A new and detailed theory suggests that a potential bird strike plus pilot error, coupled with faulty sensors, resulted in the ET302 crash.
I’ve been following the ET302 crash closely as we all try to better understand what happened and how to prevent it in the future. Pointing fingers will not bring back lives. After Boeing CEO’s confession last week, it won’t stop the lawsuits either. But wouldn’t you feel better stepping onto a 737 MAX if pilot error or bird strikes played a big role in both crashes?
Reuters published a fascinating piece entitled, “How flawed software, high speed, other factors doomed an Ethiopian Airlines 737 MAX.” We all know the working theory. The plane took off, the pilots retracted the flaps and slats, and a sensor began feeding incorrect information to the Boeing’s Maneuvering Characteristics Augmentation System (MCAS). The crew lost control of the aircraft and it shortly crashed.
But there may be more to the story. Experts who have reviewed the black box recordings and studied the trajectory of the aircraft have offered a different theory.
The engines remained at full take-off power as the airline’s youngest-ever but highly-experienced captain, a 29-year-old with 8,122 hours of flying time, and his 25-year-old co-pilot, with 361 hours, flew the aircraft out of its initial climb.
That would be an unusual step in a regular flight, according to the experts and five current and former pilots interviewed by Reuters, most of whom were not authorized to speak publicly. “You would never, ever have full power for the whole flight,” said Hart Langer, a veteran former senior vice president for flight operations at United Airlines.
The reason the engines continued at full take-off power was not given in the report. But it is not part of a usual procedure for pilots dealing with the loss of key information such as the sensor data, the four experts said.
Set aside the age for a moment, because I know some 20-somethings who are far more mature than people twice their age. Was ET302 continuing at full take-off power because they were fighting MCAS the entire time?
By the end, the aircraft was traveling at 500 knots (575 mph, 926 kph), far beyond the Boeing jet’s operating limits.
This contradicts Ethiopian Airlines’ statement last week, which claimed: “no excess speed was noted at the initial phases of the flight.”
Downward trim (triggered by MCAS) plus the increased speed (potential pilot error) may have been the lethal combination, not the MCAS alone.
And why did this happen? Did the plane simply malfunction?
A sudden spike in black box data was consistent with a bird or other debris hitting the plane as it was taking off, shearing away a vital airflow sensor, said the four experts and two U.S. officials briefed on the data.
What if debris or birds took out one of the sensors, leading to the chain of events that caused the crash?
With a potential bird strike triggering faulty sensor data, the MCAS system forced the nose of the aircraft downward. The black box recording has the captain yelling at his co-pilot to “pull up” but the force required was so strong he could not muster the strength to pull back on the yoke. The captain also instructed his co-pilot to trim the plane using the manual backup wheel in the center console. But that too they could not move.
Desperate, the pilots re-activated the electric trim system, which reactivated MCAS. That went specifically against Boeing instructions and was also left out of the Ethiopian Airlines report. In other words, the crew knew the MCAS was faulty, turned it off, but turned it on again out of desperation, which only hastened the crash.
This is but a theory, but a well-developed and highly-plausible one. There are even details in the story I linked to above. As the investigation unfolds, we may soon establish that it wasn’t just a lemon of an aircraft, but a bird strike and two critical cockpit errors.
> Read More: Boeing CEO Accepts Blame For 737 MAX Crashes