Rev. 1977 AC 43.13-2A Section 2. CONVERSION AND INSTALLATION
66. HUB-AXLE CLEARANCE. The pedestal hub should fit the axle to provide a clearance of .005" minimum to .020" maximum. Hubs may be bushed to adjust for axle size, using any ferrous or nonferrous metal, hard rubber, or fiber. If rubber or fiber bushings are used, use retaining washers of sufficient size on each side to retain the hub if the bushing should slip or tail. (See fig. 5.2.)
67. CRUST-CUTTER CABLES. Crust-cutter cables are optional. However, when operating in severe crust conditions, it is advisable to have this cable installed to prevent the shock cord from being cut if the nose of the ski breaks through the crust while taxiing.
68. CABLE AND SHOCK CORD ATTACHMENT AND ATTACHMENT FITTINGS. Service reports indicate that failure of the ski itself is not a predominant factor in ski failures. Rigging (improper tension and terminal attachments) and cast-type pedestal material failures are predominant. Usually, failures of the safety cable and shock cord attachment fittings occur at the ski end and not at the fuselage end.
Do not attach tension cords and safety cables at the same point on the fuselage fittings. Provide separate means of attaching cables and shock cords at the forward and aft ends of the skis.
Usually, approved skis are supplied with cables, shock cord, and fittings; however, the following specifications may be used for their fabrication and installations:
retaining washers bushings pedestal hub axle FIoURE 5.2.-Typical hub installation.
Chap 5 35
AC 43.13-2A Rev. 1977 Minimum Cable and Shock Cord Sizes Ski Single Double Limit Single Double Crust- Crust- Single Double Load Safety Safety Cutting Cutting Shock Shock Rating Cable Cable Cable Cable Cord Cord 1500-3000 1/8" 1/8" 1/8' 1/8"' 1/2" 1/2" 3000-5000 1/8'' 1/8" 1/2" 5000-7000 5/32' 5/32'1 5/32" 3/4"' 3/4" 7000-9000 3/16" 5/32" 3/4"
a. Cables. Make the check cable, safety cable, and crust-cutting cable ends by the splice, swage, or nicopress methods; or if adjustable lengths are desired, use cable clamps. Use standard aircraft hardware only. (Hardware used to attach cables must be compatible with cable size.)
b. Shock cord ends may be fabricated by any of the following methods:
(1) Make a wrapped splice using a proper size rope thimble and No. 9 cotton cord or .035" (minimum) safety wire. Attach with clevis or spring steel snap fastener. (Do not use cast iron snaps.)
(2) Use approved spring-type shock cord end fasteners.
c. Fitting Specifications (see figure 5.3) and Installation:
(1) Fittings fabricated for 1/8-inch cable or 1/2-inch shock cord shall be at least .065" 1025 steel or its equivalent.
(2) Fittings fabricated for 5/32-inch cable or 3/4-inch shock cord shall be at least .080" 1025 steel or its equivalent.
FIGURE 5.3.-Typical fuselage fitting.
(3) An improperly installed fitting may impose excessive eccentric loads on the fitting and attach bolts and result in failure of the fitting or bolts.
69. PROVISIONS FOR INSPECTION. Aircraft using fabric-covered landing gear may have the lower 4 inches of fabric removed to facilitate inspection of the axle attachment area. (See fig. 5.1.)
70. [RESERVED] 36 Chap 5
Rev. 1977 AC 43.13-2A Section 3. RIGGING OF SKIS
71. LOCATION OF ATTACH FITTINGS ON FUSE- zero to 5-degree ski incidence angle (reference LAGE OR LANDING GEAR. Locate fittings so the figs. 5.4 and 5.6).
shock cord and cable angles are not less than b. Adjust length of safety cable to provide 20° when measured in the vertical plane with -20 to - 35-degree ski incidence angle (reference figs. 5.5 and 5.6).
the shock absorber in the fully extended position (see angle B, figs. 5.4 and 5.5). 73. TENSION REQUIRED IN MAIN SKI SHOCK CORDS. Apply sufficient shock cord tension to NoTE: Do not attach fittings to wing-brace struts, fore end of the skis to prevent flutter at various except by special approval (manufacturer or FAA).
