Subject: SMALL AIRPLANE 

 CERTIFICATION COMPLIANCE

 PROGRAM

Date: 12/30/03

Initiated By: ACE-100 

AC No: AC 23-15A

Change:

1. PURPOSE. This advisory circular (AC) provides a compilation of historically acceptable means 

of compliance to specifically selected sections of 14 CFR part 23 that have become burdensome for 

small, simple, low performance airplanes (see Applicability section below) to show compliance. 

However, applicability of these means of compliance remains the responsibility of the certification 

manager for each specific project. Utilization of these means of compliance does not affect the 

applicability of any other certification requirements that fall outside the scope of this AC. This 

material is neither mandatory nor regulatory in nature and does not constitute a regulation. 

a. Applicability: Small, Simple, Low Performance Airplanes – The subject of this AC. The 

terms “small airplane”, “simple airplanes”, or “small low performance airplanes”, used throughout 

this AC, are synonymous with “Small, Simple, and Low Performance Airplanes”. This AC is 

applicable to airplanes with the following characteristics:

• Single reciprocating engine (Part of CLASS 1 definition in AC 23.1309-1C) 

• Less than 6,000 pounds (part of CLASS 1 definition in AC 23.1309-1C) 

• 4 Seats or less including pilot and co-pilot seats 

• Unpressurized fuselage 

• Normal category maneuvers only (see part 23, §§ 23.3(a)(1) through 23.3(a)(3) for 

definition of “normal category maneuvers”) 

• Conventional materials and techniques – i.e. wood, aluminum monocoque/semimonocoque or tubular steel design, and no composite (i.e. graphite/epoxy), primary 

structure 

• Primary structure (as used above) is that structure which contributes significantly to 

resisting or transmitting flight or ground loads, or may lead to an unsafe condition if 

failed. Some examples (not an exhaustive list) of primary structures are:

(1) Fuselage frames, stringers and skins 

(2) Wing, horizontal stabilizer and vertical stabilizer spars, ribs, and skins 

(3) Bulkheads 

(4) Intercostals 

(5) Door and window edge frames, sills, or posts 
AC 23-15A 12/30/03 

ii 

(6) Landing gear and their attachments 

(7) Engine Mounts

NOTE 

There may be instances where a portion of structure is not clearly 

“primary structure” and thus will require the judgment of the 

Aircraft Certification Office (ACO) engineer. 

• No unique, un-orthodox, or complex design features in this context: 

(1) A “unique” design feature is something that the current regulations may not 

adequately address. 

(2) An “un-orthodox” design feature is something that is not typically seen in an 

airplane of this type, for example, and canard or forward swept wing. 

(3) A “complex” design feature is not the same as a complex airplane (defined below). 

Precisely what constitutes a complex design feature is a determination that can only 

be made based on the judgment of the ACO engineer. As a rule of thumb, if a 

design feature is difficult (from the perspective of an engineer experienced in their 

field) to understand, analyze, reliably predict the behavior of, or prone to failures 

(due to complexity), that may create an unsafe condition, then it may be deemed as 

“complex” 

• Engine is 200 Horsepower (HP) or less. NOTE: Airplanes with engines over 200 HP 

are “high-performance” under Title 14 Code of Federal Regulations, part 61, § 61.31 (f). 

• The airplane may have no more than 2 of the following 3 items. NOTE: An airplane 

having all 3 of the following items are “complex” under Title 14 Code of Federal 

Regulations, part 61, § 61.31(e). 

(1) Retractable Landing Gear 

(2) Flaps 

(3) Controllable pitch propeller 

• No wing, leading edge, high lift devices. 

• For airplanes equipped with trailing edge wing flaps, the design should be a simple, 

standard design, such as “plain”, “split”, “fowler”, or “single slotted”. 

b. This AC applies only to these types of aircraft. However, certification requirements must 

always be coordinated with the local ACO. The ACO will make the determination of the suitability 

of this AC, based on a review of the aircraft design. It is always within the applicants right to 

propose the use of this AC to show compliance, and to negotiate this with the ACO. 

2. CANCELLATION. AC 23-15, Small Airplane Certification Compliance Program, dated 

January 2, 1997, is cancelled. 

s/ 

James E. Jackson 

Acting Manager, Small Airplane Directorate 

Aircraft Certification Service 
12/30/03 AC 23-15A 

iii 

CONTENTS 

Section Page

 1. Purpose............................................................................................... i

 2. Cancellation ....................................................................................... i 

 3. Related Regulations And Documents................................................ 1 

 4. Background........................................................................................ 3 

 5. Acceptable Method Of Compliance .................................................. 4 

LIST OF ILLUSTRATIONS 

Figure Page 

 1. Sighting Bars Spaced Along Runway................................................ 6 

 2. Formula to Determine Height of the Aircraft Above Runway .......... 6 

 3. Takeoff Data Installation for Swiveling Camera or Recording 

 Theodolite ....................................................................................... 7 

 4. Typical Chart and Takeoff Graph...................................................... 7 

 5. Fixed Grid.......................................................................................... 8 

 6. Corrected Takeoff Data ..................................................................... 8 

 7. Determination Of Standard S.L. Takeoff Distance Segment Method 

 (Acceleration Segment) .................................................................. 9 

 8. Determination of Takeoff Distance to 50 Feet at Given Altitude and 

 Temperature.................................................................................... 11 

 9. Data Reduction Form Climbs – Equivalent Altitude Method .......... 13 

 10. Data Reduction Form Climbs-Density Altitude Method................... 15 

 11. Data Reduction Form-Correction of Landing Data to Standard 

 Conditions....................................................................................... 19 
AC 23-15A 12/30/03 

iv 

LIST OF ILLUSTRATIONS (Continued) 

Figure Page 

 12. Normal Category Spin Test Matrix ................................................... 24 

 13. Performance Content And Format..................................................... 34 
12/30/03 AC 23-15A 

1 

3. RELATED REGULATIONS AND DOCUMENTS. 

 a. Regulations: Title 14, Code of Federal Regulations (CFR), Part 23: 

 Section 23.45 Performance: General. 

 Section 23.51 Takeoff speeds. 

 Section 23.65 Climb: All engines operating. 

 Section 23.75 Landing distance. 

 Section 23.77 Balked landing. 

 Section 23.145 Longitudinal control. 

 Section 23.161 Trim. 

 Section 23.175 Demonstration of static longitudinal stability. 

 Section 23.201 Wings level stall. 

 Section 23.203 Turning flight and accelerated turning stalls. 

 Section 23.207 Stall warning. 

 Section 23.221 Spinning. 

 Section 23.562 Emergency landing dynamic conditions. 

 Section 23.605 Fabrication methods. 

 Section 23.629 Flutter. 

 Section 23.641 Proof of strength. 

 Section 23.677 Trim systems. 

 Section 23.723 Shock absorption tests. 

 Section 23.725 Limit drop tests. 

 Section 23.726 Ground load dynamic tests. 

 Section 23.727 Reserve energy absorption drop test. 

 Section 23.735 Brakes. 

 Section 23.853 Passenger and crew compartment interiors. 

 Section 23.865 Fire protection of flight controls, engine mounts, and other 

 flight structure. 

 Section 23.867 Electrical bonding and protection against lightening and static 

 electricity. 

