The Jona J-6 was an experimental Italian

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 sesquiplane built in 1936 to demonstrate a novel, tilting wing stabilisation system. A military trainer

Trainer (aircraft)

A trainer is a class of aircraft designed specifically to facilitate in-flight training of pilots and aircrews. The use of a dedicated trainer aircraft with additional safety features—such as tandem flight controls, forgiving flight characteristics and a simplified cockpit arrangement—allows...

 development without the moving wing was produced in small numbers.

Design and development

The Jona J-6 was a very unusual design: not only was it a cantilever

Cantilever

A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...

 sequiplane, its lower wing having a span about two thirds that of the upper wing and having narrower chord

Chord

Chord may refer to:* Chord , an aggregate of musical pitches sounded simultaneously.** Chord an aggregate of musical pitches played simultaneously on a guitar* Chord , a line segment joining two points on a curve...

 but, uniquely, the upper plane was mounted to the fuselage

Fuselage

The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

 so that it could tilt about a longitudinal axis with respect to the rest of the aircraft. The objective was lateral stability; the aileron

Aileron

Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...

s were connected together and moved by the motion of the wing with respect to the fuselage so that if the port wing was raised by a gust its aileron was also raised, automatically correcting the roll. This system could only be implemented on a biplane

Biplane

A biplane is a fixed-wing aircraft with two superimposed main wings. The Wright brothers' Wright Flyer used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage, it produces more drag than a similar monoplane wing...

, with ailerons on the lower wing under the pilot's control used for turns in the usual way.

Because the upper wing tilted, it had to be a cantilever structure. It was built around two wooden spars

Spar (aviation)

In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings whilst on the ground...

, through whose centre passed a circular rod acting as hinge. This rod was held above the fuselage by four pairs of faired V-form struts with their eight ends fixed to it. Control wires from the ailerons were attached to this fixed rod, providing the required automatic deflections as the wing tilted. The rate of tilt was limited by a pair of telescopic, sprung struts from mid-chord quite close to the centre line, which met at the bottom centre of the fuselage after passing in through the upper sides. These could be hydraulically locked for aerobatics and spins or when stabilisation was not wanted. Leading edge automatic Handley Page slots were fitted to prevent spinning via wing tip stalling. The wing was plywood

Plywood

Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable, and can usually be locally manufactured...

 covered and straight tapered in plan, with semi-elliptical tips. The lower wing was generally similar, though much smaller and rigidly mounted.

The fuselage was built around a rectangular section steel tube structure, shaped into an oval with metal covering forward of the lower wing leading edge

Leading edge

The leading edge is the part of the wing that first contacts the air; alternatively it is the foremost edge of an airfoil section. The first is an aerodynamic definition, the second a structural one....

 and for the decking behind the cockpit, with fabric elsewhere. At the front a 140 hp (104 kW) Fiat A.54

Fiat A.54

-References:*...

 radial engine was mounted forward of the fuselage within a Townend ring

Townend ring

A Townend Ring is a narrow-chord cowling ring fitted around the cylinders of an aircraft radial engine to reduce drag and improve cooling.-Development:...

. The tandem cockpits were under continuous glazing with the forward seat under mid-wing, where a large cut-out eased visibility. The glazing was faired into the rear decking. The externally braced tailplane

Tailplane

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

 had a swept, straight leading edge and was mounted on top of the fuselage. It carried separate elevators

Elevator (aircraft)

Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...

, between which moved a deep, curved edged rudder

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

.

The mainwheels of the J-6 were mounted on split axles from the lower central fuselage, with shock absorbers fixed to the upper longerons. The wheels were spatted and the shock absorbers, though not their upper extension rods, were faired. The conventional undercarriage had a steerable, partly faired tailskid.

The Jona J-6 first flew on 24 May 1936. Its designer claimed that it could be flown without using the rudder, which was only needed on take-off or landing. It could not be spun or side-slipped when the upper wing was free to move, though with the wing locked it could be spun and looped at will.

After successfully completing its flight testing, the J-6 prototype was bought by the Italian government, though no more were built. The prototype of a development, the J-6S, built for Jona by Piero Magni Aviazione was flying by 1938. This aircraft, intended as a military trainer, was powered by a 240 hp (180 kW) Alfa-Romeo D.2C.30 radial engine and did not have the tilting wing but was otherwise closely similar to the J-6. The J-6S lacked a Townend ring cowling on the 9-cylinder radial, had the front cockpit set slightly further aft and had a tail wheel instead of a skid. Six J-6S were ordered but probably not used.

Variants

J-6

Built to test the stabilising wing sytem.

J-6S

Military trainer development with conventional wing and more powerful engine. 6 delivered to Italian Air Force.

Specifications (J-6)