Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, that would have superseded an existing AD that currently requires repetitive inspections to find cracks, fractures, or corrosion of each carriage spindle of the left and right outboard mid-flaps; and corrective action, if necessary. The proposed AD would also have mandated the previously optional overhaul or replacement of the carriage spindles, which would have ended the repetitive inspections required by the existing AD. This new action revises the proposed rule by adding a new requirement to the nickel plating procedures and extending the compliance time for the overhaul or replacement. The actions specified by this new proposed AD are intended to prevent severe flap asymmetry due to fractures of the carriage spindles on an outboard mid-flap, which could result in reduced control or loss of controllability of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by December 1, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-219-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-219-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Robert Hardwick, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6457; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-219-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-219-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on March 4, 2003 (68 FR 10188). That NPRM (the “original NPRM”) proposed to supersede AD 2002-22-05, amendment 39-12929 (67 FR 66316, October 31, 2002), which is applicable to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That proposal would have continued to require repetitive inspections to find cracks, fractures, or corrosion of each carriage spindle of the left and right outboard mid-flaps; and corrective action, if necessary. That NPRM also proposed to mandate the previously optional overhaul or replacement of the carriage spindles, which would end the repetitive inspections required by the existing AD. Fractures of the carriage spindles on an outboard mid-flap could result in severe flap asymmetry and consequent reduced control or loss of controllability of the airplane.

Actions Since Issuance of Previous Proposal

Due consideration has been given to the comments received in response to the original NPRM. Some of the comments have resulted in changes to the original NPRM.

Request To Change Maximum Thickness of Nickel Plating

One commenter, the manufacturer, asks that the maximum thickness of the nickel plating, as specified in paragraph (d)(2) of the original NPRM, be changed. The commenter provides substantiating data which show that, since the rate of plating is directly related to the rate of hydrogen generation in the plating process, limiting the deposition rate more efficiently minimizes hydrogen generation during plating and reduces the potential for hydrogen embrittlement of the part. The commenter asks that paragraph (d)(2) be changed to read, “After initial application of the plating current and during the plating process, the rate of plating deposit must be maintained between .001-inch-per-hour and a maximum of .002-inch-per-hour.”

The FAA partially agrees with the commenter. The material and configuration of the outboard flap carriage are such that there is increased concern for hydrogen embrittlement in the large diameter of the spindle region. After reviewing the service experience and finding no other existing related requirements, the FAA finds it necessary to include the plating requirements in this AD. Controlling the deposition rate is a direct method of controlling the quality of the plate and generation of hydrogen during the plating process. The absorption and diffusion of hydrogen into the metal during the plating process leads to a condition known as “hydrogen embrittlement.” Metals affected by hydrogen embrittlement have reduced ductility and may prematurely fail during normal usage due to this condition. The original requirement of 0.020-inch-per-plating/baking cycle did not control the deposition rate, and there were wide variations. High deposition rates produce high rates of hydrogen and poor-quality grain structure. The key parameter of 0.002-inch-per-hour maximum deposition rate (which is a more stringent requirement) provides a safeguard against high deposition rates. There is no significant detrimental effect from low deposition rates, so the minimum requirement requested will not be included. Therefore, we have changed paragraph (d)(2) of this supplemental NPRM to read, “The maximum thickness of the nickel plating that is deposited in any one plating/baking cycle must not exceed 0.002-inch-per-hour.”

Request To Remove Nickel Plating Requirement

One commenter asks that the nickel plating requirement specified in paragraph (d)(2) of the original NPRM be removed. The commenter states that if it performs the nickel plating per the new requirement, it must perform a minimum of three plating/baking cycles, which would extend the time necessary for overhaul of the carriage spindle by 15 days. The commenter suggests two alternative methods to use in place of the current proposed requirement, and provides documentation showing those methods.

We do not concur that the nickel plating requirement should be removed. However, as explained under “Request to Change Maximum Thickness of Nickel Plating,” we have changed paragraph (d)(2) of this supplemental NPRM to read, “The maximum deposition rate of the nickel plating that is deposited in any one plating/baking cycle must not exceed 0.002-inch-per-hour.” No other change to the supplemental NPRM is necessary in this regard.

