2/27/2014 Change AC 29-2C

Page MG 6 - 1 Final and approved; this changed AC sec tion is included with AC 29-2C and will later be incorporated into the next published change or revision to AC 29-2C.

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 c onfigurations are usually unique interior arrangements that are subject to the appropriate airworthi ness standards, part 29 or its predecessor CAR part 7, to which the rotorcra ft 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 wit h 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 t he 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 comple te life support systems and two or more attendants or medical personnel may be submi tted for approval. These configurations

will be evaluated to the airworth iness standards appropriate to the rotorcraft certification

basis.

(ii) Transport category rotorcraft s hould comply with flightcrew and passenger safety standards, which will result in the need to reevaluate certain f eatures of the basic

certified rotorcraft related to the EMS a rrangement, such as doors and emergency exits, and occupant protection. Compliance wit h airworthiness standards results in an emergency interior lighting system, placards or markings for doors and exits, exit size, exit quantity and location, exit access, safe ty belts, and possibly shoulder harnesses or other restraint or passenger protection means to be retained as part of the rotorcraft’sAC 29-2C Change 2/27/2014

Page MG 6 - 2 basic type design. The features, plac ards, markings, and “emergency” systems required as a part of the rotorcraft’s bas ic type design, should be retained unless specific replacements or alternate designs are necessary for the EMS configuration to comply with airworthiness standards.

(2) Many EMS configurations of tr ansport 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 ot her complex medical equipment.

(v) Human infant incubator (isolette).

(vi) Curtains or other interior light shielding for the f lightcrew compartment.

(vii) External loud speakers and search lights.

(viii) Special internal and exte rnal communication radio equipment.

*(ix) Flight data monitoring system (FDMS).

*(x) Radio altimeter.

*(xi) Helicopter terrain aw areness and warning system (HTAWS).

*(3) All helicopter air ambulance servic e providers are requir ed to operate at all times under a part 135 subpart L certificat e. 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, O peration, 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.2/27/2014 Change AC 29-2C

Page MG 6 - 3 (1) General.

(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-pr oprietary) or proprietary. It may be appropriate to reference the helicopter manuf acturer’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 whic h 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 it ems. This equipment is not included as part of the rotorcraft type des ign 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 he licopter and its occupants (including the occupant in the isolette) while being carried in the he licopter. This carry-on equipment (including the isolette) must be properly restrained so it is not a hazard during flight operations. Consequently, the means to st ow or store the medical carry -on items must be evaluated for the appropriate load factor s 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 instal led “mount” for the isolette. The “mount” is evaluated for carriage and restraining of the isole tte. In some cases, an isolette may be completely self-contained and in clude 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 Arrangement s. Access to the emergency exits or doors from any location in the cabin or co mpartment, access to and use of the exit or door opening means or release device, and t he 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 fo r locking the position of swivel seats and for rapid installation and removal of litters (i solettes, etc.) should be labeled unless they are simple and obvious, and do not require exc eptional 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 installa tion for routine use and prompt evacuation when appropriate or necessary for the interi or 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 a ttendants are necessary for an evacuation asAC 29-2C Change 2/27/2014

Page MG 6 - 4 discussed in paragraph b.(2)(iii). Placards or instruction ca rds that contain evacuation procedures do not necessarily co ntain detailed procedures for individual seats, litters,

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 repositi on may be acceptable if properly evaluated to determine that, in the event of an emergency landi ng, there is no obstruction or delay if rapi d 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 (s ee § 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 demonstrati on is determined to be appropriate for compliance, 90 seconds should be used as t he 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 ar e part of the interior. The demonstration may be conducted in daylight with the dark of the night simula ted 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 us ed. 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 ev acuation for a single litter. Procedures may be prominently displayed in durable mark ings, placards, cards, and condensed or summarized in the emergency procedures secti on of the Rotorcraft Flight Manual (RFM) or an EMS configurat ion RFM supplement.

(v) If any medical attendants are required for evacuation, the attendants should be trained in these procedur es and listed in the limitations section of the RFM. If

attendants are not essential for safe rotorc raft operation or rapid evacuation, then an attendant is not a required “crewmember.”

