For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington DC 20401 

Initiated by ACE-100 

AC 23.1311-1B 

INSTALLATION OF ELECTRONIC DISPLAY 

IN PART 23 AIRPLANES 

June 14, 2005 

6/14/05 AC 23.1311-1B 

FOREWORD 

This advisory circular (AC) sets forth an acceptable means of showing compliance with Title 14 Code of 

Federal Regulations (14 CFR) part 23 for installing electronic displays in part 23 airplanes. Applicants may

follow approved alternate methods. Words such as “shall” and “must” apply only to specific rules selected 

by the applicant. 

s/ 

John Colomy

Acting Manager, Small Airplane Directorate 

Aircraft Certification Service 

i (and ii) 

6/14/05 AC 23.1311-1B 

CONTENTS 

Section Page 

1.0 PURPOSE............................................................................................................................1 

2.0 CANCELLATION...............................................................................................................1 

3.0 RELATED REGULATIONS AND DOCUMENTS...........................................................1 

4.0 BACKGROUND .................................................................................................................7 

5.0 SCOPE.................................................................................................................................8 

6.0 ACRONYMS/DEFINITIONS.............................................................................................8 

7.0 DISPLAY DESCRIPTION................................................................................................14 

8.0 FLIGHT DISPLAYS .........................................................................................................14 

9.0 POWERPLANT DISPLAYS.............................................................................................21 

10.0 ELECTRONIC DISPLAYS FOR NAVIGATION INFORMATION...............................23 

11.0 AIRPLANE FLIGHT MANUAL (AFM)..........................................................................24 

12.0 ELECTRONIC CHECKLIST............................................................................................24 

13.0 HUMAN FACTORS CONSIDERATIONS FOR DESIGN OF ELECTRONIC 

DISPLAYS ........................................................................................................................25 

14.0 LOCATION AND CONFIGURATION OF DISPLAYS .................................................28 

15.0 PILOT FIELD-OF-VIEW CONSIDERATIONS ..............................................................29 

16.0 LUMINANCE....................................................................................................................33 

17.0 SYMBOLOGY AND FORMAT.......................................................................................33 

18.0 ANNUNCIATION.............................................................................................................40 

19.0 LAG TIME AND DATA UPDATE..................................................................................41 

20.0 CONTROLS ......................................................................................................................42 

21.0 TEST FUNCTIONS...........................................................................................................42 

22.0 COLOR STANDARDIZATION.......................................................................................42 

23.0 COLOR FOR AVIATION ROUTINE WEATHER..........................................................45 

24.0 GENERAL INSTALLATION REQUIREMENTS...........................................................45 

25.0 AIRCRAFT ELECTRICAL POWER SOURCE...............................................................45 

26.0 SAFETY ASSESSMENTS................................................................................................46 

27.0 SOFTWARE AND HARDWARE DEVELOPMENT ASSURANCE .............................48 

28.0 ENVIRONMENTAL CONDITIONS................................................................................49 

29.0 ELECTROMAGNETIC PROTECTION...........................................................................50 

30.0 ELECTROMAGNETIC INTERFERENCE......................................................................50 

31.0 IMPLOSION PROTECTION............................................................................................50 

32.0 CONFIGURATION MANAGEMENT BY ELECTRONIC IDENTIFICATION 

GUIDANCE.......................................................................................................................50 

iii (and iv) 

6/14/05 AC 23.1311-1B 

1.0 PURPOSE 

This advisory circular (AC) provides an acceptable means, but not the only means, of showing 

compliance with Title 14 of the Code of Federal Regulations (14 CFR) applicable to installing 

electronic displays in part 23 airplanes. This material is neither mandatory nor regulatory in nature 

and does not constitute a regulation. You may follow an alternate FAA-approved method. 

Mandatory words such as “shall” or “must” apply only to those who seek to show compliance to a 

specific rule by use of a method prescribed in this AC without deviation. 

2.0 CANCELLATION 

AC 23.1311-1A, “Installation of Electronic Display Instrument Systems in Part 23 Airplanes,” 

dated March 12, 1999, is cancelled. 

3.0 RELATED REGULATIONS AND DOCUMENTS 

3.1 Regulatory Sections 

These acceptable means of compliance refer to the applicable sections of 14 CFR, part 23. For 

airplanes certificated under CAR 3, we show the corresponding paragraphs of the former Civil Air 

Regulations (CAR) in parenthesis. 

§ 23.771 (3.381) Pilot compartment 

§ 23.773 (3.382) Pilot compartment view 

§ 23.777 (3.384) Cockpit controls 

§ 23.1301 (3.651 and 3.652) Equipment: Function and installation 

§ 23.1303 (3.655(a)) Flight and navigation instruments 

§ 23.1305 (3.655(b)) Powerplant instruments 

§ 23.1309 Equipment, systems, and installations 

§ 23.1311 Electronic display instrument systems 

§ 23.1321 (3.661 and 3.662) Arrangement and visibility 

§ 23.1322 Warning, caution, and advisory lights 

§ 23.1323 (3.663) Airspeed indicating system

§ 23.1326 Pitot heat indication systems 

§ 23.1329 Automatic pilot system

§ 23.1331 (3.668) Instruments using a power source 

§ 23.1335 (3.669) Flight director systems 

§ 23.1337 (3.671, 3.672, 3.673, 3.674, Powerplant instruments installation 

 and 3.675) 

§ 23.1351 (3.681, 3.682, 3.685, Electrical Systems and Equipment: General 

 and 3.686) 

§ 23.1353 (3.683) Storage battery design and installation 

§ 23.1357 (3.690, 3.691, and 3.692) Circuit protective devices 

§ 23.1359 Electrical system fire protection 

§ 23.1361 (3.688) Master switch arrangement 

1 
AC 23.1311-1B 6/14/05 

§ 23.1365 (3.693) Electric cables and equipment 

§ 23.1367 (3.694 and 3.695) Switches 

§ 23.1381 (3.696 and 3.697) Instrument lights 

§ 23.1431 (3.721) Electronic equipment 

§ 23.1501 (3.735 and 3.737) Operating Limitations and Information: General 

§ 23.1523 Minimum flight crew 

§ 23.1525 (3.750) Kinds of operation 

§ 23.1529 Instructions for Continued Airworthiness 

§ 23.1541 (3.755) Markings and Placards: General 

§ 23.1543 (3.756) Instrument markings: General 

§ 23.1545 (3.757) Airspeed indicator 

§ 23.1549 (3.759) Powerplant and auxiliary power unit instruments 

§ 23.1551 (3.760) Oil quantity indicator 

§ 23.1553 (3.761) Fuel quantity indicator 

§ 23.1555 (3.762) Control markings 

§ 23.1559 (3.772) Operating limitations placard 

§ 23.1581 (3.777) Airplane Flight Manual and Approved Manual 

 Material: General 

§ 23.1583 (3.761 and 3.778) Operating limitations 

§ 23.1585 Operating procedures 

§ 91.205 Powered civil aircraft with standard category U.S. 

airworthiness certificates: Instrument and 

 equipment requirements 

§ 121.305 Flight and navigational equipment 

§ 135.149 Equipment requirements: General 

§ 135.159 Equipment requirements: Carrying passengers 

under Visual Flight Rules (VFR) at night or under 

VFR over-the-top conditions 

§ 135.163 Equipment requirements: Aircraft carrying 

passengers under Instrument Flight Rules (IFR) 

3.2 Advisory Circulars and Related Documents 

You may access the ACs, Order, and policy statement on the FAA website: www.faa.gov. You 

may obtain copies of current editions of the following publications free from the U.S. Department 

of Transportation, Subsequent Distribution Office, M-30, Ardmore East Business Center, 3341 Q 

75th Avenue, Landover, MD 20785. 

AC 20-115B RTCA, Inc., RTCA/DO-178B 

AC 20-136 Protection of Aircraft Electrical/Electronic Systems 

Against the Indirect Effects of Lightning 

AC 20-138A Airworthiness Approval of Global Navigation Satellite 

System (GNSS) Equipment 

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6/14/05 AC 23.1311-1B 

AC 20-145 Guidance for Integrated Modular Avionics (IMA) that 

Implement TSO-C153 Authorized Hardware Elements 

AC 120-64 Operational Use and Modification of Electronic Checklists 

AC 20-176A Guidelines for the Certification, Airworthiness, and 

Operational Approval of Electronic Flight Bag Computing 

Devices 

AC 21-16D RTCA Document DO-160D 

AC 23-15A Small Airplane Certification Compliance Program

AC 23-17B Systems and Equipment Guide for Certification of Part 23 

Airplanes 

AC 23-18 Installation of Terrain Awareness and Warning System

(TAWS) Approved for Part 23 Airplanes 

AC 23-23 Standardization Guide For Integrated Cockpits In Part 23 

Airplanes 

AC 23.1309-1C Equipment, Systems, and Installations in Part 23 Airplanes 

AC 25-11 Transport Category Airplane Electronic Display Systems 

AC 91-75 Attitude Indicator 

Order 8110.49 Software Approval Guidelines, dated June 3, 2003

PS-ACE100-2001-004 Guidance for Reviewing Certification Plans to Address 

Human Factors for Certification of Part 23 Small 

Airplanes 

NOTE: You may access the ACs on the FAA website: www.faa.gov. You may purchase current 

editions of the following ACs from the Superintendent of Documents, Post Office Box 371954, 

Pittsburgh, PA l5250-7954. Make check or money order payable to the Superintendent of 

Documents. 

AC 20-88A Guidelines on the Marking of Aircraft Powerplant 

 Instruments (Displays) 

AC 23-8B Flight Test Guide for Certification of Part 23 

 Airplanes 

3
AC 23.1311-1B 6/14/05 

DOT/FAA/CT-03/05 Human Factors Design Standards for Acquisition of 

Commercial Off-The-Shelf Subsystems, NonDevelopmental Items, and Developmental Systems. You 

may access this document on the FAA website: 

www.hf.faa.gov. 

DOT/FAA/OAM-TM-03-01 Multi-Function Displays A Guide for Human Factors 

 Evaluations 

DOT/FAA/AAR-95/3 FAA Aircraft Certification Human Factors and Operations 

Checklist for Standalone GPS Receivers 

ICAO 8400/5 Procedures for Air Navigation Services, ICAO 

Abbreviations and Codes. Fifth Edition-1999. 

3.3 Technical Standard Order (TSO) 

You may obtain a copy of the current edition of the following publications from the Federal 

Aviation Administration; Aircraft Certification Service; Aircraft Engineering Division; Technical 

and Administrative Support Staff Branch, AIR-103; 800 Independence Avenue, SW; Washington, 

DC 20591 or at the FAA website: at 

http://www.faa.gov/certification/aircraft/TSOA.htm

The following is a list of the FAA Technical Standard Orders (TSOs) that are only referenced in 

this AC. For a complete list of TSOs, see AC 20-110L, “Index of Aviation Technical Standards 

Orders” or the web site for the most current list. Applicants might apply for a TSO that does not 

adequately address all the functionality in the system. Alternatively, applicants may apply for 

multiple TSOs, since no single TSO applies to all functions. 

TSO-C153 Integrated Modular Avionics Hardware Elements 

TSO-C157 Aircraft Flight Information Services-Broadcast (FIS-B) Data 

Link Systems and Equipment 

3.4 Industry Documents 

You may obtain copies of current editions of the following publications as follows. These 

documents are excellent resource materials. 

3.4.1 RTCA Documents 

The following RTCA documents are available from RTCA, Inc., Suite 805, 1828 L Street NW, 

Washington, DC 20036-4001 or at their website at www.rtca.org. 

RTCA/DO-160D Environmental Conditions and Test Procedures for 

Airborne Equipment 

 4 
6/14/05 AC 23.1311-1B 

RTCA/DO-178B Software Considerations in Airborne Systems and 

Equipment Certification 

RTCA/DO-187 Minimum Operational Performance Standards for 

Airborne Area Navigation Equipment Using Multi-Sensor 

Inputs 

RTCA/DO-200A Standards for Processing Aeronautical Data 

RTCA/DO-201A Standards for Aeronautical Information 

RTCA/DO-254 Design Assurance Guidance for Airborne Electronic 

Hardware 

RTCA/DO-257A Minimum Operational Performance Standards for the 

Depiction of Navigation Information on Electronic Maps 

RTCA/DO-267A Minimum Aviation System Performance Standards 

(MASPS) for Flight Information Services-Broadcast (FISB) Data Link 

3.4.2 Society of Automotive Engineers (SAE), Inc. 

The following Society of Automotive Engineers (SAE), Inc., documents are available from SAE, 

400 Commonwealth Drive, Warrendale, PA 15096-0001 or from their website at www.sae.org. 

ARP 268G Location and Actuation of Flight Deck Controls for

Transport Aircraft 

ARP 450D Flight Deck Visual, Audible, and Tactile Signals 

ARP 571C Flight Deck Controls and Displays for Communication and 

Navigation Equipment for Transport Aircraft 

ARP 926B Fault/Failure Analysis Procedure 

ARP 1068B Flight Deck Instrumentation, Display Criteria, and

Associated Controls for Transport Aircraft 

AIR 1093A Numeral, Letter and Symbol Dimensions for Aircraft 

Instrument Displays 

ARP 1161 Crew Station Lighting—Commercial Aircraft 

5
AC 23.1311-1B 6/14/05 

ARP 1782 Photometric and Colorimetric Measurement Procedures 

for Airborne Direct View CRT Displays 

ARP 1834A Fault/Failure Analysis for Digital Systems and Equipment 

ARP 1874 Design Objectives for CRT Displays for Part 25 

(Transport) Aircraft 

ARP 4032A Human Engineering Considerations in the Application of 

Color to Electronic Aircraft Displays 

ARP 4033 Pilot System Integration 

ARP 4067 Design Objectives for CRT Displays for Part 23 Aircraft 

ARP 4101 Flight Deck Layout and Facilities 

ARP 4102 Flight Deck Panels, Controls, and Displays 

ARP 4102/7 Electronic Displays 

ARP 4103 Flight Deck Lighting for Commercial Transport Aircraft 

ARP 4105 Abbreviations and Acronyms for Use on the Flight Deck 

 

ARP 4256 Design Objectives for Liquid Crystal Displays for Part 25 

 (Transport) Aircraft 

ARP 4260 Photometric and Colorimetric Measurement Procedures 

for Airborne Flat Panel Displays 

ARP 4754 Certification Considerations for Highly Integrated or 

Complex Aircraft Systems 

ARP 4761 Guidelines and Methods for Conducting the Safety 

Assessment Process on Civil Airborne Systems and 

 Equipment 

ARP 5287 Optical Measurement Procedures for Airborne Head-Up 

Display (HUD) 

ARP 5288 Transport Category Airplane Head Up Display (HUD) 

 Systems 

ARP 5289 Electronic Aeronautical Symbols 

 6 
6/14/05 AC 23.1311-1B 

ARP 5364 Human Factor Considerations in the Design of 

Multifunction Display Systems for Civil Aircraft

 

ARP 5365 Human Interface Criteria for Cockpit Display of Traffic 

 Information 

AS 8034 Minimum Performance Standard for Airborne 

Multipurpose Electronic Displays 

AS 8055 Minimum Performance Standard for Airborne Head Up 

 Display (HUD) 

ARD 50017 Aeronautical Charting 

ARD 50062 Human Factors Issues Associated With Terrain Separation 

Assurance Display Technology 

3.4.3 Underwriter’s Laboratory (UL), Inc. 

You may obtain the Underwriter's Laboratories (UL), Inc., document listed below from Global 

Engineering Documents, 15 Inverness Way East, Englewood, CO 80112. 

