Amendment 23-34 and Subsequent
This change added requirements for commuter category airplanes. The explanation in NPRM 83-17 states the following: “SFAR 41, Sec. 7(b) and (c), and Secs. 91.56 and 135.170 of the FAR.”
23.855 Cargo and baggage compartment fire protection
The corresponding rule in CAR 3 is CAR 3.392.
There is no corresponding rule in the Airship Design Criteria.
Amendment 23-49 and Subsequent
A proposed revision to NPRM 94-21 explains this rule as follows:
“Proposed paragraph (a) would require all sources of heat within each cargo and baggage compartment that are capable of igniting the compartment contents to be shielded and insulated to prevent such ignition.
Proposed paragraph (b) would require cargo and baggage compartments to be constructed of materials that meet the appropriate provisions of Sec. 23.853(d)(3).
Currently these requirements apply to commuter category airplanes and to the materials used in the compartments of these airplanes. The proposed new requirement would expand this applicability to the cargo and baggage compartments of all part 23 airplanes. In effect, the proposed new requirement would require materials that are self-extinguishing rather than flame resistant as currently required under Sec. 23.787(d).
Proposed new paragraph (c) would add new fire protection requirements for cargo and baggage compartments for commuter category airplanes. The proposed rule would require on of the following alternatives: (1) Either the compartment must be located where pilots seated at their duty station would easily discover the fire or the compartment must be equipped with a smoke or fire detector system to warn the pilot's station. The compartment must also provide access to the compartment with a fire extinguisher. (2) The compartment may be inaccessible, but must be equipped with a fire detector system that warns the pilot station, and the compartment must have ceiling and sidewall floor panels constructed of materials that have been subjected to and meet the vertical self-extinguishing tests of Appendix F of this part.
(3) The compartment must be constructed and sealed to contain any fire.
The proposed new section is necessary for several reasons. The proposals for additional requirements for commuter category airplane cargo and baggage compartments were developed after an examination of reported incidents of inflight fires and their causes. Although most of these incidents of inflight fires occurred on transport category airplanes, the reported sources of the fires showed that the fires originate from sources, such as matches in the pockets of clothing, that are as likely to be found on part 23 airplanes as on transport category airplanes. The same potential for inflight fires exists on commuter category airplanes and adequate protection should be provided.”
See guidance for § 23.853.
All-Cargo or Combination Passenger/Cargo Operations
Special conditions will be required for airplanes approved for all-cargo or combination passenger/cargo operations because 14 CFR, part 23, does not have applicable airworthiness standards for these operations.
23.859 Combustion heater fire protection
The corresponding rule in CAR 3 is CAR 3.388.
There is no corresponding rule in the Airship Design Criteria.
Amendment 23-5 and Subsequent
A proposed revision to NPRM 65-43 explains this amendment as follows:
“Secs. 23.859, 25.859, 27,859, and 29,859 would be amended to clarify, without changing, the conditions under which the "means independent of the components provided for the normal continuous control of combustion heater air temperature, airflow, and fuel flow" must be provided. The intent of this requirement is to require independent means of control when any one of the listed conditions exists.”
Amendment 23-27 and Subsequent
This rule was changed with the following explanation in Docket 20052: “The design complexity and operational altitude and weather capability of current Part 23 pistonpowered airplanes may necessitate installation of combustion heaters for occupant survival and airplane heating to counteract windshield icing conditions. Part 25 presently contains updated type certification requirements for combustion heater fire protection that are applicable regardless of the size of airplane in which the heater is installed. Among these requirements are those for fireproof air ducts and protection of the ventilating airstream from backfire and reverse burning, as recommended by the NTSB for inclusion in Part 23. In addition, Part 25 designates fire zones, requires fire detection means, contains heater control requirements, sets forth air intake location standards, gives heater exhaust requirements, and provides for fuel system protection and drainage. These requirements constitute the necessary minimum safety standards for combustion heater fire protection for any highperformance airplane.
Because of the increasing sophistication of normal category small airplanes and the expanded operating environment for which they are designed and used, the FAA has determined that more stringent type certification fire protection and detection standards are needed for combustion heaters when such heaters are installed in these airplanes. In view of the technical similarities between these airplanes and airplanes designed to Part 25 standards, the Part 25 standards for combustion heater fire protection are substantially adopted as type certification requirements for Part 23.”
23.863 Flammable fluid fire protection
There is no corresponding rule in CAR 3.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 4.40.
Amendment 23-23 and Subsequent
Those areas where ignition sources and flammable fluids are present must be designated as flammable fluid zones, and measures must be taken to minimize the likelihood of ignition sources and leakage being present. This is followed by a means to minimize the effects once a fire has occurred by extinguishing, ventilation, isolation, and drainage. The rule does not go so far to make the entire airplane a “designated fire zone.”
Fire detection and extinguishing is believed to be impractical for many part 23 airplanes. Where fire detection and extinguishing means might be impractical, the back up provisions could, for example, consist of a means to limit fluid leakage and fireproofing or isolation of critical parts. Therefore, compliance with § 23.863 could be accomplished with a means to limit fluid leakage, minimizing the likelihood of ignition, fireproofing or isolating critical parts. Minimization of ignition requires that equipment where a single failure can cause flammable fluid leakage, be tested to the explosion proof standards in RTCA/DO-160.
