A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 94-25-03, amendment 39-9087 (59 FR 62563, December 6, 1994), which is applicable to all Fokker Model F.28 Mark series airplanes, was published in the Federal Register on November 8, 1999 (64 FR 60745). The action proposed to continue to require a revision to the Airplane Flight Manual (AFM) that prohibits takeoff in certain icing conditions unless either a tactile inspection is performed or specific takeoff procedures are followed. The action also proposed to add a requirement, for certain airplanes, for modification of the wing leading edge ice protection system to include on-ground wing ice protection, and a new revision to the AFM.
Since the Issuance of the Notice of Proposed Rulemaking (NPRM)
Fokker Services has issued Proforma Service Bulletin F28/30-032, including Appendix 1, dated December 1, 1999, applicable to Fokker Model F.28 Mark 4000 seriesairplanes. That proforma service bulletin describes certain corrections regarding the instructions and schematics for the modification of the wiring of the on-ground wing leading edge heating described in Fokker Proforma Service Bulletin F28/30-31 (which was referenced in the NPRM as the appropriate source of service information). Since Proforma Service Bulletin F28/30-032 only provides correction for certain procedures of 1 the modification of the wiring, the FAA has revised paragraph (b) of the final rule to also reference Proforma Service Bulletin F28/30-032. That proforma service bulletin was approved by the The Civil Aviation Authority-The Netherlands (CAA-NL), which is the airworthiness authority for the Netherlands.
Clarification of Applicability
The applicability of the NPRM affects all Model F.28 Mark 0070, 0100, 1000, 2000, 3000, and 4000 series airplanes. However, paragraph (b) of the NPRM specifies that only airplanes identified in Appendix I, Revision 1, dated August 14, 1999, of Fokker Service Bulletin SBF100-30-018, and Appendix I, Revision 1, dated May 4, 1998, of Fokker SB F28/30-031; are subject to the requirements of paragraph (b) of the NPRM. The FAA notes that the effectivity of the proforma service bulletins assigns different operators the actual performance instructions based on a number designated in the Appendix. For example, one airline may be assigned the specific instructions for Appendix I. Therefore, we have revised the applicability of paragraph (b) of the final rule to clarify that Model F.28 Mark 0070 and 0100 series airplanes identified in Appendix I, Revision 1, dated August 14, 1999, of Fokker Proforma Service Bulletin SBF100-30-018; and Model F.28 Mark 1000, 2000, 3000, and 4000 series airplanes identified in Appendix I, Revision 1, dated May 4, 1998, of Fokker Proforma Service Bulletin F28/30-031, Revision 1, dated May 4, 1998; and in Fokker Proforma F28/30-032, including Appendix 1, dated December 1, 1999; are subjectto the requirements specified in paragraphs (b)(1) and (b)(2) of this AD, in accordance with the appropriate proforma service bulletin, as applicable.
Public Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
1. Conditional Concurrence
One commenter expresses conditional concurrence with the proposed language of the NPRM. The commenter's concerns regarding certain issues are included in the discussions of other comments below.
2. Requests To Provide an Optional Method of Compliance
Several commenters identified certain concerns with an on-ground wing leading edge heating system. One of these commenters states that the ground wing leading edge anti-ice heating system will not accomplish the intent of the NPRM (i.e., to prevent degradation of aerodynamic lift during takeoff when icing conditions exist). Other commenters point out problem areasthat could result, such as:
Only partial surfaces (i.e., the leading edges) of the wings are heated. The rest of the wing remains unprotected.
Deicing/anti-icing fluid flow-off may occur, and heating may change the effective holdover time of the fluid.
Adverse aerodynamic effects from refreezing of runback water (runback ice).
Risk of leading edge structural damage due to overheating caused by a ground wing leading edge heating system.
The commenters state that other means exist that are equal to or superior to the system proposed in the NPRM, and request that the FAA provide such methods of compliance as alternatives to requiring installation of a ground wing leading edge anti-ice heating system.
The FAA does not agree that the issues specified by the commenters are sufficient to justify not mandating a ground wing leading edge anti-ice heating system. Our specific responses to each of the concerns above are as follows:
We acknowledge that only the leading edges of the wing are heated. However, we do not agree that heating some of the wing surfaces (i.e., leading edges) will not accomplish the intent of the NPRM. The intent of the NPRM is to ensure that the critical surfaces of the airplane are free from frost, ice, and snow at takeoff. This is accomplished by compliance with the operating rules of 91.527 and 121.629 of the Federal Aviation Regulations (14 CFR 91.527 and 121.629), in combination with the operation of the wing leading edge heating system on the ground.
