Sunday, July 07, 2013

Boeing 777 safety questions after SF crash

Safety concerns have once again been heighten concerning the Boeing 777 after a San Francisco bound plane crashed as it came into land at the city's main international airport.

Two people were declared dead following the crash of Asiana Airlines Flight 214. The plane, which had flown from Seoul in South Korea with 291 passengers and 16 crew on board, appeared to strike the runway as it came into land just before 11:30 local time [18:30 GMT].

The cause of the crash was not immediately known, but there will be questions as to whether the plane's fly-by-wire systems were at fault or if a mechanical system failed. There may too be questions over what caused the fire which tore through the main fuselage. Weather conditions were fine and there was little wind, so there are strong indications that there was a fault with the aircraft itself.

Meanwhile authorities discounted a terrorist attack and handed the case to civil aviation investigators.

Eyewitness accounts

One witness to the crash, Ki Siadatan, said the plane "looked out of control" as it descended into San Francisco International Airport. Watching the events unfold from the balcony of his home in the Millbrae area of San Francisco, he told the BBC there were seemed to be two explosions, "We heard a 'boom' and saw the plane disappear into a cloud of dust and smoke," he told the broadcaster. "There was then a second explosion."

Some passengers on board the aircraft seemed unperturbed by the incident. Passenger David Eun tweeted a picture of people jumping out of the plane's emergency inflatable slides and wrote, "I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I'm ok. Surreal..."

Eun, who described himself as a "digital media guy" and "frequent flier", added, "Fire and rescue people all over the place. They're evacuating the injured. Haven't felt this way since 9/11."

However, several dozen people were injured but most were described as stable by health authorities. Rescue teams initially took 49 people deemed to be in a serious condition to nearby hospitals, officials said, but their condition was later described not to be life threatening.


Of the 291 passengers and 16 crew on board, 141 were Chinese, 77 were South Koreans and 61 were US citizens, according to the airline. CCTV News in China said there was also one Japanese national on board.

The two confirmed fatalities were Chinese citizens, according to South Korea's Transport Ministry. Both were young girls and were said to have been found on the runway. The high number of Chinese nationals on board, many of them students and their teachers, drew a stronger than usual interest from Chinese media. China's CCTV-13 Chinese language news station was providing almost saturation coverage throughout the day while other stations made the incident their top story.

Safety record

The twin-engine Boeing 777 has a relatively good safety record as a long-haul aircraft and is used by many major carriers. Nonetheless the aircraft has a short flight history, only coming into service in 1995. The plane involved in Saturday's incident [HL7742] was delivered  to Asiana, South Korea's second-largest airline, in March 2006.

As of 2013, the 777 had been in eight aviation occurrences, including three hull-loss accidents, and three hijackings. The type's first hull-loss occurred on January 17, 2008, when British Airways Flight 38, a 777-200ER with Rolls-Royce Trent 895 engines flying from Beijing to London, crash-landed approximately 300 metres short of Heathrow Airport's runway 27L and slid onto the runway's threshold. There were 47 injuries and no fatalities. The impact damaged the landing gear, wing roots, and engines, and the aircraft was written off. Upon investigation, the accident was blamed on ice crystals from the fuel system clogging the fuel-oil heat exchanger [FOHE]. In 2009, air accident investigators called for a redesign of this component on the Trent 800 series engine. Redesigned fuel oil heat exchangers were installed in British Airways' 777s by October 2009. It is not known if Asiana's fleet was also refitted however.

Two other minor momentary losses of thrust with Trent 895 engines occurred in February and November 2008. The National Transportation Safety Board [NTSB] investigators concluded that, just as on BA38, the loss of power was caused by ice in the fuel clogging the fuel-oil heat exchanger. As a result, the heat exchanger was redesigned.

The type's second hull-loss occurred on July 29, 2011, when an EgyptAir 777-200ER registered as SU-GBP suffered a cockpit fire while parked at the gate at Cairo International Airport. The plane was successfully evacuated with no injuries, and airport fire teams extinguished the fire. The aircraft sustained structural, heat, and smoke damage, and was written off. Investigators focused on a possible electrical fault with a supply hose in the cockpit crew oxygen system.

Saturday's crash was the third hull loss of a Boeing 777. The incident also marked the first fatal crash involving a Boeing 777 jet.

Focus of investigation

While the investigation will undoubtedly focus on engine failure, the fly-by-wire system may also be under some scrutiny. Deemed safe by most aviation experts, there are concerns that electronic failures could result in catastrophe. Aircraft systems may be quadruplexed, with four independent channels, to prevent loss of signals in the case of failure of one or even two channels. Nonetheless, something that could interfere with one system could, at least theoretically, interfere with them all [Wikipedia].

Electromagnetic interference could be of particular concern to electrical systems on a plane. Even though many systems are shielded, airlines strictly advise against the use of mobile phones and other electronic devices for fears they could affect a plane's sensitive electronic systems.

Should the use of cell-phones or other electronic devices prove to be a contributory cause, passengers may find themselves having to pack such items in their stowed luggage in the future. Even if the risk is small, many passengers ignore warning to refrain using their phones before the plane has taxied to the gate. It is not uncommon to see passengers switching on their phones even before the plane has landed and sending texts to waiting friends or relatives.

Flight boxes should at least explain any technical problems. There is however the cause and rapid spread of fire throughout the fuselage to be investigated. One potential cause, given the contained area where the fire damage existed, is the ignition of duty-free alcohol contained in overhead lockers.

Alcoholic beverages were considered to be a contributory cause to a fire which engulfed Korean Air Flight 801 after it crashed on approach to Antonio B. Won Pat International Airport, in the United States in August 1997.

It may well be that in the future, strong spirits might be banned from passengers' carry on baggage. An international agreement should perhaps be established before any such ban such that passengers be allowed to purchase duty free drink at their final destination. Even then such restrictions may prove unpopular as some airports may provide only limited choices.

Read more: BBC / Sky News / CNN / Telegraph

Update: A third schoolgirl died on the Friday following the crash bringing the death toll to three [Reuters]

tvnewswatch, Kunming, Yunnan, China

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