On June 21, 1999, about 1930 eastern daylight time, a homebuilt Rotorway Exec 90 helicopter, N4359N, registered to a private individual, was landed hard following a reported loss of engine power at the Tampa North Aero Park Airport, Lutz, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The helicopter was substantially damaged and the non-certificated pilot sustained serious injuries. The passenger was not injured. The flight originated about 1/2 hour earlier.

The owner provided a written statement to the FAA which indicated that he performed a preflight to the helicopter then started the engine. After the engine was at normal operating temperature he, "...checked out the mags and was having a problem with one working, it kept going in an out." He manipulated the toggle switch back and forth, "and the mag started working...." He then stated that he checked the fuel, lifted off to a hover, and all instruments checked fine. The flight proceeded about 5 miles away and he turned to return to the airport. The passenger began flying the helicopter and while descending over the airport at about 300 feet, with the collective lowered and the throttle reduced, the engine quit. The passenger fully lowered the collective and maintained 60 mph, then when the helicopter was 20 feet above ground level, he flared and the helicopter pitched up 45 degrees. The tailboom then impacted the ground, the main rotor blades contacted the tailboom, and the helicopter then landed hard. The owner also stated that he thought water shorted out both magneto switches. The pilot subsequently stated that following the accident, he inspected the helicopter and found corrosion at both ignition power pack connections. He also stated that the No. 1 then the No. 2 ignition power pack lights illuminated followed by failure of both power packs, and the main rotor tachometer indication failed when the No. 2 ignition power pack failed. The helicopter owner failed to complete the NTSB report form as required by Federal regulations.

The passenger stated that the takeoff and majority of the flight was flown by the pilot who performed several times, power recovery to a hover following a simulated partial loss of engine power. The pilot then flew an orbit around the airport then returned to perform another simulated partial loss of engine power. During the descent about 100-150 feet, the engine experienced a loss of power which was not immediately recognized by him; the main rotor rpm gauge indicated 0. The passenger then took the flight controls from the pilot, maintained 50 knots during the initial descent for the autorotative landing and pulled initial pitch pull at 50 feet, and final pitch pull at 25-30 feet. When the flight was 15-20 feet agl, he applied throttle input but the engine did not respond. The helicopter landed hard. He also stated that the main rotor tachometer went to zero because it was driven off of the two ignition systems.

Following the accident, the main rotor blades were removed, and in the presence of an FAA inspector, the engine was started and operated with no discrepancies noted. The FAA inspector also inspected the ignition switches for function, and both switches operated normally. There was no evidence of water leakage or corrosion at or in the vicinity of the ignition switch wiring. According to FAA records, the owner is not a certificated pilot, and the passenger is not rotorcraft rated.

By design, the helicopter was equipped with a "dual" type tachometer for engine and main rotor rpm which also contains a low main rotor warning light. Three wires from the "rotor tach sender" are directly connected to terminal Nos. 6, 7, and 8 at the dual "eng/rotor tach." The power supply to the gauge is fed from the instrument switch which is supplied power from the battery. According to the flight manual, each ignition light is operational when the switch is on.

Review of the preflight checklist revealed that the pilot is required to inspect the condition of each ignition system. Review of the "Autorotation Procedure From Altitude: For asymmetrical Rotor blades" checklist, revealed to maintain the approach airspeed of 65 mph, to flare at 35 feet agl using a 30-degree flare angle, and to level the aircraft at 3-5 feet of clearance between the tail rotor and the ground. The checklist also indicates during the level off, to add collective pitch if the helicopter is settling too rapidly, and to allow the helicopter to settle to 30 inches agl, then to add collective pitch as necessary. The checklists are attachments to this report.

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