27966 Federal Register / Vol. 75, No. 96 / Wednesday, May 19, 2010 / Proposed Rules 

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); 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. 

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 adding 

the following new AD: 

Rolls-Royce plc: Docket No. FAA–2009– 

1157; Directorate Identifier 2009–NE– 

26–AD. 

Comments Due Date 

(a) We must receive comments by July 6, 

2010. 

Affected Airworthiness Directives (ADs) 

(b) None. 

Applicability 

(c) This AD applies to Rolls-Royce plc 

RB211–22B series and RB211–524B4–D–02, 

RB211–524D4–19, RB211–524D4–39, 

RB211–524D4–B–19, RB211–524D4–B–39, 

RB211–524D4X–19, and RB211–524D4X–B– 

19 model turbofan engines. These engines are 

installed on, but not limited to, Boeing 747 

series and Lockheed L–1011 series airplanes. 

Reason 

(d) This AD results from: 

Several low pressure turbine (LPT) shafts 

have been found with cracks originating from 

the rear cooling air holes. The cracks were 

found at normal component overhaul, by the 

standard Magnetic Particle Inspection (MPI) 

technique defined in the associated engine 

manual. The cracks have been found to 

initiate from corrosion pits. Propagation of a 

crack from the rear cooling air holes may 

result in shaft failure and subsequently in an 

uncontained Low Pressure Turbine failure. 

For the reasons stated above, this AD requires 

the inspection of the affected engines’ LPT 

shafts and replacement of the shaft, as 

necessary. 

We are issuing this AD to detect cracks, 

initiated by corrosion pits, originating from 

the rear cooling air holes, which could result 

in shaft failure and subsequently in an 

uncontained failure of the LPT and damage 

to the airplane. 

Actions and Compliance 

(e) Unless already done, do the following 

actions. 

Initial Inspection Requirements 

(1) At the next engine shop visit after the 

effective date of this AD when the LPT shaft 

is completely disassembled to piece-part 

level, inspect the LPT shaft using paragraphs 

3.A.(1)(a) through 3.A.(4)(l) of the 

accomplishment instructions of Rolls-Royce 

Service Bulletin RB.211–72–AF336, dated 

October 24, 2007. 

Repetitive Inspection Requirements 

(2) Thereafter, reinspect the LPT shaft 

using paragraphs 3.A.(1)(a) through 3.A.(4)(l) 

of the accomplishment instructions of RollsRoyce Service Bulletin RB.211–72–AF336, 

dated October 24, 2007 and the following 

schedule in Table 1 of this AD: 

TABLE 1—REPETITIVE INSPECTION INTERVAL BY ENGINE MODEL

Engine model Maximum time between inspections (engine cycles) 

(i) RB211–22B Series, all models ............................................................ 3,500. 

(ii) RB211–524B4–D–02 ........................................................................... 4,000. 

(iii) RB211–524D4–19, RB211–524D4–39, RB211–524D4–B–19, 

RB211–524D4–B–39, RB211–524D4X–19 and RB211–524D4X–B– 

19.

At the next engine shop visit after the last inspection. 

Remove Parts With Cracks 

(3) Remove cracked LPT shafts, found 

using paragraphs (e)(1) or (e)(2) of this AD, 

from service before further flight. 

Definitions 

(4) For the purpose of this AD, an engine 

shop visit is the induction of an engine into 

the shop for maintenance involving the 

separation of pairs of major mating engine 

flanges. The separation of engine flanges 

solely for the purposes of transportation 

without subsequent engine maintenance does 

not constitute an engine shop visit. 

Other FAA AD Provisions 

(f) Alternative Methods of Compliance 

(AMOCs): The Manager, Engine Certification 

Office, FAA, has the authority to approve 

AMOCs for this AD, if requested using the 

procedures found in 14 CFR 39.19. 

Related Information 

(g) Refer to MCAI EASA Airworthiness 

Directive 2007–0310 R1, dated January 8, 

2008, and Rolls-Royce plc Alert Service 

Bulletin RB.211–72–AF336, dated October 

24, 2007, for related information. Contact 

Rolls-Royce plc P.O. Box 31, Derby, DE24 

8BJ, United Kingdom; telephone 044 1332 

242424; fax 044 1332 249936, for a copy of 

this service information. 

(h) Contact Tara Chaidez, Aerospace 

Engineer, Engine Certification Office, FAA, 

Engine and Propeller Directorate, 12 New 

England Executive Park, Burlington, MA 

01803; e-mail: tara.chaidez@faa.gov; 

telephone (781) 238–7773; fax (781) 238– 

7199, for more information about this AD. 

