Appendix 3
a. Applicability. Section 26.33(a) states that this rule applies to “U.S. type certificated transport category, turbine-powered airplanes, other than those designed solely for all-cargo operations, for which the State of Manufacture issued the original certificate of airworthiness or export airworthiness approval on or after January 1, 1992, that, as a result of original type certification or later increase in capacity have:
(1) A maximum type-certificated passenger capacity of 30 or more, or
(2) A maximum payload capacity of 7,500 pounds or more.”
(1) The reference to the originally certificated capacity, or later increase in capacity, is intended to address two situations:
(a) In the past, some designers and operators have gotten design change approval for a slightly lower capacity to avoid applying requirements mandated only for airplanes over specified capacities. By referencing the capacity resulting from original certification, this rule removes this possible means of avoiding compliance.
(b) It is also possible that an airplane design could be originally certified with a capacity slightly lower than the minimum specified in this section, but through later design changes, the capacity could be increased above this minimum. The reference to later increases in capacity ensures that, if this occurs, the design would have to meet the requirements of this section.
(2) Maximum payload capacity is defined in 14 CFR 119.3, Definitions. Also see the reference in paragraph 4e(15) of this AC.
(3) Foreign Type Certificate Holders. This paragraph applies not only to domestic TC holders, but also to foreign TC holders. In this sense, this section is different from most type certification programs, where foreign applicants typically work with their responsible certification authority, and the FAA relies, to some degree, upon that authority’s findings of compliance under bilateral agreements. Since this rulemaking is not harmonized in all cases, the FAA will initially retain the authority to make all the necessary compliance determinations, and where appropriate, may request certain compliance determinations by the appropriate foreign authorities using procedures developed under the bilateral agreements. The compliance planning provisions of this section (discussed later) are equally important for domestic and foreign TC holders and applicants, and we will work with the foreign authorities to ensure that their TC holders and applicants perform the planning necessary to comply with the requirements of this section.
b. Flammability Determination and Service Instructions.
(1) Flammability Analysis. Section 26.33(b) requires holders of TCs for large transport category airplanes to submit a flammability exposure analysis for approval by the FAA oversight office by December 18, 2008. Section 26.33(b)(2) provides an A3-2
Appendix 3 exception to the flammability analysis requirement for fuel tanks for which the TC holder has notified the FAA that it will provide design changes and service instructions for an FRM or IMM meeting the requirements of § 26.33(c).
(2) Model Variations and Derivatives.
(a) Section 26.33(b) specifies that the flammability analysis must include “all fuel tanks defined in the type design, as well as all design variations approved under the type certificate that affect flammability exposure.” Design variations that may affect fuel tank flammability could include changing the fuel tank volume or usable fuel capacity, changes in the fuel management procedures, engine changes that might affect parameters such as airplane climb rate or bleed air available if needed by an FRM. Other examples of configuration differences that may affect fuel tank flammability exposure are provided in the discussion of § 26.35. It would also include all modifications and changes mandated by airworthiness directives (AD) that affect fuel tank flammability exposure as of the effective date of the rule. These ADs would only be those issued against any configurations developed by TC holders. This would include any ADs issued against modifications defined by a third party STC installed on affected airplanes. The result would be a configuration that is clearly understood by both industry and the FAA.
(b) An example of a design variation is an airplane certificated with the same model and series designation that could have different maximum takeoff gross weights, changes in fuel tank configuration or engine type or thrust, equipment installations, or passenger versus all-cargo carrying capabilities. Derivatives, in most cases, are those model airplanes that historically incorporate significant design changes from the original approved type design. In general, these derivative models would have to comply with later airworthiness standards for those areas incorporating the significant design changes. The derivative models are listed on the same TC data sheet with the original certificated model. Various segments of industry have also defined these changes as “variants.” For the purpose of this regulation, we consider the terms “derivatives” and “variants” to be synonymous.
