NTSB: Ineffective rudder in slick braking led to Delta runway accident
WASHINGTON – A Delta Air Lines flight veered off a snow-covered runway while landing at New York’s LaGuardia airport in 2015 because the captain's excessive reversing of the engines while braking rendered the rudder ineffective, federal investigators announced Tuesday.
Despite the lack of serious injuries on Flight 1086 on March 5, 2015, a slow evacuation and a mistaken passenger count each raised concerns among members of the National Transportation Safety Board. The MD-88's public-address system stopped working after the accident because the batteries were damaged.
“We are fortunate to have gained these insights without any loss of life and only minor physical injuries,” said Christopher Hart, the board chairman. “This was a very close call.”
Delta said it respected the findings, conclusions and recommendations of the investigation.
"Delta Air Lines' top priority is always the safety of our customers and employees," said spokesman Morgan Durrant. "Delta leaders will use this NTSB guidance to further enhance the safety of our global operation."
The plane left the runway about 14 seconds after the landing gear touched down; it came to rest about 5,000 feet down the runway atop a berm along the waterfront of Flushing Bay. The plane’s left wing was leaking fuel because it was damaged from colliding with a perimeter fence.
Investigators found that this type of aircraft has engines on the fuselage located close to the vertical stabilizer on the tail so when thrust is reversed excessively for braking, the effectiveness of the rudder decreases.
The problem is called “rudder blanking,” which provides little or no directional control, depending on the conditions. The problem doesn’t occur on dry runways but is a greater risk at higher speeds on slick runways, investigators said.
Other planes landed safely that morning in a half-mile visibility with snow and mist, and investigators said there was plenty of room on the runway for them to stop.
“Stopping was not a concern,” said Dan Bower, the board’s investigator in charge of the accident. “This was more of a directional-control accident.”
The pilots had outdated information about runway conditions with a quarter-inch of snow on the ground at LaGuardia, a note that was at least two hours old. The Port Authority of New York and New Jersey, which runs the airport, agreed to update condition reports at least hourly.
The board recommended that the Federal Aviation Administration work with Boeing and airlines to determine the best practices to prevent rudder blanking.
Despite the fuel leak, passengers only began leaving the plane by the right-wing exit 12 minutes after coming to halt, investigators found. Evacuation drills typically aim to empty a plane within 90 seconds.
The pilot called for evacuation 6 minutes after coming to rest, but flight attendants allowed passengers to retrieve warmed winter clothes from overhead bins, investigators found. It took 17 minutes to fully evacuate the plane, investigators said.
The board found that the crew was inadequately trained to evacuate the plane in an emergency and without standard communications equipment. Airlines should better train flight attendants for staying at their assigned exits during an emergency and learn how to cope with a lack of communications equipment, the board recommended.
The flight had two pilots, three flight attendants and 127 passengers, although two lap children weren’t counted in the initial evacuation because they hadn’t been issued boarding passes. The crew initially thought there were 125 passengers during the evacuation.
Board staffer Emily Gibson, who investigated survival factors in the crash, said the board asked the FAA to clarify its regulations about passenger manifests to make sure the lists are accurate.