mardi 24 juillet 2012

The Bloch MB 150/1/2/5: Good fighters, irrelevantly used, but what a superb progeny! (Revised 25 / 01 / 2014)

The difficult beginning of an exceptional success story

(the main sources used to write the following post was: The “bible” for the MB 15x fighters: The Bloch 152, by Serge Joanne, Lela Press; The series of articles in the Album du Fanatique de l’Aviation; The testimonies published in Icare [serie: La Chasse]; Several very interesting papers in Avions and in Aéro-Journal)

The Marcel Bloch MB 150 fighter was designed by engineer Maurice Roussel, who previously designed the MB 200 and MB 210 bombers. 

If, today, this fighter may be seen as very classical, it was not the case in mid-1936. 

First, it used a radial engine, a kind of engine inducing automatically a bulky nose, signifying some loss of performances for aerodynamic reasons.

It was the first attempt of Marcel Bloch in the realm of this gorgeous category of aircrafts, the only ones able to protect a country against the enemy’s threats.

The team responsible for the conception of the prototype of the Marcel Bloch MB 150 had made a lot of work to display the newborn fighter at the end of June 1936. 

Unfortunately, the take off could not be achieved already. 

So, engineer Roussel was fired.

However, the various problems encountered were not in the plane main conception, but in a sum of little mistakes.

In late spring 1936, the political situation have changed, the “Front populaire” actually leading France: One of his numerous goals was to nationalize the defense industries. 

The leftist politicians have said that was a just principle, because all these plants were working only with public money. 

But, it was not the true motivation, which, in fact, was only to give some comfortable jobs to some incompetent lobbyists (it's more easy to see that from today).

Very quickly, the lobbyists demonstrated their poor managing qualities and the previous boss were put in charge of their ex-own plants! 

So, Marcel Bloch (as, among the others, Mr Henry Potez or Emile Dewoitine) became “administrateur délégué”, but he had not the liberty to do what he feel the best: Before any action, he needed to submit all his decisions to some committees....

Various factors explained the failure of the maiden flight of MB150. 

In the 1936’s France, the airfields, most of the time and, at first, the most used ones, consisted in rather short, bad and irregular grass surfaces (described by Jacques Lecarme, test pilot engineer in Histoire des Essais en Vol, Docavia #3, 1974)

The landing gear of the Bloch fighter was very short, may be to favor a best sight for the pilot, but enhancing the fear of the pilot to collide his propeller with the ground. 

The 930 hp Gnome & Rhône engine was not fitted with a reduction gearbox, so the air-screw, despite its small radius (2.55 m, ~8.5 feet), was completely inefficient (once in flight, the extremities of the blades exceeding too much Mach 1).

A fine general conception

Some other countries also used of radial engines for fighter planes (USA - P35, P36 for the USAF, F2A1, F4F3 for the Navy, USSR Polikarpov I 16, Italy CR42, G50, MC200,  and Japan Ki 27 and A5M4).

In fact, the main layout of the Bloch was aerodynamically and practically far superior to all these aircrafts. 

Bloch MB 150 - (after her maiden flight)

For example, her wings was very thin (14% of thickness) and her fuselage was well streamlined. The only clumsiness of the Bloch design may be found in details (which were all successively eradicated).

All the fighters of that period shared a tail wheel, inducing a nose up attitude at rest and during the very beginning of the take off. So, the pilot views were blinded by the bulky engine. 
The disturbed lines, rather frequent in the design (illustrated by, e.g., the Fiat G50) of her contemporary concurrent using also of radial engines, may be explained by the introducing of a camel hump to offer a good forward view to the pilot. 

Marcel Bloch retained a very advanced pilot position, rather similar to that of the Breda 65. Such a solution was aerodynamically more efficient than the camel hump.

During five months, the work on the MB 150 seemed to be stopped. But early in 1937, Marcel Bloch resumed the work on the MB 150. 

In French specialized publications, one can read - to explain the revival of the MB 150 - the French Air force Staff was concerned about possible shortage affecting the Hispano-Suiza 12 Y engines needed for the Morane 406 fighter.

In my own opinion, such a tale is very difficult to accept: 

The Air Staff had previously chosen the Nieuport 161. 

But, after her crash, the Nieuport was vilified, excluded from the contest (!) and the active lobbying of some politicians achieved the ordering of the Morane 406.

However, all competent military French deciders - yes, they existed -  were knowing perfectly that the performance losses induced by such an order could be catastrophic. 

So, they sent some cautious messengers to MM Bloch, Dewoitine and Renault to ask them to resume their works.
As may be you know, the Dewoitine 513 used the same engine as the Morane 406: This is the proof that the lack of Hispano engines was not true, and the French military deciders displayed a real lack of moral courage... against the lobbyists. 

