The loss of a Northrop Grumman-owned Fire Scout vertical take-off and landing tactical unmanned air vehicle (VTUAV) late last year was caused by antennas being damaged during handling by company technicians prior to installation on the aircraft.
The UAV, dubbed P1, was performing risk reduction flight testing on 4 November when it was destroyed after a 26min flight. Northrop Grumman has resumed flights using a manned prototype and is also funding a replacement VTUAV. Risk-reduction testing will continue in preparation for US Navy flying, from December, of an engineering and manufacturing development unmanned Fire Scout. The UAV is based on the Rolls-Royce 250-powered Schweizer 330 helicopter.
An accident investigation board comprising company and USN experts concluded that radar altimeter antennas installed on P1 were damaged at Northrop Grumman's San Diego facility.
The accident report says the antennas created a false reading, indicating that P1 was just above the ground when it was hovering at 500ft (150m) in preparation for landing. After the command was given to land, the guidance and control system believed the Fire Scout had landed. Performing as designed, the guidance and control system then commenced engine and systems shut down. An antennas examination revealed damage that was "hardly noticeable", says Doug Fronius, Northrop Grumman vice president.
The board said the crash would have been prevented if P1 was equipped with the dual redundant flight control avionics required on production Fire Scouts. Northrop Grumman has since revamped quality control procedures.
Source: Flight International
