From advertisement to the reality
The French program for fighters published in July 1934 gave these specifications:
- a top speed of at least 450 kph (amazingly, two months later, the program for the bombers specified, at least 470 kph!),
- a climbing time of at most 6 minutes to reach 4,000 m,
- a climbing time of at most 15 minutes to reach 8,000 m,
- an armament comprising either one 20 mm cannon and two 7.5 mm machine guns or four 7.5 mm machine guns.
The standard fighter chosen by the French Air Force late in November 1936 was the Morane-Saulnier MS 405, later designated as MS 406 (after insignificant modifications).
She was an easy to fly, maneuverable and reliable plane.
Official papers and all published data (even today) have claimed honorable performances for that time, matching perfectly to the program specifications.
The top speed at sea level was 400 kph and 485 kph at 4,500 m (the published values were inflated by a derisory 1 kph: Respectively 401 kph and 486 kph - a 2013 French paper even inflated the top speed to 490 kph without any proof given!).
The climbing time to 4,000 m was published as 6 min (and 15'46" to reach 8,000 m).
For a today reader, it seemed not far from the average top speed displayed by the Hawker Hurricane Mk I as it was told by Air Chief-Marshal Dowding (305 mph or 490 kph, see Famous Fighters of WWII, vol. 1, W.Green, Macdonald, 1960).
|Morane-Saulnier MS 405 - one can see clearly the huge and not streamlined at all cooling device|
Nevertheless, the pilots who flown operationally - during WW II - the MS 406 were very disappointed since the beginning of the Phoney War.
- Their fighter was unable to intercept any high flying spy plane as the Dornier Do 215 B1 (speed = 470 kph, ceiling = 9,000 m...);
- They experienced many difficulties to catch any German bomber which flew at lower altitude because they flew faster than the Morane can do, even the Dornier Do17 (410 kph). The only bomber she can catch was the Junkers Ju 87 Stuka (390 kph at 4,400 m);
- They were completely outclassed by the Messerscmitt Bf 109 E fighters.
The reason of this disappointment was that the official performances resulted clearly from intentionally wrong data.
Because their planes were, at least, 2 years old, it was suggested (as today also), in France, that these degraded performances were not contradictory with the official French publications, owing to the engine and skinning aging.
Unfortunately, that was not true at all.
The Quest for the true top speed of the Morane 406!
Among the published data, some are usable because they were published after the choice of this fighter (They were used only for the engineers).
It was the typical case of the following data: The MS 405 #12 used a Hispano-Suiza 12Y45 engine of 920 Hp at 4,200 m - 1,000 m higher than the 860 Hp 12Y31 engine used for all the MS 406.
If the alleged top speed with the 12 Y 31 were 485 kph at 4500 m, one could normally expect a top speed of 516 kph at 5,500 m (~20 kph for the 1,000 m gain + 11 kph for the 60 hp gain).
Using that speed, one can reverse-compute a true top speed of 455 kph, 30 kph less than the claimed top speed.
You can read the actual performance data (from 1936 to 1938) of the MS 405 and Nieuport 161 prototypes. The so-called MS 406 had the same engine, the same shape. Explain-me how she can had a significantly better top speed than the MS 405...
The absolute need for a 30 kph edge in speed !
If these 30 kph were not very significant, please, follow-me, we'l go to attack some enemy bombers ;-).
To catch up a bomber, you need to fly faster than them, OK?
But what an edge of speed is needed?
In the France of May 1940, there was no real ground control (see my post on this subject): The interception being unlikely, you must chase the enemy bombers up to be sufficiently close to fire at them.
A group of 40 bombers was clearly visible at no more than 10 km (depending from the time, the whether, and so on).
If you flew only 10 kph faster, you needed one full hour to meet them (you can read the proof here!).
The last kilometer (as all the previous ones) would have taken 6 minutes and the last 400 m needed 2 minutes 24 seconds, allowing the enemy rear gunner to perform a perfect aiming at your own plane!
A good explanation for a lot of losses of French fighters and... pilots.
If the speed of the fighter exceeded that of the bomber from 60 kph, the fighter needed only 10 minutes to meet the bombers (1 km/min.), the rear gunner had a much less comfortable situation to open fire on you (the last 400 m needed 24 seconds).
The climbing speed was even worst.
The time needed to 8000 m exceeding the 1934 program specifications by 9 minutes
In the notice d'emploi du chasseur Curtiss H75 (=P 36), it is written the Morane 406 was climbing to 7,000 m in 18 minutes. The best (true) record of the MS 406 for 4,000 m was 6'40" (400", giving an average speed of 10 m/s or ~2000 ft/min).
So, one can see the time from 4,000 m to 7,000 m was 11' 20", or 680 seconds. So the average speed for these last 3,000 m was 4.4 m/s, or 265 m/min.
This was, obviously, considerably better than the average speed necessary to climb from 7,000 m to 8,000 m. You can, at best, expect from 200 to 150 m/min.
So the Morane 406 in the very best case, climbed these last 1,000 m in 5 min (total from sea level to 8,000 m: 23 minutes) and, more probably, in 24' 40".
It was hopeless.
The Morane 410 case: Three years too late
Unfortunately, this welcomed decision occurred too late, in February 1940 - during the Phoney War - (source: G. Botquin, Album du fanatique de l’Aviation n°109, 1978). It could have been decided earlier, in November 1939, even more in November 1937, knowing the overwhelming results of the Zurich meeting.
With all these modifications, it was possible to speed up the Morane fighter by about 50 kph, a substantial progress.
But, as usual, the commissions were watching.
They decided to increase the fire power by 2 belt-fed machine-guns, such a decision imposing to fit new wings (!).
If you compute a downgrade of a Mörkö with a 12Y31 the speed decrease to 465 kph.
May be, the oil cooler of this Finnish fighter could have been better situated.
But this fighter had still her exhaust pipes, very better than those of the MS 410, and allowing her at least a top speed boost of 20 kph!
The speed limits for rejecting the MS 406 before their acceptation by the French Air Force were never published (the top speed values published for the Dewoitine 520 - 535 kph - and for the Caudron CR 714 - 460 kph - were the rejecting values).
A lot of French pilots had lost their precious life because this plane was all, except a true fighter plane.
Today, the WWII is over, death penalty is over in France, Germans are our friends, the persons who chosen this poor fighter were all dead.
So, I have 2 questions:
(a rather good training plane, the MS 435 have been derived from this plane).
Why, today, the publications on this subject did not rectify this big mistake?