Beardmore Inflexible and Inverness

Large two seat all-metal experimental aircraft to Air Ministry Specification 18/23, designed to evaluate stressed skin design and manufacturing. Beardmore collaborated with German company Rohrbach on the design of the aircraft, with whom it was known as the Rohrbach Ro VI. Beardmore outlined the aircraft’s basic specifications, Rohrbach supplying detailed drawings and some of the component parts, and Beardmore built the aircraft. The fuselage had a rectangular cross section and consisted of front and rear sections that were bolted together. Both sections were made of duralumin sheets riveted to a duralumin frame. Mounted to the rear of the fuselage were the horizontal and vertical stabilizers. The one piece elevator spanned the entire length of the horizontal stabilizer. A Flettner servo tab trailed behind the rudder and controlled its movement. The wings, which had 6° of dihedral, comprised a center wing section, which was continuous through the upper fuselage, and two outer panels. The main wing box girder was made up of two lattice girder spars joined top and bottom by plating that provided the wing surface. Sections of the leading and trailing edges of the wings were hinged for access and inspection of the inner wing. The wings were 'semi-cantilever', as each was supported in flight by a cable running from the lower longeron to the rear spar. The aircraft’s fuel was carried in four wing tanks. The Inflexible did not have any flaps, but its large ailerons spanned the outer half of each wing’s trailing edge. Extending from each of the aircraft’s control surfaces was an aerodynamic balance horn. The aircraft’s undercarriage consisted of large main wheels and a steerable tailwheel. Mounted to the wheels were 90-in diameter tyres, specially developed by the Dunlop Rubber Company. Each main wheel was supported by a shock-absorbing strut that extended from just inside the engine nacelle. An A-frame mounted to the lower fuselage secured each main wheel. Three 650 h.p. Rolls-Royce Condor II powerplants, one mounted in the nose and one under each wing. driving wooden, fixed-pitch, two-blade propellers.

Inflexible Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
156 ft 7 in	82 ft 9 in	21 ft 7 in	1892 sq ft	24923 lb	31400 lb		104 mph/ 90 kn		9350 ft
47.73 m	25.22 m	6.58 m	175.77 m2	11305 kg	14243 kg		167 km/h		2850 m

4 seat all-metal monoplane flying boat to Air Ministry Specification 20/24, ordered by the Air ministry to compare with the wooden biplanes currently in service with the Royal Air Force. The aircraft was based on the German Rohrbach Ro III, but powered by Napier Lion engines, and to the German company it was known as the Rohrbach Ro IV. The aircraft was constructed mainly of duralumin, with some steel fittings, the whole being skinned in duralumin sheet. The high aspect ratio cantilever high wing was of strictly rectangular planform, featuring a thick aerofoil section and 6° of dihedral. The structure was based on a deep chord central box spar built of cannel sections, the upper and lower sections of which formed the stressed skin wing surface, and attached to the top of the fuselage sides. Balanced rectangular ailerons filled about 35% of the trailing edges out to the tips, extending from which was an aerodynamic balance horn. The leading and trailing edges were hinged to the main wing box, enabling inspection of the wing structure.The two engines were mounted in streamlined tractor nacelles above the wing centre section. The hull was rectangular, with flat sides and top. Its planing bottom was also flat, with two steps. Stability on the water was provided by long, stepless floats on each side, strut-mounted from the wings a little outside the engines and braced to the fuselage with a parallel pair of horizontal struts. The hull tapered in plan to the tail, where the empennage was again rectangular, with a broad fin reaching out beyond the end of the hull and carrying a balanced rudder. The square cut, strut braced tailplane was mounted on the fin about one third of the way up, and carried split unbalanced narrow-chord elevators. Two crew were located in an open cockpit just ahead of the propeller discs, the other two in the fuselage or occupying the nominal gunners positions in the nose and rear fuselage. Two 450 h.p. Napier Lion

Inverness Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
94 ft	56 ft 11 in	16 ft 3 in	761 sq ft	9597 lb	12500 lb		110 mph/ 96 kn		8750 ft
28.65 m	17.35 m	4.95 m	70.7 m2	4353 kg	5670 kg		177 km/h		2667 m