By David Shepardson
WASHINGTON (Reuters) -The loss of an engine cover on a Southwest Airlines Boeing 737-800 on Sunday that fell off during takeoff in Denver and struck the wing flap was the result of a maintenance issue, the chair of the National Transportation Safety Board (NTSB) said on Wednesday.
NTSB Chair Jennifer Homendy told reporters after a Senate hearing the airplane had been in for maintenance the night before the incident in which it lost the engine cowling.
“It’s a maintenance issue,” Homendy said, adding the board opted not to open a formal investigation. The NTSB had sent a structural engineer who lives in Denver to look at the plane but was satisfied with its understanding of the incident.
“Southwest is addressing it,” she added.
Prior incidents involving engine cowling have been attributed to failure to latch the fan cowl doors. Homendy said in the Southwest incident “there may be some issues with how they latch to see whether they can tell if they’re locked or not. So they’re going through those procedures now.”
The Federal Aviation Administration, which is investigating, did not immediately comment on Wednesday. Southwest said it would “defer to the FAA due to the ongoing investigation into this incident.”
No one was injured and Southwest Flight 3695 returned safely to Denver International Airport around 8:15 a.m. local time (1415 GMT) on Sunday and was towed to the gate after losing the engine cowling.
The Boeing aircraft bound for Houston Hobby airport with 135 passengers and six crew members aboard climbed to about 10,300 feet (3,140 m) before returning 25 minutes after takeoff.
The plane entered service in June 2015, according to FAA records. Boeing referred questions to Southwest.
The 737-800 is in the prior generation of the best-selling 737 known as the 737 NG, which in turn was replaced by the 737 MAX.
The 737-800 is in the prior generation of the best-selling 737 known as the 737 NG, which in turn was replaced by the 737 MAX.
Boeing has come under intense criticism since a door plug panel tore off a new Alaska Airlines 737 MAX 9 jet at 16,000 feet on Jan. 5.
In the aftermath of that incident, the FAA grounded the MAX 9 for several weeks, barred Boeing from increasing the MAX production rate and ordered it to develop a comprehensive plan to address “systemic quality-control issues” within 90 days.
The FAA is investigating several other recent engine issues on Southwest’s fleet of Boeing planes.
The Justice Department has opened a criminal investigation into the emergency.
Homendy in March criticized what she called Boeing’s lack of cooperation and failure to disclose some documents, including on the door plug opening and closing, as well as the names of 25 workers on the door crew in Renton. After Homendy’s comments, Boeing provided the 25 names, and the planemaker said it was cooperating.
The NTSB plans to hold a public investigative hearing into the Alaska Airlines incident on Aug. 6-7.
Homendy said the hearing would include testimony from employees at Boeing and fuselage manufacturer Spirit AeroSystems and others like Alaska Airlines
NTSB Chair Jennifer Homendy on Wednesday said investigators were back at the 737 plant in Renton, Washington, this week for more interviews.
Aviation regulators stress that flying is incredibly safe and fatal accidents exceedingly rare. Federal investigations into air incidents are relatively common and do not necessarily suggest that safety is at risk. The National Transportation Safety Board has opened more than 100 investigations in the United States this year so far, involving multiple aircraft manufacturers. The incidents also do not necessarily indicate issues were caused by the manufacturer, with some responsibilities belonging to the airlines instead.
Still, the incidents have increased scrutiny of Boeing’s safety record, quality control protocols and the airlines that operate its jets. In a February statement, Boeing said it had “taken important steps to foster a safety culture,” and that it will “continue our comprehensive efforts to improve our safety and quality programs.”
Door plug blows off fuselage on Alaska Airlines flight
On Jan. 5, the door plug on an Alaska Airlines Boeing 737 Max aircraft blew out while it was ascending over Portland, Ore., leaving a gaping hole in the side of the fuselage and forcing an emergency landing.
The door plug — an exit sealed with a panel rather than used as a door — was found in a teacher’s backyard. The seat closest to the breach was empty and none of the passengers were seriously injured, although some claimed physical injuries and emotional trauma in a lawsuit against Boeing.
The accident prompted intense media scrutiny and several investigations, including a criminal probe by the Justice Department. The FAA grounded 171 737 Max 9 planes over safety concerns. In February, a NTSB investigation found that the panel appeared to have been installed at a Boeing factory without four crucial bolts.
“We are looking at other instances where a door plug was opened and closed to make sure that those records are available,” Homendy said at a U.S. Senate hearing, saying investigators want to make sure those other instances were documented.
Boeing, whose shares fell 2% on Wednesday, declined to comment on the interviews.
Last month, Boeing said it believed that required documents detailing the removal of the door plug in the Alaska Airlines plane involved in the emergency were never created.
Homendy said on Wednesday that Boeing and investigators still do not know the personnel who worked on the Alaska Boeing 737 MAX 9 that suffered the emergency. “This work occurred in September. They move a lot of planes through that factory,” Homendy said. “The biggest concern is missing records.”
At issue is the process not the individuals, she said. “This isn’t a gotcha on anybody,” Homendy said, adding the NTSB has still been unable to interview the door plug team manager, who has been on sick leave.
The door plug panel blew off the Alaska Airlines flight not long after the plane took off from Portland, Oregon, on Jan. 5.
Homendy said investigators are also looking at the planemaker’s safety culture. She said the NTSB could conduct a safety culture survey at Boeing.
Homendy said the planemaker was working well with the NTSB and providing documents sought. Boeing wants to understand what went wrong: “They want to know and they want to fix it,” Homendy said.
Following the incident, the FAA grounded the MAX 9 for several weeks, barred Boeing from increasing MAX production, and ordered the company to address systemic quality-control issues within 90 days after an audit found fault with the company’s manufacturing processes.
The NTSB said previously that four key bolts were missing from the door plug that blew out.
The Justice Department has opened a criminal investigation into the emergency.
Homendy in March criticized what she called Boeing’s lack of cooperation and failure to disclose some documents, including on the door plug opening and closing, as well as the names of 25 workers on the door crew in Renton. After Homendy’s comments, Boeing provided the 25 names, and the planemaker said it was cooperating.