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Re: Analysis from a JHU CS Prof
From: Owen DeLong <owen () delong sj ca us>
Date: Tue, 11 Sep 2001 22:04:56 -0700


Apologies to the list, this is way off topic, and if you're looking for
operational content, just hit delete now.  However, the number of people
posting bad specualtion about aviation is bothering me and I feel
compelled
to reply.

I hold a Private Pilot rating for Airplane Single Engine Land.  I also
hold
an Instrument Airplane rating.  I have about 800 hours of total flight
time,
including various single engine a small amount of multi-engine, some
glider,
some free balloon time. I have spent some time in the cockpit of an
Airbus A-319 in flight, including an approach into San Jose
International.
I was in the jumpseat, but I received substantial education from the
pilots
while I was there.  If anyone feels that my answers are not adequate,
please let me know off-list and I'll get you an answer from an ATP I
know
who is rated in the 757 and 767 types.

John Fraizer wrote:

On Wed, 12 Sep 2001, David Howe wrote:


Also, it's worth remembering that airplanes aren't all that easy to
fly. This means that the perpetrators needed to find five adequate
pilots,
Hmm. not actually sure about this - not having ever flown anything at
all, but how much skill exactly does it take to keep something already
pointed in more or less the right direction on target for two-three
minutes until impact? ok, you couldn't expect a clean landing or even a

It takes quite a bit more than you would expect.  Something that you
neglect to remember is that the plane that struck the Pentagon was
initially headed directly towards the Whitehouse, then executed a
high-speed, high-bank turn around DC, lined up on the Pentagon and managed
to nose into it at mid-level.

It is VERY difficult to control an aircraft in a high-speed nose-down
attitude.  ESPECIALLY those that are less than "sporty" in flight
characteristics.

It is not difficult to control these types of aircraft in a 200-300
knott
(knautical mile per hour, about 1.1 statute miles per hour) nose-down
attitude.  It can be done on autopilot in most cases.  

As I understand the reports, the plane that struck the Pentagon was on
the
standard noise-abatement approach path into National along the Potomac,
and made a ~30 degree bank turn nose down into the side of the
pentagon.  This may have required overriding the autopilot for the
final portion of the descent, but otherwise, the entire process could
have been conducted using a small subset of the autopilot capabilities
that could easily be figured out by a student pilot.  If you're not
worried about keeping your airspeed under control (not going too fast),
it's relatively easy to point a plane at the ground and keep it going
that way.

halfway-smooth flight path from someone who has played a MS-Windows
flight sim for a few months, but - if he was going from switching off
autopilot to keeping the plane pointed at something the size of the
WTC....... I would imagine it would all be on the yoke too, no throttles
or concerns about airspeed given you are not really going to care that
much what speed or acceleration you have on impact...

Again.  Think about it.  The WTC is not actually that large of a
target.  Granted, it's was easy to pick out from the air but, lining up on
it and maintaining a flight attitude that will keep you in the air until
impact is a different story.  If you've seen footage of the second plane
impacting, look at the last second attitude correction.  Had the
individual who was flying the aircraft not made that correction, it would
not have struck the building. (At least THAT building.)  Also, airspeed is
very important if you want to keep an aircraft aloft.  ESPECIALLY when you
are pulling turns.  If you're just above stall and try to turn the
aircraft, you don't turn -- you fall.

The WTC is a huge traget that is visible from a very long distance away
under
the weather conditions that existed.  The second plane made a very small
correction a few seconds before impact.  Nothing I saw in the footage
leads
me to believe that the airplane was not operating on autopilot in
altitude
hold mode.  The correction could have been accomplished by a small twist
of
the heading select knob.  The world trade center impacts occured at a
high
enough altitude that it is not unlikely that the autopilot would not
have
overriden the altitude selection for terrain.

... or train for the two/three more common types, then pick a flight *on
the day* that actually is flying that type of plane. book seats at the
last minute (not a problem for domestic flights) or pre-book three or
four different seats per attacker, and each picks a flight with the
right sort of plane from the "pool" of available flights.

There are mechanisms in place that would detect this type of
behavior.  (Prebooking multiple flights for the same individual.)

I agree that this would be more difficult.  All that was really
required,
though, was some time in one of the popular simulator programs and a
little
bit of knowledge about any flight management system and some
understanding
of Altitude, Heading, Waypoints, and general autopilot operations.  All
of this could probably be obtained in a relatively small amount of
training
time with any flight instructor at your local FBO.  Most of it could
probably
be learned on a PC with readily available software.  The autopilot
operation
of the large jets in Fly!2 and Micro$oft FS2000 is realistic enough to
probably provide adequate autopilot training.

This having been said, I don't put it past the various organizations to
have trained type rated pilots for this purpose.


Owen

---
John Fraizer
EnterZone, Inc

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