2000 pound Bomb/Prop Clearance Test

After approximately a month with the company, the new pilot [Bob Rahn] in the Douglas Flight Test team was offered the simple test of demonstrating the design criteria of the bomb ejector which was to release a 2,000 pound bomb in a 90 degree dive and provide twelve inches clearance from the propeller. One knew when you had reached the "big time" because when a test was considered somewhat hazardous, the company's only "Tin Hat" was issued, but it was not hazardous enough to warrant the services of a chase pilot. It is now believed that this tin crash helmet would have only transferred the dent of the helmet into the pilot's skull.

The test seemed simple enough--just hold the plane steady in a 90 degree dive for several seconds after bomb release so that a wing-mounted camera could photograph the bomb/propeller clearance. The bomb release was evident by a deep thud, but approximately four seconds later all "hell broke loose." The bomb had hit the prop, apparently knocking off a blade, and with the anti-symmetric loading, the engine was literally torn from its mounts. This pilot, before the days of ejection seats, had always studied the best way to evacuate a distressed vehicle. However, with the prop/engine gone, the resultant aft CG put the airplane in a tumbling mode, and I just "popped" out upon release of the safety belt. The buffet and tumbling was so severe that the hand mike could not be located to inform the Flight Office of the impending bailout, so a search/rescue mission was not immediately initiated. Sunset had just occurred when the pilot was located eight miles off shore by a P82 (double Mustang) production pilot.

Since the externally-mounted camera was not available because the plane was not recovered due to its being at the bottom of the ocean, no plausible reason for the collision was forthcoming. Several conjectures were: a) malfunction of the ejector, b) wrong size cartridge for a 2,000 pound bomb, or c) a bad cartridge. After days of guesswork, the question of dive angle was discussed. "Are you sure you were in a 90 degree dive?" Since the attitude gyro was not readable closer than ±l degree, the reply was: "It was not less than 90 deqrees." After determining from the interrogation that it was approximatelv four seconds from release to impact, the engineers determined that a 91 degree dive held after release would result in the bomb "catching up" and striking the aircraft in four seconds.

You have all heard of planes being shot down by their own missiles, of guns shooting out the airplanes props, or gun cases causing flame-outs, but this has the dubious distinction of being the first time (and probably the only tire) that a plane was bombed out of the sky by its own bomb. The Navy subsequently limited dive-bombing attacks to 80 degrees, and cautioned that pull-outs should be initiated immediately after bomb release.

Bob Rahn's book, Tempting Fate: An Experimental Test Pilot's Story (co-authored by Zip Rausa) covers this and many more incidents involved with the testing aircraft for Douglas Aircraft Company. It is currently in print and available.

Bob Rahn was a new test pilot for Douglas Aircraft Company in the mid 1940s when the Skyraider prototype was being evaluated. He was responsible for the structural and aerodynamic demonstration testing of the aircraft. He has been a longtime member of the A-1 Skyraider Association and was one of the first men inducted into the Test Pilot Hall of Fame. Bob lost his fight with ALS (Lou Gherig's Disease) and died of respiratory failure on May 21, 1998. God bless you, Bob.

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