AC 29-2, CHG 1 11/19/84 * (11) For vertical stablizers that house the tail rotor output gearbox, such as the Hiller Model FH1100, the tail surface air loads will add to or subtract from the tail rotor thrust according to the flight condition under consideration NOTE: For one example: At stablized yaw to the right (left pedal depressed to limit) (§ 29.351(b) (2)), the tail rotor thrust moment should equal the restoring moment of the tail boom, vertical stabilizer and main rotor torque. As stated by § 29.351(b)(3), the tail rotor thrust moment then i9 added to the vertical stabilizer restoring moment. The addition of tail rotor thrust (§ 29.351(b) (3)) and vertical stabilizer load is generally one of the critical design conditions for the fuselage/tail boom.
(i1i) For vertical stablizers or fins that have an offset incidence angie with respect to the helicopter axis, the vertical fin moment is added, or subtracted as applicable, to the tail rotor thrust moment. The condition stated in § 29.351(b)(1) may result in adding the fin load to the tail rotor thrust.
(Iv) Low airspeed maneuvers, such as sideward, rearward, and hover turns over a spot, typically impose insignificant aerodynamic loads on the fugelage and/or tail boom. The aerodynamic loads at VH or VNE, whichever is required, are generally the significant aerodynamic design loads.
A rational assessment of the various yaw conditions may be used to reduce the load deviation and analysis to the critical rotorcraft design conditions.
(vi) The helicopter structure shall be analyzed or tested for loads derived from the critical design conditions.
(vi1) A simple structural design envelope may be derived from these design data. If the right or left yaw limits are not very different, common, conservative design limits may be used. A sample yaw/forward speed diagram, as derived from design analysis of the characteristics of a hypothetical helicopter, is presented in Figure 140-l. A table of values would also suffice. This figure reflects characteristics which include a 90° yaw when the directional control inputs are applied at low airspeeds (up to 30 knots presumably the maximum are applied at VH, with a straight line variation from 30 knot forward apeed to • sideward flight speed of which this aircraft is capable) and 10° yaw when they Chap 2 236 Par 140
90° -90° Yaw Degrees 10° Max.
30 knot sideward Flight Airspeed FIGURE 140-1 * (vii1) During flight test evaluations, yaw angles have been measured using a yaw angle probe (swiveling vane type) on a nose boom. Both a visual readout for the pilot and a record, such as an oscillograph trace, have been used. This test may be conducted in the flight test program or in the flight load survey program. This record should confirm the yaw angle used in design as conservative with respeot to operational and actual flight characteristics. This test is not a requirement however.
Chap 2 Par 140 237
AC 29-2, CHG 1 11/19/84
141. § 29.361 (through Amendment 29-19) ENGINE TORQUE.
a. Explanation.
(1) The rotorcraft should be designed for limit engine to que values, as prescribed by the rule, to account for maximum engine torque, including transients and torsional oscillations. The rule recognized that reciprocating (piston) engines generate higher torque oscillations than turbine engines.
(2) A factor of 1.25 applies to maximum continuous power for turbine engines.
(3) Torque factors are also specified for reciprocating engines having two or more cylinders § 29.361a.2. The appropriate torque factor applies to takeoff power torque as well as maximum continuous power and other power conditions.
(4) Paragraph 206 of this document concerns $ 29.549(e) that contains standards associated with 2 1/2-minute power rating.
D• Procedures•
(1) The engine torque associated with the maximum continuous power condition must be multiplied by the appropriate torque factor to obtain the engine torque value used for structural substantiation purposes of the rotorcraft.
(2) The torque values associated with the minimum power-on rpm limit should be used. Maximum power-on speed limit will result in a lower torque value when calculating torque from design horsepower values. However, due to piston engine power output characteristics, an engine may produce a higher torque at higher engine speeds contrary to the previous statement. The torque factor should account for this characteristic.
142.-151. RESERVED.
Chap 2 238 (thru 248) Par 141
SECTION 7. STRENGTH REQUIREMENTS - GENERAL * 121. § 29.301 (through Amendment 29-19) LOADS.
a. Explanation,
(1) The rule is a general statement concerning limit and ultimate loads, and the application of these loads to the rotorcraft.
(2) Ultimate loads are limit loads multiplied by the prescribed factors of safety.
(3) The specified loads must be distributed appropriately or conservatively and signficant changes in distribution of the loads, as a result of deflection, must be taken into account.
b. Procedures. The design criteria report and/or design loads report must contain data that comply with the rule.
