August 18, 1995 Advisory Circular AC 90-48C (Pilots' Role in Collision Avoidance) |
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The full text of the FAA bulletin.
August 18, 1995
 Advisory Circular AC 90-48C
Pilots' Role in Collision Avoidance
U.S. Department of Transportation
Federal Aviation Administration
3/18/83
Initiated by: AFO-820
1. PURPOSE.
This advisory circular is issued for the purpose of alerting all pilots to
the potential hazards of midair collision and near midair collision, a to
emphasize those basic problem areas related to the human causal factors where
improvements in pilot education, operating practices, procedures, and improved
scanning techniques are needed to reduce midair conflicts.
2. CANCELLATION.
AC 90-48B, Pilots' Role in Collision Avoidance, dated 9/5/80 is canceled.
3. BACKGROUND.
a. From 1978 through October 1982 a total of 152 midair collisions (MAC)
occurred in the United States resulting in 377 fatalities. Throughout this
approximate 5 year time period the yearly statistics remained fairly constant,
with a recorded high of 38 accidents in 1978 and a low of 25 in both 1980 and
1981. During this same time period there were 2,241 reported near midair
collisions (NMAC). Statistics indicate that the majority of these midair
collisions and near midair collisions, occurred in good weather and during the
hours of daylight.
b. The FAA has introduced several significant programs designed to reduce the
potential for midair and near midair collisions. This advisory circular is but
one of those programs and is directed towards all pilots operating in the
National Airspace System, with emphasis on the need for recognition of the human
factors associated with midair conflicts.
4. ACTION.
The following areas warrant special attention and continuing action on the
part of all pilots to avoid the possibility of becoming involved in a midair
conflict.
a. "See and Avoid" Concept.
(1) The flight rules prescribed in Part 91 of the Federal Aviation
Regulations (FAR) set forth the concept of "See and Avoid." This concept
requires that vigilance shall be maintained at all times, by each person
operating an aircraft, regardless of whether the operation is conducted under
Instrument Flight Rules (IFR) or Visual Flight Rules (VFR).
(2) Pilots should also keep in mind their responsibility for continuously
maintaining a vigilant lookout regardless of the type of aircraft being flown.
Remember that most MAC accidents and reported NMAC incidents occurred during
good VFR weather conditions and during the hours of daylight.
b. Visual Scanning.
(1) Pilots should remain constantly alert to all traffic movement within
their field of vision as well as periodically scanning the entire visual field
outside of their aircraft to ensure detection of conflicting traffic. Remember
that the performance capabilities of many aircraft, in both speed and rates of
climb / descent, result in high closure rates limiting the time available for
detection, decision, and evasive action. (See the "Distance/Speed/Time" chart
in Appendix 1.)
(2) The probability of spotting a potential collision threat increases with
the time spent looking outside, but certain techniques may be used to increase
the effectiveness of the scan time. The human eyes tend to focus somewhere, even
in a featureless sky. In order to be most effective, the pilot should shift
glances and refocus at intervals. Most pilots do this in the process of scanning
the instrument panel, but it is also important to focus outside to set up the
visual system for effective target acquisition.
(3) Pilots should also realize that their eyes may require several seconds to
refocus when switching views between items in the cockpit and distant objects.
Proper scanning requires the constant sharing of attention with other piloting
tasks, thus it is easily degraded by such psychophysiological conditions such as
fatigue, boredom, illness, anxiety, or preoccupation.
(4) Effective scanning is accomplished with a series of short, regularly
spaced eye movements that bring successive areas of the sky into the central
visual field. Each movement should not exceed 10 degrees, and each area should
be observed for at least 1 second to enable detection. Although horizontal back
and forth eye movements seem preferred by most pilots, each pilot should develop
a scanning pattern that is most comfortable and then adhere to it to assure
optimum scanning.
(5) Peripheral vision can be most useful in spotting collision threats from
other aircraft. Each time a scan is stopped and the eyes are refocused, the
peripheral vision takes on more importance because it is through this element
that movement is detected. Apparent movement is almost always the first
perception of a collision threat and probably the most important, because it is
the discovery of a threat that triggers the events leading to proper evasive
action. It is essential to remember, however, that if another aircraft appears
to have no relative motion, it is likely to be on a collision course with you.
If the other aircraft shows no lateral or vertical motion, but is increasing in
size, take immediate evasive action.
(6) Visual search at night depends almost entirely an peripheral vision. In
order to perceive a very dim lighted object in a certain direction, the pilot
should not look directly at the object, but scan the area adjacent to it. Short
stops, of a few seconds, in each scan will help to detect the light and its
movement.
