What happened
On September 25, 2011, a Robinson R44 II helicopter, registration PR-PIP, was performing a private flight from Carolina, MA, to Itapiratins, TO. The flight included two intermediate stops at Porto Bom and Barra do Ouro. During the final leg of the flight, approximately 50 minutes into the transit, the pilot observed the main rotor RPM indicator exceeding the maximum operational limit of 102%.
Misinterpreting this indication as a rotor RPM overspeed, the pilot attempted to manually control the rotation by lowering the collective, which proved unsuccessful. The pilot then decided to perform an immediate landing in an open field via an autorotation maneuver. Because the engine was still producing power, the pilot'-s decision to fully lower the collective resulted in a descent with residual power at minimum collective pitch. The aircraft struck irregular terrain with significant force, resulting in substantial damage to the skids, horizontal stabilizer, and tail rotor blades. All four occupants escaped the crash uninjured.
The investigation
CENIPA investigators examined the aircraft's systems, including the engine governor, magnetos, fuel pump, and ignition plugs, finding no mechanical abnormalities. The investigation confirmed that the engine governor was functioning correctly and that the aircraft was within weight and balance limits.
The investigation focused on the pilot's response to the RPM indication. According to the R44 Pilot’s Operating Handbook, in the event of a governor failure, the pilot should hold the lever firmly to prevent overspeed, switch off the governor, and continue the flight using manual control. The investigation established that the pilot failed to follow these prescribed emergency procedures, opting instead for an unnecessary forced landing.
Findings
- The pilot misidentified the nature of the RPM indication.
- The pilot adopted procedures that deviated from the manufacturer's emergency manual.
- The pilot's decision-making and flight controls were inadequate for the situation.
- The pilot's lack of experience contributed to the incorrect interpretation of the flight parameters and the subsequent improper execution of the landing maneuver.