If a finding is made that either flammable fluids or vapors cannot escape into an area containing a potential ignition source, or if the fluids are nonflammable, this rule would not apply to that area. Design measures could support the finding such as:
either (1) shrouding (sealing off) of all potential ignition sources, or (2) shrouding or sealing off all flammable fluid/vapor sources. In either case, it should be discovered the means would continue to serve its function following any single failure of the system or component it is isolating from the area.
23.865 Fire protection of flight controls, engine mounts, and other flight structure
There is no corresponding rule in CAR 3.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 4.41.
Amendment 23-14 and Subsequent
A proposed revision to NPRM 71-13 explains this rule as follows: “Experience has indicated the need to ensure that flight controls and flight structure in powerplant fire zones remains operable in the event of a fire. The proposal requires this.”
Amendment 23-45 and Subsequent
A proposed revision to NPRM 90-18 added “engine mounts” to the rule with the following explanation: “This proposal clarifies existing Section 23.865 by excluding those portions of the engine mount certificated with the engine from this section.
Additionally, a clarification is provided to address the allowable damage expected on engine isolators.”
The engine mounts refer to the aircraft structure for mounting the engine and not the mount pads or attachment points, which are integral parts of the engine.
The intent of the regulations on engine mounts is the engine remains in place with a fire heating an engine mount. We do not intend to cover the case of a general conflagration where the entire engine compartment is burning. Therefore, an applicant should design enough load paths for the engine to remain in place with a localized fire.
For purposes of this rule, landing gears are not considered to be flight structures, so fireproofing or shielding landing gears are at the option of the manufacturer.
Shielding made from fireproof materials in part 23, § 23.1191(h), may be used without flame testing. While the shielding may be made of fireproof materials that do not require testing, means of installing the shielding such as sealers and adhesives should be shown not to reduce the efficacy of the shielding. Shielding materials subject to corrosion should be appropriately protected. Shielding need not be fireproof if it protects the enclosed structure to an extent equivalent to the enclosed structure being fireproof by itself.
The effectiveness of such shielding or fireproof materials should be determined by subjecting the shielded or fireproof structure, or control, to flammability testing as defined in AC 23-2, “Flammability Tests.” Before removal of the flame at the end of the test, loads should be applied to the shielded structure or control to show 163
that it can withstand the loads expected to occur during completion of the flight.
These loads can be treated as ultimate loads. Without a more rationale determination of the expected flight loads, a load factor of 70 percent of maneuver load or 40 percent of gust load is superposed with the loads from the engine thrust and torque for maximum continuous power. After five minutes and until the end of 15 minutes the engine may be assumed to be shutdown.
Amendment 23-48 and Subsequent
Policy on compliance of 14 CFR, part 23, § 23.865 at Amendment 23-48 for Structures in Adjacent Areas Subjected to Effects of Fire in Designated Fire Zones
The revision of 14 CFR, part 23, § 23.865 at Amendment 23-48 includes:
- changing the words “engine compartment” to “designated fire zones” for consistency with §§ 23.1181 and 23.1203; and
- adding the phrases “adjacent areas that would be subjected to the effects of fire in the designated fire zones.”
The intent of this section in the rules is to require the materials and components, in the designated fire zone, that are essential to flight safety: 1) be fabricated either from a material meeting defining fireproof under Title 14, part 1.1, or 2) be shown capable of maintaining their integrity or performing their function under the conditions of fire at least as well as steel. The intent of this section is also to require that materials and components, in adjacent areas to a designated fire zone, that are essential to flight safety, be capable of: 1) maintaining their integrity or 2) performing their function under the conditions of fire in the designated fire zone.
The fire condition characterized by a 2000-degree Fahrenheit (F) flame can be treated as a failure condition that should not prevent continued safe flight and landing for at least 15 minutes. The rule requires the structures (composite and metallic) behind the firewall and subjected to the heat effects of the fire be able to withstand the flight loads expected to occur during completion of the flight. It also requires these flight loads to not be less than the gust loads expected to be encountered during the completion of the flight. These loads can be treated as ultimate loads. Design features, including multiple load path arrangement, can be considered when establishing the remaining structural capacity. Freedom from flutter and whirl mode should also be shown.
Compliance with this requirement must be shown by tests, or by analysis supported by tests. Assessing heat effects needs to include all heat transfer mechanisms that may occur. For composite structure, the long-term environmental effects that may degrade the mechanical properties of the 164
structures also need to be considered. These may include the effects due to moisture and steam pressure.
EASA AMC 23.865 is acceptable for FAA certification.
ELECTRICAL BONDING AND LIGHTNING PROTECTION
23.867 Electrical bonding and protection against lightning and static electricity
There is no corresponding rule in CAR 3.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 4.42.
