Air Safety Institute Safety Spotlight
Too low for the terrain
Flying VFR at night can be a magical experience, at least over reasonably well-lit terrain. VFR flight on a dark night over sparsely populated areas is a different experience altogether--one that can quickly become a challenge even for a skilled pilot following a familiar route.
On January 17, 2006, the pilot of a Cessna 182 was killed when he flew into a hill seven miles south of Big Pine, California. The noninstrument-rated pilot had more than 6,500 hours of flight time, with thousands of those hours accrued in the Owens Valley, where the accident occurred.
The flight departed from Eastern Sierra Regional Airport in Bishop, California, at 8:15 p.m. en route to Lone Pine Airport, 57 miles to the south. Visual meteorological conditions prevailed.
At approximately 8:30 p.m., a witness at a campground in the valley reportedly noticed faint red and green lights in the distance. He said the lights appeared to be at ground level. As the lights became brighter and more distinct, they began to ascend, and the witness realized that the lights were part of an airplane. He was able to hear the aircraft's engine running as it hit a hill east of the campground and burned.
The airplane wreckage was found at 4,700 feet msl--about 275 feet below the top of a hill that rises from the valley floor. The terrain around the hill is relatively flat, with an elevation of 4,300 feet msl.
The crash site was near a heavily traveled highway that runs north to south through the valley. Lights from vehicles on the highway likely would have been visible to the pilot, but there were no lights to distinguish the rising terrain. At the time of the accident, the nearly full moon had just risen but was blocked by mountains to the east.
According to the NTSB's examination of impact ground scars, the airplane was in controlled, near-level flight when it struck the hill. The airframe and engine showed no signs of preimpact failures or malfunctions. The probable cause of the accident was the pilot's failure to maintain an adequate terrain-clearance altitude, which resulted in controlled flight into terrain, the NTSB said. Contributing factors were the rising terrain and the dark night.
Flying VFR at night over unlit terrain can be tricky. Mountains become all but invisible after the sun goes down. Preflight terrain-avoidance planning is critical to ensure there's plenty of altitude between us and the highest unseen obstacle in our path.
The pilot in this accident appeared to be flying very low--about 400 feet agl, below the legal minimum of 500 feet agl in uncongested areas, and unwise in a valley dotted with hills nearly 700 feet high--a valley the pilot reportedly knew well. In this case, an extra 300 feet of altitude would have made all the difference. A 1,000-foot buffer on top of that would have been the safe choice.
An aviation technical writer with the AOPA Air Safety Foundation, Carl Peterson creates interactive courses and other safety education materials for the aviation community. He has been flying since 1989.
By Carl Peterson