vii
11.11 Battery Box11-6
11.12 Securing the Battery11-6
11.13 Sump Jar11-6
11.14 Venting11-7
11.15 Drains11-8
11.16 Electrical Installation11-8
11.17 Quick Disconnect11-10
11.18 Weight and Balance (W&B)11-10
Section 3. Nickel-Cadmium Battery Installations11-11
11.19 General11-11
11.20 Electrical Analysis11-11
11.21 Maintenance Considerations11-11
11.22 Structural Requirements11-11
11.23 Isolation of Battery Case11-12
11.24 Ventilation11-12
11.25 Preinstallation Requirements11-12
11.26 Nickel-Cadmium Battery Installation11-13
11.27 Securing the Battery11-13
11.28 Quick Disconnect11-13
11.29 Voltage and Current Regulation11-14
11.30 Weight and Balance (W&B)11-14
Section 4. Battery Installation Checklist11-15
11.31 Structural Requirements11-15
11.32 Hazards to the Aircraft and its Occupants11-16
11.33 Operating Aspects11-16
11.34 Detail Design Standards11-16
11.35 Recordkeeping11-17
Section 5. Instructions for Continued Airworthiness11-18
11.36 Lead-Acid Batteries11-18
11.37 Nickel-Cadmium Batteries11-19
viii
Chapter 12. Adding or Relocating Instruments12-1
12.1 Purpose12-1
12.2 Hazards and Warnings12-1
12.3 Additional References12-1
12.4 Preparation12-1
12.5 Installation12-3
12.6 Testing, Marking, and Placarding12-9
12.7 Electronic Display Instrument Systems or Electronic Display Indicators12-11
12.8 Environmental Conditions12-12
Chapter 13. Cargo Tiedown Device Installations13-1
13.1 Purpose13-1
13.2 Hazards and Warnings13-1
13.3 Installation Considerations13-1
13.4 Fabrication and Installation13-1
13.5 Operating Limitations, Loading Instructions, and Placards13-9
13.6 Airworthiness Compliance Check Sheet: Cargo Tiedown Device Installations13-9
Chapter 14. Larger Tire Installations14-1
14.1 Purpose14-1
14.2 Hazards and Warnings14-1
14.3 Additional Reference (current editions)14-1
14.4 Installation Considerations14-2
14.5 Flight and Ground Handling Operational Checks14-4
14.6 Testing the Modification14-6
14.7 Maintenance (Including Inspection)14-7
14.8 Interchanging of Skis and Wheels14-9
14.9 Documentation14-9
14.10 Summary of Considerations for Approval of Larger Tire Installation (may be
used as a job aid)14-9
ix List of Figures
Figure 2-1. Bending of a Beam2-2
Figure 2-2. Typical Load2-3
Figure 2-3. Hypothetical of Determining Static Test Loads2-8
Figure 3-1. Force Diagram Normal-Utility Category3-3
Figure 3-2. Typical Fabricated Panel Mounting3-3
Figure 3-3. Typical Layouts3-4
Figure 3-4. Typical Shock-Mounted Base (Wood or Composition Flooring)3-6
Figure 3-5. Typical Shock-Mounted Base (Metal Flooring)3-6
Figure 3-6. Typical Rigid Base Plate Mount3-7
Figure 3-7. Typical Underseat Installation3-8
Figure 3-8. Typical Remote Unit Mounting Base-Vertical or Horizontal Other Than
Structure to Floor3-9
Figure 3-9. Typical Shelf Installation3-10
Figure 3-10. Typical Attachment of Support Structure to Tubular Frame Other Than
Structure to Floor3-11
Figure 4-1. Antenna Mount With Saddle4-2
Figure 4-2. Antenna Ground Plane for Nonconductive Mount4-7
Figure 4-3. One Means to Provide Adequate Antenna Bonding Through a
Composite Airframe4-7
Figure 4-4. Use Bushings for All Screws4-8
Figure 4-5. Typical Dipole Antenna Assembly4-9
Figure 4-6. Typical VOR Balun4-10
Figure 4-7. ADF Loop4-11
Figure 4-8. ADF Combined Sense Loop4-11
Figure 4-9. Communications (COM) Whip4-11
Figure 4-10. COM Whip Bent4-12
Figure 4-11. Emergency Locator Transmitter4-12
Figure 4-12. Global Positioning System4-12
Figure 4-13. Glideslope4-13
