compartments classified as Class A, or with the cargo compartment classification not addressed at all.
(b) An FAA memorandum , dated September 13, 1988, states that " . . . the agency policy has always been, and still is, that cargo compartments larger than that stated in Order 8110.27A(5)(b) are to be classified as Class B through E, whichever is applicable, and that operators comply with all requirements relative to each class." The aforementioned order describes the Class A compartment as " . . . small open compartments used for storage of crew luggage and located in the cockpit area where a fire can be easily discovered by a crewmember."
The order goes on to state that: "During the 74/75 Airworthiness Review, it was mentioned that full cabins or other large cargo compartments were presented for approval under Class A category, and that these compartments were consistently rejected on the basis that their volume was outside the intent of the Class A category where a fire must be rapidly detected and extinguished. Since the Class A compartment has no liner, large cargo areas have been considered to be outside the intent of the Class A category. It was recommended to limit the volume to 200 cubic feet."
(c) Advisory Circular (AC) 25-18, issued January 6, 1994, Transport Category Airplanes Modified for Cargo Service, addresses this subject. In the AC, Class A compartments are defined as follows:
1 "A Class A compartment is one that is located so close to the station of a crewmember that the crewmember would discover the presence of a fire immediately. In addition, each part of the compartment is easily accessible so that the crewmember could quickly extinguish a fire with a portable fire extinguisher. A Class A compartment is not required to have a liner.
2 "Typically, a Class A compartment is a small open compartment in the cockpit area used for storage of crew luggage. A Class A compartment is not, however, limited to such use; it may be located in the passenger cabin and used for other purposes provided it is close to a crewmember's station. Typically, the crewmember would be a member of the flightcrew; however, the compartment could be located adjacent to the station of any other crewmember.
3 "Because a Class A compartment does not have a liner, it is absolutely essential that the compartment be small and located close enough to a crewmember that any fire that might occur could be discovered and extinguished immediately. Without a liner to contain it, an undetected or uncontrolled fire could quickly become catastrophic by burning out of the compartment and spreading throughout the airplane. There is no specific limit on the volume;
however, all portions of the compartment must be virtually within arms length of the crewmember in order for any fire to be detected immediately and extinguished in a timely manner. Although there may be some exceptions, such as a 'U-Shaped' compartment for example, a Class A compartment greater than 50 cubic feet in volume would not typically have the accessibility required by § 25.857(a)(2) for fighting a fire."
(d) Advisory Circular 25-17, Transport Airplane Cabin Interiors Crashworthiness Handbook, dated July 15, 1991, or latest revision, notes that a Class A compartment was envisioned as a small, open compartment located in the cockpit area.
(e) It is clear from reviewing the above policy, and noting the chronology, that the intent of Class A compartments is not consistent with the conversion of an entire passenger cabin to a cargo compartment and identifying it as Class A. A number of issues support this view. In order to exit the airplane in the event of an uncontrollable fire, the only path may be through the fire zone. Access to emergency exits often does not exist with the compartment fully loaded.
Further, there are no means to protect the flightcrew from the effects of toxic gasses that can be generated in a smoldering fire. In cargo compartments classified Class B through Class E, the cargo and crew areas are separated and certification tests are conducted to ensure that no hazardous quantities of smoke or fumes will penetrate occupied areas, including the cockpit. In addition, other factors that are frequently not addressed in these modifications are: lack of a cargo restraint system, compartment liners, and a second emergency exit.
(f) The FAA has determined, for the reasons discussed above, that it is inappropriate to classify full cabin or other large areas as Class A compartments. For future certification projects (whether new, amended, or supplemental), the above guidance must be considered.
(3) Class E Cargo Compartments. The following policy is extracted from an FAA memorandum dated March 21, 1991, in response to a request for guidance on compliance relating to the installation of a Class E cargo compartment.
(a) Smoke detection capability must be demonstrated in any flight condition contemplated by the operator. This usually means a flight test must be performed at the maximum contemplated cabin altitude.
