What happened
On 2 August 2017, an AW109SP Grand New, registration G-HLCM, was performing a non-revenue commercial air transport flight when the pilot experienced significant vibrations. As the helicopter approached a private landing site near Clifton Dykes, Penrith, Cumbria, the pilot felt a shudder through the airframe and the cyclic control.
To ensure the safety of people on the ground, the pilot decided to divert from the intended landing site and instead landed in a nearby field. Following the shutdown of the engines, an inspection revealed that the tip cap of one of the main rotor blades had become detached. No injuries were reported, and there were no injuries to the crew.
The investigation
Following the incident, the aircraft manufacturer conducted an investigation into the failure. The inquiry determined that the detachment of the tip cap was the result of a surface preparation error during manufacturing. This error had compromised the structural integrity of the bonded joint, making it susceptible to failure.
Safety action
In response to the findings, the manufacturer identified other main rotor blades that might be subject to the same issue and released Service Bulletin 109SP-116 to implement periodic inspections. Additionally, EASA issued Emergency Airworthiness Directive 2017-0176-E to make these inspections mandatory.