Par 105 Page 4 structure and attachments are acceptable. Should permanent deformation occur after 3 seconds, modifications or reinforcements are required to the affected structure. Additional load testing is not necessary.
e. Static tests may need to be reviewed by an FAA Engineer so that appropriate limitations, procedures, checks and balances may be applied to mitigate any risks.
106. MATERIALS AND WORKMANSHIP. Use materials conforming to an accepted Government or industry standard such as Army/Navy and Air Force/Navy (AN) National Aerospace Standards (NAS), Technical Standard Order (TSO), or Military Specifications (MIL-SPEC).
a. Suitability and durability of materials used for parts, the failure of which could adversely affect safety, must:
(1) Be established by experience or tests;
(2) Meet approved specifications that ensure the strength and other properties, assumed in the design data; and
(3) Take into account the effects of environmental conditions, such as temperature and humidity, expected in service.
b. Workmanship must be of a high standard.
107. MATERIAL STRENGTH PROPERTIES AND DESIGN VALUES. Material strength properties must be based on enough tests of material meeting specifications to establish design values on a statistical basis such as Metallic Materials Properties D Specification (MIL-HNDK-5). Design values must be chosen to minimize the probability of structural failure due to material variability. Except as provided in subparagraph e below, compliance with this paragraph must be shown by selecting design values that ensure material strength with the following probabilities:
a. Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component ― 99 percent probability with 95 percent confidence.
b. For redundant structure, in which the failure of individual elements would result in applied loads being safely distributed to other load carrying members ― 90 percent probability with 95 percent confidence.
c. The effects of temperature on allowable stresses used for design in an essential component or structure must be considered where thermal effects are significant under normal operating conditions.
d. The design of the structure must minimize the probability of catastrophic fatigue failure, particularly at points of stress concentration.
e. Design values greater than the guaranteed minimums required by this paragraph 107 may be used where only guaranteed minimum values are normally allowed. For example, if a “premium selection” of the material is made, in which, a specimen of each item is tested before use to determine if the actual strength properties of that particular item are equal or exceed those used in design.
108. FASTENERS. Use hardware conforming to an accepted Government or industry standard such as AN, NAS, TSO, or MIL-SPEC. Attach equipment in such a way that prevents loosening in service due to vibration.
a. Each removable fastener must incorporate two retaining devices in case one retaining device should fail during flight operations.
b. Fasteners and their locking devices must not be adversely affected by the environmental conditions associated with the particular installation.
c. No self-locking nut may be used on any bolt subject to rotation in operation, unless a nonfriction locking device is used in addition to the selflocking device.
109. PROTECTION OF STRUCTURE. Provide protection against deterioration or loss of strength due to corrosion, abrasion, electrolytic action, or other causes. Each part of the structure must:
a. Be suitably protected against deterioration or loss of strength in service due to any cause, including:
(1) Weathering,
(2) Corrosion, and
(3) Abrasion.
b. Have adequate provisions for ventilation and drainage.
110. ACCESSIBILITY. Provide adequate provisions to permit close examination of equipment or adjacent parts of the aircraft that regularly require inspection, adjustment, lubrication, etc. For each part that requires maintenance, inspection, or other servicing, appropriate means must be incorporated into the aircraft design to allow such servicing to be accomplished.
111. AFFECTS ON WEIGHT AND BALANCE.
Assure that the altered aircraft can be operated within the weight and center of gravity ranges listed in the FAA type certificate (TC), data sheet, or Aircraft Listing Aircraft Specification. When adding items of mass to the aircraft, the effect on the empty weight and balance should be considered and documented in the aircraft weight and balance.
Determine that the altered aircraft will not exceed maximum gross weight. (If applicable, correct the loading schedule to reflect the current loading procedure.) Consult the current edition of AC 43.13-1, Acceptable Methods, Techniques, and Practices―Aircraft Inspection and Repair, for weight and balance computation procedures.
112. AFFECTS ON SAFE OPERATION. Install equipment in a manner that will not interfere with or adversely affect the safe operation of the aircraft (controls, navigation equipment operation, etc.).
a. The factor of safety prescribed in 14 CFR part 23, § 23.303 must be multiplied by the highest pertinent special factors of safety prescribed in 14 CFR §§ 23.621 through 23.625 for each part of the structure where strength is:
(1) Uncertain,
(2) Likely to deteriorate in service before normal replacement, or
(3) Subject to appreciable variability because of uncertainties in manufacturing processes or inspection methods.
b. Unless otherwise provided, a factor of safety of 1.5 must be used.
113. CONTROLS AND INDICATORS. Locate and identify equipment controls and indicators so they can be operated and read from the appropriate crewmember position.
