AD 97-13-08

This amendment supersedes an existing airworthiness directive (AD), applicable to all de Havilland Model DHC-8-100 and -300 series airplanes, that currently requires an inspection to detect discrepancies and damage of the low fuel pressure switch adapter/snubber (located on each engine fuel heater), and replacement, if necessary. That AD also requires an inspection to detect gaps or openings in each nacelle and engine-mounted firewall area, and in certain weather seals in the nacelles; and correction of discrepancies. This amendment requires certain new modifications to the nacelles that will minimize the passage of flammable fluid through the zones of the nacelle of each engine. The actions specified by this AD are intended to prevent the spread of fire through these zones in the event of an explosion during flight, and consequent structural damage to the airplane.

Final rule

97-13-08 DE HAVILLAND, INC.: Amendment 39-10055. Docket 96-NM-73-AD. Supersedes AD 92-13-11, Amendment 39-8281.
Applicability: All Model DHC-8-100 and-300 series airplanes, certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (h) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent the spread of fire through the zones of each nacelle, in the event of an explosion during flight, and consequent structural damage to the airplane, accomplish the following:

NOTE 2: The requirements of paragraphs (a) and (b) of this AD are restatements of the same paragraphs that appeared in AD 92-13-11, amendment 39-8281. These paragraphs require no additional action by operators who have already completed the specified actions.

(a) For airplanes having serial numbers 3 through 248, inclusive, on which Modification No. 8/1208 has not yet been accomplished, accomplish the following:

(1) Within 30 days after September 8, 1992 (the effective date of AD 92-13- 11, amendment 39-8281), remove and inspect the low fuel pressure switch adapter/snubber located on each engine fuel heater for damage to threads, indication of over-torque, and for proper seating, in accordance with the accomplishment instructions of de Havilland Alert Service Bulletin A8-73-14, Revision B, dated April 24, 1992. If the adapter/snubber is damaged or if evidence of over-torque is present, prior to further flight, replace the adapter/snubber with a serviceable part, in accordance with that service bulletin.

(2) Thereafter, at any time in which the low fuel pressure switch adapter/snubber assembly is removed, accomplish the inspection of the assembly as described in paragraph (a)(1) of this AD.

(3) Installation of Modification 8/1208, in accordance with de Havilland Service Bulletin 8-28-15, Revision A, dated April 17, 1992, constitutes terminating action for the inspections required by paragraphs (a)(1) and (a)(2) of this AD.

(b) For all Model DHC-8-100 and -300 series airplanes: Within 30 days after September 8, 1992 (the effective date of AD 92-13-11, amendment 39-8281), accomplish the procedures specified in paragraphs (b)(1) and (b)(2) of this AD.

(1) Inspect the nacelle vertical firewall section, firewall extension, and engine mounted firewall (reference: Maintenance Manual section 71-30-00) for gaps and openings that could permit flammable fluid to pass through. Gaps and openings may be found at lap joints, between bolts, and at carry-through fittings and grommets. If gaps are found, prior to further flight, seal the gaps using PR812, Pro-Seal 700, or other approved firewall sealants (reference: Maintenance Manual section 20-21-20). Allow the sealant to cure for at least 4 hours prior to further flight.

(2) Inspect access panels 419AT and 429AT as specified in DHC-8 Maintenance Manual [section 40-10, pages 12 and 14 (reference: Illustrated Parts Catalog 54-30- 00, Figure 5, Items 410 and 420)] for the presence and condition of the weather seal in the gap between the panels and the adjacent structure. If the gap is not sealed, prior to further flight, seal the panels using PR1422, PR1435, or other sealant specified in the DHC-8 Maintenance Manual, section 20-21-16. A release agent, applied prior to sealing, also may be used as specified in DHC-8 Maintenance Manual, section 20-21-19. Allow the sealant or release agent to cure for at least 4 hours, prior to further flight.