Issued in Burlington, Massachusetts, on 

May 12, 2010. 

Peter A. White, 

Assistant Manager, Engine and Propeller 

Directorate, Aircraft Certification Service. 

[FR Doc. 2010–11998 Filed 5–18–10; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2010–0480; Directorate 

Identifier 2010–NM–035–AD] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Model 747–400 and 747– 

400D Series Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for certain 

Model 747–400 and 747–400D series 

airplanes. This proposed AD would 


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Federal Register / Vol. 75, No. 96 / Wednesday, May 19, 2010 / Proposed Rules 27967 

require installing aluminum gutter 

reinforcing brackets to the forward and 

aft drip shield gutters of the main 

equipment center (MEC); and adding a 

reinforcing fiberglass overcoat to the top 

surface of the MEC drip shield, 

including an inspection for cracking and 

holes in the MEC drip shield, and 

corrective actions if necessary. This 

proposed AD also provides for an option 

to install an MEC drip shield drain 

system, which, if accomplished, would 

extend the compliance time for adding 

the reinforcing fiberglass overcoat to the 

top surface of the MEC drip shield. This 

proposed AD results from a report 

indicating that an operator experienced 

a multi-power system loss in-flight of 

#1, #2, and #3 alternating current (AC) 

electrical power systems located in the 

MEC. We are proposing this AD to 

prevent water penetration into the MEC, 

which could result in the loss of flight 

critical systems. 

DATES: We must receive comments on 

this proposed AD by July 6, 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: 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 20590, between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. 

For service information identified in 

this proposed AD, contact Boeing 

Commercial Airplanes, Attention: Data 

& Services Management, P.O. Box 3707, 

MC 2H–65, Seattle, Washington 98124– 

2207; telephone 206–544–5000, 

extension 1; fax 206–766–5680; e-mail 

me.boecom@boeing.com; Internet 

https://www.myboeingfleet.com. You 

may review copies of the referenced 

service information at the FAA, 

Transport Airplane Directorate, 1601 

Lind Avenue, SW., Renton, Washington. 

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 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 800–647–5527) is in the 

ADDRESSES section. Comments will be 

available in the AD docket shortly after 

receipt. 

FOR FURTHER INFORMATION CONTACT: 

Marcia Smith, Aerospace Engineer, 

Cabin Safety and Environmental 

Systems Branch, ANM–150S, FAA, 

Seattle Aircraft Certification Office, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; telephone 

(425) 917–6484; fax (425) 917–6590. 

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–2010–0480; Directorate Identifier 

2010–NM–035–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 a report indicating that 

an operator experienced a multi-power 

system loss in-flight of #1, #2, and #3 

AC electrical power systems located in 

the main equipment center (MEC). The 

forward MEC drip shield gutters and 

exhaust plenum have each been 

identified as part of the leak path into 

the MEC. Multiple operators have 

reported MEC drip shield gutter and 

upper surface cracks. These cracks can 

allow water to penetrate the MEC drip 

shield and enter the MEC. This 

condition, if not corrected, could allow 

water penetration into the MEC, which 

could result in the loss of flight critical 

systems. 

Relevant Service Information 

We have reviewed Boeing Alert 

Service Bulletin 747–25A3555, dated 

November 4, 2009. The service bulletin 

describes procedures for installing 

aluminum gutter reinforcing brackets to 

the forward and aft drip shield gutters 

of the main equipment center (MEC). 

The service bulletin also describes 

procedures for adding a reinforcing 

fiberglass overcoat to the top surface of 

the MEC drip shield, including a general 

visual inspection for cracking and holes 

in the top surface of the MEC drip 

shield, and corrective actions if 

necessary. The corrective actions 

include repairing any crack or hole 

found. The service bulletin also 

describes procedures for an option to 

install an MEC drip shield drain system, 

which, if accomplished, would extend 

the compliance time for adding the 

reinforcing fiberglass overcoat. 

FAA’s Determination and Requirements 

of This Proposed AD 

We are proposing this AD because we 

evaluated all relevant information and 

determined the unsafe condition 

described previously is likely to exist or 

develop in other products of the same 

type design. This proposed AD would 

require accomplishing the actions 

specified in the service information 

described previously. 

Costs of Compliance 

We estimate that this proposed AD 

would affect 71 airplanes of U.S. 

registry. The following table provides 

the estimated costs, depending on 

airplane configuration, for U.S. 

operators to comply with this proposed 

AD. 