114. PLACARDING. Label equipment requiring identification and, if necessary, placard operational instructions. Amend weight and balance information as required. Any required placards installed or required by an alteration must be added to the Limitations Section of the Instructions for Continued Airworthiness to ensure that maintenance personnel will know if a required placard is missing in future inspections.
115. THRU 199. RESERVED
Par 108 Page 5
FIGURE 1-3. HYPOTHETICAL OF DETERMINING STATIC TEST LOADS
UTILITY CATEGORY AIRCRAFT (14 CFR PART 23) LOAD FACTORS Type of load Direction 1
Limit 2
X Safety 3
= Ultimate 4
X Special 5 Static = Test 6 Critical Static Test A.
Maneuvering Fwd
Down
Side
Up
Aft (None)
6.2g
(None)
-3.8g
1.0g
1.5
----------------
1.5
1.5 ----------------
9.30g
----------------
-5.7g
1. 5g ---------------
---------------
---------------
---------------
--------------- --------------
9.3g
--------------
-5.7g
1.5g
9.3g
5.7g B.
Gust (=30 FPS @ KVc)
*For locations aft of fuselage Sta. 73.85.
Fwd
Down
Down*
Side
Up
Aft (None)
6.0g
6.4g
1.6g
-2.8g
(None) ----------------
1.5
1.5
1.5
1.5
--------------- ----------------
9.0g
9.6g
2.4g
-4.2g
---------------- ---------------
---------------
---------------
---------------
---------------
--------------- --------------
9.0g
9.g
2.4g
-4.2g
--------------
*9.6g
2.4g C.
Ground Fwd
Down
6.6g
4.0g
1.5
1.5
9.9g
6.0g ---------------
---------------
9.9g
6.0g
9.9g Already Prescribed as Ultimate
9.0g
4.5g
(None)
D.
Ultimate Inertia Forces for Emergency Landing Condition (Section
23.561).
**For Separate cargo compartments.
Fwd
Fwd.**
Down
Side
Up
Aft
Already Prescribed as Ultimate
1.5g
-3.0g
(None) ---------------
---------------
---------------
---------------
---------------
--------------- --------------
--------------
--------------
1.5g
-3.0g
--------------
**4.5g Page 6 Par 114
FIGURE 1-3. HYPOTHETICAL OF DETERMINING STATIC TEST LOADS – CONTINUED Par 114 Page 7 (and 8) UTILITY CATEGORY AIRCRAFT (14 CFR PART 23) LOAD FACTORS Type of load Direction 1
Limit 2
X Safety 3
= Ultimate 4
X Special 5 Static = Test 6 Critical Static Test E.
Ultimate Inertia Forces for Emergency Landing Condition For Seat, Litter, & Berth Attachment to Aircraft Structure (Section 23.785).
Fwd
Down
Side
Up
Aft
Already Prescribed as Ultimate
9.0g
(None)
1. 5g
-3.0g
(None)
1. 33
---------------
1.33
1.33
---------------
12.0g
--------------
2.0g
-4.0g
--------------
12.0g * Asterisks denote special load conditions for the situation shown.
CHAPTER 2. COMMUNICATION, NAVIGATION, AND EMERGENCY
LOCATOR TRANSMITTER SYSTEM INSTALLATIONS
200. PURPOSE. This chapter describes installation considerations and requirements for basic standalone, installations of communication, navigation, and emergency locator transmitter (ELT) equipment.
NOTE: Stand-alone installations do not depend on other systems or complex interfaces to function.
201. HAZARDS AND WARNINGS.
a. When installing these systems follow the aircraft and equipment manufacturers’ instructions as appropriate. Practice a “clean as you go” philosophy. Ensure that equipment and systems function properly and perform their intended function(s).
b. Alterations of aircraft that are performed to accommodate the installation of radio equipment must be evaluated for their impact on aircraft design and operation. Refer to Advisory Circular (AC) 23.1309-1, Equipment, Systems, and Installations in Part 23 Airplanes, (as amended) for additional information concerning the evaluation for equipment, systems, and installations in Title 14 of the Code of Federal Regulations (14 CFR) part 23 airplanes.
c. Frequently an alteration to accommodate the installation of radio equipment will have little impact on the design or operation of an aircraft;
however, all potential elements of impact must be considered. One approach is to evaluate each element independently.
d. Consider the impact when weight and balance or structural load limits of an added system exceeds existing installations. Consider the impact when radio frequency such as electromagnetic interference (EMI), high in tensity radiated fields (HIRF), or lightning may negatively affect existing systems (e.g., accuracy of the magnetic compass).
e. When evaluating elements of impact consider the before and af ter states. No further analysis of weight and balance may be required if an object of similar size and weight was previously installed in a location. If mounting attach points were previously substantiated to support a specific load and the same load or less is being installed, the previous analysis may be referenced.
