Subject: Installation of Electronic Display 

in Part 23 Airplanes 

Date: 11/17/2011 

Initiated by: ACE-100 

AC No: 23.1311-1C

This advisory circular (AC) provides guidance for showing compliance with certain requirements of 

Title 14, Code of Federal Regulations (CFR), part 23, as well as general guidance for the design, 

installation, integration, and approval of electronic flight deck displays, components, and systems 

installed in part 23 category airplanes. The guidance provided in this document is directed to 

airplane and avionics manufacturers, modifiers, and operators of part 23 category airplanes. 

Applicants for a technical standard order (TSO) should consider following the guidance in this AC 

when the TSO requirements do not provide sufficient guidance. The main purpose of this revision 

of the AC is providing the guidance for the requirements in the turbojet rulemaking and some 

general updating due to lessons learned and advance and emerging technologies. 

s/ 

Earl Lawrence 

Manager, Small Airplane Directorate 

Aircraft Certification Service 

11/17/2011 AC 23.1311-1C 

iii (and iv) 

TABLE OF CONTENTS 

Section Page 

1.0 Purpose......................................................................................................................................1 

2.0 Cancellation. .............................................................................................................................1 

3.0 Related Regulations and Documents. .......................................................................................1

4.0 Background...............................................................................................................................8 

5.0 Scope.........................................................................................................................................8 

6.0 Acronyms/Definitions...............................................................................................................9 

7.0 Display Description. ...............................................................................................................17 

8.0 Flight Displays........................................................................................................................17 

9.0 Powerplant Displays. ..............................................................................................................25 

10.0 Electronic Displays for Navigation Information. .................................................................27 

11.0 Aircraft Flight Manual (AFM)..............................................................................................28 

12.0 Electronic Checklist and Charts............................................................................................28 

13.0 General Human Factors Consideraations for Design of Electronic Displays.......................28 

14.0 Location and Configuration of Displays...............................................................................31 

15.0 Pilot Field-of-View Considerations......................................................................................32 

16.0 Luminance.............................................................................................................................36 

17.0 Symbology and Format.........................................................................................................36 

18.0 Annunciation.........................................................................................................................43 

19.0 Lag Time and Data Update...................................................................................................44 

20.0 Controls.................................................................................................................................45 

21.0 Test Functions.......................................................................................................................45 

22.0 Color Standardization. ..........................................................................................................45 

23.0 General Installation Requirements........................................................................................48 

24.0 Aircraft Electrical Power Source. .........................................................................................48 

25.0 Safety Assessments...............................................................................................................50 

26.0 Software and Hardware Development Assurance. ...............................................................51 

27.0 Environmental Conditions. ...................................................................................................52 

28.0 Electromagnetic Protection...................................................................................................52 

29.0 Electromagnetic Interference................................................................................................53 

30.0 Implosion Protection.............................................................................................................53 

31.0 Configuration Management by Electronic Identification Guidance.....................................53 

11/17/2011 AC 23.1311-1C 

1 

1.0 Purpose. This advisory circular (AC) provides guidance for showing compliance with certain 

requirements of Title 14, Code of Federal Regulations (CFR), part 23, as well as general guidance 

for the design, installation, integration, and approval of electronic flight deck displays, components, 

and systems installed in part 23 category airplanes. The guidance provided in this document is 

directed to airplane and avionics manufacturers, modifiers, and operators of part 23 category 

airplanes. Applicants for a technical standard order (TSO) should consider following the guidance 

in this AC when the TSO requirements do not provide sufficient guidance. The main purpose of 

this revision of the AC is providing the guidance for the requirements in the turbojet rulemaking 

from Amendment 23-62 and some general updating due to lessons learned and advance and 

emerging technologies. 

1.1 This AC provides an acceptable means, but not the only means, of showing compliance 

with 14 CFR applicable to installing electronic displays in part 23 airplanes. The applicant remains 

responsible for regulatory compliance and should work closely with their geographic Aircraft 

Certification Office (ACO) to ensure regulatory compliance. This material is neither mandatory nor 

regulatory in nature and does not constitute a regulation. You may follow an alternate FAAapproved method. Mandatory words such as “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 23.1311-1B, Change 1 “Installation of Electronic Display Instrument 

Systems in part 23 Airplanes,” dated February 17, 2009, is cancelled. 

3.0 Related Regulations and Documents. Some of the following related documents in this 

section may not be referenced in this AC, but they provide additional information or guidance for 

electronic displays. Please check for the most recent revision of the documents listed. 

3.1 Regulatory Sections. These acceptable means of compliance refer to the applicable 

sections of 14 CFR, part 23. For airplanes certificated under Civil Air Regulations (CAR) 3, we 

show the corresponding paragraphs of the former CAR in parenthesis. 

Table 1 - Regulatory Sections 

§ 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 

§ 23.1308 High-intensity Radiated Fields (HIRF) 

Protection 

§ 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 
11/17/2011 AC 23.1311-1C 

2 

§ 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, and 

3.675) 

Powerplant instruments installation 

§ 23.1351 (3.681, 3.682, 3.685, and 3.686) Electrical Systems and Equipment: General 

§ 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 

§ 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 
11/17/2011 AC 23.1311-1C 

3 

§ 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 latest version of the 

ACs, notices, orders, and policy statements on the FAA website: www.faa.gov. 

Table 2 - Advisory Circulars and Related Documents 

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

(Displays) 

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

AC 20-136A Protection of Aircraft Electrical/Electronic Systems Against the 

Indirect Effects of Lightning 

AC 20-138B Airworthiness Approval of Positioning and Navigation Systems 

AC 20-140A Guidelines for Design Approval of Aircraft Data Link 

Communication Systems Supporting Air Traffic Services (ATS) 

AC 20-149 Safety and Interoperability Requirements for Initial Domestic 

Flight Information Service - Broadcast 

AC 20-152 RTCA, Inc., Document RTCA/DO-254, Design Assurance 

Guidance for Airborne Electronic Hardware 

AC 20-153A Acceptance of Aeronautical Data Processes and Associated 

Navigation Databases 

AC 20-155 SAE Documents to Support Aircraft Lightning Protection 

Certification 

AC 20-158 The Certification of Aircraft Electrical and Electronic Systems 

for Operation in the High-Intensity Radiated Fields (HIRF) 

Environment 

AC 20-167 Airworthiness Approval of Enhanced 

Vision System, Synthetic Vision System, 

Combined Vision System, and Enhanced Flight 

Vision System Equipment 
11/17/2011 AC 23.1311-1C 

4 

AC 20-170 Integrated Modular Avionics Development, Verification, 

Integration and Approval Using RTCA/DO-297 and Technical 

Standard Order C153 

AC 21-16F RTCA Document DO-160 versions D, E and F, “Environmental 

Conditions and Test Procedures for Airborne Equipment 

AC 23-8C Flight Test Guide for Certification of Part 23 Airplanes 

AC 23-15A Small Airplane Certification Compliance Program 

AC 23-17C 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 23-22 Guidance for Approved Model List (AML) Supplemental Type 

