Appendix B B-2 Term Definition Autothrust The autothrust function provides automatic control of the thrust of the airplane. The term includes the sensors, computers, power supplies, servo-motors/actuators and associated wiring, necessary for its function. It includes any indications and controllers necessary for the pilot to manage and supervise the system. Any part of the autothrust that remains connected to the engine controls when the autothrust is not in use is regarded as a part of the engine control system.
Caution A flight deck indication that alerts the flightcrew to a non-normal operational or airplane system condition that requires immediate crew awareness. Subsequent pilot corrective compensatory action will be required.
Cognitive Task Analysis An analysis that focuses on the mental processes, skills, strategies, and use of information required for task performance.
Complex A system is complex when its operation, failure modes, or failure effects are difficult to comprehend without the aid of analytical methods.
Conformal Positioned and scaled with respect to the outside view.
Control Wheel Steering A flight guidance system (FGS) function which, when engaged, (CWS) enables the pilot/first officer to manually fly the airplane by positioning the flight control surfaces using the autopilot servos.
The positions of the flight deck controls (for example, control column, control wheel) are determined by the FGS, which converts them into autopilot servo commands. The autopilot servos, in turn, drive the appropriate flight control surfaces.
Conventional A system is considered to be conventional if its functionality, the technological means used to implement its functionality, and its intended usage are all the same as, or closely similar to, that of previously approved systems that are commonly used.
Engage A steady state that exists when a flightcrew request for mode or system functionality has been satisfied.
Error An omission or incorrect action by a crewmember or maintenance personnel, or a mistake in requirements, design, or implementation.
Appendix B B-3 Term Definition Failure An occurrence that affects the operation of a component, part, or element such that it can no longer function as intended (this includes both loss of function and malfunction).
Note: Errors may cause failures, but are not considered to be failures.
Failure Condition A condition having an effect on the airplane and/or its occupants, either direct or consequential, which is caused or contributed to by one or more failures or errors, considering flight phase and relevant adverse operational or environmental conditions, or external events.
Fail Operational System A system capable of completing an operation, following the failure of any single element or component of that system, without pilot action.
Fail Passive System A system which, in the event of a failure, results in:
(a) No significant deviation in the aircraft flightpath or attitude, and
(b) No out-of- trim condition at disengagement that is not easily controlled by the pilot.
Flight Director (FD) A visual cue or set of cues that are used during manual control of the airplane as command information to direct the pilot how to maneuver the airplane, usually in pitch, roll and/or yaw, to track a desired flightpath. The FD, displayed on the pilot’s primary head down Attitude-Director Indicator (ADI) or Head-Up Display (HUD), is a component of the FGS and is integrated with airborne attitude, air data, and NAV systems.
Flight Guidance System A system consisting of one or more of the following elements:
(FGS) • Autopilot
• Flight director, and
• Automatic thrust control.
An FGS also includes any interactions with stability augmentation and trim systems.
Appendix B B-4 Term Definition Flight Management System An aircraft area navigation (RNAV) system and associated (FMS) displays and input/output devices(s) having complex multiwaypoint lateral navigation (LNAV) and vertical navigation (VNAV) capability (or equivalent), data entry capability, database memory to store route and instrument flight procedure information, and display readout of navigation (NAV) parameters. The FMS provides guidance commands to the FGS for the purpose of automatic navigation and speed control when the FGS is engaged in an appropriate mode or modes (for example, VNAV, LNAV, RNAV).
Head Up Display (HUD) A transparent optical display system located level with and between the pilot and the forward windscreen. The HUD displays a combination of control, performance, NAV, and command information superimposed on the external field of view. It includes the display element, sensors, computers and power supplies, indications and controls. It is integrated with airborne attitude, air data and navigation NAV systems, and as a display of command information is considered a component of the FGS.
Inadvertent A condition or action that was not planned or intended.
Latent Failure A failure is latent until it is made known to the flightcrew or maintenance personnel. A significant latent failure is one that would, in combination with one or more specific failures or events, result in a hazardous or catastrophic failure condition.
Limit Flight Envelope The outermost flight envelope of the airplane normally associated with the limit loads of the airplane structure.
Minimum Engage Height The minimum height after takeoff at which the flightcrew is permitted to engage the autopilot. Also referred to as minimum use height takeoff. See Minimum Use Height.
Minimum Use Height A height specified during airworthiness demonstration or review (MUH) above which, under standard or specified conditions, a probable failure of a system is not likely to cause a significant path displacement unacceptably reducing flightpath clearance from specified reference surfaces (for example, airport elevation) or specified obstacle clearance surfaces.
Minor Transient See Transient.
Appendix B B-5 Term Definition Mode A mode is system configuration that corresponds to a single (or set of) FGS behavior(s).
Mode Reversion An automatic mode change that returns the FGS to a previously engaged mode or to a predetermined “default” mode for that condition. This may occur due to several reasons, such as specific criteria becoming satisfied or because the FGS cannot perform the currently selected operation. This type of mode change is not requested by the flightcrew and therefore may be unexpected.
Non-Normal Condition A condition or configuration of the airplane that would not normally be experienced during routine flight operations— usually due to failures. Also includes unusual airplane ferry configurations, such as transporting a spare engine or landing gear locked down ferry flight.
