[Federal Register Volume 59, Number 82 (Friday, April 29, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10167]


[[Page Unknown]]

[Federal Register: April 29, 1994]


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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).

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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]
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