 Section 23.954 Fuel system lightning protection. 

 Section 23.965 Fuel tank tests. 

 Section 23.1301 Function and installation. 

 Section 23.1309 Equipment, systems, and installations. 

 Section 23.1311 Electronic display instrument systems. 

 Section 23.1337 Powerplant instruments installation. 

 Section 23.1431 Electronic equipment. 

 Section 23.1581 Airplane Flight Manual and Approved Manual Material- 

 General. 

 Section 23.1585 Operating procedures. 

 Section 23.1587 Performance information. 
AC 23-15A 12/30/03 

2 

b. Advisory Circulars. 

 AC 20-53A Protection of Aircraft Fuel Systems Against Fuel Vapor 

 Ignition Due to Lightning 

 AC 20-115B Radio Technical Commission for Aeronautics, Inc., 

 Document RTCA/DO-178B 

 AC 20-121A Airworthiness Approval of Loran-C Navigation Systems for 

 use in the U.S. National & Airspace System (NAS) and Alaska 

 AC 20-130A Airworthiness Approval of Navigation or Flight Management 

 Systems Integrating Multiple Navigation Sensors 

 AC 20-135 Powerplant Installation and Propulsion System Component 

 Fire Protection Test Methods, Standards and Criteria 

 AC 20-136 Protection of Aircraft Electrical/Electronic Systems against 

 the Indirect Effects of Lightning 

 AC 21-22 Injury Criteria for Human Exposure to Impact 

 AC 21-40 Application Guide for Obtaining a Supplemental Type 

 Certificate 

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

 AC 23-11A 14 CFR Part 23 Type Certification of an Airplane Originally 

Certificated to Joint Aviation Regulations - Very light Airplane 

(JAR-VLA) Standards 

 AC 23-16 Powerplant Guide for Certification of Part 23 Airplanes 

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

Airplanes 

AC 23.562-1 Dynamic Testing of Part 23 Airplane Seat/Restraint Systems 

and Occupant Protection 

 AC 23.629-1A Means of Compliance with Section 23.629, “Flutter” 

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

 AC 23.1311-1A Installation of Electronic Displays in Part 23 Airplanes 
12/30/03 AC 23-15A 

3 

 Airframe and Aircraft Simplified Flutter Prevention Criteria for Personal Type 

 Equipment Engineering 

 Report (AEER) No. 45 

 FAA Technical Report Aircraft Lightning Protection Handbook 

 DOT/FAA/CT-89/22 

(1) The AC's listed above (with the exception of AEER No. 45) can be obtained from the 

U.S. Department of Transportation, Subsequent Distribution Office, Ardmore East Business Center, 

3341 Q 75th Avenue, Landover, MD 20785. 

(2) AC's 21-40, 23-17A, and 23-8A are for purchase and can be obtained from the 

Superintendent of Documents, P.O. Box 371954, Pittsburgh, PA 15250-7954, or from any of the 

Government Printing Office bookstores located in major cities throughout the United States. 

(3) All of the above AC's (with the exception of AEER No. 45 and the technical report) are 

also available free of charge in electronic format from the FAA's Aircraft Certification Service web 

page, located at the following Internet address: http://www.faa.gov/certification/aircraft/. 

(4) AEER No. 45 is available from: Manager, Standards Office (ACE-110), Federal 

Aviation Administration – Small Airplane Directorate, 901 Locust, Room 301, Kansas City, MO 

64106 or on the Internet at: http//www.faa.gov/certification/aircraft/aceAEER45-Flutter.pdf. 

(5) Technical Report DOT/FAA/CT-89/22 is available by order through the National 

Technical Information Service, Springfield, Virginia 22161 

 c. Industry Documents. The Radio Technical Commission for Aeronautics (RTCA) documents 

listed below are available from the RTCA, Inc., suite 805, 1828 L Street NW, Washington, DC 

20036-4001 or at their website at www.rtca.org: 

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

 Equipment 

 RTCA/DO-178B Software Consideration in Airborne Systems and Equipment 

 Certification 

4. BACKGROUND. Some industry and aviation organizations expressed concern that the typical 

means of compliance for some regulations might be more demanding than justified. As a 

consequence, industry, aviation groups, and the Federal Aviation Administration (FAA) formed a 

team to study this issue. Historical files, Designated Engineering Representatives (DER's), ACO's, 

and industry were used to determine target regulations and provide known means of compliance. 

This AC is a compilation of the study results, listing the regulations and attendant means of 

compliance that offer an improvement in certification efficiency. The listed means of compliance 

have been found acceptable and historically successful, but they are not the only methods, which can 

be used to show compliance. 
AC 23-15A 12/30/03 

4 

5. ACCEPTABLE METHOD OF COMPLIANCE. The selected methods of compliance are 

organized by affected sections of part 23. 

 a. Performance - General. 

(1) Regulations Reference. Sections 23.45 and 23.1587. 

 (2) Discussion. Section 23.45(e), requires that performance data for compliance 

demonstration be based on engine power at 80 percent humidity. The rule also addresses approved 

power or thrust reduced by maximum installation losses and accessory power extraction. This 

advisory material is provided for application to small airplanes to address these issues as follows: 

 (a) Humidity Adjustment. 

1. Subsections 23.45(e) requires that performance data for flight requirements 

compliance demonstration (and for performance information included in the Airplane Flight Manual 

(AFM) under § 23.1587) be based on engine power at 80 percent relative 

humidity. Based on AC 23-8B, appendix 1, paragraph 2d(3), no humidity correction is required for 

small airplanes. This paragraph states that, "Experience has shown that conditions such as 

80 percent relative humidity on a standard day at sea level has a very small effect on engine 

power...." "Standard" atmospheric conditions referenced in § 23.45 means United States Standard 

Atmosphere. See AC 23-8B, paragraph 16a(2). 

2. The need for detailed and accurate performance data is closely related to the 

airplane stall speed. An airplane that has a stall speed of 30 knots and a takeoff roll of 200 feet 

requires no takeoff performance data because the pilot’s visual judgment is adequate and more 

convenient. An error of 10 percent is only one fuselage length. For an airplane with a 130-knot stall 

speed, the ground distances are great enough to be beyond the pilot's visualization and judgment. 

The runway length and airplane requirements are closely related. Making a 10 percent error is the 

difference between a successful rejected takeoff (RTO) and terminating off the airport. Airplanes of 

this performance level require detailed and accurate data for even routine operation. Small, simple, 

low performance airplanes do not require that same level of detail and accuracy in order to show 

compliance to the regulations. Therefore, the small error in performance data based on dry air won’t 

have a significant affect (for small, simple, low performance airplanes). 

 (b) Engine Power Losses. The rule contains language regarding "approved power or 

thrust" reduced by maximum installation losses and accessory power extraction. For small 

airplanes, the prime losses pertaining here are those associated with induction and exhaust systems; 

the typical accessories that extract power are the electrical and vacuum systems. Since all testing is 

accomplished with the intake and exhaust systems installed on the airplane, no further corrections 

for losses are applicable. The typical electrical power source, an alternator, on small airplanes 

(12 volts at a maximum capacity of 60 amps) will consume less than one horsepower maximum. 

