The French Air Stricking Force: And the winner was... the LéO 451 (revised 06 / 10 / 2013)

The program : a bomber which could be as nimble as a fighter

The French program of November 1934 - designated as B4 for bombing, 4 crews - exacted as fast as possible aircrafts (one wanted initially 400 kph, after what a speed of 470 kph was exacted, 20 kph more than the fighter program published only 4 monthes earlier...).

Another constraint was the use of an engine chosen by some state deciders in place of self chosen engine. Why?

Because all the French aircraft companies were never sufficiently rich for investing enough money in all of the needed equipments, especially regarding the engines. 

The French Republic was always delaying what it was buying. Worst, by the bias of systematic devaluations, the price was automatically lowered... 

In that time, the costliest part of a bomber was the engine, so the French state became the buyer of the engines, implying, obviously, the choice of the engines was in the state bureaucracy instead of  the aircraft designers. Obviouly, also, the state commission of deciders was under strong pressures of various lobbies.

Yes, I did not like the US various lobbies, but, at least, they are well identifyed and they can be defeated by other ones, or combinations of other ones. It was never the case in the France third République where all informations disapeared under the fog of utmost secrecy.

Were the members of these commissions very proficient? Obviously, all of them claimed they were. However, the only perfect validation is, allways, given a posteriori by the History itself. In the actual case, the defeat of June 1940 demonstrated how there claims were illegitime.

A good scholar cursus define only, to any human person, a good level of acquisition of knowledge. That has nothing to do with a proficiency, which is the demonstrated capability to go out the beaten tracks.

A very innovative prototype: A good case to use untested engines for trial flights?

En 1935, attracted by some advertisements, the commission members had chosen to order an radial air cooled engine (HS 14 Aa) developped - but still untested in flight - by Hispano-Suiza and promising to deliver 1300 Cv. This engine was to be fit on all the brand new prototypes of the bombers developped by the various compagnies.

That decision was the worst possible one. Ok, Gnome et Rhône experienced some problems with its own aircooled radial engines 14 Kirs / Kjrs and ordering engines to Hispano-Suiza was a method of pressure on the French specialist of air cooled radial engines. But this order was very shortsighted.

At the origin, the Hispano-Suiza company had bought some licences for Wright radial engines. 

Contrary to my ancient readings, one of my readers (Thank you Alain) wrote me that it was a true  Hispano-Suiza engine, and not a licence version of the Wright 2600. It was less powerfull but 5 cm narrower in diameter, lighter, and its rotation speed was less important. 

It used, as the US powerfull engines, the 100° octane fuel, implying frequent overheating  when using the standard 85° octane fuel of the French Armies during the developpment of this engine as, also, of the prototypes on whitch it was fitted.

Obviously, it seems that an easy solution could had to prepare 2 sets of engine supports and cowlings, allowing a quiet aerodynamic finishing of the aircrafts. 

The  STAé (service technique de l'Aéronautique) commissions was lacking completely of any adaptation capability to the real situations.

Nevertheless, after a lot of work, the very good engineers of Hispano-Suiza achieved to finish fairly the 14 Aa engine, which obtained good results on two prototypes: The excellent Latécoère 570 and the Koolhoven FK 58. It was too late.
This history had an adverse consequence on the developpment of the Hispano-Suiza liquid cooled 12 cylinder in Vee, because the very experimented engineers needed to that work have been send to reinforce the team working on the 14 Aa. That explained how long was the time to finish the 12Y51 needed for the Dewoitine 520.

A tactically erroneous conception

The major idea of this bomber program was the new bombers being faster than the projected French fighters, they were absolutely able to outrun all fighters in the world. Amazing !

Even if I acknowledge that some French fighters - as the Nieuport 161, for example - were very well designed, that did not garantees that the ennemy fighters cannot be faster. 

Using the data of some Caudron racers flying at 500kph at sea level with only 300 hp, it was easy to project a 860 hp fighter able to fly at 550 kph at 5000m.

