Armstrong Whitworth AW.38 Whitley
Whitley VAir Ministry Specification B.3/34 called for a bomber that could carry a bomb load of 2000 lbs for 1250 miles at a height of 15,000 feet at a maximum speed of 225 mph. As the RAF’s existing hangar doors were little more than 100 feet wide, putting a firm limit on the aircraft’s wingspan which was only 84 feet but with a wide chord and thick wing section. There were four contenders to build to specification B.3/34 with Armstrong Whitworth becoming the chosen company. The A.W.38 (which was later named Whitley after the airfield and works near Coventry) contained design features that had previously been tested by the company in the A.W.23 transport/bomber. The new light alloy wing construction consisting of a basic torsion box of web corrugated vertically, and spanwise gave it strength aided by an internal bracing of steel struts.
The prototype Whitley, K4856, was first flown on March 17, 1936. With increasing urgency for the RAF to re-equip and after an original order for 80 aircraft, a second order for 240 Whitleys was signed on 13 May 1936, two months after the prototype’s first flight.
The second prototype and 34 Mk I production aircraft which followed were all powered by two 592.5kW Armstrong Siddeley Tiger IX radial engines. The first production Whitley, K7183, was delivered in the early months of 1937, with the second aircraft, K7184, being flown direct on March 9 from Baginton to No 10 Squadron, which was then equipped with Handley Page Heyfords.
The original design had no wing flaps but later flaps - with a maximum deflection of 60o - were incorporated.
With a wing area of over 1,200 square feet and a high angle of attack, the type had superb lift, but the original power plants - 795 hp Armstrong Siddeley Tiger IX air cooled radials - left the early Marks of Whitley under-powered. Half -way through the first production batch, after 34 aircraft had been completed, the Whitley 1 was superseded by the Mk II version in which the 795 hp Armstrong Siddeley Tiger IX engines were replaced by 845 hp Tiger VIII engines incorporating a two-speed supercharger.
The Mk III would appear shortly after the initial batch, introducing a Nash & Thompson ventral gun position that was retractable.
The need for still more performance and greater reliability resulted in a decision to adopt 1,745 hp Rolls-Royce Merlin Xs for the Mk IV. The first Merlin powered example flew on February 11, 1938. A subvariant of the Mk IV would appear with a newly-configured powered tail turret housing quad 7.7mm machine guns.
The first Mark V came off the line on 28 August 1939 and production of this Mark lasted four years and accounted for 90 percent of the total number of type built; over 2,000 in all.
At the outbreak of the Second World War almost all of the Whitley Is and IIs had been withdrawn from operational status as heavy bombers, although seven squadrons (Nos 10, 51, 58, 77, 78, 97 and 102) were equipped with the Mk IIIs, IVs or Vs.
After the introduction of four-engined bombers such as the Halifax, Stirling and Lancaster during 1940-41 Whitleys continued bombing operations over Germany until April 1942 - the last raid taking place on April 29-30 to Ostend.
At the end of the war the type was still in service for training and other miscellaneous duties.
The Whitley was responsible for the first bombing raid on Germany, in May 1940; the first bombing raid on Italy, in June 1940; and the first paratroop operation over Southern Italy, in February 1941.
The last Whitley built, LA951, was retained by the Armstrong Whitworth company on its completion in 1943. It was used for general test and experimental flying, one of its main tasks being to act as a tug for the A.W.52G glider. Four years later, in March 1949, LA951 was withdrawn from service and dismantled.