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
Rev. 1977 AC 43.13-2A Chapter 7. ROTORCRAFT EXTERNAL-LOAD DEVICE INSTALLATIONS Section 1. CARGO SLINGS
96. GENERAL. This section contains structural and design information for the fabrication and installation of a cargo sling used as an externalload attaching means for a Class B rotorcraftload combination operation under FAR Part 133.
As an external-load attaching means, a cargo sling" includes a quick-release device and the associated cables, fittings, etc., used for the attachment of the cargo sling to the rotorcraft.
97. QUICK-RELEASE DEVICE. Section 133.43 (d) of the FARs specifies the requirements for the quick-release device. In addition to commercially manufactured helicopter cargo hooks, some surplus military bomb releases meet the requirements of that section.
98. LOCATION OF CARGO RELEASE IN RELATION TO THE ROTORCRAFT'S C.G. LIMITS.
a. An ideal location of the cargo release would be one that allows the line of action to pass through the rotorcraft's center of gravity at all times. (See fig. 7.1, illus. A.) However, with « Lines of + Line of action action Effective pivot point Moment
• Arms Arm action Effective pivot Effective pivot pointe F F FIGURE 7.1.-Location of cargo release in relation to the rotorcraft's center of gravity.
Chap 7
AC 43.13-2A Rev. 1977 most cargo sling installations, this ideal situation is realized only when the line of action is vertical or near vertical and through the rotorcraft's c.g.
(See fig. 7.1, illus. B.)
b. Whenever the line of action does not pass through the rotorcraft's c.g. due to the attachment method used, acceleration forces, or aerodynamic forces, the rotorcraft-load combined center of gravity will shift from the rotorcraft's c.g. position. Depending upon the factors involved, the shift may occur along either or both the longitudinal or lateral axes. The amount of shift is dependent upon the force applied (F) and the length of the arm of the line of action. Their product (F x Arm) yields a moment which can be used to determine the rotorcraft-load combined center of gravity. (See fig. 7. 1, illus. C.) If the rotorcraft-load center of gravity is allowed to shift beyond the rotorcraft's approved center of gravity limits, the rotorcraft may become violently uncontrollable.
c. Thus, any attachment method or location which will decrease the length of the arm will reduce the distance that the combined center of gravity will shift for a given load (F) and line of action angle. (See fig. 7.1, illus. D.)
99. MAXIMUM EXTERNAL LOAD. The maximum external load (including the weight of the cargo sling) for which authorization is requested may not exceed the rated capacity of the quick-release should not be attached in such a manner as to provide sling-leg angles of less than 30 degrees.
102. MINIMUM SLING-LEG CABLE STRENGHT. An analysis which considered the effects of 30-degree sling angles showed that the minimum cable strength design factor required would be 2.5 times the maximum external load for each leg regardless of the number of legs. Although this is the minimum strength required by Part 133, it may be desirable to double this value to allow for deterioration of the sling-leg cables in service.
This will result in a cable strength equal to 5 times the maximum external load.
Example: Maximum external load 850 pounds Minimum required sling-leg cable strength 850 × 2.5=2125 Minimum desired sling-leg strength 850 × 2.5 x 2=4250 A 3/16-inch, nonflexible 19-wire cable (MIL-W- 6940) provides a satisfactory cable strength. See figure 4.1, chapter 4, of AC 43.13-14 for a table of breaking strength of steel cable.
venience, the cable sizes desired for various loads have been calculated and are tabulated in figure
7.2 based on a factor of 5:
Aircraft Cable Size For Each Cargo Sling Leg Махітит MIL-C-5699 External Load and (pounds) MIL-W-6940 MIL-W-1511 MIL-C-5424 1/16 3/32 3/32
100. STATIC TEST. The cargo sling installation 200 3/32 1/8 1/8 must be able to withstand the static load required by FAR 133.43(a). Conduct the test as outlined 300 400 1/8 7/64 1/8 1/8 1/8 5/32 in Chapter 1 of this advisory circular. If re- 500 600 5/32 5/32 5/32 3/16 3/16 3/16 quired during the test, supports may be placed 700 3/16 3/16 3/16 at the landing gear to airframe attach fittings to 800 3/16 3/16 7/32 prevent detrimental deformation of the landing gear due to the weight of the aircraft. 1,000 1,200 900 3/16 7/32 7/32 7/32 7/32 1/4 7/32 7/32 1/4 1,400 1/4 1/4 9/32
101. SLING-LEG ANGLES OF CABLE-SUPPORTED 1,600 1/4 9/32 5/16 SUINGS. The optimum sling-leg angle (measured 1,800 &/16 5/16 5/16 from the horizontal) is 45 to 60 degrees. Mini- 2,000 5/16 11/32 3/8 mum tension in a sling leg occurs with a sling-leg angle of 90 degrees, and the tension approaches FIGURE 7.2.-Cable Load Table.
infinity as the angle approaches zero. 103. SLING INSTALLATION. Attach the cargo sling larger sling-leg angles are desirable from a stand- to landing gear members or other structure cappoint of cable strength requirements. Slings able of supporting the loads to be carried. Install 50 Chap 7
Rev. 1977 the quick-release device in a level attitude with the throat opening facing the direction as indicated on the quick-release device. When cables are used to support the quick-release device, make sure the cables are not twisted or allowed to twist in the direction to unlay the cable.
Some cargo release devices are provided with a fitting to permit installation of a guideline to assist in fully automatic engagement of the load target ring or load bridle. Secure the guideline to the quick-release device with a shear pin of a definite known value which will shear if a load becomes entangled on or over the guideline. Provision should also be made for cable-supported slings to be drawn up against the fuselage into a stowage position to prevent striking or dragging the release on the ground when not in use.
AC 43.13-2A
104. INSTALLATION OF RELEASE CONTROLS. See figure 7.3 for typical wiring diagram of the electrical controls.
a. Install a cargo release master switch, readily accessible to the pilot, to provide a means of deactivating the release circuit. The power for the electrical release circuit should originate at the primary bus. The "auto" position of the release master switch on some cargo release units provides for automatic release when the load contacts the ground and the load on the release is reduced to a preset value.
b. Install the cargo release switch on one of the pilot's primary controls. It is usually installed on the cyclic stick to allow the pilot to release the load with minimum distraction after maneuvering the load into the release position.
RELEASE SWITCH (ON CYCLIC CONTROL)
RELEASE MASTER SWITCH Automatic OFT OPEN
RELEASE
INDICATOR LIGHT
CIRCUTT
BREAKER
QUICK RELEASE DEVICE
PRIMARY BUS
AUTO-RELEASE
RELEASE MICROSWITCH SOLENOID (Closes when load 18 reduced to preset value - usually 80-120 1b.)
SAFETY
MICROSWITCH (Release closed) FIGURE 7.3.-Typical cargo sling wiring diagram.
Chap 7 51
AC 43.13-2A
c. Install the emergency manual release control in a suitable position that is readily accessible to the pilot or other crewmember. Allow sufficient slack in the control cable to permit complete cargo movement without tripping the cargo release.
d. The manual ground release handle, a feature of some cargo release units, permits opening of the cargo release by ground personnel.
e. Label or placard all release controls as to function and operation.
105. FUNCTIONAL TEST. Test the release action of each release control of the quick-release device with various loads up to and including the maximum external load. This may be done in a test fixture or while installed on the rotorcraft, if the necessary load can be applied.
If the quick-release device incorporates an automatic release, the unit should not release the load when the master switch is placed in the iautomatic" position until the load on the device is reduced to the preset value, usually 80 to 120 pounds.
FIGURE 7.4.--Typical cargo sling installation No. 1.
Rev. 1977
106. SUPPLEMENTAL FLIGHT INFORMATION. The aircraft may not be used in Part 133 externalload operations until a Rotorcraft-Load Combination Flight Manual is prepared in accordance with section 133.47 of that Part.
FIGURE 7.5.- -Typical cargo sling installation No. 1 (showing fuselage attachment fitting).
FIGURE 7.6-Typical cargo sling installation No. 1 (showing fore and aft limiting stops).
FIGURE 7.7.-Typical cargo sling installation No. 2 (cargo hook attached directly to underside of fuselage).
Chap 7
Rev. 1977 AC 43.13-2A FIGURE 7.8.-Typical cargo sling installation No. 3 (4-leg, cable suspended).
20.
FIGURE 7.9.-Typical cargo sling installation No. 3 (showing cable sling leg attachment to landing gear crosstube fitting).
FIGURE 7.10.- Typical cargo sling Installation No. 8 (showing cargo sling in stowed position).
107.-110. [RESERVED] Chap 7
AC 43.13-2A Rev. 1977 Section 2. CARGO RACKS
111. GENERAL. This section contains structural and design information for the fabrication and installation of a cargo rack used as an externalload attaching means for a Class A rotorcraftload combination operation under FAR Part 133.
112. FABRICATION OF CARGO RACKS. The type of construction and method of attachment depend upon the material to be used and the configuration of the rotorcraft involved. Illustrations of typical construction and installation methods are shown in figures 7.11-7.15.
113. STATIC TEST. The cargo rack installation must be able to withstand the static test load required by FAR 133.43(a). Conduct the test as outlined in chapter 1 of this handbook.
114. SUPPLEMENTAL FLIGHT INFORMATION. The aircraft may not be used in Part 133 externalload operations until a rotorcraft-load combination flight manual is prepared in accordance with section 133.47 of that Part.
FIGURE 7.12.-Typical cargo rack installation No. 1 (showing attachment detail).
FIoURE 7.11.-Typical cargo rack installation No. 1.
54 Chap 7