Rev. 1977 АС 43.13-2A FIGuRE 9.16.-Typical attachment to tubular members (adequate chafing protection for tube should be provided. Detail omitted for clarity.)
168.-175. [RESERVED] Chap 9 75
Rev. 1977 AC 43.13-2A Chapter 10. BATTERY INSTALLATIONS Section 1. GENERAL
176. GENERAL. This section contains structural and design considerations for the fabrication of aircraft battery installations.
177. LOCATION REQUIREMENTS. The battery location and/or its installation should provide:
a. Accessibility for Battery Maintenance and Removal. The electrolyte level of the battery needs frequent checking; therefore, install the battery so that it is readily accessible for this service without the removal of cowling, seats, fairings, etc. Inaccessibility is often the source of neglect of this important piece of equipment.
Certain types of batteries cannot be conveniently serviced while installed. Therefore, install and/ or locate the battery so that it can be readily removed and reinstalled.
b. Protection from Engine Heat. The instaliation should protect the battery from extreme engine heat, which would be detrimental to the battery's service life and reliability. Such protection should provide for the temperatures encountered after engine shutdown as well as during engine operation. When locating the battery within the engine compartment, choose a location that will not interfere with the flow of engine-cooling air.
c. Protection from Mechanical Damage. Vibration and other shock loads are a major cause of short battery life. Whenever possible, install the battery in a manner or location that will minimize damage from airframe vibration and prevent accidental damage by passengers or
d. Passenger Protection. Enclose the battery in a box or other suitable structure to protect FIGURE 10.2.-Typical battery box installation in aft fuselage area, below cabin floorboards, or may also FIGURE 10.1.-Typical battery box installation in be adapted for within wing locations (shaded poraft fuselage area. tions indicate original structure).
Chap 10 77
AC 43.13-2A passengers from any fumes or electrolyte that may be spilled as a result of battery overheating, minor crash, inverted flight, and/or rapid decompression if the battery is located within the aircraft'ș pressure vessel.
e. Airframe Protection. Protect the airframe structure and fluid lines by applying asphalticor rubber-base paint to the areas adjacent to and below the battery or battery box. Apply paralketone, heavy grease, or other comparable protective coating to control cables in the vicinity of the battery or battery box. Damage to adjacent fabric covering and electrical equipment can be minimized by providing a battery sump jar containing a neutralizing agent, properly locating battery drains and vent discharge lines, and adequately venting the battery compartment.
178. DUPLICATION OF THE MANUFACTURER'S INSTALLATION. The availability of readymade parts and attachment fittings may make it desirable to consider the location and type of installation selected and designed by the airframe manufacturer. Appreciable savings in time and FIGURE 10.3.-Typical battery box installation in aft fuselage area (shaded portions indicate original structure).
78 Rev. 1977 work may be realized if previously approved data and/or parts are used.
179. OTHER INSTALLATIONS. If the battery installation has not been previously approved, or if the battery is to be installed or relocated in a manner or location other than provided in previously approved data, perform static tests on the completed installation as outlined in chapter 1 of this handbook. Because of the concentrated mass of the battery, the support structure should also be rigid enough to prevent undue vibration which would lead to early structural failure. Typical illustrations of battery support structure are shown in figures 10.1 thru FIGURE 10.4.Typical battery box installation suspended from cabin floorboard section.
180.-185. [RESERVED] Chap 10
Rev. 1977 AC 43.13-2A Section 2. INSTALLATION
186. SECURING THE BATTERY. Install the battery box or holddowns in such a manner as to hold the battery securely in place without subjecting it to excessive localized pressure which may distort or crack the battery case. Use rubber or wooden blocks protected with parafin or asphaltic paint as spacers within the battery box, as necessary, to prevent shifting of the battery and possible shorting of the battery terminals or cables. Also, provide adequate clearance between the battery and any bolts and/or rivets which may protrude into the battery box or compartment.
187. VENTING. Provide suitable venting to the battery compartment to prevent the accumulation of the hydrogen gas evolved during operation. For most aircraft batteries, an airfiow of 5 cu. ft. per minute is sufficient to purge the battery compartment of explosive concentrations of hydrogen.
a. Manifold Type. In this type of venting, one or more batteries are connected, via battery or battery box vent nipples, to a hose or tube manifold system as shown in figure 10.5. Fasten such hoses securely to prevent shifting and maintain adequate bend radii to prevent kinking.
(1) The upstream side of the system is connected to a positive pressure point on the aircraft, and the downstream side is usually discharged overboard to a negative pressure area. It is advisable to install a battery sump jar in the downstream side to neutralize any corrosive vapors that may be discharged.
(2) When selecting these pressure points, select points that will always provide the proper direction of airflow through the manifold system during all normal operating attitudes. Reversals of flow within the vent system should not be permitted when a battery sump jar is installed, as the neutralizing agent in the jar may contaminate the electrolyte within the battery.
b. Free Airflow Type. Battery cases or boxes that contain louvers may be installed without an individual vent system, provided:
(1) The compartment in which the battery is installed has sufficient airflow to prevent the accumulation of explosive mixtures of hydrogen;
(2) Noxious fumes are directed away from occupants; and
(3) Suitable precautions are taken to prevent corrosive battery fluids or vapors from damaging surrounding structure, covering, equipment, control cables, wiring, etc.
188. DRAINS. Position battery compartment drains so that they do not allow spillage to come in contact with the aircraft during either ground or flight attitudes. Route the drains so that they have a positive slope without traps. Drains should be at least ½" in diameter to prevent clogging.
VENT NIPPLE
MANIFOLD VENT TUBE FIGURE 10.5.-Battery with integral vent nipples.
Chap 10 79
AC 43.13-2A
189. ELECTRICAL INSTALLATION.
a. Cables/Connectors. Use cables and/or connectors that are adequately rated for the current demand and are properly installed (See AC
43.13-1A, Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repair," chapter 11). It may be necessary to contact the battery manufacturer to determine current value of the battery at the 5-minute discharge rate.
Cable size can also be selected by using the same gage as used on a previously approved production aircraft with the same battery.
(1) The cables should be of sufficient length to prevent undue strain on the battery connector or terminals.
(2) Clamp and protect cables, including the bus, in a very secure manner. Since these units are not fused, any fault could cause loss of the entire electrical system in addition to a possible fire hazard.
BATTERY RELAY
IO PRIMARY BUS Rev. 1977
(3) Route cables so that cable or terminals cannot short to the battery case or hold-down frame.
(4) Route cables outside the battery box whenever practicable to prevent corrosion by acid fumes. When internal routing is unavoidable, protect the cable inside the box with acidproof tubing. Assure that cables will not be inadvertently reversed on the battery terminals either by proper cable lengths and clamps or, if this is not practicable, use conspicuous color coding.
b. Battery Cutoff. Install a battery cutoff relay to provide a means of isolating the battery from the aircraft's electrical system. An acceptable battery cutoff circuit is shown in figure
10.6. Mount the relay so that the cable connecting the relay to the battery is as short as feasible, in any case not to exceed two feet, to reduce the possibility of a fire occurring because of a short within this section of cable.
GENERATOR / ALTERNATOR
CONTROL
CIRCUIT
BATTERY FIGURE 10.6. -Typical battery cutoff and generator alternator control circuit.
190.-195. [RESERVED] 80 Chap 10
Rev. 1977 AC 43.13-24 Section 3. REPLACEMENT OF LEAD-ACID BATTERIES WITH
NICKEL-CADMIUM BATTERIES bility, and a high degree of reliability. The teries requires careful evaluation of certain areas. fill a need for a power source that will provide large amounts of current, fast recharge capa- exchange of lead-acid for nickel-cadmium bat- 196. GENERAL. Nickel-cadmium batteries ful- the aircraft, it is important that the battery be located where it can easily be inspected, removed, and installed. Some battery cases are designed with viewports on each side of the case for visual monitoring of the cell electrolyte level. If cadmium batteries are generally not serviced in
197. ELECTRICAL ANALYSIS. The ampere hour this type of case is to be utilized, consideration capacity of a nickel-cadmium battery is selected should be given to the location of the battery to accommodate the aircraft load requirements. compartment to accommodate this feature.
