Production was authorized while the aircraft was still in the design stage, an order for 80 aircraft being placed in August 1935. Alan Campbell-Orde flew the first prototype (K4586) at Whitley Abbey on 17 March 1936, the machine's two Armstrong Siddeley Tiger X engines turning the then new three blade variable pitch de Havilland propellers. A second prototype built to Specification B.21/35 had the more powerful 795 hp (593 kW) Armstrong Siddeley Tiger IX 14-cylinder radial engines driving three bladed two-pitch propellers and was flown by Charles Turner Hughes on 24 February 1937.

The speed of the aircraft’s construction had led to some compromises in its design. Although the fuselage was a modern aluminium monocoque design, the wing wasn’t. It was built in three pieces around a huge box spar; with structures formed from aluminium sections attached front and rear, which were then clad in a mixture of non-structural aluminium sheets and fabric. This was a heavier arrangement than the more modern, but less understood stressed skin construction. The wing was also set at a huge incidence angle of 8.5 degrees to reduce the aircraft’s angle of attack while landing. The late addition of hydraulic landing flaps had made this unnecessary, but it was by then too late to change. In level flight this high wing incidence caused the fuselage to fly several degrees nose down, thereby increasing drag. Trials at the Aircraft and Armament Experimental Establishment at Martlesham Heath were undertaken in the autumn of 1936, The first production Whitley Mk Is were delivered early in 1937, including the second aircraft which was flown to RAF Dishforth on 9 March for No. 10 Squadron. Thirty-four Mk Is where built before the Whitley Mk II was introduced. This mark had Tiger VIII engines with two speed superchargers, the first fitted to an RAF aircraft; 46 Whitley Mk IIs completed the initial order for 80 aircraft.

Mk I and Mk II Whitleys had Armstrong Whitworth manually operated nose and tail turrets, each with a 7.7 mm (0.303 in) Vickers machine gun, but in the Whitley Mk III the nose turret was replaced by a power operated Nash and Thompson turret, and a retractable ventral turret with two 7.7 mm (0.303 in) Brownings was added. The 80 Whitley IIIs also had modified bomb bays to accommodate larger bombs then being introduced in the RAF.

By far the most numerous of the Whitley variants were those with Rolls-Royce engines. A Whitley Mk I was fitted with Merlin IIs and test flown at Hucknail on 11 February 1938, although engine failure prematurely concluded the second flight. The program was quickly resumed, however, and during April and May the aircraft carried out trials at Martlesham Heath.

Rolls Royce Merlin IV 12-cylinder Vee liquid-cooled engines rated at 1,030 hp (768 kW) for take-off and 990 hp (739 kW) at 12,250 ft (3740 m) driving Rotol constant speed propellers were installed on production Whitley IVs, the first of which flew on 5 April 1939. Other changes incorporated in this version included a power operated Nash and Thompson tail turret with four 7.7 mm (0.030 in) Browning machine guns. A transparent panel was added in the lower nose to improve the view for the bomb aimer, and two additional wing tanks were fitted to bring the total capacity to 705 Imperial Gallons (3205 litres). Production totalled 33, together with seven Whitley Mk IVAs which had 1,145 hp (854 kW) Merlin X engines.

The same engines were retained for the Whitley V, which incorporated a number of improvements. The most noticeable of these were modified fins with straight leading edges and an extension of 1 ft 3 in (0.38 m) to the rear fuselage to provide a wider field of fire for the rear gunner. Rubber de-icing boots were fitted to the wing leading edges, and fuel capacity was increased to 837 Imperial Gallons (3805 litres) or 969 Imperial Gallons (4405 litres) if extra tanks were carried in the bomb bay. Production totalled 1,466 aircraft.

The Whitley VI was a projected version with Pratt & Whitney engines, studied as an insurance against a possible short supply of Merlin engines. It was not built, however, and the ultimate production Whitley was the Whitley Mk VII which was essentially a Mk V with auxiliary fuel tanks in the bomb bay and in the rear fuselage to bring the total capacity to 1,101 Imperial gallons (1333 US gallons or 5000 litres) increasing the range to 2,300 miles (2701 km) for maritime patrol duties. Externally the Mk VIIIs could be distinguished by the dorsal radar aerials of the ASV Mk II Air-to-Surface radar. Production reached 146 aircraft, and some Mk Vs were converted to this standard.

