W.Green, G.Swanborough The Complete Book of Fighters

NIEUPORT Monoplane France
  
   In October 1917, Nieuport had a prototype fighter monoplane under construction with the aim of combining the structural simplicity and reduced drag of this configuration with a reasonable downward view for the pilot. The shoulder-mounted wing was braced by substantial lift struts attached to a rigid undercarriage structure incorporating a substantial spanwise surface of broad chord and streamline section. Glazed cut-outs in the wing roots gave the pilot some downward view and the wings and faired fuselage were fabric-covered. Powered by a 150 hp Gnome Monosoupape 9N rotary, the monoplane is presumed to have flown at the end of 1917 or beginning of 1918, at which time a second prototype with a 180 hp Le Rhone 9R was scheduled to fly about the end of January. The latter embodied some revision of the wings, which introduced inverse taper on the inboard trailing edges, and an extended fin. As of 1 May 1918, the Monosoupape-powered prototype was still under test, while the prototype with the Le Rhone had been abandoned. Armament comprised two synchronised 7,7-mm Vickers guns. Although the monoplane was not officially accepted, it represented the first Nieuport application of the configuration that was later to be greatly refined as the Nie 31. The following data is based on manufacturer’s estimates.

Max speed, 137 mph (220 km/h) at 13,125 ft (4 000 m).
Time to 13,125 ft (4 000 m), 13 min.
Endurance, 2.0 hrs.
Empty weight, 955 lb (433 kg).
Loaded weight, 1,565 lb (703 kg).
Wing area, 188.37 sq ft (17,50 m2).

C.Owers French Warplanes of WWI. Volume 1: Fighters (A Centennial Perspective on Great War Airplanes 43)

Nieuport Monoplane Fighters
  
  The Nieuport sesquiplanes scouts were initially very successful with their rotary engines. They were fast, manoeuvrable with good visibility for the pilot, however, they were limited in their development by an inherent weakness that was demonstrated by the Germans when they installed heavier, more powerful inline engines in their variations of the sesquiplanes layout - the Albatros D.III and D.V. It was to be mid-1917 before the first Nieuport biplane fighter flew. This was the Ni.28 that was to see front line use with the US Air Service squadrons on the Western Front.
  The Nieuport monoplane that emerge in September 1917, was built on the principles described in Nieuport patent No. 521,133. The proposal combined structural simplicity with low drag. Visually the fighter looked like a monoplane version of the Ni.28, however, the Ni.28 had a much slimmer fuselage. The shoulder-mounted broad chord wing was braced by a set of struts that were attached to the wide track axle housing of the undercarriage. This housing was in the form of an auxiliary wing. Two struts on each side were braced from the housing to about the middle of the underside of the wing. The lack of documentation and photographs makes the development history of the monoplane difficult. At this time there were several Nieuport C1 (fighter) aircraft in development with the Gnome 160-hp or Le Rhone 180-hp engine mentioned in official documents but are not detailed enough to be able to identify exactly which machine is being discussed. From photographs it appears that the first machine had plain wings without any cutouts at the fuselage to improve the pilots downward view. The cut-outs in the wings were modified a number of times. The final wartime version with the one-shot cannon had glazed cut-outs in the fuselage where the wing joined the fuselage to allow for the pilot to have a restricted downward view.
  According to some sources the first monoplane was powered by the 150-hp Gnome Monosoupape 9N rotary engine. Two synchronised 7.7 mm machine guns were mounted in front of the pilot. The aircraft is presumed to have flown in late 1917 or early 1918 as a second prototype that was powered by a 180-hp Le Rhone 9R was reported as being ready to fly at the end of January. This version had some revisions to the wing and a longer fin. One prototype was fitted with a buckshot cannon that fired through a hollow airscrew shaft. The French "ace" Georges Felix Madon recalled that
  "Twelve days later, the armistice was signed. I did not regret it, but nevertheless I felt some sadness. I had had certain Nieuport prepared with a cannon, according to the data of my friend Lieutenant Jensen, a Danish volunteer, and I think that with this weapon I could have done an impressive job."

  Maj J.P.C. Sewell, RFC/RAF liaison officer with the French, commented in April 1918, on the somewhat unattractive NIEUPORT monoplane with its glass observation panels has an undercarriage without any shock absorbers whatever. The tyres have double inner tubes.

  "Since LEGAGNEUX’s machine in 1912 such an experiment has not, as far as the writer can remember, been tried, and it seems likely to prove unsatisfactory for active service pilots."

  As at 1 May the first prototype had been abandoned but the second was still under test. Neither were considered better than the Spad fighters then in production and were not selected for production. It appears that a clipped wing version appeared in 1919 as a racing aircraft.


Nieuport Monoplane Specifications
Source 1 1 2 3. Ni.31.
Dimensions in m
   Span - - 9.40 8.60
   Length - - 6.40 6.60
   Height - - - 2.40
Area Wings in m2 17.5 17.5 17.5 193.76
Weights in kg
   Empty 440 433 433 500
   Military load* 100 100 - -
   Loaded 710 703 703 780
Performance
   Speed in kph
   Max - - 220 @ 4,000 m 230
   at 4,000 m 200 220 - -
Climb to
  to 4,000 m 13 min 13 min 13 min -
Endurance in hrs 2 2 2 2
Engine 180 Rhone 150 Mono. 150-hp Gnome Monosoupape 9N 180-hp Le Rhone -
Note: * Military load = crew and fuel.
Source:
1) "Department of Aircraft Production, British Ministry of Munitions of War, Paris, Monthly Aeroplane Report. May 1st 1918. French Experimental Aeroplanes, Scouts and Fighters." Chart from TNA AIR1/1071/204/5/1639. RAF Museum, J.M. Bruce Collection Box 15.
2) J.M Bruce data.
3) Green, W &. Swanborough, G. The Complete Book of Fighters, Greenwich Editions, UK. 2001.