samedi 31 décembre 2016

The ANF Les Mureaux 190, a murdered Prince of the Air (Revised 12 / 07 / 2017)



{Main sources: The  French aerial reviews Les Ailes, # 806, p.6, November 26, 1936, and L'Aéronautique,  November 1936}




The lightweight fighter contest (in the French 1934 program)



The program of July 1934 stipulated:
  • A top speed exceeding 450 kph at altitude, 
  • A climbing time inferior to 6' to reach 4,000 m,
        •             15'        "      8,000 m, 
  • An armament of, at least, 4 riffle caliber machine guns.
A fighter lighter than 1,900 kg may use an engine of the 500 hp class.
That very exception among all other fighter programs published around the World resulted from the exceptional results of the Suzanne Deutsch de la Meurthe's Cup whose main rule forbade any engine having a displacement of more than 8 liters: It resulted quickly in an spectacular race to the better fineness!

Another motivation of this new lightweight fighter program was economic: A lightweight fighter would be less expensive.
Her less powerful engine would need about the half part of the fuel used by the other fighters. 

Following this way, it was expected that the French Air Force would quickly gather an important amount of modern fighters. 

Such an innovative - and absolutely logical - policy failed for many reasons, except for technical ones. 


The only ordered lightweight fighter was the Caudron-Renault CR 714, manned by the Polish pilots of the groupe I/145.

Thez fought gallantly against the Luftwaffe during 10 days of Juni 1940, with clearly better results than any Morane-Saulnier 406 unit.

However, the most performing of these fighters was the ANF Les Mureaux 190 (in short Mureaux 190), designed by chief engineer André Brunet in 1935. 




The engines



All the engines expected for such an use were air cooled: That may be explained by there lighter weight (the liquid cooling implying about 100 kg of cooling liquid and radiator).

If the air cooled Renault inverted V, 12 cylinders R 01 engine, is relatively well known, many other light engines have been developed in France at this time by the companies:


  • Bloch, 
  • Delage: 12 CEDirs, initially designed for the Suzanne Deutsch de la Meurthe Cup. It was both liquid and air cooled. It was developed by Farman. Displacement : 11.4 liters.
  • Potez: Potez 12 D, a flat 12 with a displacement of 17.6 liters, the lightest - 335 kg -and the most powerful of the contenders - 485 hp - initially designed for the Potez 63, 
  • Régnier,  
  • Dewoitine: Béarn engine, 
  • Salmson:  12 Vars (which see). 
All were air cooled but, actually, because of the consequences of the 1929 US economical crash, few teams had the real financial capability to achieve the production process of an engine.

Two other engine are commonly associated with the light fighters: The Hispano-Suiza 14 AB (diameter 1 m) and the Gnome & Rhône 14 Mars (diamete96 cm).  

They were chosen for most of the twin-engined fighters and for two single-engined ones:



  • The Roussel 30 all-metal diminutive fighter-bomber, which looked like a MB 152.



  • The Bloch 700, made of wood, designed by Engineer André Herbemont, former designer of the Spad 20 to Spad 710 fighters.

  • The Renault engine, whose 6-cylinders blocks were already used in the Simoun and in the Goéland general purpose aircrafts, was obviously chosen by Caudron-Renault for the CR 710.

    Another fighter prototype will use of the Renault engine, the tiny Romano 130 biplane, which was said as never built. 

    But it's easy to see her shape in 3 view drawing published in actual reviews. 

    Likely, the prototype stayed uncompleted (as it was also the case for the twin-engined Loire-Nieuport 20, for which it remained several pictures of the structure), after the disastrous choice of the Morane 405 in 1936.


    Later, the Arsenal VG 30 was conceived to use of the Potez 12 D engine but was completed with the heavier and more powerful Hispano-Suiza 12 X. So, in 1939, she became the VG 33 which entered service in June 1940 with the HS 12 Y 31. But she was no more a lightweight fighter.


      
    For the Mureaux 190 fighter, the chosen engine was the Salmson 12 Vars, which, obviously, had never be flown before.

    The displacement was only 13.7 liters, much smaller than the others engines (the Renault had 19 liters...).

    Weighting only 300 kg, initially, its weight arose to 360 kg at the end of 1936. 

    The layout was an inverted Vee 12, because it minimized the cross section of the fuselage, favoring a better fineness. 

    The bore was 110 mm and the stroke 120 mm.
    Each row of 6 cylinders was surrounded by a twin cam arrangement.

    These data explain the 12 Vars may run very fast: 3,800 rpm (L'Aéronautique, December 1936), more than 4,000 rpm were expected.

    The compression  ratio was 6.

    The maximum power delivered was expected as 500 hp (~37 hp/liter), but it's likely that only 450 kph (33 hp/liter) were obtained in 1936.

    The reduction gear-box was designed for the use of an HS 404 20 mm gun, allowing an armament exactly similar to the one of the MS 406 (or to the Nieuport 161)!

    The only one difficulty of this engine was the lack of experience of the designers with it.





    The Mureaux 190: A lightweight fighter... really very light



    This fighter was an all-metal stressed skin monocoque.

    The weight were 850 kg - empty - and 1,300 kg for take off, giving power loading of 2.80 kg/hp.

    She seemed a little outclassed to the observers who discovered her fixed landing gear.

    However, that was not the case at all: André Brunet had chosen wings having 12% of relative thickness. 
    Such wings - very little and thin were not suited, actually, to be fitted with a retractable landing gear.




    Mureaux 190 - 


    By their elliptic plan form, the wings, as the ones of the Supermarine Spitfire, followed a tendency demonstrated by the advanced Hanriot 131 racer of 1933 (430 kph) and by the Heinkel He 70 at the Paris Air Show of December 1934.

    The wingspan was 8.38 m for an area of 10 m², giving a wing loading of 130 kg/m²

    Split flap were used for the shortening of the landing run.

    But, the ailerons were also used as combat flap, allowing very tight maneuvers.

    The fuselage, well streamlined, was 7.20 m long, 1.31 m shorter than the CR 714 !
    Its cross section was 1.43 * 0.81 (= 1.16 m²).

    The unique air-intake, under the air-screw, gathered the air for the cooling of the engine as, also, the air needed for the supercharger: This design was optimized to minimize the effects of the boundary layer. 

    The fuel tank had a capacity of 185 liters. 


    Interestingly, the little size of this fighter allowed the use of Bowden cable for the triggering of the 3 guns, eliminating one of the worst shortcoming of the Morane and Bloch fighters which needed pneumatic devices inducing an unacceptable delay of 0.5 second (!) before the effective firing of the machine-guns.




    Very promising - but shortened - flight trials


    The Mureaux 190 was ready to fly at the end of May 1936 (Les Ailes, 14 May 1936).

    Unfortunately, owing to the gigantic strikes of the Leftist unions (CGT) and political parties, the first straight ground running occurred only at the mid of July 1936, 2 months later!

    The pilot Desjobert achieved the maiden flight of the fighter between at the mid-August 1936.

    One month later, the fighter had a new pilot, Mr. Guignard.

    The review Les Ailes of the October, 8th, reported the trials being running well and insisted: "The speed is very impressive". Such a comment was written also for the Morane-Saulnier 405, but only once, in September 1936, and never after!

    Fifteen days later, the same review published 4 pictures of this fighter in his front page.

    The November 26, the same review published a complete paper to the Mureaux 190.

    The author, André Frachet, underlined her "outstanding maneuverability and the tightness of her turns".

    He wrote also how such a tiny aircraft was difficult to be visually detected, this implying few hazard against the gunners of the attacked bombers. 

    So, the Mureaux 190 may be considered as the first stealth fighter!

    Indeed, for the actual witness, this fighter was impressive because of her flying agility as, also, her excellent performances.

    Frachet concluded: "This aircraft, easy to manufacture, easy to fly, with her good adaptability and her relatively cheap price, is the forerunner of a winning formula".




    The performances


    Unfortunately, the trials were stopped by the nationalizations induced by the Front Populaire, at the beginning of January 1937.