122. § 29.303 (through Amendment 29-19) FACTOR OF SAFETY.
a• Explanation.
(1) Unless otherwise provided by FAR Part 29, a factor of safety of 1.5 is required and is applied as stated in the rule. This safety margin will assure that the design strength of the rotorcraft is greater than the design loads contained in FAR Part 29.
(2) Other rules, $$ 29.561 (b)(3) and 29.787(c), specify use of defined ultimate inertia forces for protection of occupants.
b. Procedures.
(1) The design criteria report and/or design loads report must contain data that include the appropriate factor of safety.
(2) The factor of safety multiplies the limit external and inertia loads. The rule does allow the application of this factor to the resulting 'limit internal" stresses if it is more conservative.
123. § 29.305 (through Amendment 29-19) STRENGTH AND DEFORMATION.
a. Explanation.
(1) This general rule defines, in relative terms, allowable deformation for limit and ultimate loads.
(2) The structure must support, in a static test, ultimate loads for 3 seconds without failure or dynamic tests simulating actual load application may * be used.
Chap 2 Par 121 197
AC 29-2, CHG 1 11/19/84
(3) Section 29.307 concerns proof of the structure and requires certain specified tests. This rule also allows substantiation by struotural analysis.
See paragraph 124 of this advisory circular.
b. Procedures. Any test results, static or dynamic, must satisfy the limitations or acceptance criteria contained in the rule.
(1) Any test proposals submitted for approval that are used to demonstrate compliance with sections of FAR Part 29 must contain the criteria stated in the rule.
(11) Any test results reports shall contain data and information showing the test results comply with the standard.
Chap 2 198 Par 123
124. § 29.307 (through Amendment 29-19) PROOF OF STRUCTURE.
a• Explanation.
(1) The rule requires compliance for each critical loading condition.
Certain tests must be conducted as specified. Additional tests for new or unusual design features may be required as noted in subparagraph (b) (6).
(2) Structural analysis may be used only if the structure conforms to those for which experience has shown this method to be reliable.
(3) Fatigue substantiation requirements are explained further in paragraph 230, § 29.571 of this advisory ciroular.
b. Procedures.
(1) The design criteria and/or design loads report should contain typical or representative loading conditions from which the oritical loading conditions will be selected for analytical substantiation in struotural (static and fatigue) reports and dynamics (vibration and stability) reports and fatigue, statio, dynamio, or operational test reports.
(2) Whenever tests are used or required, a test proposal or plan must be approved prior to the tests. The test article must have received conformity inspections and must have been acoepted by the FAA for the test. Test fixtures and instrumentation must also be acceptable to the FAA (using DER's as appropriate) prior to start of the test. The quality control office of the applicant or other qualified pesonnel may be authorized to conduct inspections of the test fixtures and instrumentation rather than the FAA or DER performing this task. The test proposal may be used to define and to authorize the means to accomplish inspection of the test fixtures and instrumentation. Unnecessary drawings, such as test fixture details, or layering of approvals is not intended or envisaged by this policy. Drawings, sketches or photographs have been used by the FAA to control and to assure correct location, direction, and magnitude of loads and other oritical test parameters.
(3) Structural analysis has been accepted for rotorcraft in place of static tests. Generally the helicopter airframe should have frequency placements remote to predominate rotor excitation sources, including rotor harmonics, to avoid undesirable and possibly excessive vibration and potentially high operating stress levels due to this vibration. During the flight load measurement program conducted under § 29.571, critical loaded areas or critical joints may be instrumented with strain gages or other stress strain measuring devices. This actual flight data may be compared to the analytical data to verify accuracy.
Chap 2 Par 124 199
AC 29-2, CHG 1 11/19/84
(4) Subparagraph (b) of the rule specifies certain tests. Test proposals must be approved prior to conducting official FAA tests. Other paragraphs in this advisory circular pertain to those tests.
125. § 29.309 (through Amendment 29-19) DESIGN LIMITATIONS.
a. Explanation.
(1) The rule requires an orderly selection and presentation of the basic structural design limitations of the rotorcraft. The applicant must establish these structural limitations to facilitate design of the rotorcraft.
(2) Refer to the rule for the specifio requirements.
b. Procedures.
(1) The design criteria and/or design load report should contain the design limits specified.
(2) These items are structural design limits. Other requirements may result in narrowing the ranges of type design limits or in reducing limits. It is not necessary to revise structural design criteria limits to agree with more conservative operational limits established during the certification program. The operational limits may be subsequently expanded by additional flight tests to agree with design limits.