(3) Service Instructions and Service Bulletins. If the flammability exposure analysis shows that the average exposure for any fuel tank exceeds 7 percent, § 26.33(c) requires the TC holder to develop design changes and service instructions for either FRM or IMM. Modifications incorporated into existing airplanes, including safety related changes (design and/or maintenance) that are mandated by AD, are typically made by operators using service instructions developed by the TC holders. These service instructions are commonly referred to as service bulletins. In this regulation, service instructions must contain sufficient information for the operator to incorporate the design change and any associated procedures and airworthiness limitations. They may include specific step-by-step procedures and information needed by the operator, such as parts lists, drawings, etc. Therefore, the paragraph requires TC holders to develop and submit for approval by the FAA, not just data defining a proposed design change, but a package of complete information that includes all of the information necessary to enable an operator to comply with the operational rules, discussed later. This information should A3-3
Appendix 3 be formatted and completed to a point similar to what would be submitted to the FAA if the FAA were to be issuing a mandatory action.
(4) Flammability Levels.
(a) The guidance in this paragraph applies to the new FRM or IMM requirements of § 25.981(b) and (c), and appendix M, to existing fuel tanks that exceed 7 percent average flammability exposure. For any fuel tank that is normally emptied and exceeds 7 percent average flammability exposure, if any portion of the tank is located in the fuselage contour, the rule requires TC holders to develop IMM or FRM that reduces the flammability exposure to 3 percent average flammability exposure and 3 percent warm day requirements of appendix M. The warm day requirement would limit the average flammability exposure of the tank for each of the ground, takeoff and climb phases of the airplane operation during warm days to 3 percent average flammability exposure. The flammability exposure limit for these particular tanks has been established in consideration of the service experience that shows these tanks to have a higher risk for fuel tank explosion than other tanks. For all other fuel tanks located in other portions of the airplane (for example, the wing and empennage), the proposal would require TC holders to develop IMM or FRM that reduces the flammability exposure below 7 percent and apply the requirements for an FRM of subparagraph M25.2, M25.3, M25.4 of appendix M if an FRM is selected as the means of compliance. This rule is not expected to result in the need for FRM or IMM in any fuel tanks located in the wings of airplanes in the existing fleet because previous assessments estimate these tanks have flammability exposure below 7 percent. However, the analysis required by this rule may reveal some fuel tanks located within the wing that exceed 7 percent.
(b) The definition of tanks that are normally emptied and auxiliary fuel tanks used in this section are the same as that discussed in the preamble to the flammability reduction rulemaking associated with this AC.
c. Compliance Times.
(1) Section 26.33(d) requires submitting for approval by the FAA oversight office the design changes and service instructions required by § 26.33(c) by September 20, 2010.
(2) The compliance times stated in this section are also used as the basis for the compliance dates for introduction of these systems into the operators’ fleets under parts 121, 125, and 129. Extension of the compliance dates for development of the service instructions by the certificate holders would either reduce the amount of time available to operators or delay full deployment of these safety improvements. Incorporation of FRM or IMM will likely require access inside the fuel tanks. Typically fuel tanks are only accessed during heavy maintenance checks that are done on a schedule established during development of the maintenance program. The compliance dates for the operational rules were established to allow a majority of the modifications to be done during these heavy maintenance checks. Introduction of FRM or IMM outside of normally scheduled A3-4
Appendix 3 maintenance would increase the cost to the operators because extra tank entry and airplane down time would be needed.
d. Critical Design Configuration Control Limitations.
(1) Section 26.33(e) requires that for fuel tanks equipped with FRM or IMM, holders of TCs affected by this section must establish airworthiness limitations consisting of CDCCL, inspections, or other procedures. The purpose of these limitations is, for tanks equipped with FRM, to prevent increasing the flammability exposure of the tanks above that permitted under § 26.33 and, for tanks equipped with IMM, to prevent degradation of the performance of the IMM installed in accordance with this section.
Appendix 2 of this AC provides additional guidance regarding development of CDCCL.
For example, certain fuel tanks may rely on natural cooling or use of certain fuel types to meet the flammability levels required by the rule. Therefore, CDCCL may be required that define the critical features, such as—
• flammability exposure of the unheated aluminum wing tank,
• cooling rate,
• limits on heat input,
• limits on use of high volatility fuels such as JP-4,
• quantity of engine bleed air flow that is used for inerting,
• limits on penetrations of the fuel tank,
• limits on any changes to fuel management that may affect FRM,
• limits on changes to any placards or means used to visibly identify critical design features of the fuel tank system that must not be compromised for the operational life of the airplane.