    At this time, the Mureaux 190 had flown only 4 months, so the engine was far from it's best capabilities.
    • The top speed at sea level was 430 kph, 100 kph faster than the Dewoitine 510, 60 km/h faster than the Morane 406 and 20 kph faster than the Hurricane K 5054 (This speed was the only one the journalists were able to evaluate themselves). 
    • The top speed at 5,000 m was 500 kph (Les Ailes) or 480 kph (l'Aéronautique), these speeds being of the same order of magnitude than the speed of the Nieuport 161.
    • The landing speed was 99 kph.
    • The service ceiling was 10,000 m. 
    I did not found climbing data for this fighter. They were, likely, good, taking into account the power loading of the Mureaux - 2.80 kg/hp - better than the one of the Morane 406 (2.95 kg/hp). 

    The flying endurance was 2 hours and 30 minutes, at 350 kph, that one may translate as 925 km. 

    The combat radius was 300 km, twice the one of the Messerschmitt Bf 109 E!

    As were her performances, the Mureaux 190 fighter was already considerably more performing than the Morane 406, chosen as the standard French fighter by the CEMA.



    Blockade !


    Stopping the trials was the only response of the French Air Ministry to protect the pathetic MS 406! 

    The idea under the nationalizations, for some politicians, was to gather most of the aeronautic companies in three or four state-controlled structures. They expected more simple ways to lead this industry in what they thought as the Good Direction(!).

    For the CGT worker union, that was seen also as a step to the workers power, similar as they believe about the Soviet Union.

    In most of the case, initially, the leading of the new aeronautic groups was given to a Armament Engineer (a French specific category of administrative "specialist"). 

    At this very moment, the research departments have been completely forgotten... 

    In less than 6 months, the French aeronautic production had dropped at its lowest level in the history!


    This time, the French politicians discovered that aeronautic mass production was not an ordinary job like selling saucepans!

    The leaders of the research teams needed a lot of experiences! So, the government introduced the former technical directors at their ancient place. 

    One complete year had been wasted and nobody dared to eliminate the Morane-Saulnier 406...

    The very promising Mureaux 190 was forgotten, as was also the Nieuport 161.



    A tentative tactical view


    The Mureaux 190 was clearly faster than most of the French fighters, but the Nieuport 161. 

    So, she would had no problem to catch any of the enemy bombers.


    She would deceive the gunners of the German bombers because they will overestimate the distances between them. So, they would be waiting to much before the opening of the fire, allowing to the pilot of the Mureaux 190 to shoot them first.


    She was faster than all the B, C, D variants of the Messerschmitt Bf 109 as she was faster than the Italian fighters at the only possible exception of the Macchi MC 200.

    Because of her low wing loading, her weak inertia and her combat flaps, she was exceptionally maneuverable.

    She would be an unpleasant surprise for both the German fighters, playing with them a game very similar to the one of the Zero fighter against the Allied fighters.

    Ok, the Mureaux 190 was a very small and very difficult to hit target

    Nevertheless, no fighter is perfect: If she was hit by a 20 mm shell, the damages should have a much more dramatic effect as in the case of a Nieuport 161 or a Bloch 152.


    Unexpected new developments

    The November, 3, 1938, Les Ailes published what looked as the "obituary" of the exceptional fighter of André Brunet with the title: "The King of the fighters rot at Villacoublay :

    (…) We remember the ANF-Les Mureaux 190 designed by Brunet, fighter which, fitted with an air-cooled Salmson engine of only 450 hp, was able to exceed 500 kph with the normal armament of standard fighters.
    (...)

    Today, this beautiful aircraft, which was able to fly faster than 600 kph if she was fitted with the little 12 X Hispano engine and which would be the ing of fighters, is now rotting at Villacoublay."


    After reading this, one will, logically, expect the Mureaux 190 history is finished.

    Fortunately, it was not the case, at all.


