Flight History
Northeast Airlines Flight 946 departed Boston at 17:42, bound for Lebanon, New Hampshire, and Montpelier, Vermont. The Fairchild aircraft climbed to a cruising altitude of 8,000 feet. At 18:08, the crew received clearance for an approach to Lebanon Airport, instructed to cruise at 5,000 feet and report leaving 6,000 feet. At 18:10:45, the controller terminated radar service and directed the flight to contact the Lebanon Flight Service Station (FSS). One minute later, the FSS advised the crew of the weather: an estimated ceiling of 2,000 feet overcast, visibility 10 miles, breaks in the overcast, altimeter setting 29.55, and calm wind.
Approach and Accident
The flight did not execute the published instrument approach procedure. Instead, the crew performed an abbreviated approach, making a right turn from their northwesterly heading, followed by a left turn to intercept the inbound radial to the VOR station. The inbound radial was intercepted approximately 8 to 10 miles northeast of the VOR station, passing through an altitude of about 4,500 feet. The crew began descending but did not level off at 2,800 feet m.s.l., the minimum altitude inbound to the VOR. During the approach to runway 25, the aircraft contacted trees on the cloud-shrouded side of a steep, rocky, heavily wooded mountain, 57 feet below the summit at 2,237 feet m.s.l. The aircraft cut a swath through trees, broke up, and caught fire. Two crew members and 30 passengers were killed, while 10 others were injured.
Investigation
The investigation determined the probable cause: the premature initiation of a descent towards the Minimum Descent Altitude, based on navigational instrument indications of an impending station passage in an area of course roughness. The crew was not able to determine accurately its position at this time because they had performed a non-standard instrument approach and there were no supplemental navigational aids available for their use.