We do not agree that operating the wing leading edge heat while on the ground will result in flow-off of fluid. The deicing fluid is typically heated to 60-degrees Centigrade (C) at the spray nozzle and would not be affected by 25-degree-C temperatures of the wing leading edge while being heated on the ground. We acknowledge that there may be some thinning of undiluted anti-icing fluids at the wing leading edge. However, there will be an offsetting benefit of havingthe wing leading edge heat on, which should delay the failure of the anti-icing fluid by keeping the water component above freezing.
We do not agree that there is a reason to be concerned over runback ice. For instance, ice melting on the leading edge and water consequently running to another area of the wing and refreezing should not occur, since the on-ground wing leading edge heating system is not intended for deicing purposes. The system should be used in addition to approved deicing or anti-icing procedures. Likewise, turning on the wing leading edge heat to melt ice and not performing deicing procedures is unlikely to occur, since regulations are already in place that prohibit such actions. Therefore, for the purposes of this AD, runback ice and refreezing are not issues of concern.
We do not agree that there is increased risk of structural damage to the leading edge due to overheating caused by the required heating system. We consider that, since the on-ground leading edge heating system complies with the requirements of 25.1309 (14 CFR 25.1309), any failures of the heating system, such as overheating of the structure, have been accounted for and substantiated in accordance with the hazard classification of a particular failure.
Based on the FAA's responses above to the commenter's concerns, no change to the final rule is necessary. However, we have revised the final rule to add a specific method acceptable for compliance based on another commenter's request. See the next comment and response below.
3. Request To Approve an Acceptable Method of Compliance
Two commenters request that the FAA approve the AlliedSignal "Contaminants-Fluid Integrity Measuring System," as an acceptable method of compliance with the requirements of the NPRM. The commenters present the following points in support of their request:
C/FIMSTM is a FAA-approved system via the Supplemental Type Certification (STC) process.
C/FIMSTM offers documented evidence as to its capabilities as an ice detector and as a fluid monitoring system, both in laboratory and in-service environments.
More than 4 years of in-service evaluations have occurred on the Midway Airlines fleet of Fokker Model F.28 Mark 0100 series airplanes.
Recorded documented performance is available for all weather conditions, including snow, freezing rain, and weather conditions specified as cautionary in AD 94-25-03.
With the system validated against existing approved procedures including tactile checks and the use of holdover timetables, C/FIMSTM produced absolutely no false annunciations.
C/FIMSTM installed on Fokker Model F.28 Mark 0100 series airplanes provides effective monitoring of the same surfaces addressed by the service bulletins specified in the NPRM.
The commenters state that even Fokker Services has recommended that the FAA give serious consideration to certifying C/FIMSTM as an alternative solution, since the leading edge heating system is not universally favored by Model F.28 Mark 0100 series airplanes operators.
We acknowledge that STC ST291CH (applicable to Fokker Model F.28 Mark 0100 series airplanes) approves the installation of the C/FIMSTM as an advisory system that informs the flightcrew if specific anti-icing fluids have failed or if ice or snow has accumulated on one of the ice detectors. That STC also contains instructions to insert Allied Signal Aerospace Canada, Airplane Flight Manual Supplement, Document Number 6C-486, Revision 2, dated August 4, 1999, into the AFM. The AFM Supplement describes how the C/FIMSTM operates when the modification is installed. Certification as an advisory system means that the system cannot be used as the prime means of determining if the airplane must be initially deiced or anti-iced, or if the airplane must be deiced or anti-iced again because a fluid has failed.
However, we have determined that, in combination with a revision to the Limitations Section of the AFM to install the AFM Supplement described above, installation of STC ST291CH on Fokker Model F.28 Mark 0100 series airplanes is acceptable for compliance with the requirement to install an on-ground wing leading edge heating system. Although C/FIMSTM is approved as an advisory system, we find that it will provide additional assurance that the airplane will take off free of snow, ice, or frost on the critical surfaces. This finding is contingent upon using C/FIMSTM in combination with approved procedures for complying with Federal Aviation Regulations 14 CFR 91.527 and 14 CFR 121.629.
