Sunday, April 7, 2019

The Avia B 534, a very strategical biplane fighter (Revised the 07 / 11 / 2020)


In 1938, for France, the common sens would have been to go to war with Hitler's Germany, even without any approbation of our British Allies. 

The rationale is as follow. 

Theoretically, France had, actually, two allies on the East part of Europe: Poland and Czechoslovakia. 
If the first one was much more populated, the second one had numerous military assets!

But the Poland dictatorship suffered of huge tactical weaknesses:
  • Its territories were open to most of its potential enemies (USSR and German Third Reich):
  • A completely obsolete military policy:
    • no sufficiently numerous and efficient armored vehicles,
    • no efficient and sufficiently numerous fighter planes, 
    • too few bombers, 
    • an amazingly scarce artillery endowment  for their numerous Infantry divisions (1/5 of the German ones!),
  • A foreign policy deliberately hostile to its most powerful neighbor, the USSR, and, simultaneously, no real allies.


Physical map of the today Poland: The Westward  shift of Poland by the Potsdam agreement, logically, annihilated the East Prussia. But the mountains stay only in the South, protecting Poland only against Czechoslovakia!


Military speaking, Czechoslovakia was in a considerably better shape than Poland, with a real Air Force, good tanks and armored vehicles.

So, we may focus our attention on an amazing Czechoslovakian fighter, the Avia B 534, which was really superior to the more recent British Gloster Gladiator

The huge moral weakness and the short sighted policy of many French (and British) politicians forbade us to see how this fighter was a game changer, if used at the right time.



A really useful biplane fighter


This little fighter have been designed by the Czech engineer František Novotný.

She was of classical structure, built with welded high tensile steel tubes with fabric covering, as was also the British Hurricane fighter.

She was 8.10 m long and weighted 1,440 kg empty and 1,980 kg for take off.

The wingspan was 9.40 m and the total wing area was 23.56 m². So, the wing loading was 84 kg/m², allowing an excellent maneuverability.


The engine was a Hispano-Suiza 12 Ydrs licence produced by Avia and delivering 850 Cv at 3,200 m.




-Avia B 534 of the 3rd series -  The air intake was designed to overcome the boundary layer problems, but the radiator seemed not to take into account the Meredith effect, unfortunately.



The first flight of this fighter was successfully made the
 25 of May, 1933. 

Immediately, the engineers understood this aircraft had even better potentialities and the following prototypes were significantly perfected and series production was ordered in 1934.  

The fuselage was well streamlined, allowing a top speed of 395 kph (in the literature, you may found from 37 kph to 410 kph following the variants). 

With backward exhaust pipes, this fighter would have been able to fly at list 15 kph faster! 

The maximal cruise speed was 345 kph. The total range was given from 500 to 580 km following the sources (The two fuel tanks totaled 347 liters).

An other source have given an economic cruising speed of 300 kph.

The B 534 was typically a target defense interceptor as were also the Messerschmitt 109 and the Spitfire.

The main asset of this fighter was an amazingly good climb speed:
  • The service ceiling was 10,600 m (to be compared to the 8,000 m of the Polish PZL 11C).
  • The time for 5,000 m was 5' 30" (some sources wrote 4' 28"), i.e. from 1 to 2 minutes faster than the Messerschmitt 109 E of May 1940!
The armament gathered four 7.92 mm machine guns and was very similar than the one used in the Gloster Gladiator, but with a 80 m/s faster muzzle velocity.

{The B  634 was the last and the best streamlined variant of the Avia biplane fighter. 

But, at the time this prototype was flying, Avia unveiled the B 35, a monoplane fighter which used a fixed landing gear. 

This new fighter demonstrated excellent flying qualities and her top speed exceeded those of the B 534  by 100 kph. 

Unfortunately, during a fly past at low altitude and at very high speed, the test pilot, not accustomed to such a speed; tried a too tight maneuver, triggering the fatal crash of his aircraft.


Facing the Avia B 534, Germany may used initially of early Messerschmitt 109 C or D whose engines delivered about 700 hp, weighted 350 kg more for take off and were using of a similar armament.

Monoplane and fitted with a retractable landing gear, these Bf 109 variants were able to fly only 50 to 60 kph faster than the B 534.
However, their climbing time was, by far, not so good, their operational ceiling was 2,000 m lower, these two flaws allowing the Czechoslovakian pilots to catch them by surprise. 
As they were also very far to demonstrate a maneuverability similar to the one of the B 534

Moreover, in July 1938, 50% of the Bf 109 were unable to fly: In other words, entering simultaneously in war with France and Czechoslovakia in the Fall of 1938, the Hitlers's Germany had no "roof" to protect the German peoples from any aerial strikes.

The Czech pilots who fought brilliantly in France from 1939 to June 1940 demonstrated theirs excellent qualities of fighters pilots, of their excellent marksmanship and of their good tactical sense.

In the case of aerial battle, the Messerschmitt fighters facing the B 534 would have been in a very similar situation than the US P 40 fighters against the Japanese A6M2 Zéro fighters in 1942.

The only advantage of the German fighter pilots was their excellent Freya radars, once they were operating! 

Nevertheless, in his war memory, Adolph Galland reported, in the beginning of the Phoney War (in the Fall  of 1939), a scramble of all the wing after an alert, this resulting of the downing of a Bf 108 Taifun in which was a high ranking Luftwaffe officer! 




The Czecoslovakia war (starting point for a possible What if...)