Testing is normally done with the electrical system on, thereby reducing any potential power 

correction for the alternator's power extraction to much less than one horsepower. Vacuum 

pumpsextract approximately one-half horsepower. They typically run all the time and would be 

expected to be operating during performance testing and, therefore, no correction for vacuum power 

extraction is warranted. Also, because of the difficulties associated with power determination when 
12/30/03 AC 23-15A 

5 

using fixed pitch propellers, the best approach is to use full throttle setting for takeoff and climb 

performance testing 

(c) Test Instrumentation. 

1. For measurement of altitude, airspeed, and temperature, a measurement device, 

such as that developed for the Comparative Aircraft Flight Efficiency, Inc. (CAFE) Triaviathon, will 

be an acceptable means of generating required data for measuring rate of climb, climb gradient, 

glide gradient, airspeed, balked landing criteria, etc. (CAFE Foundation, 4370 Raymonde Way, 

Santa Rosa, CA 95404) 

2. This device records indicated airspeed, true airspeed, mean sea level (MSL) 

altitude, and outside air temperature once per second into a computer memory. It then performs all 

corrections and calibrations necessary. Video cameras may also be used to record instrument 

readings and pilot actions to show compliance with flight and performance provisions. Also, the use 

of traditional equipment such as knee pad, stopwatch, force gauge, etc., is appropriate for many tasks 

and their use is encouraged. 

 b. Takeoff. 

 (1) Regulations Reference. Sections 23.53 and 23.1587. 

 (2) Discussion. 

 (a) Measurement Methods. Section 23.51(a) requires the measurement of the distance 

required to takeoff and climb over a 50-foot obstacle. AC 23-8B, 19.b, describes acceptable 

methods of compliance. To avoid any inference that expensive test equipment is required, this 

advisory material provides additional guidance specifically applicable to small airplanes. 

 (b) Distance and Height Measurements and Equipment. Measurements should be taken 

to determine the distance from the takeoff starting point to the place where the aircraft leaves the 

ground and to the point where the airplane reaches the height of 50 feet. These measurements may 

be made in various ways. A few of the acceptable methods in general use follow: 

1. When space-positioning equipment is not available, either of the following 

systems may be used. The first consists of several theodolites (sighting bars) spaced along the 

runway so as to cover the distance and time from takeoff point to the simulated 50-foot obstacle. 

The distance and time from takeoff point to each sighting station will give an approximation of the 

aircraft speed and takeoff distance. This method is shown schematically in figure 1. 
AC 23-15A 12/30/03 

6 

Figure 1 – SIGHTING BARS SPACED ALONG RUNWAY 

(aa) It is good practice to station two or three observers at the edge of the 

runway in the vicinity of the takeoff point to mark the exact point of takeoff. The data obtained by 

such observers are always a good check on ground roll distance regardless of the method used for 

obtaining data. Additionally, the error in visually determining the takeoff point may be minimized 

by making a series of lime lines on the runway at 5 to 10-foot intervals in the expected takeoff zone. 

The transit should be tilted so that the plane of rotation of the sight intersects the vertical plane of the 

runway centerline at 50 feet. (The height of the aircraft above the runway may be obtained by a 

formula determined from figure 2.) During a takeoff run, the airplane is tracked by the transit. As 

the airplane passes up through the horizontal cross hairs of the transit sight, the transit is stopped. A 

ground observer may be waved into position on the runway below the cross hairs to note the 

distance; or a calibration of distance as a function of transit azimuth may be made, and the distance 

at 50 feet read directly. Using this method the height of the aircraft above the runway may be 

obtained by a formula determined from figure 2. 

Figure 2 – FORMULA TO DETERMINE HEIGHT OF THE AIRCRAFT ABOVE RUNWAY

(bb) A more accurate field method of obtaining takeoff data consists of a 

theodolite pivoted so it may track the aircraft during the takeoff run. See figure 3. 
12/30/03 AC 23-15A 

7 

Figure 3 – TAKEOFF DATA INSTALLATION FOR 

SWIVELING CAMERA OR RECORDING THEODOLITE

(cc) The theodolite is constructed in such a way that, by keeping cross hairs 

on the aircraft, a pencil trace of the aircraft position is placed on a chart fastened rigidly to the 

theodolite supports, or alternately, an electronic trace could be fed directly to a laptop computer. 

The swiveling theodolite is set up at a known distance from the runway and so aligned as to 

encompass only as much of the runway as will be necessary for the tests of the particular aircraft 

under consideration. This is done to obtain the greatest accuracy from the instrument. 

(dd) Various standard distances from the runway may be arbitrarily 

determined and charts prepared in advance for use on this theodolite. A timing mechanism built into 

the sighting bar marks every second on the chart. Ground observers are used to mark the exact point 

of takeoff, and this information may be placed on the chart at the end of each test. A typical chart 

and takeoff graph is illustrated in figure 4. 

Figure 4 – TYPICAL CHART AND TAKEOFF GRAPH 

2. A fixed grid may also be used to photographically record the tests. In this

method, a grid consisting of a network of calibrated wires is placed in front of a video camera in the 

manner shown in figure 3, and at such a distance that it will remain in focus along with the airplane 

being tested. A timing device may be mounted on either the grid or camera to give a time history of 

the takeoff or landing. A typical frame taken through this type of grid is shown in figure 5. 
AC 23-15A 12/30/03 

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Figure 5 – FIXED GRID 

3. From information obtained by any of the above methods in the previous 

section, the observed data may be plotted as in figure 6. This figure is usually included in the final 

report as is the corrected takeoff data. 

Figure 6 – CORRECTED TAKEOFF DATA 

4. All takeoff performance data are corrected to sea level standard conditions 

and zero wind unless otherwise specified. A minimum of six takeoffs should be made and 

measured. Each test may be made using the appropriate speed over the obstacle. 

(c) For simple airplanes equipped with reciprocating sea level engines, an acceptable 

data correction process to produce the takeoff distance for standard sea level no wind conditions is 

presented in figure 7.
12/30/03 AC 23-15A 

9 

Figure 7 – DETERMINATION OF STANDARD S.L. TAKEOFF DISTANCE SEGMENT 

METHOD (ACCELERATION SEGMENT)
AC 23-15A 12/30/03 

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1. The Takeoff Distance Segment Method (figure 7) is a simplified method to 

collect takeoff distance data to a 50-foot obstacle clearance height. This method is appropriate for 

simple airplanes because it is conservative and it does not require any elevation instrumentation to 

determine the 50-foot point. This method sums the ground acceleration, without any climb, to the 

point where the target obstacle clearance speed is achieved, with the horizontal distance to climb 50 

feet. 

