Accident involving a Puma HC MK 2 (XW229) in Kabul, Afghanistan

On the afternoon of 11 October 2015, a Royal Air Force Puma HC2 (serial number XW229) was performing a routine passenger transfer flight within the Kabul "green zone." The aircraft was part of a two-ship formation operating out of Kabul International Airport. As the aircraft approached the landing site at the NATO Headquarters (HQ RS), it entered a confined and complex urban airspace.

The Service Inquiry (SI) determined that during the final approach, the Puma’s main rotor blades struck the tether of a Persistent Threat Detection System (PTDS)—a large, helium-filled surveillance balloon (aerostat) that was moored to the ground by a high-strength cable. The impact with the cable caused significant damage to the main rotor blades, leading to severe vibrations and an immediate loss of lift and control. The helicopter rolled and plummeted into the HQ RS courtyard. All five passengers and crew on board were killed in the impact.

The investigation identified the "Causal Factor" as the aircraft’s flight path, which brought it into contact with the aerostat tether. However, the inquiry focused heavily on why the crew was unaware of the tether's exact position. It was discovered that while the aerostat was a known permanent fixture, its precise location and the "swing circle" of its cable were not clearly marked on local aeronautical charts used by the crews. Furthermore, the cable itself was virtually invisible against the complex urban background of Kabul.

The report also highlighted "Contributory Factors" related to the command and control of the mission. It found that the risk of operating helicopters in such close proximity to tethered balloons had been identified in previous safety reports, but the mitigation measures—such as moving the balloon or creating a larger exclusion zone—had not been effectively implemented by NATO theatre command. By January 2026, the XW229 inquiry remains a primary reference for "Airspace Integration" in high-threat environments, highlighting the fatal risks posed by non-traditional flight hazards like aerostats in congested cityscapes.