Caution : Any "What if" is a pure fiction. 
This may be used as a demonstration that, at a precise moment in the History, other choices would have created a completely different fate for a lot of peoples in numerous countries.

I'm ignoring the degree of efficiency the Sudetenland peoples might exerted in sabotaging the capacity of the Czechoslovakian Army: That is the main objection to my "What if...".


The possibilities of the Avia fighter as I described previously regard only the 1938-1940 period and facing the Luftwaffe.

The real question is: Was France really at risk against an overwhelming Wehrmacht at the end of 1938, when French Premier Daladier was still wanting to save Czechoslovakia?



Some real facts 


In 1938, Czechoslovakia was the most powerful and the most reliable Ally for France since 1918 (remember, since the 20's, United Kingdom favored the German rearming and, simultaneously, was repeatedly objecting against our own rearmament).

From a tactical point of view, Czechoslovakia was in no way a flat country.

The Czech part is almost entirely surrounded by mountains and the Slovakian territories consist mainly in mountainous regions, excepted in the plain where flows the Danube, which is also a mighty natural break.



Mountainous terrain of Czechoslovakia in 1969 (very similar to the one of 1938) -


Moreover, the numerous forests reduced the capacity to detect troop displacements on the ground.

So, the penetration of an enemy army in such a country was not a walk in the park (I personally knew, in 1965, a Hungarian scientist who had fought successfully against the Wehrmacht together with the Slovakian Resistance in Slovakia)! 

For the Wehrmacht, it might appeared rather similar to the penetration in a very large Ardennes massif (alone, the today Czech Republic has more than twice the total area of Belgium). 

Nothing to see with Poland (in August 1965, I was driving car in these two country: The Czech roads constituted a much better training area than the Polish ones!) 


From the other hand, the Czechoslovakian fortifications were not so easy to break through

General Guderian (in Heinz Guderian, Erinnerungen eines Soldaten) wrote, after WWII, these fortifications were not so impressive than it was commonly said. 
Nevertheless, he wrote also the Wehrmacht would have experienced too much unnecessary human casualties.
It was especially true because the Czechoslovakian Army had already mobilized 33 divisions in 1938
That is very differed greatly from the Polish army which, in Septembre 1939, began only to mobilize troops after the entry of the German troops in Poland.

The Czechoslovakian armored units totaled about 350 Skoda LT vz. 35 tanks, fairly armored, fast, well armed and easy to handle. They appeared as equivalent to the Pz III.




Škoda LT vz 35 : Agile, reliable, fitted with a 37 mm cannon (V0 of 675 m/s), these tank was able to destroy easily almost all German tank Pz I, Pz II and Pz III. Its only dreadful opponent was the Pz IV (which was far from operational status).


Czechoslovakia was about to use of a even better tank, the LT vz. 38.

Today (and repeatedly), several authors wrote an inappropriate argument: They argue that 350 tanks of the armored Czechoslovakian Army could be overwhelmed by the 1,900 German tanks available in 1938. 
These so-called tanks gathered only Pz I and Pz II which were, in fact, only light armored vehicles devoid of efficient armor (the thickness exceeding rarely 16 mm in 1938). 

So, each Czechoslovakian tank would had no difficulty to destroy them in great number.

(Remember, on year later the Polish soldiers destroyed a lot of them with their Boys anti-tank riffles.)

The Panzers III were at an experimental status (and were vulnerable to the Czech 37 mm cannon) and the Pz IV was in an even less advanced status



A German author, Mr Milan Hauner, highlights very thoroughly all the difficulties occurring for Czechoslovakia facing the Wehrmacht in September 1938. 

He appears to neglect the Czechoslovakian Air Force, on the pretext that this force consisted mainly of biplane fighters Avia B 534 and that it gathered only 200 bombers.

But that was not true in the Summer of 1938 : The Czechoslovakian "fighter command" was a very rude adversary for the actual Luftwaffe.


The meteorological factor was also completely absent from Mr. Hauner's conceptions. 
In Fall, France is subject to succession of meteorological depressions which carry a lot of nimbostratus (storm clouds) displacing following mainly a West - East direction
This might have very strong repercussions on the managing of any aerial warfare: The French airmen would had the knowledge of the future weather that the German ones could not have.

In Czechoslovakia, e.g. at Prague, the first days of October may be rainy, later, the weather became a little more sunny, with frequent morning fogs (which favored ambushes). 

During the following weeks, the temperatures decrease strongly. 

Winter begins really in November with numerous snow falls.

Likely, the Germans should attempted to intimidate the populations, using the bombing of the largest city of the country, as they do in May 1940 at Rotterdam

Today, we know the Wehrmacht of 1938 was not "winter proof"!

Anyway, Germans must have sufficient forces to confront with France, this implying to conserve a lot of bombers and fighters. 

Germany was absolutely not immune from Czechoslovakian raids! 


Inside the Luftwaffe, the Dornier 17 D / F bombers were almost all involved in the Spain Civil War where their performances were seen, in 1938, as no more efficient.

In Germany, some 500 examples belonged to the Dornier 17 M / P variants, and the B variant was just about to be delivered.


The much more powerful Heinkel 111 C might be specialized for the long and fast offensive raids. 
They would likely be used for French objectives (insofar the French military deciders demonstrated a strong reaction).


In 1938, the twin-engined Junkers 86 was the most frequent German bomber with 600 examples. 

These aircrafts were 18 m long and had a take off weight of about 8,000 kg.

The wingspan was 22.50 m and the wing area totaled 82 m², allowing the very low wing loading of 100 kg/m². 





