AC 90-48E - Pilots Role in Collision Avoidance

U.S. Department

of Transportation

Federal Aviation

Administration Advisory

Circular

Subject: Pilots ’ Role in Collision Avoidance Date: 10/20/22 AC No: 90-48E

Initiated by: AFS-800 Change:

1 PURPOSE OF THIS ADVISORY CIRCULAR (AC) . This AC is issued to assist

pilots with their regulatory obligation to see and avoid other aircraft. Specifically, this

AC looks to alert pilots to human contributors to midair collisions and near midair

collisions (NMAC), and recommend improvements to pilot education, operating

practices, procedures , and improved scanning techniques to reduce midair conflicts. This

AC is not mandatory and does not constitute a regulation. The contents of this document

do not have the force and effect of law and are not meant to bind the public in any way ,

and the document is intended only to provide clarity to the public regarding existing

requirements under the law or agency policies.

2 AUDIENCE. This AC is intended to provide guidance to c ertificated pilots, flight

instructors, student pilots, training provi ders, and pilot exami ners to mitigate the risk of a

midair collision or NMAC during flight operations .

3 WHERE YOU CAN FIND THIS AC. You can find this AC on the Federal Aviation

Administration ’s (FAA ) website at https://www.faa.gov/regulations_policies/advisory

_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov .

4 PRINCIPAL CHANGES. This revision to the AC incorporates additional information

regarding pilot actions, procedures, Notices to Air Missions (NOTAM) , and aircraft

technology to mitigate the risk of a pilot causing or being involved in a ground collision ,

in-flight collision , or NMAC.

5 WHAT THIS AC CANCELS . AC 90 -48D CHG 1 , Pilots ’ Role in Collision Avoidance,

dated June 28, 2016, is canceled.

6 REFERENCES AND RELATED READING MATERIALS (current editions) .

6.1 Regulations and Guidance.

• Title 14 of the Code of Federal Regulations (14 CFR) part 91 sections related to

preflight, right -of-way rules, o perating on or in the vicinity of an airport, operations in

classes of a irspace, basic and s pecial visual flight rules (VFR ) minimums, VFR and

instrument flight rules (IFR) cruising altitudes, powered civil aircraft standard

category and equipment requirements, and Automatic Dependent

Surveillance -Broadcast (ADS -B): §§ 91.103 , 91.113 , 91.126, 91.127 , 91.129, 91.130 ,

91.131, 91.135 , 91.155, 91.157 , 91.159, 91.179 , 91.205, 91.225 , and 91.227.

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2 • AC 90-66, Non -T owered Airport Flight Operations.

• AC 91-73, Parts 91 and 135 Single Pilot, Flight School Procedures During Taxi

Operations.

• AC 91-79, Mitigating the Risks of a Runway Overrun Upon Landing.

• Aeronautical Information Manual (AIM) :

• Chapter 4, Air Traffic Control (services available to pilots , communications,

and more) .

• Chapter 8, Section 1, Fitness for Flight, Paragraph 8 -1-6, Vision in Flight.

• Digital Terminal Procedures Publications (TPP)/Airport Diagrams .

• European General Aviation Safety Team (EGAST) Leaflet GA 1, Collision

Avoidance (January 1, 2010). Based o n International Civil Aviation O rganization

(ICAO ) Circular 213 –AN /130 and a safety leaflet produced by the United Kingdom

(UK) Civil Aviation Authority ( CAA ); aims to help pilots to make “ look-out” more

effective.

• F AA Safety Team (FAASTeam ), General Aviation Pilot’s Guide to Preflight Weather

Planning, Weather Self -Briefings, and Weather Decision Making (August 2006).

• Pilot /Controller Glossary :

• See and Avoid: When weather conditions permit, pilots operating IFR or VFR are

required to observe and maneuver to avoid other aircraft (refer to § 91.113 for

right-of-way rules ).

• Visual Separation : A means employed by air traffic control (ATC) to separate

aircraft in terminal areas and en route airspace in the National Airspace System

(NAS ). There are two ways to effect this separation: 1) The tower controller sees

the aircraft involved and issues instructions, as neces sary, to ensure that the

aircraft avoid each other. 2) A pilot sees the other aircraft involved , and upon

instructions from the controller provides their own separation by maneuvering

their aircraft as necessary to avoid it. This may involve following another aircraft

or keeping it in sight until it is no longer a factor.

6.2 Additional Reading Materials.

• AC 00-65, Towbar and Towbarless M ovement of Aircraft.

• AC 150/5200-30, Airport Field Condition Assessments and Winter Operations

Safety.

• AC 150/5210-20, Ground Vehicle Operations to include Taxiing or Towing an

Aircraft on Airports .

• 437t h Airlift Wing, Joint Base Charleston , SC, Mid -A ir Collision Avoidance

(MACA) (November 2017).

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3 • Aircraft Owners and Pilots Association (AOPA), Maneuvering Flight: Hazardous to

Your Health ?