Figure 4-14. Marker4-13
Figure 4-15. Combined COM/VOR4-13
Figure 4-16. VOR Rabbit Ear4-14
x
Figure 4-17. VOR Blades4-14
Figure 4-18. Transponder/DME Probe4-15
Figure 4-19. DME/Transponder Blade4-15
Figure 5-1. Typical Anticollision or Supplementary Light Installation in a Skin
Panel (Unpressurized)5-3
Figure 5-2. Typical Anticollision or Supplementary Light Installation Involving a Cut
Stringer (Unpressurized)5-4
Figure 5-3. Typical Anticollision or Supplementary Light Installation in a Fin Tip5-5
Figure 6-1. Typical Hub Installation6-3
Figure 6-2. Typical Ski Installation6-4
Figure 6-3. Typical Fuselage Fittings6-6
Figure 6-4. Main Ski at Maximum Positive Incidence (Check Cable Taut)6-7
Figure 6-5. Main Ski at Maximum Negative Incidence (Safety Cable Taut)6-8
Figure 6-6. Main Ski Incidence Angles6-8
Figure 6-7. Typical Nose Ski Installation6-10
Figure 6-8. Typical Tail Ski Installation6-11
Figure 7-1. Typical Floor Mounting7-9
Figure 7-2. Typical Baggage Compartment Mounting7-10
Figure 7-3. Typical Oxygen Installation in Light Twin Aircraft7-11
Figure 8-1. Location of Cargo Release in Relation to the Rotorcraft’s Center of Gravity8-2
Figure 8-2. Typical Cargo Sling Wiring Diagram8-5
Figure 8-3. Typical Cargo Sling Installation No. 18-6
Figure 8-4. Typical Cargo Sling Installation No. 1 (Showing Fuselage Attachment Fitting)8-7
Figure 8-5. Typical Cargo Sling Installation No. 1 (Showing Fore Aft Limiting Stops)8-8
Figure 8-6. Typical Cargo Sling Installation No. 2 (Cargo Hook Attached Directly to
Underside of Fuselage)8-8
Figure 8-7. Typical Cargo Sling Installation No. 3 (4-Leg, Cable Suspended)8-9
Figure 8-8. Typical Cargo Sling Installation No. 3 (Showing Cable Sling Leg Attachment
to Landing Gear Crosstube Fitting)8-9
Figure 8-9. Typical Cargo Sling Installation No. 3 (Showing Cargo Sling in
Stowed Position)8-10
Figure 8-10. Typical Cargo Rack Installation No. 18-11
Figure 8-11. Typical Cargo Rack Installation No. 1 (Showing Attachment Detail)8-12
Figure 8-12. Typical Cargo Rack Installation No. 28-12
xi
Figure 8-13. Typical Cargo Rack Installation No. 2 (Showing Rack Partially Installed)8-13
Figure 8-14. Typical Cargo Rack Installation No. 38-13
Figure 9-1. Glider Tow Angle9-2
Figure 9-2. Banner Tow Angle9-2
Figure 9-3. Typical Tow-Hitch Release Handle9-7
Figure 9-4. Tricycle Gear Aircraft9-8
Figure 9-5. Conventional Gear Aircraft—Leaf Spring Type Tailwheel9-8
Figure 9-6. Conventional Gear Aircraft—Shock Strut Type Tailwheel9-9
Figure 9-7. Conventional Gear Aircraft—Tubular Spring Type Tailwheel9-9
Figure 9-8. Typical TOST Hitch9-10
Figure 9-9. TOST Double Tow Rings9-10
Figure 9-10. Schweizer Type Hitch9-11
Figure 9-11. Typical Multiple Hitch for Banner Tow9-12
Figure 9-12. Typical TOST Mount for Tricycle Gear Aircraft9-12
Figure 9-13. Typical TOST Conventional Leaf Spring Mount9-13
Figure 10-1. Major Versus Minor Alterations10-3
Figure 10-2. The Three-Point Single Harness Positioning10-10
Figure 10-3. Side Mounted Single Diagonal Type Harness10-11
Figure 10-4. Acceptable Harness Mounting Areas10-11
Figure 10-5. Undesirable Horizontal Harness Positioning10-12
Figure 10-6. Undesirable Vertical Harness Positioning10-12
Figure 10-7. Ceiling Mounted Inertia Reel―Double Over-the-Shoulder Type Harness10-13
Figure 10-8. The Four-Point Independent Harnesses Positioning10-13
Figure 10-9. The Five-Point Harness Positioning10-14
Figure 10-10. “Y” Type Retractor Positioning10-14