NOTE: Data that is referenced must be available and reviewed.
f. When structures must be fabricated or reinforced, the standard practices approved for repairs if applicable may be employed. AC 43.13-1 (as amended), Acceptable Methods, Techniques, and Practices—Aircraft Inspection and Repair, may provide structural design data for fabrication of mountings and attachments.
g. Ensure that the capacity of the aircraft’s charging system is not exceeded, including any required additional allowances.
h. Care should be taken to ensure that cables or wires will not interfere with the aircraft’s flight, engine, or propeller controls.
i. When removing older radios/wiring/power supplies and installing newer solid state components weigh the old equipment and perform a new weight and balance calculation. This is important since differences in the location and weight of equipment will shift the center of gravity.
j. Refer to AC 43.13-1 (as amended), chapter 10 and FAA-H-8083-1, Aircraft Weight and Balance Handbook, for additional information on determining of weight and balance.
Par 200 Page 9
202. CONSIDERATIONS WHEN INSTALL- ING AVIONICS EQUIPMENT. When installing radio equipment, use areas or locations designated by the airframe manufacturer and use factory supplied brackets or racks. Follow the aircraft manufacturer’s installation instructions. When this information is not available, use locations in the aircraft of known load carrying capabilities.
Baggage compartments and cabins or cockpit floors are good mounting platforms provided the floor attachments meet the strength requirements. Another method is to fabricate su pport racks, brackets, or shelves and attach them to the aircraft structure to provide a mounting that will withstand the inertia forces stipulated in chapter 1.
a. General Considerations. Ensure the following:
(1) There is appropriate air circulation to ensure proper cooling and dissipation of any heat generated or present. Consider the flammability characteristics of all associated elements.
(2) There are appropriate clearances to prevent mechanical damage to other parts of the aircraft or from other parts of the aircraft.
(3) There is protection provided to the component or article from any fluids or fumes that may be expected and that the component or article will not cause any fluids or fumes to be present that may result in damage to the aircraft or its occupants.
(4) That any interference, environmental or operational, to an aircraft or any system of the aircraft is identified and minimized as to not affect airworthiness of the aircraft.
(5) That flight characteristics of the aircraft are not altered unless appropriately identified and the changes are within the certified design limits.
b. Structural Consideration. Consider the following:
(1) Structural requirements of a mounting must be considered (see chapter 1).
FIGURE 2-1. FORCE DIAGRAM NORMAL-
UTILITY CATEGORY
3.0g (up)
1.5g (side)
9.0g (forward) 6.6g (down)
(2) Alterations that include making additional cutouts or enlargements of existing panel cutouts must be evaluated to maintain structural integrity. Some aircraft instrument panels are load bearing structures.
(3) Loads must be determined to be within the structural design limits of the supports.
(4) Instrument panels as well as other panels throughout the aircraft may be structural or nonstructural in design. Structural loads must be adequately transferred to primary airframe members.
(5) Methods and practices described elsewhere in this AC and in AC 43.13-1 (as amended) may be employed for the fabrication of attachments and structure.
Par 202 Page 10
FIGURE 2-2. TYPICAL FABRICATED PANEL MOUNTING
Machine screws and self-locking nuts Rear case support Rivets or Machine screws and self-locking nuts FIGURE 2-3. TYPICAL LAYOUTS
Typical layout older aircraft
Typical layout newer aircraft
(6) Existing structures may be reinforced or strengthened using methods described in AC 43.13-1 (as amended).
203. INSTRUMENT PANEL MOUNTING. This paragraph is supplemented by AC 43.13-1 (as amended), chapter 2, and is applicable to the installation of radio units in instrument panels.
a. Stationary Instrument Panels— Nonstructural and Structural. The stationary instrument panel in some aircraft is part of the primary structure. Prior to making any additional “cutouts” or enlargements of an existing “cutout,” determine if the panel is part of the primary structure. If the panel is structural, make additional “cutouts” or the enlargement of existing “cutouts” in accordance with the airc raft manufacturers’ instructions, or substantiate the structural integrity of the altered panel in a manner acceptable to the Administrator. Radius all corners and remove all burrs from “cutout” and drilled holes.
b. Added Equipment Stationary Instrument Panel. When radio equipment is to be installed in a stationary panel already supporting instruments, glove compartments, etc., determine the capability of the panel to support the total load.
c. Case Support. To minimize the load on a stationary instrument panel, whenever practicable, install a support between the rear (or side) surface of the radio case and a nearby structural member of the aircraft (Figure 2-2).
d. Added Equipment—Shock-Mounted Panels. When installing radio equipment designed for use in shock-mounted panels, total accumulated weight of equipment installed must not exceed the weight carrying capabilities of the shock mounts.