2. A simple way to understand the takeoff distance segment method is to 

understand it in terms of work/energy. The total distance is the sum of the work/energy required to 

accelerate to the obstacle clearance speed without any climb and the work/energy required for a 

steady climb of 50 feet (out of ground effect). The data for the climb segment should be based on 

the data reduction used for climb testing. Airplanes with fixed pitch props should use the equivalent 

altitude method, whereas airplanes with constant speed propellers should use the density altitude 

method. Radio calls can allow ground observers to mark distances to planned liftoff and obstacle 

clearance speeds. This figure presumes the test to have been conducted within the +5/-1 percent 

weight tolerance of § 23.21, and that correction of off-standard weight is not necessary. For the 

same type of airplane, an acceptable method of determining the approximate effects of altitude and 

temperature upon takeoff distance is presented in figure 8. 
12/30/03 AC 23-15A 

11 

Figure 8 – DETERMINATION OF TAKEOFF DISTANCE TO 50 FEET AT GIVEN ALTITUDE 

AND TEMPERATURE 
AC 23-15A 12/30/03 

12

3. The correction process of figures 7 and 8 presume the acceleration distance to 

vary inversely as the excess thrust that exists at the 50-foot speed, rather than inversely with the 

“effective acceleration” which generally corresponds with a speed approximately 30 percent lower. 

This simplifying assumption enables use of the airplane's climb performance ratio as an approximate 

correction factor for the effect of altitude and temperature upon acceleration distance, and thereby 

avoids the need for thrust computations. However, the process is not considered to be valid for 

extrapolating performance to gross weights or wind conditions, which differ significantly from those 

of the test. 

4. This method calculates total takeoff distance and not a ground run distance. 

Part 23 does not require any ground distance data for small airplanes; however, it would be helpful 

to the pilot to include the ground distance numbers that are determined using this method. The 

ground distance for sea level, standard day conditions at gross weight could be provided with 

correction factors for increasing altitude and temperature. 

 (d) Glossary of Terms: 

 Hp - Pressure Altitude OAT - Outside Air Temperature 

 HD - Density Altitude σ - (sigma) Density Ratio 

 He - Equivalent Altitude α - Runway Slope, in Degrees 

 R/CGU - Rate of Climb, Gear Up b - Wingspan 

E - Oswald Efficiency Factor g - Gravitational Constant 

 (.6 may be assumed in the 

 absence of analysis or test) 

 c. Climb. 

 (1) Regulations Reference. Sections 23.65 and 23.1587. 

 (2) Discussion. Section 23.65 requires the determination of climb performance, which 

exceeds a minimum standard. When AC 23-8B was published, it no longer included the previously 

longstanding equivalent altitude method of reducing climb data for fixed pitch propeller airplanes. 

The elimination of the equivalent altitude method of reducing climb data leaves no practical method 

for simple airplanes with fixed pitch propellers to reduce climb data. 

• The density altitude method of climb data reduction for constant speed propeller 

airplanes is still embodied in AC 23-8B. 

• For small airplanes, simplified methods are acceptable as follows: 

 (a) Equivalent Altitude. 

1. Data reduction procedures using the equivalent altitude method are an 

acceptable means of compliance for small airplanes with fixed pitch propellers. This method is 

described in National Advisory Committee for Aeronautics (NACA) Report 297. The data reduction 

form shown in figure 9 may be employed. This method is applicable to both saw tooth and 

continuous climb data sets. Full throttle operation is required for valid results. 
12/30/03 AC 23-15A 

13 

Figure 9 – DATA REDUCTION FORM CLIMBS – EQUIVALENT ALTITUDE METHOD 
AC 23-15A 12/30/03 

14

2. The essential limitation to this method is that the correction to the observed 

climb for power, when the outside air temperature is not standard, is predicated upon the assumption 

that all engine controls are fixed. That is, no correction for variation in throttle setting, mixture, 

carburetor heat, etc., is made, and a climb at any part throttle setting is corrected for that throttle 

setting but not to full throttle. This method is referred to as the “equivalent altitude method” since it 

employs a correction to climb performance test data for atmospheric temperature variations from 

“standard” which indicates that the performance obtained under any atmospheric temperature and 

pressure may be obtained at some “equivalent altitude” in the standard atmosphere. The “equivalent 

altitude” may for the purposes of this AC be expressed as the “pressure” altitude plus 0.36 times the 

algebraic difference between the “density” altitude and the observed “pressure” altitude 

(“equivalent” altitude will always lie between the “pressure” altitude and the “density” altitude). As 

mentioned above, when climb performance is referred to “equivalent” altitude, no further correction 

for the effect of power changes needs to be made, and the final climb obtained thereby is that which 

would be obtained in the “standard atmosphere” at a height equal to the “equivalent” altitude when 

the power plant is operated as it was in the actual test. 

 (b) Density Altitude. Data reduction procedures using the density altitude method are 

an acceptable method of compliance for small airplanes with constant speed propellers. This 

method is outlined in AC 23-8B. The data reduction form shown in figure 10 may be employed. 

This method also is applicable to both saw tooth and continuous climb data sets. 
12/30/03 AC 23-15A 

15 

Figure 10 – DATA REDUCTION FORM CLIMBS – DENSITY ALTITUDE METHOD 

(SHEET 1 OF 2) 
AC 23-15A 12/30/03 

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Figure 10 – DATA REDUCTION FORM CLIMBS – DENSITY ALTITUDE METHOD 

(SHEET 2 OF 2) 
12/30/03 AC 23-15A 

17 

(c) Engine Power Correction. These methods make no direct engine power corrections 

for the difference between calibrated and rated power. The determination of the "equivalent" 

altitude empirically adjusts the data to allow for atmospheric effects on power for fixed pitch 

propeller installations. If further corrections for engine power (differences between calibrated and 

rated power) are desired, the following process may be utilized for either the equivalent or density 

altitude method: 

 1. The airplane climbs because a surplus of power is available in accordance

with the relationship,

R

C BHP p ex W = × η × 33000 

where, 

R

C = rate of climb, feet/minimum

η p = propulsive efficiency (.75 may be used for constant speed 

propellers and .65 for fixed pitch propellers if no better value 

 is known) 

BHPex = excess brake horsepower available 

W = aircraft weight, pounds 

 2. To develop a power correction, the above equation is solved for, 

 BHP ( ) ( ) R

C ex = ×W ÷ η p

× 33000

where, 

R

C = sea level rate of climb developed in flight test 

W = airplane approved gross weight 

 Also, 

BHPex = BHPavail − BHPreq

where, 

BHPavail = maximum power available at sea level at the manifold 

pressure and engine rpm, which can be achieved. 

BHPreq = power required for level flight at the climb speed. 

The power correction must be applied to the BHPavail

 term. For example, the calibrated engine 

produces 101 percent rated power, then the BHPavail

 must be reduced by 1 percent. 

Therefore, 

BHPex ( ) BHPavail CORR BHPreq corr = − −

where, 

BHPexcorr = excess power remaining following the power correction 

CORR = power correction to available power 
AC 23-15A 12/30/03 

18

Using the corrected excess power, resolve the original equation to obtain the corrected rate of 

climb, 

R

C BHP W corr p excorr = × η × 33000 ÷

 (d) Data Requirements. In order to provide AFM data showing the effect of altitude 

and temperature as required by § 23.1587, a sufficient number of climbs through a range of speeds 

must be completed allowing rate of climb to be plotted against equivalent or density altitude

(whichever is appropriate). This relationship is then used to produce the AFM performance 

information. It is also necessary to perform climbs at different speeds in order to determine the best 

rate of climb speed Vy. 

 d. Landing. 

 (1) Regulations Reference: Sections 23.75 and 23.1587. 

 (2) Discussion. 

 (a) Measurement Methods. Section 23.75 requires the measurement of the distance 

required to land over a 50-foot obstacle and come to a stop. The methods described for takeoff 

measurement are equally applicable for landing performance measurements. 

 (b) Data Reduction. A number of ways exist to correct the test data obtained above to 

standard conditions at sea level. One method that has been used is shown in figure 11. These forms 

are oriented for reduction of test data obtained by photographic methods but may be adapted to other 

data collection methods. 
12/30/03 AC 23-15A 

19 

Figure 11 – DATA REDUCTION FORM – CORRECTION OF LANDING DATA 

TO STANDARD CONDITIONS (SHEET 1 OF 2) 
AC 23-15A 12/30/03 

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Figure 11 – DATA REDUCTION FORMCORRECTION OF LANDING DATA TO STANDARD 

CONDITIONS (SHEET 2 OF 2) 

 e. Balked Landing. 

 (1) Regulation Reference. Section 23.77. 

 (2) Discussion. 

(a) The equivalent altitude method of climb performance data reduction may be used 

for airplanes with fixed pitch propellers. The discussion under § 23.65 applies. 

(b) For reduced testing requirements, the following process may be employed: 
12/30/03 AC 23-15A 

21 

 1. At a convenient altitude, in smooth air, conduct climbs through the same 

altitude band in opposite directions at the same speed. These climb segments should be of 

approximately three minutes duration (subject to engine cooling restraints). Climbs should be 

performed perpendicular to reported winds at test altitude. Altitude should be recorded at 30-second 

intervals. 

 2. Reduce these climb data by the equivalent altitude method and average the 

two rates of climb. 

 (c) Ensure the climb gradient equals or exceeds 1:30, as required in § 23.77. 

 f. Longitudinal Control. 

 (1) Regulations Reference. Sections 23.145, 23.161, and 23.677(b). 

 (2) Discussion. Sections 23.145(e)(1), 23.161, and 23.677(b) together have been interpreted 

to require an elevator trim tab system or an elevator trim system totally independent from the 

elevator control system. To ensure that a tab system is flutter free with the disconnection of a 

control element in the tab system (as required by § 23.629(f)), a fully redundant tab control system 

back to the trim control is effectively required. For small airplanes, the following simplified 

methods are permitted: 

 (a) A longitudinal control system that provides trim control through a bungee system 

connected to the elevator horns complies with this rule. 

 (b) A bungee trim system attached not to the elevator horn, but to a pushrod, or 

pushrods, connected to the elevator also comply with the rule. 

 g. Static Longitudinal Stability. 

 (1) Regulation Reference. Section 23.175. 

 (2) Discussion: 

(a) Stick force curve requirements are specified by § 23.175, but need not be measured 

with instruments if changes in speed are clearly reflected by changes in stick forces. 

(b) Because of the relatively small speed and center of gravity (CG) envelopes, a 

simplified matrix of the configurations to be tested is an acceptable method of compliance. 

Additional guidance is available in AC 23-8B. 

1. Compliance with the rule may be met by a qualitative assessment of stick force 

gradients by the test pilot for the following matrix of flight conditions. Tests should be conducted at 

the most critical weight and CG with gear extended. For light aircraft, the most critical condition is 

usually lightweight and aft CG. 

(aa) Section 23.175(a) Climb - flaps up, gear up, 75 percent power, trimmed to 

Vy; 
AC 23-15A 12/30/03 

22 

(bb) Section 23.175(b) Cruise - flaps up, gear up 75 percent power, trimmed 

for level flight; and 

(cc) Section 23.175(c) Approach/Landing - landing flaps, power idle, trimmed 

to the recommended landing approach speed. Repeat with power for a three-degree descent. 

2. For any of these four conditions where stability is marginal, as determined by 

the test pilot, the stick force gradient must be measured. 

3. For example, if stability in climb at aft CG were the only marginal stability 

flight condition, a measurement of stick force gradient with pertinent comments in this condition 

would comply with the rule. 

 h. Stall. 

 (1) Regulations Reference. Sections 23.201 and 23.203. 

 (2) Discussion. Compliance may be shown by qualitative test pilot assessments. On 

airplanes without gyros, a flat Plexiglas plate over the glare shield on which the test pilot can mark 

bank angles with a grease pencil may be used to substantiate bank angles. 

 (a) Test pilot notation of altitude loss may be from observations of a standard altimeter. 

 (b) A Plexiglas plate with incremental bank angles placed over the glare shield and a 

video camera may be used to record bank angles. 

 (c) Compliance may be shown by rational analysis with testing at forward CG for stall 

speed determination and aft CG for stall characteristics determination. 

 i. Stall Warning. 

 (1) Regulation Reference. Section 23.207. 

 (2) Discussion. Compliance with this rule for small airplanes is found where the stall 

warning begins at not less than five knots above stall speed. The upper limit for stall warning must 

not produce a nuisance. 

 j. Spin. 

 (1) Regulation Reference. Section 23.221. 

 (2) Discussion. AC 23-8B, with or without the following modification, is considered an 

acceptable method of compliance for small airplane spin testing. 

 (a) Modifications of AC 23-8B, Provisions. The following modifications of 

AC 23-8B, paragraphs are accepted for application to normal category spin substantiation: 
12/30/03 AC 23-15A 

23 

 1. b(1) Weight and CG Envelope. For normal category spins, the corners of the 

approved loading envelope should be tested. 

2. b(3) Control Deflections. For airplanes with rigging tolerances specified as 

+/-1 degree or less, control surface rigging may be set to nominal specifications. For airplanes with 

rigging tolerances specified as greater than +/-1 degree, tests should be conducted at nominal 

specifications; and if any spin configuration is found to be critical, then the effects of rigging should 

be investigated for that condition. 

 3. b(9) Trimmable Stabilizer. The effect of the trimmable stabilizer on spins 

should be determined for the critical conditions with the trim set for 1.5 Vs1 in the cruise 

configuration, 1.2 Vs1 in the takeoff configuration, and 1.3 Vs1 in the landing configuration. 

 4. c(3) Recovery From Spins Following Abnormal Control Usage During Entry 

and Recovery. The provisions of this paragraph should be applied as necessary based on the 

outcome of the testing conducted in paragraph 5c(4). 

 5. c(4) Spin Matrix. Add the following to this paragraph after the present first 

sentence: 

 The airplane configurations to be evaluated should correspond to 

the configurations expected to be used for takeoff, cruise, and 

landing. For a normal category airplane, the spin test matrix 

should cover those abnormal control inputs reasonably expected 

from a pilot experiencing an inadvertent spin entry such as 

forgetting to reduce power, reflexively applying anti-spin aileron 

(against the turn) in response to roll-off, or inadvertently 

reversing recovery rudder and elevator sequencing. The “Normal 

Category Spin Test Matrix” is an acceptable method of 

compliance, unless unusual response requires additional 

exploration (see figure 12). 
AC 23-15A 12/30/03 

24

Figure 12 – NORMAL CATEGORY SPIN TEST MATRIX

 6. c(5) Unrecoverable Spin. Any spin that cannot be recovered within the 

required spin criteria. 

(b) Additional Guidance: Spin Resistant Airplanes. The following guidance on the 

application of the new § 23.221(a)(2) spin resistant provision is provided: 
12/30/03 AC 23-15A 

25 

 1. In § 23.221(a)(2)(ii), "with the ailerons deflected opposite the direction of turn 

in the most adverse manner" means anti-spin or "reflexive" ailerons. 

 2. In § 23.221(a)(2)(ii), "respond immediately" means recovery in approximately 

one-quarter turn or that amount that the test pilot determines is immediate and repeatable. 

 3. The preceeding spin test guidance does not reduce the regulatory burden to 

show that it is “impossible to obtain” an unrecoverable spin for a given airplane design. The 

manufacturer is responsible for compliance with the regulations and should perform a thorough spin 

test evaluation. This AC simply describes a methodology that the FAA has found is adequate for a 

showing of compliance to the spin requirements for small, simple, low performance airplanes. 

Finding literal compliance to the regulation that states “... it must be impossible to obtain 

unrecoverable spins...” is not practical since this would necessitate an infinite number of test points. 

The methods described have been found to be an adequate number of test points to find compliance 

for these airplanes. This is derived from experience, technical data, and judgment, through many 

years using AC 23-8A for showing compliance on more complex airplanes. The methodology in 

this AC is a refinement of the method in AC 23-8A for showing compliance to the spin requirement 

of 23.221(a)(1)(iii) for these simple airplanes. 

 k. Emergency Landing Dynamic Conditions. 

 (1) Regulations Reference. Section 23.562. 

 (2) Discussion. 

 (a) See AC 23.562-1 “Dynamic Testing of Part 23 Airplane Seat Restraint Systems and 

Occupant Protection” for information. AC 23.562-1 addresses all part 23 airplanes, and has no 

specific guidance for “small, simple, low performance airplanes”. However, all of the guidance 

material may be applied to “small, simple, low performance airplanes”. 

 (b) See AC 23-11A “14 CFR Part 23 Type Certification of an Airplane Originally 

Certificated to Joint Aviation Regulations - Very Light Airplane (JAR-VLA) Standards”. Some 

small, simple, low performance airplanes, are similar to the JAR-VLA discussed in AC 23-11A, and 

therefore, that AC's guidance material may be of interest to the reader. 

l. Fabrication Methods. 

 (1) Regulation Reference. Section 23.605. 

 (2) Process Specifications Format. The following sample process specification (for 

welding) provides an acceptable format. An applicant may develop specifications in this format. 
AC 23-15A 12/30/03 

26 

 (a) 1.0 PURPOSE

This section should cover what the specification will control. Such as, 

This specification establishes the engineering requirements 

for name process to be used by company name . 

Personnel and machines used shall be able to meet or 

exceed this specification. 

 (b) 2.0 REFERENCES

The following publications are to be used to clarify this specification 

or be the basis for testing or equipment/personnel certification: 

List other company specifications, military specifications (MIL SPEC) 

 or standards." 

 (c) 3.0 STANDARDS

3.1 Weld word vocabulary reference AWS A3.0-8 for definitions used in weld 

related work. 

3.2 Examples of acceptable and unacceptable weld should be shown in this section. 

3.3 Method of certification and recertification of the welder. Weld specimens and 

qualification and requalification test conditions. 

3.4 Visual and radiographic inspection, metallographic examination and standards 

should be included in this section as applicable. 

 (d) 4.0 QUALIFICATION, CERTIFICATION, REQUALIFICATION, AND

 RECERTIFICATION

The ability to weld or inspect to the requirement of this specification shows the 

person, process, and equipment are qualified. "Certified," means the welder, 

welding procedure, and welding machine is qualified to make welds, and can 

make welds, to this specification. 

4.1 Qualification requirement. 

4.2 Equipment, machines, and process procedures should consist of such things as 

required tooling, welding, schedule, pre-heat cycles, post-heat cycles, and 

required calibration of equipment. 

 (e) 5.0 MATERIALS

5.1 List welding rod and electrodes. 
12/30/03 AC 23-15A 

27 

5.2 Gases. 

5.3 Storage of rods and electrodes. 

(f) 6.0 TECHNICAL

6.1 Inspection and manufacturing requirements. 

6.2 Pre-heat and post-heat requirements if needed. 

6.3 Heat treatment. This paragraph should cover any heat treatment required to 

restore all material in a weldment to a certain temper or tensile strength. 

6.4 Detail gap - joint design information. 

6.5 Describe weld repairs if applicable. 

6.6 Cleaning, pre- and post-welding. 

(g) 7.0 MANUFACTURING AND QUALITY CONTROL

7.1 Manufacturing requirements. 

7.2 Quality control requirements. 

 m. Flutter. 

(1) Regulation Reference. Section 23.629. 

(2) Discussion. For general guidance on this section see AC 23.629-1A. 

(3) Regulation Reference. Section 23.629 (b). 

(4) Discussion. All airplanes certified to Title 14 CFR part 23, in any category, must 

perform flight flutter test(s) to show compliance in addition to any analytical methods. 

(5) Regulation Reference. Section 23.629(d). 

(6) Discussion. Airplanes that are the subject of this AC would typically meet the 

requirements of § 23.629(d)(1) through (d)(3). However, the applicant should review 

the criteria to ensure applicability. Based on the review of criteria, Engineering Report 

No. 45 (Simplified Flutter Prevention Criteria) could then be used to substantiate this 

portion of the regulations. 

(7) Regulation Reference. Section 23.629(f)(2). 
AC 23-15A 12/30/03 

28 

(8) Discussion. For small low performance airplanes, designing the actuating structures to a 

factor of safety equaling four and providing redundant fastener safety as a means to 

minimize loss of single fastener joint integrity would be an acceptable method of 

showing compliance with this request. 

n. Proof of Strength (Wings). 

(1) Regulation Reference. Section 23.641. 

(2) Discussion. Section 23.641 requires proof of strength of a stressed skin wing through 

tests or by combined structural analysis and load tests. 

(a) Proof of strength of conventional aluminum or wood stressed skin wing structures 

primarily by analysis to limit and test to ultimate loads for the most critical bending and torsional 

wing load conditions is acceptable. 

(b) In order to determine the most critical bending and torsional wing loads, one must 

complete a loads survey of the structure to determine which load case(s) produce the lowest safety 

margin against catastrophic failure of the wing. The actual mechanics of how to determine those 

specific load conditions requires qualified and experienced engineering personnel. The critical load 

conditions must be determined for the specific structural and airplane configuration, by detailed load 

and stress analysis. A specific explanation of this procedure that would be applicable for every 

airplane design doesn't exist. 

(c) For conventional aluminum materials, the ultimate strength is typically less than 

one and a half times the yield strength. This means that as long as the article doesn't fail at the 

ultimate load, it will not yield at limit load. This rationale is for the worst-case scenario where the 

part fails in tension. For most structures however, failures occur due to instability first. The 

allowable ultimate load capability of a member in compression is lower than the tension capability. 

This further reduces the difference between the ultimate and yield strength. Structural analysis 

should still be used to demonstrate that the yield strength is not exceeded at limit loads. If nonconventional aluminum is used, where this yield-to-ultimate strength relationship doesn't exist, then 

testing to ensure no yielding occurs at limit loads may be in order, at the ACO's discretion. 

