Investigation Summary
Flight 411 was a short 37-nautical-mile hop from Albany to Glens Falls, with an estimated flight time of only 15 minutes. Surface weather at Glens Falls was reported as 2,100 feet overcast, 7 miles visibility in light rain, with winds from 180 degrees at 12 knots gusting to 22. Due to a significant tailwind of approximately 50 knots at altitude, the aircraft arrived in the Glens Falls area quickly. Air Traffic Control cleared the flight for a VOR approach to Runway 19 but did not specify which of the two published procedures to use. The crew chose not to fly the only legally available approach (VOR 1), which would have required a circling maneuver from the south. Instead, they attempted an improvised, unauthorized version of the VOR/DME 19 approach from the north. Mohawk company policy at the time prohibited using DME as a primary navigational instrument, making the northern approach unavailable to this crew. During a course reversal turn over Lake George, the aircraft descended into a region of severe turbulence and a 60-knot southerly wind that created a powerful downdraft. The NTSB found no evidence to explain why the crew attempted this specific, non-standard approach path at an altitude insufficient to recover from the mountain-induced downdraft.
Final Conclusions
The NTSB issued its final report (NTSB-AAR-70-12) on June 25, 1970. The board determined the probable cause was the captain's decision to exceed clearance limits during the approach, which placed the aircraft into a severe lee-of-the-mountain downdraft at an altitude that made recovery impossible. The Cockpit Voice Recorder was recovered but found to be unusable due to fire damage, leaving the specific reasoning for the crew's choice of approach unknown.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
First Officer
Systems & Failure Modes
VOR/DME Approach
A navigational procedure using Very High Frequency Omnidirectional Range and Distance Measuring Equipment; the crew attempted an unauthorized modification of this procedure.
Cockpit Voice Recorder (CVR)
A flight recorder used to record the audio environment in the flight deck; the unit on N7811M was rendered unusable by thermal damage.
Interesting Facts
- 01The aircraft was a Fairchild Hiller FH-227B, a stretched version of the Fokker F27 Friendship.
- 02The aircraft (MSN 531) was manufactured in 1966.
- 03The flight was only 8 minutes into its journey from Albany when it reached the Glens Falls area.
- 04A 60-knot southerly wind created a severe downdraft on the lee side of Pilot Knob Mountain.
- 05The Cockpit Voice Recorder was damaged by the post-crash fire and provided no usable data.
- 06Mohawk Airlines policy prohibited the use of DME as a primary navigational instrument at the time.
Safety Actions & Advisories
Clarification of ATC Clearances
Source ↗The investigation highlighted that ATC cleared the flight for 'the VOR approach' without specifying which of the two published procedures was intended. Safety discussions following the accident emphasized the need for controllers to specify the exact approach procedure when multiple options exist to prevent crew ambiguity.
DME Navigational Policy Review
Source ↗The accident underscored the risks of crews attempting improvised procedures when their airline's equipment or policy (such as Mohawk's prohibition on DME as a primary instrument) restricted the use of safer, published instrument approaches.