jeudi 13 juillet 2017

The Spad 510 fighter? Really excellent! (revised 02 / 22 / 2018)

{The SPAD logo was the label of the French company "Société de Production des Avions Déperdussin" created by Armand Déperdussin. 

Following the financial collapse of his creator, the SPAD company became the property of Louis Blériot, who conserved the great engineer Louis Béchereau, inventor of the monocoque structure 

The SPAD logo had obviously a new meaning : Société Pour l'Aviation et ses Dérivés.}

Summary of the History of the previous Spad fighters

The Spad VII and XIII, designed by Louis Béchereau, were of real strategical importance during the last years of WWI, as were also the lighter Nieuport fighters (from the NiD XI to the NiD XXVIII).

In 1920, the Spad 20 was very better than her predecessor the Spad XIII; her top speed was 225 kph (+ 10 kph), with a better agility.

The Spad 20 bis was a very militant contender for the race to the World Air Speed Record (culminating at 309 kph).

Between 1920 to 1931, engineer André Herbemont developed rather quickly the design of a family of biplane fighters :

  • Spad 81 (1923) with a 300 hp V8 Hispano-Suiza engine, flew at 235 kph. 80 samples were  ordered for the French Air Force (wing loading: 42 kg/m²), 
  • Spad 61 (1924), used a W 12 Lorraine engine and had a top speed of 280 kph; 350 examples were ordered for both Polish and Rumanian Air Forces (wing loading: 56 kg/m²),
  • Spad 51 (1925) radial Gnome & Rhône engine, 245 kph, 50 ordered for Poland (wing loading: 56 kg/m²).
  • Spad 91 was 9 fold modified from 1928 to 1932 (!):
    • With her engine devoid of supercharger, she attained 294 kph and climbed to 4,000 m in 9'.
    • With a supercharger added to her engine, her top speed was 350 kph (she won the 500 km world speed record with 309 kph). Her climbing time for 6,000 m was 8' 30".
    • The wing loading varied, following the types, from 66 to 82 kg/m². 
           {Unfortunately, the clearly inferior Morane 225 was ordered instead: 

    • Her top speed was 330 km/h, she climbed to 6,000 m in 12' 50" (loosing 4' 20" to the Spad 91 !), 
    • Her wing loading was 91 kg/m².}

    Author personal document - Spad 91-7 : Good speed, good visibility and good maneuverability.

    The Spad 510, the last French biplane fighter

    {My sources were the comprehensive study on this brilliant fighter that Michel Ledet and Pierre Cortet published in Avion # 126 (September 2003) and also actual articles in l'Aérophile of 1938.}

    Engineer André Herbemont started the design of the Spad 510 in 1930, but several financial constraints occurring in the Blériot company slowed his work.

    So the new fighter made her first flight only the January 6, 1933, with the excellent pilot Louis Massotte. The Dewoitine D 500, her main contender, had flown 6 months earlier.

    The Spad was 7.46 m long, weighting 1,245 kg empty and 1,650 kg for take off (l'Aérophile, January 1938) .

    Her structure was metallic but for the covering of the wings which were fabric covered, the fabric being coated with an Emaillite varnish.

    Author personal document -  Spad 510 - A well streamlined biplane fighter.

    Her wings had a span of 8.84 m et and the wing area was 22 m².

    So, the wing loading did not exceed '
    75 kg/m² (Aérophile, 1938).

    After good initial trials, she went to CEMA official trials. 

    The performances appeared moderate, especially because a max speed at 3,500 m was notified to exceed 350 kph.
    •          0 m --> 308 kph    engine running at   2,340 t / m
    •   3,500 m --> 346 kph                                   2,595 t / m
    •   4,000 m --> 351 kph                                   2,620 t / m
      •   8,000 m --> 321 kph                                    2,465 t / m

      For only 4 kph, the Spad would be excluded from the contest!

      Worst, the adj. Goussin report (dated from the mid-June 1934), claimed that this fighter "went into a flat spin when the elevator is used toward a nose up attitude. It seems the commands are not sufficiently efficient to stop this flat spin, etc...".  

      Remember that, actually, the flat spin was the terror of all pilots

      As Cuny and Danel (Docavia #2) demonstrated, it was very amazing that such a "terrific aircraft" never had a fatal accident!

      Fortunately for the French Armée de l'Air, the Air Minister, general Victor Denain, was really a competent pilot. 