72. MAIN SKI INCIDENCE ANGLES. (Aircraft leveled and shock absorbers fully extended.)
a. Adjust length of check cable to provide a airspeeds and attitudes. Because of the various angles used in attaching shock cord to the skis, shock cord tension cannot be specified. In most installations the downward force applied at the fore end of the ski, sufficient to cause the check FIGURE 5.4.-Main ski at maximum positive incidence (check cable tight).
Chap 5
AC 43.13-2A Rev. 1977 FIGURE 5.5.--Main ski at maximum negative incidence (safety cable tight).
cable to slacken, should be approximately as b. Where it is possible for the nose ski rigging listed below: to contact the propeller tips due to vibration, install a ¼-inch shock cord to hold the rigging Ski Limit Doronroard out of the propeller arc.
Load Force Rating (pounds) 75. TAIL SKI INSTALLATION.
a. Use tail skis that have been approved on 1500-3000 20-10 airplanes of approximately the same weight 3000-5000 40-60 (within 10 percent) or select as outlined in sec- 5000-7000 60-120 7000-9000 120-200
74. NOSE SKI INSTALLATION. The nose ski is installed in the same manner as the main skis (see fig. 57) except:
a. Adjust length of safety cable to provide
- 5- to - 15-degree ski incidence. FIGURE 5.6.-Main ski incidence angles.
38 Chap 5
Rev. 1977 tion 1. Depending upon the type of ski selected, the tail wheel may or may not have to be removed.
b. Adjust the length of the limiting cable (ref. fig. 5.8) to allow the ski to turn approximately 35 degrees either side of the straight- AC 43.13-2A forward position with the weight of the airplane resting on the ski.
c. The shock cord (ref. fig. 5.8) must be of a length that will hold the ski in the straightforward position during flight.
FIGUBE 57.-Typical nose ski installation.
Chap 5 39
AC 43.13-2A Rev. 1977 horiz.
ref.
LIMITING - SHOCK
CABLE CABLE FIGURE 5.8 Typical tail ski installation.
76.-78. [RESERVED] Chap 5 40
AC 43.13-2A Rev. 1977 Section 4. OPERATION
79. PERFORMANCE INFORMATION. The following FAA policies concern performance data and operational check flights for ski installations.
a. For aircraft over 6,000 pounds maximum certificated weight, state the following or similar information in the performance information section of the Airplane Flight Manual and obtain FAA approval.
(1) Takeoff. Under the most favorable conditions of smooth packed snow at temperatures approximating 32° F, the skiplane takeoff distance is approximately 10 percent greater than that shown for the landplane.
NoTE: In estimating takeoff distances for other conditions, caution should be exercised as lower temperatures or other snow conditions will usually increase these distances.
(2) Landing. Under the most favorable conditions of smooth packed snow at temperatures approximately 32° F, the skiplane landing distance is approximately 20 percent greater than that shown for the landplane.
NorE: In estimating landing distances for other conditions, caution should be exercised as other temperatures or other snow conditions may either decrease or increase these distances.
(3) Climb Performance. In cases where the landing gear is fixed (both landplane and skiplane), where climb requirements are not critical, and the climb reduction is small (30 to 50 feet per minute), the FAA will accept a statement of the approximate reduction in climb performance placed in the performance information section of the Airplane Flight Manual. For larger variations in climb performance, or where the minimum requirements are critical, or where the landing gear of the landplane was retractable, appropriate climb data should be obtained to determine the changes, and new curves, tables, or a note should be incorporated in the Airplane Flight Manual.
b. For aircraft of 6,000 pounds or less maximum certificated weight, make the information in 79a available to the pilot in the form of placards, markings, manuals, or any combination thereof.
80. FLIGHT AND HANDLING OPERATIONAL CHECKS. Accomplish an operational check which includes more than one landing to determine the ground-handling characteristics as well as takeoff and landing characteristics. Take note of ski angles during tail high and tail low landings to avoid having the ski dig in or fail from localized stress. Determine there is sufficient ground control to satisfactorily complete a landing run with a turnoff at slow speed in cases where brakes are not provided. In flight, the ski should ride steady with no unusual drag and produce no unsatisfactory flight characteristics.
