CESSNA 208B near Roswell, NM — 2014-12-30

Probable cause

The pilot's failure to maintain adequate airspeed to compensate for icing on the airplane's wings and control surfaces during a circling approach, which resulted in an aerodynamic stall and impact with terrain.

NTSB narrative

The airline transport pilot received a weather dispatch package for a planned cargo flight in a single-engine, turboprop-equipped airplane. The weather forecast called for instrument meteorological conditions (IMC) en route. The pilot reported that he encountered inflight icing and solid IMC for most of the flight and was unable to climb above 8,500 ft mean sea level due to icing on the airplane's wings. During the approach at his destination airport, he reported to the air traffic controller that he didn't have much elevator control and thought that his controls were "almost frozen." The pilot was late in identifying the runway and elected to do a no-flap circling approach, staying below the clouds. During the maneuver, an intermittent stall warning horn was heard in the background of radio communications between the controller and the pilot, indicating that the airplane was below the manufacturer's recommended approach speed. The pilot stated that he "never went below 100 knots" during the approach; the manufacturer's minimum recommended no-flaps airspeed in icing conditions is 120 knots. Additionally, the manufacturer recommended using 10° of flap extension for landing when airframe ice was suspected. Before crossing the runway threshold, the airplane experienced an uncommanded roll to the left, and the left wing and aileron impacted terrain. Examination of the airplane noted damage to the left wing, including the presence of frost and ice on the airplane. It is likely that, during the approach for landing, the pilot did not compensate for the airframe icing by increasing the approach airspeed as recommended. The accident is consistent with the pilot not maintaining adequate airspeed during a circling approach to the runway, and the uncommanded roll is consistent with an aerodynamic stall. The situation was likely exacerbated by the presence of ice on the wings and control surfaces.

Analysis

Primary failure mode

Controlled flight into terrain

First missed decision gate

Pilot could have performed missed approach instead of circling to land.

NTSB coding

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

Evidence available

• ATC audio
• Photos
• 7 docket documents

Docket documents7

• ATC Transcriptatc
• Dispatch Weatheratc
• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Statement of Party Representatives to NTSB Investigationinterview
• Approach plate rwy 35other
• Cessna 208 Supplement - Excerptsother
• Photosphotos

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