(b) Smoke penetration from Class E compartment into cockpit tests must be conducted starting in a cruise configuration and continuing into a descent to sea level landing. If any other procedures, such as attempting to suppress the fire by going to higher altitudes, involve other operating altitudes, these must also be addressed.
(c) An Airplane Flight Manual (AFM) supplement is needed which addresses crew action following smoke annunciation, i.e., crew shuts off ventilating air to the cargo compartment, dons oxygen equipment, and proceeds to the nearest adequate airport.
(d) The protective breathing equipment requirement in § 25.1439(a) must be addressed.
(4) Access to Class E Cargo Compartments. The following policy is extracted from an FAA letter dated July 3, 1990, in response to a request for guidance on compliance on the carriage of dangerous goods, and the need for access, in Class E compartments.
(a) The International Civil Aviation Organization regulations for hazardous goods carried in Class E compartments require adequate access to these goods. Section 25.857 of 14 CFR does not preclude access to Class E compartments in flight. Sections 25.851(a)(3) and
121.309(c)(2) require that one hand fire extinguisher must be provided for use in each Class E cargo compartment that is accessible to crewmembers in flight.
(b) Although part 25 does not require in-flight access to Class E cargo compartments, in-flight access to the compartment can be accommodated with proper design if operational requirements result in the carriage of hazardous goods in a Class E compartment.
(5) Freighter Aircraft with Accessible Class E Compartment. The following is extracted from an issue paper dated March 10, 1995, titled “Accessible Class E Cargo Compartment.”
(a) The following applies to certification of a freighter aircraft with an accessible Class E Cargo Compartment, which would allow the operator to carry hazardous material. The following would allow the crew and "persons" access to the entire cargo compartment.
(b) Access by one cargo handler will be allowed during flight to a Class E cargo compartment carrying hazardous material provided that one Portable Breathing Equipment (PBE) meeting TSO C-116 is available in the flight deck. The cargo handler in the Class E cargo compartment must carry the portable oxygen at all times while in the cargo compartment. A placard must state that the portable oxygen must be carried at all times. In addition, there must be a readily detectable means to alert the cargo handler to don oxygen equipment and/or return to the flight deck. Further, two Halon fire extinguishers of adequate size must be installed near the cargo compartment entrance with procedures for their use. Finally, there must be a means to prohibit smoking. Compliance with the above will meet §§ 25.855(e)(1), (e)(2), and
25.857(e)(4), taking into consideration the opening caused by a person exiting the cargo compartment.
(c) The applicant should show by test or by analysis that with the access door open in flight the positive ventilation with only one pack operating is capable of excluding smoke, flames, or noxious gasses in compliance with § 25.857(e)(4). In addition, the additional fire extinguisher that was kept on the flight deck was required to be a 16-pound Halon extinguisher to comply with § 121.309(c)(2).
e. References. The addresses for ordering the latest revision of referenced documents listed below can be found in the Appendix to this AC.
Advisory Circular, 25-XX, Cargo Compartment Fire Extinguishing or Suppression Systems, date TBD.
Advisory Circular, 25-XX, Class B and F Cargo Compartments, date TBD.
Two methods of determining the leakage rate for Class D compartments that have been approved for certification are contained in:
Appendix I of CAA Technical Development Report No. 146, Evaluation of Flight Fire Protection Means for Inaccessible Aircraft Baggage Compartments, dated June 1951, and FAA Technical Center Report DOT/FAA/CT-83/1, Analysis of Dissipation of Gaseous Extinguisher Agents in Ventilated Compartments, dated May 1983.
39. SECTION 25.858 - CARGO OR BAGGAGE COMPARTMENT SMOKE OR FIRE DETECTION SYSTEMS.
a. Rule Text.
If certification with cargo or baggage compartment smoke or fire detection provisions is requested, the following must be met for each cargo or baggage compartment with those provisions:
(a) The detection system must provide a visual indication to the flight crew within one minute after the start of a fire.
(b) The system must be capable of detecting a fire at a temperature significantly below that at which the structural integrity of the airplane is substantially decreased.
