Subject: Re: Airbus safety (was Re: TWAs Status)

From: [email-masked] (Robert Dorsett)
Date: 10 Dec 92 16:07:03 PST

In article <[email-masked]> [email-masked] (Philip Peake) writes:
>
>It wasn't unintentional - it was a deliberately (contrived) example.
>The arguments I have heard so far seem to say that just because its always
>been done that way, it always should be - aircraft design has changed a LOT
>since the stick control was introduced - maybe this is no longer the
>correct control mechanisim ?

Transport aircraft design hasn't changed much at all in the last 30 years.  
We fine-tune various features, change the aspect ratio, develop better drag 
profiles, better powerplants, occasionally build a better, lighter system.  
Certainly improved manufacturing techniques.  But the *engineering* discipline 
is so WELL defined that if you give three manufacturers the task of developing 
three different airplanes for the same mission profile, you'll now come up 
with almost identical airplanes.   It is a discipline so evolved that we can 
come up with physical implementations which can match design performance 
objectives to within a percentage point.  

This is not the result of "wild-catting," or breaking the rules: it's the 
result of decades of working over the same problem, developing a very 
intimate understanding of this particular type of development problem.  We
should expect that the same considerations must be applied to how the 
pilots control the airplane.  The "old" model may not be the best available,
but it's well-understood, and is likely preferable to any "replacement"
we are likely to produce with current technology.

>If you are against the idea of insulating the pilot, maybe we should
>remove servo brakes and power steering from cars too ?

The pilot IS in the loop.  You can complain about that, and try to eliminate
that, if you want to.  However, since he IS in the loop, the unique feedback
requirements needed to let him do his job require a more interactive environ-
ment than either contemporary glass cockpits *or*, in this case, the A320
sidestick, provide.

Christopher Davis already addressed your point in his reply: *hydraulics*
is the equivalent of power steering, not FBW control.  However, note that 
we've been providing completely artificial feel to go along with this, for 
the past thirty years.  Yet all of a sudden, on the pretext that the "FBW"
in their airplane mandates it, Airbus, which is in the business of selling 
technology, cavalierly introduces a control device which:

	1.  Has no interconnect between the pilots.
	2.  Has no active feedback.
	3.  Utilizes artificial control laws in the normal and alternate 
            flight modes.

I suggest that the issue has NOTHING to do with technological "advantages"
human requirements: it is completely marketing-driven.  

>|> In essence, my point is that standards don't exist because of happenstance.
>|> They exist because it makes life easier for everyone.  This is particularly
>|> important when human lives are at stake.
>
>Standards are also perpetuated by vested interests,

Yeah, that powerful yoke-manufacturer lobby.  The bastards.  Just because
they won't retool to build sidesticks, they gotta ruin it for the rest of
us. :-)

Seriously, this is a tremendously conservative industry.  What isn't broken,
doesn't get fixed.  However, when a better mouse-trap is invented, it is
almost always adopted, universally.  The fact that no other manufacturer
is rushing to repeat Airbus' example suggests the arbitrariness of the
use of the sidesticks: if there were even minor operational or material
advantages in using them (and modified control laws) as interfaces to the
EFCS, you could bet your last dollar every other manufacturer would be doing 
so, not least as the result of airline demand.   We don't see that.

> even when better ideas
>ar around. 

This isn't one of them.  We aren't operating in a vacuum: NASA, as one example,
has been running a lot of research (over, and over) over the last 20 years, 
addressing precisely these issues: the Airbus implementation is arguably on
the weaker of a variety of choices available.

>If all new pilots were taught nothing but the side stick,
>how long would the old arangementy last - and if the old arangement

Why should pilots be taught nothing but a unique, *proprietary* side-stick 
design that no pilot had any experience with before four years ago, and which 
is only one of a variety of other possible designs?  

You imply that the sidestick's just a yoke wrapped up in a little handle.  It 
isn't: the issue's a lot more complex, and, within that simple interface, 
there are *many* ways to proceed.  The certification authorities, you will 
note, have not codified mandatory control qualities of this interface (and 
WON'T): thus, in a worst-case, we could have Airbus running its stick (+ 
control laws), Boeing running its own, MDC running its own, etc.

>is so wonderful, why do military fighter aircraft, where tight control
>by the pilot os ESSENTIAL use side stick controls ?