• AOPA Safety Publications Articles, Basic VFR: How to Know It When You See It

(April 5, 2008).

• Aviation Safety , Is See-And-Avoid Dead ? (January 6, 2017).

• Colvin, Kurt & Dodhia, Rahul , & Dismukes, R. Key, Is Pilots’ Visual Scanning

Adequate to Avoid Mid- Air Collisions ? (2005) .

• Department of Transportation (DOT) FAA General Aviation Accident Prevention

Program , Estimating Inflight Visibility .

• FAA Aerospace Medical Education Division (AAM -400), Pilot Vision

(October 2017).

• FAA Guide to Ground Vehicle Operations .

• FAASTeam, ALC -683: Conducting Preflight Self -Briefings for Student and VFR

Pilots .

• FAASTeam, FLYING LESSONS for October 13, 2011 (October 13, 2011) .

• ICAO Circular 213–AN/130, Pilot Skills to Make “Look -Out” More Effective in

Visual Collision Avoidance.

• National Transportation Safety Board ( NTSB ), Safety Alert SA -058, Prevent Midair

Collisions: Don’t Depend on Vision Alone (April 2021).

• NTSB , Educating Controllers on Two Midair Collisions (November 16, 2016) .

The presentation contains associated Safety Alert, midair collision animations,

Safety Recommendation Report (ASR -16-06), and accident reports .

• NTSB Midair Accidents .

• NTSB , Midair Collision Over George Inlet, de Havilland DHC -2, N952DB, and

de Havilland DHC -3, N959PA, Ketchikan, Alaska, May 13, 2019 (Aircraft

Accident Report (AAR) 21/04, April 20, 2021) .

• Scott Air Force Base Midair Collision Avoidance Pamphlet (March 2017) .

• SKYbrary, Inadvertent VFR Flight Into IMC (May 2020).

• SKYbrary, Visual Scanning Technique (October 2019).

• UK CAA , SafetySense Leaflet 13, Collision Avoidance (January 2013).

7 BACKGROUND. The FAA has developed tools and advisory materials designed to

reduce the risk of either midair collisions or NMAC s. This AC is one of those advisory

materials , with a focus on a pilot ’s responsibility to see and avoid other aircraft.

7.1 ADS -B for Air Tour an d NTSB Safety Recommendations . The NTSB released Safety

Alert SA-058 on midair collision prevention technology , which states , in part, “ The

‘see-and-avoid’ concept has long been the foundation of midair collision prevention.

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4 However, the inherent limitatio ns of this concept, including human limitations,

environmental conditions, aircraft blind spots, and operational distractions, leave even the

most diligent pilot vulnerable to the threat of a midair collision with an unseen aircraft. ”

On May 13, 2019 in Ketchikan , Alaska, two aircraft collided. After reviewing the

incident, t he NTSB released Midair Collision Over George Inlet, de Havilland DHC -2,

N952DB, and de Havilland DHC -3, N959PA, Ketchikan, Alaska, May 13, 2019

(AAR -21/04, April 20, 2021), advocatin g air tour operators to install ADS -B In.

However, ADS -B regulatory requirements are for aircraft originally certificated with an

electrical system operating at or above 18,000 feet, in Clas s B and C airspace, or in

Class E airspace at and above 10,000 feet mean sea level (MSL), excluding the airspace

at and below 2,500 feet above the surface (refer to § 91.225).

7.2 Air Tour Operations . Air tour flights are typically conducted in areas of congested

airspace with pilots often distracted by requirements for posi tioning the aircraft for

sightseeing and often narrating the tour for the passengers. Air tour aircraft also tend to

congregate around common points of interest/landmarks, thereby creating congestion.

NTSB studies of several recent midair collisions conclu de that the ADS -B Traffic

Advisory System (ATAS) would provide significant a dvance warning if installed

(e.g., 30–39 seconds for the Ketchikan accident; 20+ seconds in most other recent midair

collisions ) (refer to ADS -B ATAS ).

7.3 NTSB Recommendation. Therefore, though not required by regulation for these types of

flights, it is recommended by the NTSB that air tour operators install and use an ATAS

during these flights. This action would not only increase the safety of such low -altitude

operations, but the safety of en route flights that fly through high traffic areas below

2,500 feet above the surface and outside of Class B and C airspace. Refer to §§ 91.225

and 91.227 for A DS-B operational requirements. Consider that s ee-and-avoid together

with ADS -B are lifesavers.

Note: Per the 437th Airlift Wing, Joint Base Charleston, SC , Mid-Air Collision

Avoidance (MACA) (November 2017), paragraph 11, “ IN ACCORDANCE

WITH FAR PART 91.413, WHILE IN CONTROLLED AIRSPACE, EACH

PILOT OPERATING AN AIRCRAFT EQUIPPED WITH AN OPERABLE ATC TRANSPONDER MAINTAINED SHALL OPERATE THE TRANSPONDER,

INCLUDING MODE C IF INSTALLED, ON THE APPROPRIATE MODE OR

AS ASSIGNED BY ATC. IN CLASS G AIRSPACE, THE TRANSPONDER

SHOULD BE OPERATING WHILE AIRBORNE UNLESS OTHERWISE

REQUESTED BY ATC.” For more information, refer to the Joint Base

Charleston pamphlet .

