Loss Of Hydraulics Led To Domino Effect

The National Transportation Safety Board has released a probable cause report, stating a Northwest Airlines captain's decision to shut down the left engine on a DC-9 was responsible for the jet's May 2005 ground collision with a Northwest Airbus A319 at Minneapolis-St. Paul International Airport.

As ANN reported, the DC-9 -- having lost its steering or braking capability as it taxied to the terminal building -- impacted the right wing of a much bigger A319 after running under the tail.

Four crewmembers on the DC-9 were injured, including the captain and first officer. Two ground workers were also injured in the incident. A section of the DC-9 roof peeled back and the A319 wing was damaged, spilling a puddle of jet fuel a few hundred feet wide. The 94 passengers on the DC-9 and 39 passengers on the A319 were evacuated.

The 16 mph impact occurred shortly after the DC-9's pilots became aware they had a problem with their right hydraulic system, according to Minnesota's Star-Tribune. 

According to the NTSB report, the left hydraulic system was operating properly and when the captain shut off the left engine after the plane landed in the Twin Cities, the "airplane experienced a loss of steering and a loss of brakes."

Northwest spokesman Bill Mellon said Tuesday that Northwest has developed an inspection procedure for its fleet relating to the rudder shutoff valve but declined to comment to the newspaper on other aspects of the NTSB report.

The NTSB probable cause reads: "the Captain's decision to shutdown the left engine during taxi with no hydraulic pressure on the right side hydraulic system to effectively operate the brakes, steering, or thrust reversers. A factor was the fatigue fracture of the rudder shutoff valve which resulted in the loss of right side hydraulic pressure."

FMI: www.ntsb.gov, www.nwa.com