      The March 12, 1935, after nine months of controversy, Louis Massotte displayed publicly six spins of 13 complete rotations each, demonstrating without doubt the 
      spins of the Spad 510 were easy to stop.

      A bit later, he demonstrated also his fighter was a very good contender:    
      •          0 m          310 kph
      •      500 m          317 kph
      •   1,000 m          324 kph
      •   1,500 m          331 kph
      •   2,000 m          338 kph
      •   2,500 m          348 kph
      •   3,000 m          354 kph
      •   3,500 m          362 kph
      •   4,000 m          370 kph
      •   4,500 m          372 kph
      •   5,000 m          371 kph
      •   5,500 m          369 kph
      •   6,000 m          366 kph
      •   6,500 m          361 kph
      •   7,000 m          355 kph
      •   7,500 m          348 kph
      •   8,000 m          339 kph
      •   8,500 m          329 kph
      •   9,000 m          327 kph
      •   9,500 m          304 kph
      • 10,000 m          286 kph
      The total range was 875 km.

      The diving speed was better than 600 kph, a very good performance (the Dewoitine 500 did not exceed 500 kph in dive; among the other contender, the Les Mureaux 170 was the only other fighter to exceed the 600 kph).

      The climbing times were also excellent.
      •   3,150 m          3' 33"                     average instant climb speed of 14.8 m/s from 0 m
      •   3,500 m          3' 55"                     instant climb speed of 15.9 m/s for the last 350 m
      •   4,000 m          4' 31"                     
      •   4,500 m          5' 15"                      1' 20"  for the last 1,000 m
      •   5,000 m          5' 57"            
      •   5,500 m          6' 45"                      1' 30" for the last 1,000 m
      •   6,000 m          7' 43"
      •   6,500 m          8' 49"                      2' 04"  for the last 1,000 m
      •   7,000 m          9' 57"
      •   7,500 m        11' 09"                      3' 10"  for the last 1,000 m
      •   8,000 m        12' 59"  
      •   8,500 m        14' 45"                       3' 36"  for the last 1,000 m
      •   9,000 m        17' 12"  
      •   9,500 m        20' 35"                       5' 50"  for the last 1,000 m
      • 10,000 m        25' 10"  

      The service ceiling was 10,100 m (you may found also 10,600 m).

      The armament gathered four 
      7.5 mm machine guns MAC 34

      These guns were drum feed, and the drums were so bulky than two of them must be housed inside the thickness of the inferior wings (the two others being embedded in the fuselage.

      If motorized with other engines, the top speed of the Spad 510 was boosted as highlighted by L'Aérophile:
      • Hispano-Suiza 12 Y crs     :   405 kph à 4,000 m (with a service ceiling of 11,000 m)
      • Lorraine Pétrel 12 Hdrs     :   378 kph       "
      • Gnome & Rhône 14 Ksd   :   385 kph        "
      The Mureaux 170 was the only faster French fighter of this program.

      Ordered, at last!

      The French Air ministry ordered 60 examples the August 30, 1935.

      The first Spad 510 produced by the ex-Blériot plant (in Suresnes, a Paris suburb) was delivered at the beginning of 1936, only six months later.

      (Remember, the first series Morane-Saulnier 405 - ordered in July 1936 - appeared only at the end of the 1938 Winter, more than 20 months later!).

      Author personal document -  Spad 510  About 30 Spad 510 fuselages in the Suresnes plant -
      The absence of workers suggest the photography was taken during the "Front Populaire" strikes of 1936.

      The strikes and all the ensuing troubles triggered by the "Front Populaire" in 1936 were responsible of a supplemental delay of at least six months.

      The last two fighters produced had one 20 mm HS 9 cannon installed on her engine instead of the 2 usual fuselage riffle caliber machine-guns.

      The last S 510 was delivered before the end of 1937.

      The firsts delivered Spad were attributed to squadrons belonging to the VIIème Escadre de Chasse (=7th Fighters Wing). 

      The pilots were very satisfied with such a performing and nimble fighter!

      At the beginning of 1938, the Spad 510 fighter were used by 20 different squadrons (gathered in 10 groups) to accustom the youngest pilots to modern fighters.

      Such a behavior of the FAF deciders suggest they believed the Spad 510 was clearly better than all the other fighters actually in French service.