8 HUMAN LIMITATIONS AFFECTING SEE- AND- AVOID. Inherent limitations to

see-and-avoid expose the most diligent pilot to the threat of a midair coll ision with an

unseen aircraft. These limitations include but are not limited to human limitations,

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5 environmental conditions, aircraft blind spot s, and operational distractions (refer to the

Scott Air Force Base Midair Collision Avoidance Pamphlet for more information ).

8.1 Limitations of the Eye. Pilots rely on their eyes to provide most of the basic input

necessary for flying an aircraft (e.g., the aircraft ’s attitude, speed, direction, and

proximi ty to opposing traffic). As air traffic density and aircraft closing speeds increase,

the risk of midair collision also increases, and with it, so does the importance of effective

scanning. A basic understanding of the eye ’s limitations in target detection is one of the

best defenses against a collision. The following are the limitations of the eye (refer to the

Scott Air Force Base Midair Collision Avoidance Pamphlet for more information ).

8.1.1 Other Factors Affecting Vision . In flight, vision is influenced by atmospheric conditions,

glare, lighting, windshield deterioration and distortion, aircraft design, cabin temperature,

oxygen supply (particularly at night), and acceleration forces.

8.1.2 Detection of O bjects . Detection of obj ects while airb orne depends on six conditions:

• Image size—portion of the visual field filled by the object.

• Luminance —deg ree of brightness of the object .

• Contrast —difference between object and background brightness, color, and shape.

• Adaptation —degree to which the eyes adjust to surrounding illumination.

• Motion —velocity of th e object, the observer, or both.

• Exposure time —length of the time the object is exposed to view.

Note: Refer to the Scott Air Force Base Midair Collision Avoidance Pamphlet for

more informat ion.

8.1.3 Avoid Complacency: Vision In Flight . The most advanced piece of flight equipment in

any aircraft is the human eye, and since the number one cause of midair collisions is the

failure to adhere to the see- and-avoid concept, efficient use of visual techn iques and

knowledge of the eye ’s limitations will help pilots avoid collisions. Your vision ’s clarity

is influenced by some characteristics of the objects you are viewing, including :

• Your distance from the object.

•

The size, shape, and movement of the object.

• The amount of light reflected by the object.

• The object ’s contrast with the surrounding environment.

Note: Refer to the Scott Air Force Base Midair Collision Avoidance Pamphlet for

more information.

8.1.4 Accommodation and Refocusing . One inherent problem with the eye is the time required

for accommodation or refocusing. It takes 1 to 2 seconds for eyes to refocus from something up close, like a dark instrument panel 2 feet away, to a bright landmark or

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6 aircraft 1 mile away. The 1 -to-2-second delay is significant, when as Table 1 suggests it

takes 12.5 seconds to identify, react, and avoid a midair collision.

Table 1. Aircraft Identification and Reaction Time Chart

Event Seconds

See Object 0.1

Recognize Aircraft 1.0

Become Aware of Collision Course 5.0

Decision to Turn Left or Right 4.0

Muscular Reaction 0.4

Aircraft Lag Time 2.0

TOTAL Time Before Aircraft Begins to Move 12.5

Note: This table uses data from Transportation Safety Board of Canada (TSB)

Aviation Investigation Report A99P0168, which references U . S. Naval Aviation

Safety Center released data concerning typical recognition and reaction times (in

seconds) for pilots confronte d with a potential midair collision.

8.1.5 Empty -F ield Myopia . If there is little or nothing to focus on, the eyes tend to not focus.

This usually occurs on vague colorless days above a haze or cloud layer when no distinct

horizon is visible.

8.1.6 Binocular Vision . Binocular vision means using two eyes with overlapping fields of

view, allowing good perception of depth. Binocular vision and our perception can be

affected (e.g., blurring) when an object is visible to only one eye but hidden from the

other by a windshield pos t or other object , for example. Therefore, it is essential that

pilots move their head, not just their eyes, when scanning around obstructions.

8.1.7 Narrow Field of Vision/Tunnel Vision . Another inherent problem with human vision is

the narrow field of vision/tunnel vision phenomenon. Although our eyes accept light rays from an arc of nearly 200 degrees, they can only focus on and classify an object within a

relatively narrow area of approximately 10 to 15 degrees. As a result, the eye cannot

accurately i dentify what is happening in the distance when experiencing tunnel vision or

narrow field of vision, even when the eye senses move ment by its peripheral vision.

Thus, pilots tend to not believe what they see out of the corner of their eyes.

