Frank Whittle - Development of The Turbojet Engine

Development of The Turbojet Engine

Whittle continued working on the motorjet principle after his thesis work but eventually abandoned it when further calculations showed it would weigh as much as a conventional engine of the same thrust. Pondering the problem he thought: "Why not substitute a turbine for the piston engine?" Instead of using a piston engine to provide the compressed air for the burner, a turbine could be used to extract some power from the exhaust and drive a similar compressor to those used for superchargers. The remaining exhaust thrust would power the aircraft.

On 27 August 1928 Pilot Officer Whittle joined No. 111 Squadron, Hornchurch, flying Siskin IIIs. His continuing reputation for low flying and aerobatics provoked a public complaint that almost led to his being court-martialled. Within a year he was posted to Central Flying School, Wittering, for a flying instructor's course. He became a popular and gifted instructor, and was selected as one of the entrants in a competition to select a team to perform the "crazy flying" routine in the 1930 Royal Air Force Air Display at RAF Hendon. He destroyed two aircraft in accidents during rehearsals but remained unscathed on both occasions. After the second incident an enraged Flight Lieutenant Harold W. Raeburn said furiously, "Why don't you take all my bloody aeroplanes, make a heap of them in the middle of the aerodrome and set fire to them – it's quicker!"

Whittle showed his engine concept around the base, where it attracted the attention of Flying Officer Pat Johnson, formerly a patent examiner. Johnson, in turn, took the concept to the commanding officer of the base. This set in motion a chain of events that almost led to the engines being produced much sooner than actually occurred.

Earlier, in July 1926, A. A. Griffith had published a paper on compressors and turbines, which he had been studying at the Royal Aircraft Establishment (RAE). He showed that such designs up to this point had been flying "stalled", and that by giving the compressor blades an aerofoil-shaped cross-section their efficiency could be dramatically improved. The paper went on to describe how the increased efficiency of these sorts of compressors and turbines would allow a jet engine to be produced, although he felt the idea was impractical, and instead suggested using the power as a turboprop. At the time most superchargers used a centrifugal compressor, so there was limited interest in the paper.

Encouraged by his Commanding Officer, in late 1929 Whittle sent his concept to the Air Ministry to see if it would be of any interest to them. With little knowledge of the topic they turned to the only other person who had written on the subject and passed the paper on to Griffith. Griffith appears to have been convinced that Whittle's "simple" design could never achieve the sort of efficiencies needed for a practical engine. After pointing out an error in one of Whittle's calculations, he went on to comment that the centrifugal design would be too large for aircraft use and that using the jet directly for power would be rather inefficient. The RAF returned his comment to Whittle, referring to the design as being "impracticable".

Pat Johnson remained convinced of the validity of the idea, and had Whittle patent the idea in January 1930. Since the RAF was not interested in the concept they did not declare it secret, meaning that Whittle was able to retain the rights to the idea, which would have otherwise been their property. Johnson arranged a meeting with British Thomson-Houston (BTH), whose chief turbine engineer seemed to agree with the basic idea. However, BTH did not want to spend the ₤60,000 it would cost to develop it, and this potential brush with early success went no further.

In January 1930, Whittle was promoted to Flying Officer. In Coventry, on 24 May 1930, Whittle married his fiancée, Dorothy Mary Lee, with whom he later had two sons, David and Ian. Then, in 1931, he was posted to the Marine Aircraft Experimental Establishment at Felixstowe as an armament officer and test pilot of seaplanes, where he continued to publicize his idea. This posting came as a surprise for he had never previously flown a seaplane, but he nevertheless increased his reputation as a pilot by flying some 20 different types of floatplanes, flying boats, and amphibians. Every officer with a permanent commission was expected to take a specialist course, and as a result Whittle attended the Officers’ Engineering Course at RAF Henlow, Bedfordshire in 1932. He obtained an aggregate of 98% in all subjects in his exams, completing the course in 18 months instead of the more normal two years.

His performance in the course was so exceptional that in 1934 he was permitted to take a two-year engineering course as a member of Peterhouse, the oldest college of Cambridge University, graduating in 1936 with a First in the Mechanical Sciences Tripos. In February 1934, he had been promoted to the rank of Flight Lieutenant.