ROCKWELL INTERNATIONAL 690B near East Haven, CT — 2013-08-09

Probable cause

The pilot's failure to maintain airspeed while banking aggressively in and out of clouds for landing in gusty tailwind conditions, which resulted in an aerodynamic stall and uncontrolled descent.

NTSB narrative

The pilot was attempting a circling approach with a strong gusty tailwind. Radar data and an air traffic controller confirmed that the airplane was circling at or below the minimum descent altitude of 720 feet (708 feet above ground level [agl]) while flying in and out of an overcast ceiling that was varying between 600 feet and 1,100 feet agl. The airplane was flying at 100 knots and was close to the runway threshold on the left downwind leg of the airport traffic pattern, which would have required a 180-degree turn with a 45-degree or greater bank to align with the runway. Assuming a consistent bank of 45 degrees, and a stall speed of 88 to 94 knots, the airplane would have been near stall during that bank. If the bank was increased due to the tailwind, the stall speed would have increased above 100 knots. Additionally, witnesses saw the airplane descend out of the clouds in a nose-down attitude. Thus, it was likely the pilot encountered an aerodynamic stall as he was banking sharply, while flying in and out of clouds, trying to align the airplane with the runway. Toxicological testing revealed the presence of zolpidem, which is a sleep aid marketed under the brand name Ambien; however, the levels were well below the therapeutic range and consistent with the pilot taking the medication the evening before the accident. Therefore, the pilot was not impaired due to the zolpidem. Examination of the wreckage did not reveal any preimpact mechanical malfunctions.

Analysis

Primary failure mode

Spatial disorientation

First missed decision gate

Pilot could have aborted the approach when unable to maintain visual contact.

NTSB coding

• Aerodynamic stall/spin · Approach-circling (IFR)

Evidence available

• ATC audio
• Photos
• 19 docket documents

Docket documents19

• Excerpts From ATC Transcriptsatc
• Aircraft Performance Studyform
• Evidence Control Forms (Replace OUO item in MyDMS with updated file on public side)form
• Release of Wreckage Formform
• Statement of Party Representatives to NTSB Investigationinterview
• Witness Statementsinterview
• Excerpts From Maintenance Recordsother
• Excerpts From Pilot Logbookother
• Fuel Receipts.other
• Instrument Approach Procedureother
• Meteorology 5 - Attachment 1other
• Meteorology 5 - Attachment 2other
• Photo 1: Airplane at rest.photos
• Photo 2: Left wing.photos
• Photo 3: View of the cockpit.photos
• Manufacturer Report of Engine Examinationsreport
• Manufacturer Report of Propeller Examinationreport
• Meteorology 5 - Factual Report of Group Chairmanreport
• Toxicological Report.report

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