Notification to ATC of Deviations From ATC Clearances and Instructions in Response to Traffic Alert and Collision Avoidance System Resolution Advisories

DEPARTMENT OF TRANSPORTATION

14 CFR Part 91

[Docket No. 27717; Notice No. 94-16]

RIN 2120-AF35

Notification to ATC of Deviations From ATC Clearances and

Instructions in Response to Traffic Alert and Collision Avoidance

System Resolution Advisories

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This action proposes to codify a previously announced policy

extended to pilots during the initial testing of TCAS, during the

Limited Implementation Plan (LIP) for TCAS, and during the actual

implementation of TCAS under the TCAS Transition Plan (TTP) that

permitted pilots to deviate from an air traffic control (ATC) clearance

or instruction in non-emergency situations in response to a traffic

alert and collision avoidance system (TCAS) resolution advisory (RA).

The language contained in current regulations suggests that deviation

from an ATC clearance is only authorized in an emergency situation.

This proposal would add the TCAS RA as a reason to deviate from a

clearance. This proposal would require that whenever a pilot deviates

from an ATC clearance or instruction, ATC would be advised as soon as

practicable. This proposal is intended to clarify and define pilot

reporting requirements in the event a pilot deviates from an air

traffic control clearance or instruction in response to a TCAS

resolution advisory.

DATES: Comments must be received on or before May 31, 1994.

ADDRESSES: Comments on this notice should be mailed, in triplicate, to:

Federal Aviation Administration, Office of Chief Counsel, Attention:

Rules Docket (AGC-200), Docket No. 27717, 800 Independence Avenue, SW.,

Washington, DC 20591. Comments delivered must be marked Docket No.

27717. Comments may be examined in room 915G weekdays between 8:30 a.m.

and 5 p.m., except on Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Mrs. Ellen Crum, Air Traffic Rules Branch, ATP-230, Airspace Rules and

Aeronautical Information Division, Federal Aviation Administration, 800

Independence Avenue, SW., Washington, DC 20591; telephone (202) 267-

8783.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule by submitting such written data, views, or arguments as

they may desire. Comments relating to the environmental, energy,

federalism, or economic impact that might result from adopting the

proposals in this notice are also invited. Substantive comments should

be accompanied by cost estimates. Comments should identify the

regulatory docket or notice number and should be submitted in

triplicate to the Rules Docket address specified above. All comments

received on or before the closing date for comments specified will be

considered by the Administrator before taking action on this proposed

rulemaking. The proposals contained in this notice may be changed in

light of comments received. All comments received will be available,

both before and after the closing date for comments, in the Rules

Docket for examination by interested persons. A report summarizing each

substantive public contact with Federal Aviation Administration (FAA)

personnel concerned with this rulemaking will be filed in the docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must include a pre-addressed,

stamped postcard on which the following statement is made: ``Comment to

Docket No. 27717.'' The postcard will be date stamped and mailed to the

commenter.

Availability of NPRM's

Any person may obtain a copy of this NPRM by submitting a request

to the Federal Aviation Administration, Office of Public Affairs,

Attention: Public Inquiry Center, APA-430, 800 Independence Avenue,

SW., Washington, DC 20591, or by calling (202) 267-3484. Communications

must identify the notice number of this NPRM.

Persons interested in being placed on the mailing list for future

NPRM's should request from the above office a copy of Advisory Circular

No. 11-2A, Notice of Proposed Rulemaking Distribution System, which

describes the application procedure.

Background

On December 26, 1989, the FAA published a petition for rulemaking

received from the Air Transport Association (ATA) that requested the

FAA to amend Sec. 91.75(a) of the Federal Aviation Regulations (FAR) to

permit a pilot to deviate from an ATC clearance when responding to a

TCAS RA (54 FR 52951). [Effective August 18, 1990, Part 91 of the FAR

was revised (54 FR 34284; August 18, 1989) to renumber all of its

sections. Section 91.75(a) was renumbered as Sec. 91.123(a).]

