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737 MAX - Update.

From NY Times, via the Oz:

Boeing 737 pilots had 40 seconds to avert plane crash
MARCH 28, 2019

[img=188x0]https://cdn.newsapi.com.au/image/v1/a3ccd731f9992d355bf2664fe58e86d3?width=320[/img]
All pilots of Boeing 737 MAX planes will need extra training before they can fly it again, as part of a remedy package.

By ROBYN IRONSIDE

Unwary pilots flying a Boeing 737 Max would have had only 40 seconds to stop a rogue control system sending the plane crashing to the ground, tests on a simulator have suggested.

The tests have given a clearer picture of the last moments of Lion Air flight 610 in October last year, and probably also of Ethiopian Airlines flight 302, which crashed on March 10 near Addis Ababa, with a total of 346 people killed. The second of the two crashes prompted the grounding of all 737 Max jets and plunged Boeing into crisis.

The company has invited 200 pilots, airline managers and regulators to Renton, Washington, today where it will unveil software changes that it says fix shortcomings evident when used by less experienced pilots. Crews will have more control over the 737 Max stabiliser system, which Boeing insists is not flawed. Federal prosecutors and congressional investigators are scrutinising the way the system was developed.

On Saturday pilots from five airlines, including American, United and Southwest, visited Renton, where the 737 is built, to test how the aircraft would have responded to the Indonesian situation and to evaluate how it performs with the updated version of the software.

They confirmed that the pilots would have been overwhelmed by the Manoeuvring Characteristics Augmentation System, or MCAS, when it kicked in as a result of faulty data from an airflow sensor, The New York Times reported.

The Indonesian pilots were unaware of the existence of MCAS, designed to prevent stalls, because Boeing had not told its customers about it. Tewolde GebreMariam, chief executive of Ethiopian Airlines, has confirmed that the MCAS was operating on the company’s plane when it crashed. After that crash all Boeing pilots were briefed on the system. The US pilots who simulated the MCAS malfunction were surprised by the force with which the electrically powered stabiliser trim system overruled the crew and relentlessly pushed the aircraft’s nose down, The New York Times said.

The system is designed to pitch down when it detects an imminent stall. It operates only when pilots are flying manually with wing flaps retracted, just after take-off.

With no pilot action a rogue MCAS will send the aircraft out of control within 40 seconds, the tests found. Pilots can win a few minutes by counteracting the system with trim switches. The Indonesian pilots did that, the recorders showed, but the system wins by ratcheting the nose down further.

The remedy, which is standard for all stabiliser problems, is to flick two switches that cut power to the stabiliser. The Indonesian crew did not get as far as that as they leafed through a paper manual to troubleshoot their problem. Even with the stabiliser cut, pilots must briskly crank cockpit trim wheels to save the aircraft.

John Cox, a safety consultant and a former 737 pilot, said pilots had little time to understand the emergency. ‘‘There is a limited window to solve this problem, and this crew didn’t even know that this system existed,” he said.

Boeing said that its revised software “incorporates additional limits and safeguards to the system and reduces crew workload’‘. The fix will stop repeated operation of the MCAS and deactivate it if two sensors which measure the angle of oncoming air disagree. A new warning light is to be installed in cockpits to warn of angle-of-attack problems.

The software will take only an hour to install but Boeing, which has 5,000 737 Max aircraft worth $500bn on order, must convince US, European, Canadian and Chinese regulators that the aircraft is airworthy. Airlines have begun cancelling orders for what is Boeing’s best-selling aircraft.

The Times

 

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