UL 1418 Implosion Protected Cathode Ray Tubes for Television 

Type Appliances, Revised 1992 

3.4.4 General Aviation Manufacturers Association (GAMA) 

The following documents are available from their GAMA website at www.gama.aero/home.php. 

General Aviation Manufacturers Association (GAMA) Publication No. 10, Recommended 

Practices and Guidelines for Part 23 Cockpit/Flight Deck Design.

General Aviation Manufacturers Association (GAMA) Publication No. 12, Recommended 

Practices and Guidelines for an Integrated Cockpit/Flightdeck in a 14 CFR Part 23 

Certificated Airplane.

4.0 BACKGROUND 

Amendment 23-41, effective November 26, 1990, established airworthiness standards, in § 23.1311, 

for installing electronic display instrument systems in normal, utility, acrobatic, and commuter 

category airplanes. The first electronic displays were developed and were direct replacements for 

the conventional electromechanical components, with later designs providing more extensive 

information integration. Before Amendment 23-41, most electronic display instrument systems 

were approved by special condition for installation in part 23 airplanes. Amendment 23-49, 

effective March 11, 1996, further amended part 23, to harmonize the Federal Aviation Regulations 

7
AC 23.1311-1B 6/14/05 

with the Joint Aviation Requirements (JAR). The last revision of § 23.1311 removed redundant 

requirements and clarified which secondary instruments are required, including the visibility 

requirements for those instruments. 

5.0 SCOPE 

This AC is generally applicable only to an applicant seeking issuance of certain type certificates. 

These include a type certificate (TC), an amended type certificate (ATC), or a supplemental type 

certificate (STC) for the approval of a new type design or a change in the type design. This AC 

does not completely address Synthetic Vision Systems (SVS) or Enhanced Vision Systems (EVS), 

and Head-Up Displays (HUD). Contact the Small Airplane Directorate if there are any conflicts 

with other guidance or advisory circulars and this AC. The Small Airplane Directorate will 

coordinate and resolve the conflict. 

6.0 ACRONYMS/DEFINITIONS 

6.1 Acronyms 

AC Advisory Circular 

ACO Aircraft Certification Office 

ADC Air Data Computer 

ADI Attitude Direction Indicator 

ADDS Aviation Digital Data Service 

AFM Aircraft Flight Manual 

AFMS Aircraft Flight Manual Supplement 

AHRS Attitude Heading Reference System

ARD Aerospace Research Document 

ARP Aerospace Recommended Practice 

AS Aerospace Standard 

ASTC Amended Supplemental Type Certificate 

ATC Amended Type Certificate 

CAR Civil Air Regulations 

CFR Code of Federal Regulations 

CIP Current Icing Potential 

CRT Cathode-Ray Tubes 

EADI Electronic Attitude Direction Indicator 

EHSI Electronic Horizontal Situation Indicator 

EICAS Engine Indication and Crew Alert System

ELOS Equivalent Level of Safety 

EVS Enhanced Vision Systems 

FAA Federal Aviation Administration 

FAR Federal Aviation Regulation 

FD Flight Director 

FHA Functional Hazard Assessment 

FLS Field-Loadable Software 

FMEA Failure Modes and Effects Analysis 

 8 
6/14/05 AC 23.1311-1B 

FOV Field-Of-View 

GPS Global Positioning System

HIRF High Intensity Radiated Fields 

HUD Head-Up Display 

HSI Horizontal Situation Indicators 

ICAO International Civil Aviation Organization 

IFR Instrument Flight Rules 

ILS Instrument Landing System

IMA Integrated Modular Avionics 

IMC Instrument Meteorological Conditions 

JAR Joint Aviation Requirements 

LCD Liquid Crystal Displays 

LED Light Emitting Diodes 

METAR ICAO Routine Aviation Weather Report 

MFD Multifunction Flight Display 

ND Navigation Display 

PFD Primary Flight Display 

PFI Primary Flight Information 

POH Pilot's Operating Handbook 

RAIM Receiver Autonomous Integrity Monitoring (used with GPS) 

SAE Society of Automotive Engineers 

STC Supplemental Type Certificate 

SVS Synthetic Vision Systems 

TAS Traffic Advisory System

TAWS Terrain Awareness Warning System

TFR Temporary Flight Restrictions 

TC Type Certificate 

TCAS Traffic Alert and Collision Avoidance System

TSO Technical Standard Order 

UL Underwriter’s Laboratories 

VOR Very High Frequency Omni-Directional Range 

VFR Visual Flight Rules 

VMC Visual Meteorological Conditions 

WAAS Wide Area Augmentation System

6.2 Definitions 

This section contains definitions for terms in this document. 

Accuracy: A degree of conformance between the estimated or measured value and the true 

value. 

Adverse Operating Condition: A set of environmental or operational circumstances 

applicable to the airplane, combined with a failure or other emergency situation, that results in 

a significant increase in normal flight crew workload. 

9
AC 23.1311-1B 6/14/05 

Component: Any self-contained part, combination of parts, subassemblies, or units that 

perform a distinct function necessary to the operation of the system. 

Continued Safe Flight and Landing: This phrase means the airplane can continue controlled 

flight and landing, possibly using emergency procedures, without requiring exceptional pilot 

skill or strength. On landing, some airplane damage may occur as a result of a Failure 

Condition. 

Conventional: A system is considered “Conventional” if its function, the technological 

means to implement its function, and its intended use are all the same as, or closely similar to, 

that of previously approved systems that are commonly used. The systems that have 

established an adequate service history and the means of compliance for approval are 

generally accepted as "Conventional." 

Critical: Critical usually defines a function whose loss would prevent the continued safe 

flight and landing of the airplane. 

NOTE: The term “Critical Function” is associated with a Catastrophic Failure Condition. 

Newer documents may not refer specifically to the term “Critical Function.” 

Criticality: Indication of the hazard level associated with a function, hardware, software, 

etc., considering abnormal behavior (of this function, hardware, software, etc.) alone, in 

combination, or in combination with external events. 

Design-Eye Box: A three-dimensional volume of space surrounding the Design Eye 

Reference Point that designers and evaluators use to determine the acceptability of display and 

control locations. 

Design-Eye Reference Point: A single reference point in space selected by the designer 

where the midpoint between the pilot’s eyes is assumed to be located when the pilot is 

properly seated at the pilot’s station. 

Development Assurance: All those planned and systematic actions used to substantiate, to 

an adequate level of confidence, that errors in requirements, design, and implementation have 

been identified and corrected such that the system satisfies the applicable certification basis. 

Enhanced Vision System: An electronic means, though the use of an infrared sensor, imageintensifier, radar, or other sensor, to provide the pilot with an image of the external scene. 

Equipment Essential to Safe Operation: Equipment installed to comply with the applicable 

certification requirements of 14 CFR part 23 or operational requirements of 14 CFR parts 91 

and 135. 

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 failures. 

 10 
6/14/05 AC 23.1311-1B 

Failure Conditions: A condition affecting either the airplane or its occupants, or both, either 

direct or consequential, caused or contributed to by one or more failures or errors considering 

flight phase and relevant adverse operational or environmental conditions or external events. 

Failure Conditions may be classified according to their severity. See AC 23.1309-1C for 

more information on definitions of failure conditions. 

Field-of-View: The angular extent of the display that can be seen by either pilot with the 

pilot seated at the pilot’s station. See section 15 for more information on the field-of view. 

Fix: A generic name for a geographical position. A fix may be referred to as a fix, waypoint, 

intersection, reporting point, etc. 

Flight Plan: Refers to any sequence of fixes that are interconnected by the desired path. 

Flight plans may range from the simplest that include only the aircraft’s present position, the 

active waypoint, and the desired path between them, to more complicated plans that include 

departure and destination airports with multiple intermediate fixes. 

Function: The lowest defined level of a specific action of a system, equipment, and flight 

crew performance aboard the airplane that, by itself, provides a complete recognizable 

operational capability (for example, an airplane heading is a function). One or more systems 

may contain a specific function or one system may contain multiple functions. 

Functional Hazard Assessment: A systematic, comprehensive examination of airplane and 

system functions to identify potential Minor, Major, Hazardous, and Catastrophic Failure 

Conditions that may arise as a result of a malfunction or a failure to function. 

Hardware: An object that has physical being. Generally refers to circuit cards, power 

supplies, etc. 

Hazard: Any condition that compromises the overall safety of the airplane or that 

significantly reduces the ability of the flight crew to cope with adverse operating conditions. 

Head-Up Display: A see-through flight display presented in the pilot’s forward view of the 

outside world. 

Independent: A component, part, element, or system that is not relying on some other 

component, part, element, or system for accomplishing its function. This design concept 

ensures that the failure of one item does not cause a failure of another item. For redundancy, 

each means of accomplishing the same function need not necessarily be identical. 

Indicator: A means for displaying information of a parameter. More than one indicator 

could be depicted on one display. For example, a primary flight display may have indicators 

for attitude, altitude, airspeed, heading, and navigation. 

11
AC 23.1311-1B 6/14/05 

Instrument: Devices physically contained in one unit and devices composed of two or more 

physically separate units or components connected together. (One example is a remote 

indicating gyroscopic direction indicator that includes a magnetic sensing element, a 

gyroscopic unit, an amplifier, and an indicator connected together.) 

Map Orientation: Refers to the rule that determines the directional relation of the map to the 

upper part of the display depiction. Using a North-up rule, the North side of the map would 

be toward the top of the display and the south side of the map would be at the bottom. Using 

a desired path-up rule, the map would be oriented so the desired path would be vertical on the 

map and pointing straight up toward the top of the display. 

Map Range: The geographic extent of the map region (for example, the distance covered by 

the map representation in either the vertical or horizontal direction). 

Malfunction: Failure of a system, subsystem, unit, or part to operate in the normal or usual 

manner. A condition whereby the operation is outside specified limits. 

Multi-Function Display: An MFD is any physical display unit, other than the PFD, used to 

present various information, on which the layout may be reconfigured. 

Navigation: The process of planning, recording, and controlling the movement of an airplane 

from one place to another. 

Navigation Display: The display or suite of instruments by which navigation data is 

presented to the pilot. 

Navigation Information: Information that aids the flightcrew in determining the aircraft’s 

location in a given environment (for example, on flight plans, VORs, NDBs, features on the 

airport surface including taxiway, signage, etc). 

Primary: As used for instruments, it is defined in § 23.1311(c) as the “display of a parameter 

that is located in the instrument panel such that the pilot looks at it first when wanting to view 

that parameter.” 

Primary Flight Display: A PFD is a single physical unit that always provides the primary 

display of all the following: altitude, airspeed, aircraft heading (direction) and attitude located 

directly in front of the pilot in a fixed layout in accordance with § 23.1321. It may provide 

other information pertinent to guidance and fundamental control of flight of the airplane, such 

as critical engine parameters. 

Primary Flight Information: A PFI refers to those functions or parameters required by the 

airworthiness and operational rules, such as airspeed, altitude, attitude, and heading 

(direction), that are on the PFD. 

 12 
6/14/05 AC 23.1311-1B 

Primary Function: A function that is installed to comply with the applicable regulations for 

the required function, and one that provides the most pertinent controls or information 

instantly and directly to the pilot. 

Primary Navigation: Where the pilot looks first for a display of navigation information such 

as on an HSI or CDI. It displays vertical and lateral deviation and it may have the digital 

distance indication to/from the selected fix. 

Redundancy: The presence of more than one independent means for accomplishing a given 

function. Each means of accomplishing the function need not necessarily be identical. 

Reversionary Display: A secondary means to provide information initially presented on the 

PFD or MFD by the transfer of information to an alternate display. 

Scale: The relative proportion of the linear dimensions of objects on a display to the 

dimensions of the corresponding objects and distances being represented (for example, 1 inch 

= 100 nautical miles). 

