E8-6054. Airworthiness Directives; Bombardier Model DHC-8-400 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Bombardier Model DHC-8-400 series airplanes. The existing AD currently requires inspecting all barrel nuts to determine if the barrel nuts have a certain marking, inspecting affected bolts to determine if the bolts are pre-loaded correctly, and replacing all hardware if the pre-load is incorrect. For airplanes on which the pre-load is correct, the existing AD requires doing repetitive visual inspections for cracking of the barrel nuts and cradles and replacing all hardware for all cracked barrel nuts. The existing AD also requires replacement of all hardware for certain affected barrel nuts that do not have cracking, which would end the repetitive inspections for those airplanes. The existing AD also provides an optional replacement for all affected barrel nuts. This proposed AD would require replacement of all affected barrel nuts. This proposed AD results from reports of cracking in the barrel nuts at the four primary front spar wing-to-fuselage attachment joints. We are proposing this AD to detect and correct cracking of the barrel nuts at the wing front spar wing-to-fuselage joints, which could result in reduced structural integrity of the wing-to-fuselage attachments and consequent detachment of the wing.

DATES:

We must receive comments on this proposed AD by April 24, 2008.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this AD, contact Bombardier, Inc., Bombardier Regional Aircraft Division, 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Pong Lee, Aerospace Engineer, Airframe and Propulsion Branch, ANE-171, FAA, New York Aircraft Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, New York 11590; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2008-0356; Directorate Identifier 2008-NM-042-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

On February 7, 2008, we issued AD 2008-04-02, amendment 39-15374 (73 FR 8187, February 13, 2008), for certain Bombardier Model DHC-8-400 series airplanes. That AD requires inspecting all barrel nuts to determine if the barrel nuts have a certain marking, inspecting affected bolts to determine if the bolts are pre-loaded correctly, and replacing all hardware if the pre-load is incorrect. For airplanes on which the pre-load is correct, that AD requires doing repetitive visual inspections for cracking of the barrel nuts and cradles and replacing all hardware for all cracked barrel nuts. That AD also requires replacement of all hardware for certain affected barrel nuts that do not have cracking, which would end the repetitive inspections for those airplanes. That AD also provides an optional replacement for all affected barrel nuts. That AD resulted from reports of cracking in the barrel nuts at the four primary front spar wing-to-fuselage attachment joints. We issued that AD to detect and correct cracking of the barrel nuts at the wing front spar wing-to-fuselage joints, which could result in reduced structural integrity of the wing-to-fuselage attachments and consequent detachment of the wing.

Actions Since Existing AD Was Issued

The preamble to AD 2008-04-02 explains that we consider the requirements “interim action” and were considering further rulemaking to require the replacement of all hardware for all barrel nuts identified with a marking of LH7940T SPS 01. We now have determined that further rulemaking is indeed necessary, and this proposed AD follows from that determination.

FAA's Determination and Requirements of the Proposed AD

These airplanes are manufactured in Canada and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, Transport Canada Civil Aviation (TCCA) has kept the FAA informed of the situation described above. We have examined the TCCA's findings, evaluated all pertinent information, and determined that AD action is necessary for airplanes of this type design that are certificated for operation in the United States.

This proposed AD would supersede AD 2008-04-02 and would retain the requirements of the existing AD. This proposed AD would also require replacement of all affected barrel nuts.

Costs of Compliance

This proposed AD would affect about 48 airplanes of U.S. registry.

The actions that are required by AD 2008-04-02 and retained in this proposed AD take about 3 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the currently required actions is $11,520, or $240 per airplane, per inspection cycle.

Replacement of the hardware of a barrel nut, if required, will take about 12 work hours per airplane, at an average labor rate of $80 per work hour. Required parts will cost about $800 per airplane. Based on these figures, we estimate the cost of a replacement to be $1,760 per barrel nut.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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.

For the reasons discussed above, I certify that the proposed regulation:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-15374 (73 FR 8187, February 13, 2008) and adding the following new airworthiness directive (AD):

Bombardier, Inc. (Formerly de Havilland, Inc.): Docket No. FAA-2008-0356; Directorate Identifier 2008-NM-042-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by April 24, 2008.