TABLE—ESTIMATED COSTS

Action Work hours 

Average 

labor rate 

per hour 

Parts Cost per product 

Number of 

U.S.- 

registered 

airplanes 

Fleet cost 

Install Brackets .......... Between 7 and 8 1 .. $85 None ........................ Up to $680 1 ............ 71 Up to $48,280.1

Add Overcoat ............ Between 11 and 12 1 85 None ........................ Up to $1,020 1 ......... 71 Up to $72,420.1


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27968 Federal Register / Vol. 75, No. 96 / Wednesday, May 19, 2010 / Proposed Rules 

TABLE—ESTIMATED COSTS—Continued 

Action Work hours 

Average 

labor rate 

per hour 

Parts Cost per product 

Number of 

U.S.- 

registered 

airplanes 

Fleet cost 

Install Optional MEC 

Drip Shield Drain 

System.

Between 12 and 13 1 85 Up to $8,982 1 ......... Up to $10,087 1 ....... 71 Up to $716,177.1

1 Depending on work package. 

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 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), 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. 

You can find our regulatory 

evaluation and the estimated costs of 

compliance 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 adding 

the following new AD: 

The Boeing Company: Docket No. FAA– 

2010–0480; Directorate Identifier 2010– 

NM–035–AD. 

Comments Due Date 

(a) We must receive comments by July 6, 

2010. 

Affected ADs 

(b) None. 

Applicability 

(c) This AD applies to The Boeing 

Company Model 747–400 and 747–400D 

series airplanes, certificated in any category; 

as identified in Boeing Alert Service Bulletin 

747–25A3555, dated November 4, 2009. 

Subject 

(d) Air Transport Association (ATA) of 

America Code 25: Equipment/Furnishings. 

Unsafe Condition 

(e) This AD results from a report indicating 

that an operator experienced a multi-power 

system loss in-flight of #1, #2, and #3 

alternating current electrical power systems 

located in the main equipment center (MEC). 

The Federal Aviation Administration is 

issuing this AD to prevent water penetration 

into the MEC, which could result in loss of 

flight critical systems. 

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. 

Modification 

(g) Do the actions specified in either 

paragraph (g)(1) or (g)(2) of this AD, at the 

times specified in those paragraphs, in 

accordance with the Accomplishment 

Instructions of Boeing Alert Service Bulletin 

747–25A3555, dated November 4, 2009 (‘‘the 

service bulletin’’). 

(1) Within 24 months after the effective 

date of this AD, install the reinforcing 

brackets of the MEC drip shield aluminum 

gutter, in accordance with Work Package 1 of 

the Accomplishment Instructions of the 

service bulletin; and add a reinforcing 

fiberglass overcoat to the top surface of the 

MEC drip shield, including doing a general 

visual inspection for cracking and holes in 

the top surface of the MEC drip shield, and 

doing all applicable corrective actions, in 

accordance with Work Package 3 of the 

Accomplishment Instructions of the service 

bulletin. Do all applicable corrective actions 

before further flight after doing the general 

visual inspection. 

(2) Do the actions specified in paragraphs 

(g)(2)(i) and (g)(2)(ii) of this AD. 

(i) Within 24 months after the effective 

date of this AD, install the reinforcing 

brackets of the MEC drip shield aluminum 

gutter, in accordance with Work Package 1 of 

the Accomplishment Instructions of the 

service bulletin; and install a MEC drip 

shield drain system, in accordance with 

Work Package 2 of the Accomplishment 

Instructions of the service bulletin. 

(ii) Within 96 months after the effective 

date of this AD, add a reinforcing fiberglass 

overcoat to the top surface of the MEC drip 

shield, including doing a general visual 

inspection for cracking and holes in the top 

surface of the MEC drip shield, and doing all 

applicable corrective actions, in accordance 

with Work Package 3 of the Accomplishment 

Instructions of the service bulletin. Do all 

applicable corrective actions before further 

flight after doing the general visual 

inspection. 

Alternative Methods of Compliance 

(AMOCs) 

(h)(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: 

Marcia Smith, Aerospace Engineer, Cabin 

Safety and Environmental Systems Branch, 

ANM–150S, FAA, Seattle Aircraft 

Certification Office, 1601 Lind Avenue, SW., 

Renton, Washington 98057–3356; telephone 

(425) 917–6484; fax (425) 917–6590. 

Information may be e-mailed to: 9-ANMSeattle-ACO-AMOC-Requests@faa.gov. 