Certificate (STC) Approval of Part 23 Airplane Avionics 

Installations 

AC 23-23 Standardization Guide for Integrated Cockpits in Part 23 

Airplanes 

AC 23.1309-1E System Safety Analysis and Assessment for Part 23 Airplanes 

AC 25-11A Electronic Flight Deck Displays 

AC 90-106 Enhanced Flight Vision Systems 

AC 91-75 Attitude Indicator 

AC 91-78 Use of Class 1 or Class 2 Electronic Flight Bag (EFB) 

AC 120-64 Operational Use and Modification of Electronic Checklists 

AC 120-76A Guidelines for the Certification, Airworthiness, and Operational 

Approval of Electronic Flight Bag Computing Devices 

Order 8110.49 Software Approval Guidelines, dated June 3, 2003 

Order 8110.105 Simple and Complex Electronic Hardware Approval Guidance 

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

Factors for Certification of Part 23 Small Airplanes 

3.3 Technical Standard Orders (TSO). You may access the TSOs on the FAA website: 

www.faa.gov. The following is a list of the FAA TSOs that are referenced in this AC. For a 

complete list of TSOs that are related to this AC, see AC 20-110L, “Index of Aviation Technical 

Standards Orders” or the web site for the most current list. 

a. TSO-C63c, Airborne Weather and Ground Mapping Pulsed Radars. 

b. TSO-C113, Airborne Multipurpose Electronic Displays. 

c. TSO-C153, Integrated Modular Avionics Hardware Elements. 

d. TSO-C157, Aircraft Flight Information Services-Broadcast (FIS-B) Data Link Systems 

and Equipment. 
11/17/2011 AC 23.1311-1C 

5 

e. TSO-C165, Electronic Map Display Equipment for Graphical Depiction of Aircraft 

Position. 

3.4 Industry Documents. You may obtain copies of current editions of the following 

publications. 

3.4.1 RTCA Documents. The following RTCA documents are available from RTCA, 

Inc., 1828 L Street NW, Suite 805, Washington, DC 20036-4001 or at their website at 

www.rtca.org. 

a. RTCA/DO-160G, Environmental Conditions and Test Procedures for Airborne 

Equipment. 

b. RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment 

Certification. 

c. RTCA/DO-187, Minimum Operational Performance Standards for Airborne 

Area Navigation Equipment Using Multi-Sensor Inputs. 

d. RTCA/DO-200A, Standards for Processing Aeronautical Data. 

e. RTCA/DO-201A, Standards for Aeronautical Information. 

f. RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware. 

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

Depiction of Navigation Information on Electronic Maps. 

h. RTCA/DO-267A, Minimum Aviation System Performance Standards (MASPS) 

for Flight Information Services-Broadcast (FIS-B) Data Link. 

i. RTCA/DO-297, Integrated Modular Avionics (IMA) Development Guidance and 

Certification Considerations. 

j. RTCA/DO-313, Certification Guidance for Installation of Non-Essential, NonRequired Aircraft Cabin Systems and Equipment. 

k. RTCA/DO-315A: Minimum Aviation Performance Standards (MASPS) for 

Enhanced Vision Systems, Synthetic Vision Systems, Combined Vision Systems, and Enhanced 

Flight Vision Systems. 

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. 
11/17/2011 AC 23.1311-1C 

6 

a. ARP 268G, Location and Actuation of Flight Deck Controls for Transport 

Aircraft. 

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

c. ARP 926B, Fault/Failure Analysis Procedure. 

d. AIR 1093A, Numeral, Letter and Symbol Dimensions for Aircraft Instrument 

Displays. 

e. ARP 1161A, Crew Station Lighting—Commercial Aircraft. 

f. ARP 1782A, Photometric and Colorimetric Measurement Procedures for 

Airborne Direct View CRT [Cathode Ray Tube] Displays. 

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

h. ARP 1874, Design Objectives for CRT Displays for Part 25 (Transport) Aircraft. 

i. ARP 4032A, Human Engineering Considerations in the Application of Color to 

Electronic Aircraft Displays. 

j. ARP 4033, Pilot System Integration. 

k. ARP 4067, Design Objectives for CRT Displays for Part 23 Aircraft. 

l. ARP 4101, Flight Deck Layout and Facilities. 

m. ARP 4102, Flight Deck Panels, Controls, and Displays. 

n. ARP 4102/7, Electronic Displays. 

o. ARP 4103, Flight Deck Lighting for Commercial Transport Aircraft. 

p. ARP 4105B, Abbreviations and Acronyms for Use on the Flight Deck. 

q. ARP 4155A, Human Interface Design Methodology for Integrated Display 

Symbology. 

r. ARP 4256A, Design Objectives for Liquid Crystal Displays for Part 25 

(Transport) Aircraft. 

s. ARP 4260A, Photometric and Colorimetric Measurement Procedures for 

Airborne Electronic Flat Panel Displays. 
11/17/2011 AC 23.1311-1C 

7 

t. ARP 4754, Certification Considerations for Highly Integrated or Complex 

Aircraft Systems. 

u. ARP 4761, Guidelines and Methods for Conducting the Safety Assessment 

Process on Civil Airborne Systems and Equipment. 

v. ARP 5287, Optical Measurement Procedures for Airborne Head-Up Display 

(HUD). 

w. ARP 5288, Transport Category Airplane Head Up Display (HUD) Systems. 

x. ARP 5289, Electronic Aeronautical Symbols. 

y. ARP 5364, Human Factor Considerations in the Design of Multifunction Display 

Systems for Civil Aircraft. 

z. ARP 5365, Human Interface Criteria for Cockpit Display of Traffic Information. 

aa. ARP 5430, Human Interface Criteria for Vertical Situation Awareness 

Displays. 

bb. ARP 5677, Human Engineering Considerations for Cockpit Integration of 

Enhanced/Synthetic Vision Systems. 

cc. AS 5703, Minimum Performance Standard for Enhanced Vision System. 

dd. AS 8034A, Minimum Performance Standard for Airborne Multipurpose 

Electronic Displays. 

ee. AS 8055, Minimum Performance Standard for Airborne Head Up Display 

(HUD). 

3.4.3 General Aviation Manufacturers Association (GAMA). The following documents 

are available from the GAMA, 1400 K St. NW Suite 801, Washington, DC 2005 or from their 

website at www.gama.aero/industry-standards. 

