An American Airlines passenger jet and an Army helicopter collided on Jan. 29 as the plane prepared to land at Washington, D.

Helicopters in the area where the crash occurred are restricted to flying at an elevation of no more than 200 feet. Helicopter pilots typically fly and navigate using barometric altitude ...

Helicopter pilots typically rely on barometric readings while flying, but the helicopter’s black box captures its radio altitude. The radio altitude at the time of the impact put the Black Hawk ...