(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 


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Federal Register / Vol. 75, No. 96 / Wednesday, May 19, 2010 / Proposed Rules 27969 

(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. 

Issued in Renton, Washington, on May 5, 

2010. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2010–11901 Filed 5–18–10; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2010–0481; Directorate 

Identifier 2009–NM–192–AD] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Model 737–100 and –200 

Series Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for certain 

Model 737–100 and –200 series 

airplanes. This proposed AD would 

require repetitive inspections for 

cracking and damaged fasteners of 

certain fuselage frames and stub beams, 

and corrective actions if necessary. For 

certain airplanes, this proposed AD 

would also require repetitive 

inspections for cracking of the inboard 

chord fastener hole of the frame at body 

station 639, stringer S–16, and 

corrective actions if necessary. For 

certain airplanes, this proposed AD 

would also require an inspection to 

determine the edge margin of the lower 

chord. For airplanes with a certain short 

edge margin, this proposed AD requires 

repetitive inspections for cracking, and 

corrective actions if necessary; replacing 

the lower chord terminates the 

repetitive inspections. This proposed 

AD requires an eventual preventive 

modification. For certain airplanes, 

doing the modification or a repair 

would terminate the repetitive 

inspections for the repaired or modified 

frame only. For airplanes on which the 

modification or repair is done at certain 

body stations, this proposed AD would 

require repetitive inspections for 

cracking of certain frame webs and 

inner and outer chords, and corrective 

actions if necessary. For certain other 

airplanes, this proposed AD requires a 

modification which includes reinforcing 

the body frame inner chords, replacing 

the stub beam upper chords and attach 

angles, and reinforcing the stub beam 

web. This proposed AD results from 

reports of fatigue cracks at certain frame 

sections, in addition to stub beam 

cracking, caused by high flight cycle 

stresses from both pressurization and 

maneuver load. We are proposing this 

AD to detect and correct fatigue 

cracking of certain fuselage frames and 

stub beams, and possible severed 

frames, which could result in reduced 

structural integrity of the frames. This 

reduced structural integrity can increase 

loading in the fuselage skin, which will 

accelerate skin crack growth and result 

in rapid decompression of the fuselage. 

DATES: We must receive comments on 

this proposed AD by July 6, 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: 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 20590, 

between 9 a.m. and 5 p.m., Monday 

through Friday, except Federal holidays. 

For service information identified in 

this proposed AD, contact Boeing 

Commercial Airplanes, Attention: Data 

& Services Management, P.O. Box 3707, 

MC 2H–65, Seattle, Washington 98124– 

2207; telephone 206–544–5000, 

extension 1, fax 206–766–5680; e-mail 

me.boecom@boeing.com; Internet 

https://www.myboeingfleet.com. You 

may review copies of the referenced 

service information at the FAA, 

Transport Airplane Directorate, 1601 

Lind Avenue, SW., Renton, Washington. 

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 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 800–647–5527) is in the 

ADDRESSES section. Comments will be 

available in the AD docket shortly after 

receipt. 

FOR FURTHER INFORMATION CONTACT: 

Wayne Lockett, Aerospace Engineer, 

Airframe Branch, ANM–120S, FAA, 

Seattle Aircraft Certification Office, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; telephone 

(425) 917–6447; fax (425) 917–6590. 

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–2010–0481; Directorate Identifier 

2009–NM–192–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 have received reports of fatigue 

cracks found at certain frame sections, 

in addition to stub beam cracking, 

caused by high flight cycle stresses from 

both pressurization and maneuver load. 

Numerous cracks were found in the 

shear ties, webs, and inboard and 

outboard chords of the overwing body 

frames and stub beams between body 

stations 559 and 639. Cracks were also 

found in the webs, attach angles, and 

the upper and lower chords of the stub 

beams. There were reports of sheared 

fasteners in the overwing body frames 

and stub beams in the same location. 

Fatigue cracking of certain fuselage 

frames and stub beams, if not detected 

and corrected, and possible severed 

frames, could result in reduced 

structural integrity of the frames. This 

reduced structural integrity can increase 

loading in the fuselage skin, which will 

accelerate skin crack growth and result 

in rapid decompression of the fuselage. 

Relevant Service Information 

We have reviewed Boeing Service 

Bulletin 737–53–1061, Revision 4, 

including Addendum, dated July 16, 

1992. For airplanes on which a repair 

(Part III) or preventive modification 

(Part II) has not been done, the service 

bulletin describes procedures for 


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