Not all do: several continue to use center-sticks.  In either case, the
issue is in large degree driven by the need to effectively control
the aircraft at high g's--but even then, it's a significantly different 
design than that used in the A320.

I would also note that in fighter aircraft, there isn't the issue of 
two-pilot "peers" having to quickly and instinctively figure out who is
flying the airplane.  On the A320, there is no interconnect between the
sidesticks: the captain can command a full-left in an emergency evasive
maneuver, the F/O full-right, and the net result will be an algebraically
added "zero."  

>The problem is the PILOTS, not the design

Here we flip to cockpit integration, not sidesticks.

The problem is a design philosophy which is unwilling to accomodate the human
element.  I also see a great deal of "stick it to the pilots" going on: a 
number of proponents of pilot-isolation don't even bother to cite alleged 
economic or safety benefits, anymore: the pilot-isolation increasingly appears
to be an engineering-driven goal in itself. 

The Airbus approach has gone too far.  Thankfully, however, it seems to be
on its way out: new designs, such as the 777, are more sophisticated,
yet have more conventional and interactive interfaces.  And the research 
community is coming squarely on the side of more interactive, appropriate 
feedback.  New designs will be more human-factors-driven, not engineering-
driven.  And, with luck, we'll see a return to the *evolutionary* application 
of high technology, rather than the *revolutionary* application of the same.

And who knows, in 20 years, when we have enough underlying experience and
research under our belts, we can try a *standardized* alternate interface.

BTW, and for the record, I *like* the idea of sidesticks: for no other reason
than to be able to see the entire instrument panel, unencumbered.  I simply
don't like this particular implementation, and have concerns about the 
human requirements any sidestick design could introduce.

>Philip

---
Robert Dorsett
[email-masked]
...cs.utexas.edu!cactus.org!rdd

---

From: [email-masked] (Michael T. Palmer)
Date: 11 Dec 92 17:42:30 PST

>the weaker of a variety of choices available.

My contacts at Boeing agree - Boeing Flight Deck Research has been looking
at sidestick controllers for a long time.  They have decided that until they
develop an airplane that is flown *differently* they will continue to use
the column/yoke arrangement.  Now, what I mean by differently really refers
to switching from ATTITUDE control laws to VELOCITY VECTOR control laws.
Mr Dorsett is correct; NASA Langley has decades of experience with sidestick
controllers in our B-737 aircraft (it has TWO cockpits - standard in front,
and an aft research cab from which you can fly the entire flight profile
including landing).

The sidestick control has been shown to be best when commanding velocity
vector changes instead of attitude changes.  This is an interesting way of
using automation to ease the burden on the pilot while allowing him to
also remain in the loop, since the automation configures the control
surfaces to maintain the commanded direction of flight, but the pilot
still "flies" the airplane (when not in full-autopilot).  The velocity
vector control-stick steering mode is by far the mode of choice of the
pilots we bring in for experiments.

Based on the work here and their own efforts, Boeing has decided that until
they build a velocity vector airplane (hint: High-Speed Civil Transport)
they will not provide a totally different way to fly an airplane designed
with attitude control laws in mind.

Please note that I am neither a Boeing employee nor spokesman, and I neither
(officially) recommend nor approve of actions taken by them.  All the info
provided here (about Boeing's position) was provided to me personally by
Boeing employees, though, so I have no reason to doubt it.  It would be nice
if some of you lurking Boeing people jumped in to correct any mistakes I
have made.  :-)

-- 
Michael T. Palmer, M/S 152, NASA Langley Research Center, Hampton, VA 23681
Voice: 804-864-2044,   FAX: 804-864-7793,   Email: [email-masked]
PGP 2.0 Public Key now available -- Consider it an envelope for your e-mail

---

From: [email-masked] (Michael T. Palmer)
Date: 11 Dec 92 17:42:32 PST

>maneuver, the F/O full-right, and the net result will be an algebraically

I believe this is incorrect, though I don't have the documentation here
right now.  My understanding is that whenever one of the sticks reaches
a critical percentage of deflection (say, 75%), it becomes automatically
the selected input device.  At this point, the other control stick is
ignored.  So it's a race.  Whoever slams their stick to the stops first
wins, and the only way for the other crewmember to override is to physically
attack the winner.  Neat, huh?

I'm not sure how sub-critical deflections are handled - they may indeed
be algebraically summed.  If any Airbus people can provide the straight
scoop, I'd appreciate it.

In the sidestick implementations used at NASA, the sticks are interconnected
("logically", really, since they are hydraulically back-driven) so that,
like in current cockpits, whoever is strongest (i.e., most scared-to-death)
wins.

---

From: [email-masked] (Philip Peake)
Date: 11 Dec 92 17:42:32 PST

In article <[email-masked]>, [email-masked] (Robert Dorsett) writes:
|> 
|> >If all new pilots were taught nothing but the side stick,
|> >how long would the old arangementy last - and if the old arangement
|> 
|> Why should pilots be taught nothing but a unique, *proprietary* side-stick 
|> design that no pilot had any experience with before four years ago, and which 
|> is only one of a variety of other possible designs?  

You are avoiding the question - read it again, the operative word is "if".
I really don't think that a side-stick qualifies as "*proprietary*" does it ?
Does Airbus hold patents on some aspect of it ? (I don't know the answer to
this one - but if that IS true, then the result would be proprietary, and
would deserve to fail).

Changing the subject slightly, the world's safest aircraft (Concorde) uses
technology which was new, and for a time unacceptable to various licensing
authorities - it didn't have a MECHANICAL link between the stick and the control
surfaces - only hydraulic. There was *much* concern over this, and lots of
reaction from the pilots and safety mob - they almost won, and the Concorde almost
had to be produced with a mechanical linkage, which no FULL CREW would be able
to budge one mm if they all tried together - in fact, the linkages would probably
have failed, before it would have been possible to move a control surface, when
moving at full speed.

As I said, it has proved to be the worlds' safest aircraft.
Presumably, had a few airlines other than BA and Air France used them, someone
would have flown one or two of them into the ground, and we would be arguing
(or would have been arguing) about the safety of aircraft with no mechanical
backup systems.

Technology changes, old interfaces eventually HAVE to give way as they begin to
fit less and less well with the new technologies.

I don't seem to have noticed any raving about the TGV, the latest versions of
which achieve speeds comparable to that of aircraft, and use a side-stick ...
(yes, I know, French again ...) There is MUCH more prior art in train design,
and they can write off considerably more people than even a fully loaded 747/400
if something goes drastically wrong.

Philip

---

From: Robert Dorsett <[email-masked]>
Date: 13 Dec 92 12:14:14 PST

In article <[email-masked]> [email-masked] 
(Philip Peake) writes:

> |> design that no pilot had any experience with before four years ago, and 
> |> which is only one of a variety of other possible designs?
> 

Not if one views it merely as a "substitute" interface.  The A320 sidestick
is not a "parallel" substitute: it's a replacement design concept. 
Besides the ergonomics, which raise their own issues, and which, as you note,
would be duplicated by just about any manufacturer attempting to develop its 
own, it's what it DOES that determines its uniqueness.

For instance, some pilots seem to like a specific feature: pull straight 
back on the stick to activate the TOGA mode.  A few pilots *prefer* this to 
the regular stick-throttle combination one would instinctively use in such 
modes, despite the fact that if you did this on a "real" airplane, you'd
soon stall it.

So, should Boeing adopt this paradigm, if it goes to a sidestick design?  This 
is one of MANY unique characteristics that solely characterize *Airbus'* 
sidestick.  There are no official standards; no "sidestick specification" is
in the public record.  The software is jealously guarded.  If Boeing decides 
to duplicate the stick concept, should it do so by examining operating manuals 
and hope it catches most of the idiosyncrasies?  Or should it run away with 
the *idea*, and improve on it, offering its own version?  

In many ways, what I fear is what happens with "consumer software."  Take a 
word processor, for instance: a simple idea, with *many* variations.  Different
companies have different ways of looking at the same problem: indeed, none of
them may be a "best" solution.  I don't think this comparison is off base: 
Airbus has REPEATEDLY and PUBLICLY stated that its technology is its selling 
point: to distinguish itself from Boeing, it MUST continue to do its own 
thing.  

The problem is that software is so much more easily changed than hardware, 
that we could very well start an avionics equivalent of "creeping featurism."
Changing the way a stick behaves can be done in just one firmware update: no 
need to develop new tooling, production techniques, train assemblers and
maintenance engineers, offer the retrofit during the next C check, etc.  
Just the internal development process, which one can assume is faster and 
cheaper than for hardware.  But, by virtue of this ease, it's also more 
*unstable* than hardware-based solutions.