Secondary Display: A means to provide display of information on another display. 

Standby Instrument: A dedicated instrument that is always available that presents primary 

flight information. 

Supplemental: Another function that is not required or intended to meet all the airworthiness 

and operational requirements. 

System: A combination of components, parts, and elements that is interconnected to perform

one or more functions. 

Synthetic Vision System: A system used to create a synthetic image representing the 

environment external to the airplane. An image display based entirely or partially on an 

internal database carried on the aircraft. 

Time-Critical Warning: A subset of warning. A Time-Critical Warning is the highest level 

of warning for conditions that require immediate flight crew response to maintain the 

immediate safe operation of the airplane. Examples of Time-Critical Warnings include: 

Predictive and Reactive Windshear Warnings 

Terrain Awareness Warnings (TAWS) 

TCAS Resolution Advisory 

Overspeed Warnings 

Low Energy Warnings 

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AC 23.1311-1B 6/14/05 

Track: The projection on the earth’s surface of the path of an aircraft, the direction of which 

is usually expressed in degrees from North (true, magnetic, or grid). A track is the actual 

flight path of an aircraft over the surface of the earth. 

NOTE: For more definitions related to safety assessments, refer to AC 23.1309-1C for the 

appropriate definitions. 

7.0 DISPLAY DESCRIPTION 

The following paragraphs give a brief description of an electronic display. They do not cover all 

the capabilities and details of these displays or the information presented on them. 

7.1 General 

Electronic displays have replaced many of the traditional electromechanical and analog instruments 

that provide flight and powerplant information. These displays also augment and/or combine the 

functionality of conventional systems, such as radios and navigational systems. The major display 

technologies now used are multicolor cathode-ray tubes (CRTs), liquid crystal displays (LCDs), 

electro luminescence, plasma, and light emitting diodes (LEDs). The initial electronic displays 

mimicked the traditional mechanical and electromechanical flight and powerplant instruments. 

Colors, symbols, and formats resemble these conventional instruments. 

7.2 Display Configuration

Electronic displays may be installed in several configurations. A basic electronic display may 

provide only one flight or powerplant parameter, while more sophisticated systems integrate many 

parameters on one electronic display. One of the major design goals for these systems is 

eliminating separate conventional gauges, instruments, and annunciators. Recent installations show 

a trend toward a higher degree of integration. Integration of various systems should include 

analysis to ensure that complexity and workload are compatible with general aviation pilots'

capabilities. For example, an integrated primary flight display provides several parameters such as 

attitude, heading (direction), airspeed, and altitude. For more guidance on Integrated Modular 

Avionics (IMA) that implement TSO authorized hardware elements, see TSO-C153 and AC 20-

145. 

8.0 FLIGHT DISPLAYS 

8.1 Instrument Requirements 

a. Sections 23.1303, 23.1305, 23.1311, and 23.1321, with the applicable operating rules (14 

CFR part 91, part 121, and part 135), incorporate flight and powerplant instrument requirements for 

part 23 airplanes. The navigation equipment requirements are given in operational rules specified 

in §§ 91.205, 121.303, 121.305, 121.307, 135.143, 135.149, 135.159, 135.161, and 135.165. 

Display requirements for navigation information are dependent on the navigation system installed 

in the aircraft. Instruments and equipment required for flights under part 91, part 121, and part 135 

may be affected by the electronic display installation. These instruments and equipment include 

 14 
6/14/05 AC 23.1311-1B 

gyroscopic bank and pitch, gyroscopic direction, gyroscopic rate-of-turn, slip-skid instruments, and 

other required communication and navigational equipment. 

b. There have been applications to install equipment, such as flight and navigation displays, 

as non-required. These applications request approval for these installations as Situation Awareness 

(SA) only. It is not acceptable to label an instrument as “SA-Only” and assume that its failure 

condition is acceptable. Installing compelling displays that provide Primary Flight Information 

(PFI), but do not meet the appropriate operational and airworthiness requirements, and labeling 

them as “Supplemental” or “SA-Only" is not acceptable. Section 13.6 provides more guidance. 

c. The basis for certification has been that the equipment should perform its intended 

function and not present a hazard. Instruments that aid situation awareness should be certified 

under the part 23 requirements, including § 23.1301 and § 23.1309. These displays could provide 

hazardous misleading information. PFI is essential for safe operation. An instrument that provides 

PFI should meet the minimum standards of applicable TSOs or an equivalent standard. It also 

should meet the guidance in AC 23.1309-1C, AC 23-17B, and the guidance in this AC. 

8.2 Primary Flight Information (PFI) 

Primary flight information (PFI) refers to those functions or parameters that are required by the 

airworthiness and operational rules, such as airspeed, altitude, attitude, and heading (direction). It 

may provide other information pertinent to guidance and fundamental control of flight, such as 

critical engine parameters. Attitude, airspeed, altitude, and heading (direction) are the PFI required 

in § 23.1311(a)(3) and (5), and they must be arranged according to § 23.1321 in the “basic T” 

arrangement. Direction should be heading with track displayed, if available as a selectable option. 

We recommended the horizon reference line on the PFD be at least 3.25 inches wide in straight and 

level flight for integrated displays. This recommendation is not intended to prevent replacement of 

mechanical instruments with an electronic display of a similar horizon reference line. When the 

true horizon is no longer on the display, the artificial horizon line should provide a distinctive 

demarcation between sky and ground (or the background). Display of PFI on reversionary or 

standby displays should be arranged in the basic T-configuration, but it is not required. 

8.2.1 Acceptable Methods for Compliance with Section 23.1311(b). 

There are three acceptable methods for meeting the requirements of § 23.1311(b): “The electronic 

display indicators, including their systems and installations, and considering other airplane systems, 

must be designed so that one display of information essential for continued safe flight and landing 

will remain available to the crew, without need for immediate action by any pilot for continued safe 

operation, after any single failure or probable combination of failures.” This can be accomplished 

by using dedicated standby instruments, dual PFDs, or through reversionary displays that display 

independent attitude. Electronic display systems without dedicated standby instruments should 

have at least two independent displays able to provide primary flight information to the pilot. These 

displays should be powered such that any single failure of the power generation and distribution 

systems cannot remove the display of primary flight information from both displays. 

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AC 23.1311-1B 6/14/05 

8.3 Standby Instruments 

The purpose of standby instruments or another independent PFD is to ensure that primary flight 

information is available to the pilot during all phases of flight and during system failures. 

Individual indicators should be a minimum of 2 inches in diameter or, if combined, a minimum 3 

inches displayed. 

8.3.1 Dual PFDs 

Electronic display systems with dual PFDs should incorporate dual, independently powered sensors 

that provide primary flight parameters such as Attitude Heading Reference System (AHRS) with 

comparators and dual Air Data Computer (ADC). Dual PFDs with dual AHRSs and ADCs, which 

include checking and are powered by multiple power sources and distribution systems, are 

significantly more reliable than presently certified mechanical systems. For systems with these 

characteristics, dedicated standby instruments are not required. 

8.3.2 PFD and Autopilot with an AHRS. 

For normal operation, do not use a single AHRS simultaneously to drive the PFD and the autopilot 

due to possible hazardous or catastrophic failure conditions. For a lower failure condition, a single 

AHRS with a specific configuration may be acceptable. This configuration may include a dedicated 

ADI standby instrument or independent reversionary attitude display within the primary field-ofview (FOV), self-checking AHRS or comparator with another system, and a system warning and 

caution annunciator. In emergency operations, a single AHRS driving the autopilot and PFD may 

be acceptable with a system configuration with dual AHRS and comparators, and independent 

attitude display in the primary field of view (FOV). However, the pilot must be warned of the 

incorrect comparison and be able to select the AHRS. If the displays fall outside the primary FOV, 

such deviations may need an evaluation by the certification authority. Consider AC 23.1309-1C 

guidance for these configurations. 

8.4 Reversionary Flight Displays Instead of Standby Instruments or Dual PFDs

8.4.1 General Requirements 

a. Reversionary flight displays provide a secondary means to provide PFI through alternate 

display formats on another PFD or MFD by the transfer of information to an alternate display or by 

some other means. The function of an MFD system is to provide the pilot access to various data, or 

combinations of data, used to fly the aircraft, to navigate, to communicate, and/or to manage aircraft 

systems. The MFD would also display PFI as needed to ensure continuity of operations. Part 23, 

§ 23.1311(b), states that the system “must be designed so that one display of information essential 

for continued safe flight and landing will remain available to the crew, without need for immediate 

action by any pilot for continued safe operation, after any single failure or probable combination of 

failures.” To meet the requirements of § 23.1311(b), a full-time standby display, another 

independent PFD, or an independent reversionary attitude display, must be installed. Reversionary 

modes can be automatically and manually selected or only manually selected, but it will require an 

Equivalent Level of Safety (ELOS) if the PFI is not provided by a dedicated standby instrument or 

by another PFD. 

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6/14/05 AC 23.1311-1B 

b. Only on a reversionary implementation would a project specific Equivalent Level of 

Safety approved by the Small Airplane Directorate be required. Reversionary configurations are 

significantly more reliable than presently certified mechanical systems, and the skills required 

while flying in reversionary mode are identical with those used when flying in primary mode. 

Traditional external standby flight instruments (either electronic or mechanical) offer potential 

safety problems associated with delay in pilot reaction. The pilot may delay a decision to 

transition to standby instruments and to transition to partial panel techniques, as opposed to the 

simple action the pilot would take to switch displays. A nearly identical display of all flight 

information in the same format as normally shown on the PFD provides a significant safety 

enhancement over reversion to external standby instruments. This is especially true when the size, 

location, arrangement, and information provided by the standby instruments is significantly 

different from that on the PFD. 

c. Reversionary display modes should provide consistent display formats to the PFD. The 

reversionary flight information should be presented by an independent source and display to prevent 

complete loss of PFI due to a single failure. The reversionary configuration should have two 

independent displays that incorporate dual-independently powered AHRS and dual ADC 

subsystems that provide PFIs. The reversionary system response time should provide flight critical 

information on the MFD in less than one second after a switch or an automatic operation. 

d. A reversionary configuration should have a single pilot action that would force both 

the PFD and MFD displays into reversionary mode operation. A single pilot action that results in 

display of PFI within one second or less is generally considered an equivalent level of safety. 

However, the PFI must be displayed in substantially the same format and size in the reversionary 

mode as it is in normal mode. This reversionary configuration would provide backup information 

essential to continued safe flight and landing with an intuitive control that allows instant, 

simultaneous access to reversionary mode on both the PFD and MFD displays. The single pilot 

action should be easily recognized, readily accessible, and have the control within the pilot’s 

primary field of view. An acceptable method for the single pilot action is the red color and the 

lighted red “halo” ring that announces its position on the panel. 

8.4.2 Reversionary Methods 

a. One method is to have an automatic reversionary display with a single pilot action that 

would force both the PFD and MFD displays into reversionary mode operation. If PFI on another 

display is not provided, provide automatic switching to ensure PFI is available to the pilot. 

Automatic reversion must provide a complete display of PFI on the remaining display within one 

second if a fault is detected. 

b. Most possible faults should be covered by this automatic reversionary capability. Only 

a total loss of the display may not be reliably detected automatically, but such a failure condition 

would be obvious to the pilot. Faults that result in automatic switching should be extensive 

enough to ensure PFI is available at the reliability level required by AC 23.1309-1C. If such a 

malfunction occurs, a single pilot action should provide a full display of the essential information 

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AC 23.1311-1B 6/14/05 

on the remaining display within one second. All modes, sources, frequencies, flight plan data, etc. 

would be exactly as they were on the PFD before the failure. 

c. Another method would include a means to access the reversionary mode only manually 

through a single pilot action. Manual activation of the reversionary mode on the MFD through 

single action by the pilot is acceptable when procedures to activate the PFI are accomplished before 

entering critical phases of flight. The PFI would be displayed continuously on the reversionary 

display during critical phases of flight (for example, takeoff, landing, and missed or final approach). 

8.5 Display of Attitude 

For flights under IFR conditions in part 91 and part 135 operations, and under VFR at night for part 

135 operations, attitude information is required. The loss of all attitude information or the 

presentation of misleading attitude information could result in a catastrophic failure condition 

where the pilot could not continue safe flight and landing of the airplane. 

8.6 Display of Direction (Heading or Track) 

8.6.1 General

a. The loss of direction (heading or track) information could result in reduced capability of

the pilot to cope with adverse operating conditions. The orientation of any secondary navigation 

display is optional (for example, Track-up, North-up, Heading-Up). For flights under IFR 

conditions, a stabilized heading indicator must provide the primary display of the direction 

parameter. A non-stabilized magnetic direction indicator (compass) or track may provide the 

reversionary display of direction. 

b. The heading display should provide a clear and unmistakable display of aircraft symbol 

and heading. HSI should provide a clear and unmistakable display of aircraft position, heading, and 

track (an option, if available) relative to the desired course/track. Section 17 contains more 

guidance on symbology. Direction should be heading with track displayed, if available as a 

selectable option, with the data source clearly announced. On the primary display, the heading 

scale should have a mode that presents at least 120 degrees of arc. Other display formats may be 

acceptable and have been previously approved, but they need to be evaluated for human factor 

effectiveness.

8.6.2 Hazardous Misleading Heading Information 

a. The Functional Hazard Assessment (FHA) for the failure effects of hazardous 

misleading heading information from an AHRS is clarified in AC 23-17B. This policy is 

specifically about the application of AC 23.1309-1C for an airplane with the certification basis 

under Amendments 23-41 or later. This clarification is limited to installations approved for 

operation in Instrument Meteorological Conditions (IMC) under IFR. For operations limited to 

VFR, a misleading heading indication is not considered hazardous. 

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6/14/05 AC 23.1311-1B 

b. Make an FHA, and the related safety assessments, for the specific airplane type and 

configuration since there can be many combinations of failures, various mitigating factors, and 

other functions available to a pilot. These many factors affect the criticality of the heading 

indication; therefore, use a safety assessment process from AC 23.1309-1C to classify the failure 

conditions for misleading heading information. 

c. A hazardously misleading heading is usually when the accuracy error is greater than 10 

degrees on the primary heading instrument and it is an undetected error from the AHRS. The safety 

assessment process should consider appropriate mitigating factors. 

8.7 Display of Altitude, Airspeed, and Magnetic Compass Information

The original requirements of CAR 3 were adopted and later recodified into part 23, § 23.1303, 

paragraphs (a), (b), and (c). At that time, we envisioned airspeed, altitude, and magnetic compass 

information would remain available to the pilot on the loss of the airplane's primary electrical 

power. Pneumatically driven displays provided airspeed and altitude functions. For electronic 

displays, § 23.1311(a)(3) requires the primary display of attitude, airspeed, and altitude to be 

uninhibited in any normal mode of operation. Section 23.1311(a)(5) requires an independent 

magnetic direction indicator, and either an independent secondary mechanical altimeter, airspeed 

indicator, and attitude instrument, or individual electronic display indicators for the altitude, 

airspeed, and attitude. Primary altitude or airspeed displays that require electrical power are 

acceptable if means are provided for their continued operation upon loss of the airplane’s primary 

electrical power, or if pneumatically driven instruments are available for the pilot’s use. A standby 

or reversionary integrated display of altitude, attitude, and airspeed, instead of individual electronic 

display indicators for airspeed altitude and attitude, is acceptable under one condition. The 

condition is that the standby or reversionary integrated display and the primary display are powered 

such that at least one integrated display with attitude, altitude, and airspeed is available after failure 

of any power source or distribution path. 

8.8 Accuracy of the Magnetic Heading System 

8.8.1 General 

a. The operating rules, such as part 91 and part 135, specify the minimum required 

equipment that must be installed in part 23 airplanes based on the type of operation, such as VFR or 

IFR. Part 91, § 91.205, requires for heading information, under VFR operation, a magnetic nonstabilized direction indicator (that is, compass) and, under IFR operation, a gyroscopically 

stabilized heading system. 

b. The general airworthiness requirements in part 23, § 23.1301 and § 23.1525, determine 

the flight instrument and equipment accuracy requirements for part 23 airplanes. Part 23 does not 

prescribe specific accuracy requirements for magnetic gyroscopically stabilized heading systems. 

Specific accuracy requirements for avionics may be found in the related TSO and, as acceptable 

means of compliance to § 23.1301, in ACs, notices, or policy statements/letters. 

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AC 23.1311-1B 6/14/05 

8.8.2 Magnetic Non-Stabilized Direction Indicator 

A magnetic non-stabilized direction indicator (compass) is required (reference § 23.1327) to have 

an accuracy of ±10 degrees or have a correction card, placard, or a back-up gyroscopic direction 

indicator, provided the indicator is accurate better than ±10 degrees. If the sole purpose of the 

gyroscopic direction indicator is for backing up the magnetic non-stabilized direction indicator, 

then the accuracy of displayed headings can also be to ±10 degrees. However, if a gyroscopic 

direction indicator is installed to meet the IFR operating rules, then the installation requirements are 

defined by § 23.1301. 

8.8.3 Magnetic Gyroscopically Stabilized Direction Indicator 

As installed, final accuracy for a magnetic gyroscopically stabilized direction indicator of ±4 

degrees on the ground or ±6 degrees in normal level flight on any heading would meet the 

requirements of part 23, § 23.1301. This accuracy applies after compensation. It should include 

cumulative errors in all combinations due to several things. These consist of the equipment itself,

the current flow in any item of electrical equipment and its associated wiring, the movement of any 

part (for example, controls or undercarriage), and the proximity of any item of equipment 

containing magnetic material to the direction indicators. 

8.8.4 Comparator Monitor 

a. For systems installations that include two magnetic gyroscopically stabilized heading 

systems and a comparator that monitors the differences between the headings of the two systems, 

the comparator trip point, set as follows, would meet the requirements of part 23, § 23.1301. 

• 6 degrees in stabilized level flight. 

• 6 degrees plus one half of the bank angle; or 

• 12 degrees with a bank angle greater than 6 degrees. 

• The alert function can be disabled at a bank angle greater than 20 degrees. 

• An alert is provided if the condition exceeds 60 seconds, but it allows two minutes 

for a turn error, as stated in the TSO. 

b. The 6-degree trip point during level flight allows a heading error of as much as 12 

degrees on one of the systems. This would comprise one system at the 6 degrees in-flight tolerance 

limit while the other system, presumably with some malfunction, could have an error of 12 degrees 

in the same direction before the comparator monitor alert is tripped. 

8.9 Rate-of-Turn Instrument 

a. Under §§ 91.205 and 135.159, a rate-of-turn instrument is not required if a third attitude 

instrument usable through flight attitudes of 360 degrees of pitch-and-roll is installed following the 

instrument requirements prescribed in § 121.305(j). If required, place the rate-of-turn indicator near 

the heading indicator. 

 20 
6/14/05 AC 23.1311-1B 

b. A second approved attitude indicator may substitute for the rate-of-turn instrument. AC 

91-75, Attitude Indicator, provides one method. This AC is applicable to part 23 certificated 

airplanes (or airplanes certificated under earlier equivalent regulations) that weigh less than 12,500 

pounds and are operated under part 91. The second approved attitude indicator must be powered by 

an independent power source from the primary attitude indicator. This can be accomplished by 

using independent standby instruments, another independent PFD, or independent reversionary 

attitude display. Most of the installations with electronic displays that meet the requirements of

§ 23.1311 and this AC should comply with AC 91-75. 

8.10 Slip-Skid Instrument 

The slip-skid information is required by §§ 91.205(d)(4) and 135.159(b), as applicable. We suggest 

locating the slip-skid display directly below or near the rate-of-turn instrument, if installed, or under 

or within the primary attitude display. 

8.11 Vertical Speed Indicator 

If provided, present the vertical speed indicator to the right or directly below the altitude indicator 

with a scale appropriate to the performance of the aircraft. 

9.0 POWERPLANT DISPLAYS 

9.1 General 

a. This section defines a means of presenting powerplant performance and condition 

information about the airplane's operation. It also provides guidelines about when these functions 

should be displayed to the pilot. In general, there have been two methods used to accomplish this. 

These methods include: (1) display raw engine parameters to the pilot for interpretation, or (2) 

collect powerplant data and have an automatic monitoring system interpret and report the 

powerplant condition to the pilot. Use the following evaluation criteria when considering the 

installation of electronic powerplant displays. 

b. The FAA needs to evaluate each airframe, engine, and airframe/engine interface with the 

operational characteristics of these systems to determine the primary powerplant parameter 

requirements. For this evaluation, and as used in this section, a primary powerplant parameter is 

needed to start the engine and set and monitor engine power within powerplant limitations. 

c. For multiengine airplanes, a failure or malfunction affecting the display or accuracy of 

any propulsion system parameter for one engine should not cause the loss of display or accuracy of 

any parameter for the remaining engine(s). If multiple propulsion parameters are integrated on one 

display, and the display fails, it is acceptable to provide a secondary propulsion parameter display. 

9.2 Loss of Critical Powerplant Information 

a. No single failure, malfunction, or probable combination of failures, should result in 

either the loss of critical powerplant information or an erroneous display of powerplant parameters 

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AC 23.1311-1B 6/14/05 

that would jeopardize continued safe flight and landing of the airplane. Usually, for engines that do 

not generally rely on the pilot to prevent exceeding their limits in normal operations, loss of 

powerplant displays with no more failures will not cause immediate jeopardy to continued safe

flight and landing. 

b. You may use a secondary display providing powerplant parameters for cases of loss of a 

primary powerplant display if the secondary display is located so the pilot can adequately view the 

powerplant parameters. 

c. You may use throttle or power lever position in place of lost powerplant display 

parameters. This would apply if throttle position or power lever position provides a positive 

indication of the powerplant power level required to maintain safe flight to a landing, and if it has a 

means to preclude exceeding powerplant operating limits. 

d. The FAA needs to evaluate and determine the adequacy of each proposed airframe, 

engine, and airframe/engine interface, including appropriate human factors considerations. 

Appropriate procedures for operation of an integrated electronic powerplant display system should 

be in the Airplane Flight Manual (AFM). 

9.3 Powerplant Information 

a. Display primary powerplant parameters continuously when they are required. Display 

all parameters that are primary for other engine operations continuously during these engine 

operations. When a required display parameter is not displayed full time, provide adequate 

monitoring of the function. Also, provide a manual select option for the pilot to display the 

information. A parameter defined as primary for engine start, but not for other normal engine 

operation, may only have to be displayed continuously during engine start. 

b. Before reaching or exceeding any operating limit, indicate the required powerplant 

parameters without pilot action. When any operating limit is reached or exceeded for the required 

powerplant parameter, the alerts for each phase of flight should be provided timely. Provide the 

alerts in a form that enables the flight crew to identify and carry out the necessary remedial actions. 

 Display the required powerplant information continuously during a critical takeoff and landing 

phase of flight to minimize pilot distraction until an established rate of climb or minimum altitude is 

achieved. 

c. Displays that provide multiple powerplant parameters should be such that any parameter, 

display, or alert will not suppress another display or alert that also requires immediate crew 

awareness necessary to conduct safe operation of the aircraft and engine(s). Alerts that could cause 

subsequent activation of other displays or alerts should be presented in a manner and form to ensure 

appropriate identification and prioritization of all significant hazards and required crew actions. 

9.4 Direct-Reading Alphanumeric-Only Displays 

Direct-reading alphanumeric-only displays are most valuable when integrated with an analog 

display by adding a precise, quantitative indication to compliment an analog display's qualitative 

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6/14/05 AC 23.1311-1B 

indication. Direct-reading alphanumeric powerplant displays should not be used in place of analog 

instruments to indicate values of engine parameters where trend or rate-of-change information is 

important. Direct-reading alphanumeric displays limit the flight crew's ability to assess trend 

information and result in reduced crew awareness. Direct-reading alphanumeric displays are also 

limited in their ability to provide a comparison of parameters from multiple engines or to check the 

general proximity of differing parameters against their individual limits. While these shortcomings 

can be compensated for with more design provisions, use direct-reading alphanumeric displays with 

care and evaluate each airframe, engine, and airframe/engine integration. The required § 23.1305 

powerplant instruments referred to as “indicators” should have the ability to provide trend or rateof-change information if appropriate to the specific engine parameter. If using direct-reading 

alphanumeric displays, consider the following factors. These are subject to evaluation on a caseby-case basis. 

a. The visibility and relative location of the indicated parameter should be reviewed, 

including appropriate conditions of lighting and instrument panel vibration. 

b. The ability to assess necessary trend or rate-of-change information quickly, including 

when this information may be needed during in-flight engine restarts. 

c. The ability to assess how close the indicated parameter is relative to a limit. 

d. The value to the crew of quickly and accurately comparing engine-to-engine data for 

multiengine aircraft. 

e. Compensating engine design features or characteristics that would forewarn the crew 

before the parameter reaching the operating limit (for example, redline). 

9.5 Marking of Powerplant Parameters 

Mark powerplant parameters on electronic displays following § 23.1549. AC 20-88A provides 

alternate methods of marking electronic powerplant displays. Alternate methods of marking the 

displays may be performed. However, evaluate this on a case-by-case basis depending on each 

airframe, engine, integration, and appropriate human factors considerations. 

10.0 ELECTRONIC DISPLAYS FOR NAVIGATION INFORMATION 

10.1 Guidance Information 

Navigation information used by the pilot for steering commands and to monitor deviation from a 

navigation path should be in the pilot's primary field-of-view (FOV). Other data, such as warnings 

and cautions, should also be in the primary field-of-view. For more guidance on field-of-view, see 

section 15 and Table 1 of this AC. 

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AC 23.1311-1B 6/14/05 

10.2 Display Integration 

a. Navigation guidance information may be integrated with the PFDs. Common examples 

include horizontal situation indicators (HSIs) that combine inputs from a directional gyro with a 

course deviation indicator, or a flight director (FD) integrated with the attitude direction indicator 

(ADI). Additionally, information from more than one navigation source may be displayed 

separately or simultaneously. 

b. If information from more than one navigation source can be displayed, the selected 

source should be continuously indicated to the pilot. If multiple sources can be displayed 

simultaneously, the display should indicate unambiguously what information is provided by each 

source and which is for guidance. Distinctive scales or points should differentiate between angular 

deviations (for example, Instrument Landing System (ILS), and Very High Frequency OmniDirectional Range (VOR)). Some airplanes are equipped with an autopilot and/or flight director 

coupled to the lateral and vertical guidance system. On these airplanes, the input to the autopilot 

and/or flight director should coincide with the navigation source selected on the PFD or primary 

navigational display. 

10.3 Reversionary Navigation Displays

Reversionary requirements for navigation display information depend on the rules under which the 

aircraft is operated and the hazards associated with the loss of or misleading information from the 

display. The integration of non-navigation information (for example, traffic, weather or flight 

parameters) may affect the hazards associated with the loss of, or misleading information from, the 

display. In these cases, the applicant should perform a System Safety Assessment in accordance 

with AC 23.1309-1C. For more guidance on safety assessment, see AC 23.1309-1C and section 26 

of this AC for more guidance. 

10.4 Navigation Database. 

For area navigation equipment, the navigation database is an essential component of the 

equipment. Guidelines for the navigation database can be found in RTCA/DO-200A. See AC 

20-138A for more guidance and information. 