Affected ADs

(b) This AD supersedes AD 2008-04-02.

Applicability

(c) This AD applies to Bombardier Model DHC-8-400, DHC-8-401, and DHC-8-402 airplanes, certificated in any category; serial numbers 4001 and 4003 through 4176 inclusive.

Unsafe Condition

(d) This AD results from reports of cracking in the barrel nuts at the four primary front spar wing-to-fuselage attachment joints. We are issuing this AD to detect and correct cracking of the barrel nuts at the wing front spar wing-to-fuselage joints, which could result in reduced structural integrity of the wing-to-fuselage attachments and consequent detachment of the wing.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Restatement of Requirements of AD 2008-04-02

Inspections and Corrective Actions

(f) Within 50 flight hours after February 13, 2008 (the effective date of AD 2008-04-02), inspect all barrel nuts, part number DSC228-16, to determine if the barrel nuts are identified with a marking of LH7940T SPS 01. Inspect in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(1) If no barrel nuts are identified with a marking of LH7940T SPS 01, no further actions are required by this paragraph.

(2) If any barrel nut is found that is identified with a marking of LH7940T SPS 01, before further flight, inspect the inboard and outboard bolts to determine if the bolts are pre-loaded correctly. Inspect in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(i) If the pre-load is incorrect (i.e., the ring can be rotated), before further flight, replace all hardware at that location in accordance with the Accomplishment Instructions of the alert service bulletin.

(ii) If the pre-load is correct, before further flight, do a visual inspection for cracking of the barrel nuts and cradles in accordance with the Accomplishment Instructions of the alert service bulletin.

(A) If no cracking of the barrel nut and cradle is found, do the applicable action required by paragraph (g) of this AD.

(B) If no cracking of the barrel nut is found and only cracking of the cradle is found, no action is required by this paragraph provided that the applicable corrective action specified in paragraph (g) of this AD is done.

(C) If any cracking of the barrel nut is found, before next flight, replace all hardware only at that location in accordance with the Accomplishment Instructions of the alert service bulletin.

(g) For any barrel nuts on which no cracking of the barrel nut was found during the inspection required by paragraph (f)(2)(ii) of this AD, do the applicable corrective action specified in paragraph (g)(1), (g)(2), (g)(3), (g)(4), or (g)(5) of this AD at the compliance time specified in the applicable paragraph.

(1) If four barrel nuts having no cracking are found, do the actions specified in paragraphs (g)(1)(i), (g)(1)(ii), and (g)(1)(iii) of this AD.

(i) Within 50 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 50 flight hours until the replacement specified in paragraph (g)(1)(ii) of this AD is done.

(ii) Within 100 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, replace all hardware at the left-hand outboard location and the right-hand outboard location in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008. Replacing the barrel nuts on the outboard locations terminates the requirement to do the repetitive inspections specified in paragraph (g)(1)(i) of this AD.

(iii) Within 100 flight hours after doing the replacement required by paragraph (g)(1)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD for the remaining barrel nuts identified with a marking of LH7940T SPS 01. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement of all hardware at those locations is done. Do the inspection and replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(2) If three barrel nuts having no cracking are found, do the actions specified in paragraphs (g)(2)(i), (g)(2)(ii), and (g)(2)(iii) of this AD.

(i) Within 50 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 50 flight hours until the replacement specified in paragraph (g)(2)(ii) of this AD is done.

(ii) Within 100 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, replace all hardware for one affected barrel nut at the outboard location, on the side with two affected barrel nuts, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008. Replacing the barrel nut on the outboard location terminates the requirement to do the repetitive inspections specified in paragraph (g)(2)(i) of this AD.

(iii) Within 100 flight hours after doing the replacement required by paragraph (g)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD for the remaining barrel nuts identified with a marking of LH7940T SPS 01. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement of all hardware at those locations is done. Do the inspection and replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(3) If two barrel nuts having no cracking are found and both nuts are on the same side, do the actions specified in paragraphs (g)(3)(i), (g)(3)(ii), and (g)(3)(iii) of this AD.

