What happened
On 5 May 2017, an Agusta A109S Grand, registration G-PBWR, was performing a positioning flight from Dunsfold Aerodrome to London Stansted Airport to collect a passenger for a commercial air transport service. Prior to departure, the aircraft had undergone an 'A' Check and standard pre-flight inspections, which revealed no issues. During the flight, the pilot encountered significant low-level atmospheric turbulence, though the aircraft's handling remained normal. Following a routine landing at London Stansted, ground personnel alerted the pilot to a structural issue. A subsequent inspection revealed that the left-side horizontal stabiliser had failed at roughly mid-span, with the damaged section remaining attached only by electrical cabling and portions of the skin.
The investigation
The investigation focused on the structural integrity of the horizontal stabiliser and the effectiveness of existing maintenance protocols. It was established that the affected area of the stabiliser was subject to EASA Airworthiness Directive 2011-0150, which mandated inspections every 50 flying hours. The aircraft's last inspection had been performed approximately 45 hours before the incident, with no defects noted at that time. The incident was reported to the regulator through the mandatory occurrence reporting scheme, and the damaged component was sent to the manufacturer for a detailed forensic examination.
Findings
- The left-side horizontal stabiliser of the Agusta A109S Grand suffered a structural failure at mid-span.
- The failure occurred despite the aircraft having undergone a required inspection only 45 flying hours prior.
- The failure of the left side horizontal stabiliser was the primary event, occurring within an area already subject to intensive repetitive inspection requirements.