Figure 10-11. Floor Mounted Inertia Reel―Double Over-the-Shoulder Type Harness10-16
Figure 10-12. Typical Floor Mounted Inertia Reel Installation10-16
Figure 10-13. Typical Seat Mounted Inertia Reel Installation10-17
Figure 10-14. Typical Wing Carry-Through Installation10-18
Figure 10-15. Typical Hat Section Reinforcement Installation10-18
Figure 10-16. Typical Bulkhead Reinforcement Installation10-19
Figure 10-17. Typical Stringer Section Reinforcement Installation10-19
Figure 10-18. Typical Localized Stringer Section Reinforcement Installation10-20
xii
Figure 10-19. Typical Attachments to Tubular Members10-20
Figure 10-20. Vertical Angle10-25
Figure 10-21. Horizontal Angle10-25
Figure 11-1. Typical Battery Installation in the Aircraft11-5
Figure 11-2. Typical Battery Installation With Sump Jar11-7
Figure 11-3. Battery Ventilation System11-8
Figure 11-4. Typical Battery Cutoff and Generator Alternator Control Circuit11-10
Figure 12-1. The Basic “T” Visual Meteorological Conditions (VMC)
Instrument Configuration12-2
Figure 12-2. Pressure Drop Data for Smooth Tubing12-7
Figure 13-1. Extruded Track, Anchor Plates, and Associated Fittings13-3
Figure 13-2. Miscellaneous Litter, Berth, and Cargo Tiedown Fittings13-4
Figure 13-3. Typical Attachment of Fittings to Honeycomb Structures13-5
Figure 13-3. Typical Attachment of Fittings to Honeycomb Structures – Continued13-6
Figure 13-4. Installation of Underfloor Support for Extruded Track13-6
Figure 13-5. Typical Cargo Tiedown Straps and Cargo Nets13-7
Figure 13-6. Example of Allowable Cargo Loading Diagram13-12
Figure 14-1. Diagram of Axle Height Measurement14-3
Figure 14-2. Typical Main Landing Gear Spring Strut and Axle Assembly14-8
List of Tables
Table 2-1. Ultimate Load Factors2-3
Table 2-2. Sample Load Factors2-4
Table 3-1. Typical Compass Calibration Card3-5
Table 3-2. Relationship Probabilities and Severity of Failure Conditions3-14
Table 3-3. Commonly Used Radio Frequencies on Aircraft3-15
Table 3-4. Aircraft Electrical and Electronic Systems3-16
Table 4-1. Wavelength in Feet = 984/Frequency in Megahertz (MHz)4-6
Table 6-1. Recommended Minimum Cable and Shock Cord Sizes6-5
Table 6-2. Approximate Main Ski Tension Forces6-9
Table 7-1. Typical Oxygen Duration Table7-8
Table 8-1. Cable Load Table8-3
Table 9-1. Representative Steel Cable Qualities9-7
Table 10-1. Static Test Requirements10-24
xiii
Table 10-2. Calculated 1/Cosine Values10-24
Table 12-1. CFM/Vacuum Values12-5
Table 12-2. Instrument Air Consumption for Example Vacuum-Driven Autopilot and
Instrument Installations12-5
Table 12-3. Equivalent Straight Tube Line Drops for Each 90-Degree Elbow Installed
in Any Given System (By O.D.)12-6
Table 12-4. Differential Pressure Across the Instrument Inlet and Outlet of the Example
Instrument Packages12-6
1-1 CHAPTER 1. GENERAL
1.1 Purpose of This Advisory Circular (AC). This AC contains methods, techniques, and practices acceptable to the Administrator for the inspection and alteration on nonpressurized areas of civil aircraft of 12,500 pounds gross weight or less. This data generally pertains to minor alterations. However, the alteration data herein may be used as approved data for major alterations when the AC chapter, page, and paragraph are listed in block 8 of Federal Aviation Administration (FAA) Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance), when the user has determined that it is appropriate to the product being altered, directly applicable to the alteration being made, and not contrary to the manufacturer’s data. This AC contains information pertinent to Title 14 of the Code of Federal Regulations (14 CFR) § 43.13.
