Airworthiness Directives; Boeing Model 737-300 Series Airplanes Equipped With a Pemco Aeroplex Main Deck Cargo Door That Has Been Modified in Accordance With Supplemental Type Certificate (STC) SA2969S0

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-173-AD; Amendment 39-8940; AD 94-12-12]

Airworthiness Directives; Boeing Model 737-300 Series Airplanes

Equipped With a Pemco Aeroplex Main Deck Cargo Door That Has Been

Modified in Accordance With Supplemental Type Certificate (STC)

SA2969S0

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Boeing Model 737-300 series airplanes, that

requires replacement of the forward and aft hinge shims and the lower

hinge fairings of the main cargo door with new shims and fairings. This

amendment is prompted by reports of a slight separation between the end

hinge shims and the cargo door; this separation can cause bending loads

on the fasteners. The actions specified by this AD are intended to

prevent fatigue failure of the hinge fasteners, loss of structural

integrity of the cargo door hinge, possible loss of the cargo door, and

subsequent rapid decompression of the airplane.

DATES: Effective July 20, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of July 20, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Pemco Aeroplex Inc., P.O. Box 2287, Birmingham, Alabama

34201. This information may be examined at the Federal Aviation

Administration (FAA), Transport Airplane Directorate, Rules Docket,

1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small

Airplane Directorate, Atlanta Aircraft Certification Office, suite

210C, 1669 Phoenix Parkway, Atlanta, Georgia; or at the Office of the

Federal Register, 800 North Capitol Street NW., suite 700, Washington,

DC.

FOR FURTHER INFORMATION CONTACT: Curtis Jackson, Aerospace Engineer,

Airframe Branch, ACE-120A, FAA, Small Airplane Directorate, Atlanta

Aircraft Certification Office, suite 210C, 1669 Phoenix Parkway,

Atlanta, Georgia 30349; telephone (404) 991-2910; fax (404) 991-3606.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to certain Boeing 737-300 series

airplanes was published in the Federal Register on December 6, 1993 (58

FR 64198). That action proposed to require replacement of the forward

and aft hinge shims and the lower hinge fairings of the main cargo door

with new shims and fairings.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received. -

Two commenters support the proposal. -

One commenter considers there is no justification for issuing the

proposed rule, since most of the affected airplanes have already been

modified in accordance with the proposed requirements. The FAA does not

concur. Although the commenter has provided the FAA with data

indicating that the proposed modification has been accomplished on all

airplanes currently on the U.S. Register, this data did not provide

positive indication, verified by FAA personnel, that the modification

had been accomplished on airplanes not currently on the U.S. Register.

Should one of these affected airplanes be imported to the U.S. in the

future, this AD is necessary in order to ensure that the required

actions are accomplished on the airplane prior to it being placed on

the U.S. Register. Further, as is indicated in the final rule,

operators are given ``credit'' for previously accomplishing the

requirements of the rule; therefore, no further action is required on

the part of the operators in these cases. -

Another commenter contends that there is no justification for the

proposed AD, since the Supplemental Type Certificate (STC) holder

(Pemco) has not indicated that the referenced Pemco service bulletin

concerns an airworthiness problem. The commenter states that Pemco has

portrayed the service bulletin as addressing only a reliability

problem. The FAA does not concur. In developing this AD action, the FAA

reviewed the relevant data which indicated that this STC door design

allows slight separation between the end hinge shims and the cargo door

during pressurization cycles; such separation can cause increased

bending loads on the door hinge fasteners. The FAA determined that this

situation constitutes an unsafe condition since, if not corrected, it

could lead to fatigue failure of the hinge fasteners, loss of

structural integrity of the cargo door hinge, possible loss of the

cargo door, and subsequent rapid decompression of the airplane.

Regardless of whether or not the wording in the service bulletin

describes the procedures specified within it as addressing an

airworthiness problem, the FAA finds that accomplishment of those

procedures will serve to eliminate the identified unsafe condition.

One commenter suggests that the wording that identifies the

location of the affected cargo door be clarified. The commenter points

out that the notice identified this door as the ``main cargo door;''

however, a more correct identification would be ``main deck cargo

door.'' The FAA concurs and has changed the pertinent wording in the

final rule accordingly. -

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the change previously

described. The FAA has determined that this change will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 11 Model 737-300 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 2

airplanes of U.S. registry will be affected by this AD, that it will

take approximately 280 work hours per airplane to accomplish the

required actions, and that the average labor rate is $55 per work hour.

Required parts will be provided by Pemco Aeroplex at no cost to the

operators. Based on these figures, the total cost impact of the AD on

U.S. operators is estimated to be $30,800, or $15,400 per airplane. -

The total cost impact figure discussed above is based on

assumptions that no operator has yet accomplished any of the

requirements of this AD action, and that no operator would accomplish

those actions in the future if this AD were not adopted. However, the

FAA has been advised that all affected U.S.-registered airplanes have

been modified previously in accordance with the requirements of this

AD. Therefore, there is no cost impact of this AD on U.S. operators. -

The regulations adopted herein will not have substantial direct

effects 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, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment. -

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under 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. A final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39 -

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment -

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended] -

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-12-12 Boeing: Amendment 39-8940. Docket 93-NM-173-AD.

-Applicability: Boeing Model 737-300 series airplanes, as listed

in Pemco Aeroplex Inc. Service Bulletin 737-52-0012, dated February

9, 1993; equipped with a Pemco Aeroplex main deck cargo door that

has been modified in accordance with Supplemental Type Certificate

(STC) SA2969S0; certificated in any category. -

Compliance: Required as indicated, unless accomplished

previously. -

To prevent fatigue failure of the hinge fasteners, loss of

structural integrity of the cargo door hinge, possible loss of the

cargo door, and subsequent rapid decompression of the airplane,

accomplish the following: -

(a) Within 12,000 landings from the date of STC SA2969S0

installation or within 6 months after the effective date of this AD,

whichever occurs later, replace the forward and aft hinge shims and

the lower hinge fairings of the main deck cargo door, with new shims

and fairings, in accordance with Pemco Aeroplex Inc. Service

Bulletin 737-52-0012, dated February 9, 1993. -

(b) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Atlanta Aircraft Certification

Office (ACO), FAA, Small Airplane Directorate. Operators shall

submit their requests through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Atlanta ACO.

-Note: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Atlanta ACO.

-(c) Special flight permits may be issued in accordance with

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the airplane to a location where

the requirements of this AD can be accomplished. -

(d) The replacement shall be done in accordance with Pemco

Aeroplex Inc. Service Bulletin 737-52-0012, dated February 9, 1993.

This incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies may be obtained from Pemco Aeroplex Inc. Service Bulletin

737-52-0012, dated February 9, 1993. Copies may be inspected at the

FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,

Washington; or at the FAA, Small Airplane Directorate, Atlanta

Aircraft Certification Office, Suite 210C, 1669 Phoenix Parkway,

Atlanta, Georgia; or at the Office of the Federal Register, 800

North Capitol Street, NW., suite 700, Washington, DC. -

(e) This amendment becomes effective on July 20, 1994..

Issued in Renton, Washington, on June 8, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-14361 Filed 6-17-94; 8:45 am]

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