00100	COMPUTER CONTROLLED AIRPLANES
00200	by John McCarthy, Computer Science Department, Stanford University
00300	
00350	1. Introduction
00400		Computers are already used in a number of military
00500	airplanes and are projected for the supersonic
00600	transport.  This article is concerned with the use
00700	of computers in present planes even including light
00800	planes.  We envisage a small real time computer
00900	no larger than a PDP-8I carrying out tasks in the
01000	areas of navigation, collision avoidance and responding
01100	to traffic control, monitoring the condition of the
01200	airplane, optimizing flight path taking into account
01300	fuel, load, weather, and traffic.
01400	
01500	2. Navigation
01600		We advocate no basically new electronic navigation
01700	systems.  The basic system we consider is the familiar
01800	omnirange.  However, the computer will switch its radios
01900	at .1 second intervals among all available omnis and will
02000	compute each few seconds a best estimate of the current
02100	position of the aircraft.  This estimate will be displayed
02200	for the pilot on a map on a CRT and will be available for
02300	interrogation from the ground or other airplanes.  More
02400	accurate positions should be available than at present
02500	because any systematic inaccuracies in the radials of an
02600	omni due to terrain can be allowed for by the computer;
02700	a correction equation for the omni will be stored
02800	along with its position in the computer equivalent of the
02900	sectional chart.  Our goal is that  navigation be accurate
03000	enough so that aircraft can be flown close enough together
03100	so that there will be enough airspace for everybody
03200	without danger of collision.
03300	
03400		All instruments now available to the crew
03500	will be read by the computer at appropriate intervals,
03600	e.g. every .1 to 10 seconds depending on the instrument.
03700	In navigation, altitude, airspeed, and heading information
03800	will be integrated with the information obtained from 
03900	the omnis.  The amount of information available is much
04000	greater than is required to monitor position, and
04100	any inconsistencies will be detected and the offending
04200	instrument reported to the crew.
04300	
04400	3. Collision avoidance and traffic control
04500		Here again we want a system with large redundancy.
04600	The basisc scheme is that the air traffic
04700	control computer interrogates each airplane every few 
04800	seconds and gets its position information or perhaps even
04900	the raw bearing information received from the omnis.  Since
05000	the interrogation is electronic, a single 25kc band could
05100	interrogate 100 airplanes per second at 250 bits per
05200	interrogation.  Each airplane can be  given relevant
05300	traffic information or specific collision avoidance
05400	instructions if this is desired.
05500	
05600		In addition to the standard information transmitted
05700	to the airplanes, special messages addressed to the
05800	crew of an airplane can be presented on the CRT
05900	or printed on a strip printer.
06000	
06100		Additional redundancy can be obtained by 
06200	timing signals returned from a plane or even signals
06300	transmitted from the ground to a plane, then to another
06400	plane and then to another ground receiver.
06500	
06600	4. Monitoring
06700		The crew of an airplane is supposed to monitor
06800	all the instruments at regular intervals.  However, this
06900	activity can be done much more reliably by a computer.
07000	Moreover, the computer can relate such information as
07100	airspeed, attitude, engine RPM, fuel flow, and air pressure
07200	and temperature and check continuously for fall
07300	off of engine performance or ice buildup.  Other parameters
07400	that can be monitored include  electrical system performance
07500	including availability of emergency power, correct
07600	functioning of navigation and other lights, icing conditions,
07700	navigation checkpoints,  maintenance of communication,
07800	and all engine instruments.
07900	
08000	5. Visual monitoring
08100		With the aid of television cameras, a computer can be
08200	programmed to use visual information.  The 
08300	possibilities include finding airports and runways
08400	under visual conditions, landing, taking off, and taxiing,
08500	terrain avoidance, and collision avoidance.
08600	In short, the computer can potentially perform
08700	the full range of chores of the VFR pilot.  All this,
08800	however, places much larger demands on the computer and
08900	the programming than the previous applications
09000	and is therefore somewhat further in the future.