The Risks Digest

The RISKS Digest

Forum on Risks to the Public in Computers and Related Systems

ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

Volume 8 Issue 57

Saturday 15 April 1989


o H.D. Thoreau on Risks of Believing Computations
Jim Haynes
o Airbus 320
Brian Randell
o 1,000 Pilots Face ban
Dermot Williams
o RFI and elevators
Robert A. Morris
o Electronic Truant Officers
Carolyn M. Kotlas
Michael R. Hoffman
Ed Robertson
o Re: Computer CAN attempt to defraud you
Hugh Davies
o Computer maliciousness
Peter da Silva
o Info on RISKS (comp.risks)

H.D. Thoreau on Risks of Believing Computations (RISKS-8.56)

Jim Haynes <haynes@ucscc.UCSC.EDU>
Thu, 13 Apr 89 22:08:56 -0700
This reminded me of an anecdote in one of the early books about computers,
which was used to illustrate Babbage's insistence that the Difference Engine
should produce as output plates for printing the results, lest someone's error
in copying/typesetting introduce an error. (Might have been the book "Faster,
Faster" by W. J. Eckert.)

  There was a brief period in which England and Spain were on good terms with
  each other.  An English admiral invited a Spanish admiral aboard his flagship
  for a visit, during which he presented the visitor with a beautifully bound
  copy of the English navigational tables.  After the visit the Spanish fleet
  sailed away and was never heard from again.  It seems the English never used
  their own navigational tables, knowing them to be full of errors; they always
  used the French tables.
                                   [Turn the tables on the fleet afoot?  PGN]

Airbus 320

Brian Randell <>
Fri, 14 Apr 89 18:28:29 BST
I recently obtained - from Bev Littlewood - a copy of an article in
France-Soir for 18 February about computer-related problems of the Airbus
320.  In case it can, despite the passage of time, still add usefully to the
information that has been made available in the Anglo-Saxon (French for UK
plus US!) press, I am providing an almost complete translation, in which I
have endeavoured to retain the flavour and style of the original article.
(My apologies for the amateur nature of the translation and of the
inadequacy of the dictionary that I had available to me at the time!)

Brian Randell, Computing Laboratory, University of Newcastle upon Tyne

  of the Incidents which has caused Aerospatiale to return the machines to 
  "marbre" [?]

Less than one year after it first went into service, the Airbus A320, the
most sophisticated civil airliner existing, has to go back to the "marbre"
[?]. A simple revision after thousands of hours in the air?  Not just that!

After going into service in April last, the plane is "chouchoute'"[?]  by
its builder, Airbus-Industrie, and the air lines. All the improvements
capable of being made to the latest Airbus are made under the control of
DGAC (Direction Ge'ne'rale de l'Aviation Civile). "The A320, like all new
machines, is in its period of debugging ["de'verminage"]," emphasized Daniel
Tenebaum, the boss of DGAC. "It is above all a question of removing faults
which have appeared since it first went into service."


During critical phases - landing and take-off - the computer system shows only
the most dangerous alarms. "This is a wretched problem", explained an Air
France captain, "Certain failures are recorded by the computer, but the pilots
are informed only later".

Paul Baud, the flight trials director of Airbus-Industrie explains:  "To ease
the task of the pilot, only the problems which relate directly to critical
phases are communicated to him: fire in the engines, the baggage hold, or in
the toilets."

But there are worse ones. The computer system (nicknamed the "Little Genius")
sometimes escapes from the control of the crew. "I am going to land at Geneva
in my A320, and it happens that the altitude indicators show `hauteurs
farfelues' [incorrect heights?]. Luckily the airport urgently advised me of
this. Otherwise we would have flown straight into the mountain!" Immediately,
the captain demanded that the computer be replaced as being not completely

Worse. The case of the pilot who saw with horror his computer indicating "full
fuel load" when he started his descent to the airport in West Berlin.  And the
famous "Little Genius" refused to let him take over manual control.  "We very
nearly had a catastrophe", said the pilot.

The cause, it seems, is the electrical power supply. "We have screened[?] all
electrical resistances" ["Nous avons passe' au crible l'ensemble des
re'sistances"], insists Paul Baud. "There was though a failure. Henceforth, the
on-board computers will be fitted with higher performance diodes."


They will even improve the transformers-rectifiers. These serve to supply the
A320's automation systems, in modifying the the alternating and the direct
current. Nevertheless, Airbus-Industrie points out that all the flight-critical
mechanisms are duplicated. One defective computer is thus immediately replaced
by its twin.

[Paragraphs about complaints regarding noise-levels in the A320, and plans
regarding improved sound-proofing.]

1,000 Pilots Face ban

Fri, 14 Apr 89 19:01:33 GMT
From Dublin's EVENING HERALD of Thursday 13th April, without permission:

 "1,000 Pilots Face Ban"

 The US Federal Aviation Administration said it planned to suspend or revoke
 the licences of more than 1,000 pilots who lied about past alcohol or drugs

 The FAA said about 10 per cent of them were commercial airline pilots and the
 rest were private pilots.

 The FAA said it got the names of more than 6,000 pilots through a computer
 match of medical applications, criminal records and state motor vehicle

Any of the pilots on the list care to comment?  Do you feel that this is a fair
or foul use of computer databases?

Dermot Williams, University College Dublin, Dept. of Computer Science

    [In an effort to make sure we stick to the computer risks, and not compete
    with the aviation BBoards on technical nuances, I suggest that some of the
    pending submissions to RISKS might better be redirected elsewhere.  This
    item is clearly a computer database problem, not an aviation problem.  PGN]

RFI and elevators

Robert Morris <ram@typo.UUCP>
Thu, 13 Apr 89 22:09:59 EDT
Dave Horsfal writes in Risks 8.54:
  I have a little hand-held (amateur) transceiver, generating just 3 watts on
  147 MHz from a "rubber duck" antenna - very inefficient.  When I'm in the
  mood, I trigger it next to various bits of electronic equipment, just to test
  their RF susceptibility. ...

This is distressing behavior from a licensed amateur radio operator.  In the
US, this might subject one to revocation of the license and possibly criminal
penalties if the action caused damage or injury. In the US, amatuer radio
transmissions are restricted in purpose, and testing RFI rejection of
commercial equipment is not one of them.  Even if the manufacturer were wholly
negligent in their RFI rejection, the amatuer ``investigator'' of this fact
could reasonably be expected to understand the consequences of probing this
inadequate security.  For example, I rather doubt that any one would make such
an investigation of, say, someone's pacemaker. In my opinion, amatuer radio
operators have approximately the same responsibility as did the author of the
Internet worm. They have substantial technical knowledge and good reason to
believe that their action could cause malfunction, and in this case, possible
                                     Robert A. Morris     KA1BWN

    [Robert Morris was a signer of the Declaration of Independence.
    We have now had at least FOUR different namesakes contributing to or
    discussed in RISKS.  I hope no one is confused.  PGN]

Electronic Truant Officers (Re: RISKS-8.56)

Carolyn M. Kotlas <>
14 Apr 89 12:40:53 GMT
My daughter's high school (and several others in this area) has had such a
notification system in place for several years.  I don't know how much a part
the school's computers play in this, but the notification is in the form of a
telephone call to the home and a generic recording that is played.  Something
along the lines of "Your child was reported absent in one or more of his/her
classes today." The source of problems (or "risks") of this system is human,
not computer-based.  Every time I received the recording, my daughter's absence
was excused, usually because of a school field trip that had been approved by
the school; so if there's poor coordination between teachers and
administration, parents will receive false alarms.  (Which, like too many cries
of "Wolf!" may lessen a parent's belief in any real reports of absences.)
Also, since the calls are usually generated at a predictable time in the
evening of the absence, truants could just take the call for the parent and
report it as a wrong number.  (I've also heard of people without children
getting these calls, either due to typos in the student's records or misdialing
of the number.) So much for an infallible reporting system here. 

 --Carolyn Kotlas, UNC-ECS, Research Triangle Park, NC 

Re: Electronic Truant Officers

Michael R. Hoffman <h44394@leah.Albany.EDU>
Fri, 14 Apr 89 13:13:43 EDT
    When I was in my Sophomore year at The Bronx High School of Science,
they implemented a computerized attendence scheme.  Every student was given a
number (welcome to the real world... forget your name, you are now ####) which
was used to trace the student through their years at school.  When attendence
was taken in classes and in Homeroom, the teachers would fill out "bubble"
sheets which were passed through a scanner to the central computer, which was
located somewhere in Manhatten!
    They quickly found many problems in the system.  Errors in filling in
the wrong bubbles, the computer crashing, students forgetting their number, and
students who would cut Homeroom (which meant "Absent for Day") yet were not
marked absent in certain classes, really screwed the school administration up.
    And, as with most other computer systems, there were ways around the
system.  Supposedly being the "brightest students in the country" (YEAH,
Right!! :-}), you can imagine the fun we had beating it.
    In a word, computerized school attendence systems are a JOKE! And they
don't help with convincing the students that are REAL people, not just cogs in
the system.

Electronic Truant Officers (Re: RISKS-8.56)

Ed Robertson <>
14 Apr 89 23:00:24 GMT
One evening last week the phone rang and I answered to hear a sepulcral
electronic voice announce that my son, whom I know was in school, had been
absent from all of his classes that week.

The best part of this system, from the schools point of view, is
that there's not even any chance to question that electronic voice.

Edward Robertson, Computer Science Dept, Indiana U., Bloomington, IN 47405-4101

Re: Computer CAN attempt to defraud you

14 Apr 89
linden@Sun.COM (Peter van der Linden) asserts that a computer can defraud
you. His story about the pie factory is seriously flawed.

1) The computer is just a tool. You are being defrauded by the management of
the pie factory, in the same way you are defrauded by the taxi driver who short
changes you rather than by his taximeter.

2) Weights and measures are controlled by legislation. It may be immoral to
take advantage of the loopholes in that legislation, but it is not dishonest.
If the law is unsatisfactory, get it changed.

3) In the pie factory case, before automation, 50% of consumers of a 4oz.  pie
were getting *more* than they had paid for. I wonder how many of them wrote to
the factory to offer more money?

4) Computer weighing systems do *not* allow "an accuracy hitherto unobtainable".
(I wrote potato chip weighing systems for two years for a living). What they
generally do is allow repeatability in weighing, i.e., a narrowing of the
distribution curve of the weights dispensed, which then allows a slight
reduction in the 'set-weight', at an enormous saving to the producer, spread
over millions of items, but a minimal impact on the consumer of a single item.

5) Peter says "if the pie was a "4oz" pie, the bakers were permitted to range
from 3.5 to 4.5oz". This sounds unlikely to me. I am not familiar with American
weights and measures legislation, but the law is usually either formulated such
that *no* pie may weight less than 4oz - which means that the average pie must
actually weigh 4oz plus twice the standard deviation of pie weight (at least -
depends on how assiduous you want to be in avoiding prosecution!), or there is
some kind of limit on what proportion of pies may weigh less than the marked
weight. If the control is merely on the average weight, given two pies, I'll
have the 8oz pie and you can have the empty carton! In either case, it is in
the manufacturers interest to reduce the standard deviation as much as
possible, which is what the computer allows. In fact, the real problem is not
weighing the pies, or whatever, but accurately dispensing the filling. In the
EEC, all products are divided into two categories, 'easy to pack', and
'difficult to pack' with the former having tighter controls than the latter.

When I was weighing potato chips, one of the things we did was make sure each
and every packet had at least the legal minimum content. This goes part-way
towards ensuring that every consumer gets what he paid for.

Hugh Davies

Computer maliciousness (Re: RISKS-8.56)

Fri, 14 Apr 89 13:38:50 -0400
Having been roundly chastened for claiming that a computer can not be
malicious, let me explain this point more fully. A bank may have policies that
are malicious, and may embody these policies in a computer program.  I would
not deny that... the point I'm making, though, is that the computer software
can be assumed to embody the policies of the bank. Subject to bugs and design
flaws, of course, but it's the bank's policies.

An agent of the bank, then, has a reason to stand by the computer:

  While the software may have bugs, they can be reasonably certain it is not
  intended to defraud the bank. So long as the bank has reasonable policies,
  they can also assume that there's nothing in the program intended to
  deliberately defraud its customers. They have no such certainty about the
  customers themselves.

The problem comes when a customer has documentation to substantiate his
or her claim, or they know there's a bug, and they still don't act.

Peter da Silva, Xenix Support, Ferranti International Controls Corporation.

Please report problems with the web pages to the maintainer