A bomber flying at 550 kph could have been a real solution! A very clean and exceptionnally powerful bomber was the good answer as was the US Boeing B29 (580 km/h), fitted with four 2200 hp engines in 1944. But, in 1936, everywere in the World, it was not a real possibility.  

In 1944, even the B29 might be downed by a fighter diving from above as it hapened some few times over Japan. 

No, a true bomber, once in the air, cannot be sure to go back home: She is the natural prey of the ennemy fighters. General Giulio Douhet was only reasonning as if the bombers were battleships. But they are not...

A fast good bomber may kill the naughty fighter by shooting strait between the twin rudders...

Another exacting was the twin fins-and-rudders of the B4 bombers to allow the rear shooting of a 20mm cannon.

The only one French aircarft designer who found a true good twin fins-and-rudders solution was engineer Moine for the Latécoère 570, exceptionnally easy to fly, very well adapted to the futur strugles but never ordered. 

If you observe the bombers of the WWII, you can see that the most famous were not fitted with the twin fins-and-rudders, for some reasons :

• At low speed, with important angles on wind stream, the fins-and-rudders were masked by the engine cowlings, or the landing gear box, that giving a very difficult aerodynamic stiring control.
• The twin fins-and-rudder  was mechanically a complicated structure, because they are situated downstream the engines cowling. At high speed, the vortices induced by the engines produce vibrations which are dangerous from a structural point of view. To overcome these vibrations, on must strengthen the assembly of the tail, then one increases substancially the mass of the bomber.

All the US bombers bought by the French government in 1938 (Douglas DB 7 Boston and Martin 167 Maryland), used a classical tail and they had good flying characteristics. The French deciders were happy with them. 

So, the twin fins and rudders was not so crucial for them. But they accepted to buy these US bombers without self-protected fuel tanks the French-build bombers had.

At last, I need a cannon!

The French bureaucracy had decided another juicy nugget: The rear defense used a cannon! 
The chosen weapon, the Hispano-Suiza HS 404 was indoubtedly a very good one, with a impressive destructive power and very good ballistic properties. 

Ok, but the actual reasonning was biased as if the deciders were allways stuck in a two-dimmensionnal universe. In an air combat, the decision depends, in most of the cases, by the intantaneous speed difference in all of the three dimensions. So, any fighter, even the poor Morane 406, was able to manoeuvre quickly in an unexpected direction. The 5 times heavier bomber was never able to escape such a manoeuvre, owing to her own inertia.

If that weapon had a muzzle velocity twice as great as the one of a machine-gun, a gunsight allowing a very great precision, the bet may have been a winner one. It was not the case.
Worst, the number of shells was to small. Initially, the cannon had 60 shells (6 seconds!) in the drum, after, it had only 30 shells drums (14 kg). In a bomber, which is manoeuvring to escape ennemy firing, the number of g might increase from 1 to 3, even 4, increasing the drum weight up to 60 kg. The French gunners were not Hulk!

One or two belt-fed riffle machine-guns were a very better solution.

The perfect bomber?...!

That bomber was the Lioré-Olivier 451 or LéO 451. 

An aircraft I saw personnaly in a hangar of an airfield (Boufarik, in Algeria) when I was 6 or 7 (1952). 

Around me, the peoples were chating together, mezzo vocce, and said "it is a warplane". 

Obviously, I did not understand anything, but she appeared me as malicious.

The aerodynamics study of the LéO 451 was up to date, with very thin wings (15 to 11% relative thickness), the engine cowlings designed by engineer PE Mercier were very optimized for the highest possible speed (allowing 40 kph more than the previous ones). 

The fuselage was elegant allowing a good visibility to the pilot, the bomber and the gunner.

 LéO 451 in flight on this site wwiivehicles

The performances were outstanding for its time, achieving, with a bomb load of 1350 kg and all fuel, 502 kph at 5100 m and 640 kph IAS in very shallow dive (the finish of the tested bomber was particularly good, the others flying at 495 kph). 