(d) In any event, part 23.307 is still applicable. Section 23.307 states in part that 

“Structural analysis may be used only if the structure conforms to those for which experience has 

shown this method to be reliable.” If in the ACO's judgment, the structure or analysis techniques 

used by the applicant, will not produce reliable analytical data, then testing may be in order. 

(e) For wooden structures, there are no well-defined (published) yield strength 

values. When you observe the stress-strain curves for wood, it is evident that the relationship is not 

linear up to failure. The mechanism, that appears as yielding on the stress-strain curve, is actually 

micro cracks that develop within the matrix (lignin) between the fibers (cellulose). This behavior is 

very similar to that exhibited by newer composite materials (graphite/epoxy). These micro cracks 

have a negligible effect on the final ultimate strength, stiffness, or fatigue properties of the material. 

Experience has shown that the ultimate strength test along with analysis is adequate to show 

compliance. 
12/30/03 AC 23-15A 

29 

 o. Landing Gear. 

 (1) Regulations Reference. Sections 23.723, 23.725, 23.726, and 23.727. 

 (2) Discussion. 

(a) The designer selects the landing load factor, and the applicant is required to 

demonstrate that the airplane will not exceed this factor when the aircraft is landing at the descent 

velocity specified by the regulations (reference § 23.473). For design purposes, this load factor may 

not be less than 2.67 and must not be exceeded by the certification drop tests specified in §§ 23.723 

through 23.727. 

(b) Alternatively, a conservative approach may be chosen by using a load factor of 

4.2 g's to directly determine the static loads to be applied through design or static test to the landing 

gear. This load factor is considered conservative enough that it is unnecessary to verify it is not 

exceeded by an instrumented drop test. If this method (load factor of 4.2g's) is used, the only 

dynamic test required is the most critical drop test for reserve energy either in a fixture or by 

dropping the airframe, as described in § 23.727, without the need for instrumentation. 

 p. Brakes. 

 (1) Regulation Reference. Section 23.735. 

 (2) Discussion. 

 (a) A conservative rational analysis (§ 23.735(a)(1)), or Technical Standard Order 

(TSO) type tests (§ 23.735(a)(2)) and takeoff power test (§ 23.735(b)) are adequate for this class of 

airplane. (A rational analysis may include data such as service history, similarity to other approved 

brakes, etc., sufficient to increase the FAA's confidence level prior to installation/flight testing.) 

 (b) Additionally, taxi and landing stop tests to demonstrate acceptable longitudinal and 

directional stability and control, and that no unacceptable vibrations, squeal, fade, grabbing, or 

chatter are present, are required in accordance with §§ 23.75, 23.143(a)(6), 23.231(a), 23.233(c), 

23.493(c), 23.1301(d), and 23.1309(a)(1). 

NOTE 

"Acceptable" means controllable by a pilot of any skill level. 

 q. Compartment Interiors/Powerplant Instruments. 

 (1) Regulations Reference. Sections 23.853 and 23.1337. 

 (2) Discussion. 

(a) Section 23.853(e) does not prohibit direct reading oil pressure gauges, but it must 

be ". . . adequately shielded, isolated, or otherwise protected so that any breakage or failure of such 

an item would not create a hazard." Additionally, § 23.1337(a)(2)(i) and (ii) state that, "Each 

line . . . must have restricted orifices or other safety devices at the source of pressure to prevent the 
AC 23-15A 12/30/03 

30 

escape of excessive fluid if the line fails; and be . . . located so that the escape of (such) fluid would 

not create a hazard." 

(b) A direct oil pressure gauge line located in the cabin and fitted with an orifice of 

approximately 0.060-inch diameter located at the engine fitting limiting the flow of the oil into the 

cabin in the event of an oil line rupture inside the cabin is acceptable without a shrouded oil line 

vented overboard. 

 r. Fire Protection of Flight Controls, Engine Mounts, and Other Flight Structure. 

 (1) Regulation Reference. Section 23.865. 

 (2) Discussion. Two methods are available to validate that flight controls, engine mounts, 

and other flight structure can satisfy this requirement: 

 (a) Verify that the proposed components use a known fireproof material (example, 

steel or stainless steel). Or, as an alternative, a conformity inspection comparing the proposed 

assembly to an existing Parts Manufacturer Approval (PMA) or product that is used in an existing 

type certificated aircraft can be accomplished. 

 (b) The applicant can validate components not previously approved by performing a 

fireproof test. Procedures for conducting such tests are contained in AC 20-135. A proposed test 

plan would need to be reviewed and approved by the FAA prior to testing unless an existing TSO 

validation procedure is already published. The test would use a conformed control; a 2,000-degree 

Fahrenheit flame would be impinged onto the component and held in place for 15 minutes for 

fireproof compliance. Before removal of the flame at the termination of the test, loads should be 

applied to the component to show that it can still perform its intended function. 

NOTE 

This portion of the regulations does not address engine 

controls. See part 23, § 23.1141(f) for requirements 

regarding the fire resistance testing for engine controls. 

Also, the reader may refer to AC 23-17A, “Systems and 

Equipment Guide for Certification of Part 23 Airplanes” 

for more information. 

 s. Lightning Protection of Structure, Fuel System Lightning Protection, and Systems. 

 (1) Regulations Reference. Sections 23.867, 23.954, and 23.1309(e). 

 (2) Discussion. 

(a) Lightning testing is not required for those airplanes intended for operation under 

Visual Flight Rules (VFR) only. A general engineering overview of the airplane construction 

features to determine that any lightning induced hazards are minimized may be all that is required, if 

it can be determined that sufficient conductivity is available throughout the airplane and that the 

design employs features that have been found to minimize the hazard to the airplane and occupants. 

Refer to FAA report number DOT/FAA/CT-89/22, “Aircraft Lightning 
12/30/03 AC 23-15A 

31 

Protection Handbook” for best practices. The Type Certificate Data Sheet (TCDS) will contain this 

statement: "This aircraft is not approved for Instrument Flight Rules (IFR) operation under the 

provisions of § 91.205(d)." 

(b) For those airplanes intended for operation under IFR a more detailed assessment 

will need to be made as to the vulnerability to lightning related hazards. Sections 23.867, 23.954, 

and 23.1309(e) of part 23 of the 14 CFR will need to be individually addressed. The depth of the 

verification should be commensurate with the degree of hazard. Since airplanes that employ 

conventional service proven construction and systems (i.e., all-aluminum airplanes with gyro flight 

instruments, magneto type engine ignition systems, mechanical fuel systems, etc.) have 

demonstrated over many millions of flight hours excellent inherent lightning protection qualities, 

similar designs may only need a qualitative engineering assessment that all hazards have been 

reasonably minimized. The Aircraft Lightning Protection Handbook, DOT/FAA/CT-89/22 may be 

used as a guide to make this assessment. 

(c) Airplane designs that employ all composite construction, electronic flight 

instrument displays, electronic ignition systems, electronic fuel systems or electronic engine controls 

are generally more susceptible to lightning threats and, require further investigation. Therefore, 

airplanes that employ these designs are not within the scope of this AC. For electronic systems, see 

AC 20-53A, AC 20-136, and RTCA DO-160D for additional information. AC 23.1309-1C provides 

an acceptable means of identifying and assessing complex critical and essential systems. 

(d) Airplanes using the foregoing means of compliance shall display the following 

limitation placard: Not approved or eligible in Instrument Meteorological Conditions (IMC). 

(e) See AC 23-17A “Systems and Equipment Guide for Certification of Part 23 

Airplanes” for more information. 

 t. Fuel Tank Tests. 

 (1) Regulation Reference. Section 23.965. 

 (2) Discussion. Certain requirements as defined in § 23.965(b) and (c) would be unduly 

burdensome in cases where certain small aluminum or nonmetallic fuel tanks incorporate side 

stiffeners or beads and internally attached baffles. The FAA tests described in § 23.965(a) satisfy 

the requirements if the tank has less than a 10-gallon capacity, or the tank interior has baffles (or 

equivalent support) at least every 15 inches in both directions. 

 u. Avionics Installation. 

 (1) Regulations Reference. Sections 23.1301, 23.1431, 23.1309(a), and 23.1311. 

 (2) Discussion. 

(a) Section 23.1301 requires that all installed equipment perform its intended 

functions. For communication and navigation equipment required for IFR operations, an acceptable 

means of performance evaluation of these systems is provided in AC 23-8B, chapter 5. 
AC 23-15A 12/30/03 

32 

(b) For non-required navigation and communication equipment that could be used for 

flight purposes and which have not been previously approved, an acceptable means of performance 

evaluation of these systems is provided in AC 23-8B, chapter 5, and AC 23.1309-1C. For optional 

equipment that has no functions that can be utilized by the flight crew for the purpose of flight (i.e., 

stereo receivers, television sets, tape players, etc.), the intended function is considered to be the lack 

of any hazardous failure modes and the non-interference with other required equipment installed in 

the airplane. Evaluation of these systems should address only those failure modes or performance 

qualities that would directly result in hazard (fire, smoke, explosion, etc.) or indirectly affect safety 

by interfering with the operation of required equipment. Typically, FAA flight test pilot observation 

is adequate to determine any affects of interference. Non-flight related functions do not need to be 

evaluated. An acceptable method of evaluating adverse effects and minimizing hazards in 

accordance with § 23.1309(a) is provided in AC 23.1309-1C. 

(c) The requirements of § 23.1431 are self-explanatory and parallel the requirements 

of § 23.1309(a). 

(d) The requirements of § 23.1311 pertain to the certification of electronic display 

instrument system installations. An acceptable means of compliance with the specific requirements 

of § 23.1311 are provided by AC 23.1311-1A. 

(e) For communication and navigation equipment with previous installation 

approvals, an acceptable means of performance evaluation of these systems is outlined below (the 

intent is to verify the installation, not the ability of the already proven system): 

1. Very High Frequency (VHF) Communication Transceivers. For VFR, 

establish satisfactory communications with the tower while on the airport ramp and in flight at 

20+/-5 Nautical Mile (NM) and the higher of 2,000 feet Above Ground Level (AGL) or Minimum 

Obstruction Clearance Altitude (MOCA). The flight path relative to the tower includes toward, 

away, 90 degrees right and 90 degrees left while in level flight at cruise power. 

2. VHF Navigation Receivers. For VFR, tune to a Visual Omni Test (VOT), or 

use a Visual Omni Range (VOR) checkpoint (+/-4 degrees tolerance), and fly to a VOR airborne 

checkpoint and check for accuracy within IFR tolerances (+/-6 degrees). The audio signal must be 

clearly audible. 

3. VHF Area Navigation (RNAV) Systems. VFR only: establish waypoint over 

known position and confirm accuracy, per the manufacturer's instructions. IFR approvals may be 

done in accordance with AC 20-121A, AC 20-130A, or applicable Global Positioning System (GPS) 

certification guidance. 

4. Automatic Direction Finder (ADF) Navigation Systems. For VFR, tune to 

known station; check bearing indication against known position, on the ground and at 2,000 feet 

AGL, or MOCA, (whichever is higher) at 20+/-5 NM, for two positions. Errors must not exceed +/-

5 degrees, and the aural signal must be clearly audible. 

5. Transponders, Mode A. For VFR, ask approach control or center to confirm 

operation, in the traffic pattern and at 2,000 feet AGL or MOCA (whichever is higher), at 20 NM. 
12/30/03 AC 23-15A 

33 

6. Transponders, Mode C. For VFR, same as (v), also requesting altitude check, 

starting at 2,000 feet AGL, or MOCA (whichever is greater), and continuing every 2,500 feet up to 

90 percent of service ceiling; starting the climb at 10 NM and ending at 80 NM from the station. 

7. Long Range Navigation Communication (LORAN-C) Systems. Use VFR 

only criteria of AC 20-121A. 

8. Electro Magnetic Compatibility. With all systems exercised in flight, verify 

by observation that no adverse effects are present in the installed equipment. 

 v. Equipment Systems and Installation. 

 (1) Regulation Reference. Section 23.1309. 

 (2) Discussion. For those airplanes with equipment installations where a single failure 

would not cause loss of safe flight capability, or if not limited to VFR operation, a failure would not 

result in a significant reduction in the ability of the crew to cope with adverse operating conditions, 

§ 23.1309(a) is applicable. An example would be loss of the primary attitude indicator during an 

IFR flight where the pilot can maintain control of the airplane by other means such as use of a 

secondary attitude indicator or use of partial-panel piloting techniques. In this instance, further 

evaluation would not be needed other than the requirements of § 23.1309(a), which addresses 

adverse effects on other equipment, the minimizing of hazards on single engine airplanes, and the 

prevention of hazards on multiengine airplanes. The methods of compliance outlined in AC 

23.1309-1C, figure 1 and paragraph 7, are acceptable for evaluating these systems. 

(a) For those airplanes with equipment installations whose failure conditions are 

catastrophic, the requirements of § 23.1309(b) are also applicable. The methods of compliance 

outlined in AC 23.1309-1C, paragraphs 9 and 10 are acceptable for evaluation of these systems. 

(b) The general considerations of § 23.1309(c) and (f) are self-explanatory and are 

applicable to all airplanes being evaluated. Paragraph (d) is applicable only to commuter category 

airplanes (this intent was inadvertently omitted with the adoption of amendment 23-41). Paragraph 

(e) is applicable to all installations with critical or essential functions that are also susceptible to 

lightning threats and radio frequency energy threats (other than High Intensity Radiated Fields 

(HIRF). This is discussed in paragraph "5s" of this AC and in AC 23.1309-1C, paragraph 11. 

(c) Those systems employing software in their design will need further evaluation. 

AC 23.1309-1C, paragraph 12 discusses this. AC 20-115B, and RTCA/DO-178B, is an acceptable 

means of assessing these systems. 

 w. Airplane Flight Manual. 

 (1) Regulations Reference. Sections 23.1581, 23.1585, and 23.1587. 

 (2) Discussion. For small airplanes, compliance is met by computing performance at two 

temperatures--standard day, and standard day +30 degrees Centigrade, and at least three altitudes for 

takeoff and landing distance and climb data expanded to a minimum of 10,000 feet altitude. A 
AC 23-15A 12/30/03 

34 

presentation (the use of tables/charts rather than graphs) similar to that found in figure 13 is 

acceptable. 

Figure 13 – PERFORMANCE CONTENT AND FORMAT