4-8 Figure 4-4. Use Bushings for All Screws N ote: Carbon fiber composite material, while conductive, has not been found to be adequate as a ground plane.
4.11.5 Refer to AC 43.13-1, Chapter 3, Fiberglass and Plastics, for acceptable methods, techniques, and practices applicable to fiberglass and plastics.
4.12 Antenna Feed Line Balun.
4.12.1 Antenna cables (electrical feed lines) may be designed to be electrically balanced or unbalanced. Certain antenna designs incorporate dual elements with a requirement for balanced input. In these cases, standard cables that are unbalanced are generally employed for the cable run, and a balancing transformer is located at the antenna feed connection.
4.12.2 A balun is a device that converts an unbalanced feed into a balanced input and may include a transformer that matches feed impedance to provide maximum signal transfer.
Follow the manufacturer’s installation procedures when a balun is required. Some balun designs require the balun to be grounded to the airframe.
4.12.3 Refer to AC 43.13-1, Chapter 11, Aircraft Electrical Systems, for bonding practices.
4-9 Figure 4-5. Typical Dipole Antenna Assembly
4-10 Figure 4-6. Typical VOR Balun
4.13 Antenna Repair. Painting an antenna or applying protective coatings or devices that are not approved are not allowed under this AC. Paint is an RF detuner. If an antenna is painted in the field, paint type and paint thickness present uncontrolled variables that will affect an antenna’s performance and may result in the antenna no longer meeting its specifications or Technical Standard Order (TSO).
4-11 Figure 4-7. ADF Loop Fi gure 4-8. ADF Combined Sense Loop Fi gure 4-9. Communications (COM) Whip
4-12 Figure 4-10. COM Whip Bent Fi gure 4-11. Emergency Locator Transmitter Fi gure 4-12. Global Positioning System
4-13 Figure 4-13. Glideslope Fi gure 4-14. Marker Fi gure 4-15. Combined COM/VOR
4-14 Figure 4-16. VOR Rabbit Ear Fig ure 4-17. VOR Blades
4-15 Figure 4-18. Transponder/DME Probe Fig ure 4-19. DME/Transponder Blade
5-1 CHAPTER 5. ANTICOLLISION AND SUPPLEMENTARY LIGHT INSTALLATION
5.1 Purpose. This chapter gives procedures and standards to be used when replacing older rotating beacon assemblies and wing lights with strobe or other anticollision systems.
This chapter assumes that the newer units have FAA approval in the form of a Parts Manufacturer Approval (PMA) or Technical Standard Order (TSO) and not an experimental or aviation unit.
5.2 Hazards and Warnings. When installing anticollision lights, take care to ensure the unit is properly grounded, the airframe structure can support the new unit, and the aircraft wiring is of the correct size. Mechanics should take special precautions to protect their eyes when testing the new unit. Strobe lights are especially hazardous in dark or darkened hangars when activated.
5.3 Regulations and Other References. The operational requirements for anticollision lights can be found in 14 CFR § 91.205. Information regarding installation requirements for nontransport category aircraft is included in 14 CFR §§ 23.1401 and 27.1401. Additional information can be found in AC 20-30, Aircraft Position Light and Anticollision Light Installations; AC 20-74, Aircraft Position and Anticollision Light Measurements; and Civil Air Regulation (CAR) 6, Rotorcraft Airworthiness; Normal Category. Aircraft for which an application for type certificate (TC) was made before April 1, 1957, may conform to either the above regulations or to the following standards:
5.3.1 Anticollision lights, when installed, should be installed on top of the fuselage or tail in such a location that the light will not impair the flight crewmembers’ vision and will not detract from the conspicuity of the position lights. If there is no acceptable location on top of the fuselage or tail, a bottom fuselage or wing tip installation may be used.
5.3.2 The color of the anticollision light must be either aviation red or aviation white in accordance with the specifications of 14 CFR § 23.1397 or 14 CFR § 27.1397, as applicable.
5.3.3 The arrangement of the anticollision light system (i.e., number of light sources, beam width, speed of rotation, other characteristics, etc.) must give an effective flash frequency of no less than 40 but not more than 100 cycles per minute. The effective flash frequency is the frequency at which the aircraft’s complete anticollision light system is observed from a distance and applies to each sector of light, including any overlaps that exist when the system consists of more than one light source. In overlaps, flash frequencies may exceed 100 but not more than 180 cycles per minute.
5.3.4 The system must consist of enough lights to illuminate the vital areas around the aircraft, considering the physical configuration and flight characteristics of the aircraft. The field of coverage must extend in each direction within at least 75 degrees above and 75 degrees below the horizontal plane of the aircraft. The minimum light intensity and minimum effective intensities are given in 14 CFR §§ 23.1401 and 27.1401, respectively.
5.3.5 Supplementary lights may be installed, in addition to position and anticollision lights required by applicable regulations, provided that the required position and anticollision
5-2 lights are continuously visible and unmistakably recognizable and their conspicuity is not degraded by such supplementary lights.
5.4 Operational Considerations: Crew Vision. Partial masking of the anticollision light may be necessary to prevent direct or reflected light rays from any anticollision or supplementary light from interfering with crew vision. Determine if the field of coverage requirements are met. An acceptable method of preventing light reflection from the propeller disc, nacelle, or wing surface is an application of nonreflective paint on surfaces that present a reflection problem. Perform a night flight check to ensure that any objectionable light reflection, sometimes known as flicker vertigo, has been eliminated.
Enter a notation to that effect in the aircraft records.
5.5 Installation Considerations.
5.5.1 Communication and Navigation. Ensure that the installation and operation of any anticollision or supplementary light does not interfere with the performance of installed communication or navigation equipment. Capacitor discharge light (strobe) systems may generate radio-frequency interference (RFI). This radiated interference can be induced into the audio circuits of communication or navigation systems and is noticeable by audible clicks in the speaker or headphones. The magnitude of RFI disturbance does not usually disrupt the intelligence of audio reception.
5.5.2 Precautions. RFI can be reduced or eliminated by observing the following precautions during installation of capacitor discharge light systems:
1. Locate the power supply at least 3 feet from any antenna, especially antennas for radio systems that operate in the lower frequency bands.
2. Ensure that the lamp unit (flash tube) wires are separated from other aircraft wiring, placing particular emphasis on coaxial cables and radio equipment input power wires.
3. Make sure that the power supply case is adequately bonded to the airframe.
4. Ground the shield around the interconnecting wires between the lamp unit and power supply at the power supply end only.
5.6 Markings and Placards. Identify each switch for an anticollision/supplementary light and indicate its operation. The aircraft should be flight tested under haze, overcast, and visible moisture conditions to ascertain that no interference to pilot vision is produced by operation of these lights. If found unsatisfactory by test or in the absence of such testing, a placard should be provided to the pilot stating that the appropriate lights be turned off while operating in these conditions.
5.7 Electrical Installation. Install an individual switch for the anticollision light or supplementary light system that is independent of the position light system switch. Data for the installation of wiring, protection devices, and generator/alternator limitations is contained in AC 43.13-1, Acceptable Methods, Techniques, and Practices—Aircraft Inspection and Repair, Chapter 11, Aircraft Electrical Systems. Ensure that the terminal voltage at each light is within the limits as prescribed by the manufacturer.
5-3
5.8 Alteration of Structure.
5.8.1 The simplest light installation is to secure the light to a reinforced fuselage skin panel.
The reinforcement doubler shall be of equivalent thickness, material, and strength as the existing skin. (Install as shown in Figure 5-1.)
Figure 5-1. Typical Anticollision or Supplementary Light Installation in a Skin Panel (Unpressurized)
5.8.2 When a formed angle stringer is cut and partially removed, position the reinforcement doubler between the skin and the frame. The doubler is to be equivalent to the stringer in thickness and extend lengthwise beyond the adjacent fuselage frames. The distance between the light and the edge of the doubler is to be twice the height of the doubler flange (see Figure 5-2, Typical Anticollision or Supplementary Light Installation Involving a Cut Stringer (Unpressurized), for typical installation).
5-4 Figure 5-2. Typical Anticollision or Supplementary Light Installation Involving a Cut Stringer (Unpressurized)
5.8.3 Engineering evaluation is required for installations involving the cutting of complex formed or extruded stiffeners, fuselage frames, or pressurized skin of pressurized aircraft.
5.8.4 Vertical stabilizer installations may be made on the aircraft if the stabilizer is large enough in cross-section to accommodate the light installation and if aircraft flutter and vibration characteristics are not adversely affected. Locate such an installation near a spar, and add formers as required to stiffen the structure near the light. A typical installation is shown in Figure 5-3, Typical Anticollision or Supplementary Light Installation in a Fin Tip.