Evidence to support this position?  The A320 has about 4M of code.  The A330/
A340, 10M.  It's happening as we speak...  

Do any Honeywell people reading know how big the 777 EFCS is going to be?

> reaction from the pilots and safety mob - they almost won, and the Concorde 
> almost had to be produced with a mechanical linkage, which no FULL CREW would 
> be able to budge one mm if they all tried together - in fact, the linkages 
> would probably have failed, before it would have been possible to move a 
> control surface, when moving at full speed.

I think you're overstating the situation considerably.  Like they'd build
an unflyable mock-up?   :-)

In the late 1950's and 1960's, there was considerable controversy over 
hydraulics, much of it justified: there was a low confidence level among 
pilots with conventional hydraulic systems.  O-ring seals tended to break 
down, and the systems were rather "leaky"; many a flight had at least a 
partial failure.  Pilots fully realized the benefits of hydraulics, and,
starting after the 707, accepted the desirability of flying by hydraulics.
However, what a lot of pilots wanted was a hybrid system, fly-by-cable, 
COMBINED with hydraulic boost.  So, for instance, the 727 was developed with 
full-time hydraulic flight controls, but also a cable-driven "back-up" mode, 
which used control tabs to aerodynamically move the surfaces.  When hydraul-
ics were completely lost, controls became heavy, but the airplane had a 
"get it on the ground" capability.  The 727 was the last such airliner to
have this capability.

Much of the controversy surrounding the BIG airliners, such as the 747, but
even the 737, was that the manufacturers wanted to take away these tabs.
This debate was an important part of an industry-wide *process*, which helped 
induce the manufacturers to develop more reliable systems: a 747 with the 
hydraulics reliability of, say, a 707, would not have been acceptable.  This 
technological advance, combined with the *necessity* of using it in the 
specified mission profiles, helped silence objections.

So Concorde certainly wasn't the first to go all-hydraulic, and the debate
didn't start there.

I can't comment on Concorde-ish control forces, but on even the 747, the
"raw" forces in cruise, while high, don't require superhuman effort: the
figures I've seen ranged from 50 lbs to 150 lbs.  This would be unacceptable
for normal operations, but is hardly the equivalent of trying to lift a 
ton of cement with one's little finger.

> As I said, it has proved to be the worlds' safest aircraft.

Sure, 14 airplanes, piloted by superbly qualified and trained aircrews, 
with immaculate and detailed maintenance.  Flying what, TWO flights a day (no,
not two per plane, two FLIGHTs, in the fleet) on 2 or so very well-defined 
routes, to major international airports?

Concorde's an interesting experiment, but let's face it: its contribution is
merely that it can be done, not that it can be done economically, or, even,
safely, in the same types of conditions other airplanes are flown in.  It is,
however, an engineering achievement that France and England can be proud of,
and I hope British Airways and Air France continue turning their Concorde
profits, if, for nothing else, the living history the airplane represents.

> which achieve speeds comparable to that of aircraft, and use a side-stick ...

You will no doubt be DELIGHTED to note that I know nothing about trains.  
Nor do I particularly care to learn. :-)  My interest here is airliners, not
mass transportation.  I'd suggest we compare standards within the genre.

--
Robert Dorsett
Internet: [email-masked]
UUCP: ...cs.utexas.edu!rascal.ics.utexas.edu!rdd

---

From: Robert Dorsett <[email-masked]>
Date: 13 Dec 92 12:14:17 PST

In <[email-masked]> [email-masked] (Michael T. Palmer) writes:

> >On the A320, there is no interconnect between the

> attack the winner.  Neat, huh?

I've looked into this closely.  Unless there have been significant, recent
changes, it doesn't work this way (other designs do, though).  Here's an 
excerpt from the impending A320 paper that Pete Mellor and I are writing
("The A320 Electronic Flight Control System," title subject to change), which 
might help clear things up.

I've inserted a couple of comments in brackets; these clarify passages,
based on respondent comments.

---------------------------

4.1.  Sidesticks; [AIRB88, 1.09.20, 3-5; ZIE86, COR88]

The main flight control interface for the EFCS is one of two
"sidestick" controllers.  Conventional airplanes have two "control
columns," mounted between each pilot's legs.  The A320 does away with
these, and instead has sidesticks mounted on the side-walls of the
cockpit (incidentally resulting in outstanding pilot visibility of
flight instrumentation).

