NTSB Identification: SEA08LA128
14 CFR Part 91: General Aviation
Accident occurred Saturday, May 10, 2008 in Modesto, CA
Probable Cause Approval Date: 12/24/2008
Aircraft: Moravan Zlin 50LX, registration: N6660K
Injuries: 1 Serious.

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 pilot was performing in an airshow that was conducted at a controlled airport serviced by airlines. Two Federal Aviation Administration (FAA) inspectors acting as the FAA monitors, witnessed the accident. Performances, as a rule, are timed so that they do not conflict with inbound and landing airline traffic. If there is a timing conflict, normally the show is temporarily stopped so as not to delay the airline traffic. During the accident pilot's performance, the pilot was transmitting directly to the crowd, as well as communicating with an on ground safety observer, the airshow waiver holder, and an air traffic control tower controller. The air traffic control tower controller advised the pilot to stop the performance due to an inbound arriving airliner and make a right base entry for landing. The pilot had completed a normal sequence and then requested to make one more pass and the tower controller approved the request. The pilot then added the additional maneuver as his final routine before exiting the performance box. The FAA inspector indicated that during the added maneuver, the right wing impacted the ground. The pilot stated that during the airshow briefing, he had requested a sterile frequency for maintaining communication with airshow and ground support staff, which he indicated was standard operating procedures at other airshows. The air traffic control tower personnel elected to have the airshow pilots monitoring and communicating on the same frequency as the tower controllers. The pilot stated that during the flight, he was interrupted numerous times by tower personnel and incoming aircraft, which prevented his ground safety observer from communicating with him and not only added to his workload, but affected his concentration during the maneuver.

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

The pilot failed to maintain clearance from terrain during a low-altitude maneuver at an airshow. Contributing to the accident was the task overload in the increased frequency congestion.

Full narrative available

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