(c) There must be means to allow the crew to check in flight, the functioning of each fire detector circuit.
(d) The effectiveness of the detection system must be shown for all approved operating configurations and conditions.
[Amdt. 25-54, 45 FR 60173, Sep. 11, 1980; Amdt. 25-93 63 FR 8032, Feb. 17, 1998]
b. Intent of Rule. This rule provides minimum design and certification requirements for cargo or baggage compartment fire or smoke detection systems. This rule is intended to provide a standard that a fire be detected and indicated to the crew in less than one minute after inception.
c. Background. This section was added to part 25 of the Code of Federal Regulations (14 CFR) with Amendment 25-54. Prior to Amendment 25-54, a detection limit of no more than five minutes was established by policy since there was no regulatory reference to detection time.
Section 25.858(d) requires detection testing in any configuration proposed by the applicant, including depressurized flight. The cognizant ACO may certify minor changes by analysis of similarities to previously certified configurations, laboratory test, or ground test.
(1) Amendment 25-93 (February 17, 1998) revised the section heading and introductory paragraph to add reference to baggage compartments and smoke detection systems.
d. Policy/Compliance Methods. For guidance on compliance with this requirement, refer to the preamble of this rule and the following information.
(1) Smoke Detection Certification Testing. The following policy is extracted from an FAA memorandum dated June 18, 1997, which was developed in response to inquiries regarding smoke quantities to certify smoke detection systems in cargo compartments. The memo was used to distribute video guidance to help clarify smoke quantities specified in Advisory Circular (AC) 25-9A.
(a) Section 25.858(a) requires that a cargo compartment fire detection system provide a visual indication to the flightcrew within one minute after the start of a fire. AC 25-9A, section 10, provides guidelines for the conduct of certification tests related to smoke detection. The AC states that systems which provide a warning within one minute from the start of smoke generation are considered to be in compliance with the requirements of § 25.858 for cargo compartments.
Paragraph 10.b. states that the objective of the smoke detection test is “to demonstrate that the smoke detection system installation will detect a smoldering fire producing a small amount of smoke.”
(b) In February 1997, FAA/Industry meetings were held to discuss how manufacturers and operators intended to support the part 25 and 121 rule changes requiring fire detection and suppression systems to be installed in existing Class D cargo compartments. During the meeting, Industry expressed concern that a large number of conversions were going to be made and several Aircraft Certification Offices (ACO’s) would be impacted. Industry was concerned that the smoke detection standards used by the ACO’s varied and requested the FAA’s effort to standardize the test criteria used to satisfy § 25.858.
(c) In response to this request, the FAA held a standardization workshop at the FAA Technical Center in Atlantic City, NJ, during April 1997. ACO personnel and designated engineering representatives (DER’s) attended to discuss smoke generation and quantities, and other certification requirements relevant to cargo compartments requiring both detection and suppression systems.
(d) During the standardization workshop, the Technical Center provided a demonstration of a typical smoke quantity from a smoldering fire by igniting rags inside a suitcase.
There was a consensus agreement among the ACO members present that this suitcase demonstration generated an appropriate quantity of smoke for a one minute detection system. It was agreed that a video of the burning suitcase should be distributed to the ACO’s as an aid to visually demonstrate the amount of smoke that is representative of smoke from a smoldering fire as is mentioned in AC 25-9A. This video is considered visual guidance demonstrating a typical amount of smoke from a smoldering fire. The amount of smoke demonstrated in this video helps to clarify the objective of paragraph 10.b. in AC 25-9A.
(e) Copies of the video mentioned above are available through the FAA William J.
Hughes Technical Center. Refer to the Appendix of this AC for the mailing address.
(f) Additional items of discussion at the workshop included the following:
1 The tests conducted at the FAA Technical Center have shown that some materials that are routinely carried in cargo compartments burn very quickly with open flames 109
and little smoke. It was shown that a fire internal to a suitcase can rupture an aerosol can (containing butane, propane, or isobutane) contained therein and cause the liner to be breached.
