Sweden Fighter Crash

Sweden Fighter Crash

[Peter Juhl]

Last week Bjarne Stroustrup posted something about the fighter
that crashed in Sweden. Eventhough his main point was about
the difficulty of comparing languages, and the traps that people
fall into when they do so, there was some follow-ups about the
crash as such.

Somebody from Sweden expressed doubts about Bjarne knowing anything about
what caused the failure, which Bjarne attributed to software.

This just came in on the apnews

	   STOCKHOLM, Sweden (AP) _ Sweden's new jet fighter crashed during
an air show last week because of a computer flaw, an inquiry board
said Wednesday in clearing the pilot of blame.
	   Producers and military officials had been aware that vigorous
movement of the control stick could cause the JAS 39 Gripen to go
out of control because of computer overcompensation. But they
underestimated the problem, the government board said in a
preliminary report.

[ ... stuff deleted ... ]

I'll just point out that Bjarne has a lot of contacts all over the world,
and probably got a tip from friends in Sweden. 

--- peter (peju@research.att.com)

Re: Sweden Fighter Crash

[Step he Leake]

In article <26347@alice.att.com>, peju@alice.att.com (Peter Juhl) writes...
> 
>Last week Bjarne Stroustrup posted something about the fighter
>that crashed in Sweden. Eventhough his main point was about
>the difficulty of comparing languages, and the traps that people
>fall into when they do so, there was some follow-ups about the
>crash as such.
> 
>Somebody from Sweden expressed doubts about Bjarne knowing anything about
>what caused the failure, which Bjarne attributed to software.
> 
>This just came in on the apnews
> 
>	   STOCKHOLM, Sweden (AP) _ Sweden's new jet fighter crashed during
>an air show last week because of a computer flaw, an inquiry board
>said Wednesday in clearing the pilot of blame.
>	   Producers and military officials had been aware that vigorous
>movement of the control stick could cause the JAS 39 Gripen to go
>out of control because of computer overcompensation. But they
>underestimated the problem, the government board said in a
>preliminary report.
> 
>[ ... stuff deleted ... ]
> 

This sounds more like a bad value for a gain parameter, causing the control
system to go unstable, rather than a flaw in the program or compiler. I work
with real-time control systems; there are  many things that can go wrong even
after the compiler and algorithm bugs are all found!

If it is a bad gain, then it is the control engineers, not the software enginee
rs,
who are at fault. Let's not assume everything is a software fault just because
we are software people!

Stephen Leake	NASA Goddard Robotics Lab
internet : nbssal@robots.gsfc.nasa.gov

Re: Sweden Fighter Crash

[Alex Blakemore]

In article <26347@alice.att.com> peju@alice.att.com (Peter Juhl) writes:
 
> Somebody from Sweden expressed doubts about Bjarne knowing anything about
> what caused the failure, which Bjarne attributed to software.

we all appreciate Bjarne's comments in this forums.

he claimed that the avionics software was written in Ada
which a subsequent poster said was not true.

that correction (assuming it was valid) was wholely appropriate.
-- 
Alex Blakemore       alex@cs.umd.edu        NeXT mail accepted
--------------------------------------------------------------
"Without an engaged and motivated human being at the keyboard,
the computer is just another dumb box."      William Raspberry

Re: Sweden Fighter Crash

[Bjorn Kallberg]

In article <26347@alice.att.com> somebody from somewhere wrote:

>
>Last week Bjarne Stroustrup posted something about the fighter
>that crashed in Sweden. Eventhough his main point was about
>the difficulty of comparing languages, and the traps that people
>fall into when they do so, there was some follow-ups about the
>crash as such.
>
>Somebody from Sweden expressed doubts about Bjarne knowing anything about
>what caused the failure, which Bjarne attributed to software.
>

Bjarne argued, that a single software bug should not be the base for
comparing languages. We all agree to that. Then he compared the ATT
failure, (where we all have seen the code lines that was the cause of
that bug) and compared it with the fighter crash, and attributed the 
crash a bug in the software, which he claimed to be written in Ada.

I pointed out, that this example was unfortunate, as

1: It was not written in Ada. (which I knew at that time)

2: That is was a bit premature to attribute the crash to a soft-
   ware bug. (At that time no reliable information was available
   to the reason for the crash)

>This just came in on the apnews
>
>	   STOCKHOLM, Sweden (AP) _ Sweden's new jet fighter crashed during
>an air show last week because of a computer flaw, an inquiry board
>said Wednesday in clearing the pilot of blame.
>	   Producers and military officials had been aware that vigorous
>movement of the control stick could cause the JAS 39 Gripen to go
>out of control because of computer overcompensation. But they
                           =========================

Do you call this a programming bug? 

>underestimated the problem, the government board said in a
>preliminary report.
>
>[ ... stuff deleted ... ]
>
>I'll just point out that Bjarne has a lot of contacts all over the world,
>and probably got a tip from friends in Sweden. 

Now that the preliminary reasons for the failure are clear, it seems
to be even more certain, that as an example of an Ada software failure
corresponding to the ATT software bug, this was not the best example.

>
>--- peter (peju@research.att.com)


Bj|rn K{llberg

Re: Sweden Fighter Crash

[david.c.willett]

>From article <25auuq$832@gopher.cs.uofs.edu>, by bill@triangle.cs.uofs.edu (Bi
ll Gunshannon):
> In article <1993Aug23.091155.7738@celsiustech.se>, bjkae@celsiustech.se (Bjor
n Kallberg) writes:
> |> >This just came in on the apnews
> |> >
> |> >	   STOCKHOLM, Sweden (AP) _ Sweden's new jet fighter crashed during
> |> >an air show last week because of a computer flaw, an inquiry board
> |> >said Wednesday in clearing the pilot of blame.
> |> >	   Producers and military officials had been aware that vigorous
> |> >movement of the control stick could cause the JAS 39 Gripen to go
> |> >out of control because of computer overcompensation. But they
> |>                            =========================
> |> 
> |> Do you call this a programming bug? 
> |> 
> 
> Unless the computer "overcompensated" of it's own volition, yes, I call 
> that a programming bug!!
> 
> The only thing left is to get a definitive answer as to wether or not the 
> applicable code is written in ADA.
> 
> Of course, in either case (this one or the AT&T one) neither is an indictment
> of the language.  Only an example that programmers make mistakes and no
> language can prevent all of them.
> 
> bill
> 
> -- 
> Bill Gunshannon          | "There are no evil thoughts, Mr. Rearden" Francisc
o
> bill@cs.uofs.edu         |  said softly, "except one; the refusal to think."
> University of Scranton   |
> Scranton, Pennsylvania   |         #include <std.disclaimer.h>   

Why do you call it a programming bug?  Perhaps it was a "system error" in that
the feedback loop to the control surfaces wasn't tight enough?  Sheesh...
I've seen less "Monday morning quarterbacking" in campus sports bars.

Two points --

	The report cited above is from AP, hardly a technical source.  Blame
the crash on a "computer problem" and the public breathes a sigh of relief.
We don't know what the root cause is, and can't until the final report of the
investigating team is in.

	Probably the computer and fly-by-wire software was involved.  It's a
fighter, folks.  The plane is probably inherently unstable.  Just because 
the software was part of the loop, doesn't make it defective.  Perhaps the 
pilot overstressed the system.  Again, we don't know.  Let's not indict 
something without evidence.


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Dave Willett          AT&T Federal Systems Advanced Technologies

The biggest mistake you can make is to believe that you work for someone else.
			
			-- Anonymous