Sun Country B738 at Las Vegas on Feb 4th 2022, gear malfunction on departure
Last Update: March 22, 2023 / 11:45:38 GMT/Zulu time
Incident Facts
Date of incident
Feb 4, 2022
Classification
Accident
Airline
Sun Country
Flight number
SY-110
Departure
Las Vegas, United States
Destination
Minneapolis, United States
Aircraft Registration
N817SY
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
The FAA reported: "AIRCRAFT DEPARTED AND RETURNED, LANDED AND GEAR COLLAPSED, LAS VEGAS, NV."
The airline reported the right hand main gear malfunctioned.
On Mar 9th 2022 the NTSB released their preliminary report stating:
Sun Country flight 110 departed Harry Reid International Airport (LAS), Las Vegas, Nevada, about 0040 PST enroute to Minneapolis, Minnesota. After takeoff the crew moved the landing gear handle to the UP position to retract the landing gear, and subsequently received a red warning light for the right main landing gear (RMLG). The crew engaged the autopilot while they consulted the GEAR DISAGREE checklist. They placed the landing gear handle in the OFF position and the autopilot began retrimming the airplane, so they placed the handle back in the UP position. Subsequently, the crew reported hearing a loud sound from aft of the cockpit, so they declared an emergency and returned to LAS. During the approach the crew moved the landing gear handle to the DOWN position and received three green lights for the landing gear. During the landing, about 3 seconds after touching down, the RMLG collapsed. The airplane rolled right, and the right engine impacted the runway. The crew stopped the airplane on the runway and the passengers and crew deplaned using airstairs to a waiting bus. The airplane was then moved to the ramp.
Examination of the RMLG showed that the outer cylinder was fractured at the upper end between the forward and aft trunnions. A portion of the landing gear punctured the upper wing skin above the landing gear. The RMLG was removed from the airplane and the fracture surfaces were excised. The RMLG fractures were shipped to the NTSB Materials Laboratory for further examination.
On Mar 22nd 2023 the NTSB released their final report and their investigation docket concluding the probable causes of the occurrence were:
The fatigue failure of the right main landing gear initiated by liquid metal embrittlement by cadmium at arc burn locations in the outer cylinder tooling hole area. The arc burns were likely the result of operator error during stylus cadmium plating operations during overhaul.
The NTSB analysed:
Upon retracting the landing gear after takeoff, the flight crew received a right main landing gear (RMLG) red position indicator light, indicating that the RMLG was not in the up and locked position. The crew elected to return to the departure airport and the RMLG red indicator light remained illuminated until the crew selected the gear DOWN position for landing. During the landing roll, the RMLG collapsed, resulting in minor damage when the right engine impacted the runway. It is likely that the RMLG was partially fractured after takeoff which prevented it from retracting to the up and locked position.
Examination of the RMLG revealed that the outer cylinder fractured through a tooling hole. Examination of the fracture revealed the presence of fatigue cracking that initiated at the intersection of the tooling hole inner diameter and the outer cylinder inner diameter. Four areas of arc burn damage were identified in the tooling hole area, two of which were at the crack initiation sites. Cadmium identified at the intergranular separation initiation sites indicated the crack initiated due to liquid metal embrittlement by cadmium at the arc burn locations before propagating in fatigue.
The RMLG was last overhauled about 10 years before the incident, during which the outer cylinder was replated with cadmium after repair. It is likely that the arc burning in the tooling hole area was caused by a hand-held stylus cadmium plating operation performed in the tooling hole when the stylus (anode) made contact with the outer cylinder (cathode), initiating an arc. A nonconductive sleeve normally installed on the anode was either not present or deteriorated, allowing physical contact between the anode and cathode.
Ground observer video of roll out (Video: Nick Kastanes)
Aircraft Registration Data
Incident Facts
Date of incident
Feb 4, 2022
Classification
Accident
Airline
Sun Country
Flight number
SY-110
Departure
Las Vegas, United States
Destination
Minneapolis, United States
Aircraft Registration
N817SY
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
This article is published under license from Avherald.com. © of text by Avherald.com.
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