As noted above, No. 10 Squadron at RAF Dishforth was the first to equip with the Whitley, which replaced the Handley Page Heyford in March 1937. Nos. 51 and 58 Squadrons at RAF Leconfield soon followed and during the night of 3 September 1939, ten Whitley IIIs from these two squadrons flew a leaflet raid over Bremen, Hamburg and the Ruhr. Just under a month later during the night of 1 October, No. 10 Squadron flew a similar mission over Berlin. The first bombs were dropped on Berlin during the night of 25 August 1940, the attacking squadrons including Nos. 51 and 78 with Whitleys. To mark the entry of the Italians into the war, 36 Whitleys drawn from Nos. 10, 51, 58, 77 and 102 Squadrons were tasked to raid Genoa and Turin during the night of 11 June 1940, although only 13 aircraft actually reached their targets due to a combination of inclement weather and engine troubles.

The Whitley retired from Bomber Command in April 1942, the last operation being flown against Ostend during the night of 29 April, although some aircraft from operational training units were flown in the "1,000 Bomber" raid on Cologne on the night of 30 May 1942.

Coastal Commands association with the Whitley began in September 1939 when No. 58 Squadron was transferred to Boscombe Down to operate anti-submarine patrols over the English Channel. This lasted until February 1940 when the unit returned to Bomber Command, but during 1942 it took up patrol duties once again, flying over the Western Approaches from St Eval and Stornoway. Other units similarly occupied at that time included Nos. 51 and 77 Squadrons, the latter operating in the Bay of Biscay area.

Mk V Whitleys replaced the Avro Ansons of No. 502 Squadron at RAF Aldergrove in the autumn of1940 and a second Coastal Command Whitley unit, No. 612 Squadron, formed in May 1941. The Mk Vs were replaced by the ASV Mk II equipped Whitley VII, and an aircraft of No. 502 Squadron sank the type's first German submarine when it attacked U-206 in the Bay of Biscay on 30 November 1941.

Whitleys were also used at No. 1 Parachute Training School at Ringway, Manchester, and were adapted for use as glider tugs, becoming attached to No. 21 Glider Conversion Unit at Brize Norton for the training of tug pilots. The paratroop raid on the German radar site at Bruneval used Whitleys of No. 51 Squadron and the aircraft of special duty units at RAF Tempsford (Nos 138 and 161 Squadrons) flew numerous sorties, dropping agents into occupied territory and supplying Resistance groups with arms and equipment. Fifteen Whitley Vs were handed over to BOAC in May 1942 and stripped of armament but additional fuel tanks in the bomb bays, few regularly from Gibraltar to Malta carrying supplies for the beleaguered island. 

Specifications (Armstrong Whitworth A.W.38 Whitley B.Mk V)

Type: Five Seat Long Range Night Bomber

Accommodation/Crew: A crew of five consisting of a Pilot, Navigator/Bomb-aimer, Radio/Wireless Operator and 2 gunners.

Design: Armstrong Whitworth Design Team

Manufacturer: Sir W. G. Armstrong Whitworth Aircraft Limited based in Coventry. The company was formed in 1921. In 1935, the Hawker Siddeley Aircraft Company Limited was formed to amalgamate the interests of Hawker Aircraft Limited and the Armstrong Siddeley Development Company Limited which which the later company controlled Sir W. G. Armstrong Whitworth Aircraft Limited, Armstrong Siddeley Motors Limited and the A. V. Roe & Company Limited. The company was a pioneer in the development of all-metal aircraft, and it is due to their initiative that the use of high-tensile steel became prominent.

Powerplant: (B.Mk V) Two Rolls Royce Merlin X 12-cylinder liquid-cooled engines each rated at 1,075 hp (802 kW) for take-off and 1,130 hp (843 kW) at 5,250 ft (1525 m) at 3,000 rpm. (B.Mk IV) Two Rolls Royce Merlin IV 12-cylinder liquid-cooled engines rated at 1,030 hp (768 kW) for take-off and 990 hp (739 kW) at 12,250 ft (3740 m) driving Rotol constant-speed propellers.

