherents of the 1920s and much of 1930s. It was believed in many air forces that aerial bombardment alone would force an enemy to surrender or face rioting in the streets or uprisings toppling the government. They also believed they only needed a few hundred bombers to do it and those bombers didn't need 2-4000kg payloads. It was supposed to be a "cheap" way of projecting power and waging war compared to tens or hundreds of thousands men on the ground. It took a few years for the militarily pointless to sink in, even for the British after suffering through blitz. Germans would not have the fortitude of the British civilians and just one (or two) more destroyed cities would tip the balance. (sarcasm)
The He 111 was not that bad a design. Clever design only buys so much and depending on clever design to offset 20% bigger airplane is asking for a lot.
He 111 and Ju 86 were started in 1934. He 111 started with 750hp unsupercharged BMW engines and was pretty much a failure, Switching to 950hp DB 600 engines (carburetors) and superchargers fixed most of the problems in 1936.
LeO 451 and Amoit 350 started in a 1934 program and in typical French fashion it took a while to produce results (too much dicking around with the specifications) and prototypes didn't fly until early 1937.
The LeO 451 and Amoit 350 weren't that much more advanced than the He 111, they were way ahead of the Ju-86 though.
Trying to do 1939-40-41 strategic bombing with roughly 1000kg payloads was not going to actually work despite what "theory" said.
And that cuts out the smaller plane/s leaving the LeO 451 and it has problems with bomb capacity vs fuel load although better engines could probably fix that.
French were working on 4 engine heavy bombers to replace the Farmans
but they were too late although the first allied bomber to bomb Berlin was a relative.
A single plane attacked Berlin on the night of June 7th and returned.
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Steamed_Banana
Staff Sergeant
- 1,144
- Sep 29, 2025
If you look at an LeO 451 and an He 111 in the same scale, the He 111 is much thicker / fatter. It was originally designed as a dual use bomber / airliner / transport. It's shaped like a carp or a fat cigar. And the dorsal and ventral gun positions stick out more. The wings are a good bit thicker too.
Wing span is roughly the same but wing area on the He 111 is 87 m2 (943 sq ft) vs 68 m2 (732 sq ft) on the LeO 451.
I don't know what the exact wing thickness is but you can see from the three view plans here it's much thicker on the He 111
By comparison, the LeO 451 fuselage is much thinner in profile, it's almost comparable to an A-20A or Boston III.
That extra thickness translates to drag, which is why top speed for the He 111 goes from 111E at 242 mph / 390 kph to 111H at 254-270 mph (400-435 kph) while the LeO 451 made 308 mph (500 kph)
Cruising speed was 186-230 mph for the He 111 (loaded / light) vs 224 - 260 mph / 360-420 kph for the LeO 451
He 111 could theoretically carry more bombs (2,000 kg vs 1,500 kg typically) but the vertical bomb bay cells limit bomb sizes.
LeO 451 also has better range of 2,300 km with a bomb load vs 1,200 km for the He 111.
That depends a lot on A) what you consider a strategic target B) how accurate your bombing is and C) the specific nature of the target (is it hardened etc.)
I don't think the LeO 451 actually has any problems with bomb load vs fuel load. And don't forget the Amoit 351.
Now the US types, Boston and Maryland, do have a relatively small bomb load, but both proved effective in the Western Desert in British hands against Tactical and Operational targets.
If you can cut rail lines and bridges leading to the factories that's almost as good as knocking out the factories themselves.
I really need to make a model of one of those hideous Farman. I don't think the French needed any four engine bombers TBH. Four engine aircraft were good for maritime patrol but probably not ideal for bombing.
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Shortround6
Lieutenant General
A lot depends on your engines. Four 920hp engines in a 40,000lb plane or two 1200hp engines in a 30,000lb plane or something else? you can save a lot of powerplant weight and structural weight if you have engines with better power weight ratios.
We have been over this before. The LeO 451 fuel capacity can vary from 3230 liters with 500kg of bombs to 1810 liters with 1400kg of bombs and down to 1000liters with 2000kg of bombs. He 111 could hold 3480 liters in the wing tanks. H-16 was good for 1200 miles not km with 2000kg of bombs. The Ps (DB engines) and H's could stick an 835 liter fuel tank in one half of the bomb bay. Max range for a P with the bomb bay tank was 2400km, Still with 1000kg of bombs.
yes long range missions with He 111s are not going to end well but the LeO 451 was not some sort of wonder plane that could carry large loads over long distances with a minimum of fuel.
A-20G with 2745 liters was good for 1690km at 264mph carrying 2000lb of bombs and that is at a higher take-off weight than the LeO 451. Could go further by slowing down.
BTW one source gives 227mph (365kph) as the economical crusiing speed for the LeO 451.
Douglas 7B was around 5000kg lighter and only held around 500kg of bombs and 1400 liters of fuel.
Not really. A single bomb hit on a rail line could usually be repaired in 24 hours. Bridges are another story. You need a lot of bomb hits on rail lines and rail lines are not easy to hit. A hit 20-30meters off does nothing to line itself and only needs a few men with shovels and brooms to clean things up. Most any place in Germany is going to have a steam crane and bucket available in an hour or two.
British and Americans went for rail yards with many parallel tracks and lots of switches that would maximize damage for the number of bombs dropped. Cutting a single line was often not worth the lost aircraft.
