lundi 20 février 2012

Nieuport 161: The favored contender (revised 10 / 19 / 2015)

The best French fighter in 1936


Knowing how the Morane 406 was completely outclassed by its German opponent Messerschmitt Bf 109 E during the Campaign of France in 1940, an obvious question arose justifiably: Was another choice than the Morane 406 fighter possible in the 1936 France? The answer is: Yes, obviously! 

During the summer of 1936, the Nieuport 161 was leading  the  fighter contest defined by the program of 1934, because she was the best performer among all of the numerous French prototypes.



Nieuport 161 - prototype 02 - the hole in the middle of the air-screw spinner is the proof of the presence of the 20 mm gun HS 9 


Mysterious top speeds,  performances


The only published performances are those of the prototype #02. 

Those of the 01, which flew very earlier, from September 1935 until September 22, 1936, have never been published, this being clearly disturbing for me. 

These two prototypes were fitted with the same kind of engine, an Hispano-Suiza 12 Ycrs providing 860 Cv at 3250 m. 

Her speeds at different altitudes were:
  • 400 kph, at sea level, 
  • 416 kph at    1,000 m,
  • 435 kph at    2,000 m,
  • 456 kph at    3,000 m,
  • 478 kph at   4,000 m (the highest published speed, but see below),
  • 474 kph at   5,000 m,
  • 470 kph at   6,000 m,
  • 458 kph at   7,000 m,
  • 443 kph at   8 000 m,
  • 426 kph at   9,000 m,
  • 400 kph at 10,000 m,
  • 360 kph at 11,000 m. 
All these data were published in the paper of A. Prudhomme in Air Magazine #25, April 2005. 

Nevertheless, the highest speed you read above cannot be the true top speed. 

Why?

Because the engine providing its maximum output at 3,150 m, the top speed must be reached ~1,300 m higher, at about 4,500 m, owing to the dynamic pressure created by the speed of the aircraft, and, also, the much lower temperature of the air, which allowed a better filling of the cylinders

Knowing that, at such altitude, any 100 m gain of altitude give ~2 kph increase of speed until the dynamic rated altitude. 
So, the top speed of the Nieuport 161 might be more than 490 kph between 4,500 and 4,700 m (488 kph for 4,500 m, 490 kph for 4,600 m, 492 kph for 4,700 m, and so on).

Such a speed, obtained without rearward exhaust pipes, was exactly of the same order of magnitude than the top speed of the Hurricane prototype K 5083, which used an engine delivering 1,030 hp. 
If one had fitted exhaust pipes on the Nieuport, you must have an extra speed of 15 kph...

In the Arnaud Prudhomme's paper, in the table summarizing the numerical data of this fighter, he wrote also a maximum speed of 496 kph (very close to my preceding estimation), without any explanation about the altitude or the identification of the prototype. It seems to be a "surviving" measure obtained by the Ni 161-01 prototype.

You may think the air intakes of the compressor suffered from some misconception, inducing a weaker engine power outputthen you must explain why the best instantaneous climbing speed (13.6 m/s) measured by the test pilot was found just at the same 4000 m level...  

{The Hurricane K 5083 obtained her top speed of 315 mph at 16,500 ft and her top instantaneous climb speed at only 6,500 ft (the engine was a Merlin C of 1,029 hp at 11,000 ft:
 http://www.wwiiaircraftperformance.org/hurricane/k5083.html).}



The economical cruising speed of the Nieuport 161 was 350 kph, ~30 kph faster than the Morane 406. 

The maximum cruising speed was 426 kph, given by a Russian site
This speed is consistent with a top speed of 495 kph at altitude. 

Such values demonstrated that how easily the Nieuport 161 could fulfill the escort duties of both the recce Potez 63 or the bomber LéO 451, both being too fast for the Morane "fighters".

From the other hand, the climbing speed was impressive: 
  • 1,000 m in  1' 16",
  • 2,000 m in  2' 30"           (the last 1,000 m in 1' 14"),
  • 3,000 m in  3' 44"          (the last 1,000 m in 1' 14") 
  • 4,000 m en  4' 58"         (the last 1,000 m in 1' 14") 
  • 5,000 m en  6' 17"         (the last 1,000 m in 1' 19") 
  • 6,000 m in   7' 50",        (the last 1,000 m in 1' 32")  
  • 7,000 m in  9' 41"         (the last 1,000 m in 1' 52")
  • 8,000 m in 12' 03"       (the last 1,000 m in 2' 22")  (A time 3 minutes faster than the time specified for the French contest, a climbing ability clearly better than the Bf 109 E of 1940!)
  •   9,000 m in 15' 19"       (the last 1,000 m in 3' 16")
  • 10,000 m in 20' 30". 
  • 11,000 m, her service ceiling, were reached in 34' 50". 
Her absolute was 11,250 m, 

As a matter of comparison, the time needed for the Spitfire Mk I K 9793, fitted with a similar kind of air-screw, was 29 minutes to reach 32,000 ft (~9,730 m). 

This fighter exceeded, by far, the performances of all the other contenders for the French contest. 


An bizarre weight problem


The first published data (in the 60's) were an empty weight of 1,748 kg and a take off weight of 2,278 kg, allowing a wing loading of 151.8 kg/m² and a power loading of 2.65 kg/m².

In the Arnaud Prudhomme work, you can reed some amazing data regarding both empty and take off weight. He gives us an empty weight of 1,915 kg.

The discrepancy between his data and the numerous older ones are amazing.

From the other hand, a direct derivative of the Nieuport 161 was ordered as a fighter bomber by the French Navy in 1938: The Loire-Nieuport 401.

The main change was a completely new wing of 24.75 m² in W (a 2/3 increase of wing area), an arrest hook, a weaker engine, a bomb launch device, a much more robust undercarriage, a folding device for the wings. 

All this help me to evaluate the weight increase to at least 400 kg.

So, I prefer to conserve the first published data. 



The fighter absolutely needed by the Armée de l'Air



All these performances were very promising, taking into account the early level of development of the Nieuport 161. 

In gun trials, it was told she was an excellent gun plate form.

No surprisingly, a 30 fighters order was about to be sent in mid-September 1936.

Sixty years later, William Green  wrote: "the LN 161 showed considerable promise and was the favored contender for the Armée de l'Air order..."


Unfortunately for the French Armée de l'Air and her pilots, the Nieuport 161 was written off in a crash - caused by irrelevant instructions - occurring during firing trial in dive at low altitude, lethal for the engineer test pilot. 

I will come back to this crash, for which the official explanations are absolutely unlikely, in this post, because its consequences were absolutely dramatic for French Army at the beginning of the WWII

In this other post, I'm explaining the numerous assets of the Nieuport 161 fighter over the Morane 406.

In this last post, I'll show first the dishonest engine policy of the CEMA as also the different policies for the taking into account of the crash of the 2 main contenders, leading to chose the Morane 406, a slow fighter having very poor speed and climbing performances.


My blog in French is entitled "L'Aviation selon Drix"

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