### 77615 Federal Register / Vol. 78, No. 247 / Tuesday, December 24, 2013 / Proposed Rules

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),

(3) Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction, and

(4) 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. 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 FAA amends § 39.13 by removing airworthiness directive (AD) 2007–19–09R1, Amendment 39–16322 (75 FR 30687, June 2, 2010), and adding the following new AD:

Turbomeca S.A.: Docket No. FAA–2007– 27009; Directorate Identifier 2007–NE– 02–AD.
(a) Comments Due Date

The FAA must receive comments on this AD action by February 24, 2014.
(b) Affected ADs

This AD supersedes AD 2007–19–09R1, Amendment 39–16322 (75 FR 30687, June 2, 2010).
(c) Applicability

This AD applies to Turbomeca S.A. Arriel 2B1 turboshaft engines that do not have modification TU157 incorporated.
(d) Unsafe Condition

This AD was prompted by reports of ruptures on hydromechanical metering unit (HMU) constant delta pressure valves that have less than 2,000 hours in service. We are issuing this AD to prevent failure of the HMU, which could lead to damage to the engine and damage to the aircraft.
(e) Compliance

Within the compliance times specified, replace the HMU with a part eligible for installation, unless already done.

(1) HMU Operating Hours and Power Turbine (C2) Cycles Are Known.

(i) If on the effective date of this AD, the HMU C2 cycles are less than 900, then replace the HMU before the HMU accumulates 1,000 C2 cycles or 1,500 HMU operating hours, whichever occurs first;

(ii) If on the effective date of this AD, the HMU C2 cycles are 900 or more, then replace the HMU within 100 HMU C2 cycles after the effective date of this AD;

(iii) Thereafter, replace the HMU at every 1,000 HMU C2 cycles or 1,500 HMU operating hours, whichever comes first.

(2) HMU Operating Hours Are Known and C2 Cycles Are Not Known.

(i) If on the effective date of this AD, the HMU operating hours are less than 1,100, then replace the HMU before accumulating 1,200 HMU operating hours;

(ii) If on the effective date of this AD, the HMU operating hours are 1,100 or more, then replace the HMU within 100 HMU operating hours after the effective date of this AD;

(iii) Thereafter, replace HMUs at every 1,200 HMU operating hours.
(f) Definition

For the purposes of this AD, ‘‘HMU operating hours’’ or ‘‘C2 cycles’’ are defined as operating hours or C2 cycles since new, since overhaul, or since application of Turbomeca S.A. Service Bulletin (SB) No. 292 73 2105, Version B, dated December 16, 2010, or earlier version, or of Turbomeca S.A. Mandatory SB (MSB) No. 292 73 2818, Version D, dated June 24, 2013, or earlier version, whichever occurs later.
(g) Optional Terminating Action

Incorporation of Turbomeca S.A. SB No. 292 73 2157, Version C, dated July 17, 2013, or earlier version, is terminating action to the replacement and repetitive inspection requirements of this AD.

(h) Credit for Previous Actions

If you performed the actions required by paragraphs (e)(1) or (e)(2) of this AD using an earlier version of Turbomeca S.A. MSB No. 292 73 2818, Version D, dated June 24, 2013, you met the requirements of this AD. However, you must still repetitively replace the HMU as required by paragraphs (e)(1)(iii) and (e)(2)(iii) of this AD.
(i) Alternative Methods of Compliance (AMOCs)

The Manager, Engine Certification Office, FAA, may approve AMOCs to this AD. Use the procedures found in 14 CFR 39.19 to make your request.
(j) Related Information

(1) For more information about this AD, contact Frederick Zink, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; phone: 781–238–7779; fax: 781–238–7199; email: frederick.zink@faa.gov.

(2) Refer to MCAI European Aviation Safety Agency Airworthiness Directive 2013– 0171, dated July 30, 2013. You may examine the AD on the Internet at http:// www.regulations.gov by searching for and locating it in Docket No. FAA–2007–27009.

(3) Turbomeca S.A. MSB No. 292 73 2818, Version D, dated June 24, 2013 and Turbomeca S.A. SB No. 292 73 2157, Version C, dated July 17, 2013, and Turbomeca S.A. SB No. 292 73 2105, Version B, dated December 16, 2010, pertain to the subject of this AD and can be obtained from Turbomeca S.A. using the contact information in paragraph (j)(4) of this AD.