That was 25 kph faster than a Ju 88, 55 kph faster than a He 111, etc.

The climb  to 5000 m in 14 minutes displayed that this bomber was a bit too heavy. 

The reason for that was the suggestion made by Jacques Lecarme, a skilled engineer and test pilot who thought that a bomber could be used as a fighter (!).

The flying qualities were very good in flight, with an outstanding manoeuvrability. 

A big take off concern!

Nevertheless, some problems occurred when taking off. 

The origins of these problems were in the weight excess, in the too small fins-and-rudders and in the landing gear box.

A little power assymetry between the two engines when taking off induced a crash, deadly when the aircraft was full loaded. 

From the September 3, 1939 to the Mai 10, 1940 (included), 20 crashes destroyed at least one bomber. 

So, the losses, without any ennemy action, accounted ~20%. 

The test pilots - too skilled to be representative of common operationnal ones (?!) - never anticipated such a behaviour. 

Lately, since the March 18, 1940, Mr Jacques Lecarme went in the bomber squadrons to explain the pilots his own take off method. 

Nevertheless, there was still some crashes, but post-take off and probably due to air screw problems or excess of weight.

Another problem was the huge manufacturing time of this bomber (60,000 hours!). 

The first 5 LéO 451 were built in 4 months. 

And none were ready to fight. From September 1, 1939 and May 10, 1940, about LéO 451 were taken into account by the French Air Force, an average of 12 bombers a month.

It's impossible to see that as a sucessful result of our nationalization. 

Even if Jacques Lecarme answered to an article published during the 60's in Aviation Magazine, that the SNCASE company had delivered 450 bombers at the June 24, 1940, only the half part of these aircrafts were taken into account by their operational aircrews.

So, the other ones were not usable in combat.

The efficiency?... only average

Among the 247 LéO delivered for Mars 1st, 1940, only 108 were accepted! So, the May 10, 1940, few pilots and crews were able to use this bomber with the maximum skill. 

Ok, this aircraft allowed loops and roll, but that was quite useless.

Some extraordinary pilots, in team with excellent gunners, were able to survive very difficult situations, even downing about 12 German fighters. But it was not the job of this aircraft!

One know that, for the 10 days between the May 10 and the May 20, among 128 take off, only 95 sorties go to the objective. This is the proof the LéO 451 was not perfected enough.

The losses rate was 31 bombers among the 63 bombers available (49%). 

That was the same rate as the one for the Bréguet 693 and similar to the one of the RAF Fairey Battle. 

It was the direct translation that nobody, among the Allieds, was knowing how to strike the Wehrmacht.

For all the Battle of France, 80 Léo 451 were lost (for any reason) among the 180 used in operational units. 

The rate of losses was progressively lower.

Most of the times, the Léo bombers were sent to attack by small groups (3 to 4 !) at low level, favouring the Flak.

Facing the Wehrmacht, the results of such bombing were likely a bit disapointing
.

That was the hard lesson of the hasty order of an unperfected bomber.

Just after the French defeat, the fins and rudders of all LéO 451 bombers were enlarged with the amazingly very fast agreement of the German commission.



After the invasion of the Vichy France, the Germans captured hundreds of these bombers they transformed as cargo for fuel or as troops transporter, each LéO 451 carrying up to 17 soldiers in their modified bomb bay.


After the French Liberation, the remaining LéOs were used to various tasks (mostly in Sea Air Rescue duties) and the lasts were flying up to 1956.

The French Strike Air Forces: A wasted chance ! (Revised 21 / 10 / 2013)

(All the data used in this post are from the book - in French - LéO 45, Amiot 350 et autres B4 de J. Cuny & R. Danel, Docavia #23, Larivière).

As I said previously, the program BR3 (Bombing and Reprisals, 3 places) emitted by the French Air Staff fave rise to 3 prototypes, one deriving from the recordbreaker Dewoitine 33, another was the Bernard 80 and the last being the Amiot 340. 

The Amiot 340

The Amiot 340 bomber was undoubtedly a very advanced and streamlined plane of monocoque metallic construction. 

