Source: https://www.federalregister.gov/documents/2007/08/24/E7-16668/airworthiness-directives-boeing-model-737-300--400-and--500-series-airplanes
Timestamp: 2018-02-22 13:39:38
Document Index: 224286054

Matched Legal Cases: ['art 4', 'art 25', 'art 25', 'art 91', 'art 91', 'art 121', 'art 125', 'art 135', 'arts 121']

A Proposed Rule by the Federal Aviation Administration on 08/24/2007
72 FR 48597
48597-48600 (4 pages)
Docket No. FAA-2007-29043
Directorate Identifier 2007-NM-177-AD
E7-16668
https://www.federalregister.gov/d/E7-16668 https://www.federalregister.gov/d/E7-16668
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 737-300, -400, and -500 series airplanes. This proposed AD would require revising the FAA-approved maintenance inspection program to include inspections that will give no less than the required damage tolerance rating for each structural significant item (SSI), doing repetitive inspections to detect cracks of all SSIs, and repairing cracked structure. This proposed AD results from a report of incidents involving fatigue cracking and corrosion in transport category airplanes that are approaching or have exceeded their design service objective. We are proposing this AD to maintain the continued structural integrity of the entire fleet of Model 737-300, -400, and -500 series airplanes.
We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2007-29043; Directorate Identifier 2007-NM-177-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.
As a follow-on from that determination, we issued AC No. 91-56, “Supplemental Structural Inspection Program for Large Transport Category Airplanes,” dated May 6, 1981. That AC provides guidance material to manufacturers and operators for use in developing a continuing structural integrity program to ensure safe operation of older airplanes throughout their operational lives. This guidance material applies to transport airplanes that were certified under the fail-safe requirements of part 4b (“Airplane Airworthiness, Transport Categories”) of the Civil Air Regulations or damage tolerance structural requirements of part 25 (“Airworthiness Standards: Transport Category Airplanes”) of the Federal Aviation Regulations (FAR) (14 CFR part 25), and that have a maximum gross weight greater than 75,000 pounds. The procedures set forth in that AC are applicable to transport category Start Printed Page 48598airplanes operated under subpart D (“Special Flight Operations”) of part 91 of the FAR (14 CFR part 91); part 121 (“Operating Requirements: Domestic, Flag, and Supplemental Operations”); part 125 (“Certification and Operations: Airplanes having a Seating Capacity of 20 or More Passengers or a Maximum Payload of 6,000 Pounds or More”); and part 135 (“Operating Requirements: Commuter and On-Demand Operations”) of the FAR (14 CFR parts 121, 125, and 135). The objective of the SSIP was to establish inspection programs to ensure timely detection of fatigue cracking.
In order to evaluate the effect of increased fatigue cracking with respect to maintaining fail-safe design and damage tolerance of the structure of Boeing Model 737-300, -400, and -500 series airplanes, Boeing conducted a structural reassessment of those airplanes, using damage tolerance evaluation techniques. Boeing accomplished this reassessment using the criteria contained in AC No. 91-56, as well as Amendment 25-45 of section 25.571 (“Damage-tolerance and fatigue evaluation of structure”) of the FAR (14 CFR 25.571). During the reassessment, members of the airline industry participated with Boeing in working group sessions and developed the SSIP for Model 737-300, -400, and -500 series airplanes. Engineers and maintenance specialists from the FAA also supported these sessions. Subsequently, based on the working group's recommendations, Boeing developed the Supplemental Structural Inspection Document (SSID).
We have reviewed Boeing Models 737-300/400/500 Airplanes Document No. D6-82669, “Supplemental Structural Inspection Document,” Original Release, dated May 2007 (hereafter “the SSID”). The SSID describes procedures for revising the FAA-approved maintenance inspection program to include inspections that will give no less than the required damage tolerance rating (DTR) for each supplemental significant item (SSI), doing repetitive inspections to detect cracks of all SSIs, and repairing cracked structure. Accomplishing the actions specified in the SSID is intended to adequately address the unsafe condition.
We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require the following actions:
Paragraph (g) of the proposed AD would require incorporation of a revision into the FAA-approved maintenance inspection program that provides no less than the required DTR for each SSI listed in the SSID.
