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Strategies & Market Trends : 2026 TeoTwawKi ... 2032 Darkest Interregnum
GLD 368.29+0.6%Nov 7 4:00 PM EST
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From: Elroy Jetson4/1/2019 5:22:11 PM
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elmatador

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With the benefit of more information I'd say pilots have become accustomed to being able to disengage all autopilot features by pushing the controls differently.

Like most commercial aircraft, the Airbus A300 has a TO/GA activator on the stick. If while landing the aircraft the pilot decides to abort, all they have to do is click the TO/GA button (Take-off/GoAround) and the throttles automatically increase to take-off power and the trim-control automatically moves to pitch the nose up.

Once the TO/GA button was activated, it had to be turned-off with a separate button. After hundreds of "out of trim" reports by A300 pilots, Airbus realized that pilots were inadvertently activating the TO/GA without realizing it, forcing the aircraft to gain speed and pitch-up.

So Airbus provided a software fix which allowed the pilot to disengage the TO/GA by pushing the stick forward to descend - which would automatically change the pitch-up trim and throttle the engines back to where they were. The same as pushing the button to turn-off the TO/GA.

Before this software fixed was applied China Airlines Flight 140 crashed. The very junior co-pilot inadvertently pushed the TO/GA controller while landing at Nagoya Airport. The pilot said, "You just pushed the TO/GA". The pilot seemed to assume the co-pilot would hit the deactivate TO/GA button because the pilot's only action was to take the controls and try to force the nose of the plane down to continue the landing. - en.wikipedia.org

After futilely trying to force the nose down for more than a minute the pilot decided to take-off and go-around manually - which in combination with the TO/GA system put the aircraft into a fast climb that was so steep the aircraft stalled and crashed straight down to the ground.

Anti-stall mechanisms on other Boeing jets can be deactivated by making one muscular pull on the stick. The force required lets the pilot know he has deactivated all autopilot functions. But the Boeing 737-max implemented an off-switch for the MCAS which could not be optionally switched-off with a powerful pull on the stick, just like Airbus did with the TO/GA on the A-300.

The software fix Boeing is providing still allows the MCAS to activate for a shorter burst, but only once if the pilot provides forceful different input with the stick.

It seems manufacturers are going to need to always accommodate the pilot's instinct to be able to turn-off automation by shoving the stick hard.
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