The Stemal III was a test-bed for his ideas for extending the speed range of aircraft using variable camber wings, which he had begun to develop at the beginning of World War I whilst studying the Gustave Eiffel wind tunnel results[1] on the lift generated by cambered aerofoil sections.
The first full scale wing panel for structural and operational tests was built in 1921 at Bydgoszcz, in the workshops of the military flying school there.
The subsequent trials yielded promising results, with take-off and landing distances halved, rate of climb increased by 33% and service ceiling by 20%.
[2] These tests generated some interest, particularly at the Technical Services of Aerodynamics (S.T.Aè) in Paris in 1924, leading to studies by Hanriot of a similar wing.
In 1925 the Warsaw Technical University made air-tunnel measurements on a wing with a greater camber range over its full span, controlled with a simplified mechanism.