His appointment in 1931 as chief test pilot at Westland Aircraft began a 22-year labour of love: he made the initial test flights on all the subsequent Westland types, notably the extraordinary pterodactyl series of tail-less monoplanes designed by Captain Geoffrey Hill, the Houston- Westland PV3 which flew over Everest in April 1933 and the Lysander army co- operation aircraft. A disastrous in-flight structural failure of the P7 monoplane allowed Penrose the dubious privilege of becoming the first pilot to bale out of an enclosed-cockpit aeroplane, though he was forced to make his exit via a side window when suction forces jammed the sliding roof.
Born in Hereford in 1904, when man was making his first faltering essays into the skies, Penrose became enamoured with flight at the age of five, after his father showed him a picture of the monoplane in which Bleriot had just flown the Channel. Two years later, the infant was lifted aloft - albeit only a few feet - beneath a Cody-type kite in his local park.
Several encounters with flying machines in the pre-war years fired a youthful ambition to become a pilot, but not until the end of the First World War did Penrose enjoy his first flight, in a war-surplus Avro 504K in which the pioneer aviator Alan Cobham was giving joyrides from a field at Reading.
Following a four-year aeronautical course at the Northampton Engineering College of London University, Penrose joined Westland Aircraft at Yeovil, Somerset, in September 1926. By the New Year he was overseeing the construction of the Wigeon III light monoplane, and was the first to fly in it as a passenger after its maiden flight.
Obtaining a commission in the Reserve of Air Force Officers (RAFO) in 1927, Penrose learnt to fly in a Bristol Type 73 at the Bristol Flying School, soloing after six hours dual and moving on to a Jupiter-engined advance trainer variant of the First World War Bristol Fighter. He returned to Westland gazetted as Pilot Officer RAFO, obtained his private pilot's A-Licence the same year and made his first flights for Westland in the Wigeon.
In March 1928 he was authorised to fly a number of the company's new machines - much to his surprise, as he had fewer than 100 hours' total piloting experience. He was also acting as a test-flight observer, and later that year was made manager of Westland's new civil aircraft department, overseeing the development of the W.IV and Wessex trimotors. In October he qualified for his commercial pilot's B-Licence.
In 1930 Penrose began flying the Wapiti general-purpose military two- seater and the following year he was entrusted with taking a Variant to South America and demonstrating it in both landplane and seaplane forms.
Shortly after his return, in May 1931, Captain Louis Paget, Westland's pilot in charge, suffered serious injuries in a crash, and Penrose was asked to fulfil his duties - with no increase in wages. After all, he later recalled: "It just seemed wonderful that Westland was letting me have extensive free flying which I would otherwise have been unable to afford." With the news that Paget was permanently crippled, Penrose was appointed chief test pilot.
Amid his busy professional life, Penrose also found time to build and fly his self-designed sailplane, Pegasus, in 1935.
With the outbreak of the Second World War, production testing intensified and the Lysander, with its exceptional short-field capabilities, became renowned for its role in flying Special Operations Executive agents in and out of French fields in the dead of night. The new Whirlwind twin- engine fighter, first flown by Penrose in October 1938, proved a disappointment, and the extraordinary tandem-wing version of the Lysander, which he looped on its maiden flight in July 1944, was a one-off experiment.
Penrose also carried out the production tests of other manufacturers' aircraft build under licence by his company; Spitfires, Seafires, Barracudas and Lend-Lease Curtiss Mohawk and Tomahawk fighters allocated to Westland for assembly and test-flying. The company's last wartime design, the Welkin high-altitude fighter, proved a troublesome mount for Penrose and his fellow pilots.
By far the most notorious aeroplane flown by Penrose, however, was the turbo-prop powered Wyvern naval fighter, which suffered from being a new air frame married to new and under-developed engines. First flown in December 1946, this big single-seater underwent protracted development during which three test pilots lost their lives. Only quick and instinctive reactions kept Penrose from being numbered among the victims when the Wyvern he was returning to Yeovil suffered a failed aileron linkage and turned over on its back.
After six years of Wyvern flying, Penrose was appointed Sales Manager of Westland Aircraft Ltd, responsible for the Westland, Bristol and Saunders-Roe helicopter group. By then he had amassed some 5,000 hours on no fewer than 250 different types of aircraft ranging from rotorcraft to modern jets. He continued to fly for pleasure (he would probably have said that flying was always a pleasure), acquiring a diminutive Currie Wot byplane after his retirement in 1967 and sampling other types whenever the opportunity arose.
Apart from his aeronautical talents, Penrose was a keen ornithologist, a naval architect (he designed 36 boats and yachts), and designed the house at Nether Compton, Dorset, in which he lived for 50 years. He also wrote a number of books, being gifted with a fluidity and elegant prose style rare in aviation writers. His outstanding autobiographical works were I Flew with the Birds (1949), No Echo in the Sky (1958), Airymouse (1967), Cloud Cuckooland (1981), and Adventure with Fate (1984). Other titles were Architect of Wings (1985), a biography of the Avro designer Roy Chadwick, Wings across the World (1980), a history of British Airways, and an impressive five-volume history of British aviation.
Penrose was made a Fellow of the Royal Aeronautical Society in 1936 and in 1993, when his tally had risen to 5,500 hours on 309 types, he was presented with Honorary Fellowship of the US Society of Experimental Test Pilots.
Harald James Penrose, pilot: born 12 April 1904; OBE 1946; married 1929 Norn Bailey (died 1986; one son, one daughter); died 31 August 1996.