Post by Diarist on Aug 12, 2016 7:46:30 GMT 1
The prototype Boeing Model 299 crashed while its performance with two engines inoperative on one wing was being demonstrated to representatives of the USAAC. When the engines were shut down, the pilot moved the rudder to maximum deflection to counter the resulting yaw. The aircraft then experienced rudder lock, where the control loads prevented the rudder from being re-centred. As a result, the 299 went into a spin and crashed killing all on board. Subsequent wind tunnel testing showed that the addition of an extended dorsal fin ahead of and attached to the vertical tail prevented rudder lock. This design change was immediately incorporated in the production aircraft causing a significant delay.