Flight History
On April 7, 2015, a Robinson R44 Raven II helicopter, registration CS-HGF, operated by Helibravo, departed from Cascais Airfield (LPCS) for an instrument approach training flight to Montijo military air base (LPMT). The flight was the 17th mission of the IR(H) training program, with an expected duration of two hours. On board were an instructor pilot and a student pilot.
During the final phase of the third approach to LPMT, at around 300 feet and while performing a go-around procedure, abnormal vibrations and noises were perceived by both occupants. Subsequently, the instrument panel displayed illumination of the "FUEL FILTER", "AUX FUEL PUMP", and a flickering "CLUTCH" warning lights. The instructor pilot assumed control, declared an emergency, and performed a rolled emergency landing in accordance with established procedures. Meteorological conditions at the site were partially cloudy sky (scattered clouds at 3000 feet), low intensity west wind, and visibility of 10 km or more.
Injuries and Damage
Both crew members exited the aircraft unharmed. The aircraft sustained minor damage to the landing skid shoes and a catastrophic failure of the engine crankshaft.
Aircraft and Engine
The Robinson R44 Raven II is a small single-engine helicopter with a four-seat capacity, dual controls, a two-blade teetering main rotor, and skid-type landing gear. The aircraft was used by the operator for private flights, commercial initial pilot training, and leisure flights.
The helicopter was equipped with a Lycoming IO-540-AE1A5 six-cylinder, air-cooled, horizontally opposed, fuel-injected engine (serial number L-31894-48E). The engine was installed new in 2007 and had accumulated 2178:29 hours of service at the time of the failure. Although the engine can produce 260 HP, its power was derated to 245 HP for transient take-off conditions (limited to 5 minutes at 2800 RPM) and a maximum continuous output of 205 HP at 2718 RPM.
After the incident, the engine and components were assessed at a manufacturer-authorized workshop. The crankshaft (part number 13E47622, serial number V537945676) was found fractured. The fracture occurred in the short cheek connecting the crankshaft main bearing journal 4 to the cylinder rod bearing journal 4, resulting in two separate parts.
Investigation
The former GPIAA (now GPIAAF) was notified and initiated a safety investigation, classifying the occurrence as a serious incident. The investigation team analyzed available evidence and test results. A detailed analysis was requested from materials specialists to identify the component failure mode. The investigation concluded that the event had low complexity, and the safety lessons were limited, being covered by the scope of the work carried out. The investigation was closed with the publication of this summary report, disseminating the relevant facts and findings to the aeronautical community to prevent recurrence.