On August 4, 1955, the Convair CV-240-0 crashed while attempting an emergency landing in Fort Leonard Wood, Missouri, killing all 30 passengers and crew.

It was powered by two Pratt and Whitney R-2800-83AM4A engines that had logged 13,346 and 12,875 flight hours, driving each a Hamilton Standard propeller.

Afterward, ground crew in St. Louis, and two other nearby aircraft, including one near Springfield, heard the pilot of Flight 476 announce that their No.

However, the dense forest prevented rescue equipment from reaching the aircraft until army engineers bulldozed a road to it.

A closer examination at the National Bureau of Standards lab found that eight of the cylinder's hold-down studs had failed after previously being installed in another engine.

Before the crash, American Airlines required that cylinders with more than two broken studs be scrapped or returned to their manufacturer.

[1][2] After the accident, American Airlines required all cylinders with faulty studs to be mutilated to prevent employees from returning them to service without proper repair.