    An amazing "dynasty"

    {Source : Les Avions Potez Jean-Louis Coroller and Michel Ledet, Lela Presse}

    The boss of the Société de Construction Aéronautique du Nord (the former company Potez-CAMS), Mr. Henri Potez, was very wise when he pick up the chief engineer André Brunet with most of his team of Les Mureaux company. 
    As a first consequence, a new lightweight fighter, stemming from the Mureaux 190, was developed, fitting the liquid cooled Hispano-Suiza 12 X of 690 Hp at 3,900 m. This engine was said as unbreakable!
    The new fighter, designated as Potez 230, used the same armament than the Dewoitine 520.

    She took off the Mars 30, 1940.

    Heavier than the Mureaux 190 (1 800 kg at take off), she benefited from an exceptional general streamlining, as, also, a good skin polishing.


    The fuselage length was 7.46 m.

    The wingspan waso 8.71 m, the wing area being 11 m².

    The wing loading 164 kg/m² and the weight over power ratio being 2.61 kg/hp.




    Potez 230 - The canon is fitted and the Ratier air-screw was an automatic one 



    The top speed were:
    • 440 kph at sea level,
    • 560 kph at 5,000 m (CEMA, May 8, 1940).
    I did not found data about the climbing speed, but, the power loading better than the one of the D 520 and the excellent fineness suggest they were excellent.


    For common war flights, the Potez 230 used 3 protected tanks totaling 275 liters of fuel. For long transferring flights, a supplementary 80 liters tank was used but its fuel was to be consumed first.


    The patrolling time at 95% of the maximum power was 90 minutes (1 hour and 30 minutes).

    At this cruising speed (550 kph), the total range was 825 km, considerably better than the one of the Bf 109 E, which was unable to exceed 5 minutes of horizontal flight above 535 kph.

    Obviously, during an escort flight at 75% of the maximum power, the autonomy was far more than 1,000 km and the combat radius exceeded easily 300 km.

    The measured performances, as was the Potez 230, were excellent - better than those of all the other fighters built in France or in the USA - and it would be very useful to ordered it in mass production. 


    But, as usual in France, someone preferred the more powerful HS 12 Y 31 engine, which would allow a top speed of ~600 kph, and even, the 12 Y 51 which would allow ~630 kph.

    In such a case, the Potez 230 could easily fought against the Bf 109 F 2!

    However, the German onslaught was running. 

    Nobody thought to flew this precious prototype to safety. So, she fell in the hands of German who were very grateful to obtain the complete data of the first integral wing torsion box to fly!

    If ordered in time, as she was in the CEMA, this fighter could be a very difficult opponent for the Bf 109 E.




    A numerous family




    Similarly, most of the Potez projects were modified by the blending with the Brunet elliptic wings:
    • The twin-engined fighters 670 and 671,

    • The fast bombers of the 70x series, 

    • The new Potez 170, a twin-floats fighter which resemble the Potez 230 with a much larger wingspan,
    • The Potez 220, a twin engined recco aircraft unfortunately fitted with a ventral gondola spoiling her fineness.


    However, the most impressive Potez / Brunet project was undoubtedly the Potez C1 - 40 S, which looked as a larger and much more tapered Potez 230.

    She will use the new Hispano-Suiza 12 Z delivering 1,300 hp, with two turbo-superchargers.

    The air-screw will be four-bladed.

    The fuselage length was 9.71 m. The weight was 1,800 kg empty and 3,200 kg for take off.

    The wingspan was 11.92 m and the wing area was 19 m².

    The wing loading was 168 kg/m² and the power loading was 2.46 kg/hp.

    The expected speed were:
    • 540 kph at sea level,
    • 610 kph at 5,000 m,
    • 675 kph at 9,000 m.
    The time needed for 10,000 m was 14 minutes and the service ceiling exceeded 12,000 m.

    The total range was 1,800 km...

    This project achieved the stage of the wooden fitting mock up, suggesting the Potez C1-40 S to be flown clearly before the end of 1940. 

    Unfortunately, the events of June 1940 forbade to go further.

    A comparison with the fighters expected for the beginning of 1942 displays this fighter would be faster than the Arsenal VG 39 (625 / 630 kph), faster than the Bf 109 F 4 (630 kph) and even faster than the Focke-Wulf 190 A.

    Her wing loading will allow her a superior maneuverability and her total range was a valuable strategic asset.










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