[Federal Register Volume 62, Number 98 (Wednesday, May 21, 1997)]
[Notices]
[Pages 27924-27925]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-13176]


      

  Federal Register / Vol. 62, No. 98 / Wednesday, May 21, 1997 / 
Notices  

[[Page 27924]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


Advisory Circular 120-67; Criteria for Operational Approval of 
Auto Flight Guidance Systems

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Advisory circular.

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SUMMARY: This advisory circular (AC), published with a related final 
rule amendment elsewhere in this separate part of the Federal Register, 
states an acceptable means, but not the only means, for obtaining 
operational approval of the initial engagement or use of an Auto Flight 
Guidance System (AFGS) under Title 14 of the Code of Federal 
Regulations (14 CFR) part 121, Sec. 121.579(d); part 125, 
Sec. 125.329(e); and part 135, Sec. 135.93(e) for the takeoff and 
initial climb phase of flight. This advisory circular supports recent 
changes in the Title 14 that allow use of the autopilot at lower 
altitudes than previously allowed.

FOR FURTHER INFORMATION CONTACT:
Richard A. Temple, AFS-410, Flight Standards Service, Federal Aviation 
Administration, 800 Independence Avenue, SW., Washington, DC 20591, 
telephone (202) 267-5824.

SUPPLEMENTARY INFORMATION:

1. Purpose

    This advisory circular (AC) states an acceptable means, but not the 
only means, for obtaining operational approval of the initial 
engagement or use of an Auto Flight Guidance System (AFGS) under Title 
14 of the Code of Federal Regulations (14 CFR) part 121, 
Sec. 121.579(d); part 125, Sec. 125.329(e); and part 135, 
Sec. 135.93(e) for the takeoff and initial climb phase of flight.

2. Applicability

    The criteria contained in this AC are applicable to operators using 
commercial turbojet and turboprop aircraft holding Federal Aviation 
Administration (FAA) operating authority issued under SFAR 38-2 and 14 
CFR parts 119, 121, 125, and 135. The FAA may approve the AFGS 
operation for the operators under these parts, where necessary, by 
amending the applicant's operations specifications (OPSPECS).

3. Background

    The purpose of this AC is to take advantage of technological 
improvements in the operational capabilities of autopilot systems, 
particularly at lower altitudes. This AC complements a rule change that 
would allow the use of an autopilot, certificated and operationally 
approved by the FAA, at altitudes less than 500 feet above ground level 
in the vertical plane and in accordance with Secs. 121.189 and 135.367, 
in the lateral plane.

4. Definitions

    a. Airplane Flight Manual (AFM). A document (under 14 CFR part 25, 
Sec. 25.1581) which is used to obtain an FAA type certificate. This 
document contains the operating procedures and limitations and 
performance information applicable to a particular airplane type in 
order to safely operate that aircraft and conform to the type 
certificate.
    b. Autopilot. An aircraft system and associated sensors designed to 
provide automatic control of the pitch, roll, and, in certain 
instances, yaw axis of an aircraft.
    c. Auto Flight Guidance System (AFGS). Aircraft systems, such as an 
autopilot, autothrottles, displays, and controls, that are 
interconnected in such a manner to allow the crew to automatically 
control the aircraft's lateral and vertical flightpath and speed. A 
flight management system (FMS) is sometimes associated with an AFGS.
    d. Auto Throttle System (ATS). A system selected by the crew to 
provide automatic engine thrust control, as required, to achieve and 
maintain desired aircraft speed or vertical flight profile.
    e. Control Wheel Steering (CWS). A selectable feature of some 
autopilots that directly relates control wheel displacement to a 
desired aircraft response. The pilot's force or displacement inputs of 
the control wheel/column or stick are transmitted by the autopilot into 
appropriate commands to the control surfaces to achieve the desired 
aircraft pitch, roll, or yaw response.
    f. Flight Director (FD). An instrument display system providing 
visual commands for aircraft control by displaying appropriate command 
indications on the primary flight display. The flightcrew use these 
command indications to manually fly the aircraft or monitor the 
autopilot.
    g. Flight Management Systems (FMS). An integrated system used by 
flightcrews for flight planning, navigation, performance management, 
aircraft guidance and flight progress monitoring.
    h. Minimum Altitude for AFGS Engagement. Unless otherwise specified 
by the FAA, the minimum height relevant to the airport elevation, and 
runway elevation over which the crew may either initially engage an 
AFGS for automatic flight after takeoff or allow the AFGS to remain 
engaged during approach and landing.

5. Discussion

    a. AFGS capabilities have steadily increased and improved with 
time. Air carrier crews now routinely use autoflight features that are 
operational during takeoff and landing/roll-out (e.g., control wheel 
steering, automatic landing, automatic throttles, and wingload 
alleviation).
    b. Some aircraft now have automatic features identified for 
operations specifically at low altitudes (e.g., for noise abatement) 
which when used, contribute to performance, workload, cost, noise, and 
safety benefits. Such features will be certificated on the aircraft by 
either type certification or supplemental type certification. Operators 
may obtain operational approval for in service use by following the 
guidance in this AC. This should meet the intent of Secs. 121.579, 
125.329, and 135.93 for existing aircraft and describe acceptable 
methods for demonstration of these systems for new or modified 
aircraft.
    c. In accordance with the regulations, Secs. 121.579(d), 
125.329(e), and 135.93(e), the autopilot system may not be engaged 
below the minimum engagement certification altitude specified in the 
AFM or an altitude specified by the Administrator, whichever is higher, 
and may not be engaged below that altitude without a finding by the 
Administrator that use of the system will not otherwise affect the 
safety standards required by those sections of the regulations. 
Additionally, the Flight Standardization Board (FSB) report for the 
aircraft may contain further conditions or limitations regarding AFGS 
engagement after takeoff. Inclusion of a specified altitude for use 
after takeoff in the AFM or the FSB report does not constitute approval 
to conduct operations. Authorization to engage the AFGS at the altitude 
specified in the AFM are made by a revision to the operator's OPSPECS. 
For aircraft with an AFM that specifies an AFGS engagement altitude for 
takeoff, principal operations inspectors (POI's) may issue OPSPECS 
authorizing the engagement of the AFGS after takeoff at or above the 
altitude specified in the AFM or as specified in the FSB report, 
whichever is higher. When an FSB report is not available, the FAA does 
not approve an altitude below that specified in the AFM or 200 feet, 
whichever is higher. The expectation is that as technology continues to 
advance, additional operational and safety

