7-5
7.5.4.2 Flush with naphtha conforming to Specification TT-N-95B; blow clean and dry off all solvent with water-pumped air; flush with anti-icing fluid conforming to Specification TT-1-735A 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 ºF for a half hour.
7.5.4.3 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 ºF for a half an hour.
7.5.5 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.
7.5.6 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 a 1/2-inch clearance between the plumbing and any rigid control tubes or other rigid moving parts of the aircraft.
7.5.7 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.
7.5.8 Route the oxygen system tubing, fittings, and equipment away from hot air ducts and equipment. Insulate or provide space between these items to prevent heating the oxygen system.
7.5.9 Mount all plumbing in a manner that prevents vibration and chafing. Support a 3/16-inch O.D. copper line each 24 inches and a 3/16-inch O.D. aluminum each 36 inches with cushioned loop-type line support clamps (AN-742) or equivalent.
7.5.10 Locate the oxygen supply valve (control valve) 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 oxygen supply valves since the pilot can control the flow of oxygen by engaging and disengaging the plug-in type of oxygen mask.
7.5.11 Filler connections, if provided, are recommended to be located outside the fuselage skin or isolated in a manner that would prevent leaking oxygen from entering the aircraft. Any nearby source of fuel, oil, or hydraulic fuel should be carefully evaluated under normal or malfunction conditions. Each filler connection should be placarded. Additionally, any valve (aircraft or ground servicing equipment) associated with high pressure should be slow acting.
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.
7-6
7.6 Equipment Location and Mounting. Prior to commencing the installation, determine the weight/load factors and center of gravity (CG) limits.
7.6.1 Mount the cylinder in the baggage compartment or other suitable location in such a position that the shutoff valve is readily accessible. Provide access to this valve from inside the cabin so that it may be turned on or off in flight.
7.6.2 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 2, Structural Data.
7.6.3 When cylinders are located where baggage or stored materials may damage them, protect them with a suitable guard or covering.
7.6.4 Provide at least 1/2-inch of clear airspace between any cylinder and a firewall or shroud isolating a designated fire zone.
7.6.5 Mount the regulator close to the cylinder to avoid long high-pressure lines.
7.6.6 Store the masks so that there will be a minimum delay in removing and putting them into use.
7.7 Thread Compound. Use anti-seize or thread-sealing compound conforming to Specification MIL-PRF-27617F or equivalent.
7.7.1 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.
7.7.2 Treat all male-tapered pipe threads with antiseize and sealing compound (MIL-PRF-27617F, or polytetrafluorethylene tape A-A-58092) or equivalent.
7.7.3 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.
7.8 Functional Test. Before inspection plates, cover plates, or upholstering are replaced, make a system check that includes at least the following:
7.8.1 Open the cylinder valve slowly and observe the pressure gauge.
7.8.2 Open the 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.
7-7
7.8.3 Check the complete system for leaks. This can be done with a soap solution made only from mild (castile) soap or by leak-detector solution supplied by the oxygen equipment manufacturer.
7.8.4 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 until no leaks are found in the system.
WARNING: Never tighten oxygen system fittings with oxygen pressure applied.
7.8.5 Test each outlet for leaks at the point where the mask tube plugs in. This can be done by using a soapy solution over each of the outlets. Use the solution sparingly to prevent clogging the outlet with soap. Remove all residue to prevent the accumulation of dirt.
7.8.6 Examine the system to determine if 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 operated. This can be accomplished by one of the following methods:
7.8.6.1 In a continuous-flow system, when the calibration (inlet pressure versus 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 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.
7.8.6.2 In lieu of the above procedure, the flow of oxygen through the outlet that is subject to the greatest pressure drop may be measured with all other outlets open. Gas meters, rotameters, or other suitable means may be used to measure flows.
7.8.6.3 The measurement of oxygen flow in a continuous-flow system that uses a manually adjusted regulator can be accomplished at sea level. However, in a continuous-flow system that uses an automatic-type regulator, it may be necessary to check the flow at the maximum altitude that will be encountered during the aircraft’s normal operation. 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 if a flight check is necessary.
7.8.6.4 Checking 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.
7-8
7.8.7 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.
3. Installing a flow indicator.
7.9 Operating Instructions. On placards, provide instructions appropriate to the type of system and masks installed for the pilot. Include in these instructions a graph or a table showing the duration of the oxygen supply for the various cylinder pressures and pressure altitudes (see Table 7-1).
