NTSB Identification: LAX06LA235.
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Accident occurred Tuesday, July 11, 2006 in Hesperia, CA
Probable Cause Approval Date: 06/27/2007
Aircraft: Alfred Long-EZ, registration: N1014A
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The airplane collided with a fence while on final approach to the destination airport. While aligned on the final approach leg of the traffic pattern, the airplane encountered a downdraft, and the pilot attempted to increase the engine power and recover from the sudden descent. The airplane collided with a fence that was at the approach end of the runway then slid about 100 yards down the pavement before coming to rest off the right side of the runway surface. The pilot reported no preimpact mechanical malfunctions or failures with the airframe or engine. The Airport/Facility Directory, Southwest U. S., indicated that the runway was 3,910 feet long and 50 feet wide, with a displaced threshold of 500 feet. The runway had an upsloping gradient, which was not noted in the directory. A Federal Aviation Administration publication states that a "narrower-than-usual runway can create the illusion that the aircraft is at a higher altitude than it actually is." It further states that a pilot who fails to recognize this illusion will "fly a lower approach, with the risk of striking objects along the approach path or landing short." The publication also addresses runway and terrain slopes illusions, stating that an, "upsloping runway, upsloping terrain, or both, can create the illusion that the aircraft is at a higher altitude than it actually is." Again, it warns that pilots who fail to recognize this illusion will fly a lower approach.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot's failure to maintain the proper glide path on final approach as a result of the visual illusions created by a narrow, upsloping runway.

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