"The Patriot system identifies hostile missiles through their flight profile and other characteristics, including the lack of an IFF response. The criteria programmed into the Patriot computer were based on the many different Anti-Radiation Missiles available worldwide, and were therefore very broad. ZG710’s flight profile met these criteria as it commenced its descent into Ali Al Salem. The Board considered that the criteria should have been much tauter, based on the known threat from Iraq, and concluded that the generic Anti-Radiation Missile classification criteria programmed into the Patriot computer were a contributory factor in the accident.
Patriot Anti-Radiation Missile Rules Of Engagement.
10. The Board concluded that the Patriot Anti-Radiation Missile Rules Of Engagement were not robust enough to prevent a friendly aircraft being classified as an Anti-Radiation Missile and then engaged in self-defence, and were thus contributory factors in the accident.
Patriot Firing Doctrine and Training.
11. Patriot crews are trained to react quickly, engage early and to trust the Patriot system. If the crew had delayed firing, ZG710 would probably have been reclassified as its flight path changed. The crew had about one minute to decide whether to engage. The crew were fully trained, but their training had focused on recognising generic threats rather than on those that were specific to Iraq or on identifying false alarms. The Board concluded that both Patriot firing doctrine and training were contributory factors in the accident.
Autonomous Patriot Battery Operation.
12. The Patriot crew were operating autonomously, with a primary role of protecting ground troops from missile attack, but the Rules of Engagement allowed the Battery to fire in self-defence. Because its communications suite was still in transit from the US, contact with the Battalion HQ and other units was through a radio relay with a nearby Battery, which was equipped with voice and data links to and from the Battalion HQ. The lack of communications equipment meant that the Patriot crew did not have access to the widest possible “picture” of the airspace around them to build situational awareness. The Board considered it likely that a better understanding of the wider operational picture would have helped the Patriot crew, who would then have been more likely to identify ZG710 as a friendly track, albeit one without a working IFF. The Board concluded that the autonomous operation of the Patriot battery was a contributory factor.
Patriot IFF Procedures.
13. IFF is a system designed to identify automatically whether or not a
particular asset, such as an aircraft, is a “friend or foe”; civilian Air Traffic Control also use it to identify and track aircraft. A signal is sent from the ground or air to the aircraft, which then replies. There are five different modes of IFF, which can work in parallel or alone. These include Mode 1 (an unencrypted code, which was used in Iraq by all the Coalition aircraft) and Mode 4 (an encrypted form of IFF).
14. Investigation showed that the Patriot Battery’s IFF interrogator for Mode 4 was working throughout the engagement period, but that Mode 1 codes were not loaded. The Board believed that autonomous operations without voice and data connections to and from Battalion HQ might have contributed to the difficulty the Battery had in receiving the Mode 1 IFF codes. The Board
concluded that the lack of IFF Mode 1 codes increased the probability of the
accident, and was therefore a contributory factor.