What happened
On 25 November 2015, an EC135 T1, registration G-NWPS, was performing a commercial passenger flight near Bilsdale, North Yorkshire. The pilot was conducting a landing at an unmarked area adjacent to a television mast, a location suggested by the mast's operating company. The weather conditions featured good visibility and a light westerly wind.
As the pilot descended to a hover and began hover-taxiing forward approximately 10 metres toward a firmer surface, the helicopter's downwash began to displace pieces of debris located to the front and right of the aircraft. While the pilot did not initially view these items as a threat, a sudden jolt in the yaw axis and vibrations through the tail rotor pedals were felt. Although the pilot initially suspected the tail might have struck an unseen object, the aircraft remained under control. After confirming the safety of the two passengers and the crew, the pilot completed the landing.
The investigation
Post-flight inspections revealed substantial damage to the aircraft's fenestron tail rotor unit. The hub cover had detached and was found in a distorted and lacerated state. A piece of metal, roughly 20 cm square, was recovered from the vicinity. The investigation established that this metal object had been drawn into the fenestron duct, striking the hub cover and causing it to detach. This sequence of events led to the ingestion of metal fragments into the fenestron fan, resulting in deep cuts to the duct surface, scraped paintwork, and foreign object damage to the fan blades.
CCTV footage of the incident captured a single piece of debris entering the duct, which coincided with a visible puff of smoke and a slight leftward yaw of the tail. The debris, which appeared to be a piece of yellow and black signage, could not be traced to a specific origin. The investigation also noted that while the helicopter operator's policy involves inspecting such sites, it could not be confirmed if a pre-landing check for foreign objects had been performed at this specific location.