# Nieuport 31

The Nieuport Nie 31 or Nieuport 31 was a single-engine, single-seat monoplane or sesquiplane fighter aircraft designed and built in France in 1919.

## Design and development

Though the Nie 31 (it had been flown and subsequently abandoned before the company changed its name to Nieuport-Delage) was technically a sesquiplane, it could equally well be described as a shoulder-wing monoplane with a small foreplane. Its immediate predecessor was the Nieuport Madon, which had an ancillary lifting surface built around the axle of its wide-track undercarriage. The Nie 31 had a narrower-track undercarriage, but the second wing extended outwards beyond the wheels, which were faired into its upper surface; this wing and the axle were joined to the lower fuselage by a pair of near vertical N-form struts.
The main plane was of low aspect ratio. In plan it had a rounded leading edge, straight trailing edge and square tips. Its roots were cut away to allow a better downward view from the cockpit. This was placed ahead of the trailing edge so the pilot looked forward over the wing; he had a faired headrest behind. The Nie 31's upper wing had ailerons but no flaps and was braced on each side by a parallel pair of aerofoil section struts stretching outwards from the bottom of the undercarriage struts. The lower wing had parallel chord and straight edges, providing a lifting surface with about 40% the area of the main plane. Both wings were fabric covered.
The Nie 31 was powered by a 130 kW (180 hp) Le Rhone 9R nine-cylinder rotary engine, smoothly and completely cowled. It drove a two-blade propeller. The fuselage, like that of the earlier Nieuport Nie 29, was a smooth wooden monocoque shell of tulipwood, produced by winding thin spiral strips around a mould in a series of alternately handed layers and glueing them together. It tapered to the rear, where an almost delta-shaped tailplane was mounted at mid-height, carrying horn-balanced elevators. The fin was much less broad, with a straight-edged, balanced rudder extending down between the elevators below the lower fuselage, where there was a small dorsal fin.
The Nie 31 was intended to carry twin 7.7 mm (0.303 in) Vickers machine guns. A flight test programme conducted through 1919 showed that the Nie 31 had excellent performance, especially given the low engine power, but Nieuport did not proceed with its development as a fighter, however the Nieuport-Delage Sesquiplan was a direct evolution of this design, but powered with a Hispano-Suiza 8 water-cooled V8 engine, and was built specifically for racing.

## Specifications

Data from The Complete Book of Fighters: An Illustrated Encyclopedia of Every Fighter Built and Flown
General characteristics
* Crew: One
* Length: 6.60 m (21 ft 8 in)
* Wingspan: 8.60 m (28 ft 3 in)
* Height: 2.40 m (7 ft 10 in)
* Wing area: 18.0 m$^2$ (194 sq ft)
* Empty weight: 500 kg (1,102 lb)
* Gross weight: 780 kg (1,720 lb)
* Powerplant: 1 × Le Rhone 9R nine cylinder rotary engine, 130 kW (180 hp)
* Propellers: 2-bladed fixed pitch
Performance
* Maximum speed: 230 km/h (140 mph, 120 kn)
* Endurance: 2 hours
* Service ceiling: 6,000 m (20,000 ft)
Armament
* 2 × fixed 7.7 mm (0.303 in) Vickers machine guns in nose