breathing requirements stated above must be provided. If the airplane is not to be used in parts 121, 125, or 135 operation (i.e., in Part 91 operation), installation of either type of oxygen equipment at the first observer's seat is adequate to show compliance with the requirements of § 25.1441, Oxygen Equipment and Supply, and installation of communication equipment and protective breathing equipment would be optional.
(c) The duration of oxygen supply should be commensurate with the crew supply, since protection may be necessary due to a delayed descent following decompression, protective breathing requirements, or other extended usage.
e. References. The addresses for ordering the latest revision of technical standard orders and other referenced documents listed below can be found in the Appendix to this AC.
TSO-C64a, Oxygen Mask Assembly Continuous Flow, Passenger (For Air Carrier Aircraft).
TSO-C78, Crewmember Demand Oxygen Masks.
TSO-C89, Oxygen Regulators, Demand.
TSO-C99, Protective Breathing Equipment.
TSO-C116, Crewmember Protective Breathing Equipment.
The Society of Automotive Engineers (SAE) has aerospace committees which prepare documents reflecting industry standards and practices. The SAE A-10 Committee, Aircraft Oxygen Equipment, has prepared a handbook, “1992 SAE Aircraft Oxygen Equipment Handbook,” containing all Aerospace Standards, Aerospace Recommended Practices, and Aerospace Information Reports related to oxygen equipment published by SAE. While not regulatory in nature, this handbook contains information that may be of interest to an applicant.
67. SECTION 25.1449 - MEANS FOR DETERMINING USE OF OXYGEN.
a. Rule Text.
There must be a means to allow the crew to determine whether oxygen is being delivered to the dispensing equipment.
b. Intent of Rule. The standards in this section ensure that the flightcrew is able to determine that oxygen is being dispensed properly.
c. Background. Effective February 1, 1965, part 25 was added to Title 14, Code of Federal Regulations (14 CFR) to replace part 4b of the Civil Air Regulations (CAR). The requirement in § 4b.651(e) of the CAR that there be a means for the crew to determine that oxygen is being delivered to the dispensing equipment (masks) were carried over essentially unchanged to § 25.1449 of 14 CFR.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information. Compliance with this section is usually 161
accomplished by the use of flow indicators in the oxygen regulators (for flight crewmembers) and in the oxygen tubes leading to the masks (for passenger equipment).
(1) Oxygen Equipment for Observer Position. The following policy was extracted from an FAA letter dated April 19, 1996, in response to an inquiry concerning the requirement for supplemental oxygen flow indication at the observers' stations.
(a) An applicant proposed installing mask-mounted regulators without flow indication at the observers' stations. This configuration has been certified for previous versions of the same airplane model. It was the applicant’s position that the FAA exempts mask-mounted regulators from the § 25.1449 flow indication requirement. They cited FAA Technical Standard Order (TSO) C-89, which exempts mask-mounted regulators from the TSO requirement to provide a means to indicate oxygen flow from the regulator outlet. Although the TSO allows omission of flow indicators for mask-mounted regulators, it is not an authorization to install such items on transport airplanes. However, the FAA reviewed the original certification data for the airplane model in question, and the background of § 25.1449. Based on this review, the FAA determined that installation of the mask-mounted regulators without flow indicators at the observers' stations meets the intent of § 25.1449.
(b) The background for § 25.1449 is found in the FAA Civil Aeronautics Manual (CAM) 4b. Section 25.1449 states: "There must be a means to allow the crew to determine whether oxygen is being delivered to the dispensing equipment." Similarly, § 4b.651 of the Civil Air Regulation (CAR) states: "Means shall be provided to enable the crew to determine whether oxygen is being delivered to the dispensing units." Although flow indicators for each individual passenger or flight crew station represent one method of compliance, policy guidance provided in § 4b.651-10 of the CAR (for crew systems) and § 4b.651-11 of the CAR (for passenger systems) allows operators to establish procedures for checking the oxygen flow to individual oxygen users. For passenger diluter-demand systems, § 4b.651-11 of the CAR states that the procedure may be "checking of the oxygen flow by a trained crewmember by momentarily moving the regulator lever to Automix ‘OFF’ (100% OXYGEN) while the mask is being worn."
Lack of oxygen flow would be "immediately evidenced by the user's inability to inhale while wearing his mask."
(c) The FAA is satisfied that § 25.1449 does not specifically require flow indicators at each mask. Although these indicators are generally provided, other methods of flow indication are not precluded. Therefore, the FAA is satisfied that flow indicators are not required at the observers' stations for certification, provided that the applicant incorporates suitable design features and procedures to ascertain flow at the observers' stations. On the model in question, supplemental oxygen for the flightcrew and the observers' stations is provided by a common source. Flow of oxygen from the source is split between the flight crew and observers' stations by a "T" fitting. Under normal operations, all cockpit masks are set for "100% OXYGEN." At this setting, lack of flow would be immediately detected by the user. The FAA is requiring incorporation of a preflight check of the observers' masks in the airplane flight manual (AFM).
In addition, a positive indication of flow at the flightcrew stations by the flow indicators installed at those stations would indicate that oxygen is also flowing to the observers' stations. The FAA 162
is satisfied that the system design, the preflight inspection procedure, and flow indicators at the flightcrew stations are adequate to meet the intent of § 25.1449.
(2) Determination of Passenger Oxygen Supply. The following policy was extracted from an FAA memorandum dated January 8, 1996, which addresses compliance with § 25.1449 for a design that will determine, from the flightdeck, that oxygen is flowing to the passenger supplemental oxygen masks. It is noted that 14 CFR does not require a means for the flightcrew to make this determination while on flight deck duty. A number of airplanes have gaseous supplemental oxygen systems which do not have a specific indication of oxygen flow on the flight deck. Compliance with 14 CFR requirements is usually shown through use of a flow indicating device in the oxygen mask tubing. Technical Standard Order TSO-C64a, and the associated Society of Automotive Engineers Aerospace Standard SAE-AS 8025, require a means for the crew to determine that oxygen is flowing. This is usually accomplished with a small device that provides a green indication when the flow rate exceeds 0.5 liters per minute. A cabin crewmember verifies from the indicator whether or not oxygen is flowing. If there are no cabin crewmembers, this would require a flight crewmember to leave their station and check. The FAA has determined that this would not be a viable option during an emergency such as a decompression.
e. References. None.
68. SECTION 25.1450 - CHEMICAL OXYGEN GENERATORS.
a. Rule Text.
(a) For the purpose of this section, a chemical oxygen generator is defined as a device which produces oxygen by chemical reaction.
(b) Each chemical oxygen generator must be designed and installed in accordance with the following requirements:
(1) Surface temperature developed by the generator during operation may not create a hazard to the airplane or to its occupants.
(2) Means must be provided to relieve any internal pressure that may be hazardous.
(c) In addition to meeting the requirements in paragraph (b) of this section, each portable chemical oxygen generator that is capable of sustained operation by successive replacement of a generator element must be placarded to show-
(1) The rate of oxygen flow, in liters per minute;
(2) The duration of oxygen flow, in minutes, for the replaceable generator element; and
(3) A warning that the replaceable generator element may be hot, unless the element construction is such that the surface temperature cannot exceed 100 degrees F.
[Amdt. 25-41, 42 FR 36971, Jul. 18, 1977]
b. Intent of Rule. The standards in this rule ensure that chemical oxygen generators safely provide oxygen.
c. Background. The standards in this section address chemical oxygen generators. This subject was not addressed in either part 4b of the CAR or part 25 when it was originally codified.
This section was added at Amendment 25-41, July 18, 1977.
d. Policy/Compliance Methods. There is no written policy or guidance in our files.
e. Reference. The address for ordering the latest revision of the document listed below can be found in the Appendix to this AC.
The Society of Automotive Engineers (SAE) has aerospace committees that prepare documents reflecting industry standards and practices. The SAE A-10 Committee, Aircraft Oxygen Equipment, has prepared a handbook, “1992 SAE Aircraft Oxygen Equipment Handbook,” containing all Aerospace Standards, Aerospace Recommended Practices, and Aerospace Information Reports related to oxygen equipment published by SAE. While not regulatory in nature, this handbook contains information that may be of interest to an applicant.
69. SECTION 25.1453 PROTECTION OF OXYGEN EQUIPMENT FROM RUPTURE.
a. Rule Text.
Oxygen pressure tanks, and lines between tanks and the shutoff means, must be-
(a) Protected from unsafe temperatures; and
(b) Located where the probability and hazards of rupture in a crash landing are minimized.
b. Intent of Rule. This rule ensures that the oxygen equipment is not exposed to unsafe temperatures and minimizes the possibility of rupture in the event of a crash landing.
c. Background. Effective February 1, 1965, part 25 was added to Title 14, Code of Federal Regulations (14 CFR) to replace part 4b of the Civil Air Regulations (CAR). The requirements in § 4b.651(g) of the CAR were carried over essentially unchanged to § 25.1453 of 14 CFR.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information.
(1) Flexible Plastic Oxygen Lines. The following policy was extracted from an FAA memorandum dated December 27, 1983, to provide guidance regarding the use of flexible plastic tubing for oxygen distribution lines. While this guidance was generated for Part 23 airplanes, it is equally applicable for part 25 airplanes.
(a) The FAA has determined that the use of plastic lines for an oxygen distribution system that is operating under continuous pressure is not acceptable for certification in Part 23 airplanes.
(b) Lines constructed of combustible materials, including nylon, polyvinylchloride (PVC) and Teflon, may be used in oxygen lines which are pressurized only when cabin depressurization occurs. The following precautions should be taken when using such lines in the oxygen system:
1 Swaged metal type end fittings should be used to prevent leakage from cold flow.
2 Lines should be protected from abrasion by use of a reinforcing sleeving of fabric braid.
3 Precautions should be taken to route such lines away from areas where they might be subjected to elevated temperatures, electrical arcing (relays and switches) and flammable fluids.
4 Refer to Advisory Circular (AC) 43.13-2A, Chapter 6, for additional guidance material.
(2) Use of Plastic Oxygen Lines. The following policy was extracted from an FAA memorandum dated October 28, 1983, and addresses the use of plastic or nylon tubing as oxygen lines.
(a) Tubing in the fuselage for high or low pressure oxygen systems that are located behind liners or in the walls of the fuselage are typically made of rigid stainless steel (for high pressure) or aluminum (for low pressure). Synthetic flexible lines connecting the oxygen mask to the oxygen distribution system have been accepted. Swaged metal end fitted PVC tubing, covered with a synthetic braid (for abrasion resistance and strength), should be used between the aluminum low pressure distribution line and the passenger service unit manifold of many large transports. These tubes and aluminum line do not contain oxygen until a depressurization occurs. Then, the pressure is low and for a short duration. These hoses meet the interior burn requirements.
(b) Synthetic lines such as plastic or nylon cannot be recommended for oxygen high or low pressure lines that will be exposed to a continuous pressure (i.e., as opposed to pressurized when needed). These materials can cold flow. Care must be taken in the selection of the fitting design for exposures of even short duration.
(c) In addition to cold flow, polyethylene and nylon will lose strength with increasing temperature. These materials are much more susceptible to combustion in the presence of oxygen than either stainless steel or aluminum. For these reasons, the FAA 165
considers polyethylene or nylon tubing inappropriate and unsafe for oxygen lines that are subjected to continuous oxygen pressure.
e. Reference. The address for ordering the document listed below can be found in the Appendix to this AC.
The Society of Automotive Engineers (SAE) has aerospace committees that prepare documents reflecting industry standards and practices. The SAE A-10 Committee, Aircraft Oxygen Equipment, has prepared a handbook, “1992 SAE Aircraft Oxygen Equipment Handbook,” containing all Aerospace Standards, Aerospace Recommended Practices, and Aerospace Information Reports related to oxygen equipment published by SAE. While not regulatory in nature, this handbook contains information that may be of interest to an applicant.
70. SECTION 25.1455 - DRAINING OF FLUIDS SUBJECT TO FREEZING.
a. Rule Text.
If fluids subject to freezing may be drained overboard in flight or during ground operation, the drains must be designed and located to prevent the formation of hazardous quantities of ice on the airplane as a result of the drainage.
[Amdt. 25-23, 35 FR 5680, Apr. 8, 1970]
b. Intent of Rule. This rule addresses fluids subject to freezing that normally drain from the airplane either in flight or during ground operation. The intent is to prevent damage to the airplane when the ice disengages and falls free. This section addresses "gray" water from the sinks and drains in galleys and lavatories. Section 25.1455 does not apply to lavatory drain systems that are normally drained when the airplane is parked, rather than being in "ground operation." This requirement is usually met by designing the drain masts (usually heated to prevent the fluid from freezing) so that the fluid does not impact the airframe or engines when it is draining.
c. Background. Effective February 1, 1965, part 25 was added to Title 14, Code of Federal Regulations (14 CFR) to replace part 4b of the Civil Air Regulations (CAR). The requirements in section 4b.660 of the CAR were carried over to § 25.1455 of 14 CFR.
(1) Amendment 25-23 (April 8, 1970) changed the intent of the rule from preventing the formation of ice to preventing the formation of hazardous quantities of ice on the airplane as a result of drainage.
d. Policy/Compliance Methods. There is no written policy or guidance in our files.
e. Reference. The address for ordering the latest revision of the advisory circular listed below can be found in the Appendix to this AC.
AC 25.1455-1, Waste Water/Potable Water Drain System Certification Testing.
71. SECTION 25.1461 - EQUIPMENT CONTAINING HIGH ENERGY ROTORS.
a. Rule Text.
(a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section.
(b) High energy rotors contained in equipment must be able to withstand damage caused by malfunctions, vibration, abnormal speeds, and abnormal temperatures.
In addition-
(1) Auxiliary rotor cases must be able to contain damage caused by the failure of high energy rotor blades; and
(2) Equipment control devices, systems, and instrumentation must reasonably ensure that no operating limitations affecting the integrity of high energy rotors will be exceeded in service.
(c) It must be shown by test that equipment containing high energy rotors can contain any failure of a high energy rotor that occurs at the highest speed obtainable with the normal speed control devices inoperative.
(d) Equipment containing high energy rotors must be located where rotor failure will neither endanger the occupants nor adversely affect continued safe flight.
[Amdt. 25-41, 42 FR 36971, Jul. 18, 1977]
b. Intent of Rule. This rule ensures that failures of high energy rotating equipment will not adversely affect systems, structure, or occupants in the event that the rotating components fail at high speeds. Some of the equipment that contains high energy rotors are turbine engine starters, air cycle machines, air driven hydraulic pumps, cooling fans for galley equipment and electronic bays, cabin ventilation recirculation fans, and high speed electrically driven hydraulic pumps.
This section does not pertain to equipment covered by Subpart E, Propulsion, such as engines and auxiliary power units, which are covered by the provisions of § 25.903(d).
c. Background.
(1) Amendment 4b-8 of the Civil Air Regulations (CAR). This subject was first addressed in part 4b of the CAR under Amendment 4b-8, effective May 17, 1958. A new § 4b.659 was included which required appropriate protection of the airplane against failure of high energy rotors when such rotors were incorporated in any equipment on the airplanes.
Section 4b.659 read "Equipment incorporating high energy rotors shall be demonstrated as capable of containing a failed rotor or shall be so located that failure will not affect the ability of the airplane to continue safe flight."
(2) Amendment 4b-12 of the Civil Aeronautics Manual (CAM). Amendment 4b-12, effective May 13, 1962, deleted § 4b.659 because it was surmised that its substance was covered by the provisions of § 4b.606 (which later became § 25.1309) which is concerned with the reliability of all equipment, systems, and installations.
(3) Amendment 25-41. Amendment 25-41 added § 25.1461 as a result of an Airworthiness Review Program conducted in 1975. This new section added requirements for protection against the failure of equipment containing high energy rotors. Experience had demonstrated that failures which release the energy stored in these rotors may result in engine or structural damage, fires, or injury to occupants.
d. Policy/Compliance Methods. Compliance to §25.1461(c) is accomplished if it can be shown by test that equipment containing high-energy rotors can contain any failure of the rotor that occurs at the highest speed obtainable with normal speed control devices inoperative. In general, three phase induction motor driven fans do not have speed control devices. Fan speed is a function of the input power frequency supplied to the device.
(1) Because of the absence of speed controls, these fans can be treated as an extension of the aircraft power generating system. To comply with § 25.1461(c), the minimum test speed would be at the highest speed obtainable with power generating system speed control devices inoperative (speed control device is the mechanical system that governs generator shaft speed).
In the event of such a failure, generating system controls will limit frequency. Exceeding those limits would require further multiple failures. These higher order failures do not have to be considered to comply with § 25.1461(c).
(2) For external ground power operation, the same frequency limits are applicable. The cart (or other) providing power must fail, the cart protective overfrequency protection must fail, and the airplane protective systems must fail to trip the external power contactor. In addition, an uncontained fan rotor burst on the ground is classified differently as it is not a safety of flight issue.
e. References. None.
Chapter 4. OPERATING LIMITATIONS AND INFORMATION
Section 1. OPERATING LIMITATIONS
72. SECTION 25.1529 - INSTRUCTIONS FOR CONTINUED AIRWORTHINESS.
a. Rule Text.
The applicant must prepare instructions for Continued Airworthiness in accordance with Appendix H to this Part that are acceptable to the Administrator.
The instructions may be incomplete at type certification if a program exists to [Amdt. 25-54, 45 FR 60173, Sep. 11, 1980] ensure their completion prior to delivery of the first airplane for issuance of a standard certificate of airworthiness, whichever occurs later.
H25.4 Airworthiness Limitations section.
The Instructions for Continued Airworthiness must contain a section titled Airworthiness Limitations that is segregated and clearly distinguishable from the rest of the document. This section must set forth each mandatory replacement time, structural inspection interval, and related structural inspection procedures approved under § 25.571. If the Instructions for Continued Airworthiness consist of multiple documents, the section required by this paragraph must be included in the principal manual. This section must contain a legible statement in a prominent location that reads: "The Airworthiness Limitations section is FAA approved and specifies maintenance required under §§ 43.16 and 91.403 of the Federal Aviation Regulations unless an alternative program has been FAA approved."
[Amdt. 25-54, 45 FR 60173, Sep. 11, 1980; Amdt. 25-68, 54 FR 34329, Aug. 18, 1989]
b. Intent of Rule. The purpose of this rule is to ensure continued airworthiness of the airplane by requiring that inspections, checks, and replacement of parts are performed in accordance with the requirements established for type certification.
c. Background. This subject was not addressed in either section 4b of the Civil Air Regulations (CAR) or part 25 of Title 14, Code of Federal Regulations (14 CFR). This rule was added, along with Appendix H, by Amendment 25-54.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the airworthiness limitations document.
e. Reference. The address for ordering the latest revision of the advisory circular listed below can be found in the Appendix to this AC.
Advisory Circular 25-19, Certification Maintenance Requirements.
APPENDIX 1, CROSS REFERENCE FOR SELECTED SECTIONS OF PART 25, CAR 4b/CAM 4b
DISTRIBUTION TABLE
Revised Section Former Section Revised Section Former Section
25.671 4b.320 (less (b)) 25.869(b) 25.1443(b) & (c) [4b.658]
25.672 not applicable 25.869(c) 25.1451 [4b.651(f)]
25.699 4b.323(e) & (f) 25.1001 4b.437 (less (e) (last sent.))
25.701 4b.324 25.1183 4b.333, 4b.483
25.703 not applicable 25.1185 4b.481
25.729 4b.334, -2 25.1189 4b.382
25.731 4b.335(a) & (b) 25.1301 4b.600, 4b.601
25.733 4b.336 25.1309 4b.606
25.735 4b.335 less (a), (b) 25.1416 not applicable 4b.337, -4 (1st sent.) 25.1419 4b.640 (less intro, 3rd sent.
25.771 4b.350 25.1431 4b.650
25.773 4b.351 25.1433 4b.658
25.775 4b.352 25.1435 4b.653, 4b.654, 4b.655
25.777 4b.353 25.1438 not applicable
25.783 4b.356, -1(last sent) 25.1439 4b.651 (less (a)-(g) 4b.356-2(a)/1st sent 25.1441 4b.651(a)
25.831 4b.371, 4b.371-1 25.1443 4b.651(b)
25.832 not applicable 25.1445 4b.651(c), 4b.651-5a
25.833 4b.372 25.1147 4b.651(d)
25.841 4b.374, 4b.375, -1 25.1449 4b.651(e)
25.843 4b.376 25.1450 not applicable
25.851 4b.380 (less (c)), 4b.383 (2nd sent. of (a) &
(b)(3)
25.1453 4b.651(g)
25.854 not applicable 25.1455 4b.660
25.855 4b.382, 4b.384 25.1461 not applicable
25.857 not applicable
25.858 not applicable
25.863 4b.385
APPENDIX 2, GLOSSARY OF ACRONYMS
AC Advisory Circular ACO Aircraft Certification Office AD Airworthiness Directive AFM Airplane Flight Manual AIA Aerospace Industries Association AIR Aircraft Certification Service ARAC Aviation Rulemaking Advisory Committee ARP Aerospace Recommended Practice (SAE) BTMS Aircraft Brake Temperature Monitor System CAA Civil Aeronautics Administration (US) CAR Civil Air Regulations CAM Civil Aeronautics Manual CFR Code of Federal Regulations DER Designated Engineering Representative ECS Environmental Control System EICAS Engine Indication and Crew Alerting System FAR Federal Aviation Regulations IIDSS Inflight Ice Detection Sensing Systems JAA Joint Aviation Authorities JAR Joint Airworthiness Requirements KE Kinetic Energy NOE Non-original Equipment NTSB National Transportation Safety Board OAT Outside Air Temperature OBOGS On-Board Oxygen Generating System OEM Original Equipment Manufacturer PBE Protective Breathing Equipment PMA Parts Manufacturer Approval PPM Parts Per Million PPMV Parts Per Million by Volume QTR Qualification Test Report R&D Research & Development RTO Rejected Take-off SAE Society of Automotive Engineers SLD Supercooled Large Droplets SLE Sea Level Equivalent STC Supplemental Type Certificate TAD Transport Airplane Directorate TAT Total Air Temperature TC Type Certificate TSO Technical Standard Order TWA Time-Weighted-Average 171