126.-135. RESERVED.
Chap 2 200 (thru 230) Par 124
AC 43.13-1A CHG 1 Page 165 1975 Chapter 10. HYDRAULIC AND PNEUMATIC SYSTEMS Section 1. HYDRAULIC SYSTEMS
392. GENERAL. Maintain, service, and adjust connection fittings: AN-818 nut and AN-819 airplane hydraulic systems in accordance with sleeve.
manufacturers' maintenance manuals and pertinent component maintenance manuals. Certain Minimum bend radil * general principles of maintenance and repair for tightening tube nuts Wrench torque range measured at Inside of bend.
which apply are outlined below. Tube O.D. (Inch pounds) Dimenaton in inches. * (inches)
393. HYDRAULIC LINES AND FITTINGS. Carefully Alum. alloy 1100-H14, Alum. alloy 1100-H114, inspect all lines and fittings at regular intervals 5052-0 Steel 5052-0 Steel to insure airworthiness. Investigate any evidence of fluid loss or leaks. Check metal lines for 30-70 leaks, loose anchorages, scratches, kinks, or other ¾а 40-65 60-80 50-90 70-120 21/32 damage. Inspect fittings and connections for 75-125 00-150 1⅜ leakage, looseness, cracks, burrs, or other damage. 150-250 155-250 15¾8 1¾в Replace or repair defective elements. 200-350 300-400 1¼ 1¾ 300-500 430-575 1⅓ 218
a. Replacement of Metal Lines. When inspec- 500-700 550-750 1¾ 2% tion shows a line to be damaged or defective, 1 600-900 3 replace the entire line or if the damaged section 1¼ 600-900 9% is localized, a repair section may be inserted. 14½ 5¼ In replacing lines, always use tubing of the same 1¾ 2 size and material as the original line. Use the old tubing as a template in bending the new line, FIGURE 10.1.-Tube data.
a template can be made from soft iron wire.
Soft aluminum tubing (1100, 3003, or 5052) under ¼-inch outside diameter may be bent by hand. For all other tubing use an acceptable hand or power tube bending tool. Bend tubing carefully to avoid excessive flattening, kinking, or wrinkling. Minimum bend radii values are shown in figure 10.1. A small amount of flattening in bends is acceptable but do not exceed an amount such that the small diameter of the flattened portion is less than 75 percent of the original outside diameter. When installing the replacement tubing, line it up correctly with the mating part so that it is not forced into line by means of the coupling nuts.
b. Tube Connections. Many tubing connections are made using flured tube ends, and standard In forming fares, cut the tube ends square, file smooth, remove all burrs and sharp edges, and thoroughly clean. The tubing is then flared using the correct 37° aviation flare forming tool for the size of tubing and type of fitting. A double flare is used on soft aluminum tubing ⅜-inch outside diameter and under, and a single flare on all other tubing. In making the connections, use hydraulic fluid as a lubricant and then tighten. Overtightening will damage the tube or fitting, which may cause a failure; undertightening may cause leakage which could result in a system failure.
Mistaken use of 45° automotive flare forming tools will result in improper tubing flare shape and angle causing misfit, stress and strain, and probable system failure.
Chop 10 Par 392
c. Repair of Metal Tube Lines. Minor dents and scratches in tubing may be repaired. Scratches or nicks no deeper than 10 percent of the wall thickness in aluminum alloy tubing, that are not in the heel of a bend, may be repaired by burnishing with hand tools. Replace lines with severe die marks, seams, or splits in the tube.
Any crack or deformity in a flare is also unacceptable and cause for rejection. A dent less than 20 percent of the tube diameter is not objectionable unless it is in the heel of a bend.
Dents may be removed by drawing a bullet of proper size through the tube by means of a length of cable. A severely damaged line should be replaced; however, it may be repaired by cutting out the damaged section and inserting a tube section of the same size and material. Flare both ends of the undamaged and replacement tube sections and make the connection by using standard unions, sleeves, and tube nuts. If the damaged portion is short enough, omit the insert tube and repair by using one union and two sets of connection fittings.
d. Replacement of Flexible Lines. When replacement of a flexible line is necessary, use the same type, size, and length of hose as the. line to be replaced. If the replacement of a hose with swaged-end-type fittings is necessary, obtain a new hose assembly of the correct size and composition. Certain synthetic oils require a specially compounded synthetic rubber hose which is compatible. Refer to the aircraft manufacturer's service information for correct part number for replacement hose. If the fittings on each and are of the collet type or sleeve type in replacement may be fabricated as shown figure 10.2. Typical aircraft hose specifications and their uses are shown in figure 10.3. Install hose assemblies without twisting. (See figure
10.4.) Never stretch a hose tight between two fittings as this will result in overstressing and eventual failure. The length of hose should be sufficient to provide about 5 percent to 8 percent slack. Avoid tight bends in flex lines as they may result in failure. Never exceed the minimum bend radii as indicated in figure 10.5.