11.0 AIRPLANE FLIGHT MANUAL (AFM) 

For equipment required for IFR approval, the AFM or supplemental AFM should contain the 

limitations and the operating and emergency procedures applicable to the equipment installed. 

Installations limited to VFR use only may require an AFM or supplemental AFM depending on the 

complexity of the installation and the need to identify necessary limitation and operating 

procedures. AC 23-8B contains more policy and guidance on AFMs. 

12.0 ELECTRONIC CHECKLIST 

A current paper backup checklist must be carried on board the aircraft and be readily accessible to 

the crew. The checklist steps in the paper backup must be equivalent to the steps in the electronic 

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6/14/05 AC 23.1311-1B 

checklist database. Policy and guidance on electronic checklist displays is contained in AC 23-8B, 

AC 120-64, and AC 20-176A. 

13.0 HUMAN FACTORS CONSIDERATIONS FOR DESIGN OF ELECTRONIC DISPLAYS 

13.1 General 

Electronic displays can be programmed to provide many innovative display flexibilities and 

features. Technology improvements in display design and integration can enhance pilot 

performance and improve situation awareness when innovations are designed using sound processes 

and appropriate design criteria that account for human performance. The applicant should ensure 

that human performance considerations are adequately addressed throughout the design process. 

Early FAA involvement and an effective working relationship between the FAA and the applicant 

will aid in the timely identification and resolution of human factors related issues. We encourage 

the applicant to develop human performance considerations, including evaluation plans, and present 

them to the FAA early in the certification process. 

13.2 Human Factors for Certification of Part 23 Small Airplanes 

Policy statement number PS-ACE100-2001-004 provides guidance to FAA certification teams. 

This guidance covers review of an applicant's Human Factor Certification Plan or the human factor 

components of a general certification plan when one is submitted as part of a TC, STC, or ATC 

project. FAA certification teams are encouraged to use this policy in reviewing certification plans. 

The application of this guidance will ensure that human factors issues are adequately considered 

and addressed throughout the certification program. 

13.3 Cockpit/Flight Deck Design, GAMA Publication No. 10 

The purpose of this document is to provide manufacturers of small aircraft and systems with human 

factors recommendations for the design of cockpits/flight decks and their associated equipment. 

This publication was developed as a cooperative effort between the FAA and industry.

13.4 SAEs and RTCAs Recommended Practices and Standards 

Evaluation of the electronic display system should consider airworthiness regulations, 

recommended practices, and standards from industry documents as listed in section 3 of this AC. 

13.5 Human Factors Compliance Considerations 

a. The applicant should identify all human factors related regulations that apply to the 

installation and operation of the display system or component being certified. The applicant should 

document how the system or component complies with each of these regulations. A partial list of 

relevant regulations is contained in policy statement PS-ACE100-2001-004. The FAA and the 

applicant should develop and agree on a plan to describe how the applicant intends to show 

compliance with the relevant regulations. It should contain enough detail to assure that human 

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AC 23.1311-1B 6/14/05 

factors compliance considerations have been adequately addressed. The test plan should also allow 

for enough time to accomplish all necessary testing agreed to by the applicant and the FAA. 

b. Address the areas listed below to assure the following. 

(1) The intended use of the system does not require any exceptional skill or generate 

any unreasonable workload for the pilot. 

(2) The use of the display does not require unreasonable training requirements to 

adequately show that the pilot can understand and properly operate the system in all operational 

environments. 

(3) The design characteristics of the display system should support error avoidance 

and management (detection, recovery, etc.) equivalent to or less than a previously certified 

comparable system. 

(4) The display system is integrated and is consistent or compatible with other cockpit 

controls and displays, and it creates no more burden on the pilot regarding the new display system

or operation of other systems. 

(5) If a failure occurs, it does not prevent the pilot from safely operating the airplane. 

(6) The manufacturers should provide design rationale for their decisions regarding 

new or unique features in a display. Evaluation pilots should verify that the data support a 

conclusion that any new or unique features have no unsafe or misleading design characteristics. 

(7) Several pilots and human factors representatives should conduct display 

evaluations. Include those pilots who are most representative of the intended user of the system. 

For systems that contain new or unique features, a greater number of evaluators should be 

considered. Allow a reasonable amount of training time to learn all required features of the display 

system. The evaluators should be familiar with the guidance contained in this advisory circular 

before the evaluation. Evaluators should be familiar with display guidance contained in the human 

factors policy statement referenced above, GAMA Publication No. 10, and the Multi-Function 

Displays, A Guide for Human Factors Evaluations. 

13.6 Intended Function 

One of the regulations applicable to displays is § 23.1301. As part of showing compliance with 

§ 23.1301, the display system must be of a type and design appropriate to their intended function 

when used by representative general aviation pilots. An AFM, AFMS or Pilot’s Guide may be used 

to describe the intended function.

13.6.1 Demonstrate Compliance 

To show compliance with § 23.1301, an applicant must show that the design is appropriate for its 

intended function. The applicant’s statement of intended function should be specific and detailed 

enough for the certification authority to evaluate the intended function(s) and to evaluate whether 

the associated pilot tasks (if any) can be adequately achieved. This is important for systems with a 

pilot interface component, as the certification authority should evaluate the intended function from

the pilot’s perspective as well as from a systems perspective. There are several safety concerns, 

including the concern that the pilot could rely on a display that does not meet minimum safety 

standards. For example, elaborate on a statement that a new display system is intended to “enhance 

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6/14/05 AC 23.1311-1B 

situation awareness” since a wide variety of different displays from terrain awareness, vertical 

profile, and even the primary flight displays, enhance situation awareness in different ways. 

Provide a greater level of detail to identify the specific aspect(s) of situation awareness that are to 

be enhanced and show how the design supports those aspects. Similarly, the terms “supplemental,” 

“non-essential,” “secondary,” etc., in isolation would not be acceptable as statements of intended 

function. While the statement of intended function must be submitted by the applicant, the 

certification authority will make the final determination of compliance to the rule, specifically on 

the acceptability of the proposed intended function. 

13.6.2 Intended Function(s) and Associated Task(s) 

a. List the intended function(s) and associated task(s) for the system, as well as for 

individual features or functions of that system. A system may have multiple intended functions, 

provided each function is documented and all information depicted or indicated to the flight crew 

supports one or more of the documented intended functions. 

b. You may use the following information to evaluate whether the statement of intended 

function and associated task is sufficiently specific and detailed. 

(1) Does each feature and function include a statement of the intended function? Is 

there a description of the task associated with this feature/function? 

(2) What assessments, decisions, or actions are required from the pilot for these 

intended functions? 

(3) What other information is required for use with these intended functions (for 

example, other cockpit systems), assumed to be used in combination with the system?

(4) Is the operational environment in which these intended functions are to be used 

adequately described (for example, VFR, IFR, phase of flight, etc.)?

13.6.3 Method(s) of Compliance 

The method(s) of compliance should be adequate to enable the certification authority to determine 

the following. 

a. Is the system providing sufficient and appropriate information to support the intended 

functions and to achieve the associated tasks?

b. Is the level of detail, accuracy, integrity, reliability, timeliness, and update rate of the 

information matched appropriately to the task associated with the intended function?

c. Does the use of the system impair the pilot’s ability to use other systems or do other 

tasks?

27
AC 23.1311-1B 6/14/05 

d. Does the system or the use of the system impair the safe operation or the intended 

function of other systems or equipment?

13.6.4 Labeling 

All displays and controls whose function is not obvious should be labeled and identified by function 

or operating limitations or any combination. The assumptions and/or limitations should be 

adequately documented in the AFM, AFM Supplement, and/or Pilot Operating Manual (as 

negotiated with the ACO). This applies to the manufacturer of the equipment and not to the 

installer. The installer is required to verify the intended function and to make any placards or flight 

manual limitations, according to subpart G of part 23, that the installed equipment makes necessary. 

14.0 LOCATION AND CONFIGURATION OF DISPLAYS 

14.1 Display Usability

Locate the displays so the pilot(s) can monitor them with minimal head and eye movement between 

displays. Flight information should be legible, accurate, easily interpreted, sufficiently free of 

visual cutoff (viewing angle), parallax and distortion, for the pilot to correctly interpret it. 

14.2 Basic T Configuration 

Use the basic T-configuration for airplanes certificated under § 23.1321, Amendment 23-14, or a 

later amendment. The basic T-configuration is defined as an arrangement where the airspeed and 

altitude data are centered, respectively, directly to the left and right of the attitude data, with the 

direction data located directly below the attitude data. 

14.3 Deviations from the Basic T Configuration 

a. Deviations from the basic T-configuration have been approved for individual instrument 

arrangements if the droop angle (angle below the § 23.1321(d) position) is 15 degrees or less, or if 

the elevated angle is 10 degrees or less. These angles are measured from a horizontal reference line 

that passes through the center of the attitude reference data with lines passing through the center of 

the airspeed and altitude data. 

b. Unique displays or arrangements for attitude, altitude, airspeed, and navigation data, 

integration of combinations of these functions, or rearrangement of them from the basic Tconfiguration, may be approved when an equivalent safety finding, and a human factors evaluation 

is provided. This evaluation should consider the different types of airplane operations, as defined 

by § 23.1559(b). Coordination with the Small Airplane Directorate is required. Deviations beyond 

these limits may be approved for individual flight instruments through a human factors evaluation 

and display installation evaluation, considering the following items. 

(1) The display arrangement and its alignment to the normal line of the pilot's vision 

(2) The cockpit view 

(3) The integration of other functions within the displays 

 28 
6/14/05 AC 23.1311-1B 

(4) The data presented, format, symbology, etc., within the display 

(5) The ease of manipulating controls associated with the displays 

15.0 PILOT FIELD-OF-VIEW CONSIDERATIONS 

15.1 General 

a. This guidance is specifically intended to address the visibility and placement of 

information used by the pilot. Past practice has typically involved FAA flight test pilots working 

with applicants to conduct qualitative assessments of the proposed equipment locations. This is 

intended primarily for new aircraft development programs, but it could also be used for extensive 

modifications to existing cockpits. Part 23 rules do not require the applicant to establish a cockpit 

design eye reference point from which to measure viewing distances and angular displacement to 

various cockpit equipments. However, we recommend you facilitate quantitative assessments of 

equipment locations for new instrument panel designs. These evaluations typically involve the 

pilot’s subjective assessment of the applicant’s cockpit to ensure it meets the intent of § 23.1321(a), 

which states the pilot should be able to use all the required instruments with “minimum head and 

eye movement.” These assessments have worked for previous certification efforts; however, more 

information is available that may be helpful when conducting more quantitative assessments and 

when providing a more standardized evaluation for the benefit of the applicant and the FAA 

certification team. 

b. Many other factors need to be considered when determining the acceptability of 

displayed information in the cockpit. These factors can include the following: 

Readability 

Clutter 

Pilot scan pattern 

Pilot workload 

Parallax 

Frequency of use and criticality 

 

15.2 Primary Field-of-View 

Primary optimum field-of-view is based on the vertical and horizontal visual fields from the design 

eye reference point that can be accommodated with eye rotation only. With the normal line-of-sight 

established at 15 degrees below the horizontal plane, the values for the vertical and horizontal 

(relative to normal line-of-sight forward of the aircraft) are +/-15 degrees, as shown in Figure 1. 

This area is normally reserved for primary flight information and high priority alerts. Table 1 also 

provides examples of information recommended for inclusion in this visual field. In most 

applications, critical information that is considered to be essential for safe flight, with warning or 

cautionary information that requires immediate pilot action or awareness, should be placed in the 

primary field-of-view. 

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AC 23.1311-1B 6/14/05 

15.3 Primary Maximum Field-of-View

Primary maximum field-of-view is based on the vertical and horizontal visual fields from the design 

eye reference point that can be accommodated with eye rotation and minimal head rotation. These 

values are +/-35 degrees horizontal, and +40 degrees up and -20 degrees down vertical, as shown in 

Figure 1. These areas are normally used for important and frequently used information. Pilot’s 

visual scan and head rotation is minimized when information is placed in this area. Placement of 

information in this area also reduces the potential for spatial disorientation. Table 1 provides 

examples of information recommended for inclusion in this visual field. 

 30 
AC 23.1311-1B 

Figure 1. Primary Field-of-View

15.4 Recommended Location for Displaying Information 

Table 1 contains the recommended location for displaying information intended for new panel 

layout with integrated electronic displays; however, these guidelines should be followed for other 

installations as practicable. Deviations beyond these limits may be approved for individual flight 

instruments depending on the combination of factors listed in section 15.1. These deviations need a 

display installation evaluation. It may not be practicable for retrofit installations with new 

electronic displays, such as with ATC, STC, and field approvals, to comply with the values in the 

table. This is due to limitations in the systems and incompatible technologies between the aircraft 

and the system being added. In such cases, for any given item, the angular deviations should not 

increase from what was originally found to be acceptable, and the display characteristics should be 

at least as good as the original display. For retrofit installations, it may be acceptable for 

installations to fall outside the recommended data in Table 1. These deviations may need an 

evaluation by the certification authority. Factors to consider during this evaluation include the 

distinguish ability, attention-getting quality, readability, etc. The field-of-view angles should be 

applied for installation approvals where a design eye reference point exists. For installation 

approvals where no design eye reference point is defined, the linear panel distances from center in 

Table 1 should be used. 

