2/27/2014 Change AC 27-1B

Page MG 6 - 1 Final and approved; this changed AC sec tion is included with AC 27-1B and will later be incorporated into the next published change or revision to AC 27-1B.

CHAPTER 3

AIRWORTHINESS STANDARDS

NORMAL CATEGORY ROTORCRAFT

MISCELLANEOUS GUIDANCE (MG)

AC 27 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 27 or its predecessor CAR part 6, 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 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 roto rcraft 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) Normal category rotorcraft sh ould 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 with ai rworthiness standards results in placards or markings for doors and exits, exit size, ex it 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. These features, includingAC 27-1B Change 2/27/2014

Page MG 6 - 2 any placards and markings required as part of the rotorcraft’s basic 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 norma l rotorcraft are equipped with the following:

(i) Attendant and medical personnel seats, which may swivel.

(ii) Multiple litters, some of which 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 li ght shielding for the flightcrew station.

(vii) External loud speakers and search lights.

(viii) Special internal (intercom) a nd external 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 operation 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 27-1 MG 18.

b. Procedures.

(1) General.2/27/2014 Change AC 27-1B

Page MG 6 - 3 (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 equipm ent is not installed in the helicopter but instead is carried onto t he 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 such that the means for stowage of the carry-on equipment does not fail. For instance, in the case of a carry-on isolette, the isolette is typically placed on t op 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 a nd 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 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 the unobstructed area of an exit are potential problems that should be addressed in the early design stage. Multi-litter arrangements may be especially critical fo r normal category rotorcraft due to their limited space.

(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 27-1B 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 s hould not be partitioned to impede access to exits. Exits and doors should be readily accessible. A door or exit is required on

each side of the rotorcraft. A demonstrat ion or a “walk-thr ough” of appropriate evacuation procedures may be necessary to ensure the means and procedures are feasible and adequate. Rotorcraft with read ily accessible exits, using simple and obvious means and procedures for an evacuati on, may not require written procedures

or a demonstration. Placards and durable ma rkings, if necessary, may be sufficient to complement the exit markings and in structions required by the standards.

(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 ev acuation 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 demonstr ation. 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.

(3) Restraint of Occupants and Equipm ent. The emergency landing conditions specified in § 27.561(b) dictate the des ign load conditions. See AC 27-1,

sections 27.561 and 27.785 for further information.

(i) Whether seated or recumbent, the occupants must be protected from serious head injury as prescribed in § 27.785. Swivel seats and tilt litters may be used provided they are substantiat ed for the appropriate loads for the positions selected for approval. Placards or markings may be us ed to ensure proper orientation for flight, takeoff and landing, and emergency landing condi tions. 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 § 27.561(b).and § 27.785(k). Har nesses or straps are reco mmended. When used, they2/27/2014 Change AC 27-1B

Page MG 6 - 5 should prevent the occupant from significant fo rward 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 EMS type design, it may be cons idered a carry-on item and not part of the EMS type design. In these ca ses, there is typically a means to position the carry-on isolette and properly restrain the isole tte for transport as par t 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 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 some rotorcraft, depending on the rotorcraft certificati on basis amendment level of

the airworthiness standards. The minimu m 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 27.561(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.

(iv) Galleys, medical supplies, and equipment compartments or modules

should be restrained and the individual com partments should 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 modul e. Compartment latches having sufficient strength and displacement or engagement should be us ed 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 unrestrainedAC 27-1B Change 2/27/2014

Page MG 6 - 6 contents in an individual compartment, in combination with si milar compartments, should use a magnification fa ctor with the design cond itions. 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 Materials.

(i) Interior materials must meet the flammability standards in § 27.853, appropriate to the type design. The standard presently requi res compartment materials

to be at least flame resistan t. The wall and ceiling lining s, coverings of upholstery, floors, and furnishings must be at least flame resistant.

(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.

(C) Self-extinguishing materials that can meet the transport rotorcraft standards of § 29.853 of Amendment 29-17 are recommended for use in normal category rotorcraft.

(ii) When the isolette is include d in the EMS config uration approval, the isolette materials are subjec t to the flammability standards of § 27.853. The current standards require that all materials, incl uding transparencies, fabric (e.g., padding, covers), straps, etc., be flame-resistant for each compartment used by the crew or passengers. AC 23-2 also contains test information about flas h and flame-resistant

material.

(5) Exit Signs or Markings and Exter nal Markings. Door s and exits must have signs and markings (instructions) for prom pt evacuation even in darkness. An emergency light system is not required by part 27. Refe r to the RFM or maintenance manual for standard placards, dec als, stencils, etc. Alternates may be approved as a part of the interior type design.

(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 evaluat ion. Curtains that meet the flammability standards (flame resistant) may be used. Complete partitioning or separation of the flightcrew and passenger area is not prudent. Means for vis ual and oral communication are usually necessary. Refer to AC 27-1 sect ion 27.773, 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 or2/27/2014 Change AC 27-1B

Page MG 6 - 7 potential patient interference with safe operati on 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 proven for the flight and landing conditions. The lights 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” def lection of the landing gear. That is, the landing gear should deflect under limit load without causing damage to the device. For example, if the gear limit l anding load deflection is 8 inches, the device would need to have at least an 8-inch gr ound clearance to avoid contact with the landing surface.

(iii) The physical characteristics of the rotorcraft landing gear design dictate the necessary clearance. The type design owner has this design information. A conservative deflection value may be chosen in place of obtaining design information. (The limit landing descent velocity specified in § 27.725(a) ranges fr om 6.5 to 8.3 feet per second.)

(iv) The device should also be des igned and located to preclude penetration into a critical area of the fuselage such as fuel cell, fuel line, primary control tube, or occupant seat in the event of higher landing impact velocities.

(v) 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 sideAC 27-1B Change 2/27/2014

Page MG 6 - 8 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. Several paragraphs in this MG contain guidance for the standards cited in the Regulatory Sections reference list (paragraph c.(1)). These paragraphs should provide insight into desig ning an EMS configuration that would 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 27 MG 6-1 and AC 27 MG 6-2. The installation may prov ide for replenishing the liquid oxygen supply by use of a quick-removable converter or, in the case of a fixed insta llation 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.

(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. Airc raft qualified and approved

converters suitable for EMS rotorcraft use are av ailable 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 to2/27/2014 Change AC 27-1B

Page MG 6 - 9 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 27 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 27 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 from

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.AC 27-1B Change 2/27/2014

Page MG 6 - 10 (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, or 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 that2/27/2014 Change AC 27-1B

Page MG 6 - 11 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 during 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 wiring, 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 preventAC 27-1B Change 2/27/2014

Page MG 6 - 12 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 s pecified below (a minimum 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:

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:2/27/2014 Change AC 27-1B

Page MG 6 - 13 (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. Caps 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 special 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 27 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 atta ch these yokes since the rotorc raft provides a high vibration environment and no positive lock is provided. Leaks are a continuous problem with thisAC 27-1B Change 2/27/2014

Page MG 6 - 14 configuration. Yokes are ava ilable for these bottles that provide for a positive lock. Improved washers that provide for a good elastometric 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 100R 14A specifications for stainl ess 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.

(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 ho se 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 opening2/27/2014 Change AC 27-1B

Page MG 6 - 15 and closing system shut-off valves. Where the regulator is part of the cylinder, and low pressure oxygen is controlled, the emphasis on 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 maximu m flow will not result in nuisance trips, and reliable trips will be provided for malfuncti on 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, durable placards should be provided with the installed system. Em phasis 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 roto rcraft. Careful evalua tion 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 valve (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 high 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 exis t. The remainder of the emphasis on this equipment should be to ensure t hat operation of this equipm ent does not interfere withAC 27-1B Change 2/27/2014

Page MG 6 - 16 normal operation of any rotorc raft systems whose installation is required for safe operation of the rotorcraft.

(12) Cabin Lighting. EMS interiors norma lly 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 so me installations, a special curtain is required to separate the cockpit fr om any interference by the lighting. The FAA approved data should document the a pproach of how this evaluation was conducted. See paragraph b.(6) for other curtain considerations.

*(13) FDMS. If required under an oper ating regulation, an FDMS (not to be confused with a flight data recorder (FDR) certificated under § 27.1459) may be comprised of a system or combination of systems that record a helicopter’s flight performance and operational data. An FDR certificated under § 27.1459 and the appropriate operating rules woul d be acceptable to meet this requirement; however, an FDMS would not be adequate to meet the § 27.1459 requirement for an FDR. The FDMS should record digital or analog raw dat a, images, cockpit voic e or ambient audio recordings, or any combinations thereo f, according to a broadly defined set of parameters including informati on pertaining to the aircraft’ s state, condition, and system performance. This data can be used to perfo rm post flight analysis and provide critical information to investigators 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 wo uld be required to collect flight performance and operational dat a that characterizes the state of the helicopter and its subsystems that the certificate holder dete rmines is pertinent to its safety program. FDMS data should be re corded and stored on digital media, and when selecting a location to install the hardw are device used for storing the data, consideration should be given to the potential for survival in the event of a crash. The system should receive electrical power from the helicopter’s bus that provides the maximum reliability without jeopardizing serv ice to essential or emergency loads, and capable of being operated continuously 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 shoul d be tested under the st andards of RTCA DO-160F, "Environmental Condit ions and Test Procedures for Airborne Equipment," or subsequent issue. The European Or ganization for Civil Aviation Equipment (EUROCAE) specification ED -14 may be used in lieu of RTCA DO-160. Additional crashworthiness testing may be conducted according to EUROCAE specification ED-155, “Minimum Operational Performanc e Specification for Lightweight Flight Recording Systems.” Equipm ent testing should be conducted to the categories most applicable to the aircraft type, and the location of the equipment to be installed. The equipment manufacturer typically defines the test class within each environmental category. The objective of this level of te sting is to ensure that the equipment does not2/27/2014 Change AC 27-1B

Page MG 6 - 17 present a hazard to the aircraft, and c an survive and continue to operate under the environmental conditions to which it will be subj ected throughout its life. Specific testing may be required to demonstrat e that the equipment performs its intended function when operated over the full environmen tal conditions to which it has been declared to comply. Consideration should be given to the extremes at which it may be subjected during an

incident or accident. These tests can be undertaken during the specified RTCA DO160F (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. The applicant determines and maintains the data stream format and parameter documentat ion, including which para meters are recorded, how often the parameters are recorded, the bit resolution of each para meter, the operational range of each parameter, and the conversion algorithm from 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 later revision) provides acceptable software developmen t standards, which in this case would be for DAL “D” software. RTCA DO-254 (or later revision) provides acceptabl e airborne electronic hardware (AEH) development sta ndards, 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 should 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.

 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.AC 27-1B Change 2/27/2014

Page MG 6 - 18  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, using 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 instructi ons 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 removable pieces of medical equi pment that are used for patient care. The primary purpose of the evaluation of th is equipment is to emphasize the possibility of any interfer ence between operation of the EMS equipment 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 27 -1 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 other2/27/2014 Change AC 27-1B

Page MG 6 - 19 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, and so forth.

(vi) Equipment in Cargo and Bagg age Compartments. When components are added to the baggage compartments, provisions should be made to protect the system components due to shifting cargo. In additi on, when oxygen components are installed, the compartment should be placarded against t he 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 cargo weight limitations placard should be changed. AC 27-1, section 27.787 per tains 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, manuf acturer) 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. Specific seats and litters are generally approved as a part of the EMS configuration. Substitution may be approved in accordance with the standards.

c. Related Regulations and References.AC 27-1B Change 2/27/2014

Page MG 6 - 20 (1) Regulatory Sections. 14 CF R 27.337, 27.471, 27.561, 27.773, 27.783, 27.785, 27.807, 27.831, 27. 853, 27.1301, 27.1309, 27.1353, 27.1357, 27.1365, 27.1367, 27.1411, 27.1413, 27. 1431, 27.1557(d), 27.1561, 27.1581(a)(2), 27.1583(d), 27.1585, 27.1589, 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 27-1B

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

Page MG 6 - 22 FIGURE AC 27.MG 6-2 TYPICAL LIQUID OXYGEN SYSTEM - USING

COMBINATION VALVE