Requests To Extend Compliance Time

Several commenters request that the compliance time for the overhaul or replacement specified in paragraphs (c), (c)(1), and (c)(2) of the original NPRM be extended as follows:

• One commenter states that the proposed compliance time of 1 year after the effective date of the AD to replace the carriage spindles on Model 737-200C series airplanes is restrictive. The commenter asks that it be changed, due to inspection results, from “1 year after the effective date of this AD” to 24 to 36 months after the effective date, to allow time for procurement/overhaul of the spindles and to schedule the airplane during a heavy maintenance check. The commenter also states that the proposed compliance time of 2 years after the effective date of the AD to replace the spindles on Model 737-400 series airplanes is also restrictive. The commenter asks that the compliance time be changed, due to inspection results, to 36 to 48 months after the effective date, to allow time for procurement/overhaul of spindles and to schedule the airplane during a heavy maintenance check.
• One commenter asks that carriage spindles that were overhauled per Boeing 737 Component Maintenance Manual 57-53-36 before the effective date of AD 2002-22-05, and have not had all finishes and plating removed, be allowed to remain in service on the airplane for 8 years or 12,000 flight cycles, whichever comes later. The commenter adds that it has found no fractured carriage spindles to date. The commenter also asks that we allow 30 months instead of 24 months to overhaul or replace with new, any in-service carriage spindles that have not been overhauled per the referenced service bulletin. The commenter states that this would allow scheduling of the replacement of the carriage spindle during the current maintenance program without undue burden to its in-service operations.
• One commenter states that it currently has 52 Model 737-200 and 26 Model 737-300 series airplanes that would be affected by the original NPRM and has insufficient data for identifying the date each carriage spindle was overhauled or replaced during heavy maintenance visits. The commenter adds that, due to this fact, it would be forced to overhaul/replace the carriage spindles at the earliest time allowed, which is within 1 year for Model 737-200 series airplanes and 2 years for Model 737-300 series airplanes. The commenter notes that the manufacturer is unable to supply new carriage spindles to operators at a rate that would allow the replacement to be done within the time allotted. For Model 737-300 series airplanes, the manufacturer is producing about two carriage spindles per month, and overhaul of the part using an outside vendor takes approximately 3-4 weeks per airplane. With this turnaround time, the commenter would be unable to overhaul the parts in the timeframe required by the original NPRM. The commenter makes no specific request. We infer that the commenter is requesting that the compliance time be extended.
• One commenter asks that the compliance time for the initial overhaul specified in paragraph (c) of the original NPRM be extended to 2.5 years. The commenter states that, in order to install overhauled carriages on an aircraft, the flaps must be removed and reinstalled. The commenter adds that it performs a one-quarter D-check every 2.5 years, and this structural visit is the opportune time to perform such extensive maintenance.
• One commenter asks that the initial compliance times for the overhaul on Model 737-100/200 series airplanes and 737-300/400/500 series airplanes be extended to at least 3 years and 4 years, respectively, for the following reasons:

First, the compliance time for the initial inspection does not appear to account for the nondestructive test (NDT) inspection referenced in both the service bulletin and the existing AD. The commenter adds that the inspection in the referenced service bulletin is effective as an interim action in maintaining airplane safety, which indicates there are no urgent reasons to adhere to the short compliance time specified in the service bulletin for the spindle overhaul/replacement.

Second, the carriage spindle overhaul requirement means, in the commenter's case, that the spindle will have to be shipped off-site, which would require additional spares support. The short initial compliance timeframe creates a surge in demand for spares during the first 1 to 2 years. After that time, all additional spares acquired by the operators would sit on the shelf because that demand would go away for the remainder of the 8-year period until the next overhaul.

Third, due to the short initial compliance time, operators will have to remove the flaps outside the regularly scheduled maintenance visits to gain access. According to the procedures in the Boeing 737-300/-400/-500 Maintenance Planning Document D6-38278, the commenter estimates that the initial compliance time should be between 6 and 8 years for Model 737-300, -400, and -500 series airplanes, and between 6 and 10 years for Model 737-100 and -200 series airplanes.

In conclusion, the commenter states that, with immediate safety concerns already addressed in paragraph (a) of the original NPRM, increasing the compliance time specified in paragraph (c) of the original NPRM would allow accomplishment of the actions at regular maintenance intervals and would avoid a sudden demand for spares.

