Helmuth John Stieger was born in Zurich in 1902, and educated at the Swiss Federal Polytechnic, and then at the Imperial College of Science in London.

306,220 was that the wing needed only one spar with torsion loads resisted by an efficient system of strong compression struts, with triangulated bracing in the form of thin wires.

[2] The first production design was the Monospar ST-4, a twin-engined low-wing monoplane with a fixed tailwheel landing gear and folding wings for ground storage.

The Monospar ST-6 was only the second British aircraft to fly with retractable landing gear (the first, the Airspeed Courier, was flown a few weeks earlier).

GAL then produced a developed version, the Monospar ST-10, externally the same but powered by two Pobjoy Niagara engines, an improved fuel system, and aerodynamic refinements.

[1][5][6] A production batch of ten Monospar ST-12 aircraft was based on the ST-11, but with de Havilland Gipsy Major engines and fixed landing gear.

A supportive web, comprising a plain duralumin plate with triangular holes stamped out for lightness, used a series of lattice bars that functioned as braces between top and bottom flanges.

[9] These spar flanges were built up of strips and consisted of angle sections that were riveted to the web with reinforcing cover plates added on the outside.

[13] The four corner booms of this beam were of built-up D-section and were joined by an outer cover of stamped duralumin sheeting that formed lattices, akin to the main wing spar web.

[13] The shape of the fuselage was obtained via a series of hoops of trough-section duralumin and stringers (both fore and aft) of similar section.

Each vertical leg, which incorporated a Vickers-supplied oleo shock absorber, were connected to a sturdy point within the engine mounting.

[1][17] On 6 September 1935, a Monospar ST-12 operated by Australian Transcontinental Airways suffered engine failure, and made an emergency landing on Woodgreen Station in the Northern Territory.

Reports vary slightly,[20] but the plane was said to be carrying the pilot J. Maher, with two passengers, Renfrey and Maloney, and a young crocodile that was being transported to Adelaide.

[b] Renfrey walked for two days towards Ryan's Well, a watering hole on the Overland Telegraph Line around 40 mi (64 km), to seek assistance.

In the meantime, Don Thomas from Alice Springs drove to Woodgreen to pick up Purvis Sr and two "blackfellows", one of whom managed to track down the plane based on the description of the location given by Renfrey.