STIRLING Mk.I

The Short Stirling was the first four-engined British heavy bomber of the Second World War. The design had high wing, four engines and the cabin elevated over the fuselage. The airframe was fully made in metal. Another features that characterised the bomber was the impressive size of the landing gears. The first bombers went to equip the Royal Air Force Bomber Command Squadrons from the end of 1940. The Operational status was reached on January 1941 and the first war mission was dated February 1941 against logistic installation in Rotterdam. Stirling Mk.I was able to carry a significant offensive load of over 6,000 Kg of bombs and was armed with eight 7.7 mm machine guns for defense. However the performance and the reliability of the Stirling was not so impressive and it was replaced, in just two years, by more modern and efficient bombers such as the Halifax and the Lancaster.

The slab-sided Stirling was Britain’s first strategic bomber and the first to achieve operational status during World War II. Visually impressive, it suffered from poor altitude performance and was eventually eclipsed by the Avro Lancaster and Handley Page Halifax.

In 1936 the British air staff sought acquisition of its first strategic bomber, so the Air Ministry issued Specification B.12/36 for a four-engine aircraft. Several prototypes were entered by different firms, but Short’s model proved the most successful. It was a large, high-wing monoplane with smooth, stressed skin. The fuselage was rather long, was slab-sided, and housed three power turrets for defense. Because the wing was so far off the ground, enormous landing gear were required, causing the aircraft to appear larger than it actually was. A potential problem was the wingspan. Because ministry specifications mandated that the new craft should fit into existing hangars, its wings could not exceed 100 feet. Thus, the Stirling, which was rather large, always suffered from insufficient lift. Nonetheless, the decision was made to acquire the bomber in 1939, and within two years the first squadrons were outfitted.

In service the Stirling enjoyed a rather mixed record. The big craft was structurally sound and, at low altitude, quite maneuverable for its size. However, its short wing enabled it to reach barely 17,000 feet while fully loaded—an easy target for antiaircraft batteries and enemy fighters. Another unforeseen shortcoming was the bomb bay, which was constructed in sections and could not accommodate ordnance larger than 2,000 pounds—the largest weapon available in 1938. Thus, unlike the Halifaxes and Lancasters that followed, its utility as a strategic weapon was decidedly limited. Stirlings nonetheless performed good service with RAF Bomber Command until 1944, when they were relegated to secondary tasks. Foremost among these was glider-towing, which they extensively performed at Normandy in June 1944. By 1945 Stirlings had flown 18,446 sorties and dropped 27,281 tons of bombs. A total of 2,373 were constructed.

Specifications (Short Stirling I)

General characteristics

    * Crew: 7 (First and second pilot, navigator/bomb-aimer, front gunner/WT operator, two air gunners, and flight engineer)

    * Length: 87 ft 3 in (26.6 m)

    * Wingspan: 99 ft 1 in (30.2 m)

    * Height: 28 ft 10 in (8.8 m)

    * Wing area: 1,322 ft² (122.8 m²)

    * Empty weight: 44,000 lb (19,950 kg)

    * Loaded weight: 59,400 lb (26,940 kg)

    * Max takeoff weight: 70,000 lb (31,750 kg)

    * Powerplant: 4× Bristol Hercules II radial engine, 1,375 hp (1,030 kW) each

    * Propellers: Three-bladed metal fully feathering 13 ft 6 in diameter propeller

    * *Aspect ratio: 6.5

Performance

    * Maximum speed: 255 mph (410 km/h) at 21,000 ft (6,400 m)

    * Cruise speed: 200 mph[24]

    * Range: 2,330 mi (3,750 km)

    * Service ceiling: 16,500 ft (5,030 m)

    * Rate of climb: 800 ft/min (4 m/s)

    * Wing loading: 44.9 lb/ft² (219.4 kg/m²)

    * Power/mass: 0.093 hp/lb (0.153 kW/kg)

Armament

    * Guns: 8 x 0.303 in (7.7 mm) Browning machine guns: 2 in powered nose turret, 4 in tail turret, 2 in dorsal turret

    * Bombs: Up to 14,000 lb (6,340 kg) of bombs

Specifications (Short S.29 Stirling Mk III)

Type: (Mk I & III) Seven or Eight Seat Heavy Bomber (Mk IV) Glider Tug & Troop Transport (Mk V) Transport, Heavy Freighter & Air Ambulance

Accommodation/Crew: A crew of eight was carried on early Stirlings comprising of the Pilot and Co-Pilot, Navigator/Bomb-aimer, Wireless/Radio Operator, three air-gunners and a Flight Engineer. On later aircraft the position of the second pilot was removed. Crew positions also changed slightly depending on defensive armament carried. The Bomb-aimer was in the nose below the pilot's floor and under the nose gun turret. Pilots coupé gives not only good forward view but is designed to permit fighting controller to operate with minimum of interference during enemy fighter attack. The navigator is also seated within the coupé boundry. Retractable astral dome superimposed with escape hatch just aft of back end of coupé. Armoured bulkhead with hinged door separates flight compartment from engineer and wireless-operator. First pilot has additional armour to his back and head and the fighting controller has armour protection to his chest when attending to the air-gunner's position. Centre-section above bomb floor is braced to allow egress aft and also provides stowage space and rest quarters for any member of the crew. A bunk is fitted on the starboard side of this compartment. Aft of centre-section is the mid-upper turret and the servo-feed ammunition boxes to the tail turret. Aft of the bomb-bay are the multi flare chutes and a walkway to the tailplane spar frames and through them to the tail turret. Main entrance door to fuselage is fitted aft of the flare station. There were escape hatches in the nose at the Bomb-aimers position, above the Pilot's seat, two on top of the fuselage and one near the tailgunner's position.

Design: Designer Arthur Gouge of Short Brothers Limited

Manufacturer: Short Brothers (Rochester & Bedford) Limited based in Rochester, Kent, England. The company was founded in 1898 by the brothers Eustace and Oswald Short, originally building spherical balloons but they later concentrated on the building of Flying Boats. In 1936, Short Brothers Limited and Harland & Wolff Limited (Shipbuilders) of Queen's Island, Belfast, Northern Ireland, formed a partnership under the name Short & Harland Limited. Also built by Austin Motors Limited in Longbridge. Production would eventually be dispersed to over 20 different factories.

Powerplant: Four 1,675 hp (1250 kW) Bristol Hercules XVI 14-cylinder sleeve-valve double-row air-cooled radial engines rated at 2,900 rpm at 4,500 ft (1370 m); 1,615 hp (1205 kW) at 2,900 rpm for take-off; 1,050 hp (783 kW) at 2,400 rpm at 10,250 ft (3130 m). Engine weight (dry) 1,930 lbs (875 kg). The fuel used was 100 or 130 octane. The propeller was a metal three-bladed de Havilland Hydromatic Type 55/10 variable pitch, constant speed full-feathering airscrew with a diameter of 13 ft 6 in (4.11 m).

Performance: Maximum speed 270 mph (435 km/h) at 14,500 ft (4420 m); economical cruising speed of 233 mph (375 km/h) at 11,000 ft (3355 m); service ceiling 17,000 ft (5180 m); initial rate of climb 800 ft (245 m) per minute.

Fuel Capacity: Seven cylindrical self-sealing (except the leading-edge tank) fuel tanks in each wing outboard of the wing bomb cells, giving a total of 2,254 Imperial gallons (2,707 US gallons or 10246 litres), plus provision for 220 Imperial gallons (264 US gallons or 1000 litres) of auxiliary fuel in tanks installed in each of the wing bomb cells for an additional total of 440 Imperial gallons (528 US gallons or 2000 litres). The systems could be interconnected if necessary by operating an inter-system balance cock in the centre section.

Oil Capacity: Each engine had its own oil tank with a capacity of 33 Imperial gallons (40 US gallons or 150 litres).

Range: 590 miles (950 km) on internal fuel with a bombload of 14,000 lbs (6350 kg). 2,010 miles (3237 km) on normal internal fuel with a bombload of 3,500 lbs (1587 kg). Ferry range (clean) of over 3,000 miles (4831 km) was possible using auxiliary fuel tanks. Range on the Short S.29 Stirling was one of its major weaknesses. While it was capable of carrying a tremendous amount of ordnance, it could only do this a very short distance. As a result, on most missions to get the desired range, bombload was sacrificed.

Weights & Loadings: Empty (clean) 43,200 lbs (19595 kg), empty (equipped) 59,400 lbs (26939 kg) with a maximum take-off weight of 70,000 lbs (31751 kg). Wing loading 48 lbs/sq ft (234 kg/sq m); power loading 10.6 lbs/hp (4.85 kg/hp).

Dimensions: Span 99 ft 1 in (30.20 m); length 87 ft 3 in (26.59 m); height 22 ft 9 in (6.93 m); wing area 1,460.0 sq ft (135.63 sq m).

Armament: A total of eight 7.7 mm (0.303 in) Browning machine-guns plus up to 14,000 lbs (6350 kg) of bombs. Disposable stores were carried in a lower fuselage weapons bay rated at 11,000 lbs (4989 kg) and in 6 wing cells each rated at 500 lbs (227 kg). Normal loadout usually consisted of 2,000 lbs (907 kg) armour-piercing bombs and/or 500 lbs (227 kg) general-purpose high explosive bombs. The main bomb-bay in the fuselage is formed of two main longitudinal girders with arched members to the main floor. The bay is 42 ft 7 in (13.0 m) long and fitted with six hinged doors. Internal stowage for bombs is also provided in the centre-section inboard of the inner engine nacelles. A bomb overload of up to 25,500 lbs (11567 kg) was possible but it reduced the range considerably.