Junnckers 86  A or D - 


The two diesel engines Junkers Jumo 205 C-4 of this bomber delivered 600 hp, allowing a normal bomb load of 800 kg.

Her top speed was 325 kph at 3,000 m.

The service ceiling of the Ju 86 was 5,900 m : So, the normal flight level had few chance to exceed 4,000 m. 

In top speed, the Junkers was similar to that of her French counterpart Bloch 210 but her bomb load was 50 % of that of the Bloch and her ceiling was 60% less high... 

This bomber had no chance against the Avia B 534.

{Parenthesis: In Wikipedia, you may found essentially informations on the  stratospheric variant Ju 86 P which did not exist at all in 1938. 
This high altitude recco-bomber was first seen over Great Britain, during the final part of BoB, demonstrating an operational ceiling of 12,000 m without opponent before 1942 until the Spitfire Mk VII entered operational service.
If this bomber variant was technically interesting, its strategical interest was rather weak.}


OK, in 1938, Germany had about 1,300 to 1,500 bombers, but the Jagdwaffe had only 600 Bf 109 with a doubtful reliability (50% were not available in July 1938).

As wrote Adolphe Galland after WW II, politicians and generals always imagine the Mastering of the Air may be obtain only by bombing

Nevertheless, once their bombers will be flying towards the enemy territoriesthey became the preys of the enemy fighters, but when they benefited from a strong protection

At the end of October 1940, Hitler was forced to fall back on the less effective night bombing to stop the loss of bombers and of their valuable crews, decimated by the strong aerial battles occurring from the May 10, 1940 to the Fall of that year (Battle of Britain).


In the case of an aerial offensive against Czechoslovakia, and taking into account a strong reaction of France, Germany would have no real allies :
  • Poland would stay neutral, with a focus against its Ost boundary with USSR.
  • Italia would be also neutral, but with a temptation to enter in Albania.
  • The Great-Britain would have been divided between pro-Hitler and anti-Hitler. It would be not easy for Mr Chamberlain to condemn France and Czechoslovakia without tarnishing his international image . 
The Czechoslovakian fighter pilots might used of classical interception schemes

The climbing to 5,000 m with the B 534 consumed about 5', so the German bombers were attacked 10 to 15 minutes after the take off of the B 534

We know also the German bombers of 1938 suffered a strong adverse influence of the bomb load on their top speed : A fully loaded He 111 was unable to exceed 300 kph...) .

The attacks of the Czechoslovakian fighters on the German bombers could result in a better score than the one obtained by French and Allied fighters achieved the May 10, 1940.  

Such good result of the better climb speed of the B 534, on the clearly slower German bombers as, also, in the division of the existing bombers in two fleets: One for the French front and one for the Czech front. 

One may also take into account the Jagdwaffe was, in 1938, about one third of the power facing the Allies in 1940. It would also have been necessarily divided in two.

The 20 to 80 Potez 630 and 631 long range fighters, already in service in the French Armée de l'Air, being as fast as was the Bf 109 D, they were not easy prey for them, so, some of them they might play an in-flight early warning role

If the French fighting planes have consisted in Nieuport 161, the mastery of the Air would have been instantly achieved.

Nevertheless, in the historical case the Curtiss H 75, D 510, D 501 et Spad 510 would have been also extremely dangerous for the Luftwaffe.

In the case of an Allied attack, the Bf 109 C / D needed 8 minutes to reach the same altitude (10 minutes for 6.000 m). 
They had an as short range than the Bf 109 E of the Battle of Britain because their fuel tank were of smaller dimension (337 liters)...


 The Czechoslovakian bombers 


Some sources attribute 200 bombers to the Czechoslovakian Air force.
For the End of the 1938 Summer, it had :
  • 54 Bloch 200 bombers, seen as rather efficient for night bombing. They had, in the Czechoslovakian production only, a more important bomb load of 1,400 kg (instead of 1,200 kg in the French production) and 5 machine guns (instead of 3 in the original product) for its defense . 


    Document of  the author - a French MB 200


    • About 60 Tupolev SB for daylight bombing, able to deliver a bomb load of 600 kg , 


    Tupelev SB - from 425 to 450 kph.

    • At least, 400 Letov S 328 biplanes able to recce and bombing missions (with a  bomb load of 500 kg). The exceptional  maneuverability of these Letov 328 would favor their use for harassing the enemy columns, as the Germans will do with their rather similar Henshel 123.


    Letov 328 - 


    Quid of the USSR? 


    The Soviet Union wanted a free passing through Poland territories in order to go to Czechoslovakia. 

    If France had a real high level foreign minister, instead of the poor Mr. Georges Bonnet, it would be possible to answer two point to the Stalin's demand:
    • France will be an active player in this crisis. So, all European countries would clearly understand who will be their real allies against Hitler.
    • Nobody was able to prevented URSS land troops in Eastern Prussia.
    Such an intervention, taking into account the strong Prussian predominance in the high ranking officers of the Wehrmacht, Hitler should necessarily divert a lot of military means to salvaged the birthplace of the Teutonic Knights...


    At this moment, USSR disposed of a non negligible fleet of submarines, cruisers and destroyers (and even of rather powerful battleships) which might represented a thread for the Kriegsmarine in Baltic.

    From the other hand, the Red Army had several thousand of T26 and BT tanks, which appeared very powerful in 1938. 

    They were very fast (Christie suspension) and they had a 45 mm cannon efficient at more than 1 km.




