Page:Iran Air Flight 655 investigation.djvu/7

  the hooked target automatically, in order to continue interrogating Flight 655 the range gate had to be changed manually to track with the contact.

(U) Was it a critical error? No. Even if the Commanding Officer had been informed that there was no Mode II indication, that information alone has little significance. An attacker could easily be either squawking Mode II or no mode if he believes it will camouflage his identity. On 18 April, Iranian F-4s that were threatening U.S. units did not squawk any mode throughout that day. Combined with other pieces of information, a Mode II indication may help a Commanding Officer confirm or disaffirm a conclusion, but when under threat it is not definitive but only one piece in the puzzle. (U) The Commanding Officer did not put emphasis on the air corridor being 20 miles wide. In fact, his experience in the Gulf suggested that commercial aircraft normally tried hard to stay directly on the center line. He believed that 3 to 4 miles off the center axis was unusual and should be considered. In actual fact, however, it is again a peripheral point. An attacker would probably prefer to be in an air corridor if it confused his target. The Persian Gulf is blanketed by air corridors; they cover over 50% of the Gulf. Being in an air corridor is secondary information at best and must be combined with altitude, voice transmissions, etc., to be conclusive. (U) By far the most puzzling mistake to me was the ultimate misreading of altitude. The investigation established that the range and altitude information passed to the Commanding Officer was correct until the contact reached approximately 15NM. The time was 0653:45Z. Shortly thereafter, at a range between 15 and 12 miles, the Tactical Information Coordinator (TIC) reported that the altitude (which he estimated had previously reached 11,000 feet) was decreasing. At that moment, the Commanding Officer was rapidly reaching a point of no return with his Standard missiles and was inside the potential Iranian air-to-surface missile threat envelope. The TIC testified that he reported declining altitude at 11 miles, possibly 10 miles, and at nine miles. The last report was given as the missiles went off the rail and played no part in the process--the firing order had been given a few seconds earlier at 0654:05Z. Actually, the investigation concluded that the time from the first report of decreasing altitude to the decision to fire was in the neighborhood of 20 to 30 seconds.

(U) The investigation was unsuccessful in satisfactorily reconciling the conclusion that the contact was descending with subsequent data analysis. The TIC's belief, however, was supported by three other watchstanders, although it is not clear that they had arrived at that conclusion independently.

(U) It is impossible to say with assurance how the decreasing altitude information bore on the Commanding Officer's final decision. Obviously, whether the aircraft was ascending or descending could, when taken in the overall context, be a "significant indicator." It should be borne in mind, however, that an aircraft even at a range of 9 miles and altitude of 13,000+ feet (actual altitude at time of firing) was at sufficiently low 