Conventional control devices reflect control forces to some degree. 
This "feel" is usually either supplied aerodynamically by the airplane,
or, as in most airliners, via an artificial feed-back system.  The
sidesticks on the A320 do not have artificial feel.  On the A320,
springs are used to discourage abrupt control movements.  Flight
control specialists seem to regard this as a valid "artificial"
feedback mechanism, but the point must be emphasized that the pilot is
only reacting to the qualities of the spring: no tactile feedback
relates to what the airplane may be doing (unlike a conventional
control system); thus, secondary cues, such as the design of the flight
displays, take on more importance.  

[...]

Following are some of the force-characteristics of the sidesticks on
the A320 [adapted from COR86]:

Limits:
                    	                 Roll            
                 Pitch            In          Out        
Max.  load       10 daN           3 daN       2 daN        
Threshold        0.5 daN          0.4 daN     0.4 daN    
Deflection       +-16 deg.        20 deg.     20 deg.    
Orientation      20 deg fwd.      12 deg in   12 deg in.    

Proper pilot arm position is important for proper use of the sidestick. 
[actually, not that important: an early concern that proved unjustified] 
Thus, Airbus has included a fully-adjustable seat-arm, which features
an LCD readout for arm angle.  A pilot entering an aircraft need only
remember his optimal settings, and set them up.  The arm-rest rest
position may be changed within an interval of [+20,-15] degrees. 
Supporting arm position may be adapted in the interval of [+15, -12]
degrees.  

The sidesticks are not mechanically interconnected: inputs to one can't
be felt on the other.  Their inputs are algebraically added, with a
maximum limit corresponding to the maximum deflection of one sidestick.
No weight is given to the captain.  Thus, if the captain pulls full
left, and his first officer pulls full right, the net effect is zero. 
The last pilot to click on an override thumb-button (also used to
disconnect the autopilot) obtains control: a small indicator light in
front of the other pilot signals this fact.  The potential exists for
the pilots to "fight" over control of the sidesticks.  Rather than the
"strongest" pilot winning, the one with the fastest thumb will win.  If
the override button is held down for more than 30 seconds, it will
"deactivate" the other sidestick.  If the deactivated sidestick's
override button is pushed, it will re-activate.

This scheme has been the subject of much criticism from pilots: it is
widely felt that one pilot should feel what the other pilot is up to,
through the stick.  Inter-pilot communication in an emergency may also
be enhanced through better tactile feedback [PIK88, HEL86, SUM87].

Note that there is no trim control on the sidestick, since this is
normally handled by the Normal and Alternate control laws (see below). 
In Direct law, pitch [trim!] must be set through controls on the center 
control pedestal.  

The only other button, besides the override switch, is a push-to-talk
trigger, for the radios.

The sidesticks are not merely a different interface, otherwise causing
the same functional effects as a conventional airplane.  The pilot's
role in flight management is fundamentally changed, depending upon the
mode the flight control computers are in.  For example, in Normal Law,
which is what the airplane is normally flown in (see below, 5.1), in
a turn, a pilot must normally pull back on the stick, to compensate for
lost lift.  On the A320, this is not necessary: the pilot just moves
the stick in the direction he wishes to turn, and the airplane will
turn, automatically supplying the necessary elevator to maintain
altitude [HOP87].  The sidestick is more of a "flight path command"
interface, rather than a conventional "flight control surface
deflection" interface.  If, that is, the appropriate computer support
is there: if not, the same sidesticks are used with one of the other
"redundant" control laws, which are much more conventional in design. 
This raises an interesting issue of whether a pilot, who, with a
properly-functioning system, will fly in "Normal" law almost all the
time, will be "current" enough to satisfactorily fly the airplane in a
significantly degraded mode, more akin to conventional control laws. 
This issue is addressed in training, not the interface.

AIRB88    Airbus Industrie/Aeroformation, Flight Crew Operating
Manual, 1988.  

