More on the difference between Airbus and Boeing control systems

An MR reader writes to me:

Chances are you have received an email similar to this from other airline pilots, but in the off case you have not:

The article you posted contains what I believe to be some oversimplifications of the A/B control system philosophy differences.

It’s commonly stated that the Airbus will override the pilot and the Boeing will not.  This isn’t entirely true.

A more accurate statement would be this:  All jet aircraft have override/feedback systems that will warn or resist the pilot at the edges of the aerodynamic envelope.  Airbus has a slightly larger number of these systems, and they are set to trigger slightly earlier.

Both aircraft will automatically throttle back if in an overspeed condition.
Both aircraft will automatically shake the yoke, and then automatically push over, in a stall condition.


Airbus, in addition, will limit max G forces on the aircraft.  Boeing does not.

The advantage of the Airbus approach is that you can haul back on the stick as hard as you want without breaking the aircraft (and turning it into several smaller, less-airworthy aircraft).  You are limited to G forces that produce no damage to the aircraft.

The advantage of the Boeing approach is that you can generate any g forces you want.  This gives you the opportunity to fly in the region that generates enough G to bend the aircraft, but not to break it.  That extra G force may help you avoid a mountain.  Of course, you may extend into the part of the envelope that breaks the aircraft.

These differences are relatively minor, as the vast majority of crashes do not occur at the edges of the envelope, and are categorized as CFIT (Controlled Flight Into Terrain).  When within the aerodynamic envelope, Boeing and Airbus aircraft are usually under the control of the same sort interchangeable flight management computers.

Both the Asiana (Boeing) and Air France (Airbus) crashes were caused by crew that did not understand the systems of the aircraft they were flying.  Both aircraft impacted terrain under full control.


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