Re: FLY-BY-WIRE (AIRBUS vs. BOEING)

From:         dreeves@ese.ogi.edu (B. Douglas Reeves)
Organization: Tanasborne Graduate Institute
Date:         21 Jun 95 02:56:50 
References:   1
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In article <airliners.1995.792@ohare.Chicago.COM>, Jean-Francois Mezei
<MEZEI_JF@Eisner.DECUS.Org> wrote:

 |Although the Airbus's FBW system makes actual flight decisions (eg: pilot
 |trying to make a movement that is outside aircraft's capabilities) which can
 |prevent stalling etc etc, I get the impression that Boeing's system is not as
 |sophisticated and is really a glorified auto-pilot with a couple more warning
 |buzzers. I get the impression that to Boeing, FBW means just that:
 |
 |make the interface between joystick and engine/rudders an electronic one.
 |
 |Am I right in assuming that the Boeing system has less "smarts" built into
 |it and that Boeing concentrated instead on providing mechanical feedback to
 |those joysticks to replace the mechanical interfaces that existed between the
 |pilot and co-pilot ?

1.  The 777 has a yoke rather than a joystick.

2.  There is tactile feedback from (a) the flight surfaces and (b) the other
   pilot on the 777, as opposed to Airbus, which has no tactile feedback.

3.  I do not know if "Boeing's system is not as sophisticated and is really a
   glorified auto-pilot" is really a correct statement.  Boeing chose to
   keep the pilots more "in the loop" than Airbus by providing feedback and
   having the ultimate fate of the airframe in the pilot's hands, not the
   computer's.  Studies have shown that it takes 3 to 6 seconds to make the
   transition from being a "system monitor" to a "system operator", ie,
   the autopilot is flying the aircraft and you take control.  I would
   think that a *lack* of tactile feedback would *increase* the length of
   time required to become the operator.  Also, the limits placed on the
   pilots in Airbus aircraft may keep the airframe undamaged ... until
   it hits the ground.  I would rather be able to bend the aircraft to
   keep it from breaking.

4.  "Boeing's system is not as sophisticated" is irrelevant.  Sophistication
   will not save your life or fly the plane.  A *good* system will.  Number
   of lines of code means nothing if the code contains bugs.  See my previous
   post on computer software and "1-in-a-million" bugs.  Interface design
   (eg. the infamous "dot" on the A320 for glideslope or vertical rate) and
   philosophy (pilot "in the loop") are the issues, not sophistication.
   Ask the pilots of the A340 who got the "Please Wait" message on
   approach if the sophistication was working in their favor then.....

As a side note, the A310 shares some of the A320/330/340's interfaces,
so it is worth considering the A310 in this discussion, just as the 777
shares much of the 757/767 interface, which has proven less problematic
than the A320.  Maybe we should change the subject to "Flight Deck Human
Interfaces" and include the 757/767 as well?


D. Reeves

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