Dale R. Reed (
Wed, 20 Nov 1996 07:20:35 -0800

Greetings all. It has stopped snowing in Seattle and as usual it will
start raining and be very messy for a few hours. I liked the snow but I
could walk everywhere I wanted to go.

These educational discussions reminds me of my efforts to try to explain
my concerns to other members of many different Design Build Teams(DBT)
working to create the 777 airplane. I was responsible(5 years ago) for
the engineering design of the protection of the future airplane against
the induced lightning and the High Intensity Radio Frequency (HIRF)

I had to convince the other engineers and managers that were responsible
for aerodynamics, weights, costs, reliability, passenger satisfaction,
safety, efficiency . . . that I was able to design the protection
required and convince them that if they did not move the systems or add
the extra shielding the passengers would suffer. I had to have
convincing mathematical models that yielded numbers that changed in
reasonable manners when engineering design trades were being done.

No problem with the technology for we had developed modeling techniques
from our previous protection of the Minuteman nuclear missiles buried in
Montana, Missouri, South Dakota and Wyoming from the Nuclear
ElectroMagnetic Pulse(NEMP) threat. I and a brilliant young engineer
had turned a sword into a plowshare and were eager to show our stuff on
the brand new commercial airplane.

So I was competent and confident but I still had to convince my fellow
engineers on the DBT. No problem with the lightning. Everyone had seen
lightning and heard thunder. They could imagine what a 200,000 Amp
lightning bolt might do to their delicate fly-by-wire systems and the
computer model was believable to all of those that had learned even a
little of the electrical engineering lingo in school. Besides a 747 had
been blown out of the air by a lightning strike, C-130's had suffered,
many of the engineers had seen the holes drilled in the aluminum skins
of airplanes by lightning direct attachments…..they believed in the
lightning threat and I had little trouble explaining the understandable

But HIRF protection was something else. Of course lots of military
airplanes and helicopters had been effected by large ElectroMagnetic(EM)
fields especially on the cramped quarters of aircraft carriers or sky
jockeys playing too close to Radio Free Europe transmitting towers but
there has been no bad experiences between commercial airplanes and EM
fields except for non dangerous low level interference with the
communication systems. So the other DBT members did not believe there
was a threat and in fact neither did I. But the FAA said we had to
protect the airplane so we did.

Now to the important point of my story.

The explaining of my HIRF concerns was made considerably more difficult
because the HIRF threat spread over a large frequency range from
VLF(Very Low Frequencies) to Microwaves and that required a variety of
modeling approaches. The lightning model was OK for middle frequencies
if I excited it with a simple plane wave from various directions and
various polarizations instead of the attached lightning source. But
this rather easy to understand model did not work for the lower
frequencies and the very high frequencies.

Hence when I stood up in front of 20 or more doubting engineers and
managers and did my dog and pony shows with viewfoils trying to convince
them to add weight, reduce reliability, add costs, make the 777 more
difficult to maintain…… I attempted to cause them to visualize in their
own minds the interaction of the fields and the airplane over a broad
frequency range. When I said something about the resulting currents in
the systems and what protection(systems placement or shielding) I was
recommending I had to make clear what frequency range I was talking
about. If what I said did not make sense to them then I would get a
thumbs down on my preferred solution and have to live with second(from
my EM point of view) best. Unfortunately for me that usually meant
weekend work to create an alternative protection scheme.

Our school discussions are like that. At least we are all motivated but
there is a good chance that we have different children in mind as we
discuss these different options. If we are a parent the children we are
visualizing are the ages and maturities of our own children. If we are
an educator it is the ones in our school or in our classes. We may be
thinking of a particularly difficult student or we may be considering an
ideal student. We will always have trouble communicating amongst
ourselves because at any time on any day during every posting each of us
in our own ways has a different child in mind and even though what we
are saying is true for that child it may not be for the children being
imagined by the others in the discussion group at that time.

Of course that are differences between us in religion, philosophy of
life, Visions as Thomas Sowell calls them . . . but that is not the
subject of this letter.

Just an idea. Hope it was interesting and meaningful to at least a few
of you. Dale