Once the liner is breached, ventilation control and ability to maintain adequate Halon concentration will be lost. It is inappropriate to rely on detection systems that depend on copious quantities of smoke prior to detection. A fire does not know what volume compartment it is in.
A smoldering fire will generate the same levels of smoke regardless of the compartment size and should be detected within the required time to detection (one minute or five minutes as applicable) in any compartment. The solution to larger compartments may be an increased number of detectors, increased sensitivity of detectors, different type of detectors (fanned or ionic), or infrared detectors.
2 All of the current smoke detection limits and guidance have been subjective and based on previous certification practices. The FAA Technical Center's planned test program includes defining fire hazards, the amount of heat generated, and the typical quantity (in more objective terms) of smoke generated, associated with typical cargo fire hazards. The suitcase video is intended to provide clearer guidance until the Technical Center test program is complete. It is a continuing step toward standardizing the approach to smoke detection testing until the FAA determines usable, objective criteria.
(2) Certification Testing for Smoke Detection. The following policy is extracted from an FAA memorandum dated February 11, 1993, in response to an inquiry regarding certification of smoke detection systems in the cargo compartments of transport category airplanes, and provides guidance for determining detection times for these systems.
(a) Advisory Circular (AC) 25-9 and AC 25-17, differ in the guidance provided for time to detection for certification testing. AC 25-9 states in paragraph 7.e.(3) that "smoke detection should occur within one minute after the start of smoke generation." AC 25-17 states in paragraph 671.b.(6) that "An acceptable detection time for smoke detectors is 5 minutes. Use the smoke quantity and location criteria of AC 25-9, 'Smoke Detection, Penetration, and Evacuation Tests, and Related Flight Manual Emergency Procedures,' for showing that the smoke detection system detects a fire in satisfactory time. The time for fire detection systems was changed to one minute by Amendment 25-54 in § 25.858."
(b) The guidance contained in AC 25-9 reflects the detection times required in Amendment 25-54, which added § 25.858. This section established a higher standard of safety than previously existed for transport category airplanes, and applies to airplanes which have Amendment 25-54 in their certification basis. When an applicant applies for an amended or supplemental type certificate to convert a passenger configuration to a cargo configuration on an older airplane whose certification basis predates Amendment 25-54, the allowable maximum detection time is not specifically stated in 14 CFR. The five minute detection time, which is not mentioned in AC 25-9, was established in an FAA letter in 1965, and has been the accepted maximum detection time requirement until § 25.858 became effective on September 11, 1980.
(c) If an applicant applies for an amended or supplemental type certificate and the certification basis for the airplane predates Amendment 25-54, there is no regulatory basis for 110
requiring a detection time of one minute. The applicant should be encouraged to meet the later amendment, or to make detection within one minute a design goal, but it would be inappropriate to require that the applicant comply with § 25.858.
(d) Two additional points should be made regarding wording in regulations that address fire detection systems. When the terms "fire detector" or "fire detection system" are used, this also encompasses smoke detectors and smoke detection systems. A review of the preamble to Amendment 25-54 reveals that the rule is intended to address systems which detect fires, and smoke detection systems were included. Also, questions are frequently asked regarding the expression that detection must occur "within one minute after the start of a fire."
As noted in AC 25-9, time to detection is measured "after the start of smoke generation."
Therefore, detection time is defined as the elapsed time from when the smoke generator is activated (switched to the mode which actively generates smoke) to when detection occurs (annunciation of smoke detection to the flight crew).
(3) Smoke Detection Certification Testing. The following policy is extracted from two FAA letters dated December 3 and December 15, 1992. The letters were in response to a request for approval of five items discussed in a meeting between the FAA and an applicant on November 6, 1992, all related to "Smoke Detection Testing Methodology/Procedures For Compliance To § 25.858."
(a) The five items below were discussed individually. It was noted prior to responding that the positions provided in the letter related to demonstration of compliance with the provisions of § 25.858, as promulgated by Amendment 25-54, and were not intended to provide guidance as to methods to be used for certification of an airplane which does not have Amendment 25-54 in its certification basis. In addition, the responses provided were not intended to be all inclusive. Other methods of demonstrating compliance could also be acceptable.