(c) For airplanes having serial numbers 3 through 137, inclusive, on which Modification No. 8/1126 has not been installed: Within 1 year after the effective date of this AD, seal the firewall of the lower cowling of each engine by installing angle-gasket assemblies and applying sealant, in accordance with de Havilland Service Bulletin 8-54-12, dated January 27, 1989.

(d) For airplanes having serial numbers 003 through 331, inclusive, on which Modification No. 8/1885 has not been installed: Within 1 year after the effective date of this AD, accomplish the procedures specified in paragraphs (d)(1), (d)(2), and (d)(3) of this AD in accordance with de Havilland Service Bulletin S.B. 8-54-25, Revision `A,' dated July 29, 1994.

(1) Inspect the vertical firewall section, firewall extension, and engine- mounted firewall of the upper structure of each nacelle, including the lap joints between bolts and at carry-through fittings and grommets, to detect gaps and openings through which flammable fluid could pass, in accordance with the service bulletin. If any gap or opening is detected, prior to further flight, seal the gap or opening, in accordance with the service bulletin.

(2) Inspect the upper access panels of each nacelle to detect the presence and condition of sealant in any gap between each panel and its adjacent structure, in accordance with the service bulletin. If there is no sealant or the sealant is discrepant, prior to further flight, apply or replace sealant, as applicable, in accordance with the service bulletin.

(3) Apply exterior labels and protective coatings to each access panel of the left and right nacelle in accordance with the service bulletin.

(e) For airplanes having serial numbers 003 through 332, inclusive, on which Modification No. 8/1887 has not been installed: Within 1 year after the effective date of this AD, replace the Camloc receptacles in each nacelle with stainless steel receptacles, and apply additional sealant to the firewall of each nacelle, in accordance with de Havilland Service Bulletin S.B. 8-54-30, Revision `B,' dated February 5, 1993.

(f) For airplanes having serial numbers 003 through 357, inclusive, on which Modification No. 8/1966 has not been installed: Within 1 year after the effective date of this AD, inspect the forward and rearward faces of the firewall, firewall extension, and engine mounted firewall of the lower structure of each nacelle for any gap or opening at lap joints, between bolts, and at carry-through fittings and grommets through which flammable fluid could pass, in accordance with de Havilland Service Bulletin S.B. 8-54-31, dated March 8, 1994. If any gap or opening is detected, prior to further flight, apply sealant in accordance with the servicebulletin.

(g) For airplanes having serial numbers 003 through 369, inclusive, on which Modification No. 8/2001 has not been installed: Within 1 year after the effective date of this AD, replace the existing seals on the cowling doors of each nacelle with improved seals, in accordance with de Havilland Service Bulletin S.B. 8-71-19, Revision `B,' dated February 24, 1995.

(h) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, New York Aircraft Certification Office (ACO), FAA, Engine and Propeller Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

(i) Special flight permits may be issuedin accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(j) The actions shall be done in accordance with de Havilland Alert Service Bulletin A8-73-14, Revision B, dated April 24, 1992; de Havilland Service Bulletin 8-54-12, dated January 27, 1989; de Havilland Service Bulletin S.B. 8-54-25, Revision `A', dated July 29, 1994; de Havilland Service Bulletin S.B. 8-54-30, Revision `B', dated February 5, 1993; de Havilland Service Bulletin S.B. 8-54-31, dated March 8, 1994; and de Havilland Service Bulletin S.B. 8-71- 19, Revision `B', dated February 24, 1995. The incorporation by reference of de Havilland Alert Service Bulletin A8-73-14, Revision B, dated April 24, 1992, was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of September 8, 1992 (57 FR 37872, August 21, 1992).The incorporation by reference of the other publications listed in the regulations was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario, Canada M3K 1Y5. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(k) This amendment becomes effective on July 30, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 92-13-11, amendment 39-8281 (57 FR 37872, August 21, 1992), which is applicable to all de Havilland Model DHC-8-100 and -300 series airplanes, was published in the Federal Register on March 18, 1997 (62 FR 12768). That action proposed to continue to require the actions currently required by AD 92-13-11, and to add a requirement that the following actions be performed on each engine nacelle:

- installation of new angle-gasket assemblies on the firewalls of the lower cowlings, and application of sealant to gaps and openings in these areas;

- inspection of the upper access panels of each nacelle for the presence and condition of weather sealing, and application or reapplication of sealant, if necessary;

- inspection of the firewall areas for gaps and openings at lap joints, between bolts, and at carry-through fittings and grommets; and the application of sealant, if necessary;

- modification of the nacelle by replacing Camloc receptacles made of silicon bronze with receptacles of stainless steel;

- application of additional sealant to the firewall areas after the Camloc receptacles have been replaced; and

- replacement of the seals on the cowling doors with improved seals.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received.

Support for the Proposal
The commenter supports the proposed rule. In addition, the commenter urges the FAA to mandate a rapid timeline for the rework of the compartment seals, and suggests that the FAA consider whether the optional terminating action for the low fuel pressure switch adapter/snubber should be required. The commenter suggests that the FAA should consider a warning system for identifying that a failure of the system and a potential hazard exists in the event the terminating action remains optional.

The FAA finds that the proposed compliance times specified in this AD were determined to be appropriate in light of the safety implications addressed by this AD. However, the FAA will consider the commenter s suggestions and, if warranted, may consider additional rulemaking to address these suggestions. No changes have been made to this final rule in response to the commenter s requests.

Correction to the Proposal
The FAA has become aware of a typographical error that appeared in paragraph (f) of the proposal. The modification number specified in that paragraph appeared incorrectly as "Modification No. 8/1996." Paragraph (f) of this final rule has been revised to correctly specify that modification number as "Modification No. 8/1966."

Conclusion
The FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
There are approximately 100 de Havilland Model DHC-8-100 and -300 series airplanes of U.S. registry that will be affected by this AD.

Each inspection of the low fuel pressure switch adapter/snubber that is currently required by AD 92-13-11 takes approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this currently required inspection on U.S. operators is estimated to be $24,000, or $240 per airplane, per inspection.

The inspection for gaps or openings in each nacelle, engine-mounted firewall area, and certain nacelle weather seals that is currently required by AD 92-13-11 takes approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this currently required inspection on U.S. operators is estimated tobe $72,000, or $720 per airplane.

The installation of new angle-gasket assemblies that is required by this new AD will take approximately 2 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be provided by the manufacturer at no cost to operators. Based on these figures, the cost impact of this installation on U.S. operators is estimated to be $12,000, or $120 per airplane.

The inspection of the upper access panels and firewalls of both nacelles, and the application of labels, that is required by this new AD will take approximately 7 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $43 per airplane. Based on these figures, the cost impact of this inspection and application of labels on U.S. operators is estimated to be $46,300, or $463 per airplane.

The replacement of the Camloc receptacles with improved receptacles that is required by thisnew AD will take approximately 8 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $15 per airplane. Based on these figures, the cost impact of this replacement on U.S. operators is estimated to be $49,500, or $495 per airplane.

The inspection and application of additional sealant to the firewalls of the nacelles that is required by this new AD will take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. The cost of required parts is estimated to be minimal. Based on these figures, the cost impact of this inspection and application of sealant on U.S. operators is estimated to be $24,000, or $240 per airplane.

The replacement of the seals on the cowling doors that is required by this new AD will take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be provided at no cost to operators, or will cost $1,270, depending on the kit required. Based on these figures, the cost impact of this replacement on U.S. operators is estimated to be between $24,000 and $151,000, or between $240 and $1,510 per airplane, depending on the kit required.

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.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussedabove, 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 39-8281 (57 FR 37872, August 21, 1992), and by adding a new airworthiness directive (AD), amendment 39-10055, to read as follows: