Boeing failed to communicate with 737 Max operators new procedures for addressing cases in which the airplane’s automatic stall prevention system commands the nose of the airplane downward, potentially resulting the kind of steep dive that appears to have led to the fatal crash of Lion Air Flight 610, according to pilot union officials quoted by the Wall Street Journal.
The November 7 AD required a revision to the chapters in the airplane flight manual dedicated to certificate limitations and operating procedures for addressing runaway stabilizer. According to the AD, analysis performed by Boeing showed the defect could lead to repeated nose-down trim commands of the horizontal stabilizer, thereby compromising aircraft controllability and leading to excessive nose-down attitude, “significant” altitude loss, and, ultimately, a crash.
“We are issuing this AD to address this potential resulting nose-down trim, which could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain”, said the AD.
Collected and summarized from the source below by Giang Tan https://www.ainonline.com/aviation-news/air-transport/2018-11-13/boeing-guidance-737-max-stall-protection-system-under-fire