Enter a notation of these checks in the aircraft
81. INTERCHANGING OF SKIS AND WHEELS After the initial installation, removing the skis and reinstalling the wheels or vice versa may be considered a preventive maintenance operation when no weight-and-balance computation is in-
82.-85. [RESERVED] 41 Chap 5
Rev. 1977 AC 43.13-2A Chapter 6. OXYGEN SYSTEM INSTALLATIONS IN NONPRESSURIZED AIRCRAFT
86. SYSTEM REQUIREMENTS. Install oxygen cylinders conforming to Interstate Commerce Commission requirements for gas cylinders which carry the ICC 3A, SAA, or 3HT designation followed by the service pressure metal-stamped on the cylinder. The 3HT designated cylinders must not be used for portable oxygen equipment.
a. Tubing.
(1) In systems having low pressure (400
p.s.i.), use seamless aluminum alloy or equivalent having an outside diameter of 5/16 inch and a wall thickness of 035". Double flare the ends to attach to fittings.
(2) In high-pressure systems (1800 p.s.i.), use 3/16 inch O.D., .035" wall thickness, seamless copper alloy tubing meeting Specification WW- T-779a type N, or stainless steel between the filler valve and the pressure-reducing valve. Silver-solder cone nipples to the ends of the tubing to attach the fittings in accordance with Specification MIL-B-7883.
(3) Use 5/16-inch O.D. aluminum alloy tubing after the pressure-reducer (low-pressure
(4) Use flexible connections specifically designed for oxygen between all points having relative or differential motion.
b. Valves. A slow opening valve is used as a cylinder shutoff valve, or system shutoff valve.
Rapid opening and the subsequent sudden and fast discharge of oxygen into the system can cause dangerous heating which could result in fire or explosion of combustibles within the system.
c. Regulators. The cylinder or system pressure is reduced to the individual cabin outlets by means of a pressure-reducing regulator which can be manually or automatically controlled.
d. Types of Regulators. The four basic types of oxygen systems, classified according to the type of regulator employed, are:
(1) Demand type.
(2) Diluter-demand type.
(3) Pressure-demand type.
(4) Continuous-flow type.
e. Flow Indicators.
(1) A pith-ball flow indicator, vane, wheel anemometer, or lateral pressure indicator which fluctuates with changes in flow or any other satisfactory flow indicator may be used in a continuous flow-type system.
(2) An Air Force-Navy flow indicator or equivalent may be used in a diluter-demand type system. Each flow indicator should give positive indication when oxygen flow is occurring.
f. Relief Valve.
(1) A relief valve is installed in low-pressure oxygen systems to safely relieve excessive pressure, such as caused by overcharging.
(2) A relief valve is installed in highpressure oxygen systems to safely relieve excessive pressure, such as caused by heating.
g. Gauge. Provide a pressure gauge to show the amount of oxygen in the cylinder.
h. Masks. Only masks designed for the particular system should be used.
87. INSTALLATION.
Oxygen systems present a hazard. Therefore, follow the precautions and practices listed below:
a. Remove oil, grease (including lip salves, hair oil, etc.), and dirt from hands, clothing, and tools before working with oxygen equipment.
b. Prior to cutting the upholstery, check the intended route of the system.
Make sure that all system components are kept completely free of oil or grease during installation and locate components so they will not contact or become contaminated by oil or hydraulic lines.
c. Keep open ends of cleaned and dried tubing capped or plugged at all times, except during attachment or detachment of parts. Do not use tape, rags, or paper.
AC 43.13-2A
d. Clean all lines and fittings which have not been cleaned and sealed by one of the following methods:
(1) A vapor-degreasing method with stabilized trichlorethylene conforming to Specification MIL-T-7003 or carbon tetrachloride. Blow tubing clean and dry with a stream of clean, dried, water-pumped air, or dry nitrogen (water-vapor content of less than 0.005 milligrams per liter of gas at 70° F and 760 millimeters of mercury pressure).
(2) Flush with naptha conforming to Specification TT-N-95; blow clean and dry of all solvent with water-pumped air; flush with antiicing fluid conforming to Specification MIL- F5566 or anhydrous ethyl alcohol; rinse thoroughly with fresh water; and dry thoroughly with a stream of clean, dried, water-pumped air, or by heating at a temperature of 250° to 300° F for one-half hour.
