t 3 c/ 

U.S. Department 

of Transportation 

Federal Aviation 

Administration 

Y 

ircular 

Subject: 

PI=' WLE IN COLLJSICXJ AVOIDANCE 

Date: 3/18/83 AC No: 90048C 

Initiated by: AFO- 820 Change: 

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, 

'm 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 tL) reduce midair conflicts. 

2 CANCELLA'ITON. 

is canceled. 

AC 90048B, Pilots' Role in Collision Avoidance, dated g/5/80 

3 o 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 l 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 mllisions, occurred in m weather and during the 

hours of daylight. 

b The FAA has introduced several significant programs designed to reduce 

the p&ential for midair and near midair collisions. This advisory circular is 

but one of those programs and is directed tiwards all pilots operating in the 

National Airspace System, with emphasis on the need for recognition of the humtin 

factors associated with midair conflicts. 

4 ACTION. The following areas warrant special attention and continuing action 

0; mt of all pilots to avoid the possibility of becoming involved iI-1 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 *ether the operation is conducted under 

Instrument Flight Rules (IFR) or Visual Flight Rules (VFR). 

(2) Pilots should also keep in mind their responsibility for mntinuously 

maintaining a vigilant lookout regardless of the tm 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. 
AC 90048C 3/H/83 

b e Visual Scanninq. 

(1) Pilots should remain anstantly alert to all traffic movement within 

their field of visio& as well as periodically scanning the entire visual field 

outside of their aircraft ti 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 tQ increase the 

effectiveness of the scan time. The human eyes ted ti focus mmewhere, even in a 

featureless sky. In order ti be mst effective, the pilot should shift glances arCi 

refocus at intervals. Most pilots do this in the process of scanning the 

instrument panel, but it is also important tr, 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 vsiews between items in the cx>ckpit 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 nx>vements that bring successive areas of the sky into the 

central visual field. Each nr>vement 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 rrr>st mfortable ti then adhere to it ti assure 

optimum scanning. 

(5) Peripheral vision can be mst useful in spotting collision threats from 

other aircraft. Each time a scan is stopped and the eyes are refocused, the 

peripheral vision takes on m3re importance because it is through this element that 

movement is detected. Apparent rrovement is almost always the first prception of a 

collision threat and probably the nr>st important, because it is the discovery of a 

threat that triggers the events leading to proper evasive action. It is essential 

to remember, h&ever, that if another aircraft appears ti have no relative motion, 

it is likely ti be on a allision aurse 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 on 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 mntrast in daytime anc3 cronflicting 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 

Par 4 
3/18/83 AC 90-48C 

search around the physical obstructions, such as door and window posts. The 

doorpost can aver a ansiderable amount of skyr but a small head movement may 

uncover an area tdklich might be concealing a threat. 

C, Clearing Procedures. 

(1) Pilots should: 

( i 1 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 imporrtant 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 tiich permits continuous visual scanning of the airspace about them. 

(iii) Execute appropriate clearing procedures before all turns, 

abnormal maneuvers, or acrobatics. 

d e 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% Information Manual 

(AIM); and the Notices to Airmen (NCYTAM) 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 tiich they intend tr> operate. 

(ii) Note zud understand the aeronautical legend and chart symbols 

related to airspace information depicted on aeronautical &arts. 

(iii) Develop a mrking knowledge of the various airspace segments, 

including the vertical and horizontal boundaries. 

(iv) Develop a tkiq 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 b their area of operation. 

Par 4 
3118183 AC 90-48C 

(3) Pilots should also be familiar with, and exercise caution, in those 

operational environments tiere they may expect ti find a high volume of traffic or 

special types of aircraft operation. These areas include Terminal Radar Service 

Areas (TRSA's), 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 tr>wer); terminal control 

areas; control zones, including any extensions; Federal airways; vicinity of VORk; 

restricted areas; warning areas; alert areas; Military Operating Areas (MOA); 

intensive student jet training areas; military low-level high-speed training 

routes; instrument af?proach areas; and areas of high density jet arrival/departure 

routings, especially in the vicinity of major terminals and military bases. 

e. Use of Communications Equipnt and Air Traffic Advisory Services. 