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AC 23.1311-1B 6/14/05 

Table 1 – Field-of-View

Data Recommended Field-of-View 

FOV, Deg from

Pilot View 

Centerline 

(NOTE 1) 

Approx. Distance 

(inches) From

Reference Center 

Line 

(NOTE 1) 

PFI – Basic T – Electronic or Mechanical 4 (NOTE 2) 2 (NOTE 2) 

Navigation Course Error Data (HSI, 

CDI, FD) 

15 8

Autopilot and /Flight Director Modes 15 8 

Navigation Source Annunciation 15 (NOTE 3) 8 (NOTE 3) 

System Warnings and CautionsIncluding failure annunciation 15 (NOTE 4) 8 (NOTE 4) 

Required Powerplant 35 21 

Advisories Annunciations 35 21 

Standby Instruments 35 (NOTE 5) 21 (NOTE 5) 

Reversionary Display for PFI 35 21 

Electronic Map Display that is not used 

to replace the CDI/HSI/FD 

35 (NOTE 6) 21 (NOTE 6) 

NOTE 1. The FOV angles and Approximate Distance from Center Reference Line, based on 

a viewing distance of 30 inches from the panel, are defined as acceptable angles and 

distance to each data source from the center of basic T, or pilot view centerline. Distances 

are measured center-to-center of the display in question, measured horizontally. Vertical 

placement in the panel can be from just below the basic T to the glare shield. 

NOTE 2. Display PFI as close to the center of reference as possible. 

NOTE 3. The navigation source annunciation should be on or near the affected display and 

should appear on the same side of the basic T as the affected display. The guidelines for the 

proximity to the affected display depend on the size, color, and distinguishing characteristics 

of the source annunciation. 

NOTE 4. Warnings and cautions can be presented within 35 degrees if they are associated 

with a unique aural tone or a master warning/caution light that is within 15 degrees. The 

warnings and cautions should be in a consistent location, such as on an annunciator panel. 

If an aural tone is used, it should be readily distinguishable from all other cockpit sounds 

and provide unambiguous information to direct the pilot’s attention to a visual indication of 

the condition. Consider the number of aural alerts. 

NOTE 5. Install the standby instruments as close as practicable to the PFI. 

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6/14/05 AC 23.1311-1B 

NOTE 6. If a map display is used for primary navigation, such as for the CDI, HSI, or flight 

director, then it should meet the 15-degree FOV requirement identified for the steering 

command. 

16.0 LUMINANCE 

16.1 Visual Performance 

All displayed information such as symbols, graphics, and alphanumeric characters should be clearly 

differentiated from one another and legible under all ambient illumination conditions. SAE 

documents Aerospace Standard (AS) 8034, and ARPs 1668B, 4067, and 4256 may be used as 

guidelines for evaluating the visual performance parameters of the electronic displays relative to 

viewing, photo colorimetric, luminance characteristics, etc. These conditions range from the night 

environment to direct sunlight through any window with the operational brightness at the luminance 

expected at the display’s useful end-of-life state. The end-of-life luminance level represents the 

expected value of the display brightness or minimum acceptable output that is established by the 

manufacturer. The display luminance should sufficiently provide a comfortable level of viewing 

with rapid adaptation when transitioning from looking outside the cockpit. 

16.2 Luminance Level 

The luminance level of some displays will gradually diminish over the life of the unit. As part of

the continued airworthiness requirements of § 23.1529, consider establishing an operational inflight evaluation or maintenance evaluation to determine the minimum luminance level appropriate 

for the type of display, flight deck location, method of format, symbology, color used, etc. 

Although automatic luminance control compensation is not required, incorporating such a system

may decrease pilot workload. Regardless of whether an automatic luminance control is 

incorporated, provide a manual luminance control that is not adversely affected by failure of any 

automatic luminance control. Luminance control should not result in some information 

disappearing while other information remains visible. 

17.0 SYMBOLOGY AND FORMAT

17.1 Symbol Attributes 

To minimize confusion or misinterpretation, symbols should be easy to discern, consistent within 

the cockpit, and learned with minimal training. Symbols should not have shapes, colors, or other 

attributes that are ambiguous or could be confused with the meaning of similar symbols. Electronic 

displays in the cockpit should use symbology consistent with their intended function. Clearly 

define and appropriately classify the function of symbology for the pilot. Symbols representing the 

same functions on more than one display should be the same. Different symbols among different 

displays for the same functions may be acceptable only if it can be clearly shown that the pilot can 

quickly and consistently recognize, interpret, and respond correctly without incurring excessive 

pilot workload. For example, to indicate bank angle on the attitude displays in the cockpit, the type 

of pointer, ground (fix) or sky (moveable), should be similar for ease of interpretation and to 

minimize confusion. 

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AC 23.1311-1B 6/14/05 

17.2 Symbol Standards 

Symbols should be based on established industry standards (for example, SAE ARP 4102/7 and 

ARP 5289 for electronic displays). For example, the use of flashing letters, such as an “X,” should 

be consistent. Flashing, when used, should not be a caution for one parameter, and a warning for 

another. One benefit of symbol standards versus other information formats is the compact encoding 

of information, which minimizes clutter. However, the symbolic encoding of information should 

remain simple enough for pilots to learn and recall. 

17.3 Clutter 

Powerful formats are possible with an electronic display system, but excessive information on a 

limited display size can result in clutter and reduce the efficiency of the pilot cues. The density of 

information on the display should be compatible with the pilot's ability to recognize essential 

information and to minimize misinterpretation. Symbols and markings that are displayed during 

specific phases of flight may be removed at other times to reduce clutter. Establish an information 

prioritization scheme to ensure the clear presentation of essential information. Clutter should be a 

major consideration during the reversionary or compacted modes. When combining essential 

information on a display after another display or unit fails, the display format should not be 

confusing and the information should still be usable, including unusual attitude. If clutter is 

anticipated, provide a means to manually remove the clutter (decluttering). Automatic decluttering, 

such as during specific phases of flight, or during certain alerts, may also be appropriate. 

17.4 Unusual Attitude and Automatic De-clutter of the PFD 

a. All primary attitude displays should provide an immediately discernable attitude 

recognition capability that fosters a safe and effective unusual attitude recovery capability. The 

display should provide sufficient cues to enable the pilot to maintain full-time attitude awareness 

and to minimize potential for spatial disorientation. The display should support the initiation of 

recovery from unusual attitudes within 1 second with a minimum correct response rate of 95 

percent. Additional information included on primary flight reference display(s) should not interfere 

with maintaining attitude awareness, recovering from an unusual attitude, or the interpretation of 

any primary flight information. 

b. The PFD may require an automatic de-clutter function during unusual attitudes. 

Unusual attitudes generally exceed 70 degrees of bank or +/-30 degrees of pitch, but may vary with 

airplane performance. (NOTE: Not applicable to aerobatic category airplanes). The approved 

configuration (whether basic-T configuration or a new configuration) should be preserved. Basic 

navigation information on the primary navigation display does not need to be decluttered. 

17.5 Direct-Reading Alphanumeric-Only Display of Airspeed and Altitude 

Direct-Reading presentation of airspeed and altitude should convey to the pilot a quick-glance sense 

of rate and trend information. For airspeed and altitude, direct-reading alphanumeric displays may 

not be adequate on the primary display or on the standby instruments, but it is acceptable on a 

 34 
6/14/05 AC 23.1311-1B 

display used as supplementary information. If the applicant proposes a direct-reading alphanumeric 

display, they should show that the pilot response is equal to or better than the response with analog 

data (symbology) using a human factors evaluation. 

17.6 Round Dial and Moving Scale Display

The display of a round dial, moving pointer with a digital readout is acceptable. To accommodate a 

larger operating range on a linear tape, adopt a moving scale display with the present value on a 

digital readout. Since the moving scale display typically does not provide any inherent visual cue 

of the relationship of present value to low or high airspeed limits, quick-glance awareness cues may 

be needed. 

17.7 Low-Speed And High-Speed Awareness Cues 

a. Airspeed displays with fixed pointers and moving scales should provide appropriate 

low-speed and high-speed awareness cues. Conventional mechanical airspeed indicators for part 23 

airplanes include simple green and white speed arcs that, when combined with a moving pointer, 

provides pilots with adequate low-speed awareness. Airspeed displays incorporating fixed pointers 

and moving scales require more cues than conventional indicators to compensate for their 

deficiencies. For part 23 airplanes, prominent green and white arcs provide the pilot with speed 

cues but not enough to be considered equivalent. Therefore, low-speed awareness cues are 

necessary for part 23 airplanes. 

b. The low-speed awareness cues should include a red arc starting at VSO and extending 

down toward zero airspeed. During takeoff, the red arc indication of low speed should not be 

displayed. The applicant may choose an optional yellow band from VS1 down to VSO. The 

applicant may choose a single conservative stall speed value to account for various weight and flap 

configurations (reference § 23.1545(a)(4)). For most part 23 airplanes, a fixed value at gross 

weight and full flaps is acceptable since this has been an adequate safety standard for mechanical 

gauges. Incorporate a red arc or red barber pole extending from VNE or VMO upward to the end of 

the airspeed tape. 

NOTE: The red arc below the stall speed is intended for low speed awareness only and is not 

intended to limit flight operation. 

17.7.1 VNE Airplanes 

The applicant must show compliance with §§ 23.1311(a)(6) and 23.1545 (paragraphs (a) through 

(d)), and incorporate the following speed awareness cues for VNE airplanes, as shown in Figure 2. 

a. Incorporate red band from VSO to 0 (or minimum number). 

b. Incorporate red band from VNE to the top of the airspeed tape. 

c. Yellow band is optional in the low speed range from VSO to VS1. We discourage use of 

the yellow band (due to clutter) for twin-engine airplanes that incorporate a red and blue line, in 

accordance with § 23.1545, for one-engine-inoperative speeds. 

35
AC 23.1311-1B 6/14/05 

Red 

VNE

Yellow 

VNO

Green 

VFE

VS1

Blank or optional yellow 

arc 

VSO

Red 

Figure 2. Low-Speed and High Speed Awareness for VNE Airplanes 

 36 
6/14/05 AC 23.1311-1B 

17.7.2 VMO Airplanes 

The applicant must show compliance with §§ 23.1311(a)(6) and 23.1545 (paragraphs (a) through 

(d)), and incorporate the following speed awareness cues for VMO airplanes, as shown in Figure 3. 

• Incorporate red band from VSO to 0 (or minimum number). 

• Incorporate red band from VMO to the top of the airspeed tape. 

• The green arc for normal operations is not required, but it may be used if previously 

approved. 

• The yellow band is optional in the low speed range from VSO to VS1. 

Red 

Black 

Red 

VSO

VS1

This is a blank 

area 

represented by 

a black arc. 

Note: On commuter category

Airplanes, bugs should be 

provided for Setting V1 and 

V2

Blank or optional 

yellow arc 

VMO

VFE

Figure 3. Low-Speed and High Speed Awareness for VMO Airplanes 

37
AC 23.1311-1B 6/14/05 

17.7.3 Primary Flight Display 

a. Low-speed awareness is an important PFD display function. Stalls remain in the top 

five causes of fatal accidents for all types of part 23 airplanes, so it makes sense to use the expanded 

display capability of new part 23 electronic PFDs to address low-speed awareness more effectively. 

b. Historically, with traditional round dial instruments there was no ability to put color arcs 

on the airspeed indicator. Newer part 23 airplanes are required to also have a stall warning that 

sounds at 5-10 percent above stall. This was the best that could be afforded with existing 

technology. Unfortunately, most stalls occur in VMC and the pilot probably is not looking at the 

airspeed indicator when the airplane is slowing to a stall. 

c. With electronic displays, designers are not constrained to simply reproducing the old 

round-dial type displays. The displays can have features that were not possible on conventional 

instruments. Applicants should consider using the display capabilities to catch the pilot’s attention 

away from looking out the window or fixating on flight or navigation displays such as the flight 

director or HSI. One example the applicants might consider is flashing a large red “STALL” in the 

center of the PFD and MFD. These should be large enough to catch the pilot’s attention using 

peripheral vision. Another example is to display an angle-of-attack (AOA), or AOA-like display, 

above the airplane symbol (or equivalent) essentially showing the stall margin. Pilots prefer an 

AOA scheme so they can see their stall margin diminishing and take corrective action based on a 

trend. 

17.8 Linear Tape Altimeter Displays

a. Linear tape altimeter displays should include enhancements denoting standard 500- and 

1,000-foot increments. These displays should convey unambiguously, at a glance, the present 

altitude. Combining altimeter scale length and markings, therefore, should be enough to allow 

sufficient resolution for precise manual altitude tracking in level flight. They should also have 

enough scale length and markings to reinforce the pilot’s sense of altitude. The scale length should 

also allow sufficient look-ahead room to adequately predict and accomplish level off. Pilot 

evaluations have shown that, in addition to the appropriate altitude markings commensurate with 

aircraft performance, an altitude reference bug is recommended to provide acceptable cues. 

b. Display a trend indicator unless a VS1 is located adjacent and to the right of the altimeter. 

 A six-second altitude-trend indicator is typical, but other trend values may be more appropriate 

depending on the airplane performance and altitude tape scaling. 

17.9 Standardization Guide for Integrated Cockpits in Part 23 Airplanes 

This AC is to acknowledge the General Aviation Manufacturers Association (GAMA) Publication 

No. 12, “Recommended Practices and Guidelines for an Integrated Flightdeck/Cockpit in a 14 CFR 

Part 23 (or equivalent) Certificated Airplane,” as an acceptable means for showing compliance with 

applicable requirements for electronic displays in part 23 airplanes. AC 23-23, or GAMA 

Publication No. 12, and this AC should not conflict with each other. GAMA Publication No. 12 

 38 
6/14/05 AC 23.1311-1B 

provides more specifics in certain areas for standardization for pilot transitions from various 

cockpits. These specifics are acceptable, but they do not cover all the issues for the installation of 

electronic displays. One significant benefit of AC 23-23 to standardization between cockpit designs 

is that it should improve pilot performance (that is, reduce pilot errors, tasks performance times, 

etc.) when transitioning between different aircraft systems. 