(4) For service information identified in this AD, contact Turbomeca, S.A., 40220 Tarnos, France; phone: 33 (0)5 59 74 40 00; telex: 570 042; fax: 33 (0)5 59 74 45 1.

(5) You may view this service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA. For information on the availability of this material at the FAA, call 781–238–7125.

Issued in Burlington, Massachusetts, on December 11, 2013. Robert J. Ganley, Acting Assistant Directorate Manager, Engine & Propeller Directorate, Aircraft Certification Service.
[FR Doc. 2013–30488 Filed 12–23–13; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2013–1029; Directorate Identifier 2013–NM–177–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; Bombardier, Inc. Airplanes** 

**AGENCY :**  Federal Aviation Administration (FAA), DOT.

**ACTION :**  Notice of proposed rulemaking (NPRM).

**SUMMARY :**  We propose to supersede airworthiness directive (AD) 2010–13– 04, which applies to certain Bombardier, Inc. Model DHC–8–400 series airplanes. AD 2010–13–04 requires modifying the nose landing gear (NLG) trailing arm. Since we issued AD 2010–13–04, we received a report of several missing or damaged pivot pin retention bolts. This proposed AD would require installing a new pivot pin retention mechanism. This proposed AD would also add airplanes to the applicability. We are proposing this AD to prevent failure of the pivot pin retention bolt, which could result in a


### 77616 Federal Register / Vol. 78, No. 247 / Tuesday, December 24, 2013 / Proposed Rules

loss of directional control or loss of a NLG tire during take-off or landing.

**DATES :**  We must receive comments on this proposed AD by February 7, 2014.

**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: (202) 493–2251.

• 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, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Bombardier, Inc., Q-Series Technical Help Desk, 123 Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416–375– 4000; fax 416–375–4539; email thd.qseries@aero.bombardier.com; Internet http://www.bombardier.com

. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425–227–
1221. Examining the AD Docket

You may examine the AD docket on the Internet at http:// www.regulations.gov; or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the MCAI, the regulatory evaluation, any comments received, and other information. The street address for the Docket Operations office (telephone (800) 647–5527) is in the **ADDRESSES** section. Comments will be available in the AD docket shortly after receipt.

**FOR FURTHER INFORMATION CONTACT :**  Ricardo Garcia, Aerospace Engineer, Airframe and Mechanical Systems Branch, ANE–171, FAA, New York Aircraft Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, New York 11590; telephone (516) 228– 7331; fax (516) 794–5531.

**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–2013–1029; Directorate Identifier 2013–NM–177–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 based on 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 June 10, 2010, we issued AD 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010). AD 2010–13– 04 requires actions intended to address an unsafe condition on the products listed above.

Since we issued AD 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010), Transport Canada Civil Aviation (TCCA), which is the aviation authority for Canada, has issued Canadian Airworthiness Directive CF– 2009–29R1, dated August 14, 2013 (referred to after this as the Mandatory Continuing Airworthiness Information, or ‘‘the MCAI’’), to correct an unsafe condition for the specified products. The MCAI states:

Two in-service incidents have been reported on DHC–8 Series 400 aircraft in which the nose landing gear (NLG) trailing arm pivot pin retention bolt (part number NAS6204–13D) was damaged. One incident involved the left hand NLG tire which ruptured on take-off. Investigation determined that the retention bolt failure was due to repeated contact of the castellated nut with the towing device including both the towbar and the towbarless rigs. The loss of the retention bolt allowed the pivot pin to migrate from its normal position and resulted in contact with and rupture of the tire. The loss of the pivot pin could compromise retention of the trailing arm and could result in a loss of directional control due to loss of nose wheel steering. The loss of an NLG tire or the loss of directional control could adversely affect the aircraft during take off or landing.

To prevent the potential failure of the pivot pin retention bolt, Bombardier Aerospace has developed a modification which includes a new retention bolt, a reverse orientation of the retention bolt and a rework of the weight on wheel (WOW) proximity sensor cover to provide clearance for the re-oriented retention bolt.

Since the original issue of this [Canadian] AD [which corresponds to AD 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010)], there have been several reports of pivot pin retention bolts found missing or damaged. Additional investigation determined that the failures were caused by high contact stresses on the retention bolt due to excessive frictional torque on the pivot pin and an adverse tolerance condition at the retention bolt.

Revision 1 of this [Canadian] AD mandates the installation of a new pivot pin retention mechanism.

