The Potez 51 was a 1930s French intermediate trainer, intended to replace the ageing

Potez 25 Potez 25 (also written as Potez XXV) was a French twin-seat, single-engine sesquiplane designed during the 1920s. A light multi-purpose Strike fighter, fighter-bomber, it was designed as a line aircraft and used in a variety of roles, including F ...

which had sold worldwide. It did not go into production.

Design

Although the main rôle of the Potez 51 was as an intermediate trainer Potez, with their very successful

in mind, hoped that it would also serve as a photographic

reconnaissance aircraft A reconnaissance aircraft (colloquially, a spy plane) is a military aircraft designed or adapted to perform aerial reconnaissance with roles including collection of imagery intelligence (including using Aerial photography, photography), signals ...

, an air-ambulance and, in the civil sphere, a grand tourer. It was a

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

with a constant chord

parasol wing A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

with about 2.5° of sweep. The tips were semi-circular and there was a deep, rounded cut-out in the

trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...

over the

cockpit A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

s. High

aspect ratio The aspect ratio of a geometry, geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangl ...

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

occupied the whole trailing edge. The wing was built around wooden box-spars and was fabric covered. It was braced to the lower

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

by parallel

strut A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension. A stay is sometimes used as a synonym for ...

s to the wing beyond mid-span. Four

cabane struts In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both internally and externally, and may take the form of struts, which act in ...

from the upper fuselage on each side braced the wing centre section. Its fuselage was largely wooden, with

spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...

longeron In engineering, a longeron or stringer is a load-bearing component of a framework. The term is commonly used in connection with aircraft fuselages and automobile chassis. Longerons are used in conjunction with stringers to form structural fram ...

s and ply skin, though the forward section, which contained the Potez 9A

radial engine The radial engine is a reciprocating engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

, had metal bearers and removable metal sheet covering. The engine was enclosed by a

NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency that was founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its ...

long chord

engine cowling An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gene ...

. Behind the engine the fuselage was flat sided, though with rounded decking both forward and aft of the two open

s, the forward one under the

cut-out and the other close behind. Fairings ahead of each gave protection from the slipstream and dual controls were fitted. Both

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...

and

tailplane A tailplane, also known as a horizontal stabilizer, is a small lift (force), lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters ...

were essentially triangular and carried balanced control surfaces. The tailplane was mounted on top of the fuselage and its angle of incidence could be adjusted in flight; it was braced on each side at the apex of a V-strut from the lower fuselage. The Potez 51 had fixed

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for taxiing, takeoff or landing. For aircraft, it is generally needed for all three of these. It was also formerly called ''alighting gear'' by some manufacturers, s ...

, with mainwheels on cranked axles and drag struts from the lower fuselage; near vertical shock absorbing legs were attached to the forward wing struts, reinforced at their tops by struts inwards to the upper fuselage. The wheels were enclosed in semi-circular fairings. There was a short tailskid.

Development

The trainer was on display, unflown, at the 1932 Paris Salon. Its first flight was made towards the end of January 1933. Trials continued into 1934, though by August 1933 the aircraft was well harmonized. In November the

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

had to be modified to meet homologation requirements, as Potez had initially underestimated the full power of their new engine, at 2,100 rpm. Finally in March 1934 the factory testing was done and the Potez 51 went to Villacoublay for official evaluation. Its fate is not recorded in the contemporary French aviation journals, but it seems no more were built.

Specifications

References

{{Potez aircraft Parasol-wing aircraft 1930s French military trainer aircraft 051 Single-engined tractor aircraft Aircraft first flown in 1933