      2 × 7.7 mm (0.303 in) Browning trainable forward-firing machine-guns in the power-operated Frazer-Nash F.N.5 nose turret.

   

      2 × 7.7 mm (0.303 in) Browning trainable machine-guns in the power-operated Frazer-Nash F.N.50 (Boulton-Paul) dorsal turret.

      4 × 7.7 mm (0.303 in) Browning trainable rearward-firing machine-guns in the power-operated Frazer-Nash F.N.20A tail turret.

      1 x 7.7 mm (0.303 in) Browning trainable rearward firing machine-gun in a manually operated ventral position (Some aircraft only).

Variants: Stirling Mk I, Stirling Mk II (two prototypes only), Stirling Mk III, Stirling Mk IV, Stirling Mk V (transport).

Equipment/Avionics: Standard communications and navigation equipment. Aircraft in the role of pathfinder carried H2S bombing radar. It was also the first RAF Bomber to carry "Oboe" navigation radar. Standard equipment would have also included de-icing equipment fitted to the leading-edges of the wings, tailplane and fin. Several fire extinguishers and crash axes were positioned inside the aircraft fuselage. There was also equipment on board to destroy radio and bombsight equipment or set the aircraft on fire in case of an emergency landing. Individual dinghy kits were stacked in racks inside the Stirling, usually in combination with parachute stowage racks. Dinghy radio equipment was stowed in the fuselage. The Type J Dinghy for eight men was stowed in the Port wing. Complete with topping up bellows, leak stoppers, rescue line and knife. The Dinghy could be released from inside the fuselage or from the outside, or automatic by flooding of the immersion switch located in the fuselage nose. Emergency equipment was carried in a Lindholme Dinghy Container, including a first aid pack, corned beef cans, services and RAF flying rations, rum and cigarettes. Engine maintenance platforms and ladders were carried in the fuselage. Oxygen equipment was provided for all crew members. First aid kits were located on the fuselage sides behind the Pilot seat (two on the starboard and one on the port side). A Mk.XIV bomb sight control panel used in conjunction with a Mk.XIV bomb sight computer was used by the Bomb-aimer.

Wings/Fuselage/Tail Unit: The wings are of a mid-wing cantilever monoplane type with a two-spar all-metal structure similar to that of the Short "Empire" flying boat. Gouge type trailing-edge flaps with chord equal to 48 percent of the total chord. The leading-edges of the wings are armoured and are provided with barrage-balloon cable cutters. The fuselage is a rectangular section with rounded corners with an all-metal structure built up of transverse frames covered with aluminium-alloy sheet with intercoastal stiffeners and all joints joggled flush with flush riveting. The tail unit is a cantilever monoplane type with a single fin and rudder similar in form and construction to those of the "Empire" flying boats.

Landing Gear: The landing gear was a two-stage retractable type with the main wheels retracting vertically and then backwards into the inner engine nacelles taking part of their fairings with them. Retraction was powered by electric motors with alternative hand operation. Twin castoring retractable tailwheels type Dunlop WS30. In order to accommodate the RAF Bomber Command requirement to shorten the take-off and landing, a very long landing gear was utilized making the aircraft prone to swing violently on take-off and landing. The undercarriage retraction motors were originally located inside the nacelle, but were later relocated inside the fuselage to allow for manual retraction in the event of motor failure. The electric retraction motors often failed, being wholly inadequate for the task. The Stirling had one of the largest tires, manufactured by Dunlop, on a British aircraft at the time.

History: First flight (S.31 research aircraft) 19 September 1938; first flight (S.29 prototype) 14 May 1939; first flight (production Mk I) 7 May 1940; final operational sortie 8 September 1944; final production (Mk V) November 1945; withdrawn from service (RAF) 1946.

Operators: United Kingdom (RAF).

Units: They initially entered service with No.7 Squadron and at the peak of their service they equipped 13 RAF Bomber Command Squadrons (Nos.7, 15, 75, 90, 101, 149 166, 199, 214, 218, 513, 622 and 623). Starting in 1944 the main role of the Stirling was that of glider-tug and transport with RAF Transport Command. For D-Day on 6 June 1944 RAF Transport Command Squadrons Nos 190 and 622 from Fairford and Nos 196 and 299 from Keevil towed Airspeed Horsa gliders into Normandy. Late in the war, Squadron Nos 171, 295, 570, 620 and 624 also used the Stirling and participated in the airborne landings in Arnhem and the March 1945 attack across the Rhine. Squadron Nos 138 and 161 were (Special Duties) Squadrons, flying for the Special Operations Executive (SOE) from Tempsford, near Cambridge. They performed Covert Operations supplying arms to the Resistance in occupied countries. Based in Blida, North Africa, No. 624 Squadron performed the same task in the Mediterranean area.