[[Page 27925]]

benefits can be derived from using improved autopilot technology. Such 
a benefit may eventually include the use of an AFGS from the beginning 
of the takeoff phase of flight, in which case the rules will have to be 
amended.

6. Operational Concept

    a. The AFGS, as discussed in this AC, consists of an Autopilot 
(pitch, roll, and yaw) Flight Guidance System, which if used in 
conjunction with other available components such as FMS, autothrottle, 
etc. will enhance safety and ease pilot workload. Any or all of the 
many available automatic operational features are selectable at the 
pilot's discretion in modern transport aircraft. This allows a clear 
distinction to be made in contrast to the primary flight control system 
which may also be largely automatic and electronic, but is not normally 
deselectable at the flightcrew's discretion, such as the yaw dampers.
    b. There are several functions of an AFGS that could be presented 
for operational approval. These functions could be used singularly or 
in combination with each other. The following are examples of these 
functions:
    (1) Setting takeoff thrust.
    (2) Initial climb.
    (3) Noise abatement profiles.
    (4) Engine failure recognition.
    (5) Reduced climb performance profiles.
    c. Approval for using any of the above functions may include 
changing equipment, equipment support, and operational procedures in 
the aircraft manufacturer's AFM and in the air carrier's operations 
manual. Approval may require adjustments to the air carrier's OPSPECS.
    d. Once the new operation is developed and approved, maintenance 
and flightcrew training programs must be adjusted and approved. 
Qualification of maintenance personnel and flightcrews must be 
accomplished before flight operations with the new procedure can be 
implemented.

7. Airport and Ground Facilities

    An applicant authorized to use an AFGS may have certain constraints 
related to airports or ground facilities specified in the operator's 
OPSPECS where such specific provisions are necessary (e.g., operations 
based on special procedures at airports with adjacent mountainous 
terrain, operations requiring runway guidance information, etc.).

8. Airborne Equipment

    AFGS system criteria will be defined in the AFM.

9. Pilot Training and Proficiency Program

    The operator's training program for flight-crews should provide 
ground and flight training in the following subjects:
    a. Knowledge of airport and ground facilities--as defined in the 
airborne equipment certification, AFM, and/or Flight Operations Manual 
(FOM) to include new minima criteria for weather operations authorized 
through OPSPECS.
    b. The use of the AFGS within the parameters indicated by the AFM 
and FOM. This should include all normal and abnormal procedures.
    c. Training should include checking in the flight tasks (maneuvers 
and procedures) that have been adjusted in the manuals.

10. Operations Manual and Procedures

    Procedures, instructions, and information to be used by flightcrews 
should be developed by each air carrier to include, as applicable, the 
following:
    a. Flight Crewmember Duties. Flight crewmember duties during 
initial engagement or use of the AFGS should be described in the air 
carrier's operations manual. These duties should contain a description 
of the responsibilities and tasks for the pilot flying the aircraft and 
the pilot not flying the aircraft during all stages of operation. The 
duties of the third flight crewmember, if required, should also be 
explicitly defined.
    b. Training Information. Training requirements and procedures 
should be provided in the operator's approved training program.

11. Maintenance Program

    Each operator should establish a maintenance and reliability 
program, acceptable to the Administrator, to ensure that the airborne 
equipment will continue at a level of performance and reliability 
established by the manufacturer or the FAA. [part 121, subpart L; part 
125, subpart G; and part 135, subpart J] The program should include the 
following:
    a. Maintenance Personnel Training. Each operator should establish 
an initial and recurrent training program, or arrange for contract 
maintenance that is acceptable to the Administrator for personnel 
performing maintenance work on airborne systems and equipment. 
Personnel training records should be maintained.
    b. Test Equipment and Standards. The operator's program for 
maintenance of line (ramp) test equipment, shop (bench) test equipment, 
and a listing of all primary and secondary standards utilized during 
maintenance of test equipment which relates to airborne system 
operation should be submitted to the Administrator for determination of 
adequacy. Emphasis should be placed on standards associated with flight 
directors, automatic flight control systems, maintenance techniques and 
procedures of associated redundant systems.
    c. Maintenance Procedures. Any changes to maintenance procedures, 
practices, or limitations established in the qualification for airborne 
system operations are to be submitted to the Administrator for 
acceptance before such changes are adopted.

12. Engineering Modifications.

    Titles and numbers of all modifications, additions, and changes 
that were made to qualify aircraft systems performance should be 
provided to the Administrator. [part 21, subparts D and E]

    Dated: May 13, 1997.
W. Michael Sacrey,
Acting Deputy Director, Flight Standards Service.
[FR Doc. 97-13176 Filed 5-20-97; 8:45 am]
BILLING CODE 4910-13-M