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 4000 m,
- a climbing time of at most 15 minutes to reach 8000 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 4500 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 4000 m was published as 6 min (and 15'46" to reach 8000 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 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 = 9000 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 4400 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.
So, it was (as today also) suggested, 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 4200 m - 1000 m higher than the 860 Hp 12Y31 engine used for all the MS 406.
If the alleged top speed with the 12Y31 were 485 kph ar 4500 m, one could normally expect a top speed of 525 kph at 5500 m (~20 kph for the 1000 m gain + 20 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.
The absolute need for a 30 kph edge in speed !
If You think these 30 kph were not very significant, please, follow-me, we'l go to attack some enemy bombers.. ;-).
To catch 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), so the interception was unlikely, so 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 1 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, it was written the Morane 406 was climbing to 7000 m in 18 minutes. The best (true) record of the MS 406 for 4000 m was 6'40" (400", giving an average speed of 10 m/s or ~2000 ft/min).
So, You can see the time from 4000 m to 7000 m was 11' 20", or 680 seconds. So the average speed for these last 3000 m was 4.4 m/s, or 265 m/min.
This was, obviously, considerably better than the average speed necessary to climb from 7000 m to 8000 m. You can, at best, expect from 200 to 150 m/min.
So the Morane 406 in the very best case, climbed these last 1000 m in 5 min (total from sea level to 8000 m: 23 minutes) and more probably only in 24'40".
It was hopeless.
The Morane 410 case
This wise decision could have been decided earlier, in November 1939, even more in November 1937, knowing the overwhelming results of the Zurich meeting.
They decided to increase the fire power by 2 belt-fed machine-guns, such a decision imposing to fit new wings (!).
Only a 15 kph speed increase for 240 hp more power (28 %), you must be joking!
If you compute a downgrade of a Mörkö with a 12Y31 the speed decrease to 465 kph.
Ok, the oil cooler seemed not well placed.
But this fighter had still her exhaust pipes, very better than those of the MS 410, and allowing her at least a boost of 20 kph!
Since 45 years, I had not seen other values than the obviously wrong "official" ones.
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 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?