The Northwest Airlines jet that hit another Northwest plane at the Minneapolis-St. Paul International Airport on Tuesday night wanted a tow. But the DC-9 hit an Airbus A319 before it could be pulled to a gate.
"I know the Airbus was being towed out and the DC-9 was waiting reportedly for a tow in,'' said Mitch Gallo, an investigator for the National Transportation Safety Board. "I know there was a request for a tow and then following that we had the impact."
Gallo said the DC-9 suffered a failure of one of its two hydraulic systems.
"There was little or no hydraulic fluid in the right-hand system and normal fluid on the left," Gallo said.
With a normal fluid level on the left-side system, the crew should have had braking and steering control, he said.
"There are two systems on an aircraft for redundancy,'' Gallo noted. "The hydraulic system controls the landing gear, flaps, braking and steering. But there is redundancy. Failures have been anticipated in the design."
Nothing immediately before the flight or in the DC-9's recent maintenance records foreshadowed the hydraulic failure, he said.
Shortly after the DC-9 left Columbus, Ohio, for the Twin Cities on Tuesday, its crew noted low hydraulic pressure and fluid on the right-side system.
The DC-9 landed without incident and executed a 180-degree turn on the runway to head toward the G concourse on the Lindbergh Terminal, Gallo said.
He estimated the DC-9 hit the Airbus at about 15 miles per hour, moving it about 60 feet.
The DC-9 ran into a wing of the Airbus, which cut away the roof of the DC-9's cockpit. The Airbus' wing suffered major damage, leaking fuel into the DC-9 cockpit.
The NTSB still is gathering data and interviewing pilots, flight attendants and others who may help with the investigation, Gallo said.
"We have a lot of data to look at," he said.
Eight people received medical attention after the crash. The captain of the DC-9 remained in satisfactory condition at Hennepin County Medical Center on Thursday.
Transcripts of the pilots' conversations will be released when the NTSB releases its final report.
