2010-4167. Airworthiness Directives; The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 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 all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The existing AD 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 existing AD also currently requires repetitive gap checks of the inboard and outboard carriage of the outboard mid-flaps to detect fractured carriage spindles, and corrective actions if necessary. This proposed AD would require any new or serviceable carriage spindle installed per the requirements of the existing AD to meet minimum allowable diameter measurements taken at three locations. This proposed AD also would require new repetitive inspections, measurements, and overhaul of the carriage spindles, and applicable corrective actions. In addition, this proposed AD would require replacing any carriage spindle when it has reached its maximum life limit. This proposed AD results from reports of fractures that resulted from stress corrosion and pitting along the length of the spindle and spindle diameter, and additional reports of corrosion on the outboard flap carriage spindles. We are proposing this AD to detect and correct cracked, corroded, or fractured carriage spindles, and to prevent severe flap asymmetry, which could result in reduced control or loss of controllability of the airplane.

DATES:

We must receive comments on this proposed AD by April 15, 2010.

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 Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

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:

Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; 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-2010-0173; Directorate Identifier 2009-NM-076-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 November 24, 2003, we issued AD 2003-24-08, Amendment 39-13377 (68 FR 67027, December 1, 2003), for all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD 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. That AD also currently requires repetitive gap checks of the inboard and outboard carriage of the outboard mid-flaps to detect fractured carriage spindles, and corrective actions if necessary. That AD resulted from a report indicating that the inboard and outboard carriage spindles (number 7 and 8 carriage spindles) were fractured on the right outboard flap during approach to landing. We issued that AD to detect and correct cracked, corroded, or fractured carriage spindles, and to prevent severe flap asymmetry, which could result in reduced control or loss of controllability of the airplane.

Actions Since Existing AD Was Issued

The preamble to AD 2003-24-08 explains that we considered the requirements “interim action” and were considering further rulemaking. We now have determined that further rulemaking is indeed necessary, and this proposed AD follows from that determination.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. The service bulletin describes procedures for repetitive detailed and magnetic particle inspections to detect discrepancies (including corrosion, pitting, and cracks) of the carriage spindle, repetitive measurements to determine the diameter of certain areas of the carriage spindle, and applicable corrective actions. The corrective actions include repairing any corrosion or pitting, or replacement with a new or serviceable carriage. The service bulletin also describes procedures for repetitive overhauls of the carriage. In addition, the service bulletin describes procedures for repetitive replacements of any carriage when it has reached its maximum life limit.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to develop on other airplanes of the same type design. For this reason, we are proposing this AD, which would supersede AD 2003-24-08 and would retain certain requirements of the existing AD. This proposed AD would require any new or serviceable carriage spindle installed per the requirements of the existing AD to meet minimum allowable diameter measurements taken at three locations of the spindle. This proposed AD also would require accomplishing the actions specified in the service bulletin described previously.

Change to Existing AD

This proposed AD would retain certain requirements of AD 2003-24-08. Since AD 2003-24-08 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, the corresponding paragraph identifiers have changed in this proposed AD, as listed in the following table:

Revised Paragraph Identifiers

Requirement in AD 2003-24-08	Corresponding requirement in this proposed AD
paragraph (c)	paragraph (g)
paragraph (d)	paragraph (h)
paragraph (e)	paragraph (i)
paragraph (f)	paragraph (j)
paragraph (g)	paragraph (k)
paragraph (h)	paragraph (l)
paragraph (i)	paragraph (m)
paragraph (j)	paragraph (n)

Costs of Compliance

There are about 2,852 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Inspections (required by AD 2003-24-08)	12	$85	None	$1,020 per inspection cycle	652	$665,040 per inspection cycle.
Inspections and measurements (new proposed actions)	2	85	None	$170 per inspection and measurement cycle	652	$110,840 per inspection and measurement cycle.
Overhauls (new proposed actions)	16	85	$28,000 1	$29,360 per overhaul cycle	652	$19,142,720 per overhaul cycle.
Replacements (new proposed actions)	16	85	$60,000 2	$61,360 per replacement cycle	652	$40,006,720 per replacement cycle.
1 $7,000 per spindle; 4 spindles per airplane.
2 $15,000 per spindle; 4 spindles per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the actions required by this AD, and that no operator would accomplish those actions in the future if this AD were not adopted. However, we have been advised that the carriages are already being overhauled and replaced on some affected airplanes. In addition, the replacement cycle is approximately every 20 years. Therefore, the future economic cost impact of this proposed rule on U.S. operators is expected to be less than the cost impact figures indicated above.