(7) Lack of brightness and color contrast in daytime and conflicting ground
lights at night increase the difficulty of detecting other aircraft.
(8) Pilots are reminded of the requirement to move one's head in order to
search around the physical obstructions, such as door and window posts. The
doorpost can cover a considerable amount of sky, but a small head movement may
uncover an area which might be concealing a threat.
c. Clearing Procedures.
(1) Pilots should:
(i) Prior to taxiing onto a runway or landing area for takeoff, scan the
approach areas for possible landing traffic by maneuvering the aircraft to
provide a clear view of such areas. It is important that this be accomplished
even though a taxi or takeoff clearance has been received.
(ii) During climbs and descents in flight conditions which permit visual
detection of other traffic, execute gentle banks left and right at a frequency
which permits continuous visual scanning of the airspace about them.
(iii) Execute appropriate clearing procedures before all turns, abnormal
maneuvers, or acrobatics.
d. Airspace, Flight Rules, and Operational Environment.
(1) Pilots should be aware of the type of airspace in which they intend to
operate in order to comply with the flight rules applicable to that airspace.
Aeronautical information concerning the National Airspace System is disseminated
by three methods: aeronautical charts (primary); the Airman's Information Manual
(AIM); and the Notices to Airmen (NOTAM) system. The general operating and
flight rules governing the operation of aircraft within the United States are
contained in Part 91 of the FAR.
(2) Pilots should:
(i) Use currently effective aeronautical charts for the route or area in
which they intend to operate.
(ii) Note and understand the aeronautical legend and chart symbols related to
airspace information depicted on aeronautical charts.
(iii) Develop a working knowledge of the various airspace segments, including
the vertical and horizontal boundaries.
(iv) Develop a working knowledge of the specific flight rules (FAR 91)
governing operation of aircraft within the various airspace segments.
(v) Use the AIM. The Basic Flight Information and ATC Procedures describe the
airspace segments and the basic pilot responsibilities for operating in such
airspace.
(vi) Contact the nearest FAA Flight Service Station for any pertinent NOTAMs
pertaining to their area of operation.
(3) Pilots should also be familiar with, and exercise caution, in those
operational environments where they may expect to find a high volume of traffic
or special types of aircraft operation. These areas include Terminal Radar
Service Areas (TRSAs), airport traffic patterns, particularly at airports
without a control tower; airport traffic areas (below 3,000 feet above the
surface within five statute miles of an airport with an operating control
tower); terminal control areas; control zones, including any extensions; Federal
airways; vicinity of VORs; restricted areas; warning areas; alert areas;
Military Operating Areas (MOA); intensive student jet training areas; military
low level high speed training routes; instrument approach areas; and areas of
high density jet arrival / departure routings, especially in the vicinity of
major terminals and military bases.
e. Use of Communications Equipment and Air Traffic Advisory Services.
(1) One of the major factors contributing to the likelihood of NMAC incidents
in terminal areas that have an operating air traffic control (ATC) system has
been the mix of known arriving and departing aircraft with unknown traffic. The
known aircraft are generally in radio contact with the controlling facility
(local, approach, or departure control) and the other aircraft are neither in
two-way radio contact nor identified by ATC at the time of the NMAC. This
precludes ATC from issuing traffic advisory information to either aircraft.
(2) Although pilots should adhere to the necessary communications
requirements when operating VFR, they are also urged to take advantage of the
air traffic advisory services available to VFR aircraft.
(3) Pilots should:
(i) Use the AIM.
(A) The basic AIM contains a section dealing with services available to
pilots, including information on VFR advisory services, radar traffic
information services for VFR pilots, and recommended traffic advisory practices
at nontower airports.
(B) The airport / facility directory contains a list of all major airports
showing the services available to pilots and the applicable communication
frequencies.
(ii) Develop a working knowledge of those facilities providing traffic
advisory services and the area in which they give these services.
(iii) Initiate radio contact with the appropriate terminal radar or nonradar
facility when operating within the perimeters of the advertised service areas or
within 15 miles of the facility when no service area is specified.
(iv) When it is not practical to initiate radio contact for traffic
information, at least monitor the appropriate facility communication frequency,
particularly when operating in or through arrival / departure routes and
instrument approach areas.
(v) Remember that controller observation of aircraft in the terminal area is
often limited by distance, depth perception, aircraft conspicuity, and other
normal visual acuity problems. Limitations of radar (when available), traffic
volume, controller workload, unknown traffic, etc., may prevent the controller
from providing timely traffic advisory information. Traffic advisories are
secondary to the controllers' primary duties (which are separating aircraft
under their control and issuing safety advisories when aware of safety
conflicts). Therefore, the pilot is responsible for seeing and avoiding other
traffic. Traffic advisories should be requested and used when available to
assist the pilot to see and avoid other traffic by assisting, but not
substituting in any way, the pilot's own visual scanning. It is important to
remember that advisories which air traffic control may provide are not intended
to lessen in any manner the pilot's obligation to properly scan to see and avoid
traffic.
f. Airport Traffic Patterns.