(3) Restraint of Occupants and Equipm ent. The emergency landing conditions specified in § 29.561(b) dictate the des ign 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 used2/27/2014 Change AC 29-2C

Page MG 6 - 5 provided they are substantiated for the appr opriate loads for the position selected for approval. Placards or markings may be us ed to ensure proper orientation for flight, takeoff, or landing and emergency landing c onditions. The seats and litters should be listed in the type design data for the c onfiguration. 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 re commended. When used, they should prevent the occupant from significant forward motion in order to reduce occupant injuries. Infants in isolettes should be si milarly 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 platfo rm, there should be proper restraint of the platform and infant within the isolette for t he load cases noted in this paragraph. Isolette materials are also subject to the flammab ility 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 in terfere with aircraft operations. AC 135-14, Emergency Medical Services/Helicopter (EMS/H ), provides information and guidance to air ambulance and EMS/H operators for lar ge 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 specif ic emergency landing load factors as required by earlier amendments of the roto rcraft regulatory requi rements. Since publication of AC 135-14. the emergency landing load r equirements have changed for rotorcraft. Consequently; t he load factors specified in th at AC may not be appropriate for rotorcraft, depending on the ro torcraft certification basis amendment level of the

airworthiness standards. The minimum load factors should be no less than those specified in the certificati on basis of the rotorcraft trans porting 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 restrai ned 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, shoul d be placed in close proximity to the isolette

mount location.AC 29-2C Change 2/27/2014

Page MG 6 - 6 (iv) Galleys, medical supplies, and equipment compartments or modules should be restrained and the individual compar tments must also contain the contents for 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 m odule. 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 c ontainer or compartment remains intact and the latch does not disengage for the most cr itical conditions. Loose or unrestrained contents in an individual compartment, in combination with si milar compartments, should require a magnification factor with the design conditions. Prudent design and location of compartments having heavy, unr estrained (loose) equipm ent will mitigate the potential effects of landing impact loads.

(4) Flammability of Mate rials. Interior materials must meet the flammability standards appropriate for the roto rcraft 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 resi stant and wall, ceiling linings, the covering of all upholstery, floors, and fu rnishings 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 standar ds 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 configur ation approval, the isolette materials are subjec t to the flammability standards of § 29.853. The current standards require that all materials, incl uding transparencies, fabric (e.g., padding, covers), straps, etc., be self-extinguish ing for each compartment used by crew or

passengers.

(v)The applicant is urged to use self-extinguishing materials regardless of the

certification basis.2/27/2014 Change AC 29-2C

Page MG 6 - 7 (vi) For further information on material s, refer to AC 29-2, section 29.853.

AC 23-2 also contains information about flas h-resistant and flame -resistant material

tests.

(5) Exit Signs or Markings and Exter nal Markings. The approved exits require signs and markings (instructions) for prom pt evacuation even in darkness. The rotorcraft type design contains the requir ed 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 par t 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 wit h § 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 interferenc e. Use of a night vision imaging system (NVIS) should be a consideration in this eval uation. 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 pass engers or patients are located in close proximity to the pilot and the pr imary 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 operat ion 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 t he underside of the rotorcraft should not contact a level landing surfac e after “limit landing load” de flection of the landing gear. The gear should deflect without c ausing 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 su rface or have an equivalent feature of design. The physical characteristics of t he 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, prim ary control tube, or occupant seat for any

reason.AC 29-2C Change 2/27/2014

Page MG 6 - 8 (iii) A flight evaluation is necessary to determine the effects of the device on the rotorcraft flight characterist ics and on flight crew visibility . In addition, recent service history has shown that external equipment an d external fixture modifications 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 the same gross 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 V ne airspeeds.

(A) If required, the post modification V ne should be reduced so that the post modification longitudinal cyclic stick positi on is slightly aft of (or less than) the pre modification 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.

(B) In some cases, a control pos ition parameter other than longitudinal stick position may be critical. For example, a heavy 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 limitat ions other than V ne may need to be established, or reduced from pre modification limitations, to ensure pre-modification mast bending is not exceeded.

(9) Miscellaneous. Various paragraphs in this MG contain guidance for the standards cited in the reference list (par agraph c.(1)). These paragraphs should provide insight into designing an EMS configuration that w ould be acceptable under the

standards.

(10) Oxygen. EMS oxygen installations are supplied by either liquid or gaseous oxygen. Both types of systems are discussed in this paragraph.

(i) Liquid Oxygen.

(A) System General Description. Most liquid oxygen systems in use are installed in military aircraft and, as a result, much of this material is based on experience with these systems. A rotorc raft liquid oxygen system should be comprised of a liquid oxygen converter, tubing, fittings, quantit y gage, heat exchangers, and appropriate pressure and flow control components as shown in figures AC 29 MG 6-1 and AC 29 MG 6-2. The installation may prov ide for replenishing the liquid oxygen supply by use of a quick-removable converter or, in t he case of a fixed inst allation converter, by providing external access for connection to a portable service trailer. More complicated systems such as those with multiple conver ter assemblies are not discussed here since installation of those syst ems are not envisioned in ro torcraft at this time.2/27/2014 Change AC 29-2C

Page MG 6 - 9 (B) System Components. All components should be ai rcraft qualified and suitable for use in an EMS rotorcraft application.