Performance: Maximum speed 230 mph (370 km/h) at 16,400 ft (5000 m); cruising speed 210 mph (338 km/h) at 15,000 ft (4572 m); service ceiling 26,000 ft (7925 m) with a normal operational ceiling of between 17,600 - 21,000 ft (5400 - 6400 m). Initial climb rate of 800 feet (244 m) per minute; climb to 12,000 ft (3660 m) in 21 minutes.

Fuel Capacity: 837 Imperial gallons (1,005 US gallons or 3804.5 litres), plus provision for up to 132 Imperial gallons (160 US gallons or 600 litres) in auxiliary weapon-bay fuel tanks.

Range: With a 3,000 lbs (1361 kg) bombload, range was 1650 miles (2655 km) on internal fuel (standard) of 837 Imperial Gallons (4405 litres). Range could be increased to 1908 miles (3072 km) with the addition of extra tanks carried in the bombay that raised the total fuel carried to 969 Imperial Gallons (5096 litres). With a full 7,000 lbs (3175 kg) loadout range dropped to about 470 miles (756 km).

Weight: Empty 19,350 lbs (8777 kg) with a nominal take-off weight of 28,200 lbs (12789 kg) maximum take-off weight of 33,500 lbs (15195 kg).

Dimensions: Span 84 ft 0 in (25.60 m); length 70 ft 6 in (21.49 m); height 15 ft 0 in (4.57 m); wing area 1,137 sq ft (105.63 sq m); wing aspect ratio 6.21; mean chord 14 ft 4 in (4.37 m).

Defensive Armament: A (Nash and Thompson) F.N.16 nose turret was equipped with a single Vickers 'K' machine-gun using the 97 round drum-type magazine and four 7.7 mm (0.303 in) Browning machine guns in a powered (Nash and Thompson) tail turret using ammunition belts which supplied 1,000 rounds per gun.

Disposable Ordnance: Up to 7,373 lbs (3344 kg) of bombs could be carried in the two fuselage bays and 14 inner and outer wing bomb cells. Each fuselage bay was capable of carrying 2,000 lbs (907 kg) and each wing bomb cell could carry a single 250 lbs (113 kg) bomb. The two fuselage bays could be modified to carry a single 2,000 lbs (907 kg) armour-piercing bomb. Normal ordnance loadout however, was limited to the following:

• 2 x 500 lbs (227 kg) and 12 x 250 lbs (113 kg) bombs

• 16 x 250 lbs (113 kg) bombs

• 4 x 420 lbs (191 kg) depth charges (GR.Mk VII)

• 2 x 420 lbs (191 kg) depth charges and 4 x 250 lbs (113 kg) anti-shipping bombs (GR.Mk VII)

The normal bombload was 4,000 lbs (1814 kg) made up of 2 x 500 lbs (227 kg) and 12 x 250 lbs (113 kg) bombs carried in the fuselage with extra fuel in the bomb cells in the wings. One of the few instances where the Whitley carried its maximum bombload was the attacks against German invasion barges on the French coast.

Variants: A.W.38 Whitley, Whitley B.Mk I, Whitley B.Mk II, Whitley B.Mk III, Whitley B.Mk IV, Whitley B.Mk IVA, Whitley B.Mk V, Whitley C.Mk V (frieghter), Whitley Mk VI (never built), Whitley GR.Mk VII (naval conversion), Whitley GR.Mk VII (ASW).

Equipment/Avionics: Standard communication and navigation equipment. The Mk.VIIc or Mk.IXc bombsight was also standard. After 1942 most surviving aircraft were fitted with glider towing equipment. Two cannisters could be fitted under the wings for leaflet dropping raids. (GR.Mk VII) ASV Mk II Air-to-Surface Radar.

History: First flight (prototype) 17 March 1936; first delivery (Mk I) January 1937; first flight (Mk V) December 1938; first delivery (Mk V) August 1939; production terminated in June 1943; final operational sortie 29 April 1942 against Ostend.

Operators: United Kingdom (RAF, BOAC).