Bristol Type 92

Bristol Aeroplane Company

Industry	Aerospace
Founded	1910 in United Kingdom
Founder	Sir George White
Headquarters	United Kingdom
Products	Aircraft

Template:Infobox aircraft The Bristol Type 92, occasionally referred to as the Laboratory biplane, was an experimental aircraft constructed by the Bristol Aeroplane Company to investigate the discrepancies between wind tunnel cowling models and their full-scale counterparts for radial engines. It was essentially a larger version of a wind tunnel model aircraft, with only one unit produced and flown during the mid-1920s.

Development

During the 1919 development phase of the Bristol Badger, chief designer Frank Barnwell observed inconsistencies between wind tunnel test results and actual full-size aircraft performance, notably the inability to foresee the Badger’s lateral instability. To explore this, Barnwell created the Badger X, which combined standard Badger wings with a simplified fuselage designed to replicate a scaled-up wind tunnel model for direct comparison. The Badger later served as a platform for testing Bristol’s Bristol Jupiter radial engine equipped with various cowling designs. However, extrapolating aerodynamic and cooling data from wind tunnel cowling tests to full-sized aircraft remained challenging, making it difficult to predict cooling efficiency in cowlings that were aerodynamically streamlined. These cooling challenges were encountered not only with the Badger but also with subsequent Jupiter-powered Bristol aircraft such as the Bristol Bullfinch and Bristol Ten-seater.

In response, Barnwell designed a full-scale aircraft embodying the simplicity typical of wind tunnel models, capable of accommodating multiple cowling types over the Jupiter engine; this design became the Type 92. It featured a two-bay biplane configuration with equal-span, square-tipped wings that lacked both stagger and sweep. The wings and tail assembly were constructed from fabric-covered steel strips and tubing, forming straightforward rectangular shapes. The Type 92’s distinctive look partly resulted from efforts to reduce aerodynamic interference between wings and fuselage. To achieve this, the vertical gap between the wings was notably large—measuring 9 ft (2.7 m) or approximately one quarter of the wingspan. The undercarriage consisted of a wide-track, single-axle setup positioned beneath the inner interplane struts.

The fuselage was equally simple in design, consisting structurally of a box girder covered with plywood approximately 2 ft (0.61 m) square running from the nose to just beyond the second cockpit, where it tapered only in plan view down to an edge at the tail. Two streamlined pylons connected the fuselage to the wings above and below, positioning it midway between wing planes. For aerodynamic testing purposes, the untapered section of the fuselage could be enclosed within circular fairings of varying diameters; although five sizes were initially planned, budget constraints limited flight tests to only the smallest (3 ft (0.91 m)) and largest (5 ft (1.5 m)) fairings. Given that the Jupiter engine’s diameter was roughly 4 ft (1.2 m) , its cylinder heads protruded noticeably when using the smaller fairing but were enclosed by the larger one.

Operational history

Equipped with a Jupiter V engine, the Type 92 made its maiden flight from Filton on 13 November 1925. Although it exhibited awkward handling characteristics in flight and was neither officially registered nor flown extensively beyond Filton, it remained operational for over two years, primarily utilizing the 3 ft (0.91 m) cowling. In 1928, a larger cowling was installed; however, shortly afterward, the undercarriage suffered damage during a hard landing, and the Type 92 was subsequently grounded permanently.

By the close of the 1920s, advances in radial engine cowling design were becoming more refined, although the exact influence of the Type 92 on these developments remains uncertain. The introduction of the Townend ring in 1929 enhanced airflow while maintaining adequate cooling through its open design. Concurrently, between 1928 and 1929, NACA conducted and implemented successful experiments on tightly cowled engines within the 20 ft (6.1 m) diameter Propeller Research Tunnel (PRT). The PRT's capability to evaluate full-scale cowlings under controlled laboratory conditions eliminated the need for airborne testing and circumvented the complexities associated with extrapolating low Reynolds number model data to realistic operational parameters.