Bristol Type 138

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Type 138 High Altitude Monoplane

The Bristol Type 138A was a British high‑altitude research aircraft from the 1930s, built by the Bristol Aeroplane Company and designed by Frank Barnwell. It was a single‑engine, low‑wing monoplane with a fixed undercarriage to save weight and a two‑stage supercharged Pegasus engine. The aircraft carried a pressurized cockpit and a special oxygen system, with research support from the Royal Aircraft Establishment (RAE) and the National Physical Laboratory.

First flown on 11 May 1936, the 138A was part of a push to set new altitude records. Early flights used a standard Pegasus engine before the final high‑altitude setup was installed. The project helped Bristol compete in a field where nations sought to break records for prestige and technological progress.

Key milestones:
- 28 September 1936: Squadron Leader F.R.D. Swain flew to about 51,000 ft (15,600 m); the record was recognized at 49,967 ft (15,230 m) due to oxygen issues.
- 1936–1937: Several tests and small fixes pushed the altitude past 50,000 ft.
- 30 June 1937: Flight Lieutenant M.J. Adam reached 53,937 ft (16,440 m) in 2 hours 15 minutes, a new record, despite a cracked canopy during the flight.

A second airplane, Type 138B, was ordered in 1935 as a two‑seater with a Rolls‑Royce Kestrel S engine. It was incomplete and never flown; it was later used as a ground training aircraft.

Overall, the Type 138 program produced valuable data on high‑altitude flight and pressurization, helping advance the science of aviation at extreme altitudes. Only one Type 138A was completed, with the 138B airframe never flown.