sentences:  The airframe was advanced in its use of the new Clark Y airfoil thick-section aerofoil and a welded fuselage framework of chrome-molybdenum steel tubing.A departure from the all-wood structures found in other trainers, the structure proved sturdy and dependable.It was offered to the USAAS as a replacement for the Curtiss JN-4D trainer, with a choice of Le Rhone or Clerget rotary piston engines.