17.10 Alternative Formats 

Alternative formats or arrangements to those described above should have an adequate human 

factors evaluation completed to show that pilot response is timely and accurate to at least the level 

of the existing conventional displays. Human factors criteria should be defined as part of the design 

process. Because displays are a function of the specific cockpit layout and configuration, human 

factors evidence needs to be provided during certification. Specific human factors evaluations and 

studies that have been performed may support the configuration of displays and their location in the 

cockpit. Validating these evaluations/studies on each airplane during the installation process of the 

certification is an alternative. 

17.11 Integration of Display Parameters 

Integration of several display parameters into one common display provides distinct benefits, but it 

raises some certification issues. New approaches presenting data and commands to the pilot are 

encouraged. To overcome the issues that may occur as a result of this integration, present the data 

and commands in a simple format to alleviate any increase in pilot workload. The overall goal is to 

meet or exceed the existing cockpit performance levels currently in operational use while 

maintaining pilot workload at acceptable levels. 

17.12 Overlays

a. If overlays are provided, the display format should allow the pilot to overlay weather or 

other graphics relevant to the flight path on one display without ambiguity. Each new graphic 

should be evaluated both individually and with allowed combinations of other weather, terrain, and 

navigation symbology to guard against confusing the pilot or cluttering the screen. When 

overlaying two or more functions, using the same or similar color to convey different information is 

not recommended. If the same or similar colors are required, then retain the meaning of the 

different information. Patterning, bordering, or blanking may be used to clearly depict the different 

sets of data. 

b. If overlays are presented, the data should be presented in an airplane heading 

orientation. The orientation of any secondary navigation display is optional (for example, Trackup, North-up, Heads-Up). All overlay data shall be the same map orientation and scale as the 

display it is placed on. For more information, see RTCA/DO-257A. The orientation on any 

navigation display should not change when an overlay is added, unless required by TSO guidance. 

A thumbnail display is not considered an overlay. 

c. The ability to perform overlays is one of the greatest strengths of an electronic display, 

but it also creates the potential to produce cluttered or misleading information. Therefore, the 

39
AC 23.1311-1B 6/14/05 

number of overlays shall not cause the information displayed to become unusable through cluttering 

or obscuration. Combinations of multiple data presentations shall not cause conflicting 

interpretation of the symbology or icons. 

17.13 Scaling 

Symbol attributes that use scaling and dynamics should be appropriate for the performance level of 

the airplane. Conflicting range scaling shall not occur. Provide map range. Always display the 

range scale for the primary navigation display in the same location on that manufacturer’s product. 

18.0 ANNUNCIATION 

18.1 General 

The electronic display system should provide the pilot with visibly discernible annunciators that 

will indicate the system operating modes. The visual annunciators should be distinctive under all 

normal lighting conditions and consistent with cockpit warnings. Under night lighting with the 

display average brightness at the lowest usable level for prolonged flight, visual annunciators 

should be usable. Consistently locate annunciations in a specific area of the electronic display to 

ensure proper interpretation by the pilot. Except for a flight director display, using the display 

selection control position as annunciation is acceptable only under certain conditions. Those 

conditions include when the control position is in direct view of the pilot, without head movement, 

and when the control position is obvious under all lighting conditions. When a failure occurs or 

when using reversionary modes, an annunciation of abnormal system status shall be provided, in 

accordance with § 23.1311(a)(7). The display should not provide hazardously misleading 

information. Evaluate annunciations that require flight crew action to determine if the required 

actions could be accomplished in a timely manner without exceptional pilot skill. A failure of any 

PFI sensor input to the PFD should be appropriately annunciated on the PFD. 

18.2 Multiple System Configurations 

Where multiple system configurations and more than one sensor input are available for source 

selection, the switching configuration by annunciation or by selector switch position should be 

readily visible, readable, and should not be hazardously misleading to the pilot using the system. 

Labels for mode and source selection annunciators should be compatible throughout the cockpit. 

To ensure the flight crew can properly interpret the system status, cautionary annunciation methods 

should be consistent when numerous interface-switching configurations are possible. 

18.3 Alerting Messages 

Alerting messages should differentiate between normal and abnormal indications. Abnormal 

indications should be clear and unmistakable, using techniques such as different shapes, sizes, 

colors, flashing, boxing, outlining, etc. Provide individual alerts for each function essential for safe 

operation. 

 40 
6/14/05 AC 23.1311-1B 

18.4 Visual Crew Alerting and Display Prioritization 

Due to the ability to display information from several sources on an integrated display, a 

prioritization scheme ensures the continuous availability of essential information to the flight crew. 

 Prioritization of time critical alerts such as TAWS, Predictive Windshear System (PWS), Traffic 

Alert and Collision Avoidance (TCAS), and Reactive Windshear System (RWS) have been 

established for small airplane applications and are shown in AC 23-18. Crew alerting information 

systems require appropriate prioritization of warning, caution, or advisory information. This 

prioritization includes both visual and aural alerts. Layering the new information over an existing 

moving map display or an existing weather display, as a result of an automatic pop-up capability, is 

a common technique. Annunciation of any system level warning, caution, and advisory alert should 

be compatible with the time critical alert schematic. Prioritize systems information displayed on the 

MFD to allow ready access to critical information. Less critical information may be less 

accessible. Provide a means for the flight crew to select higher priority information as needed with 

a single entry on the MFD control panel or keypad. 

18.5 Visual Alerts for Time Critical Warnings 

Visual alerts for time critical warnings that require immediate pilot action should be annunciated 

with an aural warning. Terrain, traffic, and weather are typically displayed in a layered format on 

the Navigational Display (ND), although weather and terrain cannot be displayed at the same time 

in many current designs. A time critical threat should trigger an automatic pop-up and the 

appropriate display on the ND, as well as the appropriate aural alert. Subsequent time critical alerts 

of a higher priority may override the visual display, but they should override the previous aural 

alert. Other MFD functions, such as checklists, synoptic and expanded systems information, should 

only be shown when selected by the crew or displayed by phase of flight. 

18.6 Supplementary Monitoring of System Status through Independent Sensors 

Electronic displays may present system parameters, such as engine instruments, that can serve as 

supplementary information to the certified aircraft systems. This information may use sensors that 

are completely independent from the originally approved sensors. When supplementary 

information is presented using independent sensors, the presentation cannot interfere or conflict 

with the primary information. Clearly annunciate and/or display any exceedance to the pilot in the 

appropriate color, in accordance with §§ 23.1322 and 23.1549. The Airplane Flight Manual 

Supplement (AFMS) and/or the Pilot Operating Handbook must clearly identify the relationship 

and procedures associated with those annunciations. 

19.0 LAG TIME AND DATA UPDATE 

a. The display of information essential to the safety of flight should be thoroughly 

responsive and accurate to the operational requirements. Electronic display system delay effects of 

essential information, including attitude, airspeed, altitude, heading, and specific propulsion 

parameters, should not degrade the pilot's ability to control the airplane. Any lag introduced by the 

display system should be consistent with the airplane control task associated with that parameter. 

41
AC 23.1311-1B 6/14/05 

Update rates of data on displays should be fast enough so that required symbol motion is free from

objectionable lag or stepping. 

b. SAE ARPs provide recommended lag times for display of the format and primary flight 

data, and minimum rates for data updates, to meet symbol motion. A 50-60 Hz refresh rate is 

typically enough to remove traces of visible flicker on the display. Frequencies above 55 Hz for 

stroke symbology or non-interlaced raster and 30/60 Hz for interlace raster are generally 

satisfactory. Some map information may be judged as adequate for enroute navigation displays 

with update rates of at least 1 Hz, depending on the specific aircraft. Update other critical data, 

such as attitude, heading, or air data symbology, at a rate of at least 15 Hz, depending on the 

airplane. 

20.0 CONTROLS 

Display controls should be clearly visible, labeled, and usable by the pilot, with the least practicable 

deviation from the normal position and from the line of vision when the pilot is looking forward 

along the flight path. Controls should have an appropriate amount of tactile feel (for example, 

detents, friction, stops, or damping, etc.) so they can be changed without undue concentration, 

which minimizes the potential for inadvertent changes. Design controls for the pilot to use 

intuitively. The controls should be identified easily and located in all lighting conditions, allow 

differentiation of one control from another, and have feedback through the system appropriate for 

the function being controlled. 

21.0 TEST FUNCTIONS 

The electronic display should incorporate a pilot selectable or automatic test mode, such as built in 

testers, that exercises the system to a depth appropriate to the system design. Include this function 

even if the system failure analysis is not dependent on such a mode, or if display test is also a 

maintenance function. The test mode (or a sub mode) should display warning flags in their proper 

locations. Exercise alerting and annunciation functions that are necessary to alert the pilot of unsafe 

conditions. It is acceptable to incorporate the display test with a centralized cockpit light test 

switch to have the display test function disabled when airborne. The test mode may provide a 

convenient means to display the software configuration. 

22.0 COLOR STANDARDIZATION 

22.1 General 

Color is considered an enhancement for understanding the display information that leads to 

performance improvement. Select color to minimize display interpretation errors. A proliferation 

of color sets can ultimately reduce safety rather than increase it. Using contrast between basic 

colors provides a better differentiation of display elements than arbitrarily using colors near to each 

other in the color table. Before defining the color standard for a specific display, establish a 

consistent color philosophy throughout the display. The FAA does not intend to limit electronic 

displays to the below listed colors, although these have been shown to work well. The following 

section depicts colors found acceptable for compliance with § 23.1322, and other recommended 

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6/14/05 AC 23.1311-1B 

colors as related to their functional meaning for electronic display systems. Deviations may be 

approved with acceptable justification. The use of the colors red and yellow for other than 

warnings and cautions is discouraged. 

22.2 Color for Display Features 

Color code display features should be as follows: 

Warnings Red 

Flight envelope and system limits Red 

Cautions, abnormal sources Amber/Yellow 

Earth Tan/Brown 

Scales and associated figures White 

Engaged modes, flight guidance Green 

Sky Cyan/Blue 

ILS deviation pointer Magenta 

Flight director bar Magenta/Green 

Pilot selectable references (bugs) Magenta 

22.3 Color Sets 

One of the following color sets should be used: 

Color Set 1 Color Set 2

Fixed reference symbols, that is, lubber lines White Yellow* 

Current data, values White Green 

Armed modes White Cyan 

Selected data, values Green Cyan 

Selected heading Magenta** Cyan 

Active route/flight plan Magenta White 

*The extensive use of the color yellow for other than caution/abnormal information is 

discouraged. 

**In color set 1, magenta is associated with those analog parameters that constitute "fly to" 

or "keep centered" type information. 

22.4 Color for Depiction of Weather Precipitation and Turbulence 

The depiction of weather precipitation and turbulence should be coded as follows: 

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AC 23.1311-1B 6/14/05 

Precipitation 0-1 mm/hr Black 

 1-4 " Green 

 4-12 " Amber/Yellow 

 12-50 " Red 

Above 50 " Red or Magenta 

Turbulence " White or Magenta 

Icing " Light Blue

A background color (neutral color) will enhance display presentation. 

22.5 Color Deviation 

When the color assignments deviate from the above color set, the applicant should ensure the 

chosen color assignments are not susceptible to confusion of symbol meaning and increased 

workload. Where appropriate, color assignment should be consistent with other color displays in 

the panel. Luminance and color differences should not be confusing or ambiguous under any 

operating ambient illumination conditions. The specific colors should be consistent with change in 

brightness on the displays over the full range of ambient light conditions. Under high and low 

levels of lighting, color degradation should not prevent the pilot from properly interpreting display 

information. Where precipitation is integrated with other information, the precipitation colors can 

be presented at half intensity. Service experience has shown that this provides enhanced 

presentation and reduced ambiguity. Warnings should be at full intensity. 

22.6 Enhancement 

Color is an enhancement for understanding the display information that leads to performance 

improvement, but it should not be the sole means of discrimination of critical information. Use 

symbols or letters, as well as color, to further enhance the effectiveness of the display. Use of color 

alone has been shown to be less effective than when used with distinct symbol (object, graphic, or 

letter). Color degradation should be obvious and should not preclude the pilot from interpreting the 

remaining display information. Displays should remain legible, stable, and unambiguous when 

operating in a degraded mode. 

22.7 Color for Warnings and Cautions 

For warnings and cautions, § 23.1322 provides specific requirements for assigning red and amber 

for visual annunciations. Use red as the warning annunciation for emergency operating conditions 

when immediate flight crew recognition is required, and immediate correction or compensatory 

action may be required. Use amber for the cautionary annunciation for abnormal operating 

conditions when immediate flight crew awareness is required, and subsequent flight crew action 

may be required. Use white or another unique color for advisory annunciations of operating 

conditions that require flight crew awareness and, possibly, action. Use green for indication of safe 

operating conditions. 

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6/14/05 AC 23.1311-1B 

22.8 Airplane Flight Manual 

Include a complete list of warnings, cautions, and annunciation messages in the AFM, supplemental 

AFM, and placards. If the manufacturer's Pilot Operating Guide is found adequate and acceptable, 

it may be referenced in the AFM or supplemental AFM as a means to satisfy this requirement 

23.0 COLOR FOR AVIATION ROUTINE WEATHER 

23.1 General 

For electronic color graphic display of aviation routine weather to surface meteorological data, refer 

to METARS see TSO-C157, Aircraft Flight Information Services-Broadcast (FIS-B) Data Link 

Systems and Equipment and RTCA/DO-267A, Minimum Aviation System Performance Standards 

(MASPS) for Flight Information Services-Broadcast (FIS-B) Data Link. 