This behavior is always possible in every country...

Nevertheless, the perfecting of the Bloch fighter required a lot of modifications. 

Marcel Bloch had previously never been involved in the design of any high performance plane. 

So, as any engineer creating a fighter dynasty, he had (as all his staff too) to learn all the high speed aerodynamics and its associated structural consequences.

The wing was enlarged several times, the landing gear became taller, the engine cowling was slightly refined and the engine was replaced by a slightly more powerful one.
The result was the first flight achieved the May 4, 1937.

A new engine was already fitted, using a 2/3 reduction gearbox instead a direct drive and allowing the use of a 2.9 m in diameter air-screw: The top speed reached 434 kph at altitude (the same as the one of the Morane fighter).
The engines appeared always as insufficiently cooled for two reason:
a)     using of the 85° octane gasoline instead of the 100° one,
b)  the very long time of ground rolling expected by some statutory (but completely irrelevant) usages.

Even the engines were not bad at all, they became so powerful that a complete redesign was needed to take into account a lot of new constraints. 

This redesign was done, leading to the 1600 hp class Gnome et Rhône 14R Météor, unfortunately a little too late.

Overwhelmed by a lot of shortcomings, the engine makers were not able to define a cowling which can be aerodynamically efficient, allowing to satisfy the pilots who needed the highest possible speed, and also mechanically efficient, allowing to satisfy the mechanics in minimizing any wasted time for them.
So, like his colleagues Amiot and Bréguet, Marcel Bloch should have independently developed a lot of cowlings for the same GR 14 N engines. 

OK, may be, do you think it was stupid to do three times the same work while Hitler and his Nazi Reich was so close of  triggering the WWII. You are right...

With a new cowling, a larger air screw and a spinner, the MB 150 M (for modified) achieved a top speed of 480 kph. After this reasonable achievement, the radio equipment and the armament were fitted.

A new experimentation of cowling seemed to be necessary, with a diameter of the air intake started from 0.85 m to be enlarged up to 1 m – this being the standard fitting on the MB 151 - and to decrease again to 0.85 m when cooling flaps were fitted.

MB 151 prototype, with the efficient cowling of 0.85 m in diameter - photo on the site aviafrance

Unfortunately, this later cowling was never used for the MB 151... 

The top speed of this last fighter was, at least, 460 kph without exhaust pipes. 

serie MB 151 with the huge air intake of 1m in diameter
the original legend is MB 152, but its impossible: it lacks the wing cannons HS 404

With the new cowling and exhaust pipes, her top speed could have reached more than 480 kph, a speed similar to that of the Amiot 350-01 used by General Vuillemin to fly to Berlin in summer 1938, at a 440 kph average speed with narrower air intakes. 

And we know today, the cooling of her engines was good above 240 kph.

How irrelevant was such a decision! 

With a speed of 460 kph, the MB 151 experienced some difficulties to catch some bombers. 

Fitted with the best cowling and the exhaust pipes, the MB 151 could had reached a far better fate.

With the narrow air intake of the late cowling, fitted together with exhaust pipes and the more powerful GR 14 N 49, the MB 152 prototype achieved a top speed of 515 kph, a jump of 30 kph! A narrower air intake – 0.80 m – was used for the latest operational Bloch fighter, the MB 155.

All these cowling problems were responsible of one complete year of delays. 

May be, Marcel Bloch could have taken some advantage if he had chosen the efficient - but very complicated for maintenance purpose - Mercier cowling...

MB 152 on aviafrance site - the leftest plane is fitted with the "good" cowling, the following, not, but all display their  starboard canons !

Nevertheless, the most interesting thing is how strong was this experiment for him. 

The MB 150, starting with a to speed of 434 kph, culminated, with the same layout, to 515 kph. 

This progression of 80 kph was obtained together with better handling qualities and better lateral stability and, even, a complete redesign to divide the aircraft in modular blocks for a faster building: a lot of work in a very short time

Another complete redesign was done by engineer Lucien Servanty (who, later, designed the supersonic Concorde) late in 1939, to take advantage of the powerful GR 14 R engine, ending at the gorgeous MB 157, with 2 m² larger wings, an airplane able to fly faster than the FW 190 (710 km/h with military power - 15 minutes max - and 680 kph for normal max power,  and the climbing to 8000 m reached in 11').

In action

The MB 151 was used by at least the GC II/10 and III/10, in the French Air Force, and by the Aéronavale squadron AC 3.
The results of their fights is not bad, for example, one pilot of the GC III/10 downing a German bomber and a Bf 109, but was wounded and forced to land during the same combat by other German fighters.
The AC 3 fighters were most accustomed to protection missions and experienced successfully their MB 151 to protect their bombers, some convoys in the Channel and their own airbases.
When, the June 15, 27 Italian fighters attacked the naval base of Toulon, the alert was given very late. 

