______________________________________________________________________ ______________________________________________________________________ *Requires acceptance by the cognizant Flight Standards District Office Note: Some rotorcraft manufacturers have qualified certain locations on the underside of their aircraft for mounting external equipment. The manufacturers will typically specify external equipment weight and dimensional limitations at those locations. The applicant should contact the manufacturer to see if this information is available as it could be used to reduce the applicant's certification effort.
(2) The critical structural loading conditions for substantiating the installation of agricultural dispensing equipment can be developed by using the associated occupant protection load factors provided in Figure AC 29 MG 5-1. These load factors are prescribed to prevent dispensing equipment from causing injuries to occupants in the event of an emergency landing. To ensure th is, adequate margins of safety should be used in the structural design consideration of dispensing equipment and dispensing equipment installations.
FIGURE AC 29 MG 5-1
ACCEPTABLE ULTIMATE LOAD FACTOR FOR
AGRICULTURAL DISPENSING EQUIPMENT DESIGN
UP DOWN SIDE FORWARD AFT Tanks & Equipment Mounted In Or Near The Fuselage
1.5g 4.0g 2.0g 4.0g Note 1
- - - - Spray Booms 1.5g 2.5g - - - - Note 1 2.5g Note 2 Note 1: An ultimate load factor of 2 G’ s is acceptable for externally side or under fuselage mounted tank and forward mounted spray booms where failure in a minor crash landing will not create a hazard to occupants or prevent an occupant’s exit from the rotorcraft.
Note 2: The aft loads for spray booms may be developed by the applicant based on the 111 percent of VNE for which certification is requested or the load factors of Figure AC 29 MG 5-1, whichever is greater.
(3) The applicant may elect to substantiate their product by either static or dynamic testing, by analysis, or any combination thereof.
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AC 29-2C, Chg 4 12/15/2009
(4) Lower load factors may be used only when justified by manufacturer’s data, rational analysis, actual rotorcraft flight data and ground load demonstrations, or any combination of these approaches.
(5) Tank pressure testing, while not mandated, is recommended for safety reasons. An acceptable procedure is incl uded in paragraph c.(4) under “Acceptable Means of Compliance.”
(6) Dispensing equipment installation attach points that are an integral part of the rotorcraft and have been certified to the appropriate airworthiness standards, need no further substantiation. This applies prov ided a load analysis indicates the dispensing system does not impose loads at the attach points which exceed those approved as part of the rotorcraft certification.
(7) A 5-inch ground clearance for skid gear equipped, newly manufactured rotorcraft has typically been used when installing dispensing equipment, such as belly mounted supply tanks/hoppers or when installing dual side mounted supply tanks/hoppers. This applies provided the rotorcraft design incorporates cross tubes or other skid gear reinforcing structure below the fuselage and the cross tubes have not experienced in-service permanent elastic deformation. For rotorcraft equipped with wheels and/or landing gear struts, the maximum system deflections should be considered when determining the 5 inches of acceptable static ground clearance. A 3-inch ground clearance has been found acceptable and may be approved for skid gear equipped rotorcraft to account for the in-service permanent elastic deformation allowed for skid gear members (i.e., cross tube deflections allowed per the maintenance manual). Cable supp orted systems (e.g., cargo hook installations) or dispensing systems utilizing flexible ducts, such as water snorkels, have been approved even though portions of the systems contact the surface during a normal landing. A determination should be made that these systems do not interfere with the safe landing of the rotorcraft.
(8) A number of rotorcraft are approved for external cargo operations that allow a gross weight higher than the approved internal gross weight limit. This difference is usually due to the allowable weight limit restriction of the landing gear. (The gear is not approved for the higher weight.) Those types of dispensing equipment, which can be loaded in flight to a weight that exceeds the allowable limit of the landing gear, should incorporate a reliable means that rapidly reduces the total aircraft gross weight to within allowable landing gear limits. In most cases, this will involve jettison of the disposable load. The time interval for this oper ation should be demonstrated, and should not exceed a recommended 3 seconds from a level flight condition.
(9) A flight check or demonstration of the agricultural dispensing equipment installation is normally conducted. This flight check should also qualitatively determine that no hazardous deflection or resonance in the rotorcraft or dispensing system exists.
For FAA flight operations approval, this flight check must be conducted under the requirements of § 133.41.
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(10) Recent service history has shown that external equipment and external fixture modifications that generate high drag loads in forward flight can affect main rotor mast bending loads. In lieu of a mast bending survey, a pre and post modification flight test may be conducted at identical weights, center-of-gravity (CG), power, and density altitude to compare a critical control position parameter (typically longitudinal cyclic stick position) at pre and post modification VNE airspeeds.
(i) should be reduced so that the post NE modification longitudinal cyclic stick position is slightly aft of (or less than) the premodification stick position. This alte rnative procedure assumes that the static longitudinal stability of the helicopter has not been altered by the modification. For helicopters with neutral static stability, a more comprehensive investigation may be required.
(ii) In some cases, a control position parameter other than longitudinal stick position may be critical. For example, a hea vy external device mounted to the side of the helicopter that gives a lateral CG close to the limit and an asymmetric yaw component would require pre and post modification lateral cyclic stick and pedal position measurements. Operating limitations other than VNE may need to be established, or reduced from pre-modification limitations, to ensure pre modification mast bending is not exceeded.
(11) For rotorcraft certificated in dual categories, the inspection requirements of § 21.187(b) must be observed when converting from restricted to transport category.
c. Acceptable Means of Compliance.
If required, the post modification V
(1) Analysis Method Static Tests . Static structural analysis may be used provided a methodology is applied that has been shown to be reliable for analyzing the type of structure. Structural subst antiation of tanks that are designed to contain liquid materials may be accomplished by pressure testing. For tanks or hoppers designed to contain dry material (e.g., dust or fertilizer), static load tests may be used to verify structural integrity. The tank/hopper, mounting hardware, and suppor t structure should all be substantiated to the load conditions specified and should consider the effects of internal fluid pressures, when applicable, in Figure AC 29 MG 5-1.
(2) . Static tests of tank/hoppers, mounting hardware, and support structure for each critical load condition may be accomplished using conventional techniques; such as, dead weight loading, whiffletree systems, and hydraulic rams. If tests of the tank and its mounting hardware are conducted using a test fixture representing the rotorcraft, the rotorcraft support structure may be substantiated independently by means of test or analysis, or both. Static test loads should be applied in combination with associated internal fluid pressure loadings. The ultimate loads specified in Figure AC 29 MG 5-1 should be sustained for at least 3 seconds without failure.
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AC 29-2C, Chg 4 12/15/2009
(3) (i Dynamic Tests ) If the applicant elects to test to the loading conditions in Figure AC 29 MG 5-1, the maneuvering and gust loadings will be considered to be adequately substantiated. For each condition, the crit ical volume and density of fluid should be used.
(ii) The tank and mounting hardware should support ultimate loads without permanent elastic deformation failure, respectively. The rotorcraft support structure may be included in the dynamic tests, or it may be substantiated separately via static test or analysis, or both, for each condition specified in Figure AC 29 MG 5-1.
(4) Pressure Testing. Internal pre ssure loads may be applied using the water standpipe technique. Standpipe water height should be accurately computed for each critical spray tank static test loading. Pre ssure testing of spray tanks is not absolutely essential but is recommended for safety reasons. This testing will also determine whether the joints and connections are tight and will not leak in addition to determining any weak spots in the construction. W here spraying is done with highly volatile and flammable liquids, or where the tank has a return line, such as in an engine oil tank where the fluid is pumped back into the tank, it is recommended that the tank be tested for a pressure of 5 pounds per square inch. For other liquids, and where no fluid return line is used, testing to 3 ½ pounds per square inch should be satisfactory. There are many ways of pressure testing a tank, however, it is believed that the simplest and easiest method is to fill the tank with water and use a standpipe filled with water. A 1 1/8-inch pipe can be connected to the venting tube or one adapted to the filler opening. In either case, the hei ght of the pipe would be the same. For a 3 ½ PSI test of the tank, the height of the water in the pipe would only need to be 8 feet and for a 5 PSI test only an 11 ½ -foot height of water will be needed. (See Figure AC 29 MG 5-2 below.)
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Pipe TANK 8' or 11 ½' 12/15/2009 AC 29-2C, Chg 4 FIGURE AC 29 MG 5-2 SKETCH OF TANK PRESSURE TEST Page MG 5 - 7
CHAPTER 3
AIRWORTHINESS STANDARDS
TRANSPORT CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG) AC 29 MG 6. EMERGENCY MEDI CAL SERVICE (EMS) SYSTEMS INSTALLATIONS INCLUDING: INTERIOR ARRANGEMENTS,
EQUIPMENT, HELICOPTER TERRAIN AWARENESS AND
WARNING SYSTEM (HTAWS), RADIO ALTIMETER, AND FLIGHT DATA MONITORING SYSTEM.
a. Explanation. This section pertain s to EMS configurations and associated rotorcraft airworthiness standards. EMS configurations are usually unique interior arrangements that are subject to the appropriate airworthiness standards, part 29 or its predecessor CAR part 7, to which the rotorcraft was certificated. No relief from the standards is intended except by § 21.21(b)(1) or an exemption. EMS configurations are seldom, if ever, done by the original manufacturer.
(1) The FAA has specified in the operating rules the minimum equipment required to operate as a helicopter air ambulance service provider (identified by an “*” in this guidance). This equipment, as well as all other equipment presented for evaluation and approval, is subject to compliance with airworthiness standards. Any equipment not essential to the safe operation of the aircraft may be approved provided the use, operation, and possible failure modes of the equipment are not hazardous to the aircraft. Safe flight, safe landing, and prompt evacuation of the rotorcraft, in the event of a minor crash landing, for any reason, are the objectives of the FAA evaluation of interiors and equipment unique to EMS.
(i) For example, a rotorcraft equipped only for transportation of a non-ambulatory person (e.g., a police rotorcraft with one litter) as well as a rotorcraft equipped with multiple litters and complete life support systems and two or more attendants or medical personnel may be submitted for approval. These configurations will be evaluated to the airworthiness standards appropriate to the rotorcraft certification basis.
(ii) Transport category rotorcraft should comply with flightcrew and passenger safety standards, which will result in the need to reevaluate certain features of the basic certified rotorcraft related to the EMS arrangement, such as doors and emergency exits, and occupant protection. Compliance with airworthiness standards results in an emergency interior lighting system, placards or markings for doors and exits, exit size, exit quantity and location, exit access, safety belts, and possibly shoulder harnesses or other restraint or passenger protection means to be retained as part of the rotorcraft’s basic type design. The features, plac ards, markings, and “emergency” systems required as a part of the rotorcraft’s basic type design, should be retained unless Page MG 6 - 1
AC 29-2C, Chg 4 2/27/2014 specific replacements or alternate designs are necessary for the EMS configuration to comply with airworthiness standards.
(2) Many EMS configurations of transport rotorcraft are equipped with the following:
(i) Attendant and medical personnel seats, which may swivel.
(ii) Multiple litters, some of which may tilt.
(iii) Medical equipment stowage compartments.
(iv) Life support and other complex medical equipment.
(v) Human infant incubator (isolette).
(vi) Curtains or other interior light shielding for the flightcrew compartment.
(vii) External loud speakers and search lights.
(viii) Special internal and external communication radio equipment.
*(ix) Flight data monitoring system (FDMS).
*(x) Radio altimeter.
*(xi) Helicopter terrain awareness and warning system (HTAWS).
*(3) All helicopter air ambulance service providers are required to operate at all times under a part 135 subpart L certificate. The equipment required to obtain operational approval includes:
*(i) FDMS. The installation guidance is in paragraph b.(13) of this MG.
*(ii) Radio Altimeter (RAD ALT). The installation guidance is in paragraph
b.(14) of this MG.
*(iii) HTAWS. HTAWS is requir ed for operations under part 135 subpart L, Helicopter Air Ambulance Equipment, Operation, and Training Requirements;
§ 135.605, Helicopter Terrain Awareness and Warning System (HTAWS). The design standards are in Technical Standard Order (TSO)-C194 and the installation guidance is in AC 29-2 MG 18.
b. Procedures.
(1) General.
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(i) Original type design information and criteria may or may not be available from the manufacturer. Availability of this information is dependent on whether the information is considered “public” (i.e., non-proprietary) or proprietary. It may be appropriate to reference the helicopter manufacturer’s “standard” features, placards, and markings in the applicant’s modification design data.
(ii) The EMS modification presented for approval usually contains equipment of one manufacturer’s model or design. T he type design of the modification will have features to power and restrain the equipment, maintain the rotorcraft systems integrity, and to otherwise protect the occupants. See paragraph b.(17), which refers to equipment substitution.
(iii) All equipment installations in the helicopter must be approved. EMS helicopters typically include operations in which large medical equipment is not installed in the helicopter but instead is carried on to the helicopter as needed such as isolettes, large medical equipment, and other medical items. This equipment is not included as part of the rotorcraft type design modification because it is not considered a permanent installation in the helicopter. However, carry-on medical equipment must be evaluated as to how it affects the safety of the helicopter and its occupants (including the occupant in the isolette) while being carried in the helicopter. This carry-on equipment (including the isolette) must be properly restrained so it is not a hazard during flight operations.
Consequently, the means to stow or store the medical carry-on items must be evaluated for the appropriate load factors relative to the helicopter so the means for stowage of the carry-on equipment does not fail. For instanc e, in the case of a carry-on isolette, the isolette is typically placed on top of an installed “mount” for the isolette. The “mount” is evaluated for carriage and restraining of the isolette. In some cases, an isolette may be completely self-contained and include other items, such as oxygen bottles required for the isolette occupant, which must also be evaluated for carriage of that equipment.
(2) Evacuation and Interior Arrangements. Access to the emergency exits or doors from any location in the cabin or compartment, access to and use of the exit or door opening means or release device, and the unobstructed area of the “standard” or type design exit are potential problems that should be addressed in the early design stage. Multi-litter arrangement s may be especially critical.
(i) The operation or use of devices for locking the position of swivel seats and for rapid installation and removal of litters (isolettes, etc.) should be labeled unless they are simple and obvious, and do not require exceptional effort. The design features of the device(s) and the seat or litter will influence the extent of information in any label necessary to ensure proper and safe installation for routine use and prompt evacuation when appropriate or necessary for the interior arrangement. The requirement for labels or markings (instructions, etc.) that applies to operation of seat or litter features, release devices, etc., is not relieved even if attendants are necessary for an evacuation as discussed in paragraph b.(2)(iii). Placards or instruction ca rds that contain evacuation procedures do not necessarily contain detailed procedures for individual seats, litters, Page MG 6 - 3
AC 29-2C, Chg 4 2/27/2014 and so forth. Release devices that ar e simple and obvious and do not require exceptional effort are recommended. For ex ample, a single central control for litter release would be preferred over multiple action release devices. However, seats and litters that require multiple actions to release or reposition may be acceptable if properly evaluated to determine that, in the event of an emergency landing, there is no obstruction or delay if rapid evacuation is necessary.
(ii) The passenger compartment or cabin should not be partitioned to impede access to the exits. A person seated in the compartment should have access to each exit in the compartment. All persons must be able or have provisions to rapidly clear (evacuate) the rotorcraft (see § 29.803(a)). A demonstrati on or a “walk-through” of appropriate evacuation procedures may be necessary to ensure the means and procedures are feasible and adequate.
(iii) When an evacuation demonstration is determined to be appropriate for compliance, 90 seconds should be used as the time interval for evacuation of the rotorcraft. Attendants and the flightcrew, trained in the evacuation procedures, may be used to remove the litter patients. It is preferable for the pati ent to remain in the litter;
however, the patient may be removed from the litter to facilitate rapid evacuation through the exit. The patients are not ambul atory during the demonstration. Evacuation procedures should be included if isolettes are part of the interior. The demonstration may be conducted in daylight with the dark of the night simulated and the rotorcraft in a normal attitude with the landing gear extended. For the pur pose of the demonstration, exits on one side (critical side) should be used. Exits on the opposite side are blocked and not accessible for the demonstration. This is representative of a rollover or exits blocked due to a fire.
(iv) Special evacuation procedures and trained attendants may not be required for simple and obvious means of evacuation for a single litter. Procedures may be prominently displayed in durable markings, placards, cards, and condensed or summarized in the emergency procedures section of the Rotorcraft Flight Manual (RFM) or an EMS configuration RFM supplement.
(v) If any medical attendants are required for evacuation, the attendants should be trained in these procedures and listed in the limitations section of the RFM. If attendants are not essential for safe rotorcraft operation or rapid evacuation, then an attendant is not a required “crewmember.”
(3) Restraint of Occupants and Equipment. The emergency landing conditions specified in § 29.561(b) dictate the design load conditions. See AC 29-2, sections 29.561 and 29.785 for further information.
(i) Whether seated or recumbent, the occupants must be protected from serious head injury as prescribed in § 29.785. Swivel seats and tilt litters may be used provided they are substantiated for the appropriate loads for the position selected for approval. Placards or markings may be us ed to ensure proper orientation for flight, Page MG 6 - 4
takeoff, or landing and emergency landing conditions. The seats and litters should be listed in the type design data for the configuration. See paragraph b.(17) for substitutions.
(ii) For recumbent occupants, harnesses, straps, a padded headboard, a diaphragm, or safety belts may be used if in compliance with the load requirements of § 29.561(b) and § 29.785(k). Ha rnesses or straps are recommended. When used, they should prevent the occupant from significant forward motion in order to reduce occupant injuries. Infants in isolettes should be similarly protected by padding and containment within the isolette and the isolette restrained for the load cases noted in this paragraph.
If the infant is strapped to a removable platform, there should be proper restraint of the platform and infant within the isolette for the load cases noted in this paragraph. Isolette materials are also subject to the flammability standards noted in paragraph b.(4). The litter(s) and isolette(s) should be listed in the type design data for the EMS configuration.
(iii) An isolette used for the transport of infants presents a special case, in that it may be included as part of an approved EMS configuration or it may be carried on the rotorcraft as needed for transport of infants. If the isolette is self-contained and is not part of an approved EMS type design, it may be considered a carry-on item and not part of the EMS type design. In t hese cases, there is typically a means to position the carryon isolette and properly restrain the isolette for transport as part of the EMS design configuration.
(A) When the isolette is carry-on equipment, the operator must ensure that the isolette does not create a safety risk or interfere with aircraft operations. AC 135-14, Emergency Medical Services/Helicopter (EMS/H), provides information and guidance to air ambulance and EMS/H operators for large carry-on medical equipment such as isolettes. AC 135-14 includes the provision that isolettes are to be restrained in an appropriate manner and evaluated for specific emergency landing load factors as required by earlier amendments of the rotorcraft regulatory requirements. Since publication of AC 135-14. the emergency landing load requirements have changed for rotorcraft. Consequently; t he load factors specified in that AC may not be appropriate for rotorcraft, depending on the rotorcraft certification basis amendment level of the airworthiness standards. The minimum load factors should be no less than those specified in the certification basis of the rotorcraft transporting the medical equipment, such as isolettes.
(B) A placard indicating that the isolette should be evaluated per the guidance contained in AC 135-14 and restrained to the emergency landing load factors for rotorcraft occupants per 14 CFR 29.561(b)(3) or the appropriate reference based on the certification basis of the rotorcraft, should be placed in close proximity to the isolette mount location.
(iv) Galleys, medical supplies, and equipment compartments or modules should be restrained and the individual compartments must also contain the contents for Page MG 6 - 5
AC 29-2C, Chg 4 2/27/2014 the conditions noted in paragraph b.(3) of this guidance. Durable placards, decals, or markings should be used where appropriate to limit the maximum weight of any compartment and the whole module. Compartment latches having sufficient strength and displacement or engagement should be used to contain the contents for the conditions noted in paragraph b.(3) of this guidance. If necessary, a static load test or analysis should be employed to ensure the container or compartment remains intact and the latch does not disengage for the most critical conditions. Loose or unrestrained contents in an individual compartment, in combination with similar compartments, should require a magnification factor with the design conditions. Prudent design and location of compartments having heavy, unrestrained (loose) equipment will mitigate the potential effects of landing impact loads.
(4) Flammability of Materials. Interior materials must meet the flammability standards appropriate for the rotorcraft type design in § 29.853.
(i) For rotorcraft certified prior to adoption of Amendment 29-17 (1978), the cabin materials must be at least flash resistant and wall, ceiling linings, the covering of all upholstery, floors, and furnishings must be at least flame resistant. AC 23–2, Flammability Tests, contains test information about flash and flame-resistant material.
(A) Flash-resistant material may be characterized as that not exceeding a 20-inch-per-minute (horizontal) burn rate. See AC 23-2, Flammability Tests, for further information.
(B) Flame-resistant material may be characterized as that not exceeding a 4-inch-per-minute (horizontal) burn rate.
(ii) For rotorcraft certified to Amendment 29-17 adopted in 1978, the materials must be self-extinguishing as specified in the standards. For example, transparencies must be self-extinguishing as prescribed in § 29.853(a)(2).
(iii) Additionally, for rotorcraft certified to standards of Amendment 29-23 (1984), cushions of each passenger seat must have a “fire blocking layer” as prescribed in § 29.853(b).
(iv) When the isolette is included in the EMS configuration approval, the isolette materials are subject to the flammability standards of § 29.853. The current standards require that all materials, including transparencies, fabric (e.g., padding, covers), straps, etc., be self-extinguishing for each compartment used by crew or passengers.
(v)The applicant is urged to use self-extinguishing materials regardless of the certification basis.
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(vi) For further information on materials, refer to AC 29-2, section 29.853.
AC 23-2 also contains information about flash-resistant and flame-resistant material tests.
(5) . The approved exits require signs and Exit Signs or Markings and External Markings markings (instructions) for prompt evacuation even in darkness. The rotorcraft type design contains the required data. The maintenance manual and the RFM should also contain this information. See AC 29-2, section 29.811 for more information. Alternates may be approved, which then become part of the applicant’s type design data. All U.S. transport roto rcraft presently in service should have an emergency interior lighting system to comply with § 29.811(f). (Refer to the certification basis of the rotorcraft.)
(6) Interior or “Medical” Lights. The view of the fli ghtcrew must be free from glare and reflections that could cause interference. Use of a night vision imaging system (NVIS) should be a consideration in this evaluation. Curtains t hat meet flammability standards may be used. Complete partition or separation of the crew and passenger compartment is not prudent. Means for vi sual and oral communication are usually necessary. Refer to AC 29-2, section 29.773, which concerns pilot visibility.
(7) Patient Interference. When passengers or patients are located in close proximity to the pilot and the primary flight controls of the rotorcraft, a guard or shield should be installed, or the patient should be restrained to prevent inadvertent or potential patient interference with safe operation of the rotorcraft. The guard may be a part of the rotorcraft interior features. In addition, prompt evacuation should be ensured if a guard is used.
(8) External Devices.
(i) Search lights, loud speakers, baggage pods, etc., may be installed on the underside of or elsewhere on the rotorcraft. The strength of the attachments must be substantiated for the flight and landing conditions. The light s and the reflection from the lights should not adversely affect pilot view or visibility. Use of NVIS should be a consideration in this evaluation.
(ii) The device or pod located on the underside of the rotorcraft should not contact a level landing surface after “limit landing load” deflection of the landing gear.
The gear should deflect without causing damage to the device. For example, if the limit landing load deflection is 8 inches, the device would need to have at least 8-inch clearance to avoid contact with the landing surface or have an equivalent feature of design. The physical characteristics of the rotorcraft design dictate the necessary clearance for landing gear deflection. In addition, the device should be designed and located on the rotorcraft to preclude penetration of the device into a critical area of the fuselage. For example, the device should be located to minimize the potential of penetration into a fuel line, fuel cell, primary control tube, or occupant seat for any reason.
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