This proposed AD would also add airplanes to the applicability. AD 2010– 13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010), affected Model DHC–8–400 series airplanes, serial numbers 4001, 4003, 4004, 4006, and 4008 through 4238 inclusive. This proposed AD would affect serial numbers 4001 through 4435 inclusive. You may examine the MCAI in the AD docket on the Internet at http:// www.regulations.gov by searching for and locating it in Docket No. FAA–
2013–1029.

Relevant Service Information

Bombardier, Inc. has issued Service Bulletin 84–32–110, Revision A, dated April 8, 2013. The actions described in this service information are intended to correct the unsafe condition identified in the MCAI. FAA’s Determination and Requirements of This Proposed AD

This product has been approved by the aviation authority of another country, and is approved for operation in the United States. Pursuant to our bilateral agreement with the State of Design Authority, we have been notified of the unsafe condition described in the MCAI and service information referenced above. We are proposing this AD because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. Costs of Compliance

We estimate that this proposed AD affects 383 airplanes of U.S. registry.

We estimate the following costs to comply with this proposed AD:


### 77617 Federal Register / Vol. 78, No. 247 / Tuesday, December 24, 2013 / Proposed Rules

E STIMATED 

### COSTS

Action Labor cost Parts cost Cost per product Cost on U.S. operators

Modification of the NLG trailing arm [retained actions from

AD 2010-13-04, Amendment 39-16335 (75 FR 35622, June 23, 2010)]. 3 work-hours × $85 per hour = $255. $100 $355 $22,365

Installation of new pivot pin retention mechanism [new proposed action]. 2 work-hours × $85 per hour = $170. None 170 65,110

According to the manufacturer, some of the costs of this proposed AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate 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 proposed 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 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 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);

3. Will not affect intrastate aviation in Alaska; and

4. 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. 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 FAA amends § 39.13 by removing airworthiness directive (AD) 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010), and adding the following new AD:
Bombardier, Inc.: Docket No. FAA–2013– 1029; Directorate Identifier 2013–NM– 177–AD.
(a) Comments Due Date

We must receive comments by February 7,
2014.
(b) Affected ADs

This AD supersedes AD 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010).
(c) Applicability

This AD applies to Bombardier, Inc. Model DHC–8–400, –401, and –402 airplanes, certificated in any category, serial numbers 4001 through 4435 inclusive.
(d) Subject

Air Transport Association (ATA) of America Code 32, Landing Gear.

(e) Reason

This AD was prompted by a report of several missing or damaged pivot pin retention bolts. We are issuing this AD to prevent failure of the pivot pin retention bolt, which could result in a loss of directional control or a NLG tire during take-off or landing.
(f) Compliance

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

This paragraph restates the requirements of paragraph (f)(1) of AD 2010–13–04, Amendment 39–16335 (75 FR 35622, June 23, 2010), with no changes. For airplanes having serial numbers 4001, 4003, 4004, 4006, and 4008 through 4238 inclusive: Within 2,000 flight hours after July 28, 2010 (the effective date of AD 2010–13–04), modify the NLG trailing arm by incorporating Bombardier Modification Summary 4– 113599, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84–32–65, Revision A, dated March 2, 2009.
(h) New Requirement of This AD: Installing a New Pivot Pin Retention Mechanism

For airplanes having serial numbers 4001 through 4435 inclusive: Within 6,000 flight hours or 36 months after the effective date of this AD, whichever occurs first, install a new pivot pin retention mechanism by incorporating Bombardier Modification Summary 4–113749, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84–32–110, Revision A, dated April 8, 2013.
(i) Credit for Actions Accomplished in Accordance With Previous Service Information

(1) This paragraph provides credit for actions required by paragraph (g) of this AD, if those actions were performed before July 28, 2010 (the effective date of AD 2010–13– 04, Amendment 39–16335 (75 FR 35622, June 23, 2010)), using the Accomplishment Instructions of Bombardier Service Bulletin 84–32–65, dated December 17, 2008, which is not incorporated by reference in this AD.

(2) This paragraph provides credit for actions required by paragraph (h) of this AD, if those actions were performed before the effective date of this AD using Bombardier Service Bulletin 84–32–110, dated December 21, 2012, which is not incorporated by reference in this AD.
(j) Other FAA AD Provisions

The following provisions also apply to this AD:

(1) Alternative Methods of Compliance (AMOCs): The Manager, ANE–170, New York Aircraft Certification Office (ACO), FAA, has


### 77618 Federal Register / Vol. 78, No. 247 / Tuesday, December 24, 2013 / Proposed Rules

the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the ACO, send it to ATTN: Program Manager, Continuing Operational Safety, FAA, New York ACO, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516–228–7300; fax 516–794–5531. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office. The AMOC approval letter must specifically reference this AD.