Note: This is a guidance document. Its content is not legally binding in its own right and will not be relied upon by the Department as a separate basis for affirmative enforcement action or other administrative penalty.
Conformity with the guidance document is voluntary only. Nonconformity will not affect rights and obligations under existing statutes and regulations.
Note: The methods, techniques, and practices in this AC are an acceptable means of compliance with the regulation, but they are not the only means of compliance.
If persons performing maintenance, alteration, or preventive maintenance undertake another means of compliance, it must be acceptable to the FAA.
References to an established standard or publication support the acceptability of alternative methods, techniques, and practices.
1.2 Audience. This AC is for use by mechanics, repair stations, and other certificated entities.
1.3 Where You Can Find This AC. You can find this AC on the FAA’s website at https://www.faa.gov/regulations_policies/advisory_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov.
1.4 What This AC Cancels. AC 43.13-2B, Acceptable Methods, Techniques, and Practices – Aircraft Alterations, dated March 3, 2008, is canceled.
1.5 Reference. Title 14 CFR § 43.13(a) states that each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance must use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual, the instructions for continued airworthiness (ICA) prepared by its manufacturer, or other methods, techniques, or practices acceptable to the Administrator except as noted in 14 CFR § 43.16. FAA inspectors are prepared to answer questions that may arise in this regard. Persons engaged in the inspection and alteration of civil aircraft should be familiar with 14 CFR part 43 and 14 CFR part 65 subparts A, D, and E and applicable airworthiness requirements under which the aircraft was type certificated.
Note: Part 23 Amendment 23-63 and prior 14 CFR part 23 (prescriptive) regulations referenced in this AC contain sufficiently detailed language to allow
1-2 comp liance directly with each section (regulation) when applied to traditional designs that were prevalent at the time the regulations were written. These legacy prescriptive regulations are not sufficient nor appropriate for some modern designs. To show compliance with the new “performance-based rules” (Amendment 23-64, Implementation Procedures Guide, and subsequent), the applicant must choose an accepted means of compliance, per 14 CFR § 23.2010.
For more information, refer to Amendment 23-64 and AC 23.2010, F AA Accepted Means of Compliance Process for 14 CFR Part 23.
1.6 AC Feedback Form. For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.
2-1 CHAPTER 2. STRUCTURAL DATA
2.1 General. Structural integrity is a major factor in aircraft design and construction.
Addition or removal of equipment involving changes in weight could affect the structural integrity, weight, balance, flight characteristics, reliability, or performance of an aircraft.
This chapter is generic in nature and meant to assist the aviation maintenance technician in determining structural integrity. It is not meant to circumvent utilizing an FAA engineer or the responsible Aircraft Certification Service office when necessary.
