On September 21, 1956, Grumman test pilot Thomas Ettridge took off in an F11F "Tiger" BuNo 138620 fighter jet for test firing at a range over the Atlantic Ocean.
The F11F was one of the last fighters to use cannons as the main weapon. The shell casings were thrown out through special ports and sometimes damaged the fuselage and stabilizers. To avoid this, the design of the sleeves was changed. Ettridge had to test the operation of the new system when firing at supersonic speeds.
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Twenty miles off the coast, Ettridge began a gentle dive from a height of 6 kilometers. Having dropped to four kilometers, he fired a short four-second burst of his four 20-mm cannons, firing about seventy rounds, then turned on the afterburner, shifted the plane to a steeper dive and at an altitude of 2 kilometers fired the remaining shells. At this moment, the plane began to shake, and the cockpit canopy was covered with a network of cracks.
Attridge decided that his plane had collided with a bird, reported the incident to the dispatcher, noting that he was observing a large hole in the right air intake, slowed down and directed the plane towards Grumman AFB near Calverton, New York. However, the real problems were just beginning - the aircraft engine was damaged, the thrust dropped to 78 percent of the maximum. All attempts to increase engine speed resulted in severe vibration.
It became clear that the plane would not be able to reach the base. In the end, the engine finally failed, and Ettridge, not reaching the runway for only a kilometer, landed the plane on its belly in the forest, cutting a hundred-meter clearing in the thickets. From the impact, the plane collapsed and caught fire, Ettridge, with a broken leg and a compression fracture of the spine, miraculously managed to get out of the seat belts and crawl to a safe distance.
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The investigation into the incident yielded striking results - Ettridge's plane was hit by its own first-order shells. If the plane continued to descend at the original angle, it would have flown over the trajectory of the shells, but Ettridge increased the descent angle and speed, the speed of the shells, on the contrary, decreased, and after a while the plane and the shells met at one point in space.
A shell recovered from Ettridge's F11F "Tiger" engine.
One shell hit the cockpit canopy, the second hit the air intake and violated the guide device, the debris of which hit the engine, the third shell pierced the nose cone. Fortunately for Ettridge, the shells were training, with an inert warhead. If he had shot with combatants, the plane would have been destroyed in the air.
In the aftermath of the incident, the US Navy advised pilots to turn aside or at least reduce the dive angle of the aircraft after firing the cannons, although it was generally accepted that Attridge's case was too improbable to happen again.
Ettridge recovered quite quickly and continued to work as a test pilot for Grumman, and later participated in the work on the lunar module of the Apollo program.