Thwarting skyjackings
from the ground
By Alan
Staats
Posted to FACSNET
Oct. 2, 2001
Published in Quill magazine {February
1998}
Automated airplane landing systems are advanced enough to bring
a hijacked airplane 'home'
I. Introduction
II. How the system works
III. The bottom line
IV. History on remote control
V. Progress in technology
VI. A highly evolved autopilot
VII. Sources
Glossary of aviation
terms
Technology now exists that could allow a ground
crew to override and direct the flight path of a hijacked plane.
Following the Sept. 11 attacks on the Pentagon and World Trade
Center, President George W. Bush called for the creation of a system
that would allow Air Traffic Controllers on the ground the ability
to assume remote control of the aircraft and direct it to a safe
landing at a nearby airport.
The military has employed this capability since the 1950s. Modifying
and implementing the technology for use on passenger carrying aircraft
in the United States would involve significant capital outlay, research
and testing. But from an engineering standpoint, landing an aircraft
automatically is a relatively simple matter.
ìAutolandî systems have been in wide commercial use in different
parts of the world since the 1980s. Auto landings are routinely
performed thousands of times a day throughout the world.
How the system works
Landing categories are broken down by minimum cloud heights, also
known as the ìceiling," and the amount of horizontal visibility.
There are three different categories of landing systems:
1. The "CAT IIIa" approach is flown by an aircraft equipped
with three separate autopilot systems (one for actually commanding
the aircraft, and two for backup) to a decision altitude of 50 feet,
with at least 700 feet of horizontal visibility (referred to as
RVR, or Runway Visual Range).Ý With this system, the crew must have
visual confirmation that the runway is in sight, and that the aircraft
is on course to land upon it, whereupon the autopilot system is
disconnected and the pilot flies the aircraft to a safe touchdown.
2. CAT IIIb is a true autoland category, that is, the approach
and landing touchdown are controlled entirely by what is known as
a Flight Management System, or FMS. The crew must see the runway
at an alert altitude of 50 feet with an RVR of 600 feet and verify
that all three autopilots are on line and functioning correctly,
and that the aircraft is configured to land, at which point the
decision is made to allow the system to land the aircraft.
3. A CAT IIIc autoland approach has a higher alert height, 100
feet, then a IIIb landing, but a shorter RVR of 300 feet. Again,
a final decision is made at the alert height to either continue
the landing or abort.
In all three categories of approach, the Flight Management System
is entirely capable of landing the aircraft and, in some CAT IIIc-equipped
aircraft such as the Boeing 747-400, capable of applying the brakes
after touchdown and stopping the aircraft as well.
As for equipping an airliner for such use, the primary drawbacks
are the mechanical systems, the flaps and landing gear, whose actuators
are usually mechanical levers and/or switches in the cockpit. Retrofitting
aircraft to allow for remote activation of these flight critical
devices is possible, but would be very expensive.
The bottom line
It is technically possible to create a system to perform remotely
commanded return flights of a hijacked airliner. Onboard digital
command, control and display equipment can easily share data with,
and accept commands from, ground control stations. Little input
beyond the initial command to enter safe return flight and the ultimate
destination are needed.
Costs of retrofitting the existing airline fleet?Ý Estimates range
from $10 billion to more than $300 billion spent over a period of
ten years.
The most pragmatic approach? Design and install such systems into
aircraft currently under development, and, on current production
aircraft, design and install electronic interfaces and overrides.
History on remote control
Controlling the aircraft from the ground is nothing new. The military
has been flying obsolete high performance fighter aircraft as target
drones since the 1950s. In fact, NORAD (the North American Air Defense
Command) had at its disposal a number of U.S. Air Force General
Dynamics F-106 Delta Dart fighter aircraft configured to be remotely
flown into combat as early as 1959 under the auspices of a program
know as SAGE. These aircraft could be started, taxied, taken off,
flown into combat, fight, and return to a landing entirely by remote
control, with the only human intervention needed being to fuel and
re-arm them.
To this day, drone aircraft are remotely flown from Air Force and
Naval bases all over the country to provide targets for both airborne
and ground based weapons platforms.Ý
The data links, which could be used for remotely controlling digital
airborne flight control systems in commercial aircraft, are already
in wide use. Known as ACARS (Aircraft Communications Addressing
and Reporting System) this system is widely used to report everything
from position and fuel burn, weather and flight plan information
to ground stations. ACARS also has the capability of sending data
to the aircraft, as well.
Using this bi-directional data link would allow both uploading
digital control inputs to control the aircraft as well as the potential
to download and remotely monitor the digital aircraft displays.
