Aardvark Daily

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Programmers or pilots - who do you trust most?

9 October 2008

The Airbus line of passenger aircraft have been praised (mainly by their makers) as the most technologically sophisticated long-haul passenger jets in the world.

As well as their advanced physical construction, making use of the latest alloys and composites to reduce weight, increase strength and lift performance, the Airbus also embraces the concept of "fly by wire" (FBW).

The very first aircraft that flew relied on rather crude and primitive control systems. Sometimes this meant that (just as with a hang-glider), the pilot's body-weight was the only thing available to affect a change of course or pitch.

Indeed, the powered craft of NZ's own Richard Pearse had none of the moving surfaces we see on today's modern craft and experts believe it was pretty much "uncontrolled".

The Wright Brothers had a method called "wing warping" to provide them with control. A wire from each wing could be pulled to effectively twist the structure slightly to control whether it banked left or right.

Less than a decade later, most aircraft sported hinged, movable surfaces that were still controlled by cables linked to a control column in the cockpit.

These craft were slow and light so the pilot's own muscles provided all the force necessary to move those controls.

These were very simple systems which, providing they were inspected and maintained regularly, were very reliable.

However, as aviation continued to advance, planes became faster, bigger and heavier.

These changes meant that it became harder for pilots to exert the force necessary to move a plane's control surfaces against the slipstream that flowed over them while in flight.

Aerodynamic and mass-balancing were used to reduce the effort required but eventually other techniques such as power-tabs were also needed in order to provide the necessary mechanical advantage and leverage.

However, aircraft eventually got so big, heavy and fast that simple mechanical linkages could no longer be used. That's when power-assisted hydraulic systems were used.

Just like power-steering in your car, some of the engine's power was harnessed to assist with movement of the control surfaces.

A few decades later the microcomputer appeared and smart people in the aerospace industry started building things like autopilots which hooked those powered hydraulic systems up to gyros, compasses, GPS etc -- so the pilot could have little snooze from time to time.

Time marched on and aircraft-makers began to use computers to add safety features that would protect pilots and passengers from disaster.

This is where a divergence appeared in the industry.

There are now two paradigms in place within the passenger aircraft industry.

Boeing and most others use computers to help pilots make good decisions and provide warnings whenever the craft starts to drift dangerously towards the edge of its safe flight envelope (too fast, too slow, turning to tight, etc). In effect, the computer sits alongside the pilot and watches their every move -- helping where prudent and warning when necessary.

Airbus also use computers but their role is a lot more proactive - and this has been a concern to many in the industry.

In an Airbus, the computers don't sit alongside the pilot, they sit between the pilot and the aircraft's controls. When a pilot inputs a control movement, the computer looks at it, analyses what the result will be and *only* if it thinks it's a safe thing to do, passes that command on.

In Airbus system, the computer effectively has the right of veto over the pilot.

Almost every other passenger jet maker gives the pilot the final say and allows them to over-ride the computer's recommendations.

I know a lot of pilots and I also know a lot of computer programmers.

I'd rather fly in a Boeing any day -- in fact, despite the many, many hours of flawless flying that Airbusses have done, I would still be "less than comfortable" travelling in one.

And it looks as if the people on Qantas flight QF72 might now feel the same way.

Although it's not clear exactly why, this Airbus A330 appeared to suffer a computer "glitch" during a regularly scheduled flight - leaving pilots without control for a period of time.

Now I'm a hard-core techie who just loves and embraces computer technology - but I'm also a pragmatist.

I learn to live with the fact that almost everything that contains a computer will crash at some stage or another -- whether it's an iPhone, a Windows PC, an XBox or.... even an A380 Airbus.

Even though they are human and fallible, I would still rather place my trust in a pair of experienced and highly trained airline pilots than some team of spotty nerds who rarely see the light of day.

Even when you have triple redundant computer systems - you have to remember that it's simply three times as much stuff to go wrong and three times as many processors to crash.

So, do you prefer Boeing aircraft over Airbus ones?

Pilots or programmers? Who would you prefer to trust your life to?

Why has Qantas had so very many "incidents" recently? Coincidence? A curse? A cunning plan by Qantas maintenance staff to avoid redundancies and push for higher pay?

Do we place just a little too much faith in technology sometimes?

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