(b) The first proposal related to a specific fuel load (using tobacco as the fuel), tamping, and lighting procedure to be used for generating smoke to show compliance with the FAA requirements. The procedure and the tobacco weights were proposed to meet the requirements in a large compartment such as in a large transport category all cargo airplane.
There were two charges (basket sizes) proposed. These two charges should be acceptable for all large transport category airplane cargo compartments. The FAA reserves the option to stipulate smaller fuel loads when finding compliance in small compartments.
(c) The second proposal discussed the use of a smoke deflector hat, which is required to provide a more realistic smoke propagation pattern than a direct smoke exhaust directed toward the crown of the compartment. The FAA had seen no evidence that a direct smoke stack exhaust provided a representative smoke pattern. It was stated that the deflector hat would continue to be required in future tests using a tobacco generator.
(d) The third proposal requested approval of continuous smoke generation until detection, and allowed "averaging" the detection times to give a one minute overall average for 111
all positions tested, with maximum time not to exceed 110 seconds at any location.
Section 25.858 states that detection must occur within one minute after the start of a fire. When § 25.858 was proposed, several commenters stated that the one minute detection time was too stringent, especially in light of the existing policy (5 minutes to detection). It was the opinion of the commenters that the technology was not available to enable the airplane manufacturers to meet the one minute requirement. The preamble to the final rule, issued as part of Amendment 25-54, noted that the technology was available or would be available when new airplanes affected by the rule were certificated. Subsequently, a number of airplanes have shown compliance with the one minute rule, indicating that the promulgators of the rule were correct in their assessment. The technology is available, and the FAA could not arbitrarily change that requirement to allow a fire to go undetected for 110 seconds in some locations in the cargo compartment. Such a finding would not be in accordance with the rule as issued. A rule change to allow longer detection times in special cases, such as for very large cargo compartments on all-cargo airplanes, would be required.
(e) The fourth proposal dealt with a means to reduce the number of locations at which smoke would be generated within the compartment to diminish the costs associated with flight testing new cargo compartment configurations. The proposal stated that smoke detection locations would be representative of high, low, and normal detection locations as documented in the applicant's tests. The certification locations were to be randomly selected from a population of representative locations. The number of representative test locations must be at least twice the number of required certification test locations and they must be available for FAA review.
Typically, laboratory and ground testing determine the worst locations in each part of the compartment. The random selection of flight test locations should be acceptable provided the whole population of ground test times is already compliant with the rule. The FAA determined that this approach was acceptable for demonstrating compliance with § 25.858, and also for testing on the applicant's airplane.
(f) The fifth proposal discussed the "Statistical Procedure and Methodology" for demonstrating compliance with § 25.858. The proposal to use an average detection time for all locations, with no tested location having a detection time exceeding 110 seconds, was not acceptable to the FAA. However, it was recognized that smoke testing is not a perfectly repeatable process, and testing at any one location may yield varying detection times with multiple tests. Previous certification tests have proceeded as follows: If the first test at a given location results in a detection time of greater than 60 seconds, the applicant must repeat the test two more times; if the resulting average of the three tests at the given location is 60 seconds or less, the given location is a “Pass;” if the resulting average of the three tests at the given location is greater than 60 seconds, the given location and the fire detection system are both “Failed” and require a redesign of the system.
(g) Two additional points were raised by the applicant. In the FAA response to the second proposal, paragraph (c) above, regarding the use of a smoke deflector hat on the smoke generator, the FAA noted that "...we will continue to require the deflector hat on future tests."
The applicant was concerned that this statement could lead to a misunderstanding regarding the use of the deflector hat on previous tests. The FAA had commented in previous correspondence 112
that the smoke generator tends to direct smoke toward the top of the compartment, which could result in earlier detection times than would be the case if a cargo fire actually occurred (the objective of the generated smoke is to simulate natural bouyancy, not necessarily the upward velocity). It was noted that there had been no certification tests conducted using the applicant's smoke generator with a deflector hat in place. However, a deflector hat was informally tested during a certification flight test, and the FAA decided to require the use of a smoke deflector for the tobacco generator for any future certification flight tests that involved demonstrating compliance with the provisions of § 25.858.