The three patrols of the AC 3 took off just in time (a few time before noon). 

They were overwhelmed (9 vs 27), 2 pilots were killed in action, another one (SM Le Bihan) died after a forced landing ended by a collision with a tree. 

The peculiar fact is that this pilot, before his forced landing, collided voluntarily with a Fiat CR 42 fighter, which was downed.

However, this first encounter with the very nimble CR42 biplane resulted in 3 Italian fighters downed. 

According to the testimony of a French artillery officer, they have not be destroyed by the D 520 of the GC III/6 which were still on the ground.

Among these 27 seven Fiat CR 42, only 2 returned to their base... As it was very frequent in this war, the Italian want not recognize the value of the French fighters, as the Germans have done, preferring being downed by British ones. 

This was the same behavior for the British in North Africa against the Italian fighter, preferring to be downed by Germans.

This war was a racist one, but you may know that...

As it was said the Bloch fighters were unable to cross thee Mediterranean Sea, the AC 3 pilots achieved that job successfully before the June, 25, 1940, using a refueling at Ajaccio, in Corsica, and landed safely at Bône (the antique Epone and now Annaba).

Another country fought with the Bloch 151 fighters: Greece. 

Unfortunately, when the Greeks ordered 24 MB 151, the Germans were about to launch their Fall Gelb against France and all democratic countries of Western Europa. 

So, only 9 MB 151 were delivered to Greece. All of them have been previously used by the Armée de l’Air and their engines were worn out. 

The Greeks having got no spars, so they used only 5 MB 151 fighters, the others being used as spars sources.

Nevertheless, these fighters seemed to be the best fighters of the Royal Hellenic Air Force. 

They appeared fairly efficient against the Regia Aeronautica

But, when the Germans interfered, only 2 were still airworthy, and in few days they were eradicated.

The Greek pilots were efficient to protect numerous strategic points and they have got from 5 to 7 victories! A rather good performance against so overwhelming forces!

The Bloch MB 152 performed very better than the Morane 406 and scored very better. 

Even in the worst definitions, they can fly at least 30 kph faster, but those which were fully operational were able to fly at least at 505 kph at altitude, to climb to 4000 m in 6’12” and to reach 8000 m in less than 16’. 

With a VNE of 660 kph (IAS), they were able to dive faster than the Curtiss H75 (VNE : 550 kph IAS) and also faster than the actual Hurricane (Jean Nollet, in Album du Fanatique de l’Aviation, #11).

Their armament was the strongest of the world until the appearance of the FW 190 in 1941.

The fuel tank was special, allowing absolutely any negative g maneuver.

Finally, the structure was especially robust, allowing to some pilots to return home in spite of having been hit by up to ten 20 mm shells and more than 100 bullets machine gun!

This quality was essential in the overwhelming superiority of the Jagdwaffe.

Nine Groupes de Chasse (18 squadrons) of the FAA used these fighters and claimed 188 victories, among them there were 51 Messerschmitt Bf 109 and 27 Bf 110, to be compared with the 187 victories claimed  by the twelve GC (24 squadrons) using the Morane 406.
The most successful Bloch 152 equipped GC was the I/8, claiming 44 victories among them 36 were confirmed. The best GC using Morane fighters claimed 36 victories among them 29 as confirmed.
I have not included the local patrols protecting airfields or aeronautic factories, but they claimed 18 victories among them 12 were confirmed.

After the Armistice, 320 Bloch fighters were in the Free Zone of France: 49 MB 151 (20 needed some repairs), 245 MB 152 (72 needing some repair) and 8 MB 155.

This assessment is not bad, knowing the bad conditions in which the fighting was engaged.

Irrelevant starting position

As you can see on the map of the North part of France, all fighter squadrons were firmly stuck to one specific area, each one of these areas being dubbed groupement

Some of these “big” units were gathered in Zone d’Opération Aérienne, the two ZOA illustrated in this map gathered 630 single engined fighters over a grand total of 900 for all the French Air Forces (including the Morane 406 available in Lebanon[!] ).
The distribution of the fighter squadrons for May 10, 1940, seems rather odd!

Personal document of the author - Locations of the French fighters groups for the May 10, 1940

Five GC were close to Rheims, the two nearest from this town being equipped with Curtiss H 75 fighters, the 3 others with Morane-Saulnier 406. 

Four others GC (1 on Bloch 152, 3 on MS 406) were a little more far from the Belgian border. 

All these GC seemed dedicated to the protection of Paris and also to protect the limit between the tough Maginot Line and the less protected one (Ligne Maginot Prolongée).

Four GC (2 equipped with MB 152 and 2 with MS 406) were stuck in the immediate vicinity of the West Belgian border: Their squadrons could have no delay to escape any enemy attack.

There was 5 GC in the vicinity of the Seine river, 4 with MB 152 and 1 with MS 406.

Four other GC were on the East part of this map, 2 equipped with MS 406, 1 with H 75 and 1 with MB 152.

The last  Bloch equipped GC, the III/9, was in protection of Lyon. 

It claimed only 4 victories during the Battle of France. 

This poor score is the consequence of an irrelevant warning system as also of the bad positioning of this GC.

One can see the huge empty spaces with no defense squadrons. 

The organisation by GC had divided by a bit more than two the number of the airfields, allowing some reduction of the mechanics. 

But the take off points were also reduced by the same amount, and, knowing the poor training of most of the AA artillery protecting the airfields, the Germans attacks were more “juicy”.

The Bloch fighter entering service relatively late, they were not positioned in the place were they can be quickly engaged in skirmishes during the Phoney War. 

In the actual France, somebody thought the fighting did not give experiment!

As several hundreds of Bloch fighters were already produced, it could have been possible to position their squadrons in first line. 

The obsolete Morane 406 could have been used to protect the factories and the great cities.

The Bloch 155 entered service in June 1940. 

She was used a much more sophisticated cowling, a more streamlined fuselage.

A 700 l fuel tank was fitted (300 l more than the MB 152), as, also, a 40 mm thick triplex windscreen. 

The top speed published of 520 kph. 

This is likely the lowest top speed accepted by the French Air Force for fighter just out of the plant. 

The true top speed could have been about 530 km/h, the same than the Bloch 174 recce twin engined which used the same engines and the same cowling.

Captain Coutaud have got a victory with her. 

A more powerful engine (~1200 hp) was about to be available for her. 

Bloch MB 155 - on a muddy airfield, but showing all the differences with the MB 152.  The triplex windscreen is beautiful.

One prototype of the MB 155 flew with 4 Hispano-Suiza HS404 cannon...  

The last Bloch fighter belonging to this family was the Bloch 157. You may read my post on her: Click here.


In 1940, despite all the success obtained by Marcel Bloch, the lobbyists have won, and Marcel Bloch was fired from his job. 

After the defeat, as a jew, he was put in custody by Vichy police near Lyon and, after the German occupation of the so-called “free” France, at Drancy. 

In August 1944, he was deported to Buchenwald nazi concentration camp, where he was protected by French communists militants (!).

He returned home in 1945. In 1946, he change his name to Bloch-Dassaut (the name his brother Darius had used during the Résistance). 

Three years later, he changed definitively to Dassault.

At the Liberation time, the aeronautics bureaucracy had published a new program for a very heavily armed fighter. 

The nationalized companies were working on very heavy fighters, the best one being the SO 6020 Espadon designed by Lucien Servanty.

But Marcel Bloch did not think that was a relevant specification. 

He know better the financial and technical problems in the actual France than the so-called high-engineers, and preferred a much more light plane: That was the MD 450 Ouragan, which used a lot of structural solutions of the MB 150!

The lesson which one may derive from that story is how important is that Marcel Dassault had demonstrated a perfect capacity to adapt himself and his planes to any situation, and he had learn how essential is the independance of his Nation.

2 commentaires:

  1. Bonjour!

    Merci beaucoup pour cette article qui m'a aidé à comprendre pourquoi les derniers MB 152 étaient plus rapide des précédents, tout en ayant un moteur seulement d'un peu plus puissant.

    J'ai récemment trouvé ce manual:

    cependant, qui rapports un altitude de maximum vitesse de 5400 m, au contraire de l'"habituel" 4000 m. Je pense qui il est plus correct, parce que il compte la récupération de pression dynamique. Je me demande si aussi le 515 km/h qui vous indiqué sont obtenu a plus haute altitude et avec quel variant de moteur.

    Pardonnez pour le mauvais Francais, je suis Italien.

    1. Merci pour ce manuel de vol (qui traite effectivement des MB 152 à grosse entrée d'air, ceux du début de série).

      Vous avez raison, l'altitude réelle de vitesse maximale était en général de 1,300 à 1,500 m au dessus de l'altitude "de laboratoire".

      Votre Français est parfaitement compréhensible : Bravo !
      Thank you for this handbook, which has been written when the MB 152 were fitted with an air intake of 1 m diameter.

      You are right, the 4,000 m (laboratory altitude for the G & R 14 N 49) + 1,400 m (dynamic pressure + lower temperature) = 5,400 m !