On November 16, 1987, a Cessna 441 (registration N2484B) was involved in an aviation accident near Mexicali, MX. Investigators recorded the probable cause as: The pilot's night vision was impeded due to lack of dark adaptation and varying light conditions, preventing the pilot from distinguishing the terrain relief, leading to collision with a ridge. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A USCS-operated Cessna 441 struck a ridge during a night tactical flight. The copilot lacked required currency and qualification. Dark adaptation was impaired by varied light conditions, preventing the pilot from discerning terrain relief.
Flight Details
A Cessna 441, operated by the United States Customs Service (USCS), collided with terrain while on an authorized night tactical flight. The flight originated during daylight hours and continued into astronomical twilight.
Pilot Qualifications
The copilot did not meet the currency standards required by USCS and was not qualified in the aircraft. The pilots did not dark adapt prior to the night conditions.
Night Vision Considerations
Dark adaptation was impeded by flight through various light conditions created by terrain and ambient light levels. With night vision impaired, the pilot would not have been able to distinguish the relief of the terrain.
Collision with Terrain
The aircraft collided with a small ridge that abruptly rose 300 feet.
Probable cause
The pilot's night vision was impeded due to lack of dark adaptation and varying light conditions, preventing the pilot from distinguishing the terrain relief, leading to collision with a ridge.