mercredi 24 octobre 2012

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.












1 commentaire:

  1. "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 developped by Wright (1935) and was not suffciently known by its parent company to allow a smooth developpment by Hispano-Suiza".

    Le 14 Ha (plus tard 14Aa) n'a pas été développé par Wright, mais directement par Hispano qui avait mixé des brevets Wright et des recettes maison. La preuve en est que, alors que les 9V et 9Q qui étaient des moteurs Wright à peine francisés n'avaient pas de n° d'étude moteur, les 14 Aa et 14Ab en avaient... Et le premier 14 cylindres de Wright, le R-2600, diffère sérieusement du 14Aa - bien que comme lui, il n'ait jamais vraiment bien fonctionné dans ses premières versions...

    Cordialement

    Alain

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