(i) Within 100 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement specified in paragraph (g)(3)(ii) of this AD is done.

(ii) Within 500 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, replace all hardware for one affected barrel nut at the outboard location that has two affected barrel nuts in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008. Replacing the barrel nut on the outboard location terminates the requirement to do the repetitive inspections specified in paragraph (g)(3)(i) of this AD.

(iii) Within 100 flight hours after doing the replacement required by paragraph (g)(3)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD for the remaining barrel nut identified with a marking of LH7940T SPS 01. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement of all hardware at that location is done. Do the inspection and replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(4) If two barrel nuts having no cracking are found and are on opposite sides, within 100 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement of all hardware at those locations is done. Do the inspection and replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

(5) If one barrel nut having no cracking is found, within 100 flight hours after doing the inspection required by paragraph (f)(2)(ii) of this AD, repeat the inspection specified in paragraph (f)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours until the replacement of all hardware at that location is done. Do the inspection and replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008.

Actions Accomplished According to Previous Issue of Alert Service Bulletin

(h) Actions accomplished before February 13, 2008, in accordance with Bombardier Alert Service Bulletin A84-57-19, dated February 1, 2008, are acceptable for compliance with the corresponding actions specified in this AD.

Actions Accomplished According to Bombardier Alert Service Bulletin A84-57-18

(i) For airplanes on which the actions specified in Bombardier Alert Service Bulletin A84-57-18, dated January 16, 2008, were accomplished before February 13, 2008 and on which no barrel nuts were found that were identified with a marking of LH7940T SPS 01: No further action is required by this AD.

Parts Installation

(j) As of February 13, 2008, no person may install a barrel nut, part number DSC228-16, identified with a marking of LH7940T SPS 01, on any airplane.

New Requirement of This AD

Replacement of All Affected Barrel Nuts

(k) For airplanes on which barrel nuts are inspected in accordance with paragraph (g)(1)(iii), (g)(2)(iii), (g)(3)(iii), (g)(4), or (g)(5) of this AD: Within 3,000 flight hours after the effective date of this AD, replace all hardware for all remaining barrel nuts, part number DSC228-16, identified with a marking of LH7940T SPS 01. Do the replacement in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-57-19, Revision A, dated February 6, 2008. Replacement of all hardware for all affected barrel nuts constitutes terminating action for this AD.

Special Flight Permit

(l) Special flight permits, as described in Section 21.197 and Section 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199), may be issued to operate the airplane to a location where the requirements of this AD can be accomplished but concurrence by the Manager, New York Aircraft Certification Office, FAA, is required prior to issuance of the special flight permit. Before using any approved special flight permits, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO. Special flight permits may be permitted provided that the conditions specified in paragraph (l)(1), (l)(2), (l)(3), (l)(4), and (l)(5) of this AD are met.

(1) Both the right-hand side and left-hand side of the airplane must have at least one barrel nut that is not within the suspect batch (i.e., barrel nut is not identified with a marking of LH7940T SPS 01). The barrel nuts that are not within the suspect batch must be in good working condition (i.e., no cracking of the barrel nut).

(2) No passengers and no cargo are onboard.

(3) Airplane must operate in fair weather conditions with a low risk of turbulence.

(4) Airplane must operate with reduced airspeed. For further information, contact Bombardier, Q Series 24 Hour Service Customer Response Center, at: Tel: [phone]; Fax: [phone]; E-mail: [e-mail].

(5) All of the conditions specified in paragraphs (l)(1), (1)(2), (l)(3), and (l)(4) of this AD are on a case by case basis. Contact your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO, for assistance.

Alternative Methods of Compliance (AMOCs)

(m)(1) The Manager, New York Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

Related Information

(n) Canadian emergency airworthiness directive CF-2008-11, dated February 5, 2008.

Issued in Renton, Washington, on March 17, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.