Had it been submitted to normal process since it beginning and ordered as soon as ready, France could had a very strong bomber force.

The Amiot 340 bomber - The motor cowlings were very tightly streamlined: The CEMA said "too much" (!)

The Amiot 340 was designed in 1935 and several layouts were tested in wind tunnel. 

The construction of the plane began during the second half of 1936, disturbed by some long worker strikes. The plane was finished in the begining of February 1937. 

Unfortunately, the Air Ministry, which was the owner of the engines, did not accept to give to Mr Félix Amiot the wanted engines. 

It was an terrific illustration of what I dubbed "administrative viscosity", a special product of all the bureaucratic power. 

This bureaucratic product is detectable from some clear synptoms: 

• The initially specified goals are modified very often, 

• all the materials needed are released very late and scarcely and 

• the people in charge of the project never agree to any easy modification.

So begin the story of the Amiot bomber:

The bureaucracy wanted the use of the Hispano-Suiza 14Aa radial engine, based on a Wright license and providing 1100 hp. 


Unfortunately, this engine had been only recently developed (1935) from some smaller Wright engines and was not sufficiently known by its parent company Hispano-Suiza to allow a smooth development. 

Moreover, the engines were using 100° octane fuel, but in France, this fuel was only used by Air France. 

The Armée de l'Air used only of 85° fuel. 

So the cooling of the engines were not easy at all...

Mr Felix Amiot fought to discard these untested engines and to obtain Gnome & Rhône 14 N engines. 

This was accepted lateloy, the June 29, 1937. 

Then, the Amiot 340, with the old engine cowling of the previous Amiot 143, display good overall flying qualities but the cooling was poor. 

A new cowling was designed and manufatured, boosting the speed to 480 kph at 5000 m with engines providing 950 hp for take off, an altitude of 5000 m was reached in only 7 minutes and the bomb load was 1000 kg. 

An order of 5 preserie + 50 serie bombers was prepared. 

Unfortunately, Mr Pierre Cot, the Air Minister , belonging to the "radical" party was dissmissed in Januar 1938, having not finished that ordering. 

Having ordered the Morane-Saulnier 406 fighter in place of the Nieuport 161 and having refused the ordering of the Amiot 340, he shared his own and no negligible part of the French defeat in June 1940.

His successor, Mr Guy La Chambre, belonged to the same political party. He did not finish the ordering too. Why ?

However, when the Air Chief of Staff, general Vuillemin, went to Berlin in mid-1938 to visit the Luftwaffe, he chose the Amiot aircraft. 

He traveled from Paris-Le Bourget to Berlin at an average speed of 440 kph, displaying at least to his services how safe was this aircraft.

Five months later (May 1938), an order was send by the Air Ministry for only 20 pure B4 bombers following strictly the specification of the 1934 program (and not the Amiot 340 which would has been easy to manufacture as it was).

Who, in the French Air Ministry, could had hoped for a rapid industrialization of a so different aircraft ?

The Amiot 340 had a crew of 3 members, the new Amiot 350 needed 4, as she needed also a twin fins and rudders tail and a rear firing 20 mm cannon.

From a plane weighting less than 4800 kg, one derived another plane weighting 6500 kg. 

Unfortunately, all being to be reconstructed, so, at least a complete year was wasted in vain.

If you are wondering the reasons causing such a "bad luck", do'nt worry, they were certainly numerous but no black cat was never involved!

The first reason was a powerful lobby which supported the team designing the Lioré & Olivier 451 rival. 

In fact, the 2 planes were different and could easily have been ordered simultaneously. 

However, today, I think  that it was some problems of political power with some similarities with those displayed during the Borgia times.

This was not only the problem of the French Air Forces. 

It was also the case for the Armée de Terre, especially for the tanks (AFV): In 1936, Mr Louis Renault, who had invented the layout of all modern tanks with his light FT, proposed to the commission the very advanced tank ACK 1 more frequently designated as G1R. 