Therefore, the FAA has revised the final rule to add a new paragraph (d) of the final rule to specify that installation of a C/FIMSTM in accordance with STC ST291CH and certain AFM revisions required by paragraph (d) of the final rule are acceptable for compliance with the requirements of paragraph (b) of this AD, and constitute terminating actions for the requirements of this final rule.
In addition,we have added a new Note 5 to the final rule to remind operators that accomplishment of the actions specified in paragraph (d) of the final rule does not relieve the requirement that airplane surfaces are free of ice, frost, and snow accumulation as required by 91.527 and 121.629 of the Federal Aviation Regulations (14 CFR 91.527 and 121.629).
4. Request To Withdraw the Proposal
One commenter states that, even with the on-ground wing thermal anti-icing system, operators will have to continue to rely upon using deicing or anti-icing fluids and performing the visual and tactile inspections for icing as the primary procedure for on-ground wing ice protection. Therefore, the commenter argues that there is insufficient improvement provided by the proposed heating system to warrant mandating the on-ground wing ice protection system. The FAA infers that the commenter is requesting that the NPRM be withdrawn.
The FAA does not agree. We acknowledge that operators will still have to rely on fluids and procedures that are necessary for compliance with 91.527 (14 CFR 91.527) and 121.629 (14 CFR 121.629). However, the mandatory tactile inspection required by this AD will be terminated when the on-ground wing anti-ice system is installed. Because of the accident and incident history of these airplanes, we have determined that, although the operations rules (cited above) require that the critical surfaces of the airplane be free from frost, ice, and snow at takeoff, these airplanes require additional measures to ensure safety of flight. Operation of the wing anti-ice system while on the ground is a method to ensure that the critical surfaces of the airplane are free of snow, ice, and frost at takeoff. No change is necessary to the AD in this regard.
5. Request To Allow Credit for Accomplishment of New Service Information
One commenter states that it has accomplished the modification of the wing anti-ice system for operation on the ground, in accordancewith Fokker Service Bulletin SBF100-30-018, Appendix I, Revision 1, dated August 14, 1999, rather than the original issuance of the service information as specified in the NPRM. The commenter requests that Revision 1 be specified as an alternative method of compliance.
The FAA agrees that accomplishment of Fokker Service Bulletin SBF100-30-018, Appendix I, Revision 1, dated August 14, 1999, provides an acceptable means of compliance with paragraph (b) of this AD. We have revised paragraph (b) of this AD to include Revision 1 of that service bulletin appendix.
6. Request To Revise Certain Modification Procedures
One commenter states that it is concerned about a safety issue if Fokker Service Bulletin F28/30-031, Appendix I, Revision 1, dated May 4, 1998 (which was specified in the NPRM as an appropriate service information), is accomplished. The commenter explains that accomplishment of that service bulletin would result in the engine anti-ice system being shut off from the operating engine should there be an engine failure during takeoff when the engine anti-ice system has been selected to the "on" position. This same commenter states that, although the commenter has accomplished the modification in accordance with Fokker Service Bulletin F28/30-031, Appendix I, the identified problem was corrected in accordance with additional service information received from Fokker. The commenter requests that the NPRM be revised to reference the corrected modification instructions.
The FAA agrees with the commenter's request for the reasons given by the commenter. As discussed under the header entitled "Since the Issuance of the Proposed Rule," Fokker Services has issued a new Proforma Service Bulletin F28/30-032, dated December 1, 1999, that describes certain corrective procedures for modifying the wiring for the on-ground wing anti-ice system. Therefore, those corrected procedures have been required in the final rule to clarify the procedures for the modification.
7. Request To Clarify Operating Procedures If the Heating System Is Inoperative
One operator requests that the FAA confirm that current relief specified in the Minimum Equipment List (MEL) for the on-ground heated leading edge system (OGHLES) will remain in effect. Specifically, the operator requests that the FAA clarify that, when the airplane is operated with the OGHLES inoperative, the operating limitations required by AD 94-25-03 should again govern the airplane operation.
The FAA agrees that clarification is needed in this regard. First, as part of that clarification, paragraph (b)(2) of the NPRM, which requires incorporation of Fokker Manual Change Notifications (MCNOs) into the AFM, has been relettered as paragraph (c) of the final rule. Second, we point out that, incorporation of the MCNOs required by paragraph (c) of the final rule allow for alternative takeoff procedures or tactile inspections in the event the on-ground heating system is inoperative. Therefore, no change to the final rule is necessary in this regard.
