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While Lion Air's crew was fighting to control their Boeing Co. 737 Max 8 dive, they were helped by an unexpected source: an out-of-service pilot who happened to be in the badpit.
This additional pilot, sitting in the gondola in the badpit, correctly diagnosed the problem and explained to the crew how to disable a faulty flight control system and save the plane, according to two people close to the Indonesian investigation .
The next day, under the command of another crew faced with what investigators have described as identical malfunction, the airliner crashed into the Java Sea, killing the 189 pbadengers on board .
Rescuers recover the wheels of the JT610 flight on November 4th. Photographer: Fauzy Chaniago / EPA-EFE
Undisclosed details on the previous Lion Air flight were a new clue as to how some 737 Max pilots faced with the malfunction were able to avoid a disaster while the others lost control of their planes and crashed. The presence of a third pilot in the badpit was not included in the November 28th report of the National Transportation Safety Committee of Indonesia on the accident and had not been reported before.
The so-called dead chief pilot during the Bali-Jakarta flight asked the crew to shut off engine power in the trim system that was lowering the nose, according to people familiar, part of the list control requiring all drivers to memorize.
On the other hand, the crew of the flight that crashed the next day did not know how to react to this malfunction, said one of the persons familiar with the badpit voice recorder of the aircraft found in the of the investigation. They can be heard checking their quick reference manual, a summary of how to deal with unusual or urgent situations, minutes before their fall, Reuters reported, citing people he did not name.
Lion Air spokesman, Danang Prihantoro, declined to comment on the role of a third pilot, stating, "All the data and information we have available on the flight and the aircraft have been submitted to the NTSC Indonesian. We can not comment further at this point due to the ongoing investigation into the accident. "
The report of the Indonesian safety committee indicated that the aircraft had several breakdowns during previous flights and had not been repaired properly.
The airline mechanics have tried four times to solve the problems related to the plane from October 26, according to the preliminary report of Indonesia. After pilots reported problems with incorrect display of speed and altitude during the previous two flights, workers from Denspasar, Bali, had replaced a key sensor used by the aircraft. of Boeing to make him lose his nose if he detected an urgency.
Flight data shows that the sensor, known as the "angle pallet", which measures whether air flows parallel to the fuselage length or at an angle, then provides inaccurate readings.
However, according to the report, flights between Bali and Jakarta on 28 October did not report any major problems.
Their maintenance request did not mention that they had received a stall warning about 400 feet after take-off because of the defective angle of attack sensor. According to the flight data, the crashed flight was still wrong the next morning.
Boeing and Indonesian security committee representatives declined to comment on the previous flight. Boeing rose 1.1% to $ 377.59 at 12:03 pm in New York. The company's market value dropped by about $ 28 billion until Tuesday after the crash of Ethiopian Airlines.
The badpit of a 737 Max 8. Photographer: Dimas Ardian / Bloomberg
The security system, designed to prevent planes from climbing too high and stalling, was closely examined by accident investigators, as well as by another less than five months later in Ethiopia. It is believed that a faulty sensor has led the aircraft computers at Lion Air to believe that it was necessary to automatically lower the nose to prevent a stall.
The Boeing 737 Max was grounded on March 13 by US regulators, after similarities to the Oct. 29 accident, Lion Air, during the accident investigation. from flight 302 of Ethiopian Airlines. new 737 models have been approved.
The Inspector General of the Department of Transportation is currently reviewing the aircraft's certification process and a US Justice Department grand jury is also investigating elements of a possible criminal investigation into the certification of the aircraft.
Last week, the FAA announced its intention to make system changes mandatory in order to make it less likely to activate in an emergency. The agency and Boeing indicated that they would also require additional training and referrals to this training in flight manuals.
Boeing Reprograms 737 Accident System
A software update will prevent a single sensor from activating the system to increase maneuvering characteristics. The data of the two sensors will be taken into account.
"We will fully cooperate with this review during the Ministry of Transport audit," Boeing spokesman Charles Bickers said in an e-mail. The company declined to comment on the criminal investigation.
After the Lion Air crash, two US pilot unions said that the potential risks of the system, known as the maneuver feature augmentation system, were not sufficiently explained in their manuals or training. None of the documents concerning the aircraft Max included explanation, said the union leaders.
Boeing 737 Max 8 jets at Phoenix Sky Harbor International Airport on March 13th. Photographer: Ralph Freso / Getty Images
"We do not like that we are not warned," said Jon Weaks, president of the Southwest Airlines Pilots Association, in November. "It makes us wonder," That's all, guys? "I hope that there will be no more surprises."
The Allied Pilots Association of the American Airlines Inc. group also stated that details of the system were not included in the aircraft documentation.
As a result of the Lion Air accident, the FAA asked Boeing to inform the airlines of the system and Boeing sent a newsletter to all customers using the Max to remind them how to disable it in emergency case.
The authorities published little details about Ethiopian Airlines flight 302, apart from flying "very similar" to Lion Air flights and then plunking into the ground. No maintenance problem on the Ethiopian Airlines plane was reported before its crash.
The wreckage was found on March 11 at the crash site of ET302 flight of Ethiopian Airlines. Photographer: Jemal Countess / Getty Images
If the same problem also contributed to the destruction of Ethiopian Airlines flight 302, one of the most difficult problems for accident investigators and aviation safety consultants is why the pilots of this flight do not proceeded to the checklist disabling the system.
"After this horrific Lion Air accident, you would think everyone aboard this plane will know how to solve this problem," said Steve Wallace, former director of the accident investigation division of the US Federal Aviation Administration. United.
The combination of the factors needed to bring down an aircraft in these circumstances suggests that other problems may also have occurred during the crash in Ethiopia, said Jeffrey Guzzetti, who also led the FAA's accident investigations. and who is now a consultant.
"It is simply implausible that this MCAS deficiency alone can defeat a modern airliner with a qualified crew," Guzzetti said.
The MCAS is piloted by a unique attack angle sensor located near the nose, even if there are two sensors in the aircraft. Boeing plans to modify the system to rely on both sensors to reduce the risk of malfunction.
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