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

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

b. 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.
11/17/2011 AC 23.1311-1C 

8 

4.0 Background. 

a. 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 developed 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 14 CFR with the Joint Aviation 

Requirements (JAR). Section 23.1311, Amendment 23-49, removed redundant requirements and 

clarified which secondary instruments are required, including the visibility requirements for those 

instruments. 

b. Amendment 23-62 made several changes that affect the installation of electronic 

displays. Guidance relative to electronic displays of those sections is also included in this AC. The 

significant changes were: 

(1) Clarified requirements for trend information and appropriate sensory cues; 

(2) Incorporated equivalent visual displays of the instrument markings on electronic 

displays; 

(3) Allowed an applicant to take credit for reversionary or secondary flight displays on a 

multi-function flight display (MFD) that provides a secondary means of primary flight information 

(PFI); 

(4) Revised some redundancy requirements to be only applicable for IFR operations; 

(5) Accommodated new technology for magnetic direction indicator; 

(6) Updated the terminology for system safety assessment; 

(7) Revised requirements for instruments using power source(s); and 

(8) Revised requirements for storage battery backup times. 

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 and this AC. The Small Airplane Directorate will coordinate and 

resolve the conflicts among the points of contact of the other documents. 
11/17/2011 AC 23.1311-1C 

9 

6.0 Acronyms/Definitions. 

6.1 Acronyms. 

a. AC, Advisory Circular 

b. ACO, Aircraft Certification Office 

c. ADC, Air Data Computer 

d. ADI, Attitude Direction Indicator 

e. ADDS, Aviation Digital Data Service 

f. AFM, Airplane Flight Manual 

g. AFMS, Airplane Flight Manual Supplement 

h. AHRS, Attitude Heading Reference System 

i. ARD, Aerospace Research Document 

j. ARP, Aerospace Recommended Practice 

k. AS, Aerospace Standard 

l. ASTC, Amended Supplemental Type Certificate 

m. ATC, Amended Type Certificate 

n. CAR, Civil Air Regulations 

o. CDI, Course Deviation Indicator 

p. CFR, Code of Federal Regulations 

q. CIP, Current Icing Potential 

r. C/L, Center Line 

s. CRT, Cathode-Ray Tubes 

t. DN, Down 

u. EADI, Electronic Attitude Direction Indicator 
11/17/2011 AC 23.1311-1C 

10 

v. EHSI, Electronic Horizontal Situation Indicator 

w. EICAS, Engine Indication and Crew Alert System 

x. ELOS, Equivalent Level of Safety 

y. EVS, Enhanced Vision Systems 

z. FAA, Federal Aviation Administration 

aa. FD, Flight Director 

bb. FHA, Functional Hazard Assessment 

cc. FLS, Field-Loadable Software 

dd. FMEA, Failure Modes and Effects Analysis 

ee. FOV, Field-Of-View 

ff. GPS, Global Positioning System 

gg. HIRF, High Intensity Radiated Fields 

hh. HUD, Head-Up Display 

ii. HSI, Horizontal Situation Indicators 

jj. ICAO, International Civil Aviation Organization 

kk. IFR, Instrument Flight Rules 

ll. ILS, Instrument Landing System 

mm. IMA, Integrated Modular Avionics 

nn. IMC, Instrument Meteorological Conditions 

oo. JAR, Joint Aviation Requirements 

pp. LCD, Liquid Crystal Displays 

qq. LED, Light Emitting Diodes 

rr. LT, Left 
11/17/2011 AC 23.1311-1C 

11 

ss. METAR, ICAO Routine Aviation Weather Report 

tt. MFD, Multifunction Flight Display 

uu. ND, Navigation Display 

vv. NOM, Nominal 

ww. PFD, Primary Flight Display 

xx. PFI, Primary Flight Information 

yy. POH, Pilot's Operating Handbook 

zz. RAIM, Receiver Autonomous Integrity Monitoring (used with GPS) 

aaa. RT, Right 

bbb. SAE, Society of Automotive Engineers 

ccc. STC, Supplemental Type Certificate 

ddd. SVS, Synthetic Vision Systems 

eee. TAS, Traffic Advisory System 

fff. TAWS, Terrain Awareness Warning System 

ggg. TFR, Temporary Flight Restrictions 

hhh. TC, Type Certificate 

iii. TCAS, Traffic Alert and Collision Avoidance System 

jjj. TSO, Technical Standard Order 

kkk. UL, Underwriter’s Laboratories 

lll. VOR, Very High Frequency Omni-Directional Range 

mmm. VFR, Visual Flight Rules 

nnn. VMC, Visual Meteorological Conditions 

ooo. VFE, Maximum flap extended speed 
11/17/2011 AC 23.1311-1C 

12 

ppp. VMO, Maximum operating limit speed 

qqq. VNE, Never-exceed speed 

rrr. VNO, Maximum structural cruising speed 

sss. VS0, The stalling speed or the minimum steady flight speed in the landing 

configuration 

ttt. VS1, The stalling speed or the minimum steady flight speed obtained in a specific 

configuration 

uuu. WAAS, Wide Area Augmentation System 

6.2 Definitions. This section contains definitions for terms in this document. 

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

true value. 

b. 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. 

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

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

d. 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. 

e. 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." 

f. Critical: Usually 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.” 

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

software, etc., considering abnormal behavior (of this function, hardware, software, etc.) alone, in 
11/17/2011 AC 23.1311-1C 

13 

combination, or in combination with external events. Criticality is a failure classification that could 

be no safety effect, minor, major, hazardous, and catastrophic. See AC 23.1309-1E for more 

guidance. 

h. 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. 

i. 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. 

j. 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. 

k. Enhanced Vision System: An electronic means to provide a display of the forward 

external scene topography (the natural or manmade features of a place or region especially in a way 

to show their relative positions and elevation) through the use of imaging sensors, such as a forward 

looking infrared, millimeter wave radiometry, millimeter wave radar, low light level image 

intensifying. 

l. 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. 

m. Error: An omitted or incorrect action by a pilot or maintenance person, or a mistake 

in requirements, design, or implementation.

n. 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. 

o. Failure Condition: 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 23.1309-1E for more 

information on definitions of failure conditions. 

p. 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. 

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

waypoint, intersection, reporting point, etc. 
11/17/2011 AC 23.1311-1C 

14 

r. 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. 

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

pilot 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. 

t. 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. 

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

supplies, etc. 

