TH-55 OsageTH 55 Osage helicopter model. The TH 55A Osage is a revolutionary single three blade rotor helicopter that transformed military aviation training. Developed from the Hughes Model 269, this lightweight two seater became the U. S. Army's premier training aircraft in 1965, supplanting the Hiller H 23B. With approximately 800 units delivered by 1969, this exceptional aircraft served faithfully until 1988. Its impressive legacy includes training countless