Monospar ST.1 / ST.2
Monospar aircraft utilised a single-spar wing designed around a duraluminum warren girder, braced with pyramidal tie rods to take the torsional loads. Devised by H Steiger, the principle was first publicly exhibited in an experimental wing (known as the ST-1) shown at the Olympia Aero Show in July 1929. A larger wing (ST-2) was subsequently flown on Fokker EVIIB/3m J7986. Official tests demonstrated the strength of the system.