(6) Indication and warning.
(7) Installation and support.
(8) Pump/engine interface.
(9) Fire protection.
(10) Continued safe flight and 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). Sections 4b.653, 4b.654, and 4b.655 respectively became §§ 25.1435(a), 25.1435(b), and 25.1435(c) of 14 CFR for hydraulic systems. Since then, § 25.1435 has been revised under Amendment 25-13, Amendment 25-41, and Amendment 25-72 to make the regulations more comprehensive and to delete redundancies.
(1) Amendment 25-13 (June 28, 1967) prescribed more comprehensive design and test requirements by requiring (1) cockpit indication of system fluid quantity, (2) a means to prevent harmful or hazardous concentrations of the fluid or vapors in the crew or passenger compartments during flight due to hydraulic fluid leakage/release, and (3) compliance with § 25.1309 by functional tests, endurance tests, and analysis of the entire system or appropriate subsystems tested in an airplane or in a mockup installation to determine proper performance and proper relation to other aircraft systems.
(a) Regarding compliance with § 25.1435(b)(2), the preamble to the final rule states in part that, "the FAA agrees that the proposed environmental testing of the assembled system is not necessary in order to achieve a reasonable and effective testing program for improving hydraulic system reliability." The final rule was changed to allow applicants to meet endurance test requirements by performing endurance testing on components as long as the test program was representative of the airplane installation and environment.
(b) Applicants have shown compliance to the endurance testing requirements of § 25.1435 by conducting endurance tests on components or subassemblies using fixtures that represent the airplane installation and environmental conditions. The FAA normally accepts endurance test programs that vary hydraulic fluid temperature during endurance testing. The other environmental conditions are usually tested independent of the endurance test program.
The regulation does not specify the number of repeated cycles to meet endurance test requirements. As a minimum, the applicant must show that the reliability of components will meet the airplane system reliability requirements of § 25.1309.
(2) Amendment 25-23 (April 8, 1970) expanded § 25.1435(a)(4) to require means to ensure that no pressure will exceed a safe limit above design operating pressure by specifying pressure variation tolerances of +/- 10% on the pump discharge pressures and an upper limit of 125% of the design operating pressure for transients. These tolerances were based on in-service experience with such systems.
(3) Amendment 25-41 (July 18, 1977) clarified under § 25.1435(a)(2) that the pressure and quantity indication requirement was applicable to systems performing a function that is essential for continued safe flight and landing, or requiring corrective crew action when a system malfunction has occurred. It also recognized that means other than gages (e.g., warning lights) were an acceptable means of compliance. Sections 25.1435(a)(7) and 25.1435(a)(8) were added to allow certain transient pressures to exceed prescribed limits under (a)(4)(ii), provided the resulting fatigue strength was accounted for, and to require pump design such that loss of fluid condition could not create a hazard preventing continued safe flight and landing.
(4) Amendment 25-72 (July 20, 1990). Prior to this amendment, § 25.1435(b) was labeled "Tests," and contained references to a hydraulic system proof test, which was needed in order to comply with § 25.1309. Under Amendment 25-72, the general requirements of the old §§ 25.1435(a)(2) through 25.1435(a)(8), relative to indication, system pressures, transients, volumetric changes, pump discharge pressure limits, ripple damping devices, vibration, abrasion, corrosion, mechanical damage, inertia loads, hazardous vapors, relative motion, differential vibration, transient pressures, fatigue strength and loss of fluid to the pumps, were consolidated under a general listing as "Tests and Analyses" in the new § 25.1435(b)(2).
(5) Exemptions. In October 1993, pursuant to the authority contained in §§ 313(a) and 601(c) of the Federal Aviation Act of 1958, an applicant was granted an exemption (refer to exemption 5758A) from § 25.1435(b)(1) of Title 14, Code of Federal Regulations (14 CFR) to the extent necessary to permit type certification of a new airplane by testing of the complete hydraulic system at the system relief pressure, but not less than 3400 psig, in lieu of 1.5 times the design operating pressure (4500 psig). Additional similar exemptions have been granted (Refer to Exemptions 6086, 6504, and 6577).
(6) Harmonization. This regulation is the subject of a Federal Aviation Regulations/Joint Aviation Requirements (FAR/JAR) harmonization effort under the Aviation Rulemaking Advisory Committee (ARAC). The ARAC working group has recommended revisions to § 25.1435 and a new Advisory Circular (AC) 25.1435-1. The harmonized rule will reflect the exemptions granted, see (5) above. The notice of proposed rulemaking (NPRM 96-6) and accompanying proposed AC 25.1435-1, were published in the Federal Register on July 3, 1996 (61 FR 35056) and public comments were invited. The final rule is at the FAA headquarters for a regulatory evaluation. The final rule and AC are expected to be adopted in 2000.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information.
(1) Hydraulic Fluid Contamination. The following was extracted from an FAA letter to the National Transportation Safety Board (NTSB), dated June 29, 1998, and related correspondence. The NTSB accepted the FAA-Industry (Society of Automotive Engineers Committee A-6) task force resolution concerning the NTSB safety recommendation, A-96-116.
(a) Background. Following the crash of the USAir flight 427, a Boeing 737-300, on September 8, 1994, an NTSB investigation team found hydraulic fluid with a high particulate count in the main rudder power control unit (PCU). While the effect of contaminated hydraulic fluid on the different aircraft systems was not known at that time, it was examined as a potential factor. In October 1996, the NTSB made safety recommendation, A-96-116, which recommended that the FAA define and implement standards for in-service hydraulic fluid cleanliness and sampling intervals for all transport-category aircraft.
(b) Discussion. An April 1995, FAA study concluded that the existing standard, NAS 1638, was adequate for classifying the particulate contamination levels for aircraft hydraulic fluid. At the FAA's request, an industry task force formed by the Society of Automotive Engineers (SAE) Committee A-6 studied the fluid contamination issues. The industry task force concluded that (i) flight control servoactuators had demonstrated operation at contamination levels up to NAS 1638 class 17 and higher and, (ii) an in-service limit of NAS 1638 class 9 prescribed by the majority of current airframe manufacturers was conservative, adequate, and the maximum recommended limit. The task force also studied chemical contamination effects and provided in-service limits for fluid properties such as specific gravity, moisture content, viscosity, and chlorine content.
(c) Chemical Sensitivity. Actuation systems are insensitive to chemical contamination within normal in-service operational limits (see tabulation below). Gross contamination with other fluids is prohibited.
Chemical Quality Recommendations for In-Service Hydraulic Fluid
Analysis Limit Reason
Appearance No cloudiness or phase separation or precipitation Particulate and/or chemical contamination
Moisture 1.0 percent maximum Corrosion, fluid stability (acidity), low temperature pumpability
Neutralization number 1.5 mg KOH/gm maximum Corrosion, deposit formation
Kinematic viscosity @ 100ºF/38ºC
6.0 - 12.5cs Lubricity
Chlorine contamination* 200 ppm maximum Fluid purity, erosion
* This limitation is in addition to the amount already contained in the base stock.
(d) Sensitivity Methods. The task force recognized that the inconsistencies in the existing hydraulic fluid sampling procedures gave wide variations in the measured levels of particulate contamination. As a result, an Aerospace Recommended Practice ARP-5376, "Methods, Locations and Criteria for System Sampling and Measuring the Solid Particle Contamination of Hydraulic Fluids," was developed and published in September 1998.
(e) Sampling. The fluid sampling interval requirement for particulate contamination check is the same as the current one for checking chemical contamination.
Typical fluid sampling intervals used by airlines are on-condition, C-check, and 2C-check. In addition, manufacturers recommend fluid sampling when a suspected hydraulic contamination may exist (for example, due to or indicated by excessive component wear or deterioration).
(f) In summary. The FAA has identified an existing industry standard, NAS 1638, that defines fluid cleanliness levels as Classes 00 to 12; has defined NAS 1638 class 9, as the inservice limit, verified that the manufacturers already recommend these limits in their maintenance manuals including a sampling interval, and helped develop an SAE ARP document for sampling and testing techniques. The intent of the safety recommendation has been met and no regulatory corrective action is deemed necessary.
(2) Certification of Hydraulic Lines for Temporary Repairs. The following was extracted from an FAA letter dated April 23, 1992, which addresses certification of hydraulic lines for use as temporary repairs.
(a) It is not clear from the applicant's letter whether the hydraulic tubing assemblies being discussed are rigid or flexible, but it is assumed that the discussion involves various lengths of flexible hydraulic hose assemblies which can be joined together to replace 140
rigid or flexible hydraulic lines that have become unserviceable. There is an FAA Technical Standard Order (TSO) which provides minimum airworthiness requirements for hydraulic hose assemblies intended for use on transport category airplanes. Technical Standard Order TSO- C75, Hydraulic Hose Assemblies, and the accompanying Federal Aviation Standard should be considered. It should be noted that while the TSO provides an authorization for manufacturing a part that meets certain standards, it does not automatically approve the part for a specific installation.
(b) Section 43.13(a) requires that repairs must be accomplished in accordance with the manufacturers' maintenance manuals. However, air carriers are supposed to follow their Air Carrier Manual approved under part 121.
(c) The only mechanism available for certification of these repair systems by a manufacturer other than the type certificate holder would be a Supplemental Type Certificate (STC). An STC, issued for each installation on every model of airplane on which the applicant desired approval, would be a daunting task. Major airframe manufacturers, because they have all the pertinent data regarding design parameters for the hydraulic systems on their airplanes, can issue appropriate instructions in their maintenance manuals for installation of temporary repairs.
Airlines should use the manufacturer's manuals per § 43.13(a).
(d) One of the ways a manufacturer, other than the type certificate holder who wishes to manufacture parts for a certificated airplane, can apply for a Parts Manufacturing Authorization (PMA) is to show that the parts it makes are identical to those produced by the original manufacturer. Unless the applicant has original drawings complete with all necessary standards and specifications, it is difficult to show identicality. The cognizant FAA Manufacturing Inspection District Office can provide insight into the appropriate PMA application procedures, reference Order 8110.42A.
(3) Use of Hydraulic Lines for Temporary Repairs. The following was extracted from an FAA memorandum dated January 25, 1988, which addresses the use of flexible hydraulic hoses as temporary repairs for unserviceable hydraulic tubing.
(a) The use of flexible hydraulic hoses as temporary repairs for unserviceable hydraulic tubing has been commonplace on transport category airplanes for a number of years.
The lack of adverse service history indicates that this practice can be a viable method of repair, when used with the proper cautions. Strictly speaking, such substitution of hoses for rigid tubing would cause the airplane to be not in compliance with its type design; however, the provisions of Part 43 allow repairs and alterations to be made, provided the work is done in accordance with the methods, techniques, and practices in the current manufacturer's maintenance manual. With respect to multiple repairs, the FAA has concluded that they would be acceptable, provided that each one is individually performed in accordance with an approved procedure, and, collectively, the repairs will not interfere with each other or with any structure, or with the operation or performance of any system on the airplane.
(b) The key issue is the length of time that these temporary repairs may be allowed to exist on the airplane. Only by limiting the exposure can the repair be considered to be a safe alternative to the original design, much in the same manner that the Minimum Equipment List allows operation of the airplane for a short time with certain items of equipment inoperative.
Since a temporary repair would not have been evaluated and certificated in the same manner as the original system, it would not be proper to allow the repair to become, in any way, a permanent part of the type design. It has been suggested by one manufacturer that these repairs be replaced at the next "C" check, which in some cases may be a year in the future. The FAA has concluded that this much time is unwarranted, and may seriously compromise the safety of the repair. An interval of 300 to 350 hours would, in most cases, allow for the ordering and delivery of any needed parts and the scheduling of the airplane for restoration of the system to the original configuration. Also, limiting the time in this manner will reduce the problem of multiple repairs on the system. Any time limit would be largely arbitrary, but this figure, which represents approximately a month of operations, appears to be a good compromise between the economic interests of the operators, and the need for a short exposure to the temporary repair.
(4) Hydraulic System Certification Philosophy. The following was extracted from an FAA letter dated March 5, 1982, which addresses guidance concerning compliance with § 25.1435(b)(2), 14 CFR.
(a) The FAA has not been requested to accept endurance and reliability data based solely on flight test. This is because it is impractical, within a given certification time frame, to conduct the number of test cycles required to comply with § 25.1435(b)(2). The FAA would have no objection to using flight test data in addition to simulated functional endurance and reliability data, provided the manufacturer establishes that the flights are representative of expected service cycles.
(b) It is normal practice, for certification purposes, to comply with the requirements of § 25.1435(b)(2) by the use of simulators such as an "iron bird." The simulators are intended to be representative of the aircraft systems. Mounting brackets, hydraulic and electrical system flight controls, and control surfaces are all the same as the actual airplane. For practical purposes, simulation may be broken into functional subsystems, i.e., wing, rudder, gear, etc. Deviations from actual simulation have been allowed where the deviation will not interfere with the intent of establishing endurance and reliability. Deviation cases have to be ruled on in a case by case basis.
(c) The FAA would not accept compliance with § 25.1435(b)(2) based on only vendor component tests and flight tests. Functional tests and endurance tests, either using an airplane or mock-up (iron bird, simulator) at the system or subsystem level, are required.
Functional tests are required prior to first flight test.
(d) The manufacturer will develop load data through analysis, wind tunnel data, flight test experience, and/or any combination of these (spoilers and slots require flight test data, § 25.459). This load data is submitted to the FAA in the form of a loads document. The loads document is usually approved by FAA designated engineering representatives (DER) and 142
submitted to the FAA for a spot check review when and where it is considered necessary. Flight test load verification is not required when the methods used in determining those loading conditions are shown to be reliable (§ 25.301(b)). Most manufacturers go beyond FAA requirements and check the loads with strain gauges during flight tests.
(e) The airframe manufacturer (type design applicant) identifies the loading spectrum (amplitude and cycles) for the hydraulic systems based on the loads document and expected service. The FAA will be involved only indirectly in most cases, through the loads DER’s.
(f) The manufacturer subjects components and systems or the aircraft to the selected load/cycle spectrum in demonstrating compliance with the endurance requirements of § 25.1435(b)(2). Normally, vendor testing will be used for verification of the components for endurance as well as other requirements, such as environmental qualifications, fatigue, etc. The airframe manufacturer's simulator (iron bird) or simulators will be used for endurance tests and functional tests. The qualification reports documenting these tests are reviewed by FAA DER’s and approved or submitted to the FAA with a recommendation for approval. This option is designated by the FAA.
(5) Interpretation of § 25.1435(a)(4) of 14 CFR. The following was extracted from an FAA memorandum dated September 14, 1978, which addresses interpretation of § 25.1435(a)(4), Amendment 25-41.
(a) Section 25.1435(a)(4)(i) states: "There must be a means to keep hydraulic system pressures within +/- 10 percent of the pressure at the discharge of the pump outlet or the transient pressure dampening device, if provided."
(b) This rule was originally established to cover pump ripple pressure variations.
It can be seen that, under extreme system loading (high flow) conditions, the pump average discharge pressure can decrease as much as 25 percent. Apparently, the system pressure tolerance of +/- 10 percent mentioned above would then apply to this reduced pump average discharge pressure, decreased due to high flow conditions.
(c) Section 25.1435(a)(4)(ii) states: "Except as provided in Paragraph (a)(7) of this section, system pressures will not exceed 125 percent of the design operating pressure, excluding pressure at the pump outlet or dampening device. Design operating pressure is defined as the maximum steady operating pressure."
(d) The FAA has determined that Paragraph (4)(i) covers pressure variations due to pump ripple and high flow conditions while Paragraph (4)(ii) covers variations due to pressure transients. Note the use of "pump average discharge pressure" in (4)(i) and "design operating pressure" in (4)(ii).
e. References. The addresses for ordering the latest revision of advisory circulars, technical standard orders, and other referenced documents listed below can be found in the Appendix to this AC.
AC 25.1309-1A - System Design and Analysis.
AC 120-42A - Extended Range Operation with Two Engine Airplanes.
AC 20-128 - Design Considerations for Minimizing Hazards Caused by Uncontained Turbine Engine and Auxiliary Power Unit Rotor and Fan Blade Failures.
TSO-C47 - Pressure Instruments-Fuel, Oil, and Hydraulic.
TSO-C75 - Hydraulic Hose Assemblies.
SAE AS-595B - Civil Type Aircraft and Variable Delivery Hydraulic Pump.
SAE ARP-763 - Accumulators, Ground, Hydropneumatic Pressure.
SAE AIR-4150 - Inspection of In-Service Airborne Accumulators.
SAE AIR-1047C - A Guide for Selection of Quick Disconnect Couplings for Aerospace Fluid Systems.
SAE ARP-1709 - Coupling Assembly, Hydraulic Self Sealing, Quick Disconnect.
SAE AIR-786A - Elastomer Compatibility Considerations Relative to O-Ring and Sealant Selection.
SAE AS-1241B - Fire Resistant Phosphate Ester Hydraulic Fluid for Aircraft.
SAE AIR-1116 - Fluid Properties.
SAE ARP-1084 - Hydraulic External Leakage for In-service Components.
SAE AIR-1362 - Physical Properties of Hydraulic Fluids.
SAE ARP-1832 - Color Identification for O-Ring Seals.
SAE AIR-737E - Hydraulic and Pneumatic Specifications and Standards.
SAE ARP-994 - Design of Tubing Installations for Aerospace Fluid Power Systems.
SAE AIR-4003 - Turbine Engine Containment.
SAE AIR-1083B - Airborne Hydraulic and Control System Survivability for Military Aircraft.
SAE AIR-1899 - Aircraft Hydraulic System Characteristics.
SAE AIR-1918 - Comparison of Hydraulic System Cleanliness Procedures and Requirements for Ten Aerospace Companies.
SAE ARP-24B - Determination of Hydraulic Pressure Drop.
SAE ARP-490E - Electro-Hydraulic Servovalves.
SAE ARP-1280A - Aerospace Application Guide for Hydraulic Power Transfer Units.
SAE ARP-1281B - Actuators: Aircraft Flight Controls, Power Operated, Hydraulic, General Specification.
SAE ARP-4379 - Accumulator, Hydraulic, Cylindrical Aircraft.
SAE ARP-4752 - Aerospace - Design and Installation of Commercial Transport Aircraft Hydraulic Systems.
FAA Order 8000.40D - Maintenance of Pressure Cylinders in Use as Aircraft Equipment.
61. SECTION 25.1438 PRESSURIZATION AND PNEUMATIC SYSTEMS.
a. Rule Text.
(a) Pressurization system elements must be burst pressure tested to 2.0 times, and proof pressure tested to 1.5 times, the maximum normal operating pressure.
(b) Pneumatic system elements must be burst pressure tested to 3.0 times, and proof pressure tested to 1.5 times, the maximum normal operating pressure.
(c) An analysis, or a combination of analysis and test, may be substituted for any test required by paragraph (a) or (b) of this section if the Administrator finds it equivalent to the required test.
[Amdt. 25-41, 42 FR 36971, Jul. 18, 1977]
b. Intent of Rule. This rule provides standards for the tests that must be conducted to demonstrate that pneumatic and pressurization ducting and components will not fail in normal operation. The rule was originated to address the pneumatic system, from the engine bleed port(s) to the pressure regulating and/or shut-off valve, and the pressurization system, which comprises all ducting and components of the air distribution system downstream of the abovementioned valve.
c. Background. This subject was not addressed in either part 4b of the Civil Air Regulations (CAR) or part 25 of Title 14, Code of Federal Regulations (14 CFR) when it was originally codified. The reason for proposing the new standards was: "Components (such as ducts and couplings) of pressurization and pneumatic systems have failed at an unacceptable rate in service. The proposed standards for these components have been effective in preventing design deficiencies in the past."
(1) Harmonization. This regulation is the subject of a Federal Aviation Regulations/Joint Aviation Requirements (FAR/JAR) harmonization effort under the Aviation Rulemaking Advisory Committee (ARAC). The ARAC working group may recommend a revised § 25.1438/JAR 25.1438 and JAR 25X1436, and may develop an accompanying new advisory circular.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information.
(1) Pneumatic Versus Pressurization System Identification: The following policy was extracted from an FAA letter dated October 19, 1993, in response to questions regarding § 24.1438 and the difference between pressurization system elements and pneumatic system elements.
(a) Section 25.1438(a) states: "Pressurization system elements must be burst pressure tested to 2.0 times, and proof pressure tested to 1.5 times, the maximum normal operating pressure," and § 25.1438(b) states: "Pneumatic system elements must be burst pressure tested to 3.0 times, and proof pressure tested to 1.5 times, the maximum normal operating pressure."
(b) The FAA considers the pneumatic system to include all air supply elements from the bleed port on the engine to the pressure regulating and shutoff valve. Pressurization system elements are all other elements in the air distribution system.
(c) The burst pressure test requirement for pneumatic and pressure system elements has been used to demonstrate that high pressure air will be contained within the system or element. The element is not required to function during or after the burst pressure test, but pressurized air must be contained within the element or system. The proof pressure test is used to demonstrate that pneumatic and pressure system elements can function after a higher than normal pressure (1.5 times the maximum normal operating pressure) is introduced into the element or system.
(d) Section 25.1438(c) allows the applicant to use an analysis as a method of showing compliance to the burst and proof pressure test requirement in §§ 25.1438(a) & (b).
e. References. None.
62. SECTION 25.1439 PROTECTIVE BREATHING EQUIPMENT.
a. Rule Text.
(a) If there is a class A, B, or E cargo compartment, protective breathing equipment must be installed for the use of appropriate crewmembers. In addition, protective breathing equipment must be installed in each isolated separate compartment in the airplane, including upper and lower lobe galleys, in which crewmember occupancy is permitted during flight for the maximum number of crewmembers expected to be in the area during any operation.
(b) For protective breathing equipment required by paragraph (a) of this section or by any operating rule of this chapter, the following apply:
(1) The equipment must be designed to protect the flight crew from smoke, carbon dioxide, and other harmful gases while on flight deck duty and while combating fires in cargo compartments.
(2) The equipment must include-
(i) Masks covering the eyes, nose, and mouth; or
(ii) Masks covering the nose and mouth, plus accessory equipment to cover the eyes.
(3) The equipment, while in use, must allow the flight crew to use the radio equipment and to communicate with each other, while at their assigned duty stations.
(4) The part of the equipment protecting the eyes may not cause any appreciable adverse effect on vision and must allow corrective glasses to be worn.
(5) The equipment must supply protective oxygen of 15 minutes duration per crewmember at a pressure altitude of 8,000 feet with a respiratory minute volume of 30 liters per minute BTPD. If a demand oxygen system is used, a supply of 300 146
liters of free oxygen at 70 o F. and 760 mm. Hg. pressure is considered to be of 15-minute duration at the prescribed altitude and minute volume. If a continuous flow protective breathing system is used (including a mask with a standard rebreather bag) a flow rate of 60 liters per minute at 8,000 feet (45 liters per minute at sea level) and a supply of 600 liters of free oxygen at 70 o F. and 760 mm. Hg. pressure is considered to be of 15-minute duration at the prescribed altitude and minute volume. BTPD refers to body temperature conditions (that is, 37o C., at ambient pressure, dry).
(6) The equipment must meet the requirements of paragraphs (b) and (c) of § 25.1441.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-38, 41 FR 55468, Dec. 20, 1976]
b. Intent of Rule. The intent of this rule is for the protective breathing equipment (PBE) provisions to protect crewmembers from the effects of hazardous gasses and smoke, either while on flight deck duty or combating a fire, if there is a class A, B, or E cargo compartment or an isolated compartment in which crewmembers are permitted access during flight. This rule does not address passenger protective breathing equipment. Section 25.1439(b) contains wording that requires PBE if required "by any operating rule of this chapter. . . " There are two technical standard orders (TSO) providing standards for approval of PBE. Technical Standard Order, TSO-C99, provides standards for use by flight crewmembers while on flight deck duty. Per the TSO, the PBE must provide eye protection in addition to preventing inspiration of smoke/fumes.
