Texas Helicopter Corp OH 13H/M74A N10009 accident near Minonk, Illinois

Probable cause

Failure of the truck driver to ensure that he had adequate clearance to pass under the helicopter and the failure of the loader to park in a safer area for reloading operations.

NTSB analysis

During reloading operations for an agricultural flight, the nurse truck was parked on the right shoulder of a road, facing west. The helicopter was parked on the elevated helipad on top of the nurse truck, facing north, with the engine running and rotor blades turning. The helicopter's tail boom and rotor disk extended about 8-10 ft over the road. As the loader was reloading the helicopter's product tanks, a westbound semi-trailer truck drove underneath the rotor disk and struck the helicopter's tail boom. The semi-trailer truck driver said he thought he had enough clearance to pass safely under the helicopter's tail rotor. The pilot said that if the nurse truck had parked closer to an adjoining field, the platform would have a tilt, making it difficult to land for servicing. It is likely that the semi-trailer truck driver failed to ensure that he had adequate clearance to pass under the helicopter and that the loader failed to park in a safer area for the reloading operations.

Text from the NTSB. Open the NTSB docket for CEN16LA284 for the full record.