Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model EMB-120RT and -120ER Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-261-AD; Amendment 39-11315; AD 99-19-28]

RIN 2120-AA64

Airworthiness Directives; Empresa Brasileira de Aeronautica S.A.

(EMBRAER) Model EMB-120RT and -120ER Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to certain EMBRAER Model EMB-120RT and -120ER series

airplanes, that requires repetitive detailed visual inspections to

detect discrepancies of the brake assemblies on the main landing gear

(MLG), and replacement of the brake assemblies with new or serviceable

brake assemblies, if necessary. This amendment is prompted by reports

of fatigue cracking or splitting of the brake stator disk at the

thermal expansion slots. The actions specified by this AD are intended

to prevent failure of the brake assemblies of the MLG due to cracking

or splitting of the stator disk, which could result in loss of brake

effectiveness and could cause the airplane to leave the runway surface.

DATES: Effective October 20, 1999.

The incorporation by reference of certain publications listed in

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

of October 20, 1999.

ADDRESSES: The service information referenced in this AD may be

obtained from BFGoodrich, Aircraft Wheels and Brakes, P.O. Box 340,

Troy, Ohio, 45373. 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, One Crown

Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia; or at the

Office of the Federal Register, 800 North Capitol Street, NW., suite

700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Rob Capezzuto, Aerospace Engineer,

Systems and Flight Test Branch, ACE-116A, FAA, Small Airplane

Directorate, Atlanta Aircraft Certification Office, One Crown Center,

1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 30349; telephone

(770) 703-6071; fax (770) 703-6097.

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 EMBRAER Model EMB-120RT

and -120ER series airplanes was published in the Federal Register on

October 14, 1998 (63 FR 55059). That action proposed to require

repetitive visual inspections to detect discrepancies of the brake

assemblies on the main landing gear (MLG), and replacement of the brake

assemblies with new brake assemblies, if necessary.

Comments

Interested persons have been afforded an opportunity to participate

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

the four comments received.

Request to Withdraw Proposed AD

One commenter, the manufacturer, states that it discussed

with the Brazilian airworthiness authority the ``cracked/splitted

stator brakes'' that were impairing the expected service life of the

brakes of Model EMB-120 series airplanes. Upon request by the Brazilian

airworthiness authority, the manufacturer incorporated the inspections

specified by BFGoodrich Service Bulletins 2-1585-32-1 and 2-1479-32-2

into the ``EMB-120 Maintenance Review Board (MRB)'' document, temporary

revision No. 3. The commenter contends that, since the MRB is an FAA-

approved document applicable to all U.S.-registered airplanes and

includes the same inspection procedures as the service bulletins,

issuance of the proposed AD would be a duplication and, therefore, is

unnecessary.

The FAA does not concur. Although the MRB is an FAA-approved

document, the procedures specified in that document are recommended

(rather than mandatory) for U.S. operators. The FAA finds that

accomplishment of the inspections as part of a recommended action in

the MRB report would not ensure an acceptable level of safety. In light

of this and the identified unsafe condition, the FAA has determined

that issuance of this AD is necessary in order to mandate repetitive

detailed visual inspections for discrepancies of the brake assemblies

on the MLG in paragraph (a) of this AD.

One commenter states that the proposed rule is not

justified because the actions required do not effectively prevent brake

rotor failure or promote safety. The commenter suggests that additional

research needs to be accomplished to determine answers to the following

questions. Why are some operators having problems with brake rotors

when others, such as the largest operator of Model EMB-120 series

airplanes in the world, are not? Is the problem of rotor breakage

associated with landing cycles, or is it associated with brake rotor

over-temperature situations? Have there been any runway excursions or

passenger injuries as a result of brake rotor failure on Model EMB-120

series airplanes?

The FAA does not concur that the proposed AD is not justified.

BFGoodrich's investigation of the brake stator rotors indicates that

fatigue cracking began to occur between 600 and 1,000 flight hours,

which clearly shows that a service difficulty does exist with the

rotors. To address this problem, BFGoodrich issued Service Bulletins 2-

1585-32-1 and 2-1479-32-2, both Revision 1, dated June 17, 1998.

Although the exact cause of the cracking is unknown at this time,

BFGoodrich has informed the FAA that the cracking and splitting [of the

brake stator disks] are due to overheat and thermal distortion of the

stator disks. The FAA considers that the number of landing cycles and

over-temperature conditions are related to the identified unsafe

condition. Although no runway excursions or passenger injuries have

been reported as a result of the identified unsafe condition to date,

the FAA has determined that the procedures required by this AD are

necessary to prevent an unsafe condition from occurring and to ensure

continued operational safety. No change to the final rule is necessary

in this regard.

