IHC Health Services Agusta A109 SP accident

The crew of the helicopter air ambulance flight departed to pick up a patient in night visual meteorological conditions. While en route to their destination, a flight nurse, who was seated in the left seat and communicating with ground personnel, inadvertently depressed the helicopter’s left anti-torque pedal instead of the foot-activated push-to-talk (PTT) switch to activate the microphone. The helicopter suddenly yawed left about 11°, which the pilot immediately countered and restored straight-and-level flight. The helicopter sustained damage to the tail rotor blades and empennage that was not discovered until several hours later when the accident crew was relieved. The damage to the blades and empennage was consistent with their making contact, and the flight data suggest this occurred during the first leg of the shift flight as the crew did not experience any other events that would have caused the degree of damage observed. Postaccident examination of the tail rotor gearbox and tail rotor blades did not reveal any anomalies. A performance analysis by the helicopter manufacturer showed that the amount of left pedal applied at the time of the pilot’s yaw recovery exceeded the parameters tested during certification. The flight nurse seated in the cockpit at the time of the accident normally sat in the rear cabin and was likely not as familiar with the location of the PTT, especially in nighttime lighting conditions.

Verbatim NTSB analysis and probable cause from the NTSB dataset