Ethiopian airline pilots switched off MCAS black box revealed

The cockpit voice recorder captures conversations inside an aircraft’s cockpit, while the cockpit data recorder logs the aircraft’s actions, pilot instructions, and the plane's responses. Together, these tools provide crucial insights into what happens during the final moments of a flight. The preliminary investigation into the Ethiopian Airlines Flight 302 crash is based on data recovered from these devices at the crash site near Addis Ababa, Ethiopia.

Leaked information from the preliminary report reveals that the pilots of Flight 302 successfully switched off the Maneuvering Characteristics Augmentation System (MCAS), following Boeing's prescribed checklist. This undermines claims that the pilots were inadequately trained or that their African location contributed to the disaster. Boeing has consistently maintained that switching off the MCAS should resolve such issues, allowing pilots to manually control the aircraft and safely navigate out of danger. However, despite disabling the MCAS, the plane still crashed, killing everyone on board.

Even more concerning, the report indicates that after the MCAS was disabled, the plane continued to experience problems, including a persistent nose-down motion. At some point, the MCAS reactivated, but it remains unclear whether this was done manually by the pilots or automatically by the system. Most aviation experts believe the system restarted automatically, which aligns with the notion that pilots, facing persistent nose-down issues, would have no reason to re-enable the MCAS.

Similarities between this crash and the earlier Lion Air crash in Indonesia raise further questions about the reliability of the MCAS system. In the Lion Air incident, a faulty angle of attack sensor falsely signaled that the aircraft was at risk of stalling, causing the MCAS to repeatedly push the nose down. Boeing proposed a fix requiring the use of two sensors to prevent such errors, with a cockpit warning light to indicate any sensor disagreement.

However, the Ethiopian Airlines crash suggests that faulty sensors were not the sole issue. When the MCAS is disabled, the sensors are no longer in use, meaning the problem lies deeper within the aircraft's design or software. This new evidence challenges the conclusions drawn from the Lion Air investigation and calls into question Boeing’s guidance to pilots after that crash.

Boeing had informed airlines and pilots that disabling the MCAS should resolve any problems. Ethiopian Airlines pilots, armed with this knowledge, followed the procedure but still could not prevent the crash. This situation is akin to traveling back in time to warn Lion Air pilots of the MCAS issue, only to have the plane crash again despite following instructions.

The evidence increasingly points to a critical flaw in the 737 MAX 8 design. The MCAS was introduced late in the development process to address the plane’s tendency to pitch nose-up due to its modified engine placement. The system was intended to automatically correct this issue by forcing the nose down. However, when the MCAS is disabled, the plane becomes vulnerable to uncontrollable nose-up motions, particularly at high speeds.

In the case of Flight 302, the plane was traveling at an unusually high speed shortly after takeoff, making recovery nearly impossible when problems arose. At low altitudes, such as during takeoff, there is limited time to regain control, unlike at cruising altitude, where pilots would have more room to maneuver. This high-speed, low-altitude scenario rendered the plane virtually uncontrollable.

Ultimately, the evidence suggests that the 737 MAX 8 design and reliance on the MCAS system make the aircraft inherently unsafe. The high speeds, vulnerability to nose-up situations, and dependence on software intervention create a combination of risks that even experienced pilots cannot fully mitigate.

In conclusion, the 737 MAX 8 was not safe to fly, and the crashes in Ethiopia and Indonesia highlight fundamental flaws that Boeing must address to ensure the safety of future flights.