The tank Renault ACK1 on the gorgeous site chars francais (French Tanks) - compare it to those designed in the same period, including the T34, even the later the M3 Lee and the M4 Sherman!

This full scale mock up of this future AFV was at least 15 years ahead of these times: The armor was 60 mm thick, the main weapon was a powerful 75 mm / L29, the road speed was 40 kph.

If the decision have been taken imediatly, the first tanks might have been fielded in 1940. 

Instead, a unique prototype was in command in 1940 ! (The complete story of the G1 program was written in the monthly review Histoire de Guerre, Blindés & Matériels, #78, by Mr Stephane Ferrard.) 

In the two cases, some simple corruptions practices might be suspected



But other problems arisen for Felix Amiot. 

His main factory had been nationalized, that one might  translate, in fact, as robbed: The price of the plant was strongly underestimated, as also the numerous machine-tools, and the money was paid 2 years later. 

The banks don't wanted to advance money to buy new machine-tools.


All these hyper-authoritative behaviors were very frequents in these times, which were the times of the dictators. 

In USSR, Nicolaï Polikarpov, father of the I 15 and I 16 fighters, stayed in the gulag for the 15 last years of his life and was rehabilitated 13 years after his death, but only after the death of Joseph Staline. 

The fate of the mathematical genius Alan Turing, who lived in the so-called democratic UK, and who had played a so crucial role in the Victory against Hitler (deciphering of the Enigma codes), was not better at all, inducing him to commit suicide. 

the Amiot 351 / 354 bomber

Fortunately, for Mr Amiot, his engineer team stayed with him. 

Now we have to examine the changes needed to metamorphose an Amiot 340 BR 3 in an Amiot 351 B4. 

The only conserved parts were the wings and the fuselage with its modular conception.

First of all, it was required to fit a twin fins and rudders tail in order to use what was seen actually as a very powerful weapon: A 20 mm cannon. 


Unfortunately, it was a very stupid specification based on a funny belief! 

The so-called military deciders were absolutely convinced that a bomber was of course faster than any fighter. 

Such a belief was the consequence of the appearance of the Heinkel 70 at the Paris Air Show in  1934. 

This German aircraft had a retractable landing gear and a perfectly smooth skin and was really faster than the actually fielded fighters which were technologically aging. 

So, if the fighters were only marginally faster than the bombers they were attacking, they were supposed to attack them mostly from behind. 

So, a twin fins and rudders tail might allow to the gunner to down easily the imprudent poor fighter. 

The Amiot fitted with that device were designated as Amiot 351.


Unfortunately, this layout was generating several shortcommings. 

First, with the increasing speed, the turbulence created by the motors may interact with the 2 vertical surfaces, which then may begin to vibrate, inducing torsion in the stabilizer. 

To avoid such a problem, one must strengthen the stabilizer which became significantly heavier. 

The CEMA rejected rightly the first presented twin fins and rudders, afterward he rejected too the second then, also, the third, leading to the conservation of the classical layout (designated Amiot 354). 

Nevertheless, some Amiot 351 were produced.

Amazingly, all the pilots who flew them were enjoyed by their flying qualities. 

This bomber became very popular for them and general Vuillemin exacted to manufacture more Amiot 351 than LéO 451.

The most aggressive criticisms against the twin fins and rudders of the Amiot 351 were those of the follower of the LéO 451. 

What is very odd, is that we know, today, that none of the Amiot 35x bombers crashed owing to their twin fins and rudders, unlike the numerous crashes of the LéO 451, owing their bad stability during take off.

Such historical facts are appalling, because they demonstrated the CEMA test pilots were not fair at all. 

Unfortunately for French people, they acted as if they were members of an underground secret society for which the fate of the French Nation did not count at all.


Another urgent problem the Amiot team had to solve was the integration of two radial engines to a streamlined aircraft.

By definition, such engine present always an important and unavoidable section area: Its skin must be cylindrical. 

The only way to fix such a huge aerodynamic weakness is to work on the shape of both extremities of the engine envelop.

It was not very easy to do, because the cooling of the engine use a huge amount of cool air, inducing a significant air intake, as, also, an even larger hot air exit.


An interesting work was done by the chief Engineer PE Mercier of Lioré & Olivier. 

He  designed a sophisticated cowling which were aerodynamically very efficient. 

Two shortcoming appeared with this revolutionary cowling: First, all its users, including the Germans, experienced a lack of cooling efficiency. Second, it was very difficult to maintain the engines fitted with it.

The cowling of the engines used in the Amiot 143 were not good, but sufficient to cool the 860 hp engines of an aircraft flying at only 310 kph. 

Used in an aircraft flying 50% faster, it induced huge turbulence which prevented a good way  to the cooling air.

The new cowling, using an air intake of only 76 cm in diameter, allowed very faster flights and inducing a far better cooling.


Unfortunately, during a CEMA test, a climbing to high altitude ended with an engine damaged.

 It's impossible to suspect a lack of proficiency for the implied pilot.

So, knowing the hatred of the CEMA test pilots against Mr Amiot, it was likely that such an incident was a shrewd sabotage occurring after a long pre-flight station with the motor running, followed by a full out climb at a just too low speed. 

If you have read my post on the Bloch 15x fighters, you may remember the problems of the cowling air intake!

The simple low was that the better cowlings were those which had the narrowest air intakes. 

Nevertheless, we know that, as early as the speed of the Amiot 350 exceeded 240 kph, the temperature fell to a normal level.

The method to avoid heating problems was to do a quick taxiing and to take off as soon as possible.  

It was especially relevant for a bomber at war, which has two "jobs": Either, it was attacking, or it was in maintenance. 

Taxiing slowly on the ground was the better method to be strafed by Messerschmitt fighters.

Very good performances

The top speed was 485 kph at 5000 m, the cruising speed was 420 kph and the ceiling was 9000 m.   

The total range at this speed with a bomb load of 1.3 tons was 2500 km. 

The economical speed of 360 kph allowed to have a 3000 km range.

Amiot 351 - the twin fins and rudders are characteristic

Amiot 354 - a classical tailplane

The climbing speed was 8'42" (an average instantaneous climb speed of 7.7 m/s = ~1540 ft/min).

All these performances were very good.

Unfortunately, some problems were remaining. 

Regarding the armament, the most crucial was the bomb traps, which was conceived to retract inside the bomb bay. 

This sophisticated conception was, indeed, very advanced for the times but still not controlled. 

This device, moved hydraulically, did not work, inducing the need to fly with open traps, wasting speed. 

A manual device was in progress, but to late.

Another problem was the defensive armament. 

The Amiot 340 was conceived initially for only 3 riffle caliber machine guns, a very, very weak protection.

The Amiot 351 / 354 were to have a stronger armament, especially with the dorsal rear firing Hispano HS 404 20 mm cannon. 

Only one forward firing 7.5 mm MAC machine gun and another one under the belly were exacted.

The bomber manufactured in June 1940 were armed with 2 forward firing MAC machine guns, the cannon replaced by 3 MAC machine guns and the belly machine gun was to be reinforced by 2 others, all of them being stuck on the radio-operator trap as a vibratory device.

The HS 404 cannon was discarded because the streamlined cockpit, tapering downstream, was too cramped to allow the needed moves during a combat. 

Mr Amiot proposed a simple mount of 3 Darne mle 33 riffle caliber belt fed machine guns. 


Unfortunately, the Air Ministry, which had several thousands of them, refused. It preferred the drum fed MAC... it's difficult to understand its reasons.

These problems were to be solved for the mid-summer of 1940...

Unfortunately, the most serious problem was the bureaucratic blockade of the manufactured Amiot bombers. 

A lot of them were left on stocking airfields like Le Bourget, with bureaucratic technical officers dissuading pilots to fly these aircrafts.

By chance, an high rank pilot officer went to Le Bourget to fly an Amiot 351 bomber. 

