Investigation update: Jeju Air jet had a functioning engine at the time of its crash.

According to a new update by South Korean investigators, a Jeju Air aircraft that crashed during an emergency landing in December after a bird struck could have continued flying on the damaged but still functioning engine after the pilots had shut down the other.

The Boeing 737-800 belly-landed on Muan Airport without its landing gear, overshot runway, and erupted in a fireball, after slamming against an embankment. All but two of 181 passengers were killed.

Although the investigators haven't yet released a final report on the worst air disaster to hit South Korea, information has started to surface about the planes two engines.

According to an update from investigators dated July 19, which was seen but not released publicly following complaints by victims' families, the left motor suffered less damage than the other after a bird struck, but it was shut down only 19 seconds later.

In a five-page report, investigators confirmed that the right engine had generated enough power to fly. The update also included photos of both engines after the crash.

The crew did not give a reason for their actions and it is expected that the investigation will last several months, as investigators reconstruct both the technical state of the plane and what its pilots understood.

Experts warn against placing too much emphasis on incomplete evidence. They say that most air accidents can be attributed to multiple factors.

More Questions

The public has so far focused its attention on the possibility that crew members may have accidentally shut down a less-damaged aircraft engine. This brought back memories of a 1989 Boeing 737-405 crash in Kegworth (England) where pilots mistakenly shut down a nondamaged aircraft engine.

Multiple changes were made to the regulations in response to this disaster, including improved crew communication and emergency procedures.

Sources told reporters on Monday that South Korea's investigation had "clear proof" that the pilots shut off the left engine that was less damaged after the bird struck. They cited the cockpit voice recording, computer data, and a switch that had been found in the wreckage.

The latest information on the crash raises the possibility, however, that the heavily damaged engine still running may have been able to keep the plane in the air for longer.

The report did not specify what level of performance was left in the engine, or what additional options it might have provided to the emergency crew of the plane before it reverted back and landed with the landing gear raised on the opposite side of the runway than its original plan.

Both engines had bird strike damage, and both experienced vibrations following the strike. The Korean-language update of South Korea's Aviation and Railway Accident Investigation Board, ARAIB, said that the right engine had significant internal damage. However, it did not mention the damage found in left engine.

When shown the document, former U.S. National Transportation Safety Board Investigator Greg Feith said that the update didn't say how the left motor was operating or the state of the systems connected to either engines.

He said that the document contains some new information but leaves out much more. This results in a "cryptic".

ARAIB did not respond immediately to a comment request. The ARAIB plans to release a final report in June next year.

Experts in safety say that it's common for early reports of investigations to have sparse information and limited analysis.

In a preliminary report published in January, it was reported that feathers and bloodstains from ducks had been found in both engines.

The report stated that the engines, made by CFM International and jointly owned by GE France and Safran, were examined in May. No defects or fault data was found, other than bird and crash damages.

The families of those killed in the accident were informed about the findings regarding the engines, but they asked that the investigators refrain from releasing the report dated July 19, claiming it seemed to assign blame to the pilots while ignoring other factors.

South Korean media received copies of the report despite it being withheld. Boeing and GE referred all questions regarding the crash to ARAIB. Safran didn't immediately respond to an inquiry for comment.

Jeju Air previously stated that it was cooperating with ARAIB, and that they were awaiting the publication of their investigation.

Civil air investigations are conducted in accordance with international aviation regulations to determine the causes of crashes without blaming or putting anyone at fault.

The Jeju Air Pilots' Union said ARAIB "misled the public" when it suggested that there was no issue with the left motor, given that bird remains had been found in both.

Sources who attended the briefing said that investigators informed family members of the black box data indicating the left engine experienced a "surge" as well.

The pilot union, as well as representatives of bereaved family members, have requested that any evidence supporting any conclusions be made public.

Safety experts say that the embankment with navigation equipment is likely to have contributed to the high death rate.

According to global aviation standards, any navigation equipment installed along runways must be mounted on structures that are easily deformable in the event of an impact with an airplane.

The South Korean transport ministry identified seven airports in the country, including Muan Airport, that have structures made from concrete or steel rather than materials which break apart when struck, and said they will be improved.

A ministry official said last week that the designs for new structures were in progress.

(source: Reuters)