Teflon hose is used in many aircraft systems because of its superior qualities for certain applications. Teflon is compounded from tetrafluoroethylene resin which is unaffected by fluids Par 393 AC 43.13-1A CHG 1 1975 normally used in aircraft. It has an operating range of -65° F. to 450° F. For these reasons, Teflon is used in hydraulic and engine lubricating systems where temperatures and pressures preclude the use of rubber hose. Although Teflon hose has excellent performance qualities, it also has peculiar characteristics that require extra care in handling. It tends to assume a permanent set when exposed to high pressure or temperature. Do not attempt to straighten a hose that has been in service. Any excessive bending or twisting will cause kinking or weakening of the tubing wall. Replace any hose that shows signs of leakage, abrasion, or kinking.
Any hose suspected of kinking may be checked with a steel ball of proper size. Figure 10,6 shows hose and ball sizes. The ball will not pass through if the hose is distorted beyond limits.
If the hose fittings are of the reusable type, a replacement hose may be fabricated as described in figure 10.2. When a hose assembly is removed the ends should be tied as shown in figure 10.7, so that its preformed shape will be maintained. Refer to figure 10.9 for minimum bend radii of Teflon hose.
All flexible hose installations should be supported at least every 24 inches. Closer supports are preferred. They should be carefully routed and securely clamped to avoid abrasion, kinking, or excessive flexing. Excessive flexing may cause weakening of the hose or loosening at the fittings.
e. O-Ring Seals. A thorough understanding of O-ring seal applications is necessary to determine when replacement must be made. The simplest application is where the O-ring merely serves as a gasket when it is compressed within a recessed area by applying pressure with a packing nut or screw cap.
Leakage is not normally acceptable in this type of installation. In other installations the O- ring seals depend primarily upon their resiliency to accomplish their sealing uction. When moving parts are involved, minor seepage may be normal and acceptable. A moist surface found on moving parts of hydraulic units is an indication the seal is being properly lubricated.
In pneumatic systems, seal lubrication is provided by the installation of a grease-impreg- Chap 10
AC 43.13-1А Page 195 1972
PRESSURE -
SENSITIVE TAPE XYZ15
SLEEVE MARKER
TIED IN PLACE XYZ 15 FIGURE 11.19.-Identification of wire bundles and harnesses.
467.-477. RESERVED.
Chap 11 Par 464
AC 43.13-1A Chg 3 Page 196 1988 Section 5. CONNECTORS
478. GENERAL PURPOSE CONNECTORS. Connectors (plugs and receptacles) are used to facilitate maintenance when frequent disconnection is required. Since the wires are soldered to the connec tor inserts, the joints should be individually installed and the wire bundle firmly supported to avoid damage by vibration. Connectors have been particularly vulnerable to corrosion in the past, due to condensation within the shell. Special connectors with waterproof features have been developed Class C-A pressurized connector with inserts that are not removable. Looks like a Class A connector but the inside sealing arrangement is sometimes different and is used on walls of bulkheads of pressurized equipment.
Class D-Moisture and vibration resisting connector which has a sealing grommet in the back shell. Wires are threaded through tight fitting holes in the grommet, thereby sealing against moisture.
and may be used to replace nonwaterproof type Class K-A fireproof connector used in areas plugs in areas where moisture causes a connector where it is vital that the electric current is not inproblem. Use a replacement connector of the same terrupted, even though connector may be exposed basic type and design as the connector it replaces. to continuous open flame. Wires are crimped to the Connectors that are susceptible to corrosion dilhi- pin or socket contacts and the shells are made of culties may be treated with a chemically inert wa- steel. This class of connectors is normally longer terproof jelly. When replacing connector assem- than the other classes of connectors.
blies, use the socket-type insert on that half which is live or "hot" after the connector is disconnected * NOTE: Inspect connectors for loose soldered connec to prevent unintentional grounding. tions, proper insulation of metallic parts, and fraying of wires in the plug and receptacle inserts.
