What did the pilot know? In VFR conditions, when you are over mountains and approaching a lighted area at a lower elevation, you see the silhouette of the mountains eclipsing some of the lights. If lights appear to rise from behind the silhouette, you will clear the obstacle; if they appear to sink beneath it, you are on the way to a collision with terrain. Your aim point should be well above the ridge to ensure reasonable clearance. If a ridge is covered by clouds, it may be difficult to be sure what is happening; lights may appear and disappear haphazardly as your position shifts with respect to the obscuration.
Terrain awareness and warning systems (TAWS) are intended to deal with this sort of situation; so are synthetic and infrared-enhanced vision. But most airplanes do not have them.
The NTSB’s report implies, but does not assert, that the pilot may have flown into cloud, most likely inadvertently, over the final ridge. His asking the controller for the MIA, and his saying “Let’s go climb” in response to the altitude alert warning, suggest that he was uncertain of his position with respect to the local terrain, did not have visual contact with the lights of Alamosa and did not have a chart open in front of him. An IFR en route chart would have supplied the information he was asking the controller for, and a VFR chart would have made the danger of prematurely descending below 13,500 feet quite obvious.
The NTSB’s mention of “inadequate preflight planning” goes to the crux of this accident. The narrative of the flight, beginning with the estimate of the time en route as 20 minutes, suggests a certain hasty carelessness and an assumption that the pilot could make it up as he went along. In principle, he was right: A flight over mountainous terrain in total darkness should not present any difficulty to a pressurized twin turboprop. But it would require being aware of the salient characteristics of the route; climbing to an altitude that ensured ample terrain clearance; remaining at altitude until definitely clear of obstacles; and monitoring position, altitude and terrain. You have to be sure about these things; you may be penalized for guessing.
This article is based on the NTSB’s report of the accident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.