    Soviét tank BT 5 - The triumph of the Christie suspension: 72 kph on the wheels, 52 kph on caterpillars)


    The Soviet Aviation was very numerous with some thousand of fast fighters as the Polikarpov I 16 and of SB bombers faster than the German bombers and hard for the German fighters.





    Tupolev TB 3  - A very heavy bomber loaded with two  fighter-bombaers I 16 (with two 250 kg bombs each) displaying her capability to carry a load of 5 tons (in 1941) !



    USSR might use also of 800 bombers Tupolev TB 3 able to carry easily 5 tons of bombs, or dozens of paratroopers. 

    This bomber was 25 m long.

    Her wingspan was 40 m and the wing area exceeded 230 m².

    She had a weight of 12,600 kg empty and from 19,000 to 24,000 kg for take off (following the variants).

    She had a top speed of 288 kph at 4,000 m (source : Wikipedia in deutscher Sprache of the March 9, 2019).

    There were no difficulty for 350 TB 3 to carry 8,000 of para troopers over Eastern Prussia after an intense night bombing!




    The French Armée de l'Air 


    For the 1938, the bomber units of France used of:
    •  190 Bloch 200 (for night bombing), 
    • 140 Amiot 143, 
    • 150 Potez 540, 
    • 240 Bloch 210, 
    •   60 Bloch 131,
    •   30 Farman 222-2.

    France had about 800 bombers.

    Knowing that fourteen Amiot 143 have been send at daylight, the 14 of May, 1940, over the Sedan town occupied by the Guderian's Panzer divisions, while flying at only 750 m AGL.

    Knowing that except the two bombers downed, and one landed in the fields inside the French lines, the others bombers, severely damaged, returned to their airfield (but were not repaired). So, the real score was 3 absolute losses and ten damaged bombers...

    OK, they have been escorted by 12 MS 406 (!).

    Are you thinking seriously these bombers would have suffered more losses against the 1938 Jagdwaffe than 2 years later, facing better armed and 100 kph faster fighters?

    Ok, the survival of French bomber crews would have been very better if the Bréguet 462 have been ordered at the end of 1936 and the Amiot 340 during the Summer of 1937.



    Epilogue and provisional conclusion


    Early in 19398, the Czechoslovakian government proposed to sell to France, for a very low price, 200 Avia B 534 (source: L'Aviation de Chasse Française, 1918-1940, Cuny & Danel, Docavia #2, p. 144). The proposal was exceptionally interesting.


    Unfortunately, the French deciders refused, because they were not aware of the great chance that was for our armies: Such excellent fighters were available for numerous very useful first line purposes.
    The Morane 406 were very few (25 copies delivered for the end of 1938) and also completely outclassed by the Spad 510, which was slower than the Avia fighter.

    After the availability of new and better fighters, the Avia B 534 could have been used in a secondary defense line, 150 to 200 km inside the French boundaries.



    Even bigger mistakes have been done by Mr Daladier during the Sudeten crisis
    They were announced by the inappropriate Vuillemin's visit in Germany.

    This honest man was not able to decipher properly the brain of the completely dishonest Marshall Goering! 

    Instead, our general might have visited Prague and Bratislava.
    • The first mistake was to refuse the tripartite discussion with USSR and Czechoslovakia. Some tactical agreements were easy to finalize. The literature said sixty soviet divisions were ready to help the Czechoslovakian army...
    • The second mistake was to follow the English politician Neville Chamberlain in his completely unrealistic proposals!  The French Premier had only to refuse any discussion on Czechoslovakia in the absence of this country and of the USSR.
    • The last mistake was to wait before the order of mobilization of the French Army. Hitler's generals were not happy to resume the World War. Some seemed ready to eliminate their Fuehrer. Our capitulation was seen by these persons as a demonstration that Hitler was right!...

    I want, at last, to highlight the extraordinary short geopolitical sighting of Colonel Beck, the 1938 minister of Poland. 

    Mr Beck, instead of backing the Czechoslovakianbacked the German point of view in order to obtain the Teschen town as a tips

    Obviously, the Wehrmacht attacked the Poland, with the help of USSR.

    Without any immediately active Allies, Poland was defeated in three weeks... 



    Wednesday, November 14, 2018

    The mysterious Loire 250 fighter (revised the September 15, 2019 *)








    The Loire 250 was the second fighter of the 1934 contest to fly in 1935. Today, she remains unknown by most people.

    She has done a real perfecting of her flying qualities, and, despite some remnant aerodynamic oddities, she demonstrated really good performances.

    Amazingly, she was "forgotten" by the CEMA under the pretext of the nationalizations affecting quite all the French aeronautic industry.



    A rather light fighter 


    Long of 7.81 m (0.32 m  shorter than the Morane-Saulnier 406), this little fighter weighted 1,700 kg empty and 2,150 à 2,191 kg at take-off with armament (source: L'Aéronautique, November 1936).

    The wingspan was 10.80 m and the total wing area was 16.40 m². A front view of the fighter displayed a dihedral layout which already looked like those of the tiny Jodel D9 French sport plane (1948) and,15 years later, the heavy US Navy fighter-bomber McD-D F4 Phantom II

    Smooth connecting surfaces were fitted to the leading edge of the wings.


    The wing loading was 131 kg/m², announcing a good maneuverability.





    Personal document of the author -  Front view of the Loire 250 -


    The Loire 250 look rather different than most of the bulky contemporary fighters engined by radial air-cooled power plants (e.g. the Polikarpov I 16, the Seversky P 35). 