Paragraph (i) of the proposed AD would require repairing any cracked structure in accordance with a method approved by the FAA or an Authorized Representative (AR) for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the FAA to make those findings.
Paragraph (j) of the proposed AD specifies the requirements of the inspection program for transferred airplanes. Before any airplane that is subject to this proposed AD can be added to an air carrier's operations specifications, a program for doing the inspections required by this proposed AD must be established.
Section 3.0, “Structural Significant Items (SSIs)” of the SSID specifies a threshold of 66,000 flight cycles for accomplishing the initial inspections; however, it does not specify a grace period for airplanes that are near or have passed that threshold. This proposed AD would allow a grace period of 12 months after the effective date of the AD to incorporate the SSID into the FAA-approved maintenance inspection program. This proposed AD also would allow a grace period of 4,000 flight cycles measured from 12 months after the effective date of the AD to initiate the applicable inspections to detect cracks of all SSIs.
The SSID does not specify instructions on how to repair certain conditions. This proposed AD would require repairing those conditions in one of the following ways:
There are about 1,961 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.
Revision of maintenance inspection program 1,200 per operator (26 U.S. operators) $80 $96,000 per operator 599 $2,496,000.
Inspections 600 per airplane 80 $48,000, per airplane, per inspection cycle 599 $28,752,000 per inspection cycle.
Further, compliance with this proposed AD would be a means of compliance with the aging airplane safety final rule (AASFR) for the baseline structure of Model 737-300, -400, and -500 series airplanes. The AASFR final rule requires certain operators to incorporate damage tolerance inspections into their maintenance inspection programs. These requirements are described in 14 Start Printed Page 48599CFR 121.370(a) and 129.16. Accomplishment of the actions required by this proposed AD will meet the requirements of these CFR sections for the baseline structure. The costs for accomplishing the inspection portion of this proposed AD were accounted for in the regulatory evaluation of the AASFR final rule.
Boeing: Docket No. FAA-2007-29043; Directorate Identifier 2007-NM-177-AD.
(a) The FAA must receive comments on this AD action by October 9, 2007.
(d) This AD results from a report of incidents involving fatigue cracking and corrosion in transport category airplanes that are approaching or have exceeded their design service objective. We are issuing this AD to maintain the continued structural integrity of the entire fleet of Model 737-300, -400, and -500 series airplanes.
(f) The term “the SSID,” as used in this AD, means Boeing Models 737-300/400/500 Airplanes Document No. D6-82669, “Supplemental Structural Inspection Document,” Original Release, dated May 2007.
(g) Before the accumulation of 66,000 total flight cycles, or within 12 months after the effective date of this AD, whichever occurs later, incorporate a revision into the FAA-approved maintenance inspection program that provides no less than the required damage tolerance rating (DTR) for each structural significant item (SSI) listed in the SSID. (The required DTR value for each SSI is listed in the SSID.) The revision to the maintenance inspection program must include and must be implemented in accordance with the procedures in Section 5.0, “Damage Tolerance Rating (DTR) System Application,” and Section 6.0, “SSI Discrepancy Reporting” of the SSID. Under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection requirements contained in this AD and has assigned OMB Control Number 2120-0056.
(h) Before the accumulation of 66,000 total flight cycles, or within 4,000 flight cycles measured from 12 months after the effective date of this AD, whichever occurs later, do the applicable initial inspections to detect cracks of all SSIs, in accordance with the SSID. Repeat the applicable inspections thereafter at the intervals specified in Section 3.0, “Implementation” of the SSID.
(i) If any cracked structure is found during any inspection required by paragraph (h) of this AD, before further flight, repair the cracked structure using a method approved in accordance with the procedures specified in paragraph (k) of this AD.
(j) Before any airplane that is subject to this AD and that has exceeded the applicable compliance times specified in paragraph (h) of this AD can be added to an air carrier's operations specifications, a program for the accomplishment of the inspections required by this AD must be established in accordance with paragraph (j)(1) or (j)(2) of this AD, as applicable.
(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 Start Printed Page 48600(PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.
Issued in Renton, Washington, on August 12, 2007.
[FR Doc. E7-16668 Filed 8-23-07; 8:45 am]