      That was confirmed, after the Münich crisis, in November 1938, when the Spad 510 was used for mock combats against the Morane-Saulnier 406 fighter.

      These "combats" demonstrated the MS 406 was unable to withstand a Spad 510 attack, because :

      • Her maneuverability was not sufficient,
      • Her climbing speed was very poor,
      • Her top speed did not allow to escape the Spad!!!
      The discovery of the poor ability of the MS 406 for her real task of fighter was later confirmed in all combats during the Campaign of France. 

      {The Spad 510 was also opposed in similar virtual combats against the Curtiss H 75, but the gap of performances was too heavy for the biplane. Nevertheless, if the Curtiss pilot was insufficiently attentive, the Spad might win.}

      The War

      You might read in the literature the Spad 510 was never implied during the Phoney War or the following Campaign of France

      Nevertheless, one might highlight an oddity: The Groupe III/10, theoretically fully equipped with Bloch 151 (and, after, with MB 152) {Source : Le Bloch MB 152, by Serge Joanne, Histoire de l'Aviation # 13}, used also Spad 510 during most of the Campaign of France. 

      OK, at the beginning, the MB 151 were not really available. 

      The MB 152 sent later to replace the obsolete MB 151 were worn out...

      So, the Spad 510 flew operational CAP, in March, in Avril, and also - at least a handful of them - until the June 
      18, 1940.

      Obviously, the management of such a complicated structure was very difficult for the mechanics (who have to repair both Hispano 12 X - liquid cooled - and Gnome & Rhône 14 N - air cooled -).

      But, it's also the proof the Spad 510 fighter were able to fly in the so-called "German ruled" French sky in May-June 1940... 

      A forgotten asset

      As a biplane fighter, the Spad 510, seems as good as the Gloster Gladiator, for the article on her in the English written Wikipedia dated from the 19 Mai 2017).

      If the British Gladiator had nothing to do in the French sky in September 1939 - because she was completely obsolete as a fighter - she played an key task during the Campaign of Norway between March and June 1940. 

      So, the Spad 510 should have been a very relevant Navy fighter for the Béarn carrier for the same Campaign and she would be operationally efficient, at least until the end of 1940. 

      She would be very better than the poor Dewoitine 376, so impatient to get rid of free herself of her wings!


      Overview on her actual contenders

      French Fighter

      The Dewoitine 500 flew first at the June 18, 1932.  She was an all-metal stressed skin fighter with an open cockpit and a fixed undercarriage. 

      She was 7.74 m long.

      The engine was an Hispano-Suiza 12 X delivering 690 hp at 4,000 m.

      Her weight was 1,250 kg empty and 1,710 kg for take off.

      The wings had
       a span of 12.09 m and an area of 16.50 m²: The wing loading was 104 kg/m². 

      Such a great span induced an efficient ground effect which had an adverse effect for any attempt of very short landing.

      The D 500 was easy to fly, but the flight quality report (by Jacques Lecarme) - published by Cuny & Danel (Les Avions Dewoitine, Docavia #2) - displayed that a stall might induce a fall of altitude up to 1,500 m. 

      Such a loss of altitude was not a good news for the pilots...

      Author personal document -  The elegant Spad 500 fighter suffered aerodynamically from her "anti-Karman" wing junctions - 

      Emile Dewoitine expected a top speed of 400 kph at 5,000 m. Unfortunately, the designs of the wings and of the radiator were not optimal at all and did allowed such a performance.

      The effective top speed of the D 500 was 371 kph at 5,000 m, the diving speed being 500 kph.

      The climbing time were good :
        • 4,000 m in 5' 11", 
        • 6,000 m in 8' 20",
        • 8,000 m in 13' 26". 
      The service ceiling was 10,000 m
      The total range was 850 km at a cruising speed 226 km/h.

      The better fineness of the Spad 510 may be explained by:

      • Very thin wings, 
      • A well designed fuselage, 
      • A streamlined landing gear, 
      • A good NACA cowling allowing a good evacuation of the hot air toward both sides.

      Some oddity remained in the Dewoitine 500:
      • Both 2 blocks of six cylinders of the engine used separate fairings, 
      • Unfortunately, the rear part of the roots of the wings were largely indented, increasing dramatically the thickness of the airfoil at this key zone.
      • The radiator opened a very large and angular air intake just after the air screw, as if the main goal was to multiply the number of the whirlwinds... 

      British Fighters

      The Hawker Fury II (also actually dubbed Super-Fury) was 8.15 m long.

      Her wings had a span of 9.14 m with a total area of 23.2 m².

      She weighted 1,240 kg empty and 1,640 kg for take offThe wing loading of  70 kg/m² explained her excellent maneuverability.

      With her Rolls-Royce Kestrel engine delivering 640 hp, her top speed was 360 kph.

      The total range was only 490 km (about the half part of the Spad 510 range)!

      The origin of such a short range capability may be found in the choice of the lightest weight to obtain the fastest climbing speed.

      Nevertheless, the climbing time for 10,000 ft was 4 ' 30", the time for the Spad 510 to climb to 4,000 m (1,000 m higher)! 

      Unfortunately, that choice had, obviously, an adverse effect for the escort of bombers...

      The more recent Gloster Gladiator was 31% more powerful (with a Bristol Mercury IX engine delivering 840 hp).

      Larger than the Fury, she had a take off weight of 2,110 kg.

      The wing area was 30 m² and the wing loading was 70 kg/m² as those of the Fury II

      Her top speed was 
      396 km/h at an altitude of 3,770 m official data issued from Martlesham Heath in September 1937- (in Wikipedia, you may found claim for top speed of 407 or 414 kph...).

      The total range was 715 km at a cruising speed of 340 kph (?).

      This better range was an asset for both the RAF or the Royal Navy.

      The climbing times were: 

      • 1,500 m in   2' 35",
      • 3,000 m in   4' 35",  the last 1,500 m in 2' 00"
      • 4,500 m in   6' 48",  the last 1,500 m in 2' 13"
      • 6,000 m in 10' 00"   the last 1,500 m in 3' 12".
      These climbing times were only average but a bit better than those of a MS 406 fighter!  

      {The climbing times published by William Green - Fighter, Vol. 2, 1960 - are totally unsuitable.}

        US Navy Fighters

        {I do not have any fair data for the Boeing P 26 of the US Air Force, sorry.}

        biplane fighter Gruman F2F of the end of 1933 - as the Spad 510 - but used a retractable landing gear box

        She was 6.53 m long and weighted 1,220 kg empty and 1,745 kg at take off.

        The wings had a span of 8.69 m and an area of 21.40 m.

        Her wing loading was 82 kg/m².

        With the
         R-1535-72 Twin Wasp Junior engine delivering 700 hp, she had the same speed than the Spad 510, but her climb speed and her ceiling were not as good. 

        On the other hand, the total range of 1,580 km was excellent. 

        She entered service in January 1935, but she was retired at the end of 1939

        The following descendant, the Gruman F3F, was 7.06 m long

        Her weight was 1,490 kg empty and 2,175 kg for take off.

        The wing span was 9.75 m

        With a wing area of 24.15 m², the wing loading was 90 kg/m².

        The new Wright R-1820-22 "Cyclone" 9-cylinder radial engine delivered 950 hp. 

        Her first flight occurred the Mars 20, 1935. 

        The top speed was 425 kph, the economical cruise speed was 240 kph.

        The total range was 1,600 km.

        The service ceiling exceeded 10,000 m.

        After extremely fast air trials, the prototype broke in the air during a recovery at 14 g - after a dive - killing the test pilot. 

        Nevertheless, the promise of the F3F was such that she was ordered at ~140 examples and the first production fighters were in the Navy's "hands" in January 1936.

        Polish Fighter

        The PZL 11 was
         7.55 m long.

        She weighted 1,150 kg empty and 1,630 kg for take off.
        Her wingspan was 11 m and the wing area of 17.9 m² allowed her a wing loading of 91 kg/m². She had a good maneuverability. 

        The top speed of the PZL 11 fighter was 370 kph at altitude and her minimal speed was 110 kph.

        Her total range was 700 km.

        The climbing time for 5,000 m was good: 6 minutes.

        But the 7,000 m in 13' were not very good and explained a bad service ceiling of only 8,000 m.

        Her armament consisted only in two
         7.92 mm machine-guns. Moreover, this light weapons jammed frequently...

        Fighters of the USSR

        The biplane Polikarpov I 15, weighted only 1,374 kg for take off.

        The wings totaled an area of 21.9 m².

        So, the wing loading was only 63 kg/m², allowing her an outstanding maneuverability.

        The top speed of the I 15 fighter  was 370 kph with the 630 Cv engine (you may find also 350 to 376 kph). 

        The total range was only 530 km.

        But she can climb to 5,000 m in 6' 10" - a good time - and her service ceiling was 9,500 m.

        The monoplane fighter Polikarpov I 16 was likely influenced by the Gee Bee R 1 American racer.

        She had a wing area of 14.5 m².

        The take off weight was 1,500 kg and the wing loading was 104 kg/m².

        Her top speed was 450 kph at an altitude of 2,700 m d'altitude.

        The total range of 700 km was more comfortable than for the previous fighter. 

        The climbing time for 5,000 m was 7' 42" and the service ceiling was 9,100 m.

        Italian Fighter

        The Fiat CR 32 was a well streamlined biplane fighter. 

        She was 7,45 m long. Her wings had a span of 9.50 m and an area of 22.10 m².

        She weighted 1,325 kg empty and 1 865 kg for take off: The wing loading was 84 kg/m².

        Her FIAT A30 RA-bis V12 engine delivered 600 hp.

        The top speed was 370 kph at an altitude of 3,000 m d' (varying from 356 to 375 kph following the armament).

        The total range was 780 km.

        The climbing time for 6,000 m was 14' 25", resulting (likely) from the choice of a high compression ratio of 8 - and a 94 octane fuel - instead of a real super-charger.

        However, the tactical value of the Fiat CR 32 was perfectly combat proven during the Spanish Civil War: The Italian pilots of the Aviazione Legionaria had downed about 600 soviet I 15  and I 16 (in equal parts) and 60 Tupolev SB2 at the cost of 73 Fiat destroyed. 
        {The SB2 bombers were actually seen as not down-able, knowing their excellent speed (450 kph) besting any existing fighters.} 

        {The authors of the article on the Spad 510 (July 2017) in the Wikipedia in Italiano appear to be focused on the superiority of the French fighter over the Fiat CR 32 in speed - which he claimed as 380 kph - climbing and armament.}

        The CR 32 fought efficiently during the WW II in North Africa and Ethiopia.

        Japanese Fighter

        The Kawasaki Ki 10, biplane fighter of the Japanese Army entering service in 1935, was 7.55 m long. 

        Kawasaki Ki 10 - A well streamlined biplane fighter

        She weighted 1,360 kg empty and 1,740 kg for take off.

        Her wing span was 10.02 m and her wing area was 23 m². The wing loading was 75.7 kg/m².

        The engine was a water-cooled Kawasaki Ha9-IIa V 12 cylinders, with a displacement of 47 liters, and delivering 850 hp (without supercharger).

        The top speed was 400 kph at 3,000 m.

        The total range was 1,100 km.

        The ceiling of 11,300 m was excellent.

        The only flows of this fighter were the absence of supercharger and her armament of only 2 riffle caliber (7.7 mm) type 89 machine guns which had a rather slow velocity.


        In the 1930's, almost all countries favored the biplane fighters, at least up to 1937. 

         French technical deciders (STAé) wanted to be more advanced than their counterparts and chosen the Dewoitine 500 fighter, a good but perfectible fighter. 

        Unfortunately, this fighter lacked too much perfecting to be the real best fighter of the French contest.

        The CEMA staff did not acknowledged its defeat, preferring to use dishonest methods (false speed measurements and dishonest report).

        Again in 1974, MM. Bonte and Lecarme (Histoire des Essais en VolDocavia #3) wrote: "The manufacturer of the biplane Spad 510, eliminated as a result of her general lacklustre facing the far superior Dewoitine 500, succeeded in creating a competitive flight trial center whose leader, a war ace with a limited comprehension capacity, submitted a report favoring the Spad and vilifying the D 500...".

        Such a text is amazingly
         violent: It resulted from their actual impatient mood.

        In 1936, by similar methods, they imposed the poor and obsolete Morane-Saulnier 406 against the very much efficient - and modern - Nieuport 161.

        Ironically, in November 1938, just after the Munich crisis, the same Spad 510, seen as lacklustre against the D 500 by Bonte & Co., was the winner of the new simulated combats in which she was opposed against the - theoretically much more modern - Morane-Saulnier 406!

        The CEMA deciders were, apparently, not lucky at all in their choices... May be, somewhere, they were crossing the path of a Black Cat?

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