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Steamed_Banana
Staff Sergeant
- 1,144
- Sep 29, 2025
The LeO 451 made 1430 miles with 1400 kg of bombs. He 111 did potentially have a larger bomb load but due to it's vertical bomb racks, it could only carry relatively small bombs - the He 111 was designed to carry 32 x 50 kg bombs, later versions could carry eight 250 kg bombs (that is your 2,000 lb bomb load).
The Leo 451 could carry 2 x 500 kg bombs in the bomb bay or 7 x 200 kg bombs, plus a 200 kg bomb in each wing root bomb bay. For destroying relatively hard targets like factories, bigger bombs do help a lot.
I will grant you however that He 111s were modified to carry torpedoes externally which is a nice feature to have.
It was not a wonder plane nor did I ever claim it to be, it was a better bomber than an He 111, Do 15, or Do 17, and compared to the He 111 clearly had better streamlining and just a thinner profile (wing and fuselage) which ads up to better range for the same amount of fuel.
The Ju 88 makes a more competitive and interesting comparison though if we are comparing 1940 vintage aircraft I would still put my bet on the Leo 451.
The interesting thing is that the Germans never really came up with a fully new bomber design that was truly functional to replace these four. The Do 215 was marginal, the Do 217 was made in relatively small numbers as well (less than 2,000 built in 3 years) and though it looked good on paper, didn't perform so well in combat. The He 177 as we know was a great big disaster. The Arado 234 had great potential but didn't live up to it, and only 200 were built.
But there is no reason to assume that the French would necessarily sit on their heels. They were off to a better start than the Germans in 1940, and had plans to improve from there.
That is basically the number I quoted - 224 mph loaded, 260 mph 'light'.
Yeah, here's the thing though. The He 111H-16 that you mention here went into service in December 1942. The A-20G went into service in February 1943.
I think throughout this discussion we have been insisting on comparing French aircraft of 1940 with US, British, and German aircraft from much later in the war, with the assumption that the French planes could not or would not ever be upgraded. I don't think that's realistic.
yes obviously marshaling yards / rail yards and other concentrated rail facilities, as well as rail and motor vehicle bridges are the best targets. However even a rail line can be seriously damaged if it is cut repeatedly, which could also be done (and was done).
Other obvious targets include port facilities, warehouses, fuel, ammunition and supply depots, dams and so on.
By the way, strait line distance from eastern France to Ploiesti, Romania is 1,445 km or 898 miles. At maximum range with a relatively light bomb load that's well within reach for the LeO 451, the Martin 167, and maybe the Amiot 351 as well.
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Shortround6
Lieutenant General
Source please.
eight 250kg bombs = 2000kg I have made plenty of typos myself
Do 215 was a Do-17 with new engines. Faster yes but everything else was the same.
Do 217 had the new airframe. While much better it suffered from too much ambition and too little power, small wing did not help.
Wanting to carry ten 250kg bombs using similar engines to an A-20 on the wing the same size as an early B-26 while weighing around 10% more was not going to end well.
The weight doesn't matter so much as the speed. A-20G burns 110 gal/hr at 233mph. at 264mph it burns 140gph. at 314mph it burns 290 gph. All at max gross weight.
True and it had 1350hp engines. But the H-1 was in service in 1939 using 1010hp engines to start, switching to the 1100hp 211A-3 engines on the H-2s and then to the 1200hp 211D-1 engines on the H-3s which entered production in Nov 1939. These held the same amount of fuel and the same bomb loads. Late 1940 or early 1941 He 111H-4s, H-5s and (late 1941) H-6s got Jumo 211F-1 engines.
It is not realistic.
However, for the Germans the Ju-88 was not a 1940 design, it was a 1935/36 design, first flew in Dec 1936. It just took a while to get it into production and didn't get into service (in small numbers) until Sept 1939. As bomber it is rather overrated. It started out as a around a 22,000lb plane with a 565sq ft wing and at max load needed detachable rockets to have decent field length. The A-4s got a bit bigger wing, more powerful engines (in short supply leading to the A-5 version, big wing, old engines) and a gain of around 8000lb in max gross weight. The He 111s having to delay getting the new engines for a while.
Do-217 was the NEW bomber design of 1937 but it took until Aug 1938 to get the V1 into the air but with only 1075hp engines performance was less than sparkling, way less. Switching to Jumo engines did not improve things in 1939 and after trying a few other engines they settled on the BMW 801 radial in the 9th prototype. Low production was started in late 1940 with the E-0 and E-1 models and Photo recon missions started in early 1941 of Russian and in March of 1941 the Do-217 started anti shipping strikes in the west.
British were flying prototype Manchester's, Hallifaxes and Stirling's in 1939 and tooling up factories for them, it still took several more years to get into service in large numbers.
Americans were working on the B-24, B-25 and B-26 in 1939 although they didn't fly until 1940 (B-24 flew Dec 29th,1939 to fulfil contract), Yes they saw substantial modification/s
For the French we have to look at prototypes and/or projects to see potential 1942/43 bombers. Or try to figure out improvements to the 1939/40 aircraft and here is where things start getting difficult. The French have got two engines, the HS 12 series and GN 14N series. Both are hitting walls in development. If we assume that all is wonderful with the projected development with both engines, and we assume that French industry can provide enough engines (or they can buy substitutes from US or Britian) then we can look at 1400-1600hp engines and planes that will use them. If one or the other engines (or both) suffer delays then any improved bombers also take a major hit.
US engine development was nowhere near as smooth and stumble free as it may seem. Tens of Millions of dollars and tens of thousands of man hours were spent on engines that never powered a single plane in combat. Some never got an aircraft into the air for more than a few hours.
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