Determine that the structure to which the shock mounts are connected is satisfactory for supporting the added weight.
e. Existing Factory Fasteners. When possible, use existing plate nuts and machine screws provided by the aircraft manufacturer for attachment Par 202 Page 11
of the radio case or rack. If additional fastening is required, use machine screws and elastic stop nuts (preferably plate nuts).
f. Magnetic Direction Indicator. As a function of the radio installation, determine if it is necessary to swing the compass. Install a suitable placard which indicates the compass error with the radio(s) on and off. Maximum acceptable deviation in level flight is 10 degrees on any heading. The following is an example of a typical compass calibration card (refer to current edition of AC 43.13-1, chapter 12 , on how to swing a compass).
TABLE 2-1. TYPICAL COMPASS CALIBRATION CARD FOR N 30 60 E 120 150 Radio On Steer 4° 35° 63° 93° 123° 154° Radio Off Steer 358° 27° 58° 88° 118° 148°
FOR S 210 240 W 300 330 Radio On Steer 183° 214° 244° 274° 304° 337° Radio Off Steer 178° 208° 238° 268° 293° 327°
204. OTHER MOUNTING AREAS. The following are acceptable methods for installing radio equipment at other than instrument panel locations.
a. Shock-mounted Units.
(1) Wood or Composition Flooring.
Secure the shock-mounted base assembly (suitable to radio unit) directly to the floor using machine screws. Add a doubler to the bottom of the floor thereby sandwiching the composition floor between each shock-mount foot and the doubler. Subsequent removal and reinstallation of the shock-mount foot will be facilitated if plate nuts are secured to the doubler. Where practicable, use small retaining screws to keep the doubl er in position. Install a ground strap between the radio rack and metal structure of the aircraft.
Par 203 Page 12
FIGURE 2-4. TYPICAL SHOCK-MOUNTED BASE
Wood Flooring Machine Screw Shock Mount Doubler Plate Nut
(2) Metal Flooring. Secure the shockmounted base assembly directly to the floor using machine screws, washers, and self-locking nuts.
Floor area under and ar ound the radio mounting bases may require installation of doublers or other reinforcement to prevent flexing and cracking.
Installation of plate nuts on the floor or doubler will facilitate removal and in stallation of the shock mounts. Install a ground strap between the shock mount foot and the radio rack.
FIGURE 2-5. TYPICAL SHOCK-MOUNTED BASE
Shock Mount Metal Flooring Plate Nut Machine Screw
b. Rigid-Mounted Unit Base. Secure radio mounting base plate(s) to the floor (wood, composite, or metal) us ing machine screws as shown in Figure 2-6. Use a reinforcing plate or large area washers or equivalent under wood or composite flooring. When the mounting base is secured to wood or composite material, install a ground strap between the base and aircraft metal structure.
Par 204 Page 13
FIGURE 2-6. TYPICAL RIGID BASE PLATE MOUNT
Machine Screw Machine Screws and Self-Locking Nuts
205. FABRICATION OF SUPPORTING
BRACKETS FOR ATTACHMENT TO STRUCTURE OTHER THAN FLOORING.
a. Typical supporting brackets usually consist of a shelf or platform upon which the radio unit mounting base assembly can be installed in the same manner as described in applicable paragraph 203.
b. Fabricate bracket in accordance with good aircraft design, layout, assembly practices, and workmanship to obtain results compatible with the airframe structure. Generally, the thickness of bracket material will depend on the size or area of the platform and load it must sustain in accordance with provisions set forth in chapter 1.
c. Use a rivet size and pattern compatible with the aircraft structure to provide the strength needed to assure support of the loads imposed under all flight and landing conditions.
FIGURE 2-7. TYPICAL UNDERSEAT INSTALLATION
Unit attachment ear Plywood floor AN 970 flat washer Machine screw and elastic stop nut 1” clearance with seat occupied and subject to maximum seat spring deflection (6.6 X 170 pounds) downward (load).
Par 205 Page 14
NOTE: To increase the strength of floor attachment points, metal reinforcement may be installed as needed.
206. REINFORCEMENT OF SUPPORTING STRUCTURE.
a. Attach equipment to the supporting structure of the aircraft so that its supported load will be transmitted to aircraft structural members. If direct attachment to the existing structure (bulkheads, horizontal stringers, etc.) is not feasible, add the necessary stringers, doublers, bulkhead flange reinforcements, etc., to provide adequate support and assure load transfer to the primary structure. When attaching to the existing structure ensure that the attachment does not weaken the structure. Alteration to primary structure may require approved engineering data.
b. Placard. Fasten onto the shelf or bracket a permanent placard (as the example below) stating the design load which the installed structure is determined capable of supporting.
“Shelf load not to exceed __________lbs.”
Par 205 Page 15
FIGURE 2-8. TYPICAL REMOTE UNIT MOUNTING BASE-VERTICAL OR HORIZONTAL
OTHER THAN STRUCTURE TO FLOOR
Par 206 Page 16