When making this selection, the following items 199. STRUCTURAL REQUIREMENTS. Most lead-acid should be considered. battery compartments provide adequate structure
a. The low internal resistance permits it to re- attachment for the installation of nickel-cadcharge very quickly. This high recharge rate mium batteries. However, cantiliver supported current. Total system load (battery recharging plus system loads) must not exceed the pre-estab- can exceed the generator rated capacity and de- prive essential circuits of necessary operating modified to compensate for an increased over- hang moment. This may be caused by a change for nickel-cadmium battery installations unless battery boxes/compartments may not be suitable lished electrical capacity. in battery shape and c.g. location even though the replacement battery weighs less than the following: of the batteries to make sure a reduced capacity nickel-cadmium battery is adequate regarding the b. Compare the discharge characteristics curves installation, perform a static test as outlined in original lead-acid battery. (See fig. 10.7.) When ever the total installation weight and/or the overhang moment exceed those of the original
(1) Ability to provide engine starting or chapter 1 of the handbook. If the battery comcranking requirements. Turbine engines require partment is to be relocated, follow the procedures an initial surge of approximately 1200 amperes outlined in Sections 1 and 2 of this chapter.
which tapers off within 10 seconds to approximately 800 amperes cranking current. Recipro- 200. ISOLATION OF BATTERY CASE. Because of cating engines require approximately 100 am- the material from which nickel-cadmium battery peres cranking current. cases are generally made (stainless or epoxy low temperature starting. Nickel-cadmium bat- teries deliver their rated capacity when the (2) Ability to provide sufficient capacity for coated steel), it is desirable to electrically isolate the case from aircraft structure. This will elimi- nate the potential discharge current produced ambient temperature range is 70° to 90° F. In- when spillage or spewage of the electrolyte procreased battery capacity will offset the effects of vides a current path between the cell terminal low-temperature starting. or connector and exposed metal of the battery case. This isolation is also desirable in that it
198. MAINTENANCE CONSIDERATIONS. To pro- vide for ease of inspection and because nickel- ing the generator output to the stucture. could prevent a fault within the battery or fault- Chap 10 81
AC 43.13-2A Rev. 1977 of nickel-cadmium battery cases, one with vent nozzles and the type with viewports.
a. The vent nozzle type utilizes vent hoses to evacuate the gas overboard by use of forced air
- DI - REPLACEMENT or by venturi effect.
BATTERY b. Battery cases with viewports or louvers must OUTLINE have an air flow sufficient to keep the mixture of air and hydrogen below 4 percent. The gases from this type of case are evacuated into the battery compartment. Regardless of the ventilation system used, the air flow should be a minimum of 5 cubic feet per minute.
ORIGINAL
LEAD-ACID
BATTERY C.G. (WI)
REPLACEMENT
NICKEL-CADMIUM BATTERY C.G. (Wz) FIGURE 10.7.-Change in cantilever support battery overhang moment.
Example:
Original Overhang Moment with Lead- Acid Battery W1 = 25 1b., D1 = 4 inches 4 inches X 25 1b., = 100 in. - 1b.
New Overhang Moment with Replacement Nickel-Cadmium Battery Wz = 19.5 1b., Dz = 6 inches 6 inches X 19.5 1b. = 117 in. - 1b.
201. VENTILATION. During the charging process, nickel-cadmium batteries produce hydrogen and oxygen gases. This occurs near the end of the charging cycle when the battery reaches what is called the gassing potential. To avoid a buildup of these gases, and possible accidental ignition, ventilation should be provided to evacuate this gas from the aircraft. There are two types
202. PREINSTALLATION REQUIREMENTS. Inspect the replacement battery for possible damage incurred during shipment or storage. Give particular attention to signs of spilled liquid within the shipping container, as it may indicate a damaged cell. Follow procedures outlined in Section 2 for battery venting and electrical connec tions.
a. Preinstallation battery servicing. Check at least the following in accordance with the battery manufacturer's instruction:
(1) Remove the shipping plugs (if used) and clean and install the filler cap vent plugs.
(2) Check the tightness of terminal hardware including each cell connector strap to the proper torque values.
(3) Check the polarity of each cell to be sure they are connected in the proper series or sequence.
(4) Charge and check battery voltage and electrolyte level.
b. Compartments or battery boxes which have previously housed lead-acid batteries must be washed out, neutralized with ammonia or a baking soda solution, allowed to dry thoroughly, and painted with alkaline-resistant paint. Remove all traces of sulfuric acid and its corrosion products from the battery vent system to prevent contamination of the potassium hydroxide electrolyte and/or possible damage to the cell case material. Replace those parts of the vent system which cannot be thoroughly cleansed (hoses, etc.). When sump jars are incorporated into the vent system, replace the old pad with a new one that has been saturated in a three-percent solution (by weight) of boric acid and water.
82 Chap 10
Rev. 1977
203. SECURING THE BATTERY. Follow the procedures outlined in Section 2 of this chapter.
Make certain that the holddown bolts are not drawn up so tightly that the battery case/cover becomes distorted. Should the cover become distorted, there is a possibility that the cell terminal hardware may eventually puncture the neoprene cover liner used in many batteries, and short Caution: In installations where care has been taken to isolate the battery cases, inadvertent grounding may occur through improper or careless use of safety wire. Use no wood in nickelcadmium battery boxes as it becomes conductive with time causing a current flow from the battery case to ground. Use only fiberglass or other acceptable material as liners and spacers in the battery box.
204. VOLTAGE AND CURRENT REGULATION. It is essential that the charging voltage and current be checked and, if necessary, the voltage regulator reset to meet the requirements of the nickelcadmium battery being installed. IMPORTANT -improper charging current or voltage can destroy a battery in a short period of time.
Chap 10 AC 43.13-2A
205. WEIGHT AND BALANCE. After installation of the nickel-cadmium battery the weight and balance of the aircraft should be recomputed if:
a. The weight of the nickel-cadmium battery is different from that of the original lead-acid battery.
b. The location of the nickel-cadmium battery is different from that of the original lead-acid battery.
Weight and balance procedures for aircraft are contained in chapter 13 of AC 43.13-1A.
206. RESTORATION OF LEAD-ACID BATTERIES.
When lead-acid batteries are restored in lieu of nickel-cadmium batteries the procedures contained in sections 1, 2, and 3 of this chapter should be used. Structural requirements are referenced in paragraph 199 and figure 10.7.
Airframe protection is specified in paragraph
177. Follow the procedures outlined in section 2 of this chapter for battery security, battery venting, and battery drains. Assure that all electrical requirements have been accomplished.
Place emphasis on aircraft weight and balance.
Refer to chapter 13 of AC 43.13-1A.
207.-210. [RESERVED] 83
Rev. 1977 AC 43.13-2A Chapter 11. ADDING OR RELOCATING INSTRUMENTS
211. GENERAL. This chapter contains struc- niques, and Practices--Aircraft Inspection and tural and design information to be considered Repair," chapter 2, section 3, for methods and when aircraft alterations involving the addition techniques of retaining structural integrity.
and relocation of instruments are being made. b. Plumbing. Refer to the manufacturer's in-
212. PREPARATION. First determine what regu- structions for fabrication, routing and installalation, (CAR 3, 4b, FAR 23, 25, etc.) is the tion of instrument system lines. Advisory Cirbasis for the aircraft type certificate. That regu- cular 43.13-1A provides information regarding lation establishes the structural and performance the installation and fabrication of aircraft plumbrequirements to be considered when instruments are to be added or relocated. c. Vacuum Source. Minimum requirements strument panel installation. vides information by which structural integrity may be determined. Chapter 2, paragraph 23a through f provides information pertinent to in- a. Structure. Chapter 1 of this handbook pro- ments: Installation." for installation and performance of instrument vacuum systems are covered in the applicable FAR Airworthiness Standards under "Instru- (1) In the absence of specific requirements
b. Location. Consult the applicable regulation tor vacuum pump installation, refer to FAR Part 25, section 25.1433 for guidance. It is detion and arrangement. for the specific requirements for instrument loca- sirable to install a "T" fitting between the pump and relief valve to facilitate ground checking and
(1) In the absence of specific requirements, adjustment of the system.
installation of IFR flight instruments in a "T" (2) When a venturi tube power source is arrangement is recommended. Locate the air- used, it should not be taken for granted that a craft attitude indicator at top center, airspeed venturi will produce sufficient vacuum to propindicator to the left, altimeter to the right and erly operate one or more instruments. Many of directional indicator directly below, thus form- the venturi tubes available for aircraft have a flow ing the letter "T. When a radio altimeter is rate of approximately 2.3 cubic feet per minute used, the indicator may be placed on the im- at 3.75 inches of mercury (in. Hg) vacuum.
mediate right of the attitude indicator with the Therefore, it is essential that the vacuum load pressure altimeter to the right of the radio altim- requirements be carefully evaluated.
eter indicator. (3) Vacuum loads may be calculated as fol-
213. INSTALLATION. Mount all instruments so they are visible to the crewmember primarily (a) Gyroscopic instruments require optiresponsible for their use. Mount self-contained mum value of airflow to produce their rated rotor gyroscopic instruments so that the sensitive axis speed. For instance, a bank and pitch indicator is parallel to the aircraft longitudinal axis. requires approximately 2.30 cubic feet per minute 23a through f of this handbook. Refer to the Circular 43.13-1A, Acceptable Methods, Tech- aircraft manufacturer's instructions and Advisory such as adding holes in the instrument panel to mount instruments, refer to chapter 2, paragraph a. Structure. When making structural changes per minute and a pressure drop of 4.00 in. Hg. indicator consumes approximately 1.30 cubic feet would be marginal. Similarly, the directional gyro The turn and bank indicator has a flow require- of 4.00 in. Hg. Therefore, operating an instru- ment requiring 4.00 in. Hg from one venturi for its operation and a resistance or pressure drop Chap 11 85
Rev. 1977 AC 43.13-2A ment of 0.50 cubic feet per minute and reaches this flow at a pressure drop of 2.00 in. Hg. The Table 11.2.-Equivalent straight tube line drops for 90° elbows.
above instruments are listed in Tables 11.1 and Pressure drop in a 90° elbowo
11.3. Optimum values are shown in Table 11.3. Tubing size in terms of length of straight It should be noted that the negative pressure tube equivalent to a 90° elbow air source must not only deliver the optimum O.D inch Wall thickness inch Feet value of vacuum to the instruments, but must ¼ .035 0.28 Table 11.1.-Instrument air consumption.
.035 0.46 dir consumption at -042 0.62 sea level .042 0.81 Instrument Differential drop in. Hg Cubic ¾ .049 0.98 suction feet/per (Optimum) minute 1 .049 1.35 AUTOMATIC PILOT SYSTEM 3 Determine the pressure drop through Directional gyro control unit (Types A-2, A-3, & A-3A) across mount assembly 5.00 2.15* 22.48 feet (20 feet + 2.48 equivalent feet) of ½ O.D. X .042 tubing at 4.10 CFM flow. From fig- Bank & climb gyro control unit ure 11.1, pressure drop per each 10-foot length = across mount assembly 5.00 3.85* 0.68 in. Hg. Divide 22.48 feet of tubing by 10 to Total 6.00* obtain the number of 10-foot sections, i.e., AUTOMATIC PILOT SYSTEM Directional gyro control unit (Type A-4) 5.00 3.50* 22.48 ÷ 10=2.248. Multiply the number of sec- tions by 0.68 in. Hg to obtain the pressure drop Bank & climb gyro control unit 5.00 5.00* through the system. (0.68 X 2.248=1.53 in. Hg) Total 8.50* 4 The pump must therefore be capable Bank & pitch indicator Directional gyro indicator 4.00 4.00 2.30 1.30 of producing a minimum pressure differential of Turn & bank indicator 2.00 .50 Table 11.3.-Differential pressure across instrument (*) Nore.—Includes air required for operation of pneumatic inlet and outlet.
relays.
Suction in inches also have sufficient volume capacity to accom- of mercury modate the total flow requirements of the various Instrument Mini- Opti- Maxiinstruments which it serves. mum mum mum
(b) To calculate the flow requirements of elbows and 20 feet of line (½ O.D. x .042) tub- a simple vacuum system, assume four right-angle AUTOMATIC PILOT SYSTEM (Types A-2, A-3, & A-3A) ing Directional gyro control unit across mount assembly 4.75 5.00 5.25 1 Assume the flow requirements for: Bank & climb gyro control unit Turn & bank indicator .50 CFM across mount assembly 4.75 5.00 5.25 Directional gyro indicator Bank & pitch indicator 1.30 CFM 2.30 CFM Gauge reading (differential gauge in B & C control unit) 3.75 4.00 4.25
AUTOMATIC PILOT SYSTEM Total flow required 4.10 CFM (Type A-4) Directional gyro control unit 3.75 5.00 5.00 O.D. x .042 elbow is equivalent to 0.62 feet of Bank & pitch indicator Bank & climb gyro control unit 3.75 3.75 5.00 4.00 5.00 5.00 Directional gyro indicator 3.75 4.00 5.00 sure drop of four 90° elbows is equivalent to 2.48 Turn & bank indicator 1.80 2.00 2.20 feet of tubing.
Chap 11 86
Rev. 1977 AC 43.13-2A
• 035 PRESSURE DROP PER TEN FOOT LENGTH - INCHES OF MERCURY 1/4 x 035 TUBING SIZE 5/16 x 3/8 × .035 • 042 1/2 x 5/8 x • 042 3/4 x • 049
0.15 1 x
0.1
0.5 0.75 1 1.5 2 3 4 5 6 8 10 15 20
AIR FLOW - CUBIC FEET PER MINUTE
PRESSURE DROP DATA FOR SMOOTH TUBING FIGURE 11.1 Chap 11
AC 43.13-2A
5.53 in. Hg, i.e., 4.00 in. Hg for maximum instrument usage + 1.53 in. Hg (determined) at a flow of 4.10 cubic feet per minute.
d. Filter. Filters are used to prevent dust, lint and other foreign matter from entering the instrument and vacuum system. Filters may be located at the instrument intake port or at the manifold intake port when instruments are interconnected. Determine that the capacity of the filter is as great or greater than the capacity of the vacuum system. Assure that there is no pressure drop across the filter media.
e. Electrical Supply for Instruments. Guidelines for the installation of instrument electrical wiring and power source are provided in Advisory Circular 43.13-1A, chapter 11, sections 2 and 3, and Chapter 16, section 3.
NorE: Strict conformance to the shielding specifications supplied by compass manufacturers is recommended in all installations to eliminate any possibility of spurious
f. Instrument Lighting. Instrument lighting must be installed in accordance with the regulations that are applicable to the aircraft type cer- sine it yes or.
reflection of the lights is unsatisfactory, provide a shield or a means for controlling the intensity of illumination.
g. Magnetic Headings. Calibrate magnetic instruments with the powerplants operating. After this initial calibration, switch all nav/com and electrical equipment, such as windshield wipers and defrosters, "on" to determine if any electrical system interference affects the instrument calibration. If the calibration is affected, prepare an instrument placard identifying the compass headings with the equipment "on" and also with the equipment "off." Placard in accordance with par. 214f of this chapter.
88 Rov. 1977
214. TESTING, MARKING, AND PLACARDING.
a. Testing the Venturi Tube-Powered Systems.
At normal inflight cruise speed, check the venturi tube-powered system to assure that the required vacuum pressure is being supplied.
b. Testing the Vacuum Air Pump Powered System. When the system is powered by vacuum air pumps, check the system while the pumps are operating at their rated r.p.m. and measure the vacum available to the instruments.
c. Testing of Altimeters and Static Systems.
When checking the operation of an altimeter static system to determine that the system is free of any contaminating materials, be sure to disconnect the plumbing from all air operated instruments before purging the lines with dry air or nitrogen since the pressure necessary for purgmay damage any connected instrument.
Static system test procedures are provided in FAR 43, Appendix E.
d. Testing electrical supply (instruments). Check the voltage at the instrument terminals and determine that it is equal to the manufacturer's recommended values.
e. Fuel, Oil, and Hydraulic (Instrument Supply).
Measure the fluid pressure at the instrument end of the line to determine whether it is equivalent to that at the pressure source.
f. Instrument Markings and Placards. When additional instruments are installed they must be appropriately marked. Refer to the applicable CAR/FAR under "Markings and Placards" for specific instrument marking and placard requirements.
215.-240. [RESERVED] Chap 11