With another pilot, belong to the Air Ministry, they took off, against the warning of an officer of the CEMA, who said this aircraft was to dangerous. 

It was an eye-opener! 

That aircraft was delightful, very easy to fly, performed very well and very maneuverable (OK, they did not test the aerobatics...).

Worst of all, they go to the Ministry to relate this experience. 

So, the Ministry called the chiefs of some bombers units to give them all the available planes.

In action!

All the operational pilots who flew the Amiot 351 or 354 were enthusiastic on her flying qualities. 

Too much! 

They became often to hazardous, as colonel Dagnaux, who flew at 600 m AGL (2000 feet) at night, above a German column after the May 10 in the Ardennes, having forgotten that 2 engines of 1050 hp each yield a lot of noise and also very visible flames. 

So, this bomber was downed by the Flak.

The May 20, 1940, the general in chief Gamelin was dismissed and replaced by general Weygand. 


The following day, general Weygand used of two Amiot bombers to fly to Dunkirk, escorted by a squadron of Bloch 152. 

There was no problem at all. 

This demonstrated that:

• the Amiot was really very fast;

• the German did not had a real mastery of the skies, and...

• the French Army had no leader at all for a very crucial day !

During the battle of France, about 85 Amiot bombers were delivered by the Amiot factory.

A bit more than 60 were used at night for offensive scouting flights (with their bombs). 

Among them, 2 disappeared in accidents (linked to sabotage), 5 were downed and 6, damaged, were later burned. 

198 were at various stage of finition in the factory.


After the defeat of June 24, 1940, most of them were used in transportation role.


These results are not good, but a bit complicated. 


But the inconsistency of the politics was the major obstacle to the smooth development of a good bomber.

The French Strike Air forces: The missing link...

The year 1934 appears now as a temporal node for the technology of military aircrafts. The military air forces around the World were using mostly bombers which cannot fly faster than 230 kph, but some more recent planes exist which were able to fly faster than 300 km/h.
If the US Martin B 10 was a little faster - 343 kph - she was the forerunner of a new generation of bombers gathering all the advances in the domain.

 For exemple, the Junkers 86 (325 kph) and the Dornier 17 (410 kph) bombers flew first at the end of 1934.
So, the French Air Ministry decided to launch 2 military programs for the procurement of fighters (top speed: 450 kph) and, four monthes later, bombers (470 kph).

Amazingly, the French deciders wanted bombers faster than their fighters, demonstrating an obvious complete lack of proficiency about what happens during a fight in the sky.

These deciders, likely, were persons who cannot reason in a three dimensional world. Their minds were overwhelmed by the fight between sea battleship in which the gun caliber was of paramount importance.

Furthermore, the bombers they wanted had to be twin-engined, but one such aircraft with 2 x 1000 hp can be seen, roughly, as using 3 fuselages, with 6 interactions zones with the wing. So, the drag of such a bomber is larger than the one of a fighter using of the same engine.

So, a previous program, known as BCR - Bombing, Fight (Chasse in French), Recce - has been near fruition in 1935. This program had the ill-ambition to give the aerial cruisers described in the book of general Giulio Douhet.
French deciders were not alone with such a vision, the Dutch decided to buy the Fokker T.V (417 kph) and to cancell the orders for Fokker D XXI fighters...

Nevertheless, there was 4 BCR prototypes which appeared in France. The first two of them to be ready were ordered, and it was not the best choice at all.

Potez 540

Among them was the Potez 540, with 2 Hispano-Suiza 12X engines of 700 hp.

She was a rather light bomber (less than 3900 kg empty), manoeuvrable, fitted with a retractable landing gear. Her top speed was 320 kph at 4000m (13250 feet).

Potez 540
fiche technique sur aviafrance

This plane was of mixed construction (for easier repairs). 
The bomb Load was 900 kg among them 500 kg were housed in the fuselage.
The defense used of 3 riffle caliber machine guns, inducing the stupid nose turret.
More than 250 were ordered.