The flightcrew supplemental oxygen system can provide this via a full face mask with a setting that provides a positive pressure differential between the mask and ambient pressure in the cockpit to prevent smoke/fumes from entering the mask. If the crew supplemental oxygen system is equipped with an oro-nasal type mask (covers nose and mouth only) rather than a full mask, the eye protection can be achieved via a pair of goggles located within easy reach. This type of equipment is intended for use by flight crewmembers at their stations for a prolonged length of time. It would not generally be acceptable for firefighting since the crewmember's ability to reach the fire would be limited by the amount of extra oxygen tubing provided by the stationary system. TSO-C116 provides standards for PBE to be used by crewmembers while locating and fighting a fire. Per the TSO, it also provides head and shoulder protection from "drippings," and typically provides protective oxygen for 15 minutes. This type of PBE would not be suitable for use by the flightcrew at their stations.
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). Many of the requirements in section 4b.651 of the CAR were carried over essentially unchanged to § 25.1439 of 14 CFR. Part 25 standards state that PBE must be installed “if there is a class A, B, or E cargo compartment.”
(1) Amendment 25-38 (December 20, 1976) added the requirement that PBE be installed in each isolated separate compartment, including upper and lower lobe galleys, in which crewmember occupancy is permitted during flight for the maximum number of crewmembers expected to be in the area.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information.
(1) Protective Breathing Equipment Usage When Approved Under TSO-C99 and TSO-C116. The following policy, extracted from an FAA letter dated May 13, 1993, clarifies compliance with the requirements of § 25.1439 using equipment of the "smoke hood" variety approved under TSO-C116.
(a) The FAA letter clarified whether smoke hood type PBE would be acceptable for meeting the requirements of § 25.1439. The FAA is not aware of any smoke hood type PBE being approved as meeting the requirements of § 25.1439(b)(3), which relates to the use of radio equipment by the flight crew. The FAA would consider a smoke hood type PBE if compliance with § 25.1439(b)(3) is demonstrated.
(b) The FAA letter also clarified that a finding of equivalent safety would be required if an applicant wishes to use a “breathable gas,” in lieu of providing oxygen as specified in § 25.1439(b)(5).
(c) The FAA letter also addressed § 25.1439(b)(6), which specifies that there must be a means provided to allow the crew to readily determine the quantity of oxygen available.
PBE approved in accordance with TSO-C116 may or may not have such features. The FAA does not grant exemptions for the cases where the PBE is used by the flight crewmembers while on flight deck duty. When the PBE is intended for use in locating and combating a fire, the FAA will approve equipment which, when the container is intact, is considered to have a full charge of oxygen or, for chemical oxygen generation, the canister has not been activated. The container is "tamper evident" and the crewmember can readily determine that the equipment is fully charged and ready for use. This PBE would not be suitable for approval in meeting the flight crewmember requirements addressed by § 25.1439.
(d) The letter provided an FAA position on PBE requirements for the first and second observers. The FAA treats the first observer and second observer differently. The first observer must have the same protection, i.e., the same equipment, as the flight crewmembers.
The second observer may be supplied with oxygen equipment suitable for passengers. Again, the first observer must have the same protection (including the ability to communicate on the crewmember interphone) that is provided for the flight crewmembers; the second observer may be provided with passenger-type oxygen equipment.
(2) Protective Breathing Equipment Serviceability. The following policy was extracted from an FAA memorandum dated March 9, 1990, to provide guidance regarding the approval of PBE which met the requirements of § 121.337 and FAA Action Notice 8150.2.
(a) Section 121.337 was revised in 1987 and, in part, incorporated the intent of § 25.1439 and expanded on those requirements. This revision resulted in a new type of PBE for 148