(3) Flush with hot inhibited alkaline cleaner until free from oil and grease; rinse thoroughly with fresh water; and dry thoroughly with a stream of clean, dried, water-pumped air, or by heating at a temperature of 250° to 300° F for one-half hour.
e. Install lines, fittings, and equipment above and at least 6 inches away from fuel, oil, and hydraulic systems. Use deflector plates where necessary to keep hydraulic fluids away from the lines, fittings, and equipment.
f. Allow at least a 2-inch clearance between the plumbing and any flexible control cable or other flexible moving parts of the aircraft. Provide at least ½-inch clearance between the plumbing and any rigid control tubes or other rigid moving parts of the aircraft.
g. Allow a 6-inch separation between the plumbing and the flight and engine control cables, and electrical lines When electrical conduit is used, this separation between the plumbing and conduit may be reduced to 2 inches.
h. Route the oxygen system tubing, fittings, and equipment away from hot ducts and equipment. Insulate or provide space between these items to prevent heating the oxygen system.
Rev. 1977
i. Mount all plumbing in a manner which prevents vibration and chafing. Support 3/16- inch O.D. copper line each 24 inches and 3/16- inch O.D. aluminum each 36 inches with cushioned loop-type line support clamps (AN-
742) or equivalent.
¡. Locate the oxygen supply valve (control valve) so as to allow its operation by the pilot during flight. The cylinder shutoff valve may be used as the supply control valve, if it is operable from the pilot's seat. Manifold plug-in type outlets, which are incorporated in automatic systems, may be considered as oxygen supply valves since the pilot can control the flow of oxygen by engaging and disengaging the plug-in type oxygen mask.
NoTE: Locate the oxygen shutoff valve on or as close as practicable to the cylinder to prevent loss of oxygen due to leakage in the system.
88. LOCATION AND MOUNTING. Determine the weight factor and c.g. limits for the installation prior to commencing the installation.
a. Mount the cylinder in the baggage compartment or other suitable location in such a position that the shutoff valve is readily accessible. If possible, provide access to this valve from inside the cabin so that it may be turned on in flight in the event that it was not opened prior to takeoff.
b. Fasten the cylinder brackets securely to the aircraft, preferably to a frame member or floorboard using AN bolts with fiber or similar locking nuts. Add sufficient plates, gussets, stringers, cross-bracing, or other reinforcements, where necessary, to provide a mounting that will withstand the inertia forces stipulated in chapter 1 of this handbook.
c. When cylinders are located where they may be damaged by baggage or stored materials, protect them by a suitable guard or covering & Provide at least ½ inch of clear airspace between any cylinder and a firewall or shroud isolating a designated fire zone.
e. Mount the regulator close to the cylinder to avoid long high-pressure lines.
f. Store the masks in such a way that there will be a minimum delay in removing and putting them into use.
Chap 6
Rev. 1977
• 89. THREAD COMPOUND. Use antiseize or thread-sealing compound conforming to Specification MIL-T-5542-B, or equivalent.
a. Do not use compound on aluminum alloy flared tube fittings having straight threads.
Proper flaring and tightening should be sufficient to make a flared tube connection leakproof.
b. Treat all male-tapered pipe threads with antiseize and sealing compound (MIL-T-5542-B, or tetrafluroethylene tape MIL-T-27730), or equivalent.
c. Apply the compound in accordance with the manufacturer's recommendation. Make sure that the compounds are carefully and sparingly applied only to male threads, coating the first three threads from the end of the fitting. Do not use compound on the coupling sleeves or on the outside of the tube flares.
90. FUNCTIONAL TEST.
Before inspection plates, cover plates, or upholstering are replaced, make a system check including at least the following:
a. Open cylinder valve slowly and observe the pressure gauge.
b. Open supply valve and remove one of the mask tubes and bayonet fittings from one of the masks in the kit. Plug the bayonet into each of the oxygen outlets. A small flow should be noted from each of the outlets. This can be detected by holding the tube to the lips while the bayonet is plugged into an outlet.
c. Check the complete system for leaks. This can be done with a soap solution made only from a mild (castile) soap or by leak-detector solution supplied by the oxygen equipment manufacturer.
d. If leaks are found, close the cylinder shutoff valve and reduce the pressure in the system by plugging a mask tube into one of the outlets or by carefully loosening one of the connections in the system. When the pressure has been reduced to zero, make the necessary repairs. Repeat the procedure in 90c until no leaks are found in the Caution: Never tighten oxygen system fittings with oxygen pressure applied.