• One commenter asks that the compliance time specified in paragraph (c)(2)(ii) of the original NPRM (for the spindle overhaul/replacement) be changed to read, “Not later than the next major maintenance (D-check), and, until that time, repeat the NDT inspection of the spindles per the existing AD.” The commenter states that airplanes that have accumulated more than 12,000 total flight cycles, and exceeded the 8-year limitation, will be subject to the proposed 2-year compliance time. The commenter adds that, since no seed units have been provided by Boeing, procurement of the spindle is expensive, and the turnaround time is expected to be 20 days, there is no reason to ground the airplane and send the spindle for overhaul without having any spares.
• One commenter states that it will take about a year to obtain parts after ordering them, and the overhaul cannot be completed until the parts are received. The commenter states that it will be impossible to overhaul/replace the flap carriage within the proposed 2-year compliance time.
• One commenter asks for a change in the compliance time specified in paragraph (c) of the original NPRM from 12,000 flight cycles or 8 years, whichever occurs first, to 20,000 flight cycles or 8 years in-service, whichever occurs first. The commenter states that the additional flight-cycle allowance would allow the work to be done at every other D-check where time and resources to overhaul/replace the spindles are available. The commenter requests that this change apply to both the original inspection and the overhaul/replacement requirements.
• One commenter asks that we evaluate the requirement to overhaul or replace the spindles every 12,000 flight cycles or 8 years, based on inspection results and parts replacement costs. The commenter adds that the repetitive inspection intervals required by paragraph (a) of the proposed AD should be extended from 180 days to 18 months, so the airplane can be scheduled for inspection during heavy maintenance check intervals.
• One commenter states that mandating the overhaul of the carriage spindles every 8 years or 12,000 flight cycles, whichever is sooner, will have a significant cost impact on its fleet. The commenter adds that, under the current maintenance program, the carriage spindles are overhauled every 8 years, which, at current flying rates, equates to about 18,000 flight cycles. Therefore, a 12,000-flight-cycle compliance time would require overhaul at every heavy maintenance check, thereby doubling the overhaul cost. The commenter proposes that the carriage spindles remain in service until the 8-year limit is reached, provided the 180-day repetitive inspections are reinstated once the airplane reaches 12,000 flight cycles. The commenter states that this would provide an equivalent level of safety and give operators a significant cost benefit.

We agree to extend the initial compliance time somewhat. In revising this compliance time, we considered the safety implications, parts availability, and typical maintenance schedules of affected operators. In addition, the repetitive NDT inspections required by the existing AD, and restated in paragraph (a) of this supplemental NPRM, will allow operators more time to schedule maintenance and ensure safety in the interim until accomplishment of the overhaul or replacement. We have extended the compliance time specified in paragraphs (c)(1)(i) and (c)(1)(ii) of this supplemental NPRM to the later of the following: “Before the accumulation of 20,000 total flight cycles on the carriage spindle, or within 8 years since overhaul of the spindle or installation of a new spindle, whichever is first,” or “Within 2 years after the effective date of this AD.” We have extended the compliance time specified in paragraphs (c)(2)(i) and (c)(2)(ii) of this supplemental NPRM to the later of the following: “Before the accumulation of 20,000 total flight cycles on the carriage spindle, or within 8 years since overhaul of the spindle or installation of a new spindle, whichever is first,” or “Within 4 years after the effective date of this AD.” We have also extended the compliance time in paragraph (c) of this supplemental NPRM for the repetitive overhaul or replacement to every 20,000 flight cycles or 8 years, whichever is first. Extending the compliance time will not adversely affect safety but will accommodate the time necessary for the operators to obtain replacement parts and schedule the work.

We do not agree to extend the repetitive inspection intervals required by paragraph (a) of the supplemental NPRM; those inspections end when the overhaul or replacement specified in paragraph (c) of this supplemental NPRM is done. In developing an appropriate compliance time for the repetitive inspections, we considered not only the degree of urgency associated with addressing the subject unsafe condition, but the manufacturer's recommendation as to an appropriate compliance time, and the practical aspect of accomplishing the repetitive inspections within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. No change to the supplemental NPRM is necessary in this regard.

Request To Change Compliance Time to Calendar Time

One commenter contends that corrosion associated with the identified unsafe condition is a function of time rather than flight cycles. We infer that the commenter requests that the original NPRM be revised to reflect a compliance time for the spindle overhaul/replacement in terms of calendar time rather than flight cycles. We do not agree to use a calendar date in the AD because the compliance time in this case is a function of fleet utilization, which is unrelated to calendar dates. No change to the supplemental NPRM is necessary in this regard.