(2) Instructions for Continued Airworthiness. As discussed below, airworthiness limitations, such as those in this section, are part of the ICA. Section 21.50 requires that TC holders make changes to the ICA available to persons required to comply with them.
As used throughout this notice, the term “make available” is used in the same sense that it is used in § 21.50.
e. Airworthiness Limitations.
(1) Section 26.33(f) requires creation of an ALS, unless previously established.
The ALS is required by current part 25 and includes those items that have mandatory inspection or replacement times related to fuel systems and structure. The ALS is included in the ICA, approved as part of certification, and distributed with an airplane on delivery. In this way the ALS is visible to all who need it and who would be required to comply with it under §§ 121.1117, 125.509 and 129.117 of this rule. The current part 25 ALS and ICA requirements apply only to airplane types originally certified after Amendment 25-54 (adopted in 1981) and were developed for structural considerations.
As a result, they are not applicable to many current airplanes and do not currently contain information for other systems.
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Appendix 3
(2) For those TC holders of airplanes that currently do not have an ALS, the regulation only requires establishing an ALS to include fuel tank safety related limits.
This would not require that the ALS for these airplanes include the other requirements for an ALS established under Amendment 25-54 to part 25, or a later amendment. For those TC holders or applicants with airplanes certified to Amendment 25-54 or later, the existing ALS would be revised to include the fuel tank system ALI.
f. Compliance Planning.
(1) Historically, the FAA has worked together with the TC holders when safety issues arise to identify solutions and actions that need to be taken. Some of the safety issues that have been addressed by this process include those involving aging aircraft structure, thrust reversers, cargo doors, and wing icing protection. In some cases service instructions have not been developed in a timely manner. While some manufacturers have addressed these safety issues and developed service instructions, others have not applied the resources necessary to develop service instructions in a timely manner. This has caused delay in the adoption of corrective action(s). The compliance planning requirements of § 26.33(g) and (h) are intended to provide TC holders and the FAA with assurance that they understand what means of compliance is acceptable and have taken necessary actions, including assigning sufficient resources, to achieve compliance with this section. This paragraph is based substantially on “The FAA and Industry Guide to Product Certification,” which describes a process for developing project-specific certification plans for type certification programs. This Guide may be found in the docket. This planning requirement would not apply to future applicants for TC because, as described in the Guide, this type of planning routinely occurs at the beginning of the certification process. (Additional information is available in the Order referenced in paragraph 4e(14).)
(2) The Guide recognizes the importance of ongoing communication and cooperation between applicants and the FAA. Section 26.33, while regulatory in nature, is intended to encourage establishment of the same type of relationship in the process of complying with this section.
(a) Compliance Plan for Flammability Exposure Analysis. Section
26.33(g) requires submittal of a compliance plan within 90 days after September 19, 2008, for the flammability exposure analysis required by this section. The intent of the proposal is to promote early planning and communication between the certificate holders and the FAA. The affected design approval holders would be required to submit a compliance plan that addresses the following:
1 A proposed schedule, identifying all major milestones, for meeting the flammability analysis compliance date of this rule or a determination that compliance with § 26.33(b) of this section is not required because design changes and service instructions for FRM or IMM will be developed and made available as required by § 26.33.
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Appendix 3 2 If required, a proposed means of performing a flammability exposure analysis.
(b) Compliance Plan for Design Changes and Service Instructions.
1 Section 26.33(h) requires that each holder of a TC required to comply with § 26.33(c) must submit to the FAA oversight office a compliance plan for their project within 210 days after September 19, 2008. In addition to items corresponding to those required for the compliance plan in § 26.33(g), this plan requires--
(aa) A proposal for submitting a draft of all compliance items required by § 26.33(d), (e) and (f) for review by the FAA oversight office not less than 60 days before the compliance times specified in the rules, and
(bb) A proposed means of compliance with this section, identifying all required deliverables, including all compliance items and all data to be developed to substantiate compliance. If the TC holder has already initiated compliance, the FAA oversight office will review the results of those efforts to ensure that the results are acceptable.
(cc) A proposal for how the approved service information and any necessary modification parts will be made available to affected persons.
