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Should We Let Computers Control Aircraft? March 23, 2019

Posted by Peter Varhol in Algorithms, Software platforms.

Up until the early 1990s, pilots controlled airliners directly, using hydraulic systems.  A hydraulic system contains a heavy fluid (hydraulic oil) in tubes whose pressure is used to physically push control surfaces in the desired direction.  In other words, the pilots directly manipulated the aircraft control surfaces.

There is some comfort in direct control, in that we are certain that our commands translate directly to control surface motion.  There have only been a few instances where aircraft have complete lost hydraulics.  The best-known one is United Flight 232, in 1989, where an exploding engine on the DC-10 punctured lines in all three hydraulic systems.  The airliner crash landed in Sioux City, Iowa, with the loss of about a third of the passengers and crew, yet was considered to be a successful operation.

A second was a DHL A300 cargo plane hit by a missile after takeoff from Baghdad Airport in 2003.  It managed to return to the airport without loss of life (there was only a crew of three on board), although it ended up off the runway.

In 1984, Airbus launched the A320, the first fly-by-wire airliner.  This craft used wires between the flight controls used by the pilot and the control surfaces, with computers sitting in the middle.  The computers accept a control request from the pilot, interpret it in light of all other flight data available, and decide if and how to carry out the request (note the term “request”).  There were a few incidents with early A320s, but it was generally successful.

Today, all airliners are fly-by-wire.  Cockpit controls request changes in control surfaces, and the computer decides if it is safe to carry them out.  The computers also make continuous adjustments to the control surfaces, enabling smooth flight without pilot intervention.  In practice, pilots (captain or first officer) only fly manually for perhaps a few minutes of every flight.  Even when they fly manually, they are using the fly-by-wire system, albeit with less computer intervention.  Oh, and if the computer determines that a request cannot be executed safely, it won’t.

Fly-by-wire is inarguably safer than direct-fly hydraulic systems in controlling an aircraft.  Pilots make mistakes, and a few of those mistakes can have serious consequences.  But fewer mistakes can be made if the computer is in charge.  Another but:  Anyone who says that no mistakes can be made by the computer is on drugs.

Fly-by-wire systems are controlled by complex software, and software has an inherent problem – it isn’t and can’t be perfect.  And while aircraft software is developed under strict safety protocols, that doesn’t prevent bugs.  In the 737 MAX MCAS software, Boeing seems to have forgotten that, and made the system difficult to override.  And it didn’t document the changes to pilot manuals.  And that, apparently, is why we are here.  I am not even clear that the MCAS software is buggy; instead, it seems like it performed as designed, but the design was crappy.

The real solution is that yes, the computer has to fly the airplane under most circumstances.  The aircrew in that case are flight managers, not pilots in the traditional sense.  But if there is an unusual situation (bad storm, computer or sensor failure, structural failure, or more), the pilots must be trained to take over and fly the plane safely.  That is where both airliner manufacturers and airlines are falling down right now.

Aircrews are forgetting, or not learning, how to fly planes.  And not learning situational awareness, when they are able to comprehend when something is going wrong, and need to intervene.  It’s not their fault; aircraft and flying has changed enormously in the last two decades, and there is a generation of younger pilots who may not be able to recognize a deteriorating situation, or what to do about it.



1. Five Blogs – 24 April 2019 – 5blogs - April 24, 2019

[…] Should We Let Computers Control Aircraft? Written by: Peter Varhol […]

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