The XBT-1 used a layout related to the A-17, with a 42-foot wingspan, partially retractable landing gear and a rear observer-gunner position. Its split trailing-edge flaps had to perform different jobs during landing and diving. A double concentric-cylinder hydraulic mechanism allowed the lower flap to extend alone for takeoff and landing, or both upper and lower surfaces to open for a dive. Careful synchronization prevented flap deployment from disturbing longitudinal trim. Heinemann adapted the principles of a Scott Russell linkage, and the arrangement gave relatively little trouble during the first year of development.
Notable Point · 2:19:26-2:20:30
Making the XBT-1's flaps serve as landing aids and dive brakes
Separate landing and dive-brake modes required synchronized flap movement so deployment would not upset the XBT-1's trim.