(1) One of the major factors contributing to the likelihood of NMAC 

incidents in terminal areas t!-at have an operating air traffic control (AX) system 

has been the mix of known arriving and departing aircraft with unknown traffic. 

The known aircraft z!i?nerally 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 *en operating VFR, they are also urged to take advantage of the air 

traffic advisory services available ti 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 Factices at 

nontower airports. 

(B) The airport/facility directory contains a list of all major 

airports showing the services available to pilots and the applicable munication 

frequencies. 

(ii) Develop a mrking 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 *en no service area is specified. 

(iv) When it is not practical ti initiate radio contact for traffic 

information, at least monitor the appropriate facility communication frequency, 

particularly &en operating in or through arrival/departure routes and instrument 

approach areas. 

Par 4 
3118183 AC 90-48C 

( v 1 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 hen 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 rember that advisories tiich 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 0 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 1 When operating at tower-controlled airports, maintain two-way 

radio contact with the tower tiile within the airport traffic area. Make every 

effort to see and properly avoid any aircraft pointed out by the tower, or any 

other aircraft ta?ich may be in the area and unknown to the tiwer. 

(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 tive 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 murse, and during the final approach to landing. At nontower airports, 

avoid entering the traffic pattern on the base leg or fram a straight-in approach 

to the landing runway. 

( V 1 Compensate 

attitude by moving your head 

g 0 Flying In Formation, 

for blind spots due to aircraft design and flight 

or maneuvering the aircraft, 

(1) Several midair collisions have occurred which involved aircraft on the 

same mission, with each pilot aware of the other's presence. 

(2) Pilots tie are required, by the nature of their operations, to fly in 

pairs or in formation are cautioned to: 

Par 4 
AC 90-48C 3118183 

( i 1 Recognize the high statistical probability of their involvement 

in midair mllisions. 

(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 aperations. 

h a Flight Instructors, Pilot Examiners, and Persons Acting As Safety Pilots. 

(1) The importance of flight instructors training pilot applicants ti devote 

maximum attention tr> collision avoidance while conducting flight operations in 

today% 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 pearsons acting as safety pilots should: 

( 1 i Guard against preoccupation during flight instruction to the 

exclusion of maintaining a mnstant vigilance for other traffic. 

(ii) ESe particularly alert during the conduct of simulated instrument 

flight tiere there is a tendency to "look inside," 

(iii) Place special training emphasis on those basic problem areas of 

concern mentioned in this advisory circular tiere improvements in pilot education, 

operating practices, 

conflicts. 

procedures1 and techniques are needed to reduce midair 

(iv) Notify the mntrol tiwer operator, at airports where a tower is . 

manned, regarding student first solo flights. 

( V 1 Explain the availability of and encourage the use of expanded 

. radar services for arriving and departing aircraft at terminal airports where this 

. . service 1s available, as well as, the use of radar traffic advisory services for 

transiting terminal areas or flying between en-route 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: 

( 1 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. 

6 Par 4 
3118183 AC 90-48c 

(ii) Direct attention tr> the applicant% knowledge of the airspace, 

available FAA air traffic senrices 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 tro inform 

pilots on effective visual scan techniques. All pilots are encouraged to attend 

FAA/industry sponsored safety meetings tiich 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. 

Director of Flight Operations 

Par 4 

3/M/83 AC 90-48c 

Appendix 1 

DISTAM 

MP 

IO mile8 

6 miles 

5 miles 

4 miles 

60 100 

36 60 

24 

LOOK ALIVE P*O LIVE 

CRITICAL SECONDS 

Move back 12 feet from this illustration. From 

that oosition the silhouettes represent a T-33 

aircraft as it would appear to you from the distances indicated in the table on the left. The 

time required to cover these distances is given 

in seconds for combined speeds of 360 and 600 mph. 

The blocks on the lower left mark the danger area. 

for the speeds quoted, when aircraft are on a 

collision course. This danger area is based on 

the recognition and reaction times shown in the 

table on the lower right. 

RCCOCWTIo)r 

d ss== 

t9’ Seconds 

Page l(and 2)