2 This section is intended to ensure that affected persons and the FAA have a common understanding and agreement of what is necessary to achieve compliance with this section. Integral to the compliance plan will be the inclusion of procedures to allow the FAA to monitor progress toward compliance. These aspects of the plan will help ensure that the expected outcomes will be acceptable and on time. The schedule for the availability of the service information and any required parts is critical to the affected operators ability to schedule the modification of their airplanes and make changes to their maintenance or inspection programs in accordance with the operational rules. We would expect each TC holder to work with the FAA oversight office to develop a plan to create the required service instructions within the specified time. The plan should include periodic reviews with the FAA office.
3 The success of this fuel tank safety initiative hinges upon the timely development of service instructions and production incorporation of FRM or IMM by the affected certificate holders. If service instructions are not available when required, operators will not be able to begin incorporation of the FRM or IMM into their fleet as their airplanes undergo normally scheduled maintenance checks. Delay in availability of the service instructions could result in the need for operators to do unscheduled maintenance to comply with the operational requirements, resulting in significant unnecessary cost.
g. Section 26.33(j) requires that affected type certificate holders implement the compliance plans, as approved under that section. It allows for revisions to the plans, if A3-7
Appendix 3 approved, but such revisions would still have to result in compliance by the specified compliance dates.
2. Section 26.35 Changes to type certificates affecting fuel tank flammability : This section addresses changes to TCs, including installing auxiliary fuel tanks, changes in the capacity of fuel tanks, and changes that may increase the fuel tank flammability exposure of an existing fuel tank that is required by § 26.33(c) to incorporate either a FRM or IMM. An auxiliary fuel tank installed by STC or field approval may result in adverse effects on any FRM or IMM developed by the TC holder as required by § 26.33. This section requires those affected to conduct a flammability exposure analysis of their design, an impact assessment to determine any adverse impact their design may have on tanks for which CDCCL are required, and development of design changes to address adverse changes in flammability exposure. The dates for demonstrating compliance are shown as follow:
TC holders – Service instructions (including CDCCL) submittal date 9/20/10 14 months 4 months 2 months 14 months 60 days Rule effective 9/19/08 Compliance plan for flam.
analysis 12/18/08 Flam.
analysis completed 9/20/09 Impact assessment plan 11/19/10 Impact assessment 3/21/11 FIMM plan 5/19/11 90 days 9 months FIMM draft items 7/21/12 Final FIMM items 9/19/12
FIGURE 3-2 Compliance Timeline for Holders and Applicants of Changes to Certificates (§ 26.35)
a. Applicability. Paragraph 26.35 (a) states that this section applies to holders and applicants for approvals of the following design changes to any airplane subject to § 26.33(a):
• For holders of STCs or field approvals issued before September 19, 2008, and for applicants for STCs or amendments to TCs applied for before September 19, 2008, if the approval was not issued before A3-8
Appendix 3 September 19, 2008, this section applies to installation of a Normally Emptied fuel tank.
• For applicants for STCs or amendments to TCs applied for on or after September 19, 2008, this section applies to installation of a Normally Emptied fuel tank, changes to fuel tank capacity, and changes that may increase the flammability exposure of an existing fuel tank for which FRM or IMM is required by § 26.33 (c).
(1) Existing STCs and Field Approvals. For existing STCs and field approvals, this proposal excludes design changes other than for Normally Emptied fuel tank installations. (Field approvals are no longer issued for fuel tank installations.) The meaning of “Normally Emptied” fuel tank is explained earlier in the discussion of §
25.981 and in paragraph 5 of this AC. As discussed in the background section of the preamble to the flammability rulemaking associated with this AC, SFAR 88 included review of all changes to the airplane that could result in the development of ignition sources. We reviewed the fuel system related STCs in the fleet and did not identify any changes that would significantly increase fuel tank flammability. Therefore we have determined that application of this rule to current STC holders, other than those relating to auxiliary fuel tank installations, would not improve fuel tank safety.
(2) Pending Applications for STCs and TC Amendments to TCs. Except for applications that are pending as of September 19, 2008, for installation of Normally Emptied fuel tanks, pending applications for design change approvals were excluded from the final rule. Under § 26.35(d)(2), applicants with pending applications for design changes to install Normally Emptied fuel tanks must comply with § 25.981 at Amendment
25-125.
(3) Future Applicants for STCs or TC amendments.
(a) Auxiliary Fuel Tanks Installed Under STC or amendment to TC.
