In 1958 Hughes proposed their Model 269 to the US Army as a replacement for OH-13 Sioux and OH-23 Raven light observation helicopters. Although it was not found adequate for combat missions, some 792 were obtained as trainers, remaining in service as the Army's primary teaching helicopter until supplanted by the UH-1 in 1988. Some 60,000 US Army pilots are said to have received their training on the TH-55