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

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

w. Head-Up Display: A transparent optical display system located level with and 

between the pilot and the forward windscreen. The HUD displays a combination of control, 

performance, navigation, and command information superimposed on the external field of view. It 

includes the display element, sensors, computers, and power supplies, indications and controls. It is 

integrated with airborne attitude, air data and navigation systems, and as a display of command 

information is considered a component of the flight guidance system. 

x. 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. 

y. 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. 

z. Instrument: An electrical or mechanical measurement device. In § 23.1311 it is 

defined as: 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.) 

aa. 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 
11/17/2011 AC 23.1311-1C 

15 

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. 

bb. 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). 

cc. 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. 

dd. Multi-Function Display: Any physical display unit, other than the PFD, used to 

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

ee. Navigation: The process of planning, tracking, and controlling the course of an 

airplane from one place to another. 

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

presented to the pilot. 

gg. Navigation Information: Information that aids the flightcrew in determining the 

aircraft’s location in a given environment (for example, on flight plans, VORs, GPSs, features on 

the airport surface including taxiway, signage, etc.). 

hh. 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.” 

ii. Primary Flight Display (PFD): 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. 

jj. Primary Flight Information (PFI): 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. 

kk. Primary Function (PF): This definition is applicable in the case when there is more 

than one function available for same 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. For example, the PFD is a single physical unit that 

always provides the primary display and it complies with the requirements of all the following: 

altitude, airspeed, aircraft heading (direction) and attitude. This PFD is located directly in front of 

the pilot and used instantly and first by the pilot. A standby (additional) PFD that is intended to be 

used in the event of failure of the PFD is an example of a secondary system. 
11/17/2011 AC 23.1311-1C 

16 

ll. 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. 

mm. 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. 

nn. Reversionary Display: A secondary means to provide information initially 

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

oo. 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). 

pp. Secondary Display: A means to present information on another display. A display 

that can be used for backup or secondary purposes, such as in the event of a failure of another 

display. 

qq. Standby Instrument: A dedicated instrument that is always available that presents 

primary flight information. 

rr. Supplemental Function: A function that is not required or intended to meet all the 

airworthiness and operational requirements. It is usually installed for additional situational 

awareness. 

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

perform one or more functions. 

tt. Synthetic Vision System: A computer-generated image of the external scene 

topography from the perspective of the flight deck that is derived from aircraft attitude, high 

precision navigation solution, and database of terrain, obstacles and relevant cultural features. 

Note: “Topography” defined as maps or charts of natural and man-made 

features of a place or region especially in a way to show their relative 

positions and elevations, as applicable whenever deemed appropriate and 

practicable. 

uu. 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 23.1309-1E for the 

appropriate definitions. 

vv. Warning. A clear and unambiguous indication to the pilot of a failure that requires 

immediate corrective action. An inherent characteristic of the airplane or a device that will give 
11/17/2011 AC 23.1311-1C 

17 

clearly distinguishable indications of malfunction or misleading information may provide this 

warning. 

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. 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 CRTs, LCDs, electro luminescence, plasma, and LEDs. The initial electronic displays 

mimicked the traditional mechanical and electromechanical flight and powerplant instruments. The 

colors, symbols, and formats on these initial electronic displays are similar to those on traditional 

conventional instruments. Modern electronic displays provide integration and formats that often 

differ from traditional 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. For 

example, an integrated primary flight display provides several parameters such as attitude, heading 

(direction), airspeed, and altitude. Integration of various systems should include analysis to ensure 

that complexity and workload are compatible with general aviation pilots' capabilities. For more 

guidance on IMA that implement TSO authorized hardware elements, see TSO-C153 and AC 20-

170. 

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 parts 91, 121, and 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 parts 91, 121, and 135 may be 

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

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 a display as “SA-Only” and assume that its 

failure condition is acceptable. Installing displays that provide PFI that are more compelling than 
11/17/2011 AC 23.1311-1C 

18 

the required primary PFI displays, but they 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 23.1309-1E, AC 23-17C, and the guidance in this AC. 

8.2 Primary Flight Information (PFI). 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 presented, if available as a 

selectable option. The horizon reference line on the PFD should 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. The standby instrument or displays of PFI location should meet the FOV guidance 

criteria in section 15. 

8.2.1 Acceptable Methods for Compliance with § 23.1311(b). There are three 

acceptable methods for meeting the attitude requirements which is considered information essential 

for continued safe flight and landing. Compliance can be accomplished by using dedicated standby 

instruments, dual PFDs, or reversionary displays that present primary flight information. Electronic 

display systems without dedicated standby instruments should have at least two independent 

displays able to provide PFI 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 PFI from both 

displays. Section 23.1311(b) in Amendment 23-62 states: “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 be available 

within one second to the crew by a single pilot action or by automatic means for continued safe 

operation, after any single failure or probable combination of failures.” 

8.3 Standby Instruments. The purpose of standby instruments or another independent PFD 

is to ensure that PFI 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 

diameter of 3 inches (or equivalent) 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 AHRS with 
11/17/2011 AC 23.1311-1C 

19 

comparators and dual 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. 

8.3.2 PFD and Autopilot with an AHRS. For normal operation, when using a single 

AHRS to drive the PFD and the autopilot simultaneously, the installation must mitigate hazardous 

or catastrophic system level failures. An example configuration supporting proper mitigation would 

include all of the following: 

a. A dedicated standby attitude instrument within the primary maximum FOV or 

independent reversionary attitude display. 

b. An AHRS with appropriate comparator or monitor of equivalent performance. 

c. Appropriate system warning/caution annunciation associated with an AHRS 

malfunction. 

d. If an aircraft is equipped with multiple AHRS, it may be acceptable, when one 

AHRS fails, to drive both the autopilot and the PFD from a single AHRS as long as an AHRS 

independent attitude display (required for some aircraft classes) is located in the primary maximum 

field of view. The failure must be annunciated to the pilot, and the pilot must be able to select the 

non-failed AHRS. For aircraft that do not have an independent attitude indicator, when one AHRS 

fails, the autopilot should be manually or automatically disengaged. The autopilot may be 

reengaged if appropriate mitigation is available (for example, see a. through c. above). The AFM or 

supplemental AFM should contain the appropriate procedures applicable to the equipment 

installed. See section 11.0 for additional guidance. AC 23.1309-1E guidance should be considered 

for these configurations. 

e. Displays not meeting FOV guidance criteria may require additional human 

factors airworthiness evaluation by the certification authority. See section 15 for additional 

guidance. 

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 present PFI as needed to ensure continuity of 

operations. 14 CFR part 23, § 23.1311(b), Amendment 23-62, states 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 be 

available within one second to the crew by a single pilot action or by automatic means for continued 
11/17/2011 AC 23.1311-1C 

20 

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 could be 

automatically and manually selected or only manually selected. 

b. 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 format on the reversionary display of all PFI that is also shown 

on the PFD provides a significant safety enhancement over standby instruments. This is 

especially true when the size, location, arrangement, and information provided by the standby 

instruments are significantly different from those 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 single pilot action 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. However, the PFI should be 

presented in similar format and sufficient size in the reversionary mode as it is in normal mode to 

allow the pilot to enhance the control of the airplane. This reversionary configuration should 

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 optimum field of view. An acceptable method for the single pilot action 

is the red color and/or lighted red “halo” ring that announces its position on the panel at all times. 

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 availability meets the requirements of § 23.1309. If such a 
11/17/2011 AC 23.1311-1C 

21 

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

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

etc., should be similar as they were on the PFD before the failure. 

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

mode 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 on the 

MFD are accomplished before entering critical phases of flight. The PFI would be presented 

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. It is recommended that the display of attitude follows the guidelines (below) that are also 

in GAMA Publication #12. 

a. The pitch ladder should be caged to the center of the display. 

b. At pitch attitudes when the true horizon line would not normally be displayed, some 

sky or ground should be indicated on the PFD pitch display (minimum 3/8 inches and maximum of 

11.5 percent of the display), and the horizon line should indicate off-scale. 

c. With the airplane symbol on the horizon line, the range of visible pitch attitude should 

be at least + 25 to -15 degrees, but not to exceed a total pitch range of 50 degrees. 

d. Bank angle presentations should use a roll pointer; however, roll pointers and skypointers should not be mixed in the same flight deck/cockpit. 

e. Roll scale indices should be placed at 10, 20, 30, 60, and 90 degrees. An index may 

also be placed at 45 degrees. 

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 magnetic direction indicator or track may provide the reversionary display of 

direction. 
11/17/2011 AC 23.1311-1C 

22 

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 when track is presented, if available as 

a selectable option, with the data source clearly indicated. 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 from a human factor 

perspective.

8.6.2 Hazardous Misleading Heading Information. 

a. The FHA for the failure effects of hazardous misleading heading information 

from an AHRS is clarified in AC 23-17C. This policy is specifically about the application of AC 

23.1309-1E for an airplane with the certification basis of Amendments 23-41 or later. This 

clarification is limited to installations approved for operation in IMC under IFR. For operations 

limited to VFR, a misleading heading indication is not considered hazardous. 

b. Develop 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 23.1309-1E 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. The safety 

assessment process should consider appropriate mitigating factors. For Class I part 23 airplanes, 

the failure condition for misleading hazardous heading is usually considered major. 

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, pneumatically driven displays provided airspeed and altitude functions. 

Since then, the FAA envisioned airspeed, altitude, and magnetic compass information would remain 

available to the pilot with the loss of the airplane's primary electrical power. 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), as amended by Amendment 

23-62, requires an independent magnetic direction indicator and either an independent secondary 

mechanical altimeter, airspeed indicator, and attitude instrument or electronic display parameters 

for the altitude, airspeed, and attitude that are independent from the airplane's primary electrical 

power system. 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. 
11/17/2011 AC 23.1311-1C 

23 

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 operation, such as VFR or IFR. 

Under VFR operation, part 91, § 91.205, requires a magnetic direction indicator (that is normally 

intended to be a compass) for heading information. Under IFR operation, part 91, § 91.205, 

requires a gyroscopically stabilized heading system. Section 23.1303(c), Amendment 23-62, 

amended the requirement from “A direction indicator (non-stabilized magnetic compass)” to “A 

magnetic direction indicator.” As new technology becomes more affordable for part 23 airplanes, 

many electronic flight instrument systems will use magnetically stabilized direction indicators (or 

electric compass systems) to measure and indicate the airplane heading to provide better 

performance. 

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. 

8.8.2 Magnetic Non-Stabilized Direction Indicator. A magnetic non-stabilized 

direction indicator that is required by § 23.1303 should have an accuracy of 10 degrees or have a 

correction card, placard (reference § 23.1327), 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 presentation of 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 factors. 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 magnetic sensor. 

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 
11/17/2011 AC 23.1311-1C 

24 

systems, the comparator trip point, set as follows, would meet the requirements of part 23, 

§ 23.1301. 

(1) 6 degrees in stabilized level flight. 

(2) 6 degrees plus one half of the bank angle; or 

(3) 12 degrees with a bank angle greater than 6 degrees. 

(4) The alert function can be disabled at a bank angle greater than 20 degrees. 

(5) 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. 

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. The FAA suggests 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. 
11/17/2011 AC 23.1311-1C 

25 

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. There is a need 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 to set and monitor engine power within powerplant limitations. 

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

be in the AFM. 

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 

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 or engines such 

as with electronic engine controls featuring engine limit protection, the loss of powerplant displays 

should not cause immediate jeopardy to continued safe flight and landing. 

b. A secondary display providing powerplant parameters for cases of loss of a primary 

powerplant display may be used provided it is located so the pilot can adequately view the 

powerplant parameters. 

c. Throttle or power lever position may be used 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 the 

throttle has a means to preclude exceeding powerplant operating limits. 
11/17/2011 AC 23.1311-1C 

26 

9.3 Powerplant Information. 

a. Presentation of primary powerplant parameters continuously when they are required 

unless the monitor provides an adequate alert of the function. Also, provide a manual select option 

for the pilot to present the information. A parameter defined as primary for engine start, but not for 

other normal engine operation, may only have to be presented continuously during engine start. 

b. Before and upon reaching or exceeding any operating limit, the display should present 

the required powerplant parameters without pilot action. Timely alerts for each phase of flight 

should be provided when any operating limit is reached or exceeded for the required powerplant 

parameter. The alerts should be in a form that enables the pilot to identify and carry out the 

necessary and appropriate actions. The required powerplant information should be presented 

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 designed 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. See section 18 for more guidance on annunciation. 

9.4 Digital Reading Alphanumeric Displays. 

a. Digital reading alphanumeric displays are most valuable when integrated with an 

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

qualitative indication. Proper integration should include a means for pilots to clearly associate the 

analog and digital indications (e.g., via close proximity). Digital reading alphanumeric powerplant 

displays formats should not be used in place of analog formats to indicate values of engine 

parameters where trend or rate-of-change information is important for safety, or when the pilot 

needs to monitor parameters with a quick glance. Digital reading alphanumeric displays limit the 

pilot's ability to assess trend information and result in reduced crew awareness. Digital reading 

alphanumeric displays are also limited in their ability to allow the pilot to easily compare 

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 digital reading alphanumeric displays with caution and carefully evaluate each 

airframe, engine, and airframe/engine integration. 

b. Section 23.1311(a)(6), Amendment 23-62, requires sensory cues that provide a quick 

glance sense of rate and, where appropriate, trend information to the parameter being displayed to 

the pilot. Section 23.1311(a)(7) requires incorporated equivalent visual displays of the instrument 

markings required by §§ 23.1541 through 23.1553 or visual displays that alert the pilot to abnormal 

operational values or approaches to established limitation values, for each parameter required to be 

displayed by this part. 
11/17/2011 AC 23.1311-1C 

27 

c. An ELOS will be necessary for digital -reading alphanumeric only displays that are not 

associated with any scale, tape, or pointer. It may be difficult for pilots to determine the margin 

relative to targets or limits, or compare between parameters. To comply with § 23.1311(a)(7), a 

scale, dial, or tape will be needed to accomplish the intended pilot task. In order to demonstrate an 

equivalency, a human factor and/or pilot evaluations will be needed that will consider the following 

factors. These are subject to evaluation on a case-by-case basis. 