479. TYPES OF CONNECTORS. Connectors are identified by AN numbers and are divided into types and classes with manufacturer's variations in each type and class. The manufacturer's variations are differences in appearance and in the method of meeting the specification; however, they do not preclude mating plugs and receptacles of different manufacturers. There are six basic types of AN connectors used in aircraft which are further broken down into five classes as indicated in figures 11.20 and 11.21. Each class of connector has slightly different construction characteristics which are noted as follows: Classes A, B, C, and D are made of aluminum; Class K is made of steel.
Class A-Solid one-piece back shell general purpose connector.
Class B-Connector back shell separates into two parts lengthwise. Use primarily where it is important that the soldered connectors are readily accessible. The back shell is held together by a threaded ring or by screws.
480. ARMY/NAVY (AN) CONNECTOR IDENTIFI- CATION. Code letters and numbers are marked on the coupling ring or shell to identify the connector.
This code provides all the information necessary to obtain the correct replacement for a defective or damaged part. To facilitate ready identification the code found on a typical connector (as shown in figure 11.22) is explained as follows:
a. The letters AN indicate the connector was made to a government standard.
b. Type 3106 indicates this is a straight plug.
c. Letter A indicates this is a general purpose connector with a solid back shell.
d. Number 18 indicates the size of the coupling. This size is determined in 1/16-inch increments. Therefore, the size of the plug in the example is 1 1/8 inch.
Chap 11 Par 478
AC 43.13-1A Chg 3 Page 153 1988 Section 3. MISCELLANEOUS EQUIPMENT
360. PARACHUTES. With reasonable care, parachutes normally last at least 5 years. They should not be carelessly tossed about, left in airplanes so that they may become wet, or left in open places where they may be tampered with. They should not be placed where they may fall on oily floors or be subject to acid fumes from adjacent battery chargers. When repacking is scheduled, a careful inspection of the parachute should be made by a qualified parachute technician (rigger). If repairs or replacements of parts are necessary to maintain the airworthiness of the parachute assembly, such work must be done by the original parachute manufacturer or by a qualified parachute rigger, certificated in accordance with FAR Part 65, or by an appropriately rated parachute loft certificated in accordance with FAR Part 149.
Fraying of belts is an indication of wear, and such belt are likely to be unairworthy because they can no longer hold the minimum required tensile load.* Difference of opinion as to the airworthiness of a belt can be settled by testing a questionable belt to demonstrate that it will support the required load.
Airworthy one-person type-certificated belts should be able to withstand a tensile load of 525 pounds, and TSO belts withstand the rated tensile load indicated on the belt label. Most one-person TSO belts are rated for 1,500 pounds. For twoperson belts, double the loads. Since type-certificated belts will not afford the crash protection provided by a TSO or military belt, such type-certificated belts are not to be repaired nor should their buckles or end fittings be reused on safety belts. If replacement of webbing or hardware of TSO or military belt is attempted, use parts of identical design *361. SAFETY BELTS. The FARS require that and material. Make the stitch pattern identical to when safety belts are to be replaced in aircraft the original and the number of stitches per inch manufactured after July 1, 1951, such belts must equal to the number used in the original belt. There conform to standards established by the FAA.* is no objection to having a greater total length of These standards are contained in Technical Stand- stitching, provided one line of stitches is not placed ard Order TSO-C22. Safety belts eligible for instal- over another line. Space lines of stitching at least lation in aircraft may be identified by the marking 3/16-inch apart. Keep a record, preferably in the TSO-C22 on the belt or by a military designation logbook, stating the extent to which the belt was number since military belts comply with the repaired and the date. Retain the original identifica- * strength requirements of the TSO. Each safety belt tion marking on the belt, conforming either to that must be equipped with an approved metal to metal required by TSO-C22 to a deviation from this latching device. Airworthy type-certificated safety* marking, or to the military designation. Operators belts currently in aircraft may be removed for of a fleet of airplanes should follow the above sugcleaning and reinstalled. However, when a type- gestions, but keeping a record of renovations in a certificated safety belt is found unairworthy, re- logbook is impractical, since the belts are never placem it with a TSO-C22 or a new belt is pre- associated with any one particular aircraft for ferre:: any length of time. Therefore, in addition to * a. The webbing of safety belts, even when retaining the original identification label and mildew-proofed, is subject to deterioration due to attaching it to the renovated belt, use constant use, cleaning, and the effects of aging. some additional simple marking to indicate Chap a Par 360