Rev. 1977 plished. It is probable that other compromises may be necessary when adapting a specific restraint system to an aircraft in order to fit a body AC 43.13-2A of average dimensions. These compromises, however, should be permitted only when they are compatible with proper restraint functions.
FIGURE 9.5.-Acceptable mounting area-single diagonal type harness.
30° UP HORIZ. REF 5° DOWN FIGURE 9.6.--Ceiling mounted inertia reel-double over-the-shoulder type harness.
Chap 9 69
Rev. 1977 AC 43.13-2A FIGURE 9.7.-Acceptable mounting areas-double over-the-shoulder type harness.
159.-160. [RESERVED] 70 Chap 9
Rev. 1977 AC 43.13-2A Section 3. ATTACHMENT METHODS
161. STRUCTURAL ATTACHMENTS. For best results, the restraint system should be anchored to the primary aircraft structure. Design the structural attachment to spread the suddenly applied impact loads over as large an area of the structure as possible. The shoulder harness may be attached to selected secondary members which will deform slowly or collapse at a limited rate.
This will assist in dissipating the high impact #g" loads to a level tolerable to the human body.
However, the possibility of secondary members collapsing and making it difficult for an occupant to extract himself from the harness should not be overlooked.
162. FLOOR AND SEAT ATTACHMENTS. The double over-the-shoulder type harness shown in figure 9.8 may be used with either floor or seat mounting points, and typical installation methods are illustrated in figures 9.9 and 9.10. Two prerequisites necessary to ensure an effective restraint system are:
a. The seat structure and its anchorages should be capable of withstanding the additional "g" loads imposed by the restrained occupant during an abrupt deceleration. This capability may be determined by static testing in accordance with FAR 23.785, 25.785, 27.785, or 29.785, as appropriate; or, by securing a statement attesting this adequacy from the airframe manufacturer's engineering department.
b. The level of the seat back should at least be equal to the shoulder height of the seated occupant. This will reduce the inherent downward impact loads which would otherwise impart compressive forces. on the occupant's torso.
FIGURE 9.8.-Floor mounted inertia reel-double over-the-shoulder type harness.
Chap 9 251-957 0 - 77 - 4
Rev. 1977 AC 43.13-2A FIGURE 9.9.- -Typical floor mounted inertia reel installation.
FIGURE 9.10.-Typical seat mounted inertia reel installation.
Seats which utilize a fold-over type of seat back must have some type of locking mechanism so that the seat can support the loads without allowing the occupant to move forward. The lock should be of a type which has a quick release 72 to allow rear seat occupants to rapidly evacuate the aircraft. This type of installation should only be considered if other means of attachment are not available since making a folding seat rigid greatly reduces the protection afforded a passenger to the rear. When a folding seat is provided with a lock, the passenger to the rear should also be provided a shoulder restraint system, or, the back of the forward seat should be provided with sufficient absorptive material to adequately compensate for the added rigidity.
Also, the change in load distribution due to the loads being applied to the seat back may require reinforcing the seat and/or belt anchorages to meet airworthiness requirements.
163. AIRFRAME ATTACHMENTS. The method used for the attachment of shoulder harness anchorages is dependent upon the construction features of the aircraft involved.
a. Monocoque/Semimonocoque Type Constructions. Illustrations of typical aircraft members and installation methods are shown in figures 9.11 through 9.15.
b. Tube Type Construction. Various typical methods of attaching shoulder harness anchorages are shown in figure 9.16. When aircraft cable is used as a component in a shoulder harness anchorages, swage the cable terminals in accordance with the procedures contained in chapter 4 of AC 43.13-14, Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repairs."
164. STRUCTURAL REPAIR KITS. In many instances, structural repair kits are available from the aircraft manufacturer. While these kits are primarily intended for use in repairing defective or damaged structure, they may also be used as a reinforcement for shoulder harness attach fittings.
165. FLEXIBLE ATTACHMENTS. Various aircraft are designed so that fuselage members and/or skin will flex or "work." This type of structure should not be heavily reinforced for the purpose of attaching shoulder harnesses as this would defeat the design purpose. In cases such as these, use a localized reinforcement, such as shown in figure 9.15, at the attachment point.
This will allow the fuselage to flex while still maintaining a collapsible structure to absorb the loads encountered in a crash.
Chap 9
kev. 1977 AC 43.13-2A FIGURE 9.11.-Typical bulkhead reinforcement installation.
FIGURE 9.12.-Typical wing carry-through member installation.
Chap 9 73
AC 43.13-2A FIGURE 9.13.-Typical hat section reinforcement installation.
FIGURE 9.14.-Typical stringer section reinforcement installation.
166. SIMPLIFIED INSTALLATION CRITERIA. To encourage the addition of shoulder restraints to existing aircraft with a minimum of testing and engineering necessary, yet provide a satisfactory restraint, the following general conditions will be acceptable.
a. Utilize the original seat belt attachments and either the original or a new belt provided with shoulder harness fittings.
b. Use webbing approved for standard seat belts (TSO-C22f).
c. Use hardware approved for use on seat belts per TSO-C22f.
d. Secure the lower end of the shoulder strap to one side of the original seat belt or belt anchorage.
e. Use a mount for the shoulder restraint in- 74 Rev. 1977 dependent of the seat such as the aft or ceiling mounts per paragraph 128.
f. Test the added mount by applying a test load of at least 500 pounds forward at the shoulder point.
167. ENGINEERING APPROVAL. Installations which involve cutting or drilling of critical fuselage members or skin of pressurized aircraft will usually require engineering evaluation. For this reason it may be desirable to contact the airframe manufacturer to obtain his recommendations.
FIGURE 9.15.-Typical stringer section reinforcement installation.
Chap 9
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