History of Flight
The takeoff, climb, cruise, and descent were uneventful. The first officer was pilot flying for a visual approach and landing on runway 14 at Alexandria International Airport (KAEX). Flight data recorder data showed airspeed, attitude, and descent rate similar to previous landings. After landing, the right main landing gear (RMLG) cylinder fractured and collapsed aft, causing the airplane to settle onto the right wing and flaps. The crew stopped the airplane about 7,000 feet from the approach end and called for an emergency evacuation due to a suspected fire on the right wing.
Flight attendants opened the two forward and two aft doors. The escape slide at the left forward door (L1) did not deploy or inflate. Passengers and crew evacuated using the three doors with inflated slides. No injuries were reported.
Aircraft Information
The fractured RMLG cylinder (part number 5935355-501, serial number S1017) was installed on May 10, 2011 after overhaul in April 2011. Boeing released Alert Service Bulletin MD80-32A344 on March 31, 2003, with instructions for fluorescent particle and magnetic particle inspections of MLG cylinders. The FAA mandated inspections via Airworthiness Directive 2004-05-03, effective March 15, 2004, requiring repetitive inspections at intervals not exceeding 450 landing cycles.
The accident cylinder's last AD inspection was November 16, 2017, which was 218 landing cycles before the accident landing and 279 landing cycles since its previous inspection. Prior AD inspections occurred on March 30, 2017 (294 cycles since previous), November 1, 2016 (427 cycles), and February 29, 2016 (414 cycles).
The L1 escape slide (part number D29982-121, serial number 1091) was installed on January 25, 2018. The operator's maintenance program required visual inspections every 3 days, including bottle pressure checks. Twenty-two service checks were performed between installation and the accident, with no non-routine maintenance actions. Post-accident examination revealed the release cable had been pulled, the inflation valve was open, and the reservoir and valve assembly pressure gauge showed zero pressure.
Landing Gear Fracture Examination
The fractured RMLG was examined at a Boeing facility under NTSB direction. The circumferential fracture was oriented perpendicular to the longitudinal axis, about 30 inches from the cylinder bottom. Most of the fracture surface had a dull gray luster with rough texture and shear lips, consistent with overstress separation. Chevron marks and river patterns emanated from a small thumbnail crack on the forward side of the cylinder outer diameter. The thumbnail crack was 0.072 inch long and 0.035 inch deep, with crack arrest features and striations consistent with fatigue separation. No shear lips were present at the thumbnail crack.
A rectangular area around the thumbnail crack, about 4 inches longitudinally and 5 inches circumferentially, had a different surface finish. Examination found primer and paint, no cadmium plating, and scratch marks consistent with mechanical grinding. Some corrosion was present on the outer surface near, but not at, the crack initiation point. Material composition, microstructure, and hardness were consistent with specifications. No evidence of excessive mechanical grinding damage was found.
Fatigue striation counts at 14 areas estimated the crack had been present for 1,774 landing cycles. The estimated crack length at the November 16, 2017 inspection was 0.059 inch; at the March 30, 2017 inspection, it was 0.048 inch. The minimum detectable crack length stated in the service bulletin was 0.050 inch.
Escape Slide Examination
The L1 escape slide was examined at the manufacturer's facility under NTSB direction. The slide assembly was fully packed with no evidence of gas flow despite the inflation valve being open. The slide inflated normally with a pressurized reservoir. The reservoir and valve assembly had a slow leak through the rupture disk assembly, with three areas of surface corrosion on the sealing surface. Testing showed the slow leak would empty the gas reservoir over several months.
Additional Actions
After the accident, World Atlantic Airlines conducted a fleet campaign to reinspect all MD-80 MLG cylinders per the AD, retrained personnel on AD procedures, and revised task card procedures for MLG inspection. They also revised slide inspection procedures to ensure gas reservoir pressure was checked more regularly during service inspections and before each flight.