COR88    S. G. Corps, "Airbus A320 side stick and flyPbyPwirePPan
update," Society of Automotive Engineers Paper 861801. [Very GOOD
paper]

HEL86    Peter H.  Heldt, "Airline requirements on a fly-by-wire
aircraft--a pilot's view," Society of Automotive Engineers paper 861804.
[so-so]

HOP87     Harry Hopkins, "Simulating the A320," Flight International,
12 September 1987. [good article, weak on this issue]

PIK88    J.  R.  Pike, "A320 in service--initial report," British Air
Line Pilots Association, July 31, 1988. [extensive comments]

SUM87    L.G.  Summers, et.  al., "Fly-by-wire sidestick controller
evaluation," a paper presented at the SAE Aerospace Technology
Conference and Exposition, Oct.  5-8, 1987. [ this is a decent overview
of the MANY options available ]

ZIE86    Bernard Ziegler, "Front seat on the future," Aerospace
America, April 1986. [nicely-illustrated pap]

----------------------

How accurate is all this?  Besides the cited sources, I've run into
several other comments on the "algebraic" nature of the sidesticks.
I haven't tried a neutral deflection in a simulator, but a recent email
comment indicated that pilots, while trying to avoid an aircraft on the
ground, commanded opposite inputs, thus leaving the flight path 
unchanged.  If true, this would also tend to support the "algebraic,"
additive nature of inputs.

In addition, of the A320 pilots who have reviewed the paper thus far,
none have contested this point.  One pilot did raise the issue that
later transition work isn't as difficult as might be gathered from the
last paragraph.  So far, this is a minority viewpoint.

---

From: [email-masked] (Clemens Emmanuel Tillier)
Date: 13 Dec 92 18:07:13 PST

[email-masked] (Philip Peake) writes:

(discussion about control technologies deleted)

>if something goes drastically wrong.

This may be a little bit off the subject, but I think comparison with the TGV
is unwarranted. The engineer in a train has control over only one degree of
freedom of motion; the pilot in an aircraft has control over all three. It is 
therefore not surprising that entrusting so much control to one component will
cause some questions.
Besides, the TGV is utterly devoid of any control sticks... It uses the same
throttle control as previous French locomotives (a horizontal wheel).
Commercial TGV speed (300 kph) is not quite comparable to airliner speed. The
maximum speed ever achieved by a TGV (515 kph) is also lower.

Clem <[email-masked]>

---

From: [email-masked] (Michael T. Palmer)
Date: 14 Dec 92 14:11:43 PST

>might help clear things up.

Okee dokee.  You're right; I must have been remembering the specs for a
different system.  I can now recall the stories about the thumb switch for
overriding the other stick (my officemate and some of our test pilots
participated in a week of A320 training down in Florida last year).  Their
reaction to it sparked quite a lengthy debate about the various sidestick
implementations.

Personally, the lack of feedback about what the other crewmember is doing
is just astounding.  Does nobody remember their flight training?!?  How
do you think your instructors (or YOU, if you teach) were able to know what
you were doing even before the aircraft responded to your inputs?  Tactile
feedback can be a powerful and rich source of information.

And when, pray tell, would an algebraic sum of the control inputs be the
desired method of responding to the flight crew's actions?  Did the
designers think that the pilots would agree that the captain would only
move his stick left/right and the first officer only fore/aft?  "I'll be
the base of the triangle, you be the height, and we'll let the EFCS do the
hypoteneuse!"  (For those with a math/statics background:  "I'll be the
i, you be the j, and we'll let the EFCS do the resultant vector!").

My point is that if the crewmembers are trying to do something different,
the system should make that MORE not LESS visible.  Otherwise, when the
aircraft does not respond as they expect it to, each crewmember will simply
increase the magnitude of his control input without really understanding
what the h--- is going on.  I guess this is what Reason would identify as
a "latent system error."  The pilots will eventually make an error; yep,
the designers made sure of that.

---

From: [email-masked] (Ken Hoyme)
Date: 16 Dec 92 14:00:45 PST

> Do any Honeywell people reading know how big the 777 EFCS is going to be?

Well, this is an apples-to-oranges comparison.  I can only speak (and
only in vauge terms, of course) about the portion of the 777 that
Honeywell is producing.  Honeywell's Airplane Information Management
System (AIMS) contains the FMS function similar to previous generation
airplanes, but does not encompass the autopilot (Rockwell Collins) nor
the FBW Flight Controls (GEC).  The FMS alone requires about 2Mbytes of
executable code.  It also requires a Nav Data Base and RAM for
operation.  I do not know the complexity of the other components of the
"EFCS".  Of course, Displays could be considered another part of the
system.  That function lives in AIMS on the 777.