The regulation applies to design changes for which application is made on or after September 19, 2008, to install auxiliary fuel tanks on large transport category airplanes subject to the part 26 rule. The applicability list is included in appendix 1 to this AC.
These design changes must be shown to comply with § 25.981, as discussed previously in this AC. For example, the center wing box structure on some versions of certain airplane models did not originally carry fuel, but later models of the airplane may include fuel in these areas. This would be considered to be a change to add a new fuel tank, and compliance with § 25.981 would be required.
(b) Design Changes Affecting Fuel Tank Capacity. An applicant may propose to change the size of sections to an existing fuel wing tank or change the useable fuel capacity in an existing tank. Both increases and decreases in fuel tank capacity must be addressed. Under § 26.35(d)(3), these applicants must comply with the requirements of § 26.33. For example, the applicant must perform a flammability exposure analysis for the modified tank and, if the exposure exceeds 7 percent, the applicant must include FRM or IMM, as required by § 26.33.
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Appendix 3
(c) Design Changes that May Increase Fuel Tank Flammability Exposure of Tanks for which FRM or IMM are Required. Examples of design changes that may increase fuel tank flammability exposure include installation of hydraulic or electronics system heat exchangers in a fuel tank, installation of heater blankets on the wing, modification of the fuel management that results in changes in fuel tank flammability, installation of a fuel re-circulation system that transfers heat from the engine to the fuel tank, or changes to the flight manual to use lower flash point fuels such as JP-4 or Russian or Chinese fuels. As discussed below, applicants for these types of design changes must perform an impact assessment and, if applicable CDCCL are compromised, develop flammability impact mitigation means.
b. Compliance Times. Section 26.35(b) establishes a timeframe in which the affected persons must submit for approval (to the FAA oversight office) a flammability exposure analysis for their design changes. The rule includes a 12-month timeframe to complete the analysis for existing STCs. Any applicant whose STC or TC amendment is not approved within 12 months after September 19, 2008, would have to complete the analysis before approval.
c. Flammability Analysis.
(1) Supplemental type certificate holders or applicants affected by this section would need to conduct a flammability analysis using the method defined in appendix N of the rule. A number of inputs are required to conduct this analysis. Airplane specific data, such as flight length distributions or airplane climb rate, may not be readily available from the original TC holder. We intend the STC holders to obtain the information by working with the operators of airplanes that have their STC installed.
Applicants would need to work with prospective customers. Operators have business agreements with the original TC holders and access to information they obtained when they purchased the airplane. Conservative assumptions or business agreements with the original TC holders are other possible methods of gathering airplane type specific data needed for the analysis.
(2) The flammability analysis required by this § 26.35(b) is intended to identify applications for fuel tank installations that would require incorporation of FRM or IMM or that may increase the flammability exposure of such tanks. As discussed in the preamble to this rule, for existing fuel tank STCs, the flammability analysis is needed to determine if future action should be taken to address auxiliary fuel tanks installed under STCs or field approvals. Additional analysis after obtaining the CDCCL from the TC holder and developing any FIMM, is necessary to demonstrate that the final configuration complies with the applicable flammability analysis requirements and does not violate the CDCCL defined by the original TC holder.
(3) For design changes that may increase the flammability of fuel tanks equipped with FRM or IMM for which compliance with applicable CDCCL must be shown, the purpose of the requirement to perform flammability analyses is to ensure that A3-10
Appendix 3 the change does not increase flammability exposure in ways that were not anticipated when the CDCCL were developed. If an applicant can show that the design would have no such effect, it may be possible to avoid performance of a full analysis per appendix N through substantiating an equivalent level of safety finding.
d. Impact Assessment.
(1) Section 26.35 requires affected persons1 to submit for approval (to the FAA oversight office) an impact assessment of the fuel tank system, as modified by their design change. The purpose of this requirement is to identify any features of the modification to the original type design that may violate the critical design configuration control limitations developed by the original TC holder under § 26.33(d). For example, if an FRM that utilizes inerting were incorporated into an airplane, a CDCCL would likely be developed that would limit venting of air into the fuel tank because it could introduce oxygen into the tank, resulting in a flammable vapor space. In this case the STC holder would need to assess its design and identify any violation of the CDCCL identified for the FRM. Results from the analysis would be provided to the FAA in the form of a report or summary letter.
