An emergency directive has been issued, so more information is given to pilots. Airlines flying the aircraft types include Norwegian and Icelandair.
The US Federal Aviation Administration has put out an emergency airworthiness directive to airlines operating Boeing 737 MAX 8s and 9s.
The announcement follows analysis that Boeing has made since the crash shortly after take-off of Lion Air flight JT610 last week. The aircraft that crashed into the sea off Indonesia with 189 people on board was a two-month-old 737 MAX 8. There were no survivors.
The emergency directive, which the FAA says must be implemented within three days, states that there is a potential problem where incorrect “angle of attack” sensor input can cause the flight control system to send commands to the horizontal stabiliser to push the nose down.
This means that erroneous readings from one of the plane’s sensors can cause the plane to go into a sudden dive, the news agency Bloomberg reports.
A requirement of the directive is for operators of the two 737 models to revise the flight manual to give crews horizontal stabiliser trim procedures to follow under certain conditions.
The 737 MAX is the fastest-selling plane in Boeing’s history. By September, orders had been taken for 4,783 of them, with 219 already delivered to 40 airlines around the world.
These include Norwegian, Icelandair, Southwest, American Airlines, United, Air Canada and many others. The aircraft type has earned praise for its advanced aerodynamics and fuel-efficient engines.
But despite the Lion Air tragedy, Boeing and industry analysts remain confident in the company.
“This is a tragedy, but [the safety bulletin] says absolutely nothing about the design of the plane and its major subsystems,” TEAL Group aviation analyst Richard Aboulafia tells Business Insider.
Meanwhile, the search for bodies, debris and the cockpit voice recorder has been extended for three more days. It is the second time the search has been extended.
The search is involving 220 personnel, including 60 divers and four ships, focusing on an area with a radius of 250 metres.
The authorities have downloaded data from one of the black boxes found last week, the flight data recorder. A ‘ping’ for the cockpit voice recorder has been heard but is very weak, possibly because it is encased in mud, officials tell Reuters.