On January 27, 1991, a Mbb BK 117 B-1 (registration N891GM) operated by Keystone Helicopter Corporatio was involved in an aviation accident near Sonestown, PA. Investigators recorded the probable cause as: THE PILOT'S INADEQUATE PREFLIGHT PLANNING TO ASSURE THAT THE INTENDED COURSE AND ALTITUDE PROVIDED ADEQUATE TERRAIN CLEARANCE. CONTRIBUTING FACTOR(S) WAS: THE DARK NIGHT, SNOW AND MOUNTAINOUS TERRAIN. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
A medevac helicopter returning from Danville to Sayre impacted North Mountain at 2,440 ft MSL. The crest was 2,520 ft MSL with 40-ft trees. A witness reported heavy snow.
Accident Overview
A medevac helicopter returning to Sayre after transporting a patient to Danville struck terrain on North Mountain. Recorded radar data and data from the helicopter's Loran-C memory indicate that the flight was following a direct course from Geisinger Medical Center at Danville to Robert Packer Hospital at Sayre. The aircraft's horizontal situation indicator (HSI) was set to display Loran course information.
Location and Conditions
The closest point of the intended course to the crest of North Mountain was approximately 3/4 mile to the west. Impact occurred at an elevation of 2,440 feet above mean sea level (MSL). The crest of the ridge is 2,520 feet MSL with trees reaching 40 feet in height. A witness who lives in a cabin on the mountain about 200 yards from the accident site stated that it was snowing very hard when he arrived at the cabin around 1930 hours.
Flight Path
The pilot had advised Williamsport Air Traffic Control Tower (ATCT) of transiting their control zone at 2,500 feet. The helicopter's impact point was 2,440 feet MSL, which is below both the ridge crest and the trees atop it.