Par 618 Page 59 SECTION 3. AIRWORTHINESS COMPLIANCE CHECK SHEET: OXYGEN SYSTEM
INSTALLATION IN UNPRESSURIZED AIRCRAFT
618. GENERAL. Oxygen system installations made in accordance with 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.
619. APPLICABLE FEDERAL AVIATION REGULATIONS. Determine if the installation complies with the re gulations listed in paragraph 602.
620. STRUCTURAL REQUIREMENTS.
a. 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.
b. If gages are added to the instrument panel or an outside filler valve installed on the fuselage, determine if the structural integrity of the panel and airframe or its supporting structure is retained.
c. Determine if the extent of the modification has affected the center of gravity (CG) of the aircraft evaluated.
d. Check whether all lines are properly routed and supported.
621. 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 601.
622. OPERATING ASPECTS.
a. 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.
b. Determine if the oxygen system provides the required flow.
c. Determine if the oxygen regulator controls are accessible to a member of the flightcrew in flight.
d. 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.
e. 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.
623. DETAIL DESIGN STANDARDS. Determine if:
a. All parts are suitable for use with oxygen.
b. The regulator is located as close as physically possible to the oxygen cylinder and minimizes the use of fittings.
c. No lines are 100 percent visible during normal operation solid metal lines.
d. Each breathing device has a device attached that visually shows the flow of oxygen.
e. The lines that pass through potential fire zones are stainless steel.
f. When oxygen system components are added to the baggage compartments, there are provisions to protect the system components from shifting cargo.
g. Where oxygen components are installed, the compartment is placarded against the storage of oil or hydrocarbons.
h. A smoke detector is installed where oxygen cylinders are installed in a closed, nonaccessible compartment.
i. The cargo area weight limitations placard is updated.
j. All oxygen outlets are placarded.
k. “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.
624. INSTRUCTIONS FOR CONTINUED AIRWORTHINESS. Determine if:
a. There are written instructions concerning system operation, maintenance, and cylinder changing procedures.
b. There are written instructions in the use of the oxygen equipment in the AFM or placards.
NOTE: Any changes to the AFM must be approved by the FAA.
c. There are written inspection and test schedules and procedures.
d. Mechanical drawings and wiring diagrams are available, as required.
e. Written instructions are available concerning oxygen cylinder hydrostatic testing requirements and cylinder replacement requirements.
f. There is a scheduled (annual) check of a constant flow system manifold output pressure for recommended output pressure.
g. The guidance contained in AC 43.13-1 (current edition), paragraphs 9-47 to 9-51 is considered in the design of the oxygen maintenance program.
625. RECORDKEEPING. Determine if:
a. A maintenance record entry has been made.
(Reference § 43.9.)
b. The equipment list and weight and balance has been revised. (Ref erence Order 8310.6, chapter 1.)
626. THRU 699. RESERVED
Par 623 Page 60
CHAPTER 7. ROTORCRAFT EXTERNAL-LOAD-DEVICE
INSTALLATIONS CARGO SLINGS AND EXTERNAL RACKS SECTION 1. GENERAL
700. 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 Title 14 of the Code of Federal Regulations (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.
Part 133, § 133.43(d) specifies the requirements for the quick-release device.
701. 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 TC PMA, T50 or Designated Engineering Representative approved parts.
702. REFERENCES. It is the installer’s responsibility to ensure that the latest revisions of any regulations, advisory circulars, manufacturer’s data, etc., are used in any cargo sling or rack installation. Reference Title 14 of the Code of Federal Regulations part 27 and Civil Aviation Regulation 6, Rotorcraft Airworthiness; Normal Category.
703. INSTALLATION CONSIDERATIONS.
a. 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 7-1, 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 7-1, Illustration B.)
(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 shif t 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 CG (See Figure 7-1, Illustration C.) If the rotorcraft-load CG is allowed to shift beyond the rotorcraft's approved CG limits, the rotorcraft may become violently uncontrollable.
Par 700 Page 61
FIGURE 7-1. LOCATION OF CARGO RELEASE IN RELATION TO THE ROTORCRAFT’S
CENTER OF GRAVITY
(2) Thus, any attachment method or location which will decrease 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 7-1, Illustration D.)
b. 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.
704. FABRICATION AND INSTALLATION.
a. Static Test. The cargo sling installation must be able to withstand the static load required by § 133.43(a). Conduct the test as outlined in chapter 1. 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.
b. 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.
c. Minimum Sling-Leg Cable Strength.
(1) 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 Par 703 Page 62
will result in a cable strength equal to five times the maximum external load.
Example: Maximum external load 850 pounds Minimum required sling-leg cable strength 850 x 2.5 = 2125 Minimum desired sling-leg cable strength 850 x 2.5 x 2 = 4250
(2) A 3/16-inch, nonflexible 19-wire cable (MIL-W-6940) provides a satisfactory cable strength. For convenience, the cable sizes desired for various loads have been calculated and are tabulated in Table 7-1 based on a factor of 5:
TABLE 7-1. CABLE LOAD TABLE Aircraft Cable Size For Each Cargo Sling Leg
Maximum External Load (pounds)
MIL-C-5693 and MIL-W-6940
MIL-W-1511
MIL-C-5424 100 200 300 400 500 600 700 800 900 1,000 1,200 1,400 1,600 1,800 2,000 1/16 3/32 7/64 1/8 5/32 5/32 3/16 3/16 3/16 7/32 7/32 ¼ 1/4 5/16 5/16 3/32 1/8 1/8 1/8 5/32 3/16 3/16 3/16 7/32 7/32 1/4 1/4 9/32 5/16 11/32 3/32 1/8 1/8 5/32 3/16 3/16 3/16 7/32 7/32 7/32 ¼ 9/32 5/16 5/16 3/8
d. Sling Installation.
(1) Attach the cargo sling to landing gear members or other structure capable of supporting the loads to be carried. Install 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 un-lay the cable.
(2) 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.
e. Installation of Release Controls. See Figure 7-2 for typical wiring diagram of the electrical controls.
(1) 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.
(2) 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.
Par 704 Page 63
FIGURE 7-2. TYPICAL CARGO SLING WIRING DIAGRAM
(3) 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.
(4) The manual ground release handle, a feature of some cargo release units, permits opening of the cargo release by ground personnel.
(5) Label or placard all release controls as to each function and operation.
f. Functional Test.
(1) 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.
(2) If the quick-release device incorporates an automatic release, the unit should not release the load when the master switch is placed in the "automatic" position until the load on the device is reduced to the preset value, usually 80 to 120 pounds.
FIGURE 7-3. TYPICAL CARGO SLING INSTALLATION NO. 1
Par 704 Page 64
g. Supplemental Flight Information. The aircraft may not be used in part 133 external-load operations until a Rotorcraft-Load Combination Flight Manual is prepared in accordance with § 133.47 of that part. Appropriate entries should also be made in the aircraft’s weight and balance data, equipment list, and logbooks. The FAA Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance), should also be executed as required by part 43, § 43.5(a) and (b).
h. Inspection and Maintenance. Inspection of the complete installation should be accomplished prior to each lift for security and functionality.
Maintenance should be accomplished in accordance with the manufacturers instructions.
705. THRU 706. RESERVED
FIGURE 7-4. TYPICAL CARGO SLING INSTALLATION NO. 1 (SHOWING FUSELAGE ATTACHMENT FITTING)
FIGURE 7-5. TYPICAL CARGO SLING INSTALLATION NO. 1 (SHOWING FORE AFT LIMITING STOPS)
Par 704 Page 65
FIGURE 7-6. TYPICAL CARGO SLING INSTALLATION NO. 2 (CARGO HOOK ATTACHED
DIRECTLY TO UNDERSIDE OF FUSELAGE)
FIGURE 7-7. TYPICAL CARGO SLING INSTALLATION NO. 3 (4-LEG, CABLE SUSPENDED)
FIGURE 7-8. TYPICAL CARGO SLING INSTALLATION NO. 3 (SHOWING CABLE SLING
LEG ATTACHMENT TO LANDING GEAR CROSSTUBE FITTING)
Par 704 Page 66
Par 704 Page 67 (and 68) FIGURE 7-9. TYPICAL CARGO SLING INSTALLATION NO. 3 (SHOWING CARGO SLING
IN STOWED POSITION)
Par 707 Page 69 SECTION 2. CARGO RACKS
707. GENERAL. This section contains structural and design information for the fabrication and installation of a cargo rack used as an external-load attaching means for a Class A rotorcraft-load combination operation under part 133.
708. FABRICATION OF CARGO RACKS. The type of construction and method of attachment depends upon the material to be used and the configuration of the rotorcraft involved. Illustrations of typical construction and installation methods are shown in Figures 7-10 through 7-14.
FIGURE 7-10. TYPICAL CARGO RACK INSTALLATION NO. 1
709. STATIC TEST. The cargo rack installation must be able to withstand the static test load required by § 133.43(a). Conduct the test as outlined in chapter 1.
710. SUPPLEMENTAL FLIGHT INFORM- ATION. The aircraft may not be used in part 133 external-load operations until a rotorcraft-load combination flight manual is prepared in accordance with § 133.47.
711. THRU 799. RESERVED
FIGURE 7-11. TYPICAL CARGO RACK INSTALLATION NO. 1 (SHOWING ATTACHMENT DETAIL)
FIGURE 7-12. TYPICAL CARGO RACK INSTALLATION NO. 2
Par 710 Page 70
Par 710 Page 71 (and 72) FIGURE 7-13. TYPICAL CARGO RACK INSTALLATION NO. 2 (SHOWING RACK PARTIALLY INSTALLED)