2.2 Structural Design Process. Structural design processes follow these steps:
• Determine the overall load factors.
• Estimate the resulting loads.
• Distribute these loads over the aircraft.
• Determine the material, size, and shape of the part.
• Calculate the resulting stresses in the part.
• Compare these stresses with the maximum allowable for the material used.
• Resize the part as necessary.
2.3 Types of Loads and Stresses.
2.3.1 “Limit load factors” are the maximum load factors that may be expected during service (the maneuvering, gust, or ground load factors established by the manufacturer for type certification).
2.3.2 Aircraft parts may be formed out of different types of material and joined together. Each of those parts carries a load, and the fastener that brings these parts together has to carry the load from one part to the other.
2.3.3 Every aircraft is subject to different types of structural stress. Stress acts on an aircraft whether it is on the ground or in flight. Stress is defined as a load applied to a unit area of material.
2.3.4 “Tension” is a force acting against another force that is trying to pull something apart.
2.3.5 “Compression” is a squeezing or crushing force that tries to make parts smaller.
2.3.6 “Torsion” is a twisting force.
2.3.7 “Shear stress” is when one piece of material slides over another.
2.3.8 “Bending” is a combination of two forces, compression, and tension. During bending stress, the material on the inside of the bend is compressed and the outside material is stretched in tension.
2-2 Figure 2-1. Bending of a Beam
2.3.9 A n aircraft structure in flight is subjected to variable stresses due to the varying loads that may be imposed. The designer’s problem involves anticipating the possible stresses that the structure will have to endure and build the structure strong enough to withstand these stresses.
2.4 Static Loads. “Static loads” are loads that do not undergo change in magnitude or direction during a measurement procedure. Load factors are defined as follows:
2.4.1 “Limit load factors” are the maximum load factors that may be expected during service (the maneuvering, gust, or ground load factors established for type certification).
2.4.2 “Ultimate load factors” are the limit load factors multiplied by a prescribed factor of safety. Certain loads, such as the minimum ultimate inertia forces prescribed for emergency landing conditions, are given directly in terms of ultimate loads.
2.4.3 “Static test load factors” are the ultimate loads multiplied by the casting, fitting, bearing, and/or other special factors, when applicable. Where no special factors apply, the static test loads are equal to the ultimate loads.
2.4.4 “Critical static test load factors” are the greater of the maneuvering, gust, ground, and inertia load static test load factors for each direction (up, down, starboard, port, fore, and aft).
2-3 Figure 2-2. Typical Load
2.5 Structural Sizing and Analysis. Design and size your load structures, including wing spars, wing attach fittings, stabilizers, landing gear struts, etc.
2.5.1 Static tests using the load factors in Table 2-1 are acceptable for equipment installations.
The alteration needs to comply with the limit load factors as required by the aircraft’s certification basis.
Table 2-1. Ultimate Load Factors Direction of Force Applied Normal-Utility Occupant 14 CFR Part 23 (CAR 3) Acrobatic Occupant 14 CFR Part 23 (CAR 3) Items of Mass Within the Cabin 14 CFR Part 23 (CAR 3) Rotorcraft Occupant and Items of Mass Within the Cabin 14 CFR Part 27 (CAR 6) Sideward 1.5g 1.5g 4.5g 8.0g Upward 3.0g 4.5g 3.0g 4.0g Forward 9.0g 9.0g 18.0g 16.0g Downward 6.6g 9.0g - 20.0g Rearward - - - 1.5g Note 1: When equipment mounting is located externally to one side, or forward of occupants, a forward load factor of 2.0g is sufficient.
Note 2: Due to differences among various aircraft designs in flight and ground load factors, contact the aircraft manufacturer for the load factors required for a given model and location. In lieu of specific information, the factors used for the 14 CFR part 23 utility category are acceptable for aircraft that never exceed the speed of 250 knots and the factors used for 14 CFR part 23 acrobatic category.