(1) A significant number of midair collisions, as well as near midair
collisions, have occurred within the traffic pattern environment.
(2) Pilots should:
(i) When operating at tower controlled airports, maintain two-way radio
contact with the tower while within the airport traffic area. Make every effort
to see and properly avoid any aircraft pointed out by the tower, or any other
aircraft which may be in the area and unknown to the tower.
(ii) When entering a known traffic pattern at a nontower airport, keep a
sharp lookout for other aircraft in the pattern. Enter the pattern in level
flight and allow plenty of spacing to avoid overtaking or cutting any aircraft
out of the pattern.
(iii) When approaching an unfamiliar airport fly over or circle the airport
at least 500 feet above traffic pattern altitude (usually at 2,000 feet or more
above the surface) to observe the airport layout, any local traffic in the area,
and the wind and traffic direction indicators. Never descend into the traffic
pattern from directly above the airport.
(iv) Be particularly alert before turning to the base leg, final approach
course, and during the final approach to landing. At nontower airports, avoid
entering the traffic pattern on the base leg or from a straight-in approach to
the landing runway.
(v) Compensate for blind spots due to aircraft design and flight attitude by
moving your head or maneuvering the aircraft.
g. Flying In Formation.
(1) Several midair collisions have occurred which involved aircraft on the
same mission, with each pilot aware of the other's presence.
(2) Pilots who are required, by the nature of their operations, to fly in
pairs or in formation are cautioned to:
(i) Recognize the high statistical probability of their involvement in midair
collisions.
(ii) Make sure that adequate preflight preparations are made and the
procedures to be followed are understood by all pilots intending to participate
in the mission.
(iii) Always keep the other aircraft in sight despite possible distraction
and preoccupation with other mission requirements.
(iv) Avoid attempting formation flight without having obtained instruction
and attained the skill necessary for conducting such operations.
h. Flight Instructors, Pilot Examiners, and Persons Acting As Safety Pilots.
(1) The importance of flight instructors training pilot applicants to devote
maximum attention to collision avoidance while conducting flight operations in
today's increasing air traffic environment cannot be overemphasized.
(2) Flight instructors should set an example by carefully observing all
regulations and recognized safety practices, since students consciously and
unconsciously imitate the flying habits of their instructors.
(3) Flight instructors and persons acting as safety pilots should:
(i) Guard against preoccupation during flight instruction to the exclusion of
maintaining a constant vigilance for other traffic.
(ii) Be particularly alert during the conduct of simulated instrument flight
where there is a tendency to "look inside."
(iii) Place special training emphasis on those basic problem areas of concern
mentioned in this advisory circular where improvements in pilot education,
operating practices, procedures, and techniques are needed to reduce midair
conflicts.
(iv) Notify the control tower operator, at airports where a tower is manned,
regarding student first solo flights.
(v) Explain the availability of and encourage the use of expanded radar
services for arriving and departing aircraft at terminal airports where this
service is available, as well as, the use of radar traffic advisory services for
transiting terminal areas or flying between enroute points.
(vi) Understand and explain the limitations of radar that may frequently
limit or prevent the issuance of radar advisories by air traffic controllers
(refer to AIM).
(4) Pilot examiners should:
(i) During any flight test, direct attention to the applicant's vigilance of
other air traffic and an adequate clearance of the area before performing any
flight maneuver.
(ii) Direct attention to the applicant's knowledge of the airspace, available
FAA air traffic services and facilities, essential rules, good operating
practices, procedures, and techniques that are necessary to achieve high
standards of air safety.
i. Scan Training. The Aircraft Owners and Pilots Association (AOPA) Air
Safety Foundation has developed an excellent educational program designed to
inform pilots on effective visual scan techniques. All pilots are encouraged to
attend FAA / industry sponsored safety meetings which feature this program. The
program, called "Take Two and See," is available on loan through the AOPA Air
Safety Foundation, 7315 Wisconsin Avenue, Bethesda, Maryland 20814. For further
information on the availability of this or any other Accident Prevention Program
dealing with collision avoidance, interested persons may contact the Accident
Prevention Specialist at any FAA General Aviation District Office or Flight
Standards District Office.
/s/
KENNETH S. HUNT
Director of Flight Operations
Appendix 1
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