Pentagon unhappy about drone aircraft reliability: rising mishap rates of unmanned vehicles attributed to rushed deployments.

• Author: Peck, Michael

Crashes and component failures are driving up the cost of unmanned air vehicles and limiting their availability for military operations, said a Pentagon report. Of particular concern are those UAVs that have become useful tools of war--such as the Predator and the Global Hawk.

The reliability issue has sparked disagreements among military and civilian experts, amid congressional criticism that UAVs are becoming too expensive. Heating the controversy were comments by Air Combat Command chief Gen. Hal Hornburg at an Air Force Association conference in February. Hornburg dismissed the notion that UAVs are simple expendable vehicles. "Number one, we can't treat these things like disposable diapers and just throw them out," Hornburg said. "These things cost money, and it comes our of your treasury, just like it comes out of ours."

Hornburg put Predator's crash rate last year at 32.8 per 100,000 flight hours, and this year's at 49.6. "If you want to talk about Global Hawk, which we are measuring, the accident rate for the Global Hawk right now is 167.7. That is unsatisfactory."

The Defense Department's 2002 UAV Roadmap confirms a mixed history of Class A mishaps--those causing loss or severe damage to an aircraft--especially compared to manned aircraft. Officials noted, however, that comparing UAV mishap rates against manned aircraft may not be entirely fair, because commanders take risks with UAVs that typically they would not with piloted airplanes.

While the F-16 was recently assessed at a mishap rate of 3.5 per 100,000 flight hours,

* The RQ-2A Pioneer has a mishap rate of 363 per 100,000 hours, though the figure for the RQ-2B declined to 139.

* The RQ-5 Hunter racked up a mishap rate of 255 for pre-1996 aircraft, but it has plunged to 16 since.

* The Predator RQ-1A had a mishap rate of 43, and the RQ-1B 31, according to Defense Department figures.

"The mishap rate for large UAVs should be reduced to less than 25 per 100,000 hours by 2009 and less than 15 by 2015," recommended the report, which did not set specific goals for smaller UAVs, citing a need for further research into factors affecting their aerodynamics. It did suggest examining a retrofit of Predator B components on the more crash-prone Predator A, standardizing reliability measurements between all services and incorporating all-weather capability into future designs.

However, some Air Force officials question the validity of the Defense Department's statistics, particularly the 100,000-hour statistical benchmark, which was derived by combining the flight hours of...