Currently, the FAR's do not provide for any deviation from an ATC

clearance or instruction except in an emergency situation. However,

during the initial trial and implementation of TCAS II, the FAA

notified pilots that no enforcement action would be initiated if the

pilot deviated from ATC clearances when responding to TCAS RA's. This

notification was provided in a letter signed by the former FAA

administrator James B. Busey. The letter was published as appendix C to

the TCAS Transition Program (TTP) Project Management Plan, dated August

1, 1990. The FAA also provided procedural guidance, including ATC

communication requirements, in Advisory Circular 120-55, ``Air Carrier

Operational Approval and Use of TCAS II'' dated October 23, 1991, and

later amended as AC 120-55A dated August 27, 1993. The policy and

guidance proved successful during the testing and implementation of

TCAS II.

The ATA petition states that TCAS is an advisory system and not an

emergency system. The ATA felt that pilots should be able to comply

with a TCAS RA without exercising emergency authority. The ATA petition

mirrors current FAA policy and guidance for use of TCAS II. The

petition drew no negative comments and one positive comment, from the

Airline Pilots Association (ALPA), in support of the proposal.

Section 91.123 of the FAR states, in pertinent part, that each

pilot in command who, in an emergency, deviates from an ATC clearance

or instruction shall notify ATC of that deviation as soon as possible.

This provision could be interpreted to mean that deviations for non-

emergency related reasons are not authorized.

TCAS II is now installed on approximately 6000 aircraft worldwide.

Over the past 3 years, more than 15 million flight hours of operational

experience have been accumulated.

TCAS Overview

TCAS equipment in an airplane interrogates the ATC transponders of

other aircraft nearby. By computer analysis of the replies, TCAS

equipment determines which transponder-equipped aircraft are potential

collision hazards and provides appropriate advisory information to the

flight crew. If a TCAS-equipped airplane interrogates an aircraft that

is equipped with a Mode A transponder, range and azimuth information

will be provided to the TCAS-equipped aircraft. If the interrogated

aircraft is equipped with an altitude encoding transponder (Mode C or

Mode S), then relative altitude information will be provided in

addition to range and azimuth. TCAS equipment cannot detect the

presence of an aircraft that is not equipped with a transponder.

TCAS equipment performs proximity tests on each detected target. If

the path of a target is projected to pass within certain horizontal and

vertical distance criteria, then that target is declared an intruder.

An intruder that is determined to pose an even greater risk of

collision is declared a threat. When a threat is declared, TCAS

equipment will determine the appropriate direction that the TCAS-

equipped aircraft must move (climb or descent) and the vertical rate

that must be maintained to achieve separation from the threat.

There are two classes of advisories provided by TCAS equipment. The

first class, traffic advisories (TA's), provides supplemental

information to the pilot that aids in visual detection of other

aircraft. TA's include the range, bearing, and, if the intruder has

altitude-reporting equipment, the altitude of the intruding aircraft

relative to the TCAS-equipped aircraft. TA's without altitude may also

be provided from non-altitude reporting transponder-equipped intruders.

The second class of advisories, resolution advisories (RA's), indicates

the vertical direction and rate that must be achieved to prevent

insufficient separation.

TCAS I equipment provides TA's that only assist the pilot in

visually detecting an intruder aircraft. TCAS II equipment provides

TA's and RA's only in the vertical plane. TCAS III, which is still

under development, will provide TA's and RA's in both the vertical and

horizontal planes.

Related Agency Actions

On January 10, 1989, the FAA published a final rule (54 FR 940),

the ``TCAS rule,'' which required airplanes having more than 30

passenger seats and operated under parts 121, 125, or 129 to be

equipped with TCAS II by December 30, 1991. The TCAS rule also required

airplanes having 10 to 30 passenger seats and operated under parts 129

or 135 to be equipped with TCAS I by February 9, 1995.

On April 9, 1990, the FAA amended the TCAS rule by revising the

schedule for the installation of TCAS II equipment in airplanes having

more than 30 passenger seats (55 FR 13242). Operators of airplanes

having more than 30 passenger seats and operated under part 121 are

required to install TCAS II equipment in accordance with a phased-in

schedule so that 100% of an operator's covered airplanes will have TCAS

II equipment by December 30, 1993. Operations conducted under parts 125

or 129 with airplanes having more than 30 passenger seats are also

required to install TCAS II equipment by December 30, 1993.

The Proposal

The FAA believes that most TCAS RA's will involve changes in the

rate of descent or climb in order to mitigate potential collision

hazards. Such TCAS RA's routinely will not necessitate a pilot

deviating from an ATC clearance or instruction. The issue of advising

ATC of the receipt of or compliance with a TCAS RA that does not

involve a deviation from a clearance or instruction is a matter of

pilot judgment and discretion.

The FAA also has determined that the majority of deviations from

ATC clearances or instructions in response to TCAS RA's will be

appropriate and necessary to resolve potential collision hazards with

other transponder-equipped aircraft. In such cases, pilots executing

the appropriate maneuvers are expected to advise ATC of the deviations

as soon as possible.

The current language of Sec. 91.123(c) provides that a pilot who

deviates from an ATC clearance or instruction, in an emergency, shall

notify ATC as soon as possible. If a pilot deviates from an assigned

altitude in response to a TCAS RA, but does not believe that an

emergency exists, that pilot may determine, based on current

Sec. 91.123(c), that an advisory to ATC is not required. The proposal

would specifically state that a report to ATC is required.

Air traffic controllers base their control and traffic management

decisions on the expectation that pilots will comply with ATC-assigned

routes, altitudes, and other clearances and instructions. If a pilot

must deviate from an ATC clearance or instruction, the controller mut

be given timely notification of that deviation so that appropriate

instructions and/or advisories can be issued to ensure a safe, orderly,

and expeditious flow of traffic. By advising ATC as soon as possible

after a deviation, the controller can evaluate the situation, determine

the most appropriate and safe course of action, and issue alternate

instructions if necessary.

The FAA has concluded that this proposed rule is necessary to

codify existing policy for pilots to notify ATC as soon as possible

after any deviation from an ATC clearance or instruction in response to

a TCAS RA, whether that deviation was emergency-related or not.

Further, the FAA has determined that this proposed rule will not add or

change any notification or reporting requirements for deviations that

are necessary to resolve potential or imminent collision hazards. The

FAA has always intended that notification to ATC of a deviation from a

clearance or instruction is necessary and required, whether that

deviation is emergency-related or not. This action serves only to

reinforce and codify that intention.

Accordingly, the FAA proposes to amend Sec. 91.123 of the FAR to

authorize deviations from an ATC clearance or instruction when

responding to a TCAS RA. In addition, pilots would be required to

advise ATC of the TCAS RA deviation from an ATC clearance or

instruction whether emergency-related or not.

Economic Evaluation

The FAA has determined that this NPRM is not a ``significant

regulatory action'', as defined by Executive Order 12866 (Regulatory

Planning and Review). The anticipated benefits and costs associated

with this NPRM are summarized below. (A detailed discussion of costs

and benefits is contained in the full evaluation in the docket for this

NPRM). The agency has determined that this proposed rule would be cost-

beneficial because it imposes no costs and would promote air safety.

There would not be any changes in notification or reporting

requirements for deviations from ATC clearances that are necessary to

avoid potential collision hazards. The proposal would clarify and

codify existing policy and guidance requirements that pilots who

deviate from their assigned altitudes in response to a TCAS resolution

advisory provide timely notice of that deviation to air traffic control

in both non-emergency situations and emergency situations. Such

notification would give controllers an opportunity to resolve any

conflicts resulting from a TCAS II- equipped aircraft being at other

than the assigned altitude.

International Trade Impact Statement

This proposed rule would not impose a competitive disadvantage to

either U.S. air carriers doing business abroad or foreign air carriers

doing business in the United States. This assessment is based on the

fact that this proposed rule would not impose additional costs on

either U.S. or foreign air carriers.

Regulatory Flexibility Determination

In accordance with the Regulatory Flexibility Act of 1980, the FAA

has determined that this proposed rule would not have a significant

economic impact, positive or negative, on a substantial number of small

entities. This assessment is based on the fact that the proposed rule

would not impose any additional cost on aircraft operators.

Paperwork Reduction Act

There are no requirements for information collection associated

with this proposed rule that would require approval from the Office of

Management and Budget pursuant to the Paperwork Reduction Act of 1980

(Pub. L. 96-511).

Federalism Implications

The regulation proposed herein would not have substantial direct

effects on the states, on the relationship between the national

government and the states, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposed rule does not have sufficient federalism implications to

warrant the preparation of a Federalism Assessment.

International Civil Aviation Organization and Joint Aviation

Regulations

In keeping with the U.S. obligations under the Convention on

International Civil Aviation (ICAO), it is FAA policy to comply with

ICAO Standards and Recommended Practices (SARP) to the maximum extent

practicable. The FAA has determined that this NPRM complies with the

ICAO SARP.

Conclusion

For the reasons discussed in the preamble, and based on the

findings in the Regulatory Flexibility Determination and the

International Trade Impact Analysis, the FAA has determined that this

proposed regulation is not a ``significant regulatory action'' under

Executive Order 12866. This proposed regulation is not considered

significant under DOT Order 2100.5, Policies and Procedures (44 FR

11034; February 26, 1979). In addition, the FAA certifies that this

proposed regulation, if adopted, will not have a significant economic

impact, positive or negative, on a substantial number of small entities

under the criteria of the Regulatory Flexibility Act. A regulatory

evaluation of the NPRM, including a Regulatory Flexibility

Determination and Trade Impact Analysis, has been placed in the docket.

A copy may be obtained by contacting the person identified under FOR

FURTHER INFORMATION CONTACT.

List of Subjects in 14 CFR Part 91

Air traffic control, Aircraft, Aviation safety.

The Proposed Amendment

In consideration of the foregoing, the Federal Aviation

Administration proposes to amend Sec. 91.123 of the Federal Aviation

Regulations (14 CFR part 91) as follows:

PART 91--GENERAL OPERATING AND FLIGHT RULES

1. The authority citation for part 91 continues to read as follows:

Authority: 49 U.S.C. 1301(7), 1303, 1344, 1348, 1352 through

1355, 1401, 1421 through 1431, 1471, 1472, 1502, 1510, 1522, and

2121 through 2125; articles 12, 29, 31, and 32(a) of the Convention

on International Civil Aviation (61 Stat. 1180); 42 U.S.C. 4321 et

seq.; E.O. 11514, 35 FR 4247, 3 CFR, 1966-1970 Comp., p. 902; 49

U.S.C. 106(g).

2. Section 91.123 is amended by revising paragraphs (a) and (c) as

follows:

Sec. 91.123 Compliance with ATC clearances and instructions.

(a) When an ATC clearance has been obtained, no pilot in command

may deviate from that clearance unless an amended clearance is

obtained, an emergency exists, or the deviation is in response to a

traffic alert and collision avoidance system resolution advisory.

However, except in Class A airspace, a pilot may cancel an IFR flight

plan if the operation is being conducted in VRR weather conditions.

When a pilot is uncertain of an ATC clearance, that pilot shall

immediately request clarification from ATC.

* * * * *

(c) Each pilot in command who, in an emergency, or in response to a

traffic alert and collision avoidance system (TCAS) resolution

advisory, deviates from an ATC clearance of instruction shall notify

ATC of that deviation as soon as possible.

* * * * *

Issued in Washington, DC on April 21, 1994.

Harold W. Becker,

Manager, Airspace Rules and Aero Information Division, Air Traffic

Rules & Procedures Service.

[FR Doc. 94-10167 Filed 4-28-94; 8:45 am]

BILLING CODE 4910-13-M