WE ARE MONITORING THE BOEING 737 MAX 8 ISSUES
It will likely be several months before the world finds out what exactly happened in the tragic crash of Ethiopian Flight 302 and the equally tragic crash of Lion Air Flight 610 back in late October, but everything appears to be pointing to a design defect in the Boeing 737 Max 8 model line, and a failure by Boeing to provide clear instructions in the aircraft’s flight manual about what to do if the relevant system malfunctions. Both aircraft crashed shortly after takeoff, and initial reports indicate that both suffered the same type of “nose over” command to the autopilot that is supposed to be a reaction to an imminent stall condition.
That description raises a number of concepts, and I will explain them one by one. First, any airplane can “stall,” but a stall of an aircraft is different from a stall of a car. A stall of a car means that the engine shuts down. A stall of an airplane means an “aerodynamic stall,” which essentially means that its wings stop producing the “lift” that is vital to sustained flight. Wings have curved surfaces on top, over which the oncoming air passes. When that air is guided around a curved surface, it speeds up. If you have ever watched a floating leaf meandering along a stream, you might have noticed that it goes faster around a rock in the stream than it does in flat water. That is because fluids go faster around turns. Air acts as a fluid also, so when a wing bends air, the air speeds up. Another law of physics is that this acceleration of the air flow results in a lowering of the air’s pressure. Low pressure creates a vacuum, which attaches to the wings and holds them up. (A vacuum cleaner is simply a machine that creates low pressure to help clean your home). In order for the wings to bend the air flow properly, they need to be at a certain angle relative to the oncoming air. That is known in aerodynamics as the “angle of attack.” If their front edges are presented to the oncoming air at too high an angle of attack, it is like holding your hand up flat to stop an oncoming blast of air-the air flow essentially bounces off and refuses to bend around the wings. That causes an aerodynamic stall, and the result is that the wings stop producing low pressure, the vacuum that was lifting the wings gets less powerful, and gravity takes over and causes the plane to drop. Clearly, that is not a desirable situation for an airliner full of passengers.
Airliners manufactured by Airbus, Boeing’s principal French competitor, have incorporated a system for many years that prevents aerodynamic stalls from happening. When the wings of an Airbus airliner are raised to a high angle of attack that would cause a stall, where the airliner’s nose would be pointed sharply up, the system takes over and orders the autopilot to pitch the nose downward, thereby returning the wings to an angle of attack that facilitates sustained flight. Pilot inputs are temporarily canceled, because the system assumes that something has happened to the pilot. No sane pilot would pull an airliner full of passengers into an aerodynamic stall.
The system that appears to have malfunctioned in the Max 8 is Boeing’s attempt to emulate the successful Airbus system. It is known as the MCAS. Its goal is to pitch the Max 8’s nose down, through commands to the autopilot, to prevent a stall. But Boeing’s system appears to sense that imminent stalls are occurring even when they aren’t. Pilots have complained of having to fight to keep the nose up, when the autopilot is trying to shove it down. In the cases of Ethiopian 302 and Lion Air 610, it seems the pilots lost the fight. In fact, recent reports indicate that the captain of Flight 302 started to experience problems almost immediately after takeoff, and requested permission to bring the plane back to the airport.
It is easy to say that the pilots should just turn off the autopilot and fly the airplane by hand, but modern airliners are not that simple. Many other necessary systems rely on the autopilot, so disengaging the autopilot creates a huge amount of work in the cockpit. It can certainly be done under some circumstances, but taking on an unexpected extra workload while negotiating a difficult departure route from a busy airport can sometimes be out of the question. The preferable course of action is to disengage only the system that is commanding the nose of the aircraft down erroneously. And that (in addition to the fact that the MACS system is malfunctioning in the first place) seems to be the problem. Pilots have called Boeing’s instructions for disengaging MCAS woefully deficient.
Those instructions are contained in the airplane’s certified flight manual, which is part of its required certification by the FAA. Flight manuals and their associated checklists are required to provide all of the instructions necessary to operate the aircraft safely. In order to do so, they need to be understandable. Max 8 pilots say they aren’t, as far as the MACS is concerned.
Boeing has known this for some time. Boeing keeps in touch with all of the owners of the 350 Max 8s that it has sold, and it receives reports from their owners on a regular basis. When they have a problem, they let Boeing know. When Boeing determines that a change in any system or set of instructions is necessary to ensure safe operation, it has the power to issue an immediate bulletin to all of those owners, worldwide.
So, why didn’t it? Media reports indicate that at least 5 pilots reported erroneous MCAS operation, but Boeing took no corrective action. When 189 people lost their lives in the Lion Air crash on October 29, 2019, Boeing began to stir into action (according to it). But no action resulted from such stirrings, and then 157 more people died in the Ethiopian Airlines crash. Why did 346 innocent passengers have to lose their lives before governments stepped in and grounded the Max 8s because Boeing wouldn’t? Did the fact that Boeing has approximately 5,000 orders for new Max 8s on its books play a role in its inaction? Investigation of its risk analysis documents will tell part of the story.
Park Avenue Law LLC continues to monitor this developing situation on a minute to minute basis.