(2) Airworthy Product: For any requirement in this AD to obtain corrective actions from a manufacturer, use these actions if they are FAA-approved. Corrective actions are considered FAA-approved if they were approved by the State of Design Authority (or its delegated agent, or by the DAH with a State of Design Authority’s design organization approval). For a repair method to be approved, the repair approval must specifically refer to this AD. You are required to ensure the product is airworthy before it is returned to service.

(k) Related Information

(1) Refer to Mandatory Continuing Airworthiness Information (MCAI) Canadian Airworthiness Directive CF–2009–29R1, dated August 14, 2013, for related information. This MCAI may be found in the AD docket on the Internet at http:// www.regulations.gov by searching for and locating it in Docket No. FAA–2013–1029.

(2) For service information identified in this AD, contact Bombardier, Inc., Q-Series Technical Help Desk, 123 Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416–375–4000; fax 416–375–4539; email thd.qseries@aero.bombardier.com;
Internet http://www.bombardier.com. You may review copies of this service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425–227–1221.

Issued in Renton, Washington, on December 11, 2013. John P. Piccola, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2013–30468 Filed 12–23–13; 8:45 am]

**BILLING CODE 4910–13–P DEPARTMENT OF TRANSPORTATION** 

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2013–1057; Directorate Identifier 2013–CE–041–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; M7 Aerospace LLC Airplanes** 

**AGENCY :**  Federal Aviation Administration (FAA), DOT.

**ACTION :**  Notice of proposed rulemaking (NPRM).

**SUMMARY :**  We propose to adopt a new airworthiness directive (AD) for all M7 Aerospace LLC Models SA226–AT, SA226–T, SA226–T(B), SA226–TC, SA227–AC (C–26A), SA227–AT, SA227–BC (C–26A), SA227–CC, SA227– DC (C–26B), SA227–TT, SA26–AT, and SA26–T airplanes. This proposed AD was prompted by reports of airplanes with multiple fatigue cracks in the FS 69.31 front pressure bulkhead. This proposed AD would require repetitively inspecting (visually) the FS 51.31 front pressure bulkhead on SA26 series airplanes and FS 69.31 front pressure bulkhead on SA226 and SA227 series airplanes for cracks, and repairing any cracked bulkhead. This proposed AD also requires reporting certain inspection results to M7 Aerospace LLC. We are proposing this AD to correct the unsafe condition on these products.

**DATES :**  We must receive comments on this proposed AD by February 7, 2014.

**ADDRESSES :**  You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.

• Fax: 202–493–2251.

• 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: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact M7 Aerospace LP, 10823 NE Entrance Road, San Antonio, Texas 78216; phone: (210) 824–9421; fax: (210) 804–7766; Internet: http://www.m7aerospace.com; email: none. You may view this referenced service information at the FAA, Small Airplane Directorate, 901 Locust, Kansas City, Missouri 64106. For information on the availability of this material at the FAA, call 816–329–4148. Examining the AD Docket

You may examine the AD docket on the Internet at http:// www.regulations.gov by searching and locating Docket Number FAA–2013– 1057; 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 (phone: 800–647–5527) is in the

**ADDRESSES** section. Comments will be available in the AD docket shortly after receipt.

**FOR FURTHER INFORMATION CONTACT :**  Andrew McAnaul, Aerospace Engineer, FAA, ASW–150 (c/o San Antonio MIDO), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; phone: (210) 308–3365; fax: (210) 308–3370; email: andrew.mcanaul@faa.gov.

**SUPPLEMENTARY INFORMATION :** 
Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the **ADDRESSES** section. Include ‘‘Docket No. FAA– 2013–1057; Directorate Identifier 2013– CE–041–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

We received reports of two M7 Aerospace LLC Model SA227 airplanes with multiple fatigue cracks in the FS 69.31 front pressure bulkhead. Thecracks are located in the radii of the lefthand and right-hand part number 27– 21027 frames. The cracks were discovered by maintenance personnel after the flight crew reported trouble maintaining normal cabin pressure. The root cause for multiple site fatiguecracking is the normal ground-airground pressure cycles.