As a result of this problem, TWA blocked the Flaps 40 setting. Flaps 40 provided so much drag that a high sink rate could develop and it may be difficult to stop once it begins.
To remedy this, the Flaps 40 setting was physically blocked on all TWA 727s. Flaps 30 was the most we were authorized to use, and the most we could select due to the physical block on the flap lever. Flaps 30 does not offer nearly as much drag, making the high-sink situation less of an issue.