What happened
On November 25, 2011, a Bell 212 helicopter, registration HC-CLH, was performing a scheduled test flight at the Aeromaster maintenance facilities in the El Condado sector of Quito. The purpose of the flight was to conduct vibration measurements following a 3,0-hour maintenance check, preparing the aircraft for its return to service in the El Coca region.
The flight crew, consisting of two pilots and two maintenance mechanics, began the operation with low-altitude hovering maneuvers over the helipad. At approximately 16:47 UTC, the pilot initiated a takeoff maneuver, orienting the aircraft northeast and performing a vertical ascent to roughly 45 feet. As the aircraft transitioned into forward flight, it experienced a sudden loss of rotor RPM. The pilot attempted to return to the landing pad; however, the aircraft struck the edge of an adjacent ravine with its right skid. The helicopter slid down the slope and came to rest at the bottom of the ravine, 35 meters below the takeoff site. The impact resulted in two fatalities among the crew and the total destruction of the aircraft.
The investigation
The investigation focused on the mechanical state of the aircraft, the flight planning, and the crew's performance during the critical takeoff phase. Investigators examined the maintenance logs, which revealed that while most inspections were up to date, certain signatures were missing from specific component inspection forms.
Analysis of the Cockpit Voice Recorder (CVR) and external video footage showed that rotor RPM began to decline immediately after the aircraft exited the ground effect. The investigation also reviewed the weight and balance documentation, noting that while the takeoff weight was within limits, the weight and balance sheet had not been signed by the pilot. Furthermore, no pre-flight briefing was recorded or observed among the crew members.
Findings
- The primary cause of the accident was that the takeoff continued despite a loss of rotor RPM during the initial ascent, which was not detected in time by the crew.
- As the helicopter moved away from the helipad, it lost the aerodynamic benefit of ground effect, contributing to the power/RPM instability.
- There was a lack of crew coordination and monitoring, as no pre-flight briefing was conducted and flight instruments were not adequately monitored during takeoff.
- Maintenance records for certain scheduled inspections were incomplete due to missing authorized signatures.
- The helipad facilities did not fully comply with ICAO standards.