The stresses from the opening of the drogue parachutes (3 for the A version, 4 for the heavier B/C variants) were particularly severe at the speed anticipated for the BAC TSR-2, the requirement stating a dropping speed of from Mach number M 0.75 to M 1.15, at a height of 50 feet for TSR-2; and M 0.75 to M 0.95 for the Blackburn Buccaneer.