8. Request To Specify the Modification as Terminating Action
One commenter notes that paragraph (b) of AD 94-25-03 specifies that modification of the thermal anti-ice system, so that it can be operated on the ground in accordance with a method approved by the FAA, constitutes terminating action for the requirements of that AD. However, the commenter also notes that the NPRM proposing to supersede AD 94-25-03 does not contain reference to the terminating action. The commenter suggests adding such reference to Note 3 of the NPRM.
The FAA agrees with the commenter, and has revised this AD to add a statement in paragraph (c) of this AD specifying that accomplishment of the actions required by paragraph (b) and (c) of the AD constitutes terminating action for the requirements of paragraph (a) of the AD.
9. Request To Revise the Cost Estimate
One commenter states that its experience in accomplishing the heating system modification reveals that it takes approximately 400 work hours per airplane to accomplish, as opposed to the estimate of 274 work hours provided in the NPRM.
The FAA acknowledges that the actual work hours necessary to accomplish the required modification exceeds the estimated work hours provided by the NPRM. That estimate of work hours was provided to the FAA by the manufacturer based on the best data available to date. As explained in the NPRM, that estimate is intended to represent the time necessary to perform only the modification required by this AD. We recognize that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. However, the cost analysis in AD rulemaking actions typically does not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate. However, after considering the information presented by the commenter, we agree that the number of work hours required is higher than previously estimated. Therefore, the cost impact information provided in this final rule has been revised to estimate 400 work hours for accomplishment of the required modification.
10. Request To Revise the Unsafe Condition
One commenter states that it takes exception to the statement of the unsafe condition as presented in the NPRM. The commenter states that, contrary to the statement in the NPRM, no ice protection system (IPS) can "* * * prevent degradation of aerodynamic lift * * *" The commenter further states that, at best, the proposed modification represents only slight improvements over the present system and procedures. The FAA infers that the commenter is requesting that the statement of the unsafe condition be revised.
The FAA acknowledges that the statement of the unsafecondition should be revised. We agree that deicing and anti-icing fluid will minimally affect the aerodynamic lift and have revised the wording for the unsafe condition to more accurately reflect the description of the unsafe condition. For those sections in the final rule that discuss the unsafe condition, we have eliminated reference to aerodynamic lift and specified that the unsafe condition is to prevent takeoff with snow, ice, or frost on the critical surfaces of the airplane.
11. Request To Revise Icing Related Language
One commenter requests that any icing related language must be accompanied by a specific warning to the flightcrew that no ice protection system can keep an airplane as clean as it was on the day it was certified, and that keeping it clean is the ultimate objective of deicing or anti-icing.
The FAA does not agree that additional warning to the flightcrew is necessary. Although we acknowledge that no ice protection system can keep an airplane absolutely "clean" (i.e., free of ice, snow, and frost), the flightcrew is required by existing operational rules to keep the airplane's critical surfaces free from ice, snow, and frost at takeoff even though a wing leading edge heating system is being operated on the ground. No change to the final rule is necessary in this regard.
12. Request To Emphasize Flightcrew Actions and Procedures
One commenter states that, until technological improvements such as airplane design changes are able to "remove the source of the problem" (e.g., performance degradations due to airframe ice accretions and in-flight encounters with icing conditions), emphasis must be placed on the flightcrew actions, and procedures must be identified to preclude icing encounters that may cause degraded airplane performance.
The FAA does not agree. The intent of this final rule is to prevent airplane takeoff with snow, ice, or frost on critical surfaces, and not to address in-flight icing encounters. Certain other regulations and procedures exist that address in-flight icing encounters. Therefore, no change to this final rule is necessary in this regard.
Conclusion
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
Cost Impact
There are approximately 191 Fokker Model F.28 series airplanes of U.S. registry that will be affected by this AD.
The currently required AFM revisions required by this AD take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required AFM revisions of this AD on U.S. operators is estimated to be $60 per airplane.
The modification that is required by this new AD action for certain airplanes will take approximately 400 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $26,585 per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $50,585 per airplane.
The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.
Regulatory Impact
The regulations adopted hereinwill not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39-AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-9087 (59 FR 62563, December 6, 1994), and by adding a new airworthiness directive (AD), amendment 39-12827, to read as follows: