Newsgroups: comp.risks
X-issue: 5.40
Date: Mon, 28 Sep 87 18:17:33 EDT
From: mnetor!utzoo!henry@uunet.UU.NET (Henry Spencer)
To: RISKS@csl.sri.com
Subject: Concorde tires burst: RISKS without the automatic system

Flight International for Aug. 29 reports that a British Airways Concorde
burst five tires on landing at JFK on Aug. 11.  Nobody was hurt and no
emergency evacuation was necessary, but two engines were later replaced
as a precaution because they had ingested debris.  (If the Concorde was
being designed over again, in hindsight one definitely would not put the
landing gear directly in front of the engine intakes!)  The interesting
part is the reason for the tirebursts:  the main hydraulic system was
down due to a "minor fault", leaving the brakes on the standby hydraulic
system... which has no antiskid control.  The disturbing aspect here is
that the crew evidently had come to rely completely on the antiskid
braking system.  Unless, perhaps, the pilots were unaware that they were
back to "dumb" brakes -- seems unlikely -- it's disturbing that they made
such a drastic error in braking procedure.  These were not second-rate
pilots, by the way; my understanding is that the Concorde is the most
sought-after assignment in BA, and it is likely to have BA's best crews.

				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry

Newsgroups: comp.risks
X-issue: 10.34
Date: Fri, 7 Sep 90 14:27:22 EDT
From: henry@zoo.toronto.edu
Subject: Re: "wild failure modes" in analog systems

>... we would never attempt to build systems of the complexity
>of our current digital systems if we had only analogue engineering to rely on.

Unfortunately, this is not entirely true.  Very complex analog systems were
not at all unknown in pre-digital days.  Concorde's engine computers are
analog circuitry, which makes them a maintenance nightmare by modern
standards -- each setting interacts with others, so readjusting them
is a lengthy and difficult chore.  (It is not worth developing a digital
replacement for such a small number of aircraft.)  For another example,
I believe the US Navy's four ex-WWII battleships are still using their
original *mechanical* analog fire-control computers.  For still another,
although the recent fuss about fly-by-wire systems for aircraft has
focused mostly on digital versions, analog fly-by-wire systems were
not at all unknown:  Avro Canada's Arrow interceptor was flying at
Mach 2 with analog fly-by-wire in 1958.

Certain jobs simply require complex systems, and will be done one way or
another.  It is probably true that digital implementations make it easier to
add *unnecessary* complexity, but they also make it easier to do a better and
(potentially) more foolproof job on the basics.  This argument has many
parallels to the old ones about whether word processors lead to poorer writing,
or whether 16-bit address spaces forced better programming.  Analog circuitry
does encourage simplicity, yes... by making design, testing, and maintenance of
even simple systems more difficult.  This is not necessarily a virtue.

                         Henry Spencer at U of Toronto Zoology utzoo!henry

Newsgroups: sci.aeronautics.airliners,misc.transport.air-industry
Date: 26 Dec 97 03:29:00
From: don@news.daedalus.co.nz (Don Stokes)
Subject: Re: Concorde's other customers

toad <y106fm@iamerica.net> wrote:
>Does Concorde have thrust reversers?  Or does it use a parachute to slow it
>down?

Short answer: thrust reversers.

Longer answer: Concorde actually has two sets of variable nozzles on each
engine.  The primary nozzle shapes the flow coming out of the engine, just
behind the reheats.  The second set operates as a pair of buckets.  Fully
open, they act as a kind of expansion chamber -- this is the setting while
operating supersonically.  Partly closed, they divert air from above and
below the engines into the core flow, reducing noise (relatively!), which
is used during subsonic operations.  Fully closed they act as thrust
reversers.

Concorde prototypes had drag parachutes for landing, but these were dropped
from the pre-production and production aircraft as being unnecessary.  (The
prototypes initially lacked the bucket style secondary nozzles.)

--
Don Stokes, Networking Consultant  http://www.daedalus.co.nz  +64 25 739 724
Network Design, Cable Plans, LANs, WANs, Radio Networks, Internet Consulting

Newsgroups: alt.sci.planetary
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Gravity???
Date: Mon, 12 Feb 1996 00:06:18 GMT

In article <4fk7t8$bdt@whidbey.whidbey.com> timelee@whidbey.net (Tim Huff, Sr.) writes:
>I am curious, if the Earth had half as much mass - but double the rotational 
>speed, what would be the effects??Does rotation have an effect on percieved 
>gravity on the surface of an object?

Yes, but only a small one for the rotational rates that are normally of
interest.  Careful measurement of Earth's gravitational attraction reveals
that it is a function of latitude, partly due to Earth's equatorial bulge
and partly due to the centrifugal force of rotation.  However, this effect
is insignificant for most practical purposes.  Doubling the rotation rate
would not change that. 

The only practical consequence I'm aware of from the centrifugal reduction
of gravity is that Concorde's fuel economy is slightly better eastbound,
where the aircraft's velocity adds to the rotational velocity and the
"centrifugal lift" reduces the wing loading slightly.  (For ordinary
airliners, as I recall, the effect is sufficiently smaller that it's
usually swamped by the differences in winds.)

For precise work, you have to pay attention to this sort of thing, though.
There are two different definitions of latitude, for example, and you have
to know which you're using when doing data reduction on astronomical
observations.  Geodetic latitude is the angle between a plumb-bob and the
Earth's equatorial plane, corrected for local irregularities in gravity,
e.g. the gravitational pull of mountains.  Geocentric latitude is the
angle between a line to Earth's center and the plane of the equator.  On
a spherical non-rotating planet they would be the same.  On Earth, they
aren't, except at the poles and the equator.

(Actually, there are three definitions of latitude:  the astronomical
latitude is the geodetic latitude without the corrections.  But that's
a detail.)
-- 
Space will not be opened by always                 |       Henry Spencer
leaving it to another generation.   --Bill Gaubatz |   henry@zoo.toronto.edu

Newsgroups: sci.aeronautics.airliners,alt.folklore.urban
From: ehahn@fairlite.mitre.org (Ed Hahn)
Subject: Re: How to become irradiated at 30 000 feet.
Date: 22 Apr 94 20:29:50

In article <airliners.1994.1161@ohare.Chicago.COM> kls@ohare.Chicago.COM
(Karl Swartz) writes:

   (Is there anything special
   about Concorde or its operation to address any radiation concerns?)

------
Well, it's not my usual source for postings to s.a.a, but Cecil
Adams of the Straight Dope column addressed this question in one of
his books, and concluded pretty much the same as you did.

He did mention that the Concorde had radiation detectors which advised
the pilot to descend if a certain radiation level was reached (50
millirems per hour ?).  Anyways, in the first several years of flight,
the detectors had yet to measure one tenth the alarm value.

Cecil Adams tends to shoot straight and research his answers about
technology fairly well, so I don't feel too anxious about posting
this...

ed