Request for Credit for Previously Overhauled Carriage Spindles

One commenter asks that the carriage spindles overhauled before issuance of AD 2002-22-05 (no finish/plating required) remain in service for 8 years or 12,000 flight cycles, whichever comes first. The commenter has been proactive on this issue, and started carriage spindle overhauls prior to the effective date of the original NPRM. The commenter adds that no fractured carriage spindles have been found to date.

We do not agree with the commenter. Although we acknowledge the fact that the commenter has not had any carriage spindle failures and maintains a good track record for diligent completion of AD requirements, many operators have been working to overhaul their fleets before the release of the AD in order to minimize the impact on the fleet. In light of the fact that the finish/plating removal was not required before issuance of AD 2002-22-05, carriage spindles that were overhauled before issuance of that AD may not have had the finishes/platings removed, and would not be compliant with that AD. Therefore, no change to the supplemental NPRM is necessary in this regard.

Request To Accept Alternative Methods of Compliance (AMOCs) Approved for AD 2002-22-05

Two commenters ask that the original NPRM be revised to accept certain AMOCs previously approved for AD 2002-22-05. One commenter states that the original NPRM does not have a provision for such AMOCs, and asks that a paragraph be added for previously approved AMOCs for paragraphs (a) and (b) of the original NPRM. The commenter recognizes that it would not be able to use previously approved AMOCs after paragraph (c) of the supplemental NPRM is accomplished. Another commenter asks that we allow for optional tracking of the carriage part and serial number instead of the aircraft serial number to demonstrate compliance. The commenter states that it currently has an AMOC approved for AD 2002-22-05 that addresses this situation.

We agree with the commenters' requests to accept certain AMOCs approved previously for AD 2002-22-05. We have added a new paragraph (f)(2) to this supplemental NPRM to include AMOCs previously approved for AD 2002-22-05. Regarding optional tracking of the carriage part and serial number instead of the airplane serial number, the commenter may submit substantiating data that support a request for an AMOC for this proposed AD per paragraph (f)(1) of this proposed AD.

Request To Require Additional AD for Carriage Spindle Only

One commenter states that paragraph (d) of the original NPRM describes two constraints on the overhaul process. The commenter notes that paragraph (d)(1) of the original NPRM specifies the maximum time allowed before carrying out the hydrogen embrittlement procedure, and paragraph (d)(2) of the original NPRM defines the maximum thickness of nickel plating that can be done at any one plating/baking cycle. The commenter adds that the Boeing Standard Operating Procedures Manual for nickel plating includes the requirements specified in paragraph (d)(1), but the maximum plating requirements specified in paragraph (d)(2) are not included in the Boeing Component Maintenance Manual (CMM) 57-53-56, so compliance cannot be assumed by following the procedures in the CMM. The commenter is concerned that if these elements are required in an AD, there is a possibility that a flap carriage may be overhauled without reference to the AD, and subsequently, since there is no mechanism to prevent it, passed back to the operator without evidence of compliance with requirements. The commenter suggests that, if the relevant amendments are not placed in the CMM (against which the overhaul is to be performed before the effective date of the AD), a component AD against the flap carriage assemblies should be issued to ensure that the overhaul requirements are both complied with and certified as such before the assemblies are passed on to an operator. The commenter adds that the magnetic particle inspection addresses only the carriage, not the carriage spindle.

We do not agree with the commenter. Overhaul manuals are not FAA-approved documents. Updating these manuals is done by the original equipment manufacturer for the benefit of the operators. When an unsafe condition exists, we issue an AD to correct that condition, and, if additional safeguards are required as part of the mandated action, those safeguards are included in the text of the AD, unless mandated in other rulemaking actions. Ultimately, it is the responsibility of the operator to ensure compliance with any ADs that affect the operator's fleet. No change to the supplemental NPRM is necessary in this regard.

Request To Remove or Change Paragraph (a)

One commenter asks that the current inspections that would be required by paragraph (a) of the original NPRM be removed or changed as they are ineffective for finding cracks. The commenter states that it performed the inspections and, approximately 10 days later, a carriage spindle severed during flight. The commenter does not see any benefit in performing the current inspections.

We do not agree with the commenter. The inspections mandated by AD 2002-22-05 are designed to find a fully failed spindle before the second spindle fails due to load redistribution from the failed spindle. AD 2002-22-05 is required to safeguard against a dual-spindle failure. Further, the carriage spindle is manufactured from high strength steel, which is a material not generally conducive to damage tolerance methods. No change to the supplemental NPRM is necessary in this regard.