Normal Condition Any fault-free condition typically experienced in normal flight operations. Operations typically well within the aircraft flight envelope, and with routine atmospheric and environmental conditions.
Normal Flight Envelope The range of altitude and operating speeds that are defined by the airplane manufacturer as consistent with conducting flight operations for which the airplane is designed. This envelope is generally associated with practical, routine operation and/or prescribed conditions, whether all-engine or engine inoperative.
Other than Normal The summation of rare normal and non-normal conditions.
Condition Override (of engaged FGS An action taken by the flightcrew intended to prevent, oppose, or functions) alter an operation being conducted by a flight guidance function, without first disengaging that function.
Rare Normal Condition A fault-free condition that is experienced infrequently by the airplane due to severe environmental conditions (for example, significant wind, turbulence, or asymmetric icing).
Redundancy The presence of more than one independent means for accomplishing a given function or flight operation.
Select The flightcrew action of requesting functionality or an end state condition.
Appendix B B-6 Term Definition Significant Transient See Transient.
Stability Augmentation Automatic systems that provide or enhance stability for specific System aerodynamic characteristics of an airplane (for example, yaw damper, longitudinal stability augmentation system, Mach trim).
System A combination of components, parts, and elements that are interconnected to perform one or more specific functions.
Transient A disturbance in the control or flightpath of the airplane that is not consistent with response to flightcrew inputs or environmental conditions.
Minor Transient: A transient that would not significantly reduce safety margins and which involves flightcrew actions that are well within their capabilities involving a slight increase in flightcrew workload or some physical discomfort to passengers or cabin crew.
Significant Transient: A transient that would lead to a significant reduction in safety margins, an increase in flightcrew workload, discomfort to the flightcrew, or physical distress to passengers or cabin crew, possibly including nonfatal injuries.
Note: The flightcrew should be able to respond to any significant transient without:
• Exceptional piloting skill, alertness, or strength,
• Forces greater than those given in § 25.143(c), and
• Accelerations or attitudes in the airplane that might result in further hazard to secured or nonsecured occupants.
Warning A flight deck indication that alerts the flightcrew to a nonnormal operational or airplane system requiring immediate recognition. Immediate corrective or compensatory action by the flightcrew is required.
Appendix C C-1 APPENDIX C. ACRONYMS Table C-1. Acronyms and Definitions Acronym Definition AC Advisory Circular ADI Attitude-Director Indicator AFM Airplane Flight Manual AGL Above Ground Level ARP Aerospace Recommended Practice ATC Air Traffic Control CDI Course Deviation Indicator CFR Code of Federal Regulations CG Center of Gravity CWS Control Wheel Steering DA Decision Altitude DA(H) Decision Altitude (Height) DME Distance Measuring Equipment EVS Enhanced Vision System FAA Federal Aviation Administration FCOM Flightcrew Operations Manual FD Flight Director FGS Flight Guidance System FL Flight Level FMA Flight Mode Annunciator
Appendix C C-2 Acronym Definition FMS Flight Management System GBAS Ground-Based Augmentation System GLS GBAS Landing System GPWS Ground Proximity Warning System HDD Head Down Display HUD Head-Up Display ICAO International Civil Aviation Organization ILS Instrument Landing System IMA Integrated Modular Avionics IMC Instrument Meteorological Conditions LNAV Lateral Navigation LOC Localizer MDA(H) Minimum Descent Altitude (Height) MSL Mean Sea Level MSP Mode Select Panel MUH Minimum Use Altitude/Height (autopilot) NAV Navigation ND Navigation Display NDB Non-Directional Beacon PANS-OPS Procedures for Air Navigation Services—Aircraft Operations PF Pilot Flying PFD Primary Flight Display PM Pilot Monitoring
Appendix C C-3 Acronym Definition RNAV Area Navigation RNP Required Navigation Performance RTO Rejected Takeoff RVSM Reduced Vertical Separation Minimum SAE Society of Automotive Engineers TCAS Traffic Alert and Collision Avoidance System TCS Touch Control Steering TERPS Terminal Instrument Procedures TOGA Takeoff/Go-Around VDF/MDF Demonstrated Flight Diving Speed/Demonstrated Flight Diving Mach VMO/MMO Maximum Operating Limit Speed/Maximum Operating Limit Mach VR Rotation Speed VSR Reference Stall Speed (see § 25.103) V2 Takeoff Safety Speed VMC Visual Meteorological Conditions VNAV Vertical Navigation VOR Very high frequency Omnidirectional Range WAT Weight, Altitude, and Temperature xLS ILS or GLS
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 (1) emailing this form to 9-AWA-AVS- AIR500-Coord@faa.gov or (2) faxing it to the attention of the Aircraft Certification Service Directives Management Officer at (202) 267-3983.
Subject: AC 25.1329-1C CHG 1, Approval of Flight Guidance Systems Date: _____________________ Please check all appropriate line items:
☐ An error (procedural or typographical) has been noted in paragraph ____________ on page _______.
☐ Recommend paragraph _____________ on page __________ be changed as follows:
______________________________________________________________________ ______________________________________________________________________ ☐ In a future change to this AC, please cover the following subject:
(Briefly describe what you want added.)
______________________________________________________________________ ______________________________________________________________________ ☐ Other comments:
______________________________________________________________________ ______________________________________________________________________ ☐ I would like to discuss the above. Please contact me.
Submitted by: Date: