Pilots who fly Boeing's 737 MAX in the US say the airline manufacturer didn't tell them about features of a new flight-control system that reportedly are part of the investigation into last month's deadly crash in Indonesia. In the event that a pilot raises the nose too high, the system is created to force the nose downwards in order to prevent a stall.
A union bulletin to pilots at American Airlines Group Inc. said the company hadn't provided details about the system with its documentation about the plane.
Boeing Co and United States aviation regulators are weighing whether to issue a software fix to the 737 Max, the aircraft type involved in a recent crash in Indonesia to ensure that the plane won't dive aggressively without pilot commands.
What the air crash investigators will be considering now is whether the pilots would have had time to implement this checklist when experiencing an unexpected nosedive at just 5,000 feet. He said the procedures for handling the control issue were "part of the training manual". It wasn't in our books.
The Allied Pilots Association, which represents American Airlines pilots, suggested something similar in a message to its members.
Pilots trained on the MAX weren't given even minimal briefings on MCAS, according to an interview with Jon Weaks, president of the Southwest Airlines Pilots Association published in the Seattle Times early Tuesday.
"I was not pleased. We want to be given the information to keep our pilots, our passengers and our families safe", he said.
"The crew may have been hampered in their efforts to understand the airplane's behavior, and regain control, by the fact that they were missing a key piece of information - the existence of an automatic system that could adjust the trim, even when the airplane's autopilot was switched off", Douglas Harned, an analyst at Bernstein Research, said in a note to clients.
The comments focus attention on the contents of aircraft manuals and a conversion course allowing pilots of the previous generation of Boeing jet, the 737NG, to upgrade to the MAX. An American spokesman said the airline was unaware of some new automated functions in the MAX but hasn't experienced nose-direction errors.
The Federal Aviation Administration issued an emergency directive last week to airlines, telling them to update cockpit manuals to include instructions for how pilots can adjust flight controls under certain conditions.
When Boeing designed its latest version of the 737, it added the new safety feature to combat a loss of lift, which is a leading contributor to the loss-of-control accidents that by far cause the most crash deaths around the world.
The Oct. 29 crash was the first accident involving the 737 MAX, an updated version of Boeing's workhorse narrowbody jet that entered service a year ago.
The Wall Street Journal reported that US and Indonesian investigators are increasingly focusing on the way that the plane's automated control systems interact.