Progress in Technology
In the past 20 years, progress in the field of avionics (AVIation
electrONICS) has given end users the ability to safely navigate
and communicate to, and from, virtually any point on, or for that
matter above, the earth.
The most significant development is the fielding and proliferation
of a satellite based navigation infrastructure, or Global Positioning
System (GPS) originally intended for use by the U.S. military. GPS
utilizes a ìconstellationî of satellites -- 24 of which are in active
use with three launched as spares, to provide incredibly accurate
position information to end users.
Paralleling the widening acceptance of both the burgeoning GPS
industry as well as the exponential increases in computer processing
capabilities were two major developments in airborne navigation
and display.Ý
Cathode ray tube (CRT) displays, collectively known as Electronic
Flight Information Systems (EFIS), were first fielded for civilian
use in 1985.Ý EFIS displays are essentially airborne computer monitors
with the ability to ìcompositeî information from a number of sources
into a single display, something that cannot be done with traditional
electro-mechanical instruments.
In essence, EFIS allows the crew to distill available information
down to what a pilot needs to know at a particular time.
The downside of these displays is their expense:Ý An eight by ten
inch CRT tube used in a Boeing 747 class aircraft costs approximately
$234,076, according to the 2002 Rockwell Collins price list. A 747
has six of these displays installed.
A 'highly evolved autopilot'
As ìglass cockpits," as EFIS instrument panels are referred
to, gained acceptance, engineers concurrently designed flight management
system (FMS) hardware and software that utilized faster and faster
onboard computers to manage more and more onboard tasks.Ý
FMS hardware is essentially a highly evolved autopilot, for all
intents and purposes.Ý However, where the autopilot was, in earlier
times, a self-contained system, in todayís modern cockpits the autopilot
is a sub-system that interpolates and executes commands generated
by the FMS automatically or by the pilot, manually.
In every day airline use, a flight plan is loaded into an FMS via
either keystrokes on an alphanumeric pad, or via disc. This flight
plan, pre-approved by, and filed with, the FAA will contain course,
altitude and speed data which the aircraft will maintain at all
points of its flight.Ý
The format of the flight plan can be thought of as ìpoint in spaceî
data. In other words, the pilot flies the aircraft off of a runway
and initially aims at a point in space that is a certain distance
from, and at a certain altitude above the end of the runway he departed
from. Upon reaching that point in space, which in most cases is
an ìintersection,î a point at which two major aircraft routes known
as ìairwaysî meet, the FMS will execute a turn, a climb, or combination
of the two to the next point in space, and so on as the flight plan
progresses.
Autopilots, once a system into and of themselves in airline aircraft,
have evolved as well.Ý
Originally designed and built in large numbers during World War
II, the autopilot has come a long was since the first commercially
available unit, the Sperry H-2, a comparatively crude pneumatic
mechanical and vacuum tube device that would hold a course and keep
the wings level, more or less.Ý
These days, a digital autopilot, in conjunction with systems that
control the throttles, can effectively fly the aircraft from point
to point with little or no input (beyond systems monitoring) from
the crew.
Because all the components of controlling the aircraft communicate
with each other digitally through a central unit, the FMS, activating
such a ìsafe returnî system would be a matter of uploading commands
to the FMS to fly the aircraft to the nearest airport.Ý Controlling
the aircraftís speed, altitude and course, the FMS would guide it
back to land.
Sources:
-
Richard Vandam
US Airways A320 Captain; Former Captain, U.S. Air Force, RF4-C
pilot, Reno National Championship Air Races Air Boss and Chase
Plane pilot, check and instructor pilot for vintage Cold War
era Eastern Bloc fighter aircraft (MiG-15, -17, -21)
Reno, Nevada. 775-742-5640 (cell), 775-851-1930 (home), e-mail
rvandam162@aol.com
-
Aircraft Electronics Association http://www.aea.net
Contact: Paula Derks, 4217 S. Hocker, Independence, MO 64055
Phone: 816-373-6565
Fax: 816-478-3100Ý email: paulad@aea.net
-
National Business Aircraft Association
Main contacts:Ý Joseph Ponte, Jack Olcott
1200 Eighteenth Street NW, Suite 400, Washington, DC 20036-2506
Tel: (202) 783-9000Ý Fax: (202) 331-8364
Web: http://www.nbaa.org
-
FlightSafety International-Corporate Headquarters
Contact:Ý James Waugh
Marine Air Terminal, LaGuardia Airport, Flushing, NY 11371-1061
(718) 565-4100,Ý (800) 877-5343 Fax: (718) 565-4174
Questions@FlightSafety.com
-
Airline Pilots Association
Contact: Gary Dinunno
http://www.alpa.org
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