Pentagon unhappy about drone aircraft reliability: rising mishap rates of unmanned vehicles attributed to rushed deployments.
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 Predator, Pioneer and Hunter, rather than focusing on each individually. "Predator has only reached about 65,000 hours. Global Hawk is only at about 2,500 hours. You are nowhere near where you can statistically try to project what your mishap rare is fur 100,000 hours," said Lt. Cal. Douglas Boone, deputy chief of the Air Force's Airborne Reconnaissance Division.
Although 27 out of 80 Predators have been lost due to combat and non-combat causes, Boone told National Defense the program is almost where it should be, with a crash rare of one every 1,900 hours, compared to an initial program goal of one crash no more than every 2,000 flight hours. He believes the mishap rate is skewed because Predators were sent to Bosnia lacking spare parts, maintainers and adequately trained operators.
Similarly, Boone blames the Global Hawk's crashes, which have claimed four of six prototypes, on hasty deployment to theaters such as Afghanistan. Accolades earned during Operation Enduring Freedom have obscured the fact that the Global Hawk is still in the development stage. "In normal times, it would never have been deployed," added Boone.
Even determining why a UAV is lost on a mission is difficult. "If it doesn't return, did we get shot down, or did we have a normal mechanical failure?" Boone asked.
Brad Brown, president of the Association for Unmanned Aerial Aircrafts International, said that reliability will determine further acceptance of UAVs. "According to several senior officers, who wouldn't admit it publicly, the reason they were against the use of some of these platforms, including Global Hawk, was reliability. It isn't just a matter of cost. It boils down to a matter of capability. If you only have two, and you lose one, there goes 50 percent of your capability."
Agreeing that UAV reliability should improve is easy, but how this will be accomplished is another matter. Cost is a concern. More redundancy of flight control systems boosts reliability, but beyond a certain threshold, they negate the UAV cost advantage over manned aircraft, the Pentagon report noted. Similarly, the absence of components needed for manned aircraft make UAVs cheaper, but also affect reliability. And if reliability is overly compromised, then high attrition will require more UAVs to be acquired, thus negating the cost savings. The report recommends focusing improvement efforts on UAV flight control systems, propulsion and operator training, which account for 80 percent of mishaps. It suggests possible remedies such as decreasing maintenance requirements by substituting electrical for hydraulic systems, and digital for analog sensors.
Redundancy is difficult to add to smaller UAVs, but larger aircraft, such as the Global Hawk, have dual redundancy flight control systems and communications, which add reliability but also cost and weight. Triple redundancy is an even more expensive option. "If you make UAVs too expensive or too capable, now you're going to say that you can't afford to lose them. You have a Hobson's choice," said Timothy Beard, a retired admiral and aviator who is now Northrop Grumman's director of business development for unmanned vehicles.
Boone foresees UAVs with more sophisticated guidance systems that will enable them to do more than return to their launch point if there is a problem. "With more power in the computer, you can give it more complex instructions like, 'in an emergency, fly to emergency landing field A."'
Brown points to Athena Technologies' "fault tolerant" approach that equips a UAV with an autonomous capability to respond to failures. Frequently operators on the ground cannot determine if or where a UAV has experienced a failure, said David Vos, chief technology officer. Athena's control system uses onboard sensors to detect malfunctions such as in the rudder, which the aircraft's computer then compensates for by adjusting other flight controls.
UAV reliability affects more than military use of unmanned vehicles. Iris also key to convincing both the Federal Aviation Administration to relax its restrictions on UAVs flying in civilian airspace, and foreign governments to allow overflight and landing rights.
Brown warned that FAA approval will not be forthcoming unless unmanned vehicles approach the reliability of manned aircraft. Boone expects that in the wake of last year's collision between a Russian passenger jet and a DHL cargo 757 over Switzerland, international agreements governing international flights will require aircraft to carry both radar and optical collision avoidance systems. "Our UAVs are going to have to be compliant with that, too. If you have a Global Hawk flying over Switzerland and it encounters another aircraft, it must deconflict automatically."
Though it has no jurisdiction over military UAVs and their operators, the FAA does require Certificates of Authorization for flying in controlled airspace. Even though UAV supporters point out that Global Hawk operates at 60,000 feet, well above the altitude of commercial flights, FAA spokesman William Shumann replied that the UAV may ascend or descend through passenger jet altitudes during its missions.
Filing a flight plan ran rake up to 60 days, and there are currently about 30 of these certificates, with about three-quarters awarded to military UAVs such as Global Hawk, according to Shumann. Military users wants to file and fly on the same day, and the Air Force's Boone predicts that Global Hawk will be permitted to do this within two years.
RELATED ARTICLE: Global hawk crashes: who's to blame?
Mishaps that destroyed or badly damaged four out of seven Global Hawk prototypes resulted from errors or decisions made by Air Force operators, said the Global Hawk manufacturer, Northrop Grumman Corp.
Though Air Force statements generally match Northrop Grumman's version of events, the manufacturer claims that the crashes were preventable, and do not reflect any flaws in the Global Hawk's design.
Without disputing the findings of the Air Force's accident boards, which mostly suggest manufacturer responsibility, Northrop Grumman argues that there is another side to the story. "We look much better than many people think," said Timothy Beard, Northrop Grumman's director of business development for unmanned vehicles.
For its part, the Air Force declined to provide additional information on the incidents, beyond what already was published in news releases and accident reports.
The Air Force said that a March 1999 mishap occurred when a Global Hawk controlled by operators at Edwards Air Force flew so high that it lost the Edwards signal and inadvertently responded to a termination signal emanating from Nellis Air Force Base. In a December 1999 incident a Global Hawk was badly damaged when it overran the runway during a taxiing test. The Air Force investigation blamed it on a combination of known software problems between the aircraft's mission planning systems. Beard said operators ignored Northrop Grumman's warning that a ground speed of 155 knots was excessive given the length of the Edwards AFB runway and the aircraft's braking capacity.
The two most recent crashes occurred over Afghanistan in December 2001 and July 2002. According to an Air Combat Command Accident Investigation Report, the primary cause was structural failure of the right V-tail and rudder-elevator assembly, due to a control rod bent "by coming in contact with an improperly installed actuator nut plate bolt." Beard acknowledged that the problem was mainly "due to maintenance manufacturing and installation error." Yet, he also said that it was not fatal, and that the Global Hawk could have been saved had Air Force rules of engagement allowed the operators to divert it to bases in nearby friendly nations, rather than returning it to its launch point after the problem was detected.
If the aircraft had been a manned U-2, it would have been diverted to the first available base, Beard said. He added that the Global Hawk managed to fly 6.5 hours after the tail mechanism failed, but crashed during landing.
For a July 2002 mishap, Air Force investigators blame an engine malfunction on "failure of a single fuel nozzle in the high-flow position that eventually caused internal failure of the engine," leading to a crash during an attempted emergency landing. Beard counters that although operators did not know why the Global Hawk was losing altitude--because the aircraft's telemetry did not indicate a reason--they should have stopped running the engine at 100 percent power.
"Most of us who have flown airplanes realize that if something like this happens, and I'm not getting any information as to why, we've got a problem, and we had better bring it on home and reduce the throttle," said Beard, a retired admiral and naval aviator. As with the previous mishap, the aircraft could also have been diverted to a friendly country, Beard added.
He said that it was ironic that the reliability goals initially set for Global Hawk by the Defense Advanced Research Projects Agency were too low. "Predicted Global Hawk reliability exceeds those goals today," he said, estimating reliability at the current test stage at 9.5 per 100,000 flight hours, and rising to 5.1 when Global Hawk enters production. Two are scheduled to be built this year, four next and then six every subsequent year. Beard estimated the cost of production models at about $35 million, though other estimates put the price tag as high as $50 million, depending on the sensor package.
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|Date:||May 1, 2003|
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