8.1.8 The Blossom Effect .

In aviation, t he “blossom effect ” refers to the visual phenomenon

where two aircraft on a collision course will appear to be virtual ly motionless to each

other. The other aircraft will remain in a seemingly stationary position, without appearing

to move or grow in size for a relatively long time, and then suddenly bloom into a huge

mass filling one of the windows. Given that we need motion or contrast to attract our

eyes’ attention, this effect becomes a frightening factor when you realize that a large bug

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7 smear or dirty spot on the windshield can hide a converging plane until it is t oo close to

be avoided.

8.1.9 Environmental Limitations . In addition to its inherent problems, the eye is also limited by

the environment. The atmosphere ’s optical properties alter the appearance of aircraft,

particularly on hazy days. VFR requires 5 statute miles (sm) of visibility, but on a hazy

day, a pilot may have difficulty detecting opposing aircraft . For this reason, we

recomm end you fly above a haze layer. For addition al information on the effect of haze,

refer to the AIM, Chapter 8.

8.1.10 Glare . Glare effects make objects hard to see, and therefore make it harder to scan

successfully for other aircraft. This is particularly true on a sunny day over a cloud layer

or during fl ight directly into the sun. An aircraft that has a high degree of contrast against

the background will be easy to see, while one with a low degree of contrast at the same distance may be impossible to see. In addition, when the sun is behind the aircraft, a

conflicting aircraft will stand out clearly, but if it is flying into the sun, the glare of the

sun will often prevent seeing the other aircraft. A dirty, scratched, opaque, or distorted windshield will make matters worse. Therefore, the FAA recommends k eeping

windshield s clean.

9 PREFLIGHT PLANNING. Before flying, § 91.103 requires each pilot in command

(PIC) to become familiar with all available information concerning that flight. In addition to the nonexhaustive list of information PICs should consider, the FAA recommends

pilots also consider the following items that can affect a pilot ’s ability to see and avoid

other aircraft .

9.1 The Airport ’s NOTAMs. A NOTAM is a notice containing information concerning the

establishment, condition, or change in airport ’s facility, service, procedures , or hazard in

the NAS , which is essential to personnel concerned with flight operations. For example,

an airport may issue a NOTAM to inform the public of construction that could affect runways or taxiways, and therefore distr act a pilot during landing and ground operations.

Also, field condition (FICON) NOTAMs provide a runway’s surface friction level and, after applying the recommended 15- percent safety margin to the Aircraft Flight Manual

(AFM) or pilot’s operating handbook (POH) required landing distance, information on

whether there is sufficient runway length to safely stop the aircraft to mitigate a runway

overrun. Refer to AC 91-79.

9.2 VFR or IFR Navigation Charts. Reviewing the route of flight on the appro priate

VFR/IFR na vigation chart s can help a pilot identify special use airspace , restricted

airspace, and Military Operations Areas (MOA) around the departure and arrival airports, as well as the terrain and its elevation along the route of flight. These include :

• Aeronauti cal Charts. Use current aeronautical charts for the route and area of flight.

• Terminal Area Charts (TAC), sectional aeronautical charts, and helicopter route

charts (refer to https://www.faa.gov/air_traffic/flight_info/aeronav/productcatalog/vfr

charts/ ).

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8 • Digital Chart Supplements (d-CS). Use current chart supplements. Access the FAA

d-CS at https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dafd/

and look under the Airport/Nav column to obtain airport -specific information, such as

the approach (APP) or departure control (DEP) frequency, or refer to the FAA

Aeronautical Informa tion Services (AIS) web page at https://www.faa.gov/air_traffic/

flight_info/aeronav/ . Either is a source for up -to-date airport information.

9.3 Weather Conditions. A pilot can ensure they will be able to meet any required VFR

requirements (e.g., ceiling and visibility requirements) by familiarizing themselves with

expected weather conditions a long the intended flight path. For example, weather services

can inform the pilot of any adverse meteorological conditions that would affect the ability to see other aircraft, such as smoke, haze, and precipitation, and increase the risk of a

midair collision o r NMAC.

9.4 Daytime or Nighttime Flight. The FAA recommends that a pilot become aware of the

time of day they will be flying to account for the expected light ’s effect on visibility, and

therefore, the effect on a pilot ’s ability to see and avoid. For example, a pilot ’s vision will

be affected if flying in the direction of the sun due to the sun ’s glare. A pilot should

consider ways to reduce the effect of the sun ’s glare on their ability to see traffic. If the

flight occurs at night, pilots should account for ground, tower, and other night time

lighting conditions that can affect their ability to see at night.

10 AIRPORT GROUND OPERATIONS. Field of vision is key to a pilot ’s ability to

remain constantly alert to all types of traffic movement on the airport surface and while flying. While operating on the airport surface, remain aware that there is both vehicle and

aircraft movement on the ramp and taxiways.

10.1 Pilot ’s Role. The following are actions pilots can take to reduce the risk of collision on

an airport ’s surfac e.

10.1.1 Airport Ground Operations . Be aware of vehicle movements, taxiing aircraft, and aircraft

being towed.

10.1.2 Pilot Workloads . To mitigate the risk of a collision during ground operations, pilots can

reduce distractions that take the pilot ’s attention away from scanning and being alert to

activ ity within their taxiing area. For example, we recommend that pilots do not perform

pretaxi or other checklists while taxiing, or engage in unnecessary conversations with

passengers. These actions, and any other actions th at take the pilot ’s attention from

scanning outside of the aircraft, can increase the risk of a ground collision.

10.1.3 Human Factors That Affect a Pilot ’s Performance. A pilot can mitigate against the risk of

collision by accounting for the human factors associ ated with fatigue, “ get-there -itis,” or

distractions during ground operations.

10.1.4 Airport Hot Spots . Airport “hot spot” information forewarns pilots and others operating

in the movement area of the airport of confusing airport geometry and intersections.

Pilots can reduce the risk of collision by becoming aware of airport s’ hot spots. A hot

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9 spot is a location within the airport movement area with a history of potential risk of a

collision or runway incursion. Therefore, we recommend pilots ide ntify hot spots a long

their ATC -issued route to their assigned runway, or a route to another location on the

airport.

10.2 Airport Communications and Taxi Procedures. Refer to radio communication

regulations in §§ 91.126, 91.127, 91.129, 91.130, 91.131, and 91.135.

10.2.1 Radio Commun i cations at Towered Airports . Before operating from the ramp area onto a

taxiway (movement area), FAA regulations require establishing two-way radio

communications with the airport ’s ATC facility (refer to §§ 91.126, 91.127, 91.129,

91.130, and 91.131) . When contacting the ATC facility, we highly recommend the pilot

use the aircraft ’s full call sign. This will help avoid confusion if there are aircraft on the

frequency with a similar call sign. For example , if the pilot mistakenly takes a clearance

for an other aircraft with a similar call sign and reads back to ATC with their aircraft ’s full

call sign , ATC will acknowledge that the clearance was for another aircraft .

10.2.2 Operations at Non -To wered Airports . To minimize collision risk, we recommend pilots

operating at non- towered airports follow the same pretaxi and taxi procedures employed

at towered airports. Given that some aircraft at a non -towered airport may operate

without radio communication, a pilot s hould scan their surrounding area; the runway in

use; and the final, base, and downwind leg s of the runway in use, and be alert for radio

transmissions by other pilots, announcing that they are landing or taking off from

runways other than the runway that the pilot is us ing. Addi tionally, the pilot should

self-announce their position and intentions , such as whether they will taxi or are entering

the runway in use for takeoff. For additional guidance, refer to AC 90-66 and AIM,

Chapter 4 .

Note: For ATC issuing an IFR clearance at a non -t owered airport, ATC may issue

an “IFR departure release, ” which is not an authorization to the pilot to take off.

The pilot must communicate over the airport ’s common traffic advisory (TA)

frequency (CTAF ) their call sign, the runway they will use to take off, their

departure direction, and their initial climb altitude, and coordinate their takeoff

with other inbound aircraft and with aircraft in the traffic pattern before taking

off, in order to mitigate the risk of a s urface or mid air collision. If the departing

aircraft has a clearance void time and cannot safely take off, then they are to

contact ATC and advise ATC that they need to obtain another clearance void

time.

10.3 Airport Communication Procedures . After obtaining the airport ’s current weather

(e.g., through Automatic Terminal Information Service ( ATIS )), we suggest the

following best practices:

10.3.1 Initiate communication with ATC by stating the aircraft ’s make and full registration

number. After receiving the VFR or IFR departure i nstructions from ATC, write down

the instruction or clearance. Then, initiate a r eadback to ATC using the same phraseology

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10 used by ATC, stating the aircraft ’s make and full registration number, as well as the

instruction or clearance.

10.3.2 Contact ground control, us ing the aircraft ’s full call sign , and write down the ta xi route to

the assigned runway. Then, read back the instructions as described above in

paragraph 10.3.1.

10.3.3 Before taxiing, review the airport ’s diagram for hot s pots along the taxi route and locate

where to hold short of any runway that you have not been cleared to cross . This will limit

head s-down time , increase scanning outside the aircraft for traffic and other conflicts , and

assist in complying with the ATC instruction/clea rance .

10.3.4 Finally, when in doubt of where to taxi or hold short of a runway, stop and ask ATC for

clarification . For e xample , “N1234, am I cleared to cross Runway 1? ” This will avoid

causing a runway incursion and a possible collision with other taxiing and landing

aircraft . Remember , you are the final authority in the operation of the aircraft (refer to

AC 91 -73).

10.4 Suggested Procedures for Collision Avoidance and When to Abort a Takeoff . The

FAA suggests the following actions to avoid a takeoff collision and help identify if a

takeoff should be aborted. There are two mnemonic devices to help remember the

actions.

10.4.1 L ights, Camera, Action . A pilot should take these actions when ATC issues the pilot a

takeoff clearance, or before taking the active runway for takeoff at a non -towered airport :

• “L ights ”: Turn on your landing light and other lights appropriate for the conditions of

flight to increase your visibility to other traffic.

• “Camera ”: Turn on your transponder for ATC identification.

• “Action ”: At a towered airport, a pilot should read back and state to ATC the

aircraft ’s full call sign . At a non -towered airport, announce your aircraft make ,

registration number, and model .

Note: When cle ared to either line up and wait or takeoff, scan the final approach

for landing aircraft and look down the runway for vehicles or aircraft that may be

on or crossing the runway before entering the runway safety area. When on the

active runway, confirm that the aircraft is aligned on the correct runway by

checking that the painted runway numbers, the magnetic “whiskey” compass, and

directional gyro all indicate the heading of the assigned takeoff runway.

10.4.2 RE ACT . When beginning the takeoff roll, perform the “ REACT ” check. This mnemonic

provides decision points to abort the takeoff if any one of the following “related items ”

are not normal.

• “ R” : Check engine revolutions per minute (r pm)/manifold pressure. Is it at takeoff

power?

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11 • “E”: Engine gauges are normal .

• “A”: Airspeed is continually increasing .

• “C”: Maintain runway centerline (RCL) .

• “T”: Know your approximate t akeoff point. This is the distance at which your aircraft

should be airborne.

Note: Knowing your airplane ’s performance, for either a sea- level takeoff or a

high-density altitude takeoff, enables a pilot to know their aircraf t’s approximate

takeoff point. This is the “T” in REACT . If any of the se items is not within

expectation, abort the takeoff by communicating over the tower or common traffic

advisory (TA) frequency ( CTAF ) the aircraft ’s call sign, announce that you are

aborting take off, exit the runway, taxi to a safe area, and figure out why one or

more of the REACT items was not met.

11 IN-FLIGHT COLLISION AVOIDANCE OPERATIONS.

11.1 Typical Midair Collision Scenarios . The following are typical midair collision

scenarios , with the appropriate pilot action to avoid a midair collision (refer to § 91.113).

11.1.1 A pproaching Head -On (During Cruise Flight ). When aircraft are approaching each other

head-on, or nearly so, each pilot of each aircraft shall alter its course to the right.

11.1.2 Overtakin g ( During Cruise Flight ). Each aircraft that is b eing overtaken has the

right -of-way. Each pilot of an overtaking aircraft shall alter its course to the right to pass

well clear.

11.1.3 Landing at Non-Towered Airports . As stated in § 91.113(g), “ Aircraft, while on final

approach to land or while landing, have the right -of-way over other aircraft in flight or

operating on the surface, except that they shall not take advantage of this rule to force an

aircraft off the runway surface which has already landed and is attempting to make way

for an aircraft on final approach . When two or more aircraft are approaching an airport

for the purpose of landing, the aircraft at the lower altitude has the right -of-way, but it

shall not take advantage of this rule to cut in front of another which is on final approach

to land or to overtake that aircraft. ”

11.1.4 Landing at T owered Airpor ts. ATC may instruct the pilot to report , for example, when on

a 2 mile left base to runway 22. This means that the pilot is to report when on the left

base to runway 22 and is to intercept runway 22’ s extended centerline for a 2 -mile final

leg for landing. This is typically used by ATC to sequence aircraft for landing.

11.1.5 Avoiding Collisions With Unmanned Aircraft Systems (UAS) . Pilots should remain

vigilant of UAS at or below 400 feet in uncontrolled airspace and at all times in visual

meteorological conditions (VMC). All pilots should remain vigilant of all aircraft if they

are able to see them, and take measures to avoid them.

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12 11.2 Collision Avoidance Assistanc e and Maneuvering and Formation Flights.

11.2.1 C ollision Avoidance Assistance. ATC provides ATAS , which is an excellent addition to

scanning resources to mitigate midair collision s. To arrange for the service, contact the

airport ’s clearance delivery and request the ATC frequency to contact after takeoff to

request ATAS . Further, the ATC facility frequency that can provid e this service is

available in the d-CS for the respective airport during your preflight planning process.

The A TC departure frequency can also be found on the airport ’s information page or by

contacting the Flight Service Station (FSS) after departure by using the flight service

common frequency of 122.2 megahertz ( MHz ). For more information, refer to the

Aeronautical Chart Users’ Guide.

11.2.2 Maneuvering and Formation Flight s.

11.2.2.1 Maneuvering Flight Cautions . More than one -quarter (26.6 percent) of all

fatal accidents in the last 10 years occurred during maneuvering flight. This

includes buzzing, formation flying, aerial work, stalls/spins, canyon flying, aerobatics, and normal flight operation. The distraction created by these

maneuvers takes away from scanning for traffic.

11.2.2.2 Forma tion Flight . Several midair collisions have occurred during

recreational formation flights. Formation flights have been enjoying a great

deal of popularity among civilian pilots over the past several years. Unfortunately, the increase in the number of form ation flights has also led to

an increase in midair collisions between the formation flight aircraft. We strongly suggest that pilots looking to fly in pairs or in formation refer to the

AOPA Safety Advisor article, “ Maneuvering Flight : Hazardous to Your

Health? ” We also recommend that pilots train with an established formation

flying training organizat ion before flying in formation.

12 EFFECTIVE SCANNING TECHNIQUES . 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 most pilots seem

to prefer horizontal back -and-forth eye move ments, each pilot should develop a scanning

pattern that is most comfortable and then adhere to it to en sure optimum scanning. See

Figure 1 below .

Figure 1. Sample Scan Pattern

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13 12.1 Phases of Flight and Blind Spot Scanning Techniques During All Phases of Fli ght.

Pilots can compensate for blind spots and enhance identifying other aircraft in a climb by

adjusting the aircraft’s pitch attitude to improve visibility over the nose of the aircraft

(which optimizes your scanning for traffic ahead), and when in level cruise or

descending, by executing gentle shallow bank turns left and right for a clear view of traffic ahead and from either side, and by scanning the rear of the aircraft by scanning

from behind the right wing through the windscreen to the back of the l eft wing . Finally,

when in the traffic pattern, the FAA recommends that pilots continue to scan for other

aircraft and check blind spots caused by fixed aircraft structures, such as doorposts and

wings. High -wing airplanes have restricted visibility above , while low -wing airplanes

have limited visibility below. The worst -case scenario is a low -wing airplane flying

above a high -wing airplane. Banking from time to time can uncover blind spots. The pilot

should also occasionally look to the rear of the airplan e to check for other aircraft. Refer

to the Airplane Flying Handbook (FAA -H-8083-3), C

hapter 7 , Ground Reference

Maneuvers .

12.2 S ee-and-Avoid Reaction Time. Table 1 a bove provides a pilot ’s reaction time upon

seeing traffic and implementing an avoidance maneuver .

13 N IGHT FLYING. Be aware of night vision limitations and give your eyes time to

adjust.

13.1 Scanning at Night. Scanning at night depends almost entirely on peripheral vision. This

is due in part to the night -blind spot that involves an area between 5 and 10 degrees wide

in the center of the visual field. A pilot can compensate for th e night -blind spot through

“off-center ” viewing, which requires looking approximately 10 degrees above, below, or

to either side of an object. To better perceive a dimly lit object in a certain direction, the

pilot should scan the area around the object rather than looking directly at the object.

Short s tops of a few seconds in each scan will help detect the light and its movement.

Note that conflicting ground lights at night increase the difficulty of detecting other aircraft. Also, avoid blinding others while taxiing by not using strobe or landing light s

until on the active runway for takeoff.

Note: Pilots utilizing a Night Vision Imaging System (NVIS), such as night

vision goggles (NVG), must be aware that some light -emitting diode (LED )

obstruction and aircraft anti collision lighting may not be visible through the NVG.

When flying with NVG, pilots should also be looking around the binocular assembly frequently, outside of the NVG view, to detect lighting that may not be

visible through the NVG.

14 AIRCRAFT SYSTEMS AND TECHNOLOGI ES FOR GROUND AND

AIRBORNE COLLISION AVOIDANCE. The FAA recommends using the following

safet y equipment to aid in collision avoidance:

• High -intensity anti collision white strobe lights , visible from all directions.

• Pulse light (collision avoidance) systems for aircraft landing lights.

10/20/22 AC 90 -48E

14 • Dual aircraft communications radios.

• TA systems (TAS), Traffic Alert and Collision Avoidance System (TCAS) I,

TCAS II, and the ADS -B In and display capability , required as of January 1, 2020.

• Weather avoidance systems.

14.1 New Tech nology: Emergency Auto Land (EAL) . Garmin’s EAL system is now

available for aircraft. This technology senses if a pilot becomes incapacitated and takes

control of the aircraft. Pilots should listen for EAL transmissions , which will provide the

aircraft ’s registration, and its action to land at a named airport. This system does not

currently have any see-and-avoid capability. The FAA d eems aircraft operating under

EAL to be in distress, and therefore have right -of-way over all other aircraft. Therefore, if

you hear an EAL message, be alert and give way. For more i nformation , refer to the

Garmin Autonomi video at https://discover.garmin.com/en -US/autonomi/ .

14.2 Avoid Inadvertent VFR Into Instrument Meteo rological Conditions (IMC ). In

addition to obtaining current and forecasted en route and terminal weather, be aware of

VFR flight into instrument weather conditions. VFR flight with reduced in- flight

visibility increases the risk of n ot seeing conflicting traffic. For more information, refer to

the FAASTeam’s General Aviation Pilot ’s Guide to Preflight Weather Planning, Weather

Self-Briefings, Weather Decision Making, and the FAA’s Estimating In -Flight Visibility ,

in paragraph 6 a bove .