(1) Liquid Oxygen Converter. A liquid oxygen converter assembly is a self-powered system for the storage of liqui d oxygen and for its conversion to gaseous oxygen when required. A princi pal part of the converter assembly is a vacuum insulated

container. Pressure relief valves shoul d be provided to allow the escape of gas generated when oxygen is not being expended in the supply line. Oxygen losses from a converter assembly vary from 5 to 20 per cent per 24 hours depending on the size of the container, its installation env ironment, and so forth. Ai rcraft qualified and approved

converters suitable for EMS rotorcraft use are ava ilable in either 5 or 50-liter capacities. Size selection should be determined by fl ow rate and duration requirements.

Performance characteristics of each converte r size are available from the manufacturer.

(2) Shutoff Valve Assembly. This valve must be accessible to a flightcrew member and be mount ed in the supply line on or as close as possible to the outlet of the converter. This valve provides for the confinement of the remaining supply of liquid oxygen to the converter in the event of an emergency. Since the system pressure is low, the use of an electrically actuated shutoff valve is satisfactory to accomplish this function. In some in stallations, where the evaporating coil is immediately adjacent to the converter, a flow fuse has been used to accomplish this function. Use of a flow fuse must be suppor ted by a system fault analysis and testing to

show maximum normal flow will not result in nuisance trips, and reliable trips will be provided for malfunction condition s resulting in excess flow.

(3) Filler Valve. Some designs combine this function with the build-up and vent valve assembly as shown in figure AC 29 MG 6-2.

(4) Build-up and Vent Valve Assemb ly. This valve is positioned in the “vent” position when the system is being filled with oxygen and in the “build-up position at other times. Some designs combine this function with the filler valve as shown in figure AC 29 MG 6-2.

(5) Pressure Build-up Coil Assembly and Pressure Closing Valve. With the build-up and vent valve in the “build -up” position gas that is formed is allowed to apply pressure to the liquid to provide adequate flow through the check valve to the evaporating coil assembly. A connection to a pressure relief valve is also provided.

(6) Evaporating Coil Assembly. This is provided to convert the liquid oxygen into a gaseous form. The evaporating coil assembly should be of sufficient capacity to maintain the design flow quant ity to the dispensing regulators at a temperature within +10 and - 20°F of cabin ambient tem perature. MIL-D-19326G

contains a discussion of installati on considerations for this unit.

(7) Vent Line. Gaseous oxyg en escapes through this line. At the conclusion of the fill operati on, liquid oxygen will flow over board in a steady stream fromAC 29-2C Change 2/27/2014

Page MG 6 - 10 this line to indicate the container is full of liquid oxygen. The vent line should be located

to drain overboard at the bottom of the roto rcraft fuselage. Flow from the overboard

vent should be directed so as not to creat e a hazard for personnel and not allow liquid oxygen to come in contact with the rotorcraft. The vent lines should be insulated to prevent frosting and sweating if they pass over equipment that will be harmed by water dripping from the lines, or drip pans should be installed under t he lines. There should be no hydrocarbon fills or drains, forward or above, in proximity to the vent outlet.

(8) Regulator. A regulator should be installed in the supply line

downstream from the heat exchanger. The regulator s hould reduce the liquid oxygen converter operating pressure to a supply pr essure of 50 pounds per square inch gauge (PSIG) to be compatible with the norma l operating pressure of medical oxygen equipment.

(9) Flow Control Valve. This valve provides a calibrated flow of gaseous oxygen from an operat ing supply of 50 ± 5 PSIG. A valve whose proof pressure is specified at 80 PSIG and has a burst pressure rating of 350 PSIG would be considered satisfactory.

(10) Check Valve. This va lve prevents gaseous oxygen in the supply system from backing up into the liquid oxyg en in the container and increasing the vaporization rate of the liquid oxygen by exposure to the gas. This valve is normally an integral part of the liquid oxygen converter assembly.

(11) Quantity Indicators. A quant ity indicator should be installed at the appropriate rotorcraft crew stat ion to permit monitoring of t he liquid oxygen supply. The

indicator when installed in the rotorcraft s hould indicate the amount of liquid oxygen in the converter. Adequate clearance should be provided for the indicator connectors so that they can be readily disconnected by se rvicing personnel. Provisions should be made for the storage of the ro torcraft connectors to the liquid oxygen converter when they are disconnected. Liquid oxygen quantity i ndicating equipment is available in three types: capacitance gauging, electro-mechani cal transducer indication, and differential pressure type indication.

(12) Pressure Relief Valves. Pr essure relief valves are provided to vent overboard through the overboard vent system any excess pr essures developing within the system.

(13) Lines. Lines should be ei ther solid tubing or flexible hoses. Examples of acceptable solid tubing are aluminum alloy conforming to AMS 4071 or corrosion resistant annealed steel (304) conf irming to MIL-T-8506. Flexible hoses should be used for rotorcraft system connections to removable converters and to other applications where relative movement may o ccur. Flexible hoses should be wire-braidcovered bellows or wire-braid- covered tetrafluoroethylene. Flexible hoses conforming to MS90457 or MS24548 are satisfactory. MS90457 hose is flexible to -297°F (-183°C), and MS24548 hose is flexible to -65°F (-54°C). Sy nthetic lines such as plastic, nylon, or2/27/2014 Change AC 29-2C

Page MG 6 - 11 rubber should not be used for lines subjected to continuous pressure, or for application

where the line will not be visible. Lines that are not visibl e are those that are located

behind liners or in the walls of the fuselage.

(14) Fittings. If in contac t, dissimilar metals should be suitably protected against electrolytic corrosion. Li ne assemblies should be terminated with “B” nuts or a similar manufactured terminating connection. Universa l adapters (AN 807) or friction nipples used in conj unction with hose clamps should be avoided in pressurized systems.

(15) Drain Valve. Systems t hat have permanently installed containers

should include a drain valve located to allow for complete draining of the liquid oxygen container. An acceptable drain valve would be one in accordance with MK-V-25962 that is suitably capped. A cap in a ccordance with AN 929- 5 with a permanently attached chain is a suitable cap.

(16) Low Pressure, Low Level Warning System. It is recommended that provisions be included in the system to alert the appropr iate aircraft crew member that the level of the oxygen supply has reached some low level. It is recommended that low level be actuated when less than 10 perc ent of the full container capacity is available. If low system pressure is also monitored, the low pressure valve selected should be such that any drop in supply line pr essure upon inhalation should not activate the low pressure warning function.

(C) Component Installation. The following are typical installation

considerations that should be addre ssed when designing the oxygen system.

(1) Location. The oxygen equipment, lines, and fittings should be located as remotely as practicable from sources of flammable fluids, high heat and electrical items, fuel, oil, hydraulic fluid, batteries, exhaust sta cks, manifolds, and so forth. Oxygen lines should not be grouped with lines carrying flammable fluids. If possible, converters should not be in line with the plane of rotation of a turbine. System components should not be installed in an env ironment that will exceed the temperature limit of the component, and no par t of the system should be in stalled in an area that will exceed 350°F (176°C). To minimize loss due to heat, the liquid oxygen converter should not be located near equipment that dissipates a high quantity of heat.

(2) Converter Mounting. The oxygen container should be readily accessible to servicing personnel. If the cont ainer is not removable for servicing, the

filler should be external to the aircraft with adequate contaminat ion protection. Mounting provisions for the converter and plumbing to the evaporating coil assembly should include a drain pan with an overboard drain.

(3) Flexible Hoses. Hoses s hould be of sufficient length to provide unstressed connections and be protected against chafing on surfaces or objects that may damage the wire covering. The bend radius imposed on the hoses duringAC 29-2C Change 2/27/2014

Page MG 6 - 12 installation and replacement should not be le ss than the minimum established by the hose specifications.

(4) Lubricants. No lubricant s should be used on liquid oxygen pipe fittings. MIL-T-27730 Teflon tape may be us ed on male pipe fittings when required. Teflon tape should not be used on flared tube fi ttings, straight threads, coupling sleeves,

or on the outer side of tube flares. None of the tape should be al lowed to enter the inside of a fitting. Krytox fluorinated gr ease by E.I. Dupont De Nemours and Company, or an equivalent, may be used sparingly on seals.

(5) Tubing Routing and Mounting. There should be at least 2 inches of clearance between the oxygen system and flexible moving parts of the rotorcraft. There

should be at least a 1⁄2-inch clearance between the oxygen system and rigid parts of the rotorcraft. The oxygen system tubing, fittings, and equipment should be separated at

least 6 inches from all electrical wiri ng, heat conduits, and heat emitting equipment in

the rotorcraft. In sulation should be provided on adjacent hot ducts, conduits, or equipment to prevent heating of the oxygen system. In rout ing the tubing, the general policy should be to keep total length to a mini mum. Allow for expansion, contraction, vibration, and component r eplacement. All tubing should be mounted to prevent vibration and chafing. This should be acco mplished by the proper use of rubberized or cushion clips installed at 24-inch interval s (copper) or 36-inch intervals (aluminum) and as close to the bends as possible. The t ubing, where passing through or supported by the rotorcraft structure, should have adequate protection against chafing by the use of flexible grommets or clips. The tubing shou ld not strike against t he rotorcraft structure during vibration and shock encountered dur ing normal use of the rotorcraft.

(6) System Marking. The ro torcraft should be permanently and legibly marked, as applicable, in the locations spec ified below (a minimu m letter height of 1⁄4 - inch is recommended):

(i) Adjacent to the overboard vent opening:

CAUTION
LIQUID OXYGEN VENT

(ii) On outside surface of filler box cover plate:

LIQUID OXYGEN (BREATHING) FILL ACCESS

(iii) On underside surf ace of filler box cover plate:

CAUTION - KEEP CLEAN, DRY, AND FREE FROM OILS

(iv) In prominent place when filler box is open, preferably near liquid oxygen drain valve:2/27/2014 Change AC 29-2C

Page MG 6 - 13 DO NOT OPEN DRAIN VALVE UNTIL DRAIN HOSE

AND DRAIN TANK ARE CONNECTED

(v) Other placards, such as one at the converter cautioning about the presence of liquid oxyg en, may also be appropriate.

(7) Other installation criteria are given in Chapter 6 of AC 43.13-2, Acceptable Methods, Techniques, and Practi ces-Aircraft Alterations, and should be given consideration.

(D) Precautions. The referenced Society of Automotive Engineers (SAE) report contains precautions peculiar to a liq uid oxygen installation, and this material

should be reviewed. It should also be emphasized that liquid oxygen equipment and the aircraft being serviced must be electric ally grounded during servicing to prevent an

accumulation of static elec tricity and discharge. The fo llowing considerations are included for special emphasis:

(1) System Cleanliness. The completed installation should be free of oil, grease, fuels, water, dust, dirt, objecti onable odors, or any other foreign matter, both internally and externally prior to introducing oxygen in the system.

(2) Closures. Lines that need to be disconnected during rotorcraft maintenance checks or overhaul, due to t he location of the converter within the rotorcraft, should be capped to prevent material s that are incompatible with oxygen from entering the system when the system integrity is broken. C aps that introduce moisture and tapes that leave adhesive deposits should not be used for these purposes. All openings of lines and fittings should be kept securely capped until closed within the

installation.

(3) Degreasing. All co mponents of the oxy gen system should be procured for oxygen service use in an “oxyg en clean” condition. Pa rts of the oxygen system, such as tubing, not specifically covered by cleaning procedures should be degreased using a vapor phase trichloroetha ne degreaser. Ultrasonics may be used in conjunction with vapor phase degreasing for the cleaning of components.

(4) Purging. The system should be purged with hot, dry 99.5 percent pure oxygen gas in accordance with t he manufacturers recommendations after:

(i) Initial assembly of the oxygen system; and

(ii) After system closur e whenever the oxygen system pressures have been depleted to zero, or the system ha s been left open to atmospheric conditions for a period of time or is opened for repairs.

(5) Maintenance and Replacemen t. All parts of the oxygen system should be installed to permit ready removal and replacement without the use of specialAC 29-2C Change 2/27/2014

Page MG 6 - 14 tools. All tubing connections and fittings should be readily accessible for leak testing with a leak test compound formulated for l eak testing oxygen systems and for tightening of fittings without removing surrounding parts.

(ii) Gaseous Oxygen.

(A) General. This guidance is intended to supplement the existing guidance in AC 43.13-2, Chapter 6. If there are any differenc es within the two ACs, this guidance prevails since it pertains s pecifically to part 29 requirements.

(B) System Components.

(1) High Pressure Cylinders. Many installations utilize hospital type cylinders rather than aviation type cylinders. A concern with the hospital type cylinders is the yoke and the hard plastic washer that is commonly used with these cylinders. It is very difficult to properly attach these yokes since the rotorcra ft provides a high vibration environment and no positive lock is provided. Leaks are a continuous problem with this configuration. Yokes are ava ilable for these bottles that provide for a positive lock. Improved washers that provi de for a good elastomeric seal and include a metal ring to limit crushing the washer are al so available. If the hospita l type bottles are to be used, only the modified yokes and improved seal s should be considered for future installations. The preferred cylinder is the aviation type cy linder with the integral shutoff valve and regulator. All cy linders should be DOT approved.

(2) Lines.

(i) General. Any lines that pass through potential fire zones should

be stainless steel.

(ii) High Pressure. Use of high pressure lines may be necessitated by the use of a pressure regul ator that is remote from th e cylinder. The intent is to locate the regulator as close as physically po ssible to the cylinder, and to minimize the use of fittings. Lines of 6-inch lengths are encouraged with 18-inch lengths being the

maximum in unusual circumstances. Lines made of stainless steel are recommended.

(iii) Low Pressure. Although lines may only be subjected to low pressures, if they are loca ted behind upholstery or for an y reason are not 100 percent visible during normal operation, they should be solid metal lines or high pressure flexible lines that conform to SAE 100R14A specific ations for stainless braided hoses. Other oxygen lines, so called “green lines,” s hould only be used in locations that are 100 percent visible during normal operation. Th is would restrict their use to the run

between the mask and the bulkhead disconnect in the aircraft cabin. Synthetic lines such as plastic, nylon, or rubber ar e not recommended for applications that will be exposed to continuous pressure (i.e., as opposed to pressurized when needed). These

materials can cold flow.2/27/2014 Change AC 29-2C

Page MG 6 - 15 (3) Fittings.

(i) High Pressure. Inter cylinder connections are made with regular flared or flareless tube fittings with stainle ss steel. Usually fittings are of the same

material as the lines. Mild steel or alumi num alloy fittings with stainless steel lines are discouraged. Titanium fittings should nev er be used because of a possible chemical reaction and resulting fire.

(ii) Low Pressure. Fittings fo r metallic low pressure lines are flared or flareless, similar to high pressure li nes. Line assemblies should be terminated with

“B” nuts in a similar manner to a manufactured terminating connection. Universal adapters (AN 807) or friction nipples used in conjunction with hos e clamps are not accepted for use in pressurized oxygen systems.

(4) Shut-off Valve. Each system should contain a shutoff valve that is located as close as practical to the high pressure cylinder(s), and it should be assessable to a flightcrew me mber. High pressure cylinder s should use slow opening and closing system shut-off valves. Where the regulator is part of the cylinder, and low pressure oxygen is controlled, the emphasis in slow acting valves is not as significant, and use of a flow fuse may be possible. Us e of a flow fuse must be supported by a system fault analysis and testing to show ma ximum normal flow will not result in nuisance trips, and reliable trips will be provided for malfunction conditions resulting in

excess flow.

(5) Regulators. The regulator should be mounted as close as possible to the cylinders (see paragraph b.(10)(i)(B)(8) of this guidance). If non-aviation qualified regulators are considered, their service history should be reviewed and careful consideration given to the manufacturer’s env ironmental qualification. Radio Technical

Commission for Aeronautics Document D0 -160 is a recognized and accepted standard

for environmental considerations. As a mi nimum, consideration should be given to operation during altitude, temper ature, and vibration extremes.

(6) Placards. Appropriate placards should be provided with the installed system. Emphasis should be placed on any precautions that are appropriate during filling of the system and so forth.

(7) Filler Connections. When a filler connection is provided, it is recommended it be located outside the fuselage skin or isolated in a manner that would prevent leaking oxygen from entering the ro torcraft. Careful evaluation should also be made of any nearby sources of fuel, oil, or hydraulic fluid under normal or malfunction

conditions. Each filler connection should be placarded. In addition, any valves (on aircraft or ground servicing equipment) asso ciated with high pressure should be slow acting.

(C) “Provisions Only” Considerat ions. In some instances systems are approved that only include provisions for a supply system consisting of the highAC 29-2C Change 2/27/2014

Page MG 6 - 16 pressure cylinders, regulators, and their associated lines and fittings. In these instances, a placard should be provided that refers to a supply system that is considered satisfactory for the remainder of the insta llation. An example of an acceptable placard for this situation is:

Oxygen Supply System must be in accordance with the requirements given in STC SH _________. Deviations to the configuration specified must be evaluated and approved by the Manager (include reference to the appropriate FAA ACO).

(11) Medical Communication Equipment. This equipment is provided to allow for

communication between the roto rcraft and ground medical personnel. It includes voice communication and may also include teleme try equipment for the transmission of graphic data. It should be demonstrated that th is equipment functions properly and the range at which this determination was made reco rded in the project file. The functional demonstration should include a 360° turn (c lockwise and counterclockwise) to ensure no significant sections of signal blanking ex ist. The remainder of the emphasis on this equipment should be to ensure t hat operation of this equipm ent does not interfere with normal operation of any rotorc raft systems whose installation is required for safe operation of the rotorcraft.

(12) Cabin Lighting. EMS interiors no rmally include higher intensity cabin lighting

than other interiors. This lighting capability should be care fully evaluated to ensure it does not interfere with operation of the rotorcraft. In some installations a special curtain is required to separate the cockpit from any interference by the lighting. The FAA project file should document the approach of how this eval uation was conducted. See paragraph b.(6) for other cu rtain considerations.

*(13) FDMS. If required under an oper ating regulation, an FDMS (not to be confused with a flight data recorder (FDR) certificated under § 29.1459) may be comprised of a system or combination of systems that record a helicopter’s flight performance and operational data. An FDR certificated under § 29.1459 and the appropriate operating rules woul d be acceptable to meet this requirement; however, an FDMS would not be adequate to meet the § 29.1459 requirement for an FDR. The FDMS should be capable of capturing digita l or analog raw data, images, cockpit voice or ambient audio recordings, or any combin ations thereof, according to a broadly defined set of parameters including informa tion pertaining to the aircraft’s state, condition, and system performance. This data can be used to perform post flight analysis and provide critical information to in vestigators in the event of an incident or accident as well as to promote operational safety. When used in conjunction with an FAA-approved flight operations quality assurance (FOQA) program, part 135 certificate holders would be required to collect flight performance and operational data that characterizes the state of the helicopter and its subsystems that the certificate holder determines is pertinent to its safety pr ogram. FDMS data should be recorded and stored on digital media, and when selecting a location to install the hardware device used for storing the data, consideration should be given to the potential for survival in2/27/2014 Change AC 29-2C

Page MG 6 - 17 the event of a crash. The system should rece ive electrical power from the helicopter’s bus that provides the maximum reliability without jeopardizing service to essential or emergency loads, and capable of being operated c ontinuously from the time power is applied to the aircraft until power is removed from the aircraft.

(i) Safety. The FDMS equipment s hould not, under normal or fault conditions, adversely affect the airworthiness of the syste ms to which it is interfaced or of other aircraft systems. The equipment should be in stalled in accordance with all applicable safety regulations. The equipment should be tested under the sta ndards of RTCA DO160F, "Environmental Conditi ons and Test Procedures for Airborne Equipment," or subsequent issue. The European Organizati on of Civil Aviation Equipment (EUROCAE) specification ED-14 may be used in lieu of RT CA DO-160. Additional crashworthiness testing may be conducted according to EU ROCAE specification ED-155, “Minimum Operational Performance Specification for Lightweight Flight Re cording Systems.” Equipment testing should be conducted to the categories most applic able to the aircraft type, and the location of the equipment to be installed. The equi pment manufacturer typically defines the test class within each envi ronmental category. The objective of this level of testing is to ensure that the equipment does not present a hazard to the aircraft, and can survive and continue to operate under t he environmental conditions to which it will be subjected throughout its life. Specific testing ma y be required to demonstrate that the equipment performs its int ended function when operated over the full

environmental conditions to which it has been declared to comply. Consideration should be given to the extremes at which it may be subjected dur ing an incident or accident. These tests can be undertaken during the specified RTCA DO-160F (or later revision) tests or separately. Analysis may be substituted for a test where its use can be shown to produce equivalent evidence of compliance. The system should be capable of recording up to 2 hours of image or acoustical data and 6-hours of aircraft parameter data. T he applicant determines and maintain s the data stream format and parameter documentation, incl uding which parameters are recorded, how often the parameters are recorded, the bit resolution of each parameter, the operational range of each parameter, and the conversion algorithm fr om decimal units to engineering units. The Design Assurance Level (DAL) for an FDMS that is required by an operating regulation is DAL “D.” RTCA DO-178B (or la ter revision) provides acceptable software development standards, which in this case would be for DAL “D” software. RTCA DO-254 (or later revision) provides acc eptable airborne electronic hardware (AEH) development standards, which in this case would be for DAL “D” AEH.

Note: The duration between data downloads fo r the promotion of operational safety within a FOQA program is directly correlat ed to the recording capabilities of the system installed.

(ii) Recording. The FDMS shoul d be capable of capturing and recording any combination of the following parameters in order to moni tor the aircraft’s state, condition, and system performance:

 Positioning system time.AC 29-2C Change 2/27/2014

Page MG 6 - 18  Positioning system latitude.

 Positioning system longitude.

 Positioning system altitude.

 Positioning system error.

 Altitude.

 Heading.

 Pitch attitude.

 Pitch rate.

 Roll attitude.

 Roll rate.

 Yaw rate.

 Air speed.

 Ground speed.

 Ambient acoustic data.

 Engine parameters.

 Main rotor revolutions per minute.

 Transmission ambient audio.

 Any other parameters deemed ap propriate by the operator.

Notes: Parameters may be recorded directly or deduced from recorded data from the FDMS. Additional guidance on parameters can be found in EUROCAE specification ED-155.

Recording individual pilots, usi ng hot microphones, on separate pilot audio channels can provide useful information in the investigation of incidents and

accidents.

(iii) Maintenance. The maintenance requirements to ensure the serviceability

and continued airworthiness of the FDMS are typically established by the equipment

manufacturer and installer. These maintenanc e instructions should be included in the applicable helicopter model instruct ion for continued airworthiness.

*(14) Radio Altimeter (R AD ALT). RAD ALTs insta llation is required. Its information display must be in the pilot’s prim ary field of view in all helicopters operating under a part 135 certificate. The mini mum performance requirements for an FAA approved RAD ALT system c an be found in TSO-C87.

(15) Other EMS Equipm ent. These items of equipm ent installed for the EMS mission are considered optional equipment and should be operated to ensure they function properly. This evaluation woul d normally be done by so meone knowledgeable about the particular type of equipment, since correct operation of the equipment is

essential to a valid determination that t he required rotorcraft sys tems are not being

interfered with. This includes all removabl e pieces of medical equipment that are used for patient care. The primary purpose of the evaluation of this equipment is to emphasize the possibility of any interfer ence between operation of the EMS equipment2/27/2014 Change AC 29-2C

Page MG 6 - 19 and the systems whose installation is required for safe operation of the aircraft, the adequacy of the installation provisions, and assu rance that failure m odes will not result

in a hazardous condition for the rotorcraft.

(16) Miscellaneous. The following areas are not peculiar to EMS installations; however, their significance is enhanced by the complexity of an EMS installation.

(i) Compatibility. M any EMS installations are a co llection of several STCs and may also include some FAA field approvals. Fo r this situation, it should be shown that the overall installation provides for safe operat ion of the aircraft. Operation of a search light, if included, should be addressed since in using this system it can be difficult to keep light from interfering with the pilot view.

(ii) Electrical Load Analysis. An el ectrical load analysis should be conducted, and additional guidance is available in AC 29 -2 MG 1. If the analysis indicates the generator(s) can be overloaded, appropriate m easures should be taken to account for the problem. In some instances (e.g., in a visual flight rules (VFR) approved rotorcraft), a placard that specifies cert ain operating limitations may be satisfactory, while in other instances (e.g., in an instrument flight ru les (IFR) approved rotorcraft), an electrical interlock may be in order. In general, if t he amount of overload is relatively small and the rotorcraft is not an IFR-approved rotorc raft, the placard solution will probably be satisfactory, whereas if the amount of possibl e overload is significant, it is more likely that an interlock scheme will be necessary.

(iii) Aircraft Grounding. It should be emphasized in an appropriate place in the STC data (e.g., RFM, maintenance info rmation) that any time the EMS systems are being operated or serviced (e.g., oxygen) on the ground, the rotorcraft itself must be grounded.

(iv) Electrical Outlets. All electrical outlets provided in the cabin should be the three-prong grounded type. When not in use, these outlets should be suitably protected against the entry of fluids.

(v) Placards. All medical outlets (e.g., air, oxygen, vacuum) should be placarded. Electrical power outlets should be placarded for type of voltage and amperage capacity. A placard stating “No Smoking When Oxygen Is In Use” should be included. Other placards would include information appropr iate to the oxygen system, operation of special controls, etc.

(vi) Equipment in Cargo and Bagg age Compartments. When components are added to the compartment, revisions should be made to protect t he system components due to shifting cargo. In addition, w hen oxygen components ar e installed, the compartment should be placarded against the storage of oil or hydrocarbons. A smoke detector is recommended for a compartment if oxygen cylinders are installed in a closed, non-accessible compartm ent. Also, the compartment weight limitations placardAC 29-2C Change 2/27/2014

Page MG 6 - 20 should be changed. AC 29-2, section 29.787 pertains to cargo and baggage
compartments.

(vii) Safety Assessment. When inst alling any new equipm ent or modifying existing equipment, a safety assessment must be made to assure the FAA that all possible failure conditions that could o ccur from these changes have been adequately addressed to show compliance to the regulations.

(17) Equipment Substitution. The EMS modification that is presented for approval will contain specific items of equi pment, and the approval will make reference to this equipment. If other equipment (e .g. new model, manufac turer) is to be substituted, then an evaluation should be ma de to ensure the substitute equipment is also satisfactory. This evaluation would no rmally consist of comparing the attachment means, design features, failure modes, specif ications, and operation of the two units. The purpose of the evaluation is to ensur e there are no differ ences that have an

adverse effect on the airworthin ess of the installation. Ot her differences would not be considered significant. A specific seat and litter design is approved as a part of the EMS configuration. Substitutions may be approved in accordance with the standards.

c. Related Regulations and References.

(1) Regulatory Sections. 14 CF R 29.337, 29.471, 29.561, 29.773, 29.783, 29.785, 29.803, 29.805, 29.809, 29.811, 29.813, 29.815, 29.831, 29.853, 29.1301, 29.1309, 29.1353, 29.1357, 29. 1411, 29.1431, 29.1557(d), 29.1583(d), 29.1585, 29.1589, part 91, and part 135.

(2) Other References Refer to the current version of each document.

(i) Helicopter Association Inter national, Emergency Medical Services

Recommended Guidelines.

(ii) National Highway Traffic Safety Administration, Air Ambulance Guidelines.

(iii) AC 23-2, Flammability Tests.

(iv) AC 43.13-2, Acceptable Met hods, Techniques, and Practices-Aircraft

Alterations.

(v) AC 135-14, Emergency Medica l Services/Helicopter (EMS/H).

(vi) Oxygen Equipment for Aircra ft, Society of Automotive Engineers Aerospace Information Report No. 825.

(vii) MIL-D-19326G, Design and Installa tion of Liquid Oxygen Systems in Aircraft, General Specification for Military Specification.2/27/2014 Change AC 29-2C

Page MG 6 - 21 FIGURE AC 29.MG 6-1 TYPI CAL LIQUID OXYGEN SYSTEMAC 29-2C Change 2/27/2014

Page MG 6 - 22 FIGURE AC 29.MG 6-2 TYPICAL L IQUID OXYGEN SYSTEM - USING

COMBINATION VALVE