They fought gallantly in Spain (to the Republican side with André Malraux who wrote one of his adventure in "l'Espoir").
When they were facing the FIAT CR32 of the Aviazione Legionaria without fighter escort, they were hopeless, as usually for any bomber facing modern fighters.
After the mass arrival of soviet planes, these bombers were vilified by the Russian as it's frequent between allieds. 
But, if the Potez 540 were clearly slower than the Tupolev SB2, they were fitted with self sealing fuel tanks, allowing a better resistance to gun fire.

An upgraded version appeared later, the Potez 544, with 2 Hispano-Suiza 12Y. 

The top speed might had been 350 kph but the ceiling exceeded 11000m, giving her an interesting role as spy plane. 

However, few of them were ordered. Neve.rtheless, this plane cannot be seen as more survivable than a Bloch 210

Bloch 131

The second aircraft ordered was the Bloch 131. 
This aircraft appeared as clearly more aerodynamic than all her forerunners.

Bloch 131
technical data

The Bloch 131 prototype was able to fly as fast as 385 kph. 

Unfortunately, she suffered from alarmingly strong vibrations. 
Due to a wrong interpretation of this phenomenon, some reinforcements were proceeded, adding more than 1000kg to the bomber. 

It was then discovered that the vibrations were induced by motor cowlings on the horizontal part of the tail. 

But, now, the French Air Staff was following the same stupid "fashion thinking" than the British one for the Witley and ask to Marcel Bloch a shorter take off run.
As for the Whitley, the solution found was to increase the angle of the wing. 
So, the Bloch lose 2000m of ceiling and 35 kph in top speed, at 350 kph. 
Her bomb load was only 800 kg.

Pilots were able to make aerobatics with this plane, but was it so usefull?

More than 140 of this bomber were manufactured ans given to recce squadrons. 

But, used without fighter escort for recce in 1939, they suffered heavy casualties and were withdrawed soon. 

Two better contenders would have been chosen. They were later, because they were more advanced.

Bréguet 462

The first one was the Bréguet Br.462, the perfected progeny of the Br.460, an interesting aircraft able to fly at 385 kph but with too many problems (even most of them have been solved when she was given to the Spanish Republic).

The Bréguet 462 

This new aircraft was aerodynamically refined, stable, reliable, faster and more manoeuvrable.

She had a top speed of 405 kph, a ferry range of 3000 km, a ceiling of 8300m and abomb load of 1500 kg.

It was one of the very few aircraft for which the CEMA had not expressed criticisms!

One bomber was ordered by Japan, the other by USSR, only to study the Bréguet process.

She was not ordered for France, as it was written by engineer Louis Bonte, "because she did not correspond to the new program B4, for which the Lioré-Olivier 451 was the type" (Histoire des essais en vol, Docavia #3, 1974). 


What a spectacular example of bureaucratic literature! 

So, France was continuing to manufacture one year more several dozens of Bloch 131 flying at most at 350 km/h. 

And these bureaucrats were refusing to order a very better plane, flying 50 kph faster, able to use twice the bomb load!
Moreover, with the better engines available in 1938, the Bréguet 462 could be able to fly even 25 to 40 kph faster, being strictly competitive with the Heinkel 111 P of 1940.

Obviously, as quite all bombers, she would need fighter escort. 

But the time needed to complete a bombing mission could have been significantly shorter than for all previous bombers. 

Furthermore, the Bréguet 462 was ready to be manufactured in time for being operational at the beginning of 1938, giving to Mr Daladier - equivalent to Prime Minister for France - an opportunity to make a more courageous choice at the Munich conference.

Another argument is that the availability of such a plane allowed the perfecting of the B4 bombers among them no one was ready to go to war.

Apparently, none of the French actual decider was aware of the time needed to engage a completely new industrial process, including all the new technological equipments.

The second chance wasted

Previously, I told you there were 2 contenders wrongly rejected.

The second one was the Amiot 340. 

A very advanced aircraft, able to fly at 480 kph.

I will told you about her in another post, soon.