The Swearingen SA226-AT Merlin IV, HK-5225, belonging to the company Colcharter, was scheduled to perform two flights as an air ambulance, first from Barranquilla to San Andres (ADZ) and then with a patient to Medellin (EOH). The first leg was uneventful. The controller cleared the flight to back track on runway 06/24 to the threshold of runway 06 for takeoff. After having taxied about 200 m, the right engine apparently experienced a substantial periodic acceleration to a taxi speed of 36 knots, where a maximum speed of 10 knots is allowed by the manufacturer. After the right engine accelerated, there was a trajectory change to the left side of the runway centerline. The crew attempted to keep the aircraft within the runway, however, the crew’s efforts did not have a positive result, allowing the aircraft to drift out of the runway into the safety zone. When the aircraft was over the safety zone, the crew attempted to use the braking system, however, the brakes were not effective due to the poor traction of the aircraft’s wheels with the grass surface in the safety zone. The aircraft continued to taxi to the left of the runway, until coming to a complete stop when the nose of the aircraft collided with a concrete wall bordering the airport. The aircraft suffered substantial damage in the nose area, however, the stress concentration due to the impact was more evident in the left front fuselage area, structurally compromising a large part of the skin. Probable Cause Runway excursion, as a result of loss of directional control of the aircraft, when exceeding the maximum taxi speed allowed by the aircraft manufacturer. Contributing Factors Possible misuse of the nose wheel steering control system, nose wheel steering, by the crew when using it above the allowed speed, hindering directional control. Lack of standardization of the company’s operating procedures, as it lacks its own taxiing policies and procedures. Probable self-imposed pressure from the crew, due to their desire to comply with the scheduled operation. Overconfidence, complacency, loss of situational awareness, and inadequate application of CRM by the crew, during a normal operation of the aircraft, which was apparently free of hazards.