Confusion Preceded Denver Jet Crash, Controllers Say

DENVER — There was confusion in the airport tower during the half hour before the Nov. 15 takeoff of a Continental Airlines jetliner that ended in a crash during a snowstorm, air traffic controllers testified Thursday.

The testimony indicated that the confusion began when the cockpit crew of Flight 1713 failed to obtain clearance from the tower to taxi away from the passenger gate. The confusion was compounded as controllers lost track of the plane on the ground and mistook it for another aircraft.

One controller testified that as he handed the plane over to another controller about seven minutes before the crash, he remarked: “Seventeen Thirteen’s next for takeoff. I don’t know how he got there, but there he is.”

Contributed to Long Wait

The mix-ups are considered significant because they apparently contributed to the long wait--27 minutes by the latest estimates--between the time when the DC-9 was sprayed with alcohol at a ground de-icing station and the moment when it crashed after lifting off at Denver’s Stapleton International Airport, killing 28 of the 82 aboard.

Early testimony at the National Transportation Safety Board hearings here this week has indicated that a layer of ice--perhaps no more than .03 of an inch thick--may have accumulated on the plane as it waited in sub-freezing temperatures for takeoff.

And an expert from McDonnell Douglas, manufacturer of the plane, has testified that even a layer of ice that thin could have caused the plane to stall and crash as it did.

NTSB investigators say that under normal sequencing, planes at Stapleton request, and then receive, clearance from the tower before departing from a passenger gate.

Did Not Seek Clearance

However, controller Robert S. Tarbox testified Thursday that neither the pilot, Frank Zvonek, 43, nor the co-pilot, Lee Bruecher, 26, asked for clearance before Flight 1713 left the gate.

As a result, Tarbox said, he assumed the plane was still at the gate when, in fact, it had taxied to a Continental de-icing pad some distance away.

Tarbox said that when Flight 1713 called him a few minutes later to request clearance to leave the pad and head for the runway apron, he misunderstood the message and responded affirmatively, believing the plane was just leaving the gate.

For several minutes thereafter, the control tower stayed one step behind Flight 1713, which soon reached the apron of Runway 35 Left and began waiting for instructions to take off.

Meanwhile, another mix-up occurred. Continental Flight 594, a MD-80 jetliner that had requested clearance to go to the de-icing pad, was instead instructed by a controller to taxi to the runway apron.

Flight 594 neither questioned nor corrected the clearance, simply responding “Five ninety-four.”

Tries to Radio Plane

While Flight 1713 continued to wait for takeoff instructions, controller Charles E. Hess, who was handling takeoffs on the takeoff radio frequency and believed incorrectly that Flight 594 had moved to the runway apron, tried six times to raise 594 without success, according to his testimony.

After about five minutes of this, Flight 1713 finally broke in and said: “Denver tower, that number one Continental there at the runway is seventeen thirteen.”

Hess, who testified Thursday that his initial thought was that the pilot responding “didn’t know what his call sign was” radioed back after a confused moment, “Seventeen thirteen, are you an MD-80?”

“Negative, sir. A DC-9,” Flight 1713 answered.

“All right, thank you,” Hess answered a moment later.

It was Hess who said he then handed over control of the plane to the man who was taking over his shift, Steven W. Pelham, saying: “Seventeen Thirteen’s next for takeoff. I don’t know how he got there, but there he is.”

About seven minutes later, Pelham cleared Flight 1713 for takeoff, and the jet, which was headed for Boise, Ida., began accelerating down the runway.

A minute after that an inbound jet radioed the tower: “Somebody just . . . crashed on Runway 35 Left . . . big fireball. . . .”