What happened
During an approach to runway 14 at Montgomery County Airpark (GAI) in Gaithersburg, Maryland, an aircraft crashed into the ground and three nearby residences. The impact occurred approximately 0.75 miles from the runway threshold. A fire broke out following the collision, involving both the aircraft and one of the homes. The accident resulted in six fatalities, including the pilot, two passengers, and three residents of the impacted house. The aircraft was completely destroyed by the force of the impact and the subsequent fire.
Data recovered from the cockpit voice and data recorder (CVDR) showed that the flight departed Horace Williams Airport in Chapel Hill, North Carolina, at approximately 0945. While the initial flight stages were uneventful, the passenger noted the aircraft had entered clouds roughly 15 minutes after takeoff. Although the engine anti-ice and wing/stabilizer deice systems were briefly activated for two minutes, they were manually deactivated shortly thereafter. During the approach, automated weather reports indicated conditions suitable for ice accumulation, yet the deice systems remained off for the remainder of the flight.
Findings
Investigation of the flight data revealed that the pilot failed to follow established procedures for icing conditions. Although the pilot was expected to execute the Descent checklist from the Quick Reference Handbook (QRH) before descending through 10,000 feet, the deice systems were not reactivated despite the presence of icing conditions.
Furthermore, the pilot established a landing reference speed (Vref) of 92 knots. This speed was calculated using performance data that assumed the deice systems were inactive and that the aircraft was lighter than its actual weight. Had the pilot correctly applied the Normal Icing Conditions checklist and accounted for the true weight of the aircraft, the required approach speed would have been 126 knots. The failure to use appropriate landing speeds for icing conditions was a critical factor in the accident.