What happened
The pilot initiated an instrument approach during weather conditions that were highly conducive to structural icing. At the time of the event, visibility was reduced by fog and light snow, with the ambient temperature recorded at 32 degrees Fahrenheit. The aircraft in question was not equipped with deicing systems, leaving it vulnerable to ice accumulation on critical surfaces.
During the approach phase and subsequently during the climb-out following a missed approach, structural ice began to accrete on the airframe. This accumulation significantly degraded the aircraft's aerodynamic performance and lift capabilities. As a result, the aircraft was unable to achieve the necessary climb rate to reach the assigned altitude or transition into Visual Flight Rules (VFR) conditions as intended.
The aircraft continued to accumulate ice while operating in Instrument Meteorological Conditions (IMC). The worsening performance eventually made it impossible to maintain controlled flight at higher altitudes. To prevent a catastrophic loss of control, the pilot was forced to descend until visual contact with the ground could be re-established.
The investigation
The investigation focused on the environmental conditions and the aircraft's configuration during the incident. Key findings included:
- The presence of fog and light snow at 32 degrees Fahrenheit created a high risk for structural icing.
- The aircraft lacked deicing equipment, which is standard safety gear for operations in such weather.
- Ice accretion was confirmed to have occurred during both the approach and the missed approach climb-out.
Findings
The primary factor contributing to the incident was the structural ice accretion on an aircraft not equipped for deicing. The degradation of performance prevented the pilot from climbing to a safe altitude, ultimately forcing an emergency descent to regain visual reference with the ground.