    She belonged to a new and rather slim generation which culminated with the FW 190, the Nakajima Ki 84 Hayate and the Hawker Fury of 1945.

    This French fighter used a Hispano-Suiza 14 Ha engine delivering 980 hp.


    Initially, the 2 blades fixed pitch wooden air-screw was 2.75 m in diameter.

    The fuel tank contained only 330 liters (as discussed below).



    The French aeronautical weekly Les Ailes of September 19, 1935 announced the next factory outing of the new Loire fighter: "At LOIRE-NIEUPORT. One proceeds to the last assemblies  of the new single seat fighter Loire. 
    This aircraft is an all-metal low-wing monoplane, fitted with a radial air-cooled Hispano engine, of 1,000 hp. 

    The monocoque fuselage is of a great fineness and the streamlining of this fighter is very nice. 
    The first flight is expected to be done with Sadi-Lecointe at the controls."




    Personal document of the author - From L'Aéronautique, 1936 -
    The glassed canopy was a bit too long but announced the one of the Mitsubishi A6 M2


    The maiden flight occurred the September 27, 1935, and was reported as follow by les Ailes of the October 03, 1935"At LOIRE-NIEUPORT.— The new fighter had done her first flights. 
    At first, Sadi-Lecointe flew short strait lines, then he have flown long enough. A little after, Nadot had also flown her. 


    The impression after these first tests is excellent.
    Other flight tests will follow actively under the direction of engineer Asselot, designer of the Loire aircrafts."

    This good general impression, while her contender Morane 405 was flying since more than a full month, indicated the Loire was seen too as a good contender for the contest.


    The October 10, 1935, the same weekly confirmed the pilots Sadi-Lecointe and Nadot continued to fly with "Some modifications of the aircraft controls have been made on the Loire 250."


    The following week, "the Loire fighter - Hispano 14-Ha engine - have done short perfecting flight tests."




    The initial look of the Loire 250 fighter likely before the first flight:
    The air-screw is a wooden 2 blades fixed pitch one and the landing gear is a fixed one.

    The October 24, alone Pierre Nadot tested the fighter.


    The November 21, 1935, Les Ailes told us about the Loire fighter: "This fighter fly almost daily with Nadot at the controls."

    For the first time after 2 months of flight testing, it appears that something leaves to be desired:  May be the Hispano-Suiza 14-Ha engine was not perfectly reliable or not sufficiently powerful.



    Nevertheless, the November 28, 1935, Les Ailes came back on the subject: "The Loire fighter, type 250, Hispano 14-Ha engined, is continuing successfully her perfecting flight tests; This new kind of engine appears to give any satisfaction to the pilots."


    The December 12, 1935, "Surtel and Nadot flew the Loire 250. The fighter will be modified, the engine is disassembled."

    From December 20, 1935 to January 5, 1936, despite a very bad weather, Les Ailes of the January 9, 1936, wrote about a lot of work about the two prototypes of fighters manufactured by Loire-Nieuport. "Nadot had flown numerous tests with the fighter Loire 250."

    The January 10, 1936, despite “a forceful storm” (which involved the territories of Great Britain, France, Belgium and Germany, killing 16 British people and 2 German ones), the Loire 250 displayed a full demonstration of all the aerobatic maneuvers, like do also her 2 contenders, the Morane 405 and the Nieuport 161. 


    Amazingly, the February 2th, 1936, Les Ailes published a complete article on the Loire 250. 
    Some of the published data were inaccurate, as the empty weight (1,500 kg) and the weight at take-off (2,000 kg).

    The dimensions were good but the performances were theoretical:
    • The top speed was 485 kph;
    • The climbing time to 5,000 m will be inferior to 5 minutes.
    One may read another climb time later, likely related to an increase of the take-off weight.


    The weekly Les Ailes told us about the Loire fighter the March 12, 1936. 
    After a brief stay in factory, the test flights were resumed: "The Loire 250 his now fitted with her definitive Hispano 14-Ha engine, which had no reduction gear box. The pilot Nadot flew several flights with this fighter."




    The Avril 2, 1936, the reporter of Les Ailes wrote: "Always numerous flight tests with the two recent fighters, Loire 250 and Nieuport 161, respectively by Nadot and by Lefèvre.

    The perfecting of these two aircrafts is rather complete, both will soon enter the CEMA.
    They will be formidable contenders for the Morane 405."

    Such a commentary demonstrated the Morane 405 appeared no more as the favorite of the French fighter contest for competent and independent spotters.

    Two weeks later, Les Ailes insisted again about numerous perfecting flights done by Nadot with the Loire 250.


    The following week, we learned the Loire 250 was testing a variable pitch air-screw.




    During May 1936, the reporters became silent about the fighter prototypes, one of the sad consequences of the huge Front Populaire strikes.


    The June 18, 1936, Les Ailes told us : "Numerous tests flights of Lefèvre [...] with the new Loire 250 fighter which have got a variable pitch Hamilton air-screw.

    The July 30, we can read: "The Loire 250, with a Hispano 14-Ha engine, received modifications for some of her fairings.



    The August 6, Les Ailes wrote: "Lefèbvre carried out tests with the new Loire fighter, Hispano 14-Ha engine fitted with the new variable pitch air-screw; The enter to CEMA would be occur soon." 

    The September 3th, 1936, les Ailes reported the Loire 250 continued to fly, but Surtel succeeded to Lefèbvre at her controls (Lefèbvre was more associated to the Nieuport 161 fighter).



    Original document of the author, from L’Aéronautique 1936 - The Loire 250 in her last configuration. The cockpit canopy was too long, the engine cowling was too large, the streamlining of the engine cowling was inexistant and the exhaust pipes were not well designed: That "costed" circa 50 kph!


    The November 5th, the fighter was at the ultimate finishing stage in the factory.

    At the Paris Air Show, in November 1936, the Loire fighter was exposed on her stand.


    The British weekly Flight of the November 19, 1936, dedicated to the Paris Air Show, reportedafter some laudatory words about the tiny Mureaux 190 fighter:
    "Two larger, heavier and higher powered machines in the 300 mph category are the Loire-Nieuport 250 and the Morane-Saulnier 405.
    (…)
    The Loire is fitted with one of the new Hispano-Suiza 14 Ha two-row fourteen-cylinders radial of 980 hp and is a low-wing cantilever monoplane with a wing of peculiar formation.

    The center section is proportionately wider than usual and is given no dihedral, this being reserved for the outer panels.

    The undercarriage retracts in an inward sense into the wing which carries trailing-edge flaps designed to keep the landing speed down to 62 mph in spite of the wing loading of over 30 lb/sq.ft. [sic!].

    The fuselage behind the big Hispano radial is of circular section as far back as the pilot's cockpit thence developing an oval section.
    The cockpit enclosure is of more than usual interest because its tail fairing is quite transparent to improve the field of view.

    Full night-flying gear is specified, together with two-way wireless, two canons mounted in the wings and two machine guns.

    A three-bladed Hispano-Suiza air-screw is fitted, being a Hamilton type built under license in France. 
    In round figures the maximum speed is given as 300 mph and the time of climb to 13,120 ft as five minutes. 



    Original document of the author - The Loire 250 at the Paris Air Show, hiding the already obsolete Loire 46 fighter, which just entered service


    The November 22, 1937, Les Ailes commented as follow the présentation of this aircraft: 
    "The look of the Loire 250 fighter is striking for any spotter. 
    She is one typical example of the aerodynamic improvements obtained through the research on the interactions between the diverse parts of the aircraft.

    The connecting surfaces between these parts were thoroughly designed and, if the one between the trailing edge of the wings and the fuselage (= Karman) meets our requirements, we were particularly interested by the sophisticated “fore Karman”, connecting the NACA engine cowling to the wings to make the landing speed slower.

    This new feature has been proved experimentally in the wind-tunnel at slow speed, and, after, by about twenty hours of flight testing.

    The Loire-Nieuport 250 is a single-seat fighter which fulfill the 1934 program of the French “Armée de l'Air”. 


    Having an integral metal structure and taking advantage of the cantilever low-wing layout, she had balanced control surfaces thoroughly designed to avoid all kinds of hazards associated to great speed.

    Following the altitudes, this fighter top speeds are:
                       395 kph [at sea level], 
                       480 kph (at 4,500 m) and 
                       450 kph at the service ceiling of 10,000 m.”



    The last mention of the Loire 250 fighter by Les Ailes was published May 6, 1937:

    "The LOIRE-250 was to begin her official trials when her manufacturer was nationalized.


    This prototype, using a Hispano-Suiza 14-Ha engine delivering 980 hp, was exhibited at the last Paris Air Show.
    She is flying since eighteen months and her perfecting is fully completed.
    She is now in a hangar of the Villacoublay airbase, ready to demonstrate the controlled flight performances in order to obtain useful data on the value of the Loire 250, as want the designers of this fighter.


    The Loire-250 was designed for the French program of the single-seat fighters of 1934 and, soon, we will got the prototypes for the program of 1936. 


    Fitted with very similar engines, but beneficiaries of new aerodynamic assets, one expect they will easily exceed the wall of 500 kph."


    What a beautiful example of diplomatic synthesis!


    The French Aeronautic Press in 1937 experienced a very different life than the previous year: Her liberty was no more sacred facing the CGT unionists and the political orders. 

    Pierre Cot and his favorites were deciding everything. A frontal opposition would be very dangerous, as quite always in the 1937 Europe. 


    Highlighting the Loire 250 was really perfected, the columnist informed us this fighter was actually perfectly stable
    Telling us the Loire designers were asking controlled performances, he inform us that this fighter outperformed the Morane 405 (as also the MS 406, this last designation being applied for an identical aircraft using an identical engine).


    The Loire 250 outperformed the Bloch 150 too, which has just first flown in May 1937 with very poor performances.
    None of the MB 150, 151 and 152 reached really better performances than the Loire fighter before 1940. The Bloch 15x were perfected only at the final part of the MB 152 series, and with the MB 155.


    The performances


    They were published by L'Aéronautique, for the Paris Air show of November 1936:
    • 395 kph at sea level,
    • 435 kph at 2,500 m, altitude reached in 3 minutes
    • 480 kph at 4,500 m,      "          "             5' 30"
    • 470 kph at 6,000 m,      "          "             7' 40"
    • 450 kph at 8,000 m,      "          "           12 minutes
    The landing speed was 100 km/h.

    These values appeared very close to those of her Nieuport 161 stablemate.

    The same data were given by other sources but L'Aéronautique was alone to suggest they resulted from a mathematical correction taking into account the expected power of the 14 Ha engine (which was not given but may be ranging from 1050 to 1120 hp).
    Simple reverse calculations allows us to obtain measured top speed of the Loire 250: From c460 kph to c475 kph at 4,500 m. 

