The right engine (in red circle) of Jeju Air Flight 7C2216 (Boeing 737-800) appears to be open for reverse thrust during an attempted belly landing at Muan International Airport, Sunday. Captured from video provided by a reader

A range of questions has emerged regarding the Jeju Air passenger plane crash that occurred on the morning of Dec. 29 at Muan International Airport in South Jeolla Province. Key issues include whether the engine's reverse thrust was engaged during the emergency landing and why the plane did not jettison fuel before the accident.

A former commercial pilot and aviation experts analyzing video footage from the crash said it is likely the engine reverse thrust was activated. However, they noted a weak correlation between the absence of fuel jettisoning and the scale of the crash's impact.

Was reverse thrust activated?

Of the 181 passengers and crew aboard, 179 lost their lives when the plane slid off the runway during an emergency belly landing, eventually colliding with a concrete structure holding the localizer antenna. The absence of landing gear, which plays a critical braking role, was cited as the primary cause.

However, questions remain about whether auxiliary speed-reduction mechanisms, such as flaps, spoilers, or reverse thrust, were properly deployed.

A former commercial pilot said, "Crash footage and photos show the engine covers were open, indicating that reverse thrust was engaged. While it cannot be ruled out that the covers opened due to the impact, it seems more plausible that the captain activated reverse thrust during the emergency."

A family member of a passenger mourns near the site of a Jeju Air crash at Muan International Airport in South Jeolla Province, Monday. Yonhap

Why wasn't fuel jettisoned?

Another factor cited in the scale of the crash was the lack of a fuel jettison system on the Boeing 737-800 aircraft.

Some have argued that if the aircraft had been equipped with a system to release fuel quickly mid-air, it could have reduced the braking distance and mitigated the explosion caused by the collision.

The Jeju Air passenger plane burst into flames after overrunning the tarmac and colliding with the localizer antenna.

However, experts believe the fuel level may not have significantly influenced the outcome. The plane, which flew from Bangkok's Suvarnabhumi Airport to Muan Airport, had already consumed a large portion of its fuel.

A retired air force expert said, "Most aircraft assigned to short regional routes, like this one, are not equipped with fuel jettison systems. Even if some fuel was reserved for go-around attempts, it is unlikely the aircraft exceeded its maximum landing weight."

Search operations for personal belongings are underway at a Jeju Air crash site at Muan International Airport, Monday. Yonhap

Why was landing gear deployment impossible?

While bird strikes are considered a probable primary cause of the crash, several questions remain unanswered. Investigators must determine the specific malfunctions caused by the bird strike.

Additionally, they need to examine why the aircraft only completed a partial turn and landed in the middle of the runway instead of executing a full go-around.

The failure of all three landing gear systems also requires clarification. Although a bird strike could have damaged the hydraulic system controlling the landing gear, experts noted that alternative systems, such as electronic or manual methods, should still have allowed the gear to deploy.

Kim Gyu-wang, head of flight education at Hanseo University, said, "If the hydraulic system fails, operating the control stick becomes significantly more difficult for the pilot. The investigation must uncover why deploying the landing gear within a short timeframe proved to be impossible."

Chrysanthemums are placed outside the fence near a Jeju Air crash site at Muan International Airport, Monday. Yonhap

Black box analysis

The investigation into the Jeju Air crash hinges on the analysis of the aircraft's black box. The black box comprises a cockpit voice recorder (CVR), which captures communications, and a flight data recorder (FDR), which logs the aircraft's operational status.

While the CVR remains intact, the FDR's connector, necessary for analysis, is missing. If the damage to the black box makes it difficult to analyze, decoding and publishing results could take over six months, as the device must be sent to the U.S. National Transportation Safety Board (NTSB) for processing.

Authorities transported the retrieved black box to the testing and analysis center at Seoul's Gimpo International Airport. The investigation team includes four experts from the NTSB and Boeing, the aircraft's manufacturer. A comprehensive safety inspection of all Boeing 737-800 aircraft in South Korea is also underway.

The Boeing 737-800 is primarily used by domestic low-cost carriers. Jeju Air operates the largest fleet with 39 aircraft, followed by T'way Air with 27, Jin Air with 19, Eastar Jet with 10, Air Incheon with 4, and Korean Air with 2, for a total of 101 planes in operation.

This article from the Hankook Ilbo, a sister publication of The Korea Times, is translated by a generative AI and edited by The Korea Times.