Request To Add the Repetitive Overhaul in Paragraph (c) to the Operator's Time Limit Index

One commenter asks that paragraph (c) of the original NPRM, which requires repetitive overhaul of the carriage spindles every 12,000 flight cycles or 8 years, whichever is first, be incorporated into an Operator's Time Limit Index (Hard Time Component Program). The commenter states that this can be done by adding the following statement to paragraph (c): “Operators may incorporate the overhaul requirement into the FAA-approved maintenance program if the Principal Maintenance Inspector (PMI) approves that action.” The commenter adds that this would allow the PMI to approve the action, when appropriate, without a concern that it violates the Code of Federal Regulations.

We do not agree with the commenter. To include the overhaul of this part in a particular overhaul program would be an operations-dependent procedure and cannot be done as a general option. The commenter provides no data to substantiate that its request would provide an acceptable level of safety. However, an affected operator may request approval of an AMOC, as provided by paragraph (f)(1) of this AD, if data are submitted to support that an alternative method would provide an acceptable level of safety. No change to the supplemental NPRM is necessary in this regard.

Request To Change Cost Impact Section

Two commenters ask the Cost Impact section of the original NPRM be changed, as follows:

• One commenter states that the estimated cost of the replacement of the carriage spindle ($45,000 per spindle, and $10,000 per spindle for the overhaul) does not include the out-of-service time and work hours necessary.
• One commenter states that the “short” initial compliance time would require operators to remove flaps outside their routine maintenance program, which would take an additional 192 work hours per airplane. The commenter estimates the additional labor cost at over $500,000. The commenter adds that the overhaul of the carriage spindle will require additional spare carriage spindles over the short initial compliance timeframe. Based on an overhaul turnaround time of 30 days, the commenter estimates it would need up to six shipments of spare carriage spindles at a cost of approximately $1.2 million. All these spares would then not be used for the remainder of the 8-year period until the next overhaul. In addition, the commenter notes that the cost for overhauling the carriage spindle is almost $100,000, based on the cost estimate per airplane provided in the original NPRM.

We do not agree with the commenters. The cost impact information describes only the costs of the specific actions required by this AD. The number of work hours necessary to accomplish the overhaul or replacement, as specified in the cost impact information, is consistent with the service bulletin. This number represents the time necessary to perform only the actions actually required by this AD. We recognize that, in accomplishing the requirements of any AD, operators may incur additional costs due to special circumstances when scheduling maintenance visits. However, because maintenance schedules vary significantly from operator to operator, the hours necessary for access and close-up time, including out-of-service time, are almost impossible to calculate. No change to the supplemental NPRM is necessary in this regard.

Conclusion

Since certain changes described previously expand the scope of the original NPRM, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Changes to 14 CFR Part 39/Effect on the Proposed AD

On July 10, 2002, the FAA issued a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's airworthiness directives system. This regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance (AMOCs). Because we have now included this material in part 39, only the office authorized to approve AMOCs is identified in each individual AD.

Change in Labor Rate

We have reviewed the figures we have used over the past several years to calculate AD costs to operators. To account for various inflationary costs in the airline industry, we find it necessary to increase the labor rate used in these calculations from $60 per work hour to $65 per work hour. The cost impact information, below, reflects this increase in the specified hourly labor rate.

Cost Impact

There are approximately 3,132 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,384 airplanes of U.S. registry would be affected by this proposed AD.

The inspections that are currently required by AD 2002-22-05 take approximately 10 work hours per airplane to accomplish, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be $899,600, or $650 per airplane.

It would take approximately 2 work hours per airplane to accomplish the new detailed inspection, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the inspection proposed by this AD on U.S. operators is estimated to be $179,920, or $130 per airplane, per inspection cycle.

Should an operator be required to accomplish the overhaul, it would take approximately 32 work hours per airplane to accomplish, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the overhaul proposed by this AD is estimated to be $2,080 per airplane.

Should an operator be required to accomplish the replacement, it would take approximately 32 work hours per airplane to accomplish, at an average labor rate of $65 per work hour. Required parts would cost approximately $45,000 per carriage spindle. Based on these figures, the cost impact of the replacement proposed by this AD is estimated to be $47,080 per spindle, per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed 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 proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.