Chap 6 AC 43.13-2A
e. Test each outlet for leaks at the point where the mask tube plugs in. This can be done by drawing a soap bubble over each of the outlets.
Use the solution sparingly to prevent clogging the outlet by soap. Remove all residue to prevent accumulation of dirt.
f. Examine the system to determine that the flow of oxygen through each outlet is at least equal to the minimum required by the pertinent requirements at all altitudes at which the aircraft is to be operated. This can be accomplished by one of the following methods:
(1) In a continuous flow system when the calibration (inlet pressure vs. flow) of the orifices used at the plug-in outlets is known, the pressure in the low-pressure distribution line can be measured at the point which is subject to the greatest pressure drop. Do this with oxygen flowing from all outlets. The pressure thus measured should indicate a flow equal to or greater than the minimum flow required.
(2) In lieu of the above procedure, the flow of oxygen, through the outlet which is subject to the greatest pressure drop, may be measured with all other outlets open. Gas meters, rotometers, or other suitable means may be used to measure flows.
(3) The measurement of oxygen flow in a continuous flow system which uses a manually adjusted regulator can be accomplished at sea level. However, in a continuous flow system which uses an automatic-type regulator, it may be necessary to check the flow at maximum altitude which will be encountered during the normal operation of the aircraft. The manufacturer of the particular continuous-flow regulator used should be able to furnish data on the operating characteristics of the regulator from which it can be determined whether a flight check is necessary.
(4) The checking of the amount of flow through the various outlets in a diluter-demand or straight-demand system is not necessary since the flow characteristics of the particular regulator being used may be obtained from the manufacturer of the regulator. However, in such systems the availability of oxygen to each regulator should be checked by turning the lever of the diluter-demand regulator to the "100 percent oxygen position and inhaling through the tube via the mask to determine whether the regulator valve and the flow indicator are operating.
AC 43.13-2A
g. Provide one of the following acceptable means or equivalent to indicate oxygen flow to each user by :
(1) Listening for audible indication of oxygen flow.
(2) Watching for inflation of the rebreather or reservoir bag.
Rev. 1977
(3) Installation of a flow indicator.
91. OPERATING INSTRUCTIONS. Provide instructions appropriate to the type of system and masks installed for the pilot on placards. Include in these instructions a graph or a table which will show the duration of the oxygen supply for the various cylinder pressures and pressure altitudes.
ACTUAL DURATION IN HOURS AT VARIOUS ALTITUDES Number of Persons 8000 Ft. 10,000 Ft. 12,000 Ft. 15,000 Ft. 20,000 Ft.
Pilot only 7.6 hr. 7.1 hr. 6.7 hr. 6.35 hr. 5.83 hr.
Pilot and 1 Passenger 5.07 hr. 4.74 hr. 4.47 hr. 4.24 hr. 3.88 hr.
Pilot and 2 Passengers 3.8 hr. 3.55 hr. 3.36 hr. 3.18 hr. 2.92 hr.
Pilot and 3 Passengers 3.04 hr. 2.84 hr. 2.68 hr. 2.54 hr. 2.34 hr.
Pilot and 4 Passengers 2.53 hr. 2.37 hr. 2.24 hr. 2.12 hr. 1.94 hr.
NOTE: The above duration time is based on a fully charged 48 cubic-foot cylinder. For duration using 63 cubic-foot cylinder, multiply any duration by 1.3.
FIGURE 6.1-Typical oxygen duration table.
Regulator .032 aluminum Hinge Typical example of shroud Cylinder bracke
• Large area washer AN bolt and self-locking nut fit contour of cylinder base. Cylinder support block - Cut to Oxygen cylinder bracket Secure with countersunk machine screw or wood screw. NOTE: Enclose cylinder and valve with shroud to prevent damage from baggage.
Reinforce floor, if necessary, to withstand the added lood.
Use aluminum or plywood of suficient thickness. FIGURE 6.3.---Typical baggage compartment mounting.
FIGURE 6.2.-Typical floor mounting.
46 Chap 6
Rev. 1977 AC 43.13-2A Alternate Location Cabin Wall Outlet Gage Regulator Cylinder Outside Filler Valve FroURE 6.4.-Typical oxygen installation in light twin aircraft.
92.-95. [RESERVED] Chap o 47 251-957 0 - 77 - 3