24.0 GENERAL INSTALLATION REQUIREMENTS 

The TC/STC/ATC/ASTC applicant must show that the installed electronic display system

configuration (including hardware and software) meets the appropriate airplane certification basis. 

This demonstration must include applicable functional TSO(s), or equivalent, functional 

performance, interoperability, aircraft-level and system-level safety assessments, environmental 

qualification, system integration test, flight test, software assurance, hardware assurance, and other 

certification activities (as required to show compliance to the regulations). TC/STC/ATC/ASTC 

applicants may use TSO data to support airworthiness assessment if they show that the TSO 

requirements apply to the installation. 

25.0 AIRCRAFT ELECTRICAL POWER SOURCE 

25.1 Electrical Power 

Install each electronic display instrument system so that it receives electrical power from a bus that 

provides the necessary reliability, according to the § 23.1309 safety assessment, without 

jeopardizing other essential or critical electrical loads connected to that bus. The applicant should 

provide a means to indicate when adequate power is available for proper operation of the 

instrument. 

25.2 Power Interruptions 

Use techniques that reduce the momentary power interruptions or design the equipment so 

momentary power interruptions will not adversely affect the availability or integrity of essential 

information required for continued safe flight and landing. The category selected from RTCA/DO160( ) for momentary power interruptions should be appropriate for the intended use. The PFD 

being used by the pilot during the takeoff phase of flight should be usable within one second after a 

momentary power interruption up to a 200-millisecond duration. Large electrical loads required to 

restart an engine (for example, turboprops and small jets) should not affect the availability or 

integrity of essential information required for continued safe flight and landing. 

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AC 23.1311-1B 6/14/05 

25.3 Independent Power Source 

a. Each reversionary or standby display providing primary flight information should be 

powered from a power source independent of the source for the primary display. It should function 

independently from the primary display, such as a second alternator or battery. The power source 

for each reversionary display should provide for uninterrupted operation for at least 30 minutes 

after failure of the power source for the primary display. The independent power source may be 

provided by manual or automatic means. Section 23.1353(h) requires a minimum supply of 30 

minutes of electrical power to the essential loads for continued safe flight and landing of the 

airplane should a complete loss of the primary electrical power generating system occur, including 

the reversionary displays. The airplane's primary electrical power includes the airplane's electrical 

generating system and the airplane's starter battery when only one battery is installed. The starter 

battery is not considered an acceptable standby power source unless a proper state of charge is 

monitored and displayed to the pilot. In this case, an ELOS may be required. 

b. The intent of this guidance may be met by a power generation and distribution 

architecture with multiple power sources and multiple distribution paths. The paths must be 

designed such that any single failure of a power generation or distribution component does not 

adversely affect the primary, reversionary, or standby displays. It does not need independent 

sources for the primary and reversionary or standby displays. 

c. For single engine airplanes where the engine drives the power generation devices, the 

engine is not considered to be a single power source for this guidance. For example, a single engine 

airplane with two engine driven alternators, one powering a PFD and the other powering a 

reversionary PFD, is considered to meet this guidance. However, this does not exempt the 

applicant from the § 23.1353(h) requirements. Section 23.1331(c) requires two independent 

sources of power, but it does not require installing dual alternators or vacuum systems on single 

engine airplanes. There are other options. First, you could include a dedicated battery with a 30-

minute capacity for electrical instrument loads essential to continued safe flight and landing. 

Second, you could use of differently powered types of instruments for primary and standby. 

Finally, you could verify the aircraft battery used for starting by a system safety analysis under 

§ 23.1309. See AC 23-17B for more guidance. 

26.0 SAFETY ASSESSMENTS 

26.1 Regulations Before and After Amendment 23-41 

Part 23 regulations, promulgated before Amendment 23-41, were based on single-fault or fail-safe 

concepts. A single failure would cause the loss of only one primary instrument function. Only 

mechanical or electromechanical instruments that function independently of the primary parameter 

display were envisioned; that is, flight and powerplant instruments were isolated and independent. 

Sometimes, several other instrument functions (indication of the function, display, or indicator) are 

housed in a common case. Since electronic displays permit presentation of several parameters on 

one display, a failure in the electronic display may affect more than one required parameter. 

Section 23.1309, Amendment 23-41, allowed approval of more advanced and complex systems. 

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6/14/05 AC 23.1311-1B 

Amendment 23-41 also incorporated § 23.1311 into part 23, which provides the standards for 

electronic displays. Section 23.1311, Amendment 23-49, revised and clarified the secondary 

instruments and the visibility requirements. 

26.2 Common-Mode Failures 

Section 23.1311(b) states that “the electronic display indicators, including their systems and 

installations, and considering other airplane systems, must be designed so that one display of 

information essential for continued safe flight and landing will remain available to the crew, 

without need for immediate action by any pilot for continued safe operation, after any single failure 

or probable combination of failures.” In general, without considering specific characteristics of an 

airplane design, information essential to continued safe flight and landing are attitude, airspeed, 

altitude, warnings, and any applicable propulsion parameter(s). Address major common-mode 

failures. Design systems such that a fault in one system does not cause a fault in a different 

system. These include such failures induced by software errors, lightning effects, electromagnetic 

interference, power transients, cooling, etc., that could simultaneously affect the display of more 

than one parameter. AC 23.1309-1C explains the criticality of these failure conditions. 

26.3 Safety Analysis 

a. AC 23.1309-1C describes safety assessment methods for identifying and classifying 

each failure condition and choosing the method(s) of safety assessment. Certification of electronic 

display systems may involve new and complex technology that may not use traditional serviceproven design concepts. In this case, technically qualified judgment can be enhanced when a 

quantitative analysis is included in the safety assessment, whether or not a quantitative analysis is 

required by § 23.1309. 

b. The use of electronic displays allows a higher degree of integration than was practical 

with previous electromechanical instruments. Evaluating failure states and determining display 

function criticality in highly integrated systems may be complex. Safety assessment determination 

should refer to the display function and include all causes that could affect the displays of that 

function, not only the display equipment. 

c. Installing electronic systems in cockpits creates complex functional interrelationships 

between the pilots and other display and control systems. The FHA identifies the failure conditions 

for all display functions, analyzes the effects on the aircraft and flight crew, and assigns the 

corresponding criticality classification (no safety effect, minor, major, hazardous, catastrophic). It 

also considers both loss of functions, malfunctions, and situations that provide misleading 

information. 

d. A pilot initiated preflight test may be used to reduce failure exposure times associated 

with the safety analysis required under § 23.1309. If the flight crew is required to test a system

before each flight, assume, for the safety analysis, the flight crew will accomplish this test at least 

once a day, providing the preflight test is conveniently and acceptably implemented. 

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AC 23.1311-1B 6/14/05 

27.0 SOFTWARE AND HARDWARE DEVELOPMENT ASSURANCE 

27.1 General 

Applicants must show compliance with § 23.1309, regardless of the intended function of the 

display system. The equipment shall be designed to the appropriate software and hardware 

development assurance level(s) based on the intended function and application of the equipment, 

including the aircraft class in which it is to be installed (see AC 23.1309-1C, Figure 2). The 

appropriate development assurance level(s) are determined by an analysis of the failure modes of 

the equipment and a categorization of the effects of the failure on the operation of the aircraft. For 

the analysis for displays, a failure is defined as either a loss of function or the output of misleading 

information. Flight guidance information must meet the appropriate design assurance levels 

required for that function. 

27.2 Software Guidance 

27.2.1 General

AC 20-115B discusses how RTCA/DO-178B provides an acceptable means for showing that 

software complies with pertinent airworthiness requirements. All software used in electronic 

displays systems should be developed to the guidance of RTCA/DO-178B, Software Considerations 

in Airborne Systems and Equipment Certification, dated December 1, 1992, or another acceptable 

means of compliance, as agreed to between the applicant and the appropriate FAA Aircraft 

Certification Office (ACO). 

27.2.2 Software Levels 

Determine all software levels by appropriate safety assessments (see AC 23.1309-1C, Figure 2) and 

any more requirements, such as those specified by functional TSOs. 

27.2.3 Field-Loadable Software (FLS) 

Many electronic displays systems use Field-Loadable Software (FLS) as part of the 

TC/STC/ASC/ASTC installation. FLS is software that can be loaded without removal of the 

equipment from the aircraft installation. FLS might also include software loaded into a line 

replaceable unit (LRU) or hardware element at a repair station or shop. FLS can refer to either 

executable code or data. When obtaining certification approval for use of the FLS capability, refer 

to the guidance in Order 8110.49 and AC 20-145. 

27.3 Electronic Hardware Guidance 

If the electronic display system contains electronic devices whose functions cannot feasibly be 

evaluated by test and/or analysis, the electronic devices should comply with RTCA/DO-254, or 

other acceptable means of compliance, as agreed to by the appropriate ACO. Determine the 

hardware levels for all hardware by the appropriate safety assessments (see AC 23.1309-1C, Figure 

2) and any more requirements, such as those specified by functional TSOs. 

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6/14/05 AC 23.1311-1B 

28.0 ENVIRONMENTAL CONDITIONS 

28.1 General 

The equipment environmental limits established by the manufacturer should be compatible with the 

operating environment of the airplane. Evaluation of the equipment installation should consider 

factors such as the maximum operating altitude of the airplane and whether the equipment is located 

within a temperature and pressure-controlled area. Applicable methods for testing the performance 

characteristics of equipment for specified environmental conditions are provided in RTCA/DO160( ). Either test or analysis, or both, ensures the compatibility between the operational 

environment and the environmental equipment category of the laboratory tests. 

28.2 Temperature 

Electronic systems reliability is strongly related to the temperature of the solid-state components in 

the system. Component temperatures are dependent on internal thermal design and external 

cooling. In evaluating the temperature environment, consider the additional heat generated by the 

equipment, especially in a location where airflow is restricted. To determine if adequate cooling is 

provided, the evaluation should make maximum use of previous data from comparable installations, 

thus limiting ground or flight tests to those installations that cannot be verified conveniently by 

other means. When the equipment-operating environment cannot be verified from previous 

experience or from an evaluation of temperature values in that equipment location, a cooling test 

should be conducted. 

28.3 Attitude Information 

Attitude information should continue to be presented for a minimum of 30 minutes after the inflight loss of cooling for the primary instrument when operating in the normal operating 

environment (temperature/altitude). If proper performance of the flight instrument function(s) is 

adversely affected due to in-flight loss of cooling, such failure conditions should be annunciated. 

Consider automatic over-temperature shutdown of the system a failure condition. Document 

subsequent pilot actions in the AFM or on placards. These actions may include procedures to allow 

possible recovery of a system that has an over-temperature shutdown condition. 

28.4 Annunciation 

Annunciation of in-flight loss of cooling or fan monitors may not be required if it is shown by a 

safety analysis or test demonstration that a hazardous or catastrophic failure condition does not 

occur. The safety analysis should consider the reliability of the fans, redundancies of the functions, 

reversionary features (such as the ability to transfer critical functions), the annunciation of overtemperature and its response time, and the availability of other flight instrumentation. In some

systems, cooling fans may only be installed to extend the life of the components and not to prevent 

a failure condition or shutdown of the equipment. These types of installations do not require fan 

monitors or temperature sensors. If the cooling fans are needed to prevent a hazardous or 

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AC 23.1311-1B 6/14/05 

catastrophic failure condition, install fan monitors or another method to determine the status of the 

cooling fan during preflight checks. 

29.0 ELECTROMAGNETIC PROTECTION 

Current trends indicate increasing reliance on electrical and electronic systems for safe operations. 

For systems that perform flight, propulsion, navigation, and instrumentation functions, consider 

electromagnetic effects. AC 23.1309-1C and AC 23-17B provide more guidance for lightning and 

High Intensity Radiated Fields (HIRF) protection.

30.0 ELECTROMAGNETIC INTERFERENCE 

The electronic display instrument system should not be the source of objectionable conducted or 

radiated interference. Conducted or radiated interference from other equipment or systems installed 

in the airplane should not adversely affect the displays. 

31.0 IMPLOSION PROTECTION 

Design and construct the display unit to prevent implosion when the unit is operating over the range 

of normal and abnormal operating environment in the airplane. When a display unit has a 

component containing lower pressure than the ambient atmospheric pressure and it is susceptible to 

implosion, no incapacitation of the flight crew or adjacent equipment should result if an implosion 

occurs. Test the display unit for the most severe environmental conditions of pressure and 

temperature levels. Also test for variations in both normal and abnormal operating conditions 

(including overpressure and decompression) specified by RTCA/DO-160( ). To verify that the 

display unit is acceptable if an implosion occurs, the unit should meet the requirements in UL 1418 

listed in paragraph 3.4 of this AC. Similarity of a particular display to a unit already tested may be 

used to comply with this requirement. 

32.0 CONFIGURATION MANAGEMENT BY ELECTRONIC IDENTIFICATION GUIDANCE 

Configuration management may be necessary because the system may contain many hardware 

elements and functional software components, with multiple approved configurations. 

Identification of software components field-loaded into hardware elements may be implemented by 

electronic means. Section 21.607, requires equipment with a TSO to be permanently and legibly 

marked with specific information. Compliance with § 21.607 may be shown when an electronic 

identification query system stored in non-volatile memory provides the required information. This 

approach is commonly referred to as an “electronic TSO nameplate.” The electronic identification 

system must be verifiable on board the aircraft when the aircraft is on the ground at any geographic 

location. The system must provide the specific information required by § 21.607 for all applicable 

functional TSOs being integrated. All hardware elements that support a functional TSO must have 

a physical TSO nameplate. Even when electronic identification (that is, electronic nameplate) is 

used, a physical TSO nameplate must be included on supporting hardware elements. See AC 20-

145 for more guidance. 

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