(h) The FAA noted in our response to the third proposal, paragraph (d) above, regarding approval of continuous smoke generation until detection and allowing "averaging" the detection times to give a one minute overall average for all positions tested, that " Such a finding would not be in accordance with the rule as issued." The applicant expressed the opinion that the § 25.858 wording "...within one minute after the start of a fire" was not adequately defined in the rule. Demonstration of compliance for smoke detection systems, whether the requirement is the previous 5 minute standard per policy or the 1 minute provision in § 25.858, has always been accomplished by measuring the time from smoke generator "ON" until detection. We did not anticipate any change in this policy. If this were not the case, the period of time during which the tobacco charge is being ignited with a torch would be included in the time for detection. For the tobacco generator, the "ON" time is when the tobacco basket is placed in the generator and the fan turned on. For a theatrical smoke generator, the "ON" time is when the switch is turned on. It is recognized that a theatrical smoke generator may have a built in time delay (by design) between the "switch on" event and when the smoke begins to exit; the cognizant ACO engineer needs to make that determination. Such a time differential may be negligible or not measurable.
(4) William J. Hughes Technical Center Research and Development. The FAA Technical Center is currently conducting a research and development (R&D) program to help standardize fire detection certification methods. When this R&D effort is complete, it is intended to revise AC 25-9A to provide more objective criteria for smoke/fire detection certification. The above Policy/Compliance Methods will be subject to change and/or incorporation into the revision to AC 25-9A in the future.
e. References. The addresses for ordering the latest revision of advisory circulars and other referenced documents listed below can be found in the Appendix to this AC.
AC 25-9A - Smoke Detection, Penetration, and Evacuation tests and related flight manual Emergency Procedures.
AC 25-17 - Transport Airplane Cabin Interiors Crashworthiness Handbook FAA Video, Smoke Quantities to Certify Smoke Detection Systems in Cargo Areas.
40. SECTION 25.863 - FLAMMABLE FLUID FIRE PROTECTION.
a. Rule Text.
(a) In each area where flammable fluids or vapors might escape by leakage of a fluid system, there must be means to minimize the probability of ignition of the fluids and vapors, and the resultant hazards if ignition does occur.
(b) Compliance with paragraph (a) of this section must be shown by analysis or tests, and the following factors must be considered:
(1) Possible sources and paths of fluid leakage, and means of detecting leakage.
(2) Flammability characteristics of fluids, including effects of any combustible or absorbing materials.
(3) Possible ignition sources, including electrical faults, overheating of equipment, and malfunctioning of protective devices.
(4) Means available for controlling or extinguishing a fire, such as stopping flow of fluids, shutting down equipment, fireproof containment, or use of extinguishing agents.
(5) Ability of airplane components that are critical to safety of flight to withstand fire and heat.
(c) If action by the flight crew is required to prevent or counteract a fluid fire
(e.g., equipment shutdown or actuation of a fire extinguisher) quick acting means must be provided to alert the crew.
(d) Each area where flammable fluids or vapors might escape by leakage of a fluid system must be identified and defined.
[Amdt. 25-23, 35 FR 5676, Apr. 8, 1970, as amended by Amdt. 25-46, 43 FR 50597, Oct. 30, 1978]
b. Intent of Rule. The intent of this rule is to minimize the probability of ignition of flammable fluid or vapor leakage in any area where they may exist and, in case of ignition, to 114
minimize the resultant hazard to the aircraft. The definition in 14 CFR 1.1 says "Flammable, with respect to a fluid or gas, means susceptible to igniting readily or to exploding. Examples are aviation jet fuel, hydraulic fluid, and oxygen. Hydraulic equipment, e.g., pumps are qualified per airplane and engine manufacturers' specifications, (SAE) industry standards and/or military standards addressing issues of bonding and grounding, flame and arc resistance, explosion proofing, dielectric strength and case drain temperature limits.
c. Background. For guidance on compliance with this requirement, refer to Advisory Circular (AC) 25-XX, Propulsion Systems Handbook, chapter 3, section 1.
d. Policy/Compliance Methods. For guidance with this requirement, refer to Advisory Circular (AC) 25-XX, Propulsion Systems Handbook, chapter 3, section 1. Section 25.1435(c), Hydraulic systems-fire protection, requires compliance with § 25.863.