Table 7-1. Typical Oxygen Duration Table Actual Duration in Hours at Various Altitudes Number of Persons 8,000 Feet 10,000 Feet 12,000 Feet 15,000 Feet 20,000 Feet Pilot Only 7.6 hours 7.1 hours 6.7 hours 6.35 hours 5.83 hours Pilot and One Passenger 5.07 hours 4.74 hours 4.47 hours 4.24 hours 3.88 hours Pilot and Two Passengers 3.8 hours 3.55 hours 3.36 hours 3.18 hours 2.92 hours Pilot and Three Passengers 3.04 hours 2.84 hours 2.68 hours 2.54 hours 2.34 hours Pilot and Four Passengers 2.53 hours 2.37 hours 2.24 hours 2.12 hours 1.94 hours NOTE: The above duration time is based on a fully charged 48 cubic-foot cylinder. For duration using a 63 cubic-foot cylinder, multiply any duration by 1.3.
Figure 7-1. Typical Floor Mounting Regulator Alternater Location Cylinder Bracket Floor Large area washer AN bolt and self-locking nut Oxygen cylinder bracket Reinforce floor, if necessary, to withstand the added load.
Like aluminum or plvwood of sufficient thickness.
7-9
Figure 7-2. Typical Baggage Compartment Mounting .032 aluminum Hinge Fasteners к..
Typical example of shroud Bracket Bulkhead ...
Self-locking Nut Washer Doubler Cylinder support block - Cut to fit contour of cylinder base. Secure with countersunk machine NOTE: Enclose cylinder and valve with shroud screw or wood screw. to prevent damage from baggage.
7-10
7-11 Figure 7-3. Typical Oxygen Installation in Light Twin Aircraft
7-12 Section 3. Airworthiness Compliance Check Sheet: Oxygen System Installation in Unpressurized Aircraft
7.10 General. Oxygen system installations made in accordance with an FAA-approved airframe manufacturer or other FAA-approved installations may be accepted without further investigation. On other installations, the following points should be checked to determine if the installation is satisfactory.
7.11 Applicable Federal Aviation Regulations. Determine if the installation complies with the regulations listed in paragraph 7.3.
7.12 Structural Requirements.
7.12.1 If changes or alterations of the aircraft structure are made (mounting of oxygen cylinder), determine if the original strength and integrity of the structure is retained.
7.12.2 If gages are added to the instrument panel or an outside filler valve is installed on the fuselage, determine if the structural integrity of the panel and airframe or its supporting structure is retained.
7.12.3 Determine if the extent of the modification has affected the CG of the aircraft evaluated.
7.12.4 Check whether all lines are properly routed and supported.
7.13 Hazards to the Aircraft or its Occupants. Determine if the design of the oxygen system is evaluated to ensure that the aircraft and its occupants are safe from hazards identified in paragraph 7.2.
7.14 Operating Aspects.
7.14.1 When required by the operating rules for the use of supplemental oxygen, determine if the system’s capacity is sufficient to supply oxygen to all combinations of crew and passengers.
7.14.2 Determine if the oxygen system provides the required flow.
7.14.3 Determine if the oxygen regulator controls are accessible to a member of the flightcrew in flight.
7.14.4 Determine if there is a means, readily available to the crew in flight, to turn on and shut off the oxygen supply at the high-pressure source.
7.14.5 Check whether there is a means to allow the crew to readily determine during flight the quantity of oxygen available in each source of supply.
7-13
7.15 Detail Design Standards. Determine if:
1. All parts are suitable for use with oxygen.
2. The regulator is located as close as physically possible to the oxygen cylinder and minimizes the use of fittings.
3. No solid metal lines are 100 percent visible during normal operation.
4. Each breathing device has a device attached that visually shows the flow of oxygen.
5. The lines that pass through potential fire zones are stainless steel.
6. When oxygen system components are added to the baggage compartments, there are provisions to protect the system components from shifting cargo.
7. Where oxygen components are installed, the compartment is placarded against the storage of oil or hydrocarbons.
8. A smoke detector is installed where oxygen cylinders are installed in a closed, nonaccessible compartment.
9. The cargo area weight limitations placard is updated.
10. All oxygen outlets are placarded.
11. “No Smoking When Oxygen Is In Use” placards and other appropriate placards
(i.e., operation instructions) are visible to the crew and occupants of the aircraft.
7.16 Instructions for Continued Airworthiness (ICA). Determine if:
1. There are written instructions concerning system operation, maintenance, and cylinder changing procedures.
2. There are written instructions in the use of the oxygen equipment in the Aircraft Flight Manual (AFM) or placards.
Note: Any changes to the AFM must be approved by the FAA.
3. There are written inspection and test schedules and procedures.
4. Mechanical drawings and wiring diagrams are available, as required.
5. Written instructions are available concerning oxygen cylinder hydrostatic testing requirements and cylinder replacement requirements.
6. There is a scheduled (annual) check of a constant flow system manifold output pressure for recommended output pressure.
7. The guidance contained in AC 43.13-1, Chapter 9, Aircraft Systems and Components, paragraphs 9-47 through 9-51 is considered in the design of the oxygen maintenance program.
7-14
7.17 Recordkeeping. Determine if:
1. A maintenance record entry has been made. Refer to 14 CFR § 43.9.
2. The equipment list and Weight and Balance (W&B) have been revised.
8-1 CHAPTER 8. ROTORCRAFT EXTERNAL-LOAD DEVICE INSTALLATIONS,
CARGO SLINGS, AND EXTERNAL RACKS Section 1. General
8.1 Purpose. This section contains structural and design information for the fabrication and installation of a cargo sling used as an external-load attaching means for a Class B rotorcraft-load combination operation under 14 CFR part 133. As an external-load attaching means, a “cargo sling” includes a quick-release device (hook) and the associated cables, fittings, etc., used for the attachment of the cargo sling to the rotorcraft.
Title 14 CFR § 133.43(b) specifies the requirements for the quick-release device.
8.2 Hazards and Warnings. Particular attention should be paid to the effect of the sling load on the lateral as well as the fore and aft center of gravity (CG) of the rotorcraft. Use type certificate (TC), Parts Manufacturer Approval (PMA), TS0, or Designated Engineering Representative (DER) approved parts.
8.3 References. It is the installer’s responsibility to ensure that the latest revisions of any regulations, ACs, manufacturer’s data, etc., are used in any cargo sling or rack installation. Refer to 14 CFR parts 27 and 29; Civil Air Regulation (CAR) 6, Rotorcraft Airworthiness; Normal Category; and CAR 7, Rotorcraft Airworthiness; Transport Categories.
8.4 Installation Considerations.
8.4.1 Location of Cargo Release in Relation to the Rotorcraft’s CG Limits. An ideal location would be one that allows the line of action to pass through the rotorcraft’s CG at all times (see Figure 8-1, Location of Cargo Release in Relation to the Rotorcraft’s Center of Gravity, Illustration A). However, with 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 CG (see Figure 8-1, Illustration B).
8.4.1.1 Whenever the line of action does not pass through the rotorcraft’s CG due to the attachment method used, acceleration forces, or aerodynamic forces, the rotorcraft-load combined CG will shift from the rotorcraft’s CG 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 that can be used to determine the rotorcraft-load combined CG (see Figure 8-1, Illustration C). If the rotorcraft-load CG is allowed to shift beyond the rotorcraft’s approved CG limits, the rotorcraft may become violently uncontrollable.
8-2 Figure 8-1. Location of Cargo Release in Relation to the Rotorcraft’s Center of Gravity
8.4.1.2 Thus, any attachment method or location that decreases the length of the arm will reduce the distance that the combined CG will shift for a given load (F) and line of action angle (see Figure 8-1, Illustration D).
8.4.2 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 device.
8.5 Fabrication and Installation.
8.5.1 Static Test. The cargo sling installation must be able to withstand the static load required by 14 CFR §§ 27.865(a) and 29.865(a). Conduct the test as outlined in Chapter 2, Structural Data. If required during the test, supports may be placed at the landing gear to airframe attach fittings to prevent detrimental deformation of the landing gear due to the weight of the aircraft.
8.5.2 Sling-Leg Angles of Cable-Supported Slings. The optimum sling-leg angle (measured from the horizontal) is 45 to 60 degrees. Minimum tension in a sling leg occurs with a sling-leg angle of 90 degrees, and the tension approaches infinity as the angle approaches zero. Thus, larger sling-leg angles are desirable from a standpoint of cable strength requirements. Slings should not be attached in such a manner as to provide sling-leg angles of less than 30 degrees.