N999TF

On April 1, 1996, about 1004 eastern standard time, Canadair CL-600-1A11, N999TF, nose landing gear collapsed on landing at the Raleigh-Durham Airport, Raleigh, North Carolina. The aircraft was being operated by Pal-Waukee Aviation under the provisions of 14 CFR Part 135 and instrument flight rules. Instrument meteorological conditions existed at the time of the accident, and an instrument flight rules flight plan was in effect. The airline transport pilot, his co-pilot, the cabin attendant, and the six passengers were not injured; the aircraft was substantially damaged. The flight departed Milwaukee, Wisconsin at 0830 the same day.

The pilot stated that when the landing gear was extended, the landing gear position indicating system presented conflicting information regarding the position of the nose landing gear. The landing gear was then raised, and the indicator lights were all extinguished. The gear was again extended. The main gear indicator lights were illuminated, indicating that the main gear was down, but the nose gear light was extinguished. The light in the gear handle was off, indicating that the system was functioning properly. The pilot did not use the emergency landing gear extension system. The aircraft was landed and the nose gear collapsed. The pilot stated that the clouds and visibility precluded any observation of the landing gear by airport tower personnel.

Post accident examination of the nose gear selector valve revealed an intermittently inoperative extend solenoid valve. According to the failure analysis report, the solenoid valve most likely experienced moisture entry. The manufacturer reported that the selector valve was repaired with an upgraded solenoid to preclude recurrence of the failure.