Amendment 23-7 and Subsequent
A proposed revision to NPRM 67-14 explains this rule as follows: “Small airplane operations involving potential exposure to lightning strikes are increasing. The hazardous effects of lightning on aircraft are well known. Economically practical means of protecting aircraft from such effects have been under study for several years. In order to prevent undue dictation of design, and yet, on the other hand, avoid an unnecessarily vague standard, this proposal summarizes the design objectives derived from the studies and experience obtained in the field of lightning protection of aircraft structures.”
Lightning protection of Visual Flight Rules (VFR) airplanes was considered because there is a possibility that a lightning strike on a VFR airplane could occur. However, the probability and consequences of a VFR lightning strike are more relevant than the possibility. The hundreds of millions of hours of service history on metallic airplanes illustrate neither a probability nor a consequence worthy of requiring the customer’s assets be spent on lightning certification of this class of airplane. Therefore, this section is not applicable to VFR-only airplanes that have electrical-bonding characteristics commensurate with metallic construction.
Protection of Composite Structure and Installed Equipment from the Direct and Indirect Effects of Lightning
Unless VFR-only airplanes, an applicant should submit a certification test plan describing the analyses/testing to be used to show lightning protection effectiveness.
At a minimum, the test plan should describe the sub-components, components, and systems to be tested and include:
a. Zone definition of the entire aircraft (show how this will be accomplished—strike attachment model tests and similar design).
b. Full scale or other acceptable means of simulated lightning qualification test on all flight critical portions of the airframe, flight controls, fuel, propulsion, electrical and avionics systems, including damage assessment procedures.
c. The indirect effect on the airplane and its systems after a direct lightning strike must also be evaluated. This will include both upset and damage assessment to the electrical and avionics systems.
d. Values for each phase of the protection should be drawn. This includes test procedures, test parameters, methodology, and simulation techniques to be used during the validation phase.
e. Grounding and bonding concerns are paramount in any aircraft but are more critical in composite structures. The test plan must address these areas and include life cycle environmental tests.
f. Lightning simulation methods including test voltages and current waveforms must be defined.
g. The test plan should address maintenance practices and repairs to the structure that ensure the continued lightning protection effectiveness.
The following SAE documents are applicable:
SAE ARP 5412, “Aircraft Lightning Environment and Related Test Waveforms,” November 1, 1999.
SAE ARP 5413, “Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning,” (being incorporated into an AC), May 14, 2002.
SAE ARP 5414, “Aircraft Lightning Zoning,” December 1, 1999.
SAE ARP 5415, “Users Manual for Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning,” May 14, 2002.
SAE ARP 5577, "Aircraft Lightning Direct Effects Certification,” September 30, 2002.
Amendment 23-49 and Subsequent
A proposed revision to NPRM 94-21 explains the change in the title of § 23.867 as follows: “This proposed revision would change the heading that precedes the section from "Lightning Evaluation" to "Electrical Bonding and Lightning Protection." It would also revise the section heading form "Lightning protection of structures" to "Electrical bonding and protection against lightning and static electricity." The proposed revisions more accurately clarify the content of the section.”
MISCELLANEOUS
23.871 Leveling means
The corresponding rule in CAR 3 is CAR 3.401.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 4.50.
Amendment 23-7 and Subsequent
The original rule required “reference marks.”
This amendment has the following explanation in NPRM 67-14: “any means, not just reference marks, are acceptable for leveling the airplane on the ground.”
Subpart F—Equipment
GENERAL
23.1301 Function and installation
The corresponding rules in CAR 3 are CAR 3.651 and 3.652.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 6.1.
Original Issue and Subsequent
When performing TSO testing to RTCA/DO-160, sections 16 and 17, the sentence “After exposure, DETERMINE COMPLIANCE WITH APPLICABLE EQUIPMENT PERFORMANCE STANDARDS” is considered to refer to the appropriate section of the RTCA Minimum Operational Performance Standards (MOPS) that references DO-160.
For a test section of a MOPS that is titled “Normal Operating Conditions,” the applicable equipment standards should be met while the test is being conducted. If the equipment experiences an interruption of operation as a result of the test, then the acceptability of the duration of the interruption will depend on the intended function of the equipment and must be justified.
Manual resets or pilot actions required to restore normal operation following any test must be explicitly permitted by the applicable TSO or MOPS. If the TSO or referenced MOPS does not specifically allow for a reset, then the equipment must continue to operate or resume normal operation without any pilot action.
Instruments and equipment installed to meet the requirements of 14 CFR, part 23, § 23.1303 and part 91, § 91.205 should meet the TSO requirements that are applicable for that instrument or equipment or equivalent requirements.
Amendment 23-7
A proposed revision to NPRM 67-14 explains this change as follows: “This proposal would remove the unnecessary distinction between radio and other equipment that now exists in Sec. 23.1301 (a) (2) and (3), and extend the provisions of Sec. 23.1431 to all equipment, not only radio equipment. There is no basis for distinguishing between radio and other equipment so far as general functioning requirements are concerned. The other changes are intended to bring the sections in closer conformity with the corresponding sections in Part 25 through 29, without substantive change.”