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-XX, Propulsion Systems Handbook.
41. SECTION 25.869 - FIRE PROTECTION SYSTEMS.
a. Rule Text.
(a) Electrical system components:
(1) Components of the electrical system must meet the applicable fire and smoke protection requirements of 25.831(c) and 25.863.
(2) Electrical cables, terminals, and equipment in designated fire zones, that are used during emergency procedures, must be at least fire resistant.
(3) Main power cables (including generator cables) in the fuselage must be designed to allow a reasonable degree of deformation and stretching without failure and must be-
(i) Isolated from flammable fluid lines; or
(ii) Shrouded by means of electrically insulated, flexible conduit, or equivalent, which is in addition to the normal cable insulation.
(4) Insulation on electrical wire and electrical cable installed in any area of the fuselage must be self-extinguishing when tested in accordance with the applicable portions of Part I, appendix F of this Part.
(b) Each vacuum air system line and fitting on the discharge side of the pump that might contain flammable vapors or fluids must meet the requirements 25.1183 if the line or fitting is in a designated fire zone. Other vacuum air systems components in designated fire zones must be at least fire resistant.
(c) Oxygen equipment and lines must-
(1) Not be located in any designated fire zone,
(2) Be protected from heat that may be generated in, or escape from, any designated fire zone, and 115
(3) Be installed so that escaping oxygen cannot cause ignition of grease, fluid, or vapor accumulations that are present in normal operation or as a result of failure or malfunction of any system.
[Amdt. 25-72, 55 FR 29784, Jul. 20, 1990]
b. Intent of Rule. The intent of this rule is to minimize the probability of fire damage and to assure critical components of the electrical system, vacuum air system, and oxygen equipment and lines maintain the capability needed to complete safe flight and landing following a fire.
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). Section 4b.626 of the CAR became § 25.1359 of 14 CFR for electrical system fire and smoke protection; section 4b.658 of the CAR became §§ 25.1433(b) and 25.1433(c) of 14 CFR for vacuum air system line and fittings fire protection; and § 4b.651(f) of the CAR became § 25.1451 of 14 CFR for oxygen equipment and lines fire protection..
(1) Amendment 25-72 (July 20, 1990) consolidated all fire protection requirements for electrical, vacuum, and oxygen systems and transferred to § 25.869 “Fire protection: systems.”
Section 25.1359 became § 25.869(a) except for test acceptance criteria which was transferred to Appendix F. Sections 25.1433(b) and (c) were combined as §§ 25.869(b) and 25.1451 became § 25.869(c). Minor editorial changes were also made as necessary.
d. Policy/Compliance Methods: For guidance on compliance with this requirement, refer to the preamble of this rule and the following information. For policy and guidance on § 25.869(a), electrical system components, refer to Advisory Circular (AC) 25-16, AC 25-17 (section 25.1359, paragraph 781), and Appendix F to part 25. For policy and guidance on § 25.869(b), vacuum air systems, refer to the Propulsion Systems Handbook, section 25.1183.
For policy and guidance on § 25.869(c), oxygen equipment and lines, see paragraph 115. d.(3)(e) of this document and AC 25-17, section 25.1451, par 1011.
e. References. The address for ordering the latest revision of the advisory circulars listed below can be found in the Appendix to this AC.
AC 25-16, Electrical Fault and Fire Prevention and Protection.
AC 25-17, Transport Airplane Cabin Interiors Crashworthiness Handbook.