(1) The visibility and relative location of the indicated parameter should be reviewed, 

including appropriate conditions of lighting and instrument panel vibration. 

(2) The ability to assess necessary trend or rate-of-change information quickly, 

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

(3) The ability to assess how close the indicated parameter is relative to a limit. 

(4) The value to the crew of quickly and accurately comparing engine-to-engine data 

for multiengine aircraft. 

(5) Engine design features or characteristics that would forewarn the crew before the 

parameter reaches the operating limit (for example, redline). 

(6) The use of color in accordance with § 23.1549 to indicate the state of operation: a 

green indication would indicate normal operation, a yellow indication would indicate operation in a 

takeoff or precautionary range, and a red indication would indicate operation outside of the safe 

operating limits. 

9.5 Marking of Powerplant Parameters. Mark powerplant parameters on electronic displays 

in accordance with § 23.1549. AC 20-88A provides alternate methods of marking electronic 

powerplant displays. Alternate methods of marking the displays may be performed. However, the 

FAA may evaluate these markings on a case-by-case basis depending on each airframe, engine, 

integration, and appropriate human factors considerations. Alternate markings that do not comply 

with the requirements of § 23.1549 require an ELOS. 

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 FOV. Warnings 

and cautions should also be in the primary FOV. For more guidance on FOV, see section 15 and 

Table 3 of this AC. 

10.2 Display Integration. 

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

examples include HSIs that combine inputs from a directional gyro with a course deviation 
11/17/2011 AC 23.1311-1C 

28 

indicator, or an FD integrated with the 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 presented, the selected 

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

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

source and which one has been selected for guidance. Some airplanes are equipped with an 

autopilot and/or FD coupled to the lateral and vertical guidance system. On these airplanes, the 

input to the autopilot and/or FD 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 following AC 23.1309-1E. For more guidance on safety 

assessments, see AC 23.1309-1E 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 20-138 and AC 20-153 for more guidance and information. 

11.0 Aircraft 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 23-8C contains more policy and guidance on 

AFMs. 

12.0 Electronic Checklist and Charts. Policy and guidance on electronic checklist and charts on 

electronic displays are contained in AC 23-8C, AC 91-78, AC 120-64, and AC 120-76A. 

13.0 General Human Factors Considerations for Design of Electronic Displays. 

13.1 General. Electronic displays can provide many innovative display flexibilities and 

features that were not possible with traditional displays. 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. The FAA encourages the applicant to develop human 

performance considerations, including evaluation plans, and present them to the FAA early in the 

certification process. 
11/17/2011 AC 23.1311-1C 

29 

13.2 Human Factors for Certification of the Part 23 Small Airplanes. Policy statement 

number PS-ACE100-2001-004 provides guidance for 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. 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 GAMA 

Publication No. 10 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 

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

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

b. The applicant should 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.). 

(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. 
11/17/2011 AC 23.1311-1C 

30 

c. Manufacturers should provide design rationale for their decisions regarding new or 

unique features in a display. Evaluation should be conducted to collect data in support of the new 

or unique features to assure they have no unsafe or misleading design characteristics. The design 

teams, including pilots, should concur with the conclusion found with the data collected. 

d. The applicant should conduct display evaluations with several human factors and 

pilots representatives whom are intended users 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 AC before the evaluation. Evaluators should also be 

familiar with human factors display regulations, guidance, standards, and recommendations 

contained under sections 3. 

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 its 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, applicants should 

elaborate on a statement that a new display system is intended to “enhance 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. Applicants should 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 major pilot 

interfaces focusing on new or unique features that affect the pilot interface. A system may have 

multiple intended functions, provided each function is documented and all information depicted or 

indicated to the pilot supports one or more of the documented intended functions. See PS-ACE100-

2001-004 paragraph 2.a., Intended Function, for more guidance. 

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

intended function and associated task is sufficiently specific and detailed. 
11/17/2011 AC 23.1311-1C 

31 

(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? 

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. Displays should be located such that 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. The basic T-configuration should be used for airplanes 

certificated under § 23.1321, Amendment 23-14, or a later amendment. The basic T-configuration 
11/17/2011 AC 23.1311-1C 

32 

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 level of safety, and a human factors evaluation 

are 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; 

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

(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.” 
11/17/2011 AC 23.1311-1C 

33 

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

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

(1) Readability; 

(2) Clutter; 

(3) Pilot scan pattern; 

(4) Pilot workload; 

(5) Parallax; 

(6) Frequency of use and criticality; 

(7) Attention-getting; 

(8) Out-the-window correlation; 

(9) Pilot disorientation; and 

(10) Illumination and glare. 

15.2 Primary Field-of-View. Primary optimum FOV 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 3 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 FOV. 

15.3 Primary Maximum Field-of-View. Primary maximum FOV 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. A 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 3 provides examples of information recommended for inclusion in 

this visual field. 
11/17/2011 AC 23.1311-1C 

34 

Figure 1. Primary Field-of-View 

15.4 Recommended Location for Displaying Information. Table 3 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 3. These deviations may need an evaluation by the 

certification authority. Factors to consider during this evaluation include the distinguishing ability, 

attention-getting quality, readability, etc. The FOV 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 3 should be used. 
11/17/2011 AC 23.1311-1C 

35 

Table 3 – Field-of-View 

Data Recommended Field-of-View 

FOV, Degree 

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 

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, and 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 annunciations should be within 15 degrees. Some 

annunciations may be acceptable within 35 degrees if they are associated with a unique 

aural tone or a master warning/caution annunciations that is within 15 degrees and with 

a pilot evaluation. 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. 

Note 5. Install the standby instruments as close as practicable to the PFI. 
11/17/2011 AC 23.1311-1C 

36 

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. TSO-C113 and 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 endof-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 in-flight 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 

be positioned with sufficient accuracy to avoid interpretation errors or significantly increase 

interpretation time. Symbols should not have shapes, colors, or other attributes that are ambiguous 

or could be confused with the meaning of similar symbols. Symbols that represent physical objects 

(for example, navigational aids and traffic) should not be misleading as to the object’s physical 

characteristics (including position, size, envelope, and orientation). 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. The shape, dynamics, and other 

symbol characteristics representing the same function on more than one display on the same flight 

deck should be consistent. 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. 

17.2 Symbol Standards. Symbols should be based on established industry standards. The 

symbols in the following SAE documents have been found to be acceptable for compliance to the 

regulations: SAE ARP 4102/7, ARP 5289, and SAE ARP 5288. For example, the use of flashing 

letters, such as an “X,” should be consistent. One benefit of symbol standards versus other 
11/17/2011 AC 23.1311-1C 

37 

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 Declutter of the PFD. 

a. All primary attitude displays should provide an immediately discernible 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 PFI. 

b. The PFD may require an automatic declutter function during unusual attitudes. 

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

airplane performance. 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. Flight guidance displayed to assist in unusual attitude recovery 

should be red and point to the correct direction for proper recovery. SVS information on the display 

may need to be removed if the attitude source is no longer available. See AC 20-167 for additional 

guidance on removing SVS information. 

Note: Not applicable to aerobatic category airplanes. 

17.5 Digital Read-Out Alphanumeric-Only Display of Airspeed and Altitude. Digital 

read-out presentation of airspeed and altitude should convey to the pilot a quick-glance sense of rate 

and trend information. For airspeed and altitude, digital read-out alphanumeric displays may not be 

adequate on the primary display or on the standby instruments, but it is acceptable on a display used 

as supplementary information. If the applicant proposes a digital read-out 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. 
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38 

17.6 Round Dial and Moving Scale Display. The display of a round dial, moving pointer 

with a digital read-out 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 (Linear Tape Displays). 

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, 

provide 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 should 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. 
11/17/2011 AC 23.1311-1C 

39 

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

yellow band is discouraged (due to clutter) for twin-engine airplanes that incorporate a red and blue 

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

Red 

Yellow 

Green 

Red 

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

Blank or optional yellow 

arc 

VS1 

VSO 

VNE 

VNO 

VFE 
11/17/2011 AC 23.1311-1C 

40 

17.7.2 VMO Airplanes. The applicant should 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. 

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

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

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

previously approved. 

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

Red 

Black 

Red 

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

Blank or optional 

yellow arc 

Note: On commuter category 

airplanes, bugs should be 

provided for setting V1 and 

V2 This is a blank 

area 

represented by 

a black arc. 

VMO

VFE

VS1

VSO
11/17/2011 AC 23.1311-1C 

41 

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. 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 direct the 

pilot’s attention away from looking out the window or fixating on flight or navigation displays such 

as the FD 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 direct the pilot’s attention using 

peripheral vision. Another example is to display an 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 Vertical Speed Indicator 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. GAMA 

Publication No. 12, “Recommended Practices and Guidelines for an Integrated Flightdeck/Cockpit 

in a 14 CFR part 23 (or equivalent) Certificated Airplane,” is 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 one another. GAMA Publication 

No. 12 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 
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42 

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 certification process 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 there are multiple depictions, such as inset, inlays, or overlayed depictions, the 

orientation (for example, heading up, track up, North up, etc.) should be the same for each 

depiction. This does not apply to other systems where the pilot and copilot may select different 

presentations of the same information and are used exclusively by that pilot. For more information, 

see TSO-165. 

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 number of overlays should not cause the information displayed to become unusable through 

cluttering or obscuration. Combinations of multiple data presentations should 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 should not occur. Provide map range. 
11/17/2011 AC 23.1311-1C 

43 

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. 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. Using the display selection control position as annunciation is 

acceptable only under certain conditions. For the flight director, it is acceptable if the control 

position is appropriately labeled to indicate the function. The control position should be in direct 

view of the pilot and it should be obvious under all lighting conditions. When a failure occurs or 

when using reversionary modes, an annunciation of abnormal system status must be provided, in 

accordance with § 23.1311(a)(7). The display is not to provide any misleading information. 

Evaluate annunciations that require pilot 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 misleading to 

the pilot using the system. Labels for mode and source selection annunciators should be compatible 

throughout the cockpit. To ensure the pilot 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. 

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 pilot. Prioritization of warnings and caution 

alerts such as TAWS, Predictive Windshear System (PWS), 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 alert schematic. Prioritize systems 

information displayed on the MFD to allow ready access to critical information. Less critical 
11/17/2011 AC 23.1311-1C 

44 

information may be less accessible. Provide a means for the pilot to select higher priority 

information as needed with a single entry on the MFD control panel or keypad. 

18.5 Visual Alerts for Warnings. Visual alerts for 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 ND, although weather and terrain cannot be displayed at the 

same time in many current designs. A threat should trigger an automatic pop-up and the 

appropriate display on the ND, as well as the appropriate aural alert. Subsequent alerts of a higher 

priority may override the visual display, but the active aural alert should finish before another aural 

alert of equal or less urgency begins. However, active alerts should be interrupted by alerts from 

higher urgency levels if the delay to annunciate the higher-priority alert impacts the timely response 

of the pilot(s). When multiple alerts exist in the same category (for example multiple warning 

alerts), a means for the pilot to determine the most recent or most urgent should be provided. 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. The electronic display should clearly annunciate and/or display any 

exceedance to the pilot in the appropriate color, following §§ 23.1322 and 23.1549. The 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. 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. 
11/17/2011 AC 23.1311-1C 

45 

20.0 Controls. 

a. 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 be intuitive, that is, so the pilot can rapidly, accurately identify, and select all of the functions of 

the display control. 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. 

b. Soft controls and cursor control devices development assurance levels should be 

commensurate with the level of criticality of the airplane system they will control. Redundant 

methods of controlling the system may lessen the criticality required of the display control. The 

final display response to control input should be fast enough to prevent undue concentration being 

required when the pilot sets values or display parameters. The applicant should show by test and/or 

demonstration in representative motion environment(s) (for example, turbulence) that the display 

control is acceptable for controlling all functions that the pilot may access during these conditions. 

21.0 Test Functions. The electronic display should incorporate a pilot selectable or automatic test 

mode, such as built in testers, that exercise 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 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. See TSO-C113 and TSO-C63 for additional 

guidance, 
11/17/2011 AC 23.1311-1C 

46 

22.2 Color for Display Features. Color code display features should be as indicated in the 

table below: 

Table 4 – Color for Display Features

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 as indicated in the table 

below: 

Table 5 – Color Sets 

 Color Set 1 Color Set 2

 

Fixed reference symbols, that 

is, lubber lines 

White Yellow*1

Current data, values White Green 

Armed modes White Cyan 

Selected data, values Green Cyan 

Selected heading Magenta**2 Cyan 

Active route/flight plan Magenta White 

*1 The extensive use of the color yellow for other than caution/abnormal information is 

discouraged. 

