Potentially erroneous or misleading cockpit airspeed readings have emerged as a first focus of security experts on the Lion Air plane crash in Indonesia, which killed 189 passengers and crew members.
The company that made the 737 Max 8 twin-engine model and participates in the probe has privately suggested at least one airline officer and one external security expert to be interested in whether the pilots received unreliable speed data, the interlocutors said.
The plane, which was delivered to the airline in August, crashed into the Java Sea 12 minutes after departure from Jakarta in good weather, without the crew sending a Mayday message. Indonesian teams mapped the ocean floor on Tuesday while searching for the jetliner.
The Chicago-based aircraft manufacturer has signaled, according to an independent security expert closely associated with the company, that its experts are particularly keen to understand the maintenance work reported to have been carried out on some of the aircraft's airspeed measurement and reporting systems deadly flight.
At least one aviation officer said he had understood that a problem with the airspeed monitoring was discussed the day before the crash due to maintenance, one person who was informed about the discussion.
The spokesman declined comment and referred to the company's earlier allegation that it provided technical assistance to the investigation and asked questions to the Indonesian authorities.
The discussions of possible speed deviations are preliminary and may change significantly if data downloaded from flight data and cockpit voice recorders indicate other potential system malfunctions or missteps by the pilot. Pilots are routinely trained to cope with unreliable airspeed information, and security experts said such reactions – especially in clear weather with a visible horizon – should not normally cause the crew to lose control.
However, security experts believe that dealing with irregular speed displays may be difficult for some airlines, as they are usually reliant on manual flying, at least temporarily. Capabilities rarely used in today's increasingly automated cockpits.
The government investigators in Indonesia and the US have not commented on the details of the probe, and air traffic control officials said the flight crew did not specify when they requested permission to return to the airport.
Airspeed reporting and maintenance issues will be part of the investigation, said Soerjanto Tjahjono, head of the National Road Safety Committee of Indonesia, who is conducting the investigation, to the Wall Street Journal without comment. He confirmed that the investigators will investigate the circumstances of the specific maintenance checks performed prior to the crash.
Search at sea
New Boeing 737 model was missing shortly after launch from Jakarta to Pangkal Pinang.
Boeing said in a message to the operators who run the latest 737 Max 8 models that they would endeavor to keep them up to date, he noted that "there are currently no recommended actions by the operator," one said copy checked by the journal.
This language usually indicates that a manufacturer has not detected any system-related defects or design flaws that require immediate safety checks or repairs.
A search of the US Aviation Authority's records did not reveal any unusual patterns of problems or failures affecting airspeed indicators or other mechanical or electrical systems of the 737 Max 8 fleet, according to a person familiar with the matter.
A number of other 737 Max 8 operators said they did not know about recurrent aircraft errors.
Based on public information about Lion Air Flight 610 – combined with various types of communications between Boeing, some of its airline customers, and external security experts – the investigation has increasingly fueled industry interest in displaying airspeed on cockpit instruments. For Boeing 737 Max 8 aircraft, captain and co-pilot have separate airspeed indicators and there is an additional standby system.
Relatives complain as Indonesia reacts to jetliner crash
Underwater tracking devices that are sent to the crash site will attempt to find flight data and cockpit voice recorders of the aircraft
Members of the search and rescue team in Jakarta look through recovered items that are believed to come from the downed Lion Air JT610 flight on Tuesday.
Edgar Su / Reuters
1 out of 10
The Ministry of Transport has transported the two Indonesian airlines with the Boeing 737 Max 8, Lion Air and the airline
to learn about repetitive airspeed problems and to explain all procedures for their elimination. The aircraft are not grounded and would remain in service, said Pramintohadi, the acting Director General of Air Transport, told reporters.
Problems with faulty pitot tubes – aircraft airspeed airspeed sensors – have been well documented over the years, leading to a series of passenger plane accidents. They often occur in stormy weather at cruising altitudes – much higher than the Lion Air aircraft that did not climb over 5,000 feet – as ice crystals accumulate and sensors clog.
Over the past decade, US and European regulators have issued a series of mandatory safety instructions to check or replace Pitot tubes that are prone to failure
Jetliner and other models.
However, the same sensors can be affected by debris or other conditions on the ground. Pilots have detected cases of wasp nests in pitot tubes, and workers have accidentally left covers after painting or waiting.
"With this system, some things can go wrong, even if it's pretty straightforward," said a pilot from a major US airline.
– Ben Otto contributed to this article.
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