WEAPONS THAT MIGHT HAVE....... by Victor Durrell First in an occasional series on aircraft, ships or other weapons which might have been... MARTIN-BAKER M.B.5 (British) In 1939 the Martin-Baker were awarded a contract to develop a fighter aircraft in advance of that being contemplated by their larger contemporaries (eg F18/37 which resulted in the Hawker Typhoon). The result was the M.B.3 built round the Napier Sabre an engine with an unfortunate development history of failures and fires. When the Martin-Baker M.B.3 crashed on 12 September 1942, the company held an Air Ministry contract to build two more prototypes, but assembly of these aircraft had not yet begun. Improvements had already been planned, including the use of an all-round vision cockpit canopy with cut-down rear fuselage, but a more extensive redesign was now put in hand, since the likelihood that the M.B.3 would be needed in quantity had receded with the advent of the Hawker Typhoon and the changing priorities of the RAF. In place of the Sabre engine, a Griffon was adopted, the choice finally falling upon the Mk 83 version of this engine driving counter rotating propellers, and in this guise the second prototype was designated M.B.5 In the event, little progress was ever made towards fabrication of the third machine, but it was assumed that this would also be an M.B.5. In place of the M.B.3's underwing radiator, the M.B.5 had a large intake duct under the fuselage aft of the wing, containing the inter-cooler, main cooler and oil cooler radiator; a small lip intake under the spinner supplied air to the carburettor. The deeper rear fuselage that resulted called for the use of a longer tailwheel than on the M.B.3 and the cockpit, with its tear-drop hood, was moved forward to improve the view over the longer nose. Wing and undercarriage remained unchanged in form from the M.B.3, but the radiators were, of course, removed, as were the two outer cannon, as it was now recognised that a four-cannon armament represented an entirely adequate punch for a single- seat fighter. Fuel was contained in two tanks in the centre fuselage, one ahead of and one behind the cockpit. Just aft of the rear tank, the fuselage contained the large pneumatic ram that, as on the M.B.3, powered the undercarriage and flaps; the connections to the main oleo legs were by cable for raising, with spring-operated radius rods for lowering and a hydraulic damper on the ram to control the rate of descent of the undercarriage (this being the only use of hydraulics in the entire aircraft). Dunlop pneumatic brakes were fitted, operated differentially through the rudder bar when the handbrake was "on", and the tailwheel was self-centring. Some further refinements were made to the original Martin structural concept. The fuselage was still of tubular steel construction, with all joints made by tapered bolts finished to close tolerance. Attached to the basic frame were light alloy formers to give the fuselage its final shape, and these formers supported heavy-duty rubber beading which provided a bed for the skin panels, which were attached by Dzus fasteners. The engine cowling and large areas of the fuselage skin were thus quickly removable, giving access to all parts of the aircraft structure, all accessories, attachment points of all components and all filters. The wing differed structurally only in minor respects from that of the M.B.3 and, indeed, the M.B.2. Once again, large panels gave immediate access to the gun bays and a servicing platform could be quickly attached for use by the armourer. All control surfaces were conventionally operated by tubular push-pull rods passing through bearings that could be easily reached for lubrication. With the exception of the fabric covered rudder, the flying controls were metal-skinned; all had spring-loaded servo tabs, that fitted to the rudder being operable from the cockpit, and the elevators also had normal trim tabs. The cockpit layout of the M.B.5 received special attention and was to draw almost universal praise from all who flew or examined the aircraft after its completion. A clean floor was provided -- at a time when the "floor" of most fighter cockpits was no more than the inside of the lower fuselage - - and the flying controls, comprising stick and rudder bar, were built up to be installed, or removed for servicing or repair, as a single unit. The control panel comprised three major sections, of which that in the centre comprised the blind-flying instruments, with engine instruments on the starboard side and flap controls and supercharger selection to port; each panel was hinged to fold forwards into the cockpit, giving easy access to the rear of the instruments. Completed at Denham in the spring of 1944, the M.B.5 was fitted with the angular fin and rudder and small tailplane as used on the M.B.3; stub fairings were fitted on the cannon positions in the wings. In this form, the prototype was transported -- in its quickly dismantled form -- to RAF Harwell, where the first [light was made on 23 May 1944, the pilot being Capt Bryan Greensted, the then chief test pilot of Rotol Ltd who had been seconded for the job by the Ministry of Aircraft Production. Early test flights quickly revealed a lack of directional stability and a larger fin and taller rudder soon appeared. Thus modified, the M.B.5 proved to be excellent in both performance and handling. With 25 Ib/sq in (1,76 kg/cm2) boost and 130 octane fuel, the Griffon 83 was able to produce a maximum of 2,340 hp and bestowed on the M.B.5 a top speed of 460 mph (740 km/h) at 20,000 ft (6 100 m) -- quite possibly a record for piston engined aircraft at the time although both the Hornet and the Spiteful achieved higher speeds eventually. Nevertheless, flight hours were built up only slowly -because it was already clear, by the middle of 1944, that the M.B.5 would not be required for production. Between May 1944 and October 1945, the M.B.5 accumulated some 40 flight hrs, before making its first public appearance at the end of that month (with an enlarged tailplane with greater chord now fitted) when the RAE Farnborough put on a flying exhibition of the latest British aircraft. A little more flying was done with the M.B.5 for a year or two, before this final flying prototype produced by the Martin-Baker company was scrapped. Martin-Baker M.B.5 Specification Power Plant: One Rolls-Royce Griffon 83 liquid-cooled 12 cylinder V-engine rated at 1,900 hp for take-off with 18 Ib/sq in (1,27 kg/cm2) of boost; max output with 25 Ib/sq in ( 1,76 kg/cm2) boost, 2,305 hp in "M" gear at 500 ft ( 153 m) and 2,060 hp in "S" gear at 15,700 ft. De Havilland six- blade counter-rotating constant speed propeller of 12 ft 6 in (3,81 m) diameter. Fuel capacity, 70 Imp gal (318-1) in fuselage tank ahead of cockpit and 130 Imp gal (591 -1) in second fuselage tank aft of cockpit. Performance: Max speed, 395 mph (636 km/h) at sea level, 425 mph (684 km/h) at 6,000 ft ( 1 830 m) and 460 mph (740 km/h)at 20,000 ft (6 100 m); normal cruising speed, 320 mph (515 km/h) at 10,000 ft (3 050 m) and 360 mph (579 km/h) at 20,000 ft (6 100 m); most economical cruising speed, 250 mph- 325 mph (402-523 km/h) at 20,000 ft (6 100 m); take-off distance to 50 ft (15,2 m), 1,620 ft (494 m); initial rate of climb, 3,800 ft/min ( 19,3 m/sec); rate of climb at 7,000 ft (2 134 m), 4,000 ft/min (20,3 m/sec); time to 20,000 ft (6 100 m), 6.5 min; time to 34,000 ft (10 363 m), 15 min; service ceiling, 40,000 ft (12 192 m); range, 1,100 mls (1 770 km) at 250 mph(402km/h) and 950 mls (l 529 km) at 325 mph (523 km/h); landing distance from 50 ft (15,2 m), 1,650 ft (503 m). Weights: Tare, 9,233 lb (4 192 kg); normal take-off, 11,000 lb (4 994 kg); max overload, 12,090 lb (5 489 kg). Dimensions: Span, 35 ft O in (10,67 m); length, 37 ft 03/4 in (11,3 m); height (tail down), 14 ft 4 in (4,37 m); undercarriage track, 15 ft 2 in (4,62 m); wing area, 263 sq ft (24,4 m2); dihedral, 41/2 deg constant. Armament: Four 20-mm Hispano Mk II cannon with 200 rpg, fixed forward-firing in wings. Postscript: One by product of the loss of the M.B.3 and Captain H.V Baker one of the founders of the company was a change in direction of the company. From being a company sub-contracting aircraft assemblies for larger concerns (and with a hankering to develop its own) Martin-Baker moved into the development of ejection seats and is still in the forefront of design and production of this vital equipment..