    Such top speeds appear, today, as rather slow. But one may remind:
    • The Brewster Buffalo XF2 A-1 did not exceed 447 kph during the Navy early trials in 1938 (a complete work was done to obtain good performances).
    • The Grumman XF4F-2 was limited to 468 kph at the same time. 
    • With regard to the Bloch MB 150 M, she was then flying at only 434 kph, like the Morane 405 of 1936 (in Louis Bonte, Histoire des Essais en Vol, Docavia # 3). The Bloch was intensively perfected, not the Morane before the very late (5 years) MS 410, in April 1940...
    This suggestion of a recalculation seems not clear at all. 

    As she was, the Loire 250 fighter was not a dirty plane, aerodynamically speaking
    • Her wings displayed not the excess of relative thickness seen in the Hawker Henley (or in the Hurricane Mk I). 
    • The fuselage appeared rather streamlined so a top speed of 485 kph at 4,500 m was likely.

    Nevertheless, if we remember the political situation of the 1936 France, one understand it was difficult for the Air Minister Pierre Cot to order the Morane-Saulnier 405 / 406 - with, actually, a real top speed of 435 kph - when a radial engined fighter was able to fly at 485 kph.

    Moreover, these performances were obtained by the Loire 250 in an aerodynamic configuration still suffering from a non-optimal aerodynamic configuration:

    • The NACA cowling was very basic, worse than the one of Bloch MB 151 (of 1939) and MB 152 using the huge one meter in diameter cooling air intake.
    • The exhaust pipes were not facing backward.
    • And many other parasitic drag generators.
    These shortcomings reduced the top speed from at least 40 to 50 kph.

    {Parenthesis: The Hispano-Suiza 14 Ha or AA was the origin of some controversies:

     I – This engine appeared in Les Ailes of January 18, 1934, as a 900 hp engine in the first perfecting stage. 
    Hispano-Suiza wanted a new and more powerful engine partly using the technology of the Wright radial air-cooled 9 cylinders.

    The first tests were reported by Les Ailes of the February 1st, 1934: The 14 Ha engine delivered 960 hp at 1750 rpm. It was said also to be 1.20 m in diameter. 


    II – As far as I know, the first flight test of the 14 Ha was in September 1935, with the Loire 250. 
    Initially, it used only of 100 octane fuel, identical to the one used by the Air-France company. 
    As no comment was done, it appears logically this engine experienced no insurmountable problem. 

    The performances being promising, not surprisingly, the Loire fighter had flown dozens of flight hours from 1935 to 1936.




    III – The story of this engine became completely different in 1937 with Jacques Lecarme, an engineer- test pilot, and his friend Louis Bonte, when a lot of problems occurred with the bomber Lioré-Olivier 45.


    The first flights of the LéO 45 have been found excellent, with the same Hispano-Suiza 14 Ha engines, especially the flying qualities were seen as flawless

    For these test flights, this bomber was devoid of any fairing for the legs of the landing gear.

    Unfortunately, later, right after the assembly of the landing gear fairings, the LéO 45 became vicious during the take-off: The new fairing were masking the two rudders during the first part of the run. 
    But this important issue was aggravated by the very forward position where the landing gear was positioned: The bomber got out of hand... 

    This problem could have been fixed by replacing the classical landing gear by a tricycle one...  
    Thereby, the flight testing must take more time to fix this purely aerodynamic but unexpected issue.


    It never rains but it pours, during a calibration test at low altitude – the engines running full out while they were using the 87 grade of octane – the crankshafts of the two engines broken simultaneously at Saclay (10 km of Paris).

    Fortunately for the crews, as also for the bomber, due to the flat landscape of the Saclay plateau, the external temperature rather cold and the exceptional skill of the test pilot (Doumerc), no other issue occurred.
    The HS 14 Ha have not supported to run so fast for a so long duration with a so "bad" fuel.


    Quite identical mishaps were experienced by Rolls-Royce at the very beginning of the Merlin engine (which was fixed by a lot of work) and, after, by the Peregrine engine which was discontinued, downing the excellent Whirlwind twin-engined fighter.

    If Lecarme (in Louis Bonte, Histoire des essais en volDocavia #3) acknowledged that, “somehow miraculously”, no issue was following after fitting generous oil radiators, he attributed only to the Hispano engine the excessive delay of perfecting the LéO 45.

    So, the French Air Ministry directed Lioré & Olivieto stop any further aerodynamic investigation on the take-off stability and to proceed directly to the mass production of the LéO 451 using only Gnome & Rhône 14 N engines.
    That order had lethal consequences…





    IV – From the other hand, the Koolhoven FK 58 fighter prototypeusing the radial air-cooled Hispano 14 Ha - renamed 14 AA - took off for her maiden flight mi-Juillet 1938, and was able to exceed 500 kph.


    This engine was a new variant, more powerful (1080 hp) with an important increase of the cooling surfaces and using Sarrazin dampers.

    The French government ordered several dozens of FK 58 fighters but imposed the GR 14 N engines. These new FK 58 was 30 kph slower than the prototype and have got no victory... 





    V - The Latécoère company designed the Laté 570a B4 bomber, which was conceived to use of the new Gnome & Rhône 18 L delivering 1350 hp.


    The first flight of this excellent bomber was delayed for almost 2 years by the enticement of workers by CGT unionists who wanted to punish Mr. Latécoère to have not accepted the nationalization of his plant!

    Only the Hispano-Suiza 14 AA engines, with their actual bad reputation, were available.
    Amazingly, these rejected engines ran very well.

