Airbus EC135 N36RX accident near Apple Valley, California

Probable cause

The ingestion of a towel from an unsecured storage container at the landing site into the helicopter's fenestron during the landing.

NTSB analysis

According to the airline transport pilot, firefighting personnel were using the helicopter for training to simulate patient loading and unloading. The training consisted of multiple takeoffs and landings from the training center landing site. The pilot reported that, during the third landing, when the helicopter was between 2 and 3 ft above ground level, he felt it shudder unexpectedly. The pilot immediately landed and shut down the helicopter without further incident. The pilot reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

A postflight examination revealed that a towel had been ingested into the fenestron, which resulted in substantial damage to the fenestron tail rotor blades, fenestron housing body, tailboom, and tail rotor drive shaft flex couplings. The pilot reported that the towel had migrated from an unsecured storage container near the landing site. The investigation revealed that, when the towel was ingested, the fenestron hub fairing detached from the hub body, which was then ingested by the fenestron tail rotor blades. The operator's director of maintenance reported that a postaccident examination revealed that all of the main rotor blades "received a small amount of [foreign object damage] FOD…at middle cord line near the tips" and that the "damage was the result of FOD from the Fenestron [hub fairing ingestion] after the towel was ingested." This evidence indicates that the hub fairing body becoming detached due to the ingestion of the towel contributed to the severity of the damage.

Text from the NTSB. Open the NTSB docket for GAA16LA056 for the full record.