The US National Transportation Safety Board has released an update on the investigation into the Southwest Airlines incident of the 17th April that resulted in the death of passenger Jennifer Riordan, a 43-year-old mother-of-two.
The report details that at 11.03am local time, on 17th April a Southwest Airlines Boeing 737-700, registration N772SW operating flight 1380, experienced a failure of the left CFM International CFM-56-7B engine and loss of engine inlet and cowling as the aircraft was climbing and had reached an altitude of around 32,000 feet.
It was fragments from the engine inlet and cowling that struck the wing and fuselage, which caused a rapid depressurization after the loss of one of the windows at row 14. The aircraft suffered substantial damage and the crew decided and performed an emergency landing at Philadelphia.
The NTSB's initial examination of the aircraft found that the majority of the inlet cowl was missing,
including the entire outer barrel, the aft bulkhead, plus the inner barrel. The No.13 fan blade had separated at the root; the dovetail remained installed in the fan disk and upon further investigation and examination found fatigue fracture features emanated from multiple origins in the fan blade. No other fan blades exhibited any fatigue cracks when they were examined.
The accident engine fan blades had accumulated more than 32,000 engine cycles since new, had been periodically lubricated as per the maintenance manual and according to Southwest's records, the fan blades were last overhauled some 10,712 engine cycles before the accident. Following this, the NTSB then recommended all fan blades in CFM International CFM 56-7B-series engines that had accumulated 20,000 engine cycles be examined and checked.
It was part of the inboard engine cowl that struck the window at row 14, the window was entirely missing and no window, aeroplane structure, or engine material was found inside the cabin.
According to the report the NTSB had interviewed the Southwest staff on the flight and they reported a loud sound could be heard and experienced vibration. It was then that oxygen masks automatically deployed throughout the cabin. The flight attendants retrieved portable oxygen bottles and began moving through the cabin to calm passengers and assist them with their masks. As they moved toward the mid-cabin, they found the passenger in row 14 partially out of the window and attempted to pull her into the cabin. Two male passengers helped and were able to bring the passenger in.
During interviews, the flight crew stated the climbout from LaGuardia was normal with no indications of any problems; the first officer was the pilot flying and the captain was the pilot monitoring. They reported experiencing a sudden change in cabin pressure, aircraft yaw, cockpit alarms, and a “gray puff of smoke.” They donned their oxygen masks, and the first officer began a descent. Flight data recorder data showed that the left engine parameters all dropped simultaneously, vibration increased, and, within 5 seconds, the cabin altitude alert activated.
The FDR also indicated that the airplane rolled left to about 40 degrees before the flight crew was able counter the roll with control inputs. The flight crew reported that the airplane exhibited handling difficulties throughout the remainder of the flight. The captain took over flying duties and the first officer began running emergency checklists. The captain requested a diversion from the air traffic controller; she first requested the nearest airport but quickly decided on Philadelphia. The controller provided vectors to the airport with no delay.
The flight crew reported initial communications difficulties because of the loud sounds, distraction, and wearing masks, but, as the airplane descended, the communications improved. The captain initially was planning on a long final approach to make sure they completed all the checklists, but when they learned of the passenger injuries, she decided to shorten the approach and expedite landing.