**2 In color set 1, magenta is associated with those analog parameters that constitute "fly to" 

or "keep centered" type information. 
11/17/2011 AC 23.1311-1C 

47 

22.4 Color for Depiction of Weather Precipitation and Turbulence. The depiction of 

weather precipitation and turbulence should be coded as indicated in the table below: 

Table 6 – Color for Depiction of Weather Precipitation and Turbulence 

Precipitation 0-1 mm/hr Black 

 

1-4 mm/hr Green 

4-12 mm/hr Amber/Yellow 

12-50 mm/hr Red 

Above 50 mm/hr Red or Magenta 

Turbulence mm/hr White or Magenta 

Icing mm/hr Light Blue 

 

Note: 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 pilot recognition is required, and 
11/17/2011 AC 23.1311-1C 

48 

immediate correction or compensatory action may be required. Use amber for the cautionary 

annunciation for abnormal operating conditions when immediate pilot awareness is required, and 

subsequent pilot action may be required. Use white or another unique color for advisory 

annunciations of operating conditions that require pilot awareness and, possibly, action. Use green 

for indication of safe operating conditions. 

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. 

22.9 Color for Aviation Routine Weather. For electronic color graphic display of aviation 

routine weather to surface meteorological data see TSO-C157 and AC 20-149 for guidance. 

23.0 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 TSO-C113, 

and 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 assessments if they show that the TSO requirements apply to the installation. 

24.0 Aircraft Electrical Power Source. 

24.1 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. 

24.2 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/DO-160 for momentary power interruptions should be appropriate for the 

intended use. RTCA/DO-160 provides information that may be used for an acceptable means of 

qualifying display equipment such that they perform their intended function when subjected to 

anomalous input power. 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. 

24.3 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 power source of the primary display, such as a second alternator or battery. 
11/17/2011 AC 23.1311-1C 

49 

b. Section 23.1331(c), Amendment 23-62, requires, for certification of IFR operations 

and for the heading, altitude, airspeed, and attitude, there must be at least: 

(1) Two independent sources of power (not driven by the same engine on 

multiengine airplanes), and a manual or an automatic means to select each power source; or 

(2) A separate display of parameters for heading, altitude, airspeed, and attitude that 

has a power source independent from the airplane's primary electrical power system. 

c. Section 23.1353(h), Amendment 23-62, requires, in the event of a complete loss of 

the primary electrical power generating system, the battery must be capable of providing electrical 

power to those loads that are essential to continued safe flight and landing for: 

(1) At least 30 minutes for airplanes that are certificated with a maximum altitude of 

25,000 feet or less, and 

(2) At least 60 minutes for airplanes that are certificated with a maximum altitude 

over 25,000 feet. 

Note: The time period includes the time to recognize the loss of generated power and to 

take appropriate load shedding action. 

d. 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. The aircraft battery used for starting may satisfy the requirements of 

§ 23.1353(h) provided its adequacy is shown through a system safety analysis under § 23.1309. In 

this case, an ELOS may be required; AC 23-17C provides more guidance. 

e. 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 power 

generation sources for the primary and reversionary or standby displays for single engine airplanes 

if there is a different dedicated source. 

f. 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 singleengine 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. 
11/17/2011 AC 23.1311-1C 

50 

25.0 Safety Assessments. 

25.1 Regulations Before and After Amendment 23-41. Part 23 regulations issued 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 and later, allowed approval of more advanced and complex systems. Amendment 23-41, and 

later, also incorporated § 23.1311 into part 23, which provides the standards for electronic 

displays. 

25.2 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 be 

available within one second to the crew by a single pilot action or by automatic means 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 that should be considered are attitude, airspeed, altitude, warnings and any 

applicable propulsion parameter(s). Common-mode failures should be addressed. See AC 

23.1309-1E for more guidance. 

25.3 Safety Analysis. 

a. AC 23.1309-1E 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 the display and control systems. The FHA identifies the failure conditions 

for all display functions, analyzes the effects on the aircraft and pilot, 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. 
11/17/2011 AC 23.1311-1C 

51 

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 pilot is required to test a system 

before each flight, assume, for the safety analysis, the pilot will accomplish this test at least once a 

day, providing the preflight test is conveniently and acceptably implemented. 

26.0 Software and Hardware Development Assurance. 

26.1 General. Applicants must show compliance with § 23.1309, regardless of the intended 

function of the display system. The equipment should 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 23.1309-1E, 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. 

26.2 Software Guidance. 

26.2.1 General. AC 20-115B addresses 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 ACO. 

26.2.2 Software Levels. Determine all software levels by appropriate safety 

assessments (see AC 23.1309-1E, Figure 2) and any more requirements, such as those specified by 

functional TSOs. 

26.2.3 Field-Loadable Software (FLS). Many electronic displays systems use FLS as 

part of the TC/ATC/STC/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 20-170. 

26.3 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 AC 23-1309-1E, 8110.105 CHG 1, and AC 20-152, which addresses how to 

use RTCA/DO-254. These documents provide acceptable means for showing that complex 

hardware complies with the pertinent airworthiness requirements. Determine the hardware levels 

for all hardware by the appropriate safety assessments (see AC 23.1309-1E, Figure 2) and any more 

requirements, such as those specified by functional TSOs. 
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52 

27.0 Environmental Conditions. 

27.1 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/DO-160F. Either test or analysis, or both, ensures the 

compatibility between the operational environment and the environmental equipment category of 

the laboratory tests. 

27.2 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. 

27.3 Attitude Information. It is recommended that attitude information continue to be 

presented for a minimum of 30 to 60 minutes after the in-flight 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. The applicant should consider automatic 

over-temperature shutdown of the system a failure condition. The subsequent pilot actions should 

be documented 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. 

27.4 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 over-temperature 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 catastrophic failure condition, install fan monitors or another method to 

determine the status of the cooling fan during preflight checks. 

28.0 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 20-136A, AC 20-155, AC 20-158, 

AC 23.1309-1E, and AC 23-17C provide more guidance for lightning and HIRF protection.
11/17/2011 AC 23.1311-1C 

53 

29.0 Electromagnetic Interference. The electronic display instrument system should not be the 

source of detrimental conducted or radiated interference. Conducted or radiated interference from 

other equipment or systems installed in the airplane should not adversely affect the displays. 

30.0 Implosion Protection. Design and construct the display unit to prevent implosion when the 

unit is operating over the range of normal and abnormal operating environments 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 pilot 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) as specified by RTCA/DO-160F. 

Similarity of a particular display to a unit already tested may be used to comply with this 

requirement. 

31.0 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 20-170 for 

more guidance.