Sophisticated System Failed to Identify Jet

The $525-million Aegis missile defense system used Sunday by the Navy to shoot down an Iranian airliner is among the most sophisticated weapons in the U.S. arsenal, but faced with an unidentified plane spotted so close and approaching so fast, it apparently was not sophisticated enough.

And the special characteristics of the Aegis system may prove to be a key factor in answering the central question posed by the tragedy: How could the U.S. ship, the cruiser Vincennes, fail to tell the difference between a two-man F-14 jet fighter and a commercial A-300 Airbus airliner that carried nearly 300 people?

‘Electronic Indications’

At a press conference, Adm. William J. Crowe Jr., chairman of the Joint Chiefs of Staff, said the Vincennes picked up “electronic indications . . . that led it to believe that the aircraft was an F-14.” He described the indications only as “electronic information which is classified and (which) I am not willing to discuss.”

The Aegis system, for all of its elaborate capabilities, was not designed primarily for the close-in conditions and short reaction times that prevail in the gulf, according to military experts.

At close range, the Aegis is no more effective in identifying threatening targets than the less-expensive, more-conventional electronic defense systems used on other missile-carrying ships, said Eugene J. Carroll, a retired rear admiral who is now deputy director of the Washington-based Center for Defense Information.

“The Aegis system was intended to reach farther out,” said Scott Truver, a private naval policy analyst. “For all intents and purposes, those guys had a couple of minutes to make up their minds” about shooting down the aircraft.

Of Aegis, electronics warfare expert James Bamford said, “Its main purpose was to act as a battlefield command post.”

Even the Navy acknowledges the Aegis’ limitations. “It does not solve all of our problems and it does not defy the laws of physics,” Crowe said, apparently referring to the fact that--given the range of modern air-to-ship missiles and the speed of the jet--the approaching Iranian plane posed a potential threat to the vessel.

Nine Miles Away

At the time the cruiser decided to fire, the Iranian plane was nine miles away, traveling directly toward it at 517 m.p.h. The aircraft was six miles distant when the missile struck it.

Complicating the problem of identification, according to the Pentagon’s account of the incident, was the head-on angle at which the airliner approached the Navy warship.

With that approach, “you’ve got a very small blip (on radar), and basically one blip looks like another blip,” said Andy Lightbody, editor of the Irvine-based International Defense Images magazine.

Without a positive identification by the Aegis system, several experts said, the Vincennes’ skipper in all likelihood relied on other factors in making the decision to fire on what turned out to be Iran Air Flight 655.

For example, several experts noted, the airliner took off from the Iranian airport at Bandar Abbas, a facility used for both military and commercial aviation.

And, they added, Capt. Will C. Rogers III undoubtedly had in the back of his mind the fate of the Navy frigate Stark, which was nearly sunk and had 37 crewmen killed when it was attacked in the gulf by an Iraqi jet fighter with an Exocet missile.

Much of what happened in the Persian Gulf on Sunday is still the subject of speculation.

For example, it is not clear whether the Iranian airliner was equipped with the device--a type of radio transponder--that is supposed to automatically identify the craft as a commercial aircraft. Even if it was so equipped, it is not known whether the transponder was functioning.

Classified Information

Meanwhile, the Pentagon has said there were other indications that contributed to the Vincennes’ conclusion that the Iranian airliner actually was a jet fighter, but it has refused to spell out what those indications were because they involve classified information.

Named after the mythical shield of the Greek god Zeus, the Aegis missile defense system aboard the Vincennes relies on state-of-the-art digital computers and radar signal processing equipment to throw a “deep defense” around naval task forces. It has been deployed on Ticonderoga-class guided missile cruisers since 1981.

At the heart of Aegis is a sophisticated radar system known as AN/SPY-1, which allows computers to simultaneously track as many as 100 aircraft flying as far as 2,000 miles away. Using radar and computers, Aegis can launch and guide missiles to targets, either aircraft or cruise missiles, within a range of about 300 miles.

But the electronic gear that Aegis uses to identify aircraft--the so-called electronic countermeasures suite--is essentially the same as that deployed in all other Navy ships capable of firing surface-to-air missiles.

According to Truver, Carroll and other experts, the countermeasures system identifies an aircraft by analyzing the electronic signals coming from it.

“It says, ‘Oh! This frequency and this pulse repetition says it’s a Foxbat (Soviet fighter) radar and I’d better worry about it,’ ” Truver said.

With sufficient time and enough signals from the incoming aircraft, the electronic countermeasures system usually can give its operators an accurate indication of what type of plane it has detected. But in the four minutes between the time the Iranian airliner first was identified as a threat and the time a decision had to be made to fire, it is doubtful that the computers aboard the Vincennes received enough information to make a positive identification, the experts said.

Gulf Is Like a ‘Lake’

“When you get into the Persian Gulf, a ‘lake,’ as Admiral Crowe described it, we’re operating five minutes from a destructive attack, and in that five minutes you are not very apt to get a clear-cut distinction between a hostile and a friendly aircraft,” Carroll said.

Of the Vincennes, Carroll added: “This ship is in the position where it can’t use the unique capabilities it’s been given, with Aegis radar and missiles, because it’s too close in, it’s in a lake, not an ocean.”

Reacting to Crowe’s comment about electronic indications that the plane was an F-14, several experts said the only electronic signals that might have come from both an F-14 and a commercial airliner would have been those emanating from a military radio altimeter adapted to commercial use.

“That seems to be a likely candidate,” Carroll said.

Even if the Vincennes’ electronics countermeasures system had received no information indicating that the incoming airplane was a hostile fighter, Navy officers might still have believed that they were facing an F-14 on a suicide mission, flying visually, with its electronic systems shut down, Truver said.

Iranians, he said, “have shown a proclivity to drive trucks with bombs into embassies. Why not an F-14?”

Crowe said the Vincennes sent out warnings on both military and civilian frequencies usually monitored by most aircraft. The warship warned the airliner three times on the civilian frequency and four times on the military frequency without receiving a response, the admiral said.

The warnings to the Iranian aircraft were issued in English, said Lt. Col. Keith Schneider, a Defense Department spokesman. Schneider said English is the officially recognized international language for communicating with aircraft.

AIRBUS AND F-14: A COMPARISON Airbus A-300 length: 177ft.5 in. Wingspan: 147ft. 1 in. Range: About 4,200 miles Passengers: Usually 267: maximum of 375 F-14 Tomcat Length: 62 ft. 8 in. Wingspan: 64ft. 1 1/2 in. Range: About 2,000 miles First flown: December 21,1970