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On October 22, 1999, about 1507 hours Pacific daylight time, an experimental Luhnau BD-5B, N62765, was substantially damaged when the amateur-built airplane descended at a steep angle and impacted terrain about 1 mile southwest of the Boulder City Municipal Airport, Boulder City, Nevada. Visual meteorological conditions prevailed and no flight plan was filed for the post-maintenance test flight. The airline transport pilot, the sole occupant, was fatally injured. The airplane was owned and operated by the pilot. The flight was performed under the provisions of 14 CFR Part 91. The flight originated from Boulder City about 1500.
A witness reported observing the pilot takeoff from runway 09, climb to about 400 feet above ground level, turn right onto the crosswind leg, and then turn onto the downwind leg at the traffic pattern altitude. Thereafter, the witness heard the pilot announce his position in the traffic pattern. About 10 seconds later, while the airplane was maintaining a level flight cruise attitude, the airplane began descending, and it turned right toward the airport. The witness further reported that the rate of descent increased and the pilot broadcast "765 I've got a problem." The witness lost sight of the airplane while it was descending at what appeared to be a 30- to 40-degree nose down angle.
The pilot was a retired airline captain. He had experience flying Boeing 727, 737, DC-8, DC-10, and B-747 airplanes. The pilot was not the builder of his experimental airplane. Also, he did not possess either a repairman or a Federal Aviation Administration (FAA) Airframe & Powerplant certificate.
The pilot's total experience flying the airplane was about 16 hours. The accident occurred during his first flight following maintenance.
WRECKAGE AND IMPACT INFORMATION
The FAA inspector reported that the on-scene accident site and wreckage examination revealed the airplane impacted flat, desert terrain in a nose low attitude consistent with the last flight attitude observed by the witness. A shallow impact crater was noted at the initial point of ground impact. The propeller was found about 15 feet northwest of the crater.
About 70 feet northwest of the crater, the main wreckage was located on a 320-degree magnetic heading. The approach end of runway 33 was about 1 mile and 330 degrees ahead of the airplane.
The entire airplane structure was found in the vicinity of the accident site. The continuity of the flight control system was confirmed. There was no evidence of fire.
The FAA inspector reported that the airplane's propeller assembly did not appear to have been damaged during the impact sequence. The propeller blade pitch angle was found near the 2-degree pitch position. This position is consistent with the blade being in a nearly flat pitch. A blade oriented at this angle would produce considerable drag, according to the FAA.
A review of the airplane's logbook and associated records indicates that on October 9, 1999, an NSI Aero Products, CAP 140 Cockpit Adjustable Propeller and hub assembly was installed in the airplane. The logbook was signed off by "C S Folsom." Thereafter, on October 10 and 11, the pilot performed three taxi tests for 0.8, 1.5, and 0.8 hours.
On October 16, 1999, the logbook indicates that the airplane received an annual inspection. A mechanic having inspection authorization signed off the inspection. No additional taxi tests or evidence of flight operation was observed recorded in the airplane's or the pilot's logbook, or in the pilot's notebook which listed various test results.
TESTS AND RESEARCH
An electric motor controlled the pusher-propeller's variable pitch setting. A witness reported that just prior to the flight, the pilot made a wiring change to the propeller's pitch control drive motor. The alteration was intended to reduce the time necessary to vary the pitch through its full range of travel from 15 to between 7 and 8 seconds.
The FAA reported observing a loose wire at terminal #10 on the electric control unit (ECU module) that is connected to the adjustable propeller's pitch control system. The FAA indicated that this wire losing contact at the terminal would likely result in an inhibition of the blades to properly change pitch, including a lack of pitch control authority. In addition, a jumper wire was found placed across terminals number 1 and 5 that was used to double the propeller blade pitch change speed.
The propeller motor was subsequently functionally tested and full blade pitch travel was confirmed. No mechanical malfunctions were noted with the propeller assembly that was related to its operation.
The acting general manager of NSI Aero Products (the propeller assembly manufacturer) indicated, in pertinent part, that the propeller assembly was improperly installed on the accident aircraft. As the pilot advanced the propeller to resume powered flight it stopped working due to a disconnected ground on the propeller ECU. With the propeller stalled at a very low pitch angle, the aircraft did not have sufficient thrust to maintain level flight. (See NSI's report for additional details.)