Armstrong Whitworth A.W.41 Albemarle, B.Mk I Series I

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                 Armstrong Whitworth A.W.41 Albemarle, B.Mk I Series I

Development, Design and Service History:

Development

The origins of the Albemarle like most British aircraft that took part in the second world war, can be traced to a specification issued by the British air ministry in the mid-1930s. The Albemarle was a product of specification B.9/38, which requested the development of a twin-engine medium bomber of wood and metal construction, without the use of any light alloys, in order that the aircraft could be readily built by less experienced manufacturers from outside the aircraft industry. In addition to this, it was also asked that the aircraft could be engineered in a manner that would allow it to be divided into smaller compact subsections, that could fit on a standard Queen Mary trailer, in order to facilitate the adoption of a dispersed manufacturing strategy if necessary. The reason for this was due to the Air Ministry being concerned about a repeat of the first world war in which the restriction to supplies of critical materials from the colonies would result in an environment unsuitable for mass production efforts.

The Specification caught the attention of several aircraft manufacturers, including Armstrong Whitworth, Bristol and de Havilland, who were approached to produce designs to meet the specification. The design put forward by Armstrong Whitworth was named the AW.41 included a tricycle undercarriage and was as requested built of sub-sections to ease manufacture by firms without aircraft construction experience. The initial engines intended for the design were Rolls-Royce Merlin engines, but they made provisions for the use of Bristol Hercules as an alternative powerplant.

In June of 1938, mock-ups for both the AW.41 and Bristol 155 ( an improved Beaufort with tricycle landing gear and Taurus engines) were examined, resulting in revised specifications B.17/38 and B.18/38 being drawn up. It was at this point, de Havilland opted against submitting a design. The new specification outlined the requirements that the plane must be able to maintain 250 mph (400 km/h) at 15,000 ft (4,600 m) while carrying 4,000 lb (1,800 kg) of bombs

Due to Bristol being occupied with the production of other aircraft, they stopped development on the 155, resulting in only the development of the Albemarle continuing further past this point. Further changes came when the Air staff reconsidered the role that the Albemarle would serve within the airforce, as they settled on the concept of a Reconnaissance aircraft capable of carrying out bombing, resulting in the fuel capacity of the plane being increased to give it a range of 4,000 mi (6,400 km) range. This also resulted in defensive armament being added to the aircraft in the form of an upper dorsal turret and (retractable) ventral turret for downward firing.

Happy with the design, the ministry ordered 200 aircraft off the drawing board in October of 1938, without the production of a prototype. Due to the aircraft having a positive reputation within the ministry, there were initially high hopes for its performance, though it would never meet these lofty expectations. The first hurdle was the physical work that would be the construction of a pair of lead aircraft that would have to be test flown, prior to the commencement of full-rate manufacture of the type. This meant that the first Albemarle, serial number P1360, would not see her maiden flight until the 20th of March 1940, after being assembled at Hamble Aerodrome by Air Service Training.

Ironically the first flight for the aircraft was completely unintended, as the test pilot while undergoing taxying test runs managed to pick up too much speed, and had only managed to take off with the barest margin after traversing the entire runway. P1360’s bad luck would hold, and she was damaged after a forced landing during the test flight programme, but she was promptly repaired. These early tests according to test pilots showed the type was rather typical for her class, and was described as relatively average and free of any serious flaws. Even so, a number of modifications were made to the aircraft, including measures to improve take-off performance, which took the form of a wider span 77 ft (23 m) wing, and the thickening of the rudder’s trailing edge to correct a tendency to over-balance. Unfortunately, not all issues could be corrected though, and the engine overheating issues were never fully resolved, with the only real change being the raising of the maximum permissible operational temperature from 280C to 300C.

With these changes done, the Albemarle’s production was handed off to A.W. Hawksley Ltd of Gloucester, a subsidiary of the Gloster Aircraft Company, which was specifically formed to construct the Albemarle. The initial plans had been for the work to be undertaken at Gloster’s Brookwood facility, as both Gloster and Armstrong Whitworth were member companies of the Hawker Siddeley group, which was one of the largest Aircraft conglomerates in Britain at the time. In addition to this, parts for the Albemarle were produced by over 1,000 subcontractors, including MG Motor and Rover who worked on parts of the fuselage and wings, and Harry Lebus who build the tailplane units. The ultimate production of the Ablemarle would be 602 units when production was terminated in December 1944.

Design

The Albemarle was a mid-wing cantilever monoplane with twin fins and rudders, with the fuselage being built of three primary sections, composed of unstressed plywood over a steel tube framing. This design choice allowed the structure to be intentionally divided, in order to permit individual sections to be removed and replaced in the event of battle damage. The aircraft possessed a Lockheed-designed and hydraulically operated retractable tricycle landing gear, with the main wheels retracting into the engine nacelles and the nose wheel retracting backwards into the front fuselage, making this the first plane to see RAF service with a retractable nose wheel to be built in quantity.

Power for the aircraft was provided by a pair of Bristol Hercules XI air-cooled radial engines, each producing 1,590 hp, while driving a three-blade de Havilland Hydromatic propeller unit. Fuel would be generally stored in four tanks, two in the centre fuselage and two within the wings, though if the extended range was required an additional auxiliary tank could be installed within the aircraft bomb bay in a manner similar to other RAF bombers of the time. This large bomb bay was equipt with hydraulically operated doors and spanned the aircraft from just behind the cockpit to roughly halfway between the wings and the tail, allowing a lofty bombload of 4,500 pounds of ordnance.

The two pilots in this plane sat side by side, with a radio operator seated behind them. The navigator’s position was forward of the cockpit, with integrated bombsight to allow for accurate bombing. This glass nose was complimented with a glass observation section in the rear fuselage, where several glazed panels were present so a fire controller could help coordinate the aircraft’s defensive turrets against possible attackers. The dorsal turret was a Boulton-Paul design, which was both electrically operated and armed with four Browning machine guns. A fairing forward of the turret automatically retracted as the turret rotated allowing the turret to fire forward. This configuration gave the Albemarle a crew of six, including the two gunners, with one manning the four-gun dorsal turret and one in a manually operated twin-gun ventral turret, though this lower turret was only present in the first 32 aircraft, which were designated the Mk I Series I.

Unfortunately for the Albemarle, by the time they were available in quantity, they were already commonly considered to be inferior to several other aircraft already in RAF service, such as the well-known Vickers Wellington. This resulted in the class rarely being used for bombing operations, instead being used and configured as transports, under the name “general transport” or “special transport”. This change resulted in the elimination of the ventral turret, and the dorsal turret was downgraded to a manually operated twin gun arrangement. Other changes included the removal of bomb-aiming equipment and the rear fuselage tank, along with the addition of a quick-release hook allowing the aircraft to tow gliders. The aircraft could also be fitted out to serve as a paratrooper transport, with a maximum of ten fully armed troops being carried, who would exit via a dropping hatch in the rear fuselage, along with a large loading door on the right side of the aircraft.

Operational history

Due to the ambitions of using the Albemarle as a bomber role was dropped more or less immediately upon it entering service, the aircraft was mostly relegated to general reconnaissance and transport duties and thus was re-orientated towards such missions. Its moments of glory during the war took part during British airborne operations, beginning with the invasion of Sicily. The defining moment of its career though would be during the d-day landings on the night of 5/6 June 1944 when 295 and 296 Squadrons sent aircraft to Normandy with the pathfinder force, resulting in 295 Squadron being the first squadron to drop allied airborne troops over Normandy. During Operation Tonga four Albemarle squadrons were involved, followed by their involvement in Operation Mallard in which 220 Airseed Horsas and 30 Hamilcars were deployed to Normandy. Similar deployments occurred on the 17th of September 1944, when during operation market garden, 54 Horsas and two Waco Hadrian gliders were deployed over the Netherlands by 28 Albemarles of 296 and 297 squadrons, with another 45 aircraft sent the following day. Overall the Albemarle had a relatively safe service, with only 17 of the 602 aircraft made lost during operations with another 81 written off or lost during accidents. The aircraft would serve until February of 1946, when the heavy glider conversion unit replaced them with Hadley page Halifax bombers.

Aircraft Specification:


General characteristics

Crew:
Six (two pilots, navigator/bomb-aimer, radio operator and two gunners) in Bomber configuration
Length: 59 ft 11 in (18.26 m)
Wingspan: 77 ft 0 in (23.47 m)
Height: 15 ft 7 in (4.75 m)
Wing area: 803.5 sq ft (74.65 m2)
Empty weight: 25,347 lb (11,497 kg)
Max takeoff weight: 36,500 lb (16,556 kg)
Fuel capacity: 769 imp gal (924 US gal; 3,500 L) normal, 1,399 imp gal (1,680 US gal; 6,360 L) with auxiliary tanks
Powerplant: 2 × Bristol Hercules XI 14-cylinder air-cooled radial engines, 1,590 hp (1,190 kW) each
Propellers: 3-bladed de Havilland Hydromatic

Performance:
Maximum speed: 265 mph (426 km/h, 230 kn) at 10,500 ft (3,200 m)
Cruise speed: 170 mph (270 km/h, 150 kn)
Stall speed: 70 mph (110 km/h, 61 kn) (flaps and undercarriage down)[30]
Range: 1,300 mi (2,100 km, 1,100 nmi)
Service ceiling: 18,000 ft (5,500 m)
Rate of climb: 980 ft/min (5.0 m/s)

Armament:
Guns: Four × .303 in (7.7 mm) Browning machine guns in dorsal turret.
Two × .303 in (7.7 mm) machine guns in ventral turret
Bombs: Internal bomb bay for 4,500 lb (2,000 kg) of bombs

Additional Historical pictures:



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Sources:

2 Likes

+1, the UK needs mor light and medium bombers