GUY NORRIS / LOS ANGELES
US defence investigation highlights pressing need to refocus on key technologies to improve mission effectiveness
A recent study of unmanned air vehicle (UAV) reliability for the US Office of the Secretary of Defense (OSD) has revealed significant areas of concern, and the urgent need to refocus on key technologies to help improve mission effectiveness.
Results of the study, due to be published shortly, show reliability is suffering because of over-emphasis on affordability. "In the drive to make it less expensive, we have cut corners and that has reduced reliability," says the OSD's Dyke Weatherington. "Component quality has been sacrificed and, although UAVs have performed admirably, they have suffered high loss rates."
The aim of the study, conducted to support the integration of UAVs into US national airspace, was to identify specific risks to aircraft and people on the ground, improve UAV reliability metrics and developing UAV airspace operating regulations that might satisfy the Federal Aviation Administration.
Weatherington says loss statistics show the majority of crashes are propulsion-related, with flight control issues coming second. A comparison of tactical UAV losses between US- and Israeli-operated vehicles showed consistent results - 26% of US TUAV losses are attributed to flight control issues versus 28% in Israel; propulsion-related losses are 37% and 32% respectively.
Although the Northrop Grumman RQ-4A Global Hawk loss rate (three vehicles in 3,308h flight time) is considered consistent with the single-seat combat aircraft mishap rate, the General Atomics RQ-1 Predator was singled out for attention in the study. "The US Air Force needs to take a hard look at the Predator B to incorporate lessons learned," says Weatherington. Predator mishaps per 100,000h were 34 versus 10.7 for the Boeing AV-8B, 6.2 for the Lockheed U-2 and 3.35 for the Lockheed Martin F-16 and 3.2 for the Boeing F/A-18. The OSD goal is 15-20/100,000h by 2010 for tactical systems.
The study recommends a renewed focus on precipitation, icing, wind and Reynolds number. "Raindrops do not scale [with size], and icing effects are very significant for any UAV we're looking at," Weatherington says. "We need better [aerodynamics design] codes for low Reynolds numbers, and we need to encourage more research because of the coming explosion in small UAVs."
Source: Flight International
