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ee te pe - 3 - controller's knowledge of the Learjet's position could only have been based on the route for which he cleared the aircraft -- and the pilot's Progress reports. rere sae: In commenting on the flightcrew's "failure to recognize their proximity to high terrain,’ the Board pointed out that "proper exercise of responsibility" during descents and takeoffs can only be based on knowledge of terrain hazards. However, in this case, the pilot was familiar with the Palm Springs airport and its surrounding terrain. Thus, the Board said, it could not explain the Learjet pilot's continuance of a heading that, if maintained would aim his aircraft toward the highest mountain in the area and at an altitude more than 2,000 feet "below" the f highest terrain. The Board did note, however, that several aircraft accident investigations have indicated that, since the advent of radar control and its capability to vector traffic, there has been "a derogation of pilot knowledge of terrain over which they fly.’ toe, ves oe, In commenting on the controller'sfailure to detect the aircraft's deviation from the route contained in the air traffic control clearance the Board noted that at 1656:55 the Learjet crew reported they were approaching 9,000 feet and asked if they were cleared ''via'' the 051 degree radial to Twenty-nine Palms. The controller replied in the affirmative and added "I had a change of route there. Maintain 9,000, I'll keep you advised. '' The crew then asked if they were to maintain 9,000 feet ''straight ahead, right?" and the controller said they were. ‘The controlier’s use of "I had a change of route there’ appearegi to con- firm their belief that their present heading (approximately 300 degrees) was to be maintained until they received clearance to "turn back" toward Twenty-nine Palms and "intercept the 051 radial. On the other hand the controller stated that when he said he would "keep them advised" he was only considering the "altitude restriction" of 9,000 feet. Moreover, since the controller was convinced the flight a was already established outbound on the 051 radial course the query © ff ¥ about flying "straight ahead" merely meant "continued flight" toward co, Twenty-nine Palms on the 051 radial, The Board noted that during this _ exchange the flightcrew did not apprise the controller of one vital piece C4 of information -- their heading, or direction of flight. Subsequently, at 1658:30 the crew reported they were about 14 miles from Palm Springs and maintaining 9,000 feet on a heading of "three one zero (310 degrees)" and asked "what's our clearance from here." This was the only transmission from the flightcrew that gave the controller "heading information” the Board said, and a chance to make a reasonably accurate estimate of the aircraft's position. However, the Board said, the controller did not recognize the significance of the 310 degree heading or it did not register with sufficient impact to overturn his conviction Bote eae