PARIS, Sept 29: The Pentagon has covered up major flaws in the US Army's Patriot missile system that prompted a battery to shoot down a British Tornado during the Iraq invasion last year, a top US scientist says.

Theodore Postol, professor of science, technology and national security policy at the Massachusetts Institute of Technology (MIT), says "every one" of the claims made by a Pentagon probe into the shoot down was false.

Postol led an MIT research group to analyse the success of the Patriot systems in the first Gulf war. After that conflict, the US Army claimed the Patriots had intercepted 96 percent of the Scuds they had engaged.

"The real intercept rate was almost certainly zero. Now we have discovered a similar but far more insidious cover up following Operation Iraqi Freedom," says Postol, in a commentary published in next Saturday's issue of the British weekly New Scientist.

The Royal Air Force (RAF) ground-attack Tornado, Yahoo 76, was shot down by a Patriot air and missile defence unit over Kuwait on March 22, 2003 as it descended with another Tornado along a pre-planned "safe" corridor towards its home base west of Kuwait city. Both airmen were killed.

In its much-delayed investigation into the Tornado incident, the US Department of Defence concluded the mistake was caused "in major part" by incorrect setting of the plane's Identification Friend or Foe (IFF) system.

The IFF is an electronic system that tells defence crews and other aircraft that the plane is friendly, not hostile. The Pentagon also said the Patriot battery detected what appeared to be a hostile Iraq missile heading directly towards it.

The "missile", though, turned out to be the Tornado. However, according to the report, the allied integrated defence system did not work correctly and failed to identify it.

"We believe that every one of these claims is false," Postol says. By sifting through the data in the appendix in the report, Postol says he discovered that the "missile" signal received by the Patriot unit was a "ghost" - an illusory signal that was probably generated by electronic inference from other Patriot units nearby. And far from the assertion that the "missile" was heading towards the unit, this false target was in fact heading towards a troop encampment 15 kilometres (10 miles) to the north.

Had it been heading towards the unit, the battery's weapons control computer would have classified it as a Category 1 Air Threat. Instead, it was tagged as Category 9, a threat level so low that the computer did not even mark it for engagement, says Postol.

Still, believing they were under attack, the Patriot crew fired an interceptor missile at the false target, which by this stage had "moved" in the area of the two Tornados. Lacking any other target, the missile's radar homed in on one of the planes and blew it up.

In addition to the false signal problem, the Patriot battery did not have high-speed data links that would have enabled it to "talk" to the rest of the air defence system.

"Unbelievably, the communications module needed for the data links had not been shipped with the rest of the equipment," says Postol. "This was a crucial error. Had the links been working, the Patriot battery would have known from other units that the target it was tracking was a ghost" and that Yahoo 76 was friendly and flying down a safe approach corridor, he says.

Eleven days after the Tornado was shot down another Patriot crew fired at another false target, destroying a US Navy F-18, killing its pilot. The US Army has yet to release its report into this incident. -AFP