(2) Holders of STCs and field approvals for fuel tanks designed to be normally emptied on airplane models listed in Table 3-1 have to submit the safety assessment by March 21, 2011. This date is six months after the TC holder is required to establish their CDCCLs. Applicants for STCs and for amendments to type certificates whose design changes are not approved within that six-month period would have to submit the assessment before approval of the change. Once the CDCCLs are approved, the TC holder is required to make them available to other affected persons, including those subject to this section.
1 This refers to STC holders for auxiliary fuel tanks as of September 19, 2008, and future applicants for design changes that may increase flammability exposure of tanks for which FRM or IMM are required.
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Appendix 3
TABLE 3-1
AFFECTED AIRPLANE MODELS
Model – Boeing 747 Series 737 Series 777 Series 767 Series 757 Series Model – Airbus A318, A319, A320, A321 Series A300, A310 Series A330, A340 Series
e. Development of Service Instructions. Section 26.35(d) requires development of design changes and service instructions as stated in § 26.35 (d)(1), (d)(2) and (d)(3).
(1) Section 26.35(d)(1) affects persons required to prepare impact assessments, described in the previous paragraph. It includes requirements that apply if the impact assessment shows that a design change compromises any CDCCL applicable to any airplane on which the change is eligible for installation. The holder or applicant would have to develop a means, referred to as a Flammability Impact Mitigation Means (FIMM), to comply with all applicable CDCCLs. FIMM could include either additional design changes or limitations or other procedures. If FIMM are necessary, the applicant or holder would also have to show that their design change, as modified by the FIMM, would still meet the other requirements of this section. For example, § 26.35(d) requires that the flammability analysis for an existing auxiliary fuel tank, as modified by FIMM, would have to be accomplished per § 26.35(b). This paragraph is necessary to ensure that the safety improvements in this rule are not degraded by later design changes.
(2) Section 26.35(d)(2) requires applicants for STCs and amended TCs for installation of a Normally Emptied tank, to meet the requirements of § 25.981 in effect on September 19, 2008 if—
(a) the application is made before September 19, 2008 and the approval was not issued before September 19, 2008, or
(b) the application was made on or after September 19, 2008,
(3) Section 26.35(d)(3) requires applicants for a STC or an amendment to a type certificate made on or after September 19, 2008, that changes the capacity of an A3-12
Appendix 3 existing tank to comply with the requirements of § 26.33, Holders of type certificates:
Fuel tank flammability, as discussed in paragraph 1 of this appendix.
(4) Various methods described in this AC are available for meeting the flammability exposure requirements. The exact modifications needed to comply depend upon specific details of the particular design and choices made by the designers. The most likely solutions include inerting, cooling of the tank, installation of polyurethane foam and pressurizing the tank similar to other tanks that use air pressure for fuel transfer.
f. Compliance Times for Design Changes and Service Instructions . Section
26.35(e) establishes timeframes in which holders of STCs and field approvals and applicants for STCs and amendments to TCs must comply with the requirements of §
26.35(d). Supplemental type certificate holders and holders of field approvals would be required to comply by September 19, 2012, which is 24 months after the TC holder compliance date for § 26.33(c). Applicants for STCs and amendments to TCs whose applications are pending on September 19, 2008, would have to comply before the FAA would issue their approval.
g. Compliance Planning. Section 26.35(f) requires compliance plans for the actions required by this section. Compliance planning is discussed earlier in this appendix with guidance for § 26.33. Because STC holders and applicants would need the TC holders’ CDCCLs to comply with paragraphs (c) and (d) of this section, the compliance times for submitting those plans provide adequate time after the TC holders are required to comply with § 26.33. The compliance planning dates are given in Table 2 of § 26.35(f), which is shown below.
h. Section 26.35(g) requires that affected holders and applicants implement the compliance plans, as approved under that section. It allows for revisions to the plans, if approved, but such revisions would still have to result in compliance by the specified compliance dates.
TABLE 3-2
COMPLIANCE PLANNING DATES
Flammability Exposure Analysis Plan Impact Assessment Plan Design Changes and Service Instructions Plan STC and Field Approval Holders December 18, 2008 November 19, 2010 May 19, 2011
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