15 MAINTAINING VIGILANCE. Air traffic information equipment does not relieve a

pilot’s regulatory resp onsibility to see and avoid other aircraft. Pilots should maintain

vigilance by managing distractions caused by the use of technology in the flight deck/cockpit , which is critical to the safety of the flight. While new aircraft systems can

provide pilots with a wealth of information, they can also cause fixation on the displays and draw a pilot ’s attention insi de the flight deck /cockpit and awa y from the outside

environment.

16 AIR TRAFFIC CONTROLLER LIMITATIONS. Remember that an air traffic

controller ’s view of aircraft on the airport surface is often limited by distance, depth

perception, aircraft conspicuity, an d normal visual acuity problems. Also, radar

limitations and air traffic volume can increase a controller ’s workload and prevent the

controller from providing timely TA information. Therefore, the pilot should not solely

depend upon ATC TA s for collision a voidance. The pil ot must proactively conduct

see-and-avoid procedures.

16.1 Airport Traffic Pattern Collision Avoidance . A significant number of midair collisions

and NMACs have occurred within towered and non -towered airport traffic pattern s. For

additional information on operating within traffic patterns, refer to AIM, Chapter 4;

AC 90-66; the FAA Pilot’s Handbook of Aeronautical Knowledge (FAA -H-8083-25);

and the Airplane Flying Handbook.

10/20/22 AC 90 -48E

15 17 FLIGHT INSTRUCTORS, PILOT EXAMINERS, AND PERSONS ACTING AS

SAFETY PILOTS COLLISION AVOIDANCE RECOMMENDATIONS .

17.1 Collision Avoidance Training. It is critical that flight instructors train pilot applicants to

devote maximum attention to co llision avoidance while conducting flight operations in

today ’s increasing ly complex air traffic environment. For additional details, refer to the

FAA’s Airplane Flying Handbook, Chapter 1, Introduction to Flight Training.

17.2 Flight Instructor and Safety Pilo t Responsibilities. Flight instructors and persons

acting as safety pilots can contribute to reducing the risk of aircraft collisions by :

1. Guard ing against preoccupation during flight instruction to the exclusion of

maintaining a constant vigilance for other traffic.

2. Being particularly alert during the use of advanced flight deck /cockpit technology and

the conduct of simulated instrument flight , wher e there is a tendency to “ look inside ”

excessively and forget see- and-avoid responsibilities.

3. Taking the time to teach new and advanced flight deck /cockpit technology on the

ground. Thoroughly review features as well as limitations of the equipment and the

pitfalls of fixation and overreliance on technology.

4. Placing special training emphasis on those basic problem areas of concern mentioned

in this AC . Improvements in pilot education, operating practices, conflicts,

procedures, and techniques are needed to reduce midair conflicts.

5. Student pilots communicating at towered or non -towered airports. Student pilots are

advised to inform ATC at a towered airport, and at a non -towered airport announce

over the CTAF that they are a student pilot solo.

17.3 Pilot Examiner and Certificated Flight Instructor ( CFI) Actions. Pilot examiners and

CFIs play an integral role in ensuring pilots have the collision avoidance skills necessary

to satisfy their regulatory see- and-avoid obligations. For example, the Private

Pilot –Airplane Airman Certification Standards ( FAA -S-ACS -6), Appendix 6, Safety of

Flight, requires that the evaluator assess an applicant ’s use of visual scanning and

collision avoidance procedures throughout the entire test. Other FAA guidance also

encourages CFIs to train and assess an applicant or certificated pilot ’s knowledge and

skill in their use of visual scanning and collision avoidance techniques.

18 COLLISION AVOIDANCE EDUCATIONAL RESOURCES. For further

information on training courses, documents, and events related to collision avoidance and visual scanning techniques, visit https://www.faasafety.gov

. Additional information can

also be obtained from the FAASTeam Program Manager (FPM) . Use the FAASTeam

Online Directory to locate an FPM in your state/area.

10/20/22 AC 90 -48E

16 19 AC FEEDBACK FORM. For your convenience, the AC Feedback Form is the last page

of this AC. Note any deficiencies found, clarifications needed, or suggested

improvements regarding the contents of this AC on the Feedback Form.

W

esley L. Mooty

Acting Deputy Executive Director , Flight Standards Service

Advisory Circular Feedback Form

If you find an error in this AC, have recommendations for improving it, or have suggestions

for new items/subjects to be added, you may let us know by contacting the General Aviation

and Commercial Division at 9-AFS-800-Correspondence@faa.gov or the Flight Standards

Directives Management Officer at 9-AWA-AFB-120-Directives@faa.gov.

Subject: AC 90-48E, Pilots’ Role in Collision Avoidance

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