    The Laté 570 was exceptionally easy to fly, able of very tight maneuvers, achieving 470 kph à 5,000 m. This powerful bomber was able to deliver 2,000 kg of bombes, a bomb load 700 kg heavier than the one of the LéO 451.}




      

    The Loire 250: A bad fighter?


    Absolutely not.

    Amazingly, the Loire 250 was never accepted by the CEMA which preferred, later, the Bloch 150 M (alias MB 151) or le Curtiss H 75, which had lower performances until 1939.


    The Loire air-screw was 2.75 m in diameter. In 1939, the Bloch 152 used an air-screw of 2.90 m in diameter. 


    That was the consequence of the bad idea of using an engine devoid of reduction gear box (such a conception forbade any full out dive...). 

    Also, a too little air-screw reduce the speed capabilities of an aircraft…

    In the literature, we have read the deciders of the Loire-Nieuport company preferred clearly the Nieuport 161 fighter to the Loire 250 one.

    But, the Nieuport was involved in a lethal crash (she was not responsible at all, as I explained) and the Loire not experienced problem: One would have expected a more open mind of the test pilots and deciders.

    The Loire 250 have flown without accident for 18 month, so she may not be seen as dangerous.

    Assuming the minimal hypothesis for her performances, anyway, the Loire fighter of 1936 was 30 kph faster than the Bloch 150 M of 1937.

    Moreover, the relatively low wing loading of the Loire 250 (131 kg/m²) provided her a clearly better maneuverability than those of the Bloch 152 (156 kg/m²).



    The Loire 250 for the French Navy carriers? Yes, a wasted chance…



    In 1936, the French Aéronavale used, on the Béarn aircraft carrier only some Wibault 74 fighter (top speed 230 kph). 

    All other major navies used fighters that can fly at least 100 kph faster (like the Royal Navy, with its Gladiator ;-), or worst, when using the Skua or... the Roc!).

    In place of choosing the best adaptable fighters among the French more recent prototypes, the French Navy ordered a fighter belonging to the previous generation.

    That was the Dewoitine 376 (in fact, it was a product of Lioré & Olivier deciders in order to squeeze the Emile Dewoitine leadership). This already obsolete fighter was said to fly over 405 kph but she never reached the 380 kph of the terrestrial D 371 prototype (source: Les avions Dewoitine, Cuny & Danel, Docavia). 

    OK, these fighters were maneuverable and climbed well but the association of a bad air-screw with a not well balanced crankshaft induced numerous (and tremendous) vibrations which themselves induced frequent engine failures and, even, structural destructions...

    Simultaneously, a new contest was launched by the French Navy, in 1938, to obtain a fighter for the 2 new aircrafts carriers Joffre and Painlevé. The favorite contender, the Dewoitine 790, issued from the D 520 with a larger wing, was initially scheduled to fly only in the spring of 1941!

    A real naval tactician should have chosen, as soon as possible, in 1936, the most appropriate fighter among the existing prototypes of the 1934 French fighter contest.

    The Loire 250 was already particularly suitable to be used on board of the Béarn aircraft carrier:
    • She was already able to land at 100 kph (62 mph).
    • She occupied, on the ground and without folding the wings, the relatively little surface of 84 m², about 80 % of the surface occupied by most of her potential opponent or contenders, allowing a significant fighter covering of the French fleet.
    • She had better performances than most of her potential opponents.
    • With such a fighter, the Béarn would became a dreadful capital ship, the Loire 250  being able to carry bombs for dive bombing.
    • The armament would be constituted by:
      • Either 2 HS 404 guns of 20 mm and two 7.5 mm Darne belt-fed machine guns with 600 cartridges each;
      • Or four 7.5 mm Darne belt-fed machine guns with 600 cartridges each.

    One may argue the fuel tank was very insufficient for a naval aircraft. 
     

    The real fuel consumption, for one hour full out with the 1080 hp variant, was 359 liters, exceeding the fuel tank capacity by 30 liters, theoretically allowing just 55’ of flight.


    So, a completely different possibility deserve to be analyzed: Using a significantly lighter and thinner engine even it delivered significantly less power.

    This lighter fighter variant would have been interesting, using one of the two tiny 700 hp radial air-cooled engines designed by Gnome & Rhône (14 Mars) or by Hispano-Suiza (14 AB).

    The first light engine to be ready was the Hispano 14 AB which weighted 490 kg instead of 647 kg for the HS 14 Ha and its diameter was only 1.01 m.

    With this engine at maximum power, the 14 AB powered "light" Loire 250 fighter would have flown during 1 hour and 33 minutes.


    The second engine was the Gnome & Rhône 14 Mars weighted 410 kg and had diameter of only 0.95 m. 

    At maximum power, the 14 Mars powered "light" Loire 250 would be able to fly 1 hour and 42 minutes.

    OK, the loss of power would induce mechanically the loss of 40 to 70 kph (from 415 to 440 kph following the chosen engine).

    However, one may rectify these results because these calculations don’t take into account some other data, among them the reduced diameter of these engines, which allows a gain of about 40% of the engine cowling section.

    In such a case, one may expect a gain of about 20 kph (from 435 to 460 kph). Such fighters would have been at least as efficient than the Fokker D XXI of the Netherlands Air Force.

    Supplementary aerodynamic works should give supplementary gains totaling about 30 kph, (allowing a top speed ranging from 465 kph to 490 kph).

    Two years later, the conversion to the 100 octane fuel will increase the power to 800 hp, allowing a new 20 kph step, (allowing a top speed ranging from 485 kph to 510 kph).