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
• Incorporation by reference
• 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 39-13377 (68 FR 67027, December 1, 2003) and adding the following new airworthiness directive (AD):

The Boeing Company: Docket No. FAA-2010-0173; Directorate Identifier 2009-NM-076-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by April 15, 2010.

Affected ADs

(b) This AD supersedes AD 2003-24-08, Amendment 39-13377.

Applicability

(c) This AD applies to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category.

Subject

(d) Air Transport Association (ATA) of America Code 57: Wings.

Unsafe Condition

(e) This AD results from a report indicating that the inboard and outboard carriage spindles were fractured on the right outboard flap during approach to landing. We are issuing this AD to detect and correct cracked, corroded, or fractured carriage spindles and to prevent severe flap asymmetry, which could result in reduced control or loss of controllability of the airplane.

Compliance

(f) 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 Certain Requirements of AD 2003-24-08, With Updated Service Information

Compliance Times

(g) The tables in paragraph 1.E., “Compliance” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003, specify the compliance times for paragraphs (g) through (k) of this AD. For carriage spindles that have accumulated the number of flight cycles or years in service specified in the “Threshold” column of the tables, accomplish the gap check and nondestructive test (NDT) and general visual inspections specified in paragraphs (h) and (j) of this AD within the corresponding interval after December 4, 2003 (the effective date AD 2003-24-08), as specified in the “Interval” column. Repeat the gap check and NDT and general visual inspections at the same intervals, except:

(1) The gap check does not have to be done at the same time as an NDT inspection; after doing an NDT inspection, the interval for doing the next gap check can be measured from the NDT inspection; and

(2) As carriage spindles gain flight cycles or years in service and move from one category in the “Threshold” column to another, they are subject to the repetitive inspection intervals corresponding to the new threshold category.

Work Package 2: Gap Check

(h) Perform a gap check of the inboard and outboard carriage of the left and right outboard mid-flaps to determine if there is a positive indication of a severed carriage spindle, in accordance with Work Package 2 of paragraph 3.B., “Work Instructions” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003.

Work Package 2: Corrective Actions

(i) If there is a positive indication of a severed carriage spindle during the gap check required by paragraph (h) of this AD, before further flight, remove the carriage spindle and install a new or serviceable carriage spindle in accordance with the “Work Instructions” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003; or Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. If, as a result of the detailed inspection described in paragraph 4.b. of Work Package 2 of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003, a carriage spindle is found not to be severed and no corrosion and no cracking is present, it can be reinstalled on the mid-flap in accordance with Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003; or Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. After the effective date of this AD, use only Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009.

Work Package 1: Inspections

(j) Perform a NDT inspection and general visual inspection for each carriage spindle of the left and right outboard mid-flaps to detect cracks, corrosion, or severed carriage spindles, in accordance with the “Work Instructions” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003.

Work Package 1: Corrective Actions

(k) If any corroded, cracked, or severed carriage spindle is found during any inspection required by paragraph (j) of this AD, before further flight, remove the carriage spindle and install a new or serviceable carriage spindle in accordance with the “Work Instructions” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003; or Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. After the effective date of this AD, use only Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009.

Parts Installation

(l) Except as provided in paragraph (i) of this AD: As of December 4, 2003, no person may install on any airplane a carriage spindle that has been removed as required by paragraph (i) or (k) of this AD, unless it has been overhauled in accordance with the “Work Instructions” of Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003; or Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. After the effective date of this AD, use only Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. To be eligible for installation under this paragraph, the carriage spindle must have been overhauled in accordance with the requirements of paragraph (m) of this AD.

(m) During accomplishment of any overhaul specified in paragraph (l) of this AD, use the procedures specified in paragraphs (m)(1) and (m)(2) of this AD during application of the nickel plating to the carriage spindle in addition to those specified in Boeing 737 Standard Overhaul Practices Manual, Chapter 20-42-09, Revision 25, dated July 1, 2009.

(1) The maximum deposition rate of the nickel plating in any one plating/baking cycle must not exceed 0.002-inches-per-hour.

(2) Begin the hydrogen embrittlement relief bake within 10 hours after application of the plating, or less than 24 hours after the current was first applied to the part, whichever is first.

Exception to Reporting Recommendations in Certain Service Bulletins

(n) Although Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003, recommends that operators report inspection findings to the manufacturer, this AD does not contain such a reporting requirement.

New Actions Required by This AD

Inspections, Measurements, and Overhauls of the Carriage Spindle

(o) At the applicable times specified in paragraph (o)(1) or (o)(2) of this AD: Do the detailed inspection for corrosion, pitting, and cracking of the carriage spindle, the magnetic particle inspection for cracking of the carriage spindle, measurements of the spindle to determine if it meets the allowable minimum diameter, and overhauls, and applicable corrective actions by accomplishing all the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009. The applicable corrective actions must be done before further flight. Repeat these actions thereafter at intervals not to exceed 12,000 flight cycles on the carriage spindle or 8 years, whichever comes first.

(1) For Model 737-100, -200, -200C airplanes, at the later of the times specified in paragraph (o)(1)(i) or (o)(1)(ii) of this AD:

(i) Before the accumulation of 12,000 total flight cycles on the carriage spindle since new or overhauled, or within 8 years after the installation of the new or overhauled part, whichever comes first.

(ii) Within 1 year after the effective date of this AD.

(2) For Model -300, -400, and -500 series airplanes, at the later of the times specified in paragraph (o)(2)(i) or (o)(2)(ii) of this AD:

(i) Before the accumulation of 12,000 total flight cycles on the carriage spindle since new or overhauled, or within 8 years after the installation of the new or overhauled part, whichever comes first.

(ii) Within 2 years after the effective date of this AD.

Replacement of the Carriage Spindle

(p) For Model 737-100, -200, -200C airplanes: Replace the carriage spindle with a new or documented (for which the service life, in flight cycles, is known) carriage spindle, in accordance with Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009, at the later of the times specified in paragraphs (p)(1) and (p)(2) of this AD, except as required by paragraph (r) of this AD. Overhauling the carriage spindles does not zero-out the flight cycles. Total flight cycles accumulate since new.

(1) Before the accumulation of 48,000 total flight cycles on the new or overhauled carriage.

(2) Within three years or 7,500 flight cycles after the effective date of this AD, whichever occurs first.

(q) For Model 737-300, -400, and -500 series airplanes: Replace the carriage spindle with a new or documented (for which the service life, in flight cycles, is known) carriage spindle, in accordance with Boeing Alert Service Bulletin 737-57A1218, Revision 5, dated February 9, 2009, at the later of the times specified in paragraphs (q)(1) and (q)(2) of this AD, except as required by paragraph (r) of this AD. Overhauling the carriage spindles does not zero-out the flight cycles. Total flight cycles accumulate since new.

(1) Before the accumulation of 48,000 total flight cycles on the new or overhauled carriage.

(2) Within six years or 15,000 flight cycles after the effective date of this AD, whichever occurs first.

(r) For airplanes with an undocumented carriage: Do the applicable actions specified in paragraph (p) or (q) of this AD at the applicable time specified in paragraph (r)(1) or (r)(2) of this AD.

(1) For Model 737-100, -200, -200C series airplanes: Do the actions specified in paragraph (p) of this AD at the time specified in paragraph (p)(2) of this AD.

(2) For Model -300, -400, and -500 series airplanes: Do the actions specified in paragraph (q) of this AD at the time specified in paragraph (q)(2) of this AD.

Repetitive Replacements of Carriage Spindle

(s) For all airplanes: Repeat the replacement of the carriage spindle specified by paragraph (p) or (q) of this AD, as applicable, thereafter at intervals not to exceed 48,000 total flight cycles on the new or overhauled carriage spindle.

Alternative Methods of Compliance (AMOCs)

(t)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Or, e-mail information to [e-mail].

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

Issued in Renton, Washington, on February 17, 2010.

Stephen P. Boyd,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.