For the second time in as many days, a U.S. Patriot missile defense battery has apparently locked its sights on an allied fighter plane, raising concern about a potentially serious glitch in the system's targeting software.
U.S. defense officials said yesterday that a Patriot system about 30 miles south of the Iraqi city of Najaf apparently "locked on" to an Air Force F-16 fighter Monday and prepared to fire. The F-16 responded by firing a high-speed anti-radiation HARM missile at the battery, destroying its radar dish.
No one was injured in the strike -- and the F-16's response might have saved the crew's lives. But it came a day after a Patriot missile shot down a British Royal Air Force Tornado GR4 fighter near the Kuwaiti border, killing both crew members. The British fliers were the first known friendly fire casualties of the war in Iraq.
Defense officials at the Pentagon and at the air command center at Prince Sultan air base in Saudi Arabia were divided about the significance of the two incidents, both of which are under investigation. An Air Force official in Saudi Arabia cautioned that it is not yet certain that the Patriot had the F-16 in its sights or whether the aircraft was detecting Iraqi anti-aircraft radar.
A defense official in Washington was similarly cautious about blaming the Patriot.
"Error on the battlefield is more often than not human error," the official said. "I wouldn't want to pin this on anyone yet."
But other Pentagon officials and independent weapons experts were far less circumspect.
"It's obviously a software glitch," one defense official said. "Jets go fast, but there's no way they should be mistaking them for a Scud going supersonic."
The details of both incidents raise doubts that human error could have been at fault, defense technology experts said. In Monday's incident, the Patriot battery -- moved north to protect 3rd Infantry Division troops speeding toward Baghdad -- was taking heavy mortar fire, a defense official in Saudi Arabia said. So the Patriot crew took cover, leaving the missile battery operating largely on automatic. Taking cover might have saved the crew from the U.S. missile, but it also indicated that the Patriot system, not human error, targeted the F-16.
Defense Secretary Donald H. Rumsfeld said on Sunday that the downing of the British aircraft earlier in the day might have been caused either by a problem with targeting recognition equipment or because the British aircraft was not beaming the proper signal indicating it was friendly.
But John Pike, a defense technology expert at GlobalSecurity.org, said the Tornado would have been tracked by multiple air defense systems as it returned to Kuwait, and only the Patriot fired.
"There is evidently a problem," Pike said.
The Patriot was used to little avail against Scud missile attacks during the 1991 Persian Gulf War, but since then, the system has had three major upgrades, according to an assessment released yesterday by the Center for Defense Information.
So far, the more advanced Patriots have been considerably more effective. Fourteen Iraqi missiles have been launched at U.S. forces in Kuwait since the war began, and the Pentagon has said six were intercepted.
The good news, Pike said, is, "Well, Patriot works." But he added that the system may be too good at interception.
Victoria Samson, the author of the Center for Defense Information analysis, said that in February 2002, a Patriot operational test failed when an electrical overload briefly blinded the radar, just long enough to interfere with targeting. The problem could be recurring, she said.
The Patriot system is far too important for the two incidents to take it out of action, Pike said. Patriot technicians will be scrambling to determine if there is a problem and, if so, repair it quickly.