Request to Increase the Compliance Time for the Inspections

Three commenters request that the compliance times for the initial

and repetitive inspections be increased.

One commenter requests revising the initial inspection in paragraph

(a) of the proposed AD to ``within 400 hours after the effective date

of this AD'' and repeating the inspections thereafter ``at an interval

not to exceed 400 hours.'' The commenter contends that such an

extension of the compliance time would allow accomplishment of these

inspection requirements during an operator's regularly scheduled ``A''

checks. The commenter adds that some operators do not have certified

inspectors at remote line stations to support a mandatory inspection

requirement to accomplish the repetitive inspections at each wheel

change, although it is preferred to have

[[Page 49975]]

line mechanics inspect the brakes at each wheel removal.

Another commenter states that the repetitive inspection interval

required by the proposed AD of ``300 landings'' would require very

labor intensive and costly tracking and planning, which would make

operators prone to ``overfly'' errors. The commenter contends that

repetitive inspection intervals should include the option of using

airframe hours and should be based on an operator's existing

maintenance/inspection program, as determined by each operator's

continuing analysis and surveillance system. Based on a sampling of

COEX brake removal data due to stator/disc breakage, an ``A-check''

interval of 400 hours would provide an equivalent level of safety for

our fleet.

Another commenter states that a ``300 cycle re-inspection

requirement'' is impractical and does not increase safety. There is no

documented time at which cracks appear, nor is there any documentation

of crack propagation rates. In addition, the ``300 cycle interval'' at

each wheel change required by the proposed AD appears to be arbitrary

with no supporting data.

The FAA concurs with the commenters' requests to extend the

compliance time for the inspections. Based on information provided by

one of the commenters, the FAA recognizes that ``400 flight hours''

corresponds more closely to the interval representative of most of the

affected operators' normal maintenance schedules, where special

equipment and trained maintenance personnel will be available if

necessary. The FAA does not consider that this extension will adversely

affect safety. Paragraph (a) of the final rule has been changed to

specify the compliance times for the initial detailed visual inspection

as: ``Within 400 flight hours after the effective date of this AD,''

and the repetitive inspections [in paragraphs (a) and (b)] as: ``at an

interval not to exceed 400 flight hours.''

Request to Change Brake Replacement Requirement

Three commenters request changing the proposed AD to require

replacement of the brake assembly with a ``serviceable'' rather than a

``new'' brake assembly. One commenter contends that it is doubtful the

brake manufacturer can maintain production levels to support Model EMB-

120 series airplanes with new replacement units. Another commenter

contends that there is no justification for requiring a new part to be

installed as a replacement because, in every instance, a

``serviceable'' part should be acceptable for replacement.

The FAA concurs that the replacement of discrepant brake assemblies

with serviceable parts is acceptable. The FAA has provided operators

with the option of replacing any discrepant brake assemblies with

either a new or serviceable brake assembly. This option provides

greater flexibility to the operators in meeting the requirements of

this AD and alleviates any problems regarding parts availability, while

still providing an acceptable level of safety for the fleet. The FAA

has revised the preamble and paragraph (b) of the final rule

accordingly.

Request to Consider Adding Brake Assemblies to the Applicability

One commenter requests that the FAA consider whether the

applicability of the proposed AD should include brake assemblies, part

numbers (P/N) 2-1585 and 2-1479-1, that have been modified with parts

manufacturer approval (PMA) heat sink components.

The FAA finds that this AD would apply to airplanes equipped with

brake assemblies having part number (P/N) 2-1585 or 2-1479-1, if those

assemblies have been modified with PMA heat sink components and if the

PMA approval was based on identicality. Such components are identical

to the original part in materials and dimensions and, therefore, may be

subject to the same identified unsafe condition. However, investigation

reveals that the only known PMA's to these brake assemblies were

obtained through test and computation. Because there are no known PMA's

to these brake assemblies that have been obtained through identicality,

no change to the applicability of the final rule is necessary.

Request to Revise the Preamble of the Proposal

One commenter requests revising the Summary of the proposed AD by

clarifying that the brake stator disk is located at the ``thermal

expansion slots'' rather than at the ``cut-out slots.'' The FAA concurs

and has changed the Summary of the final rule accordingly.

That same commenter also requests revising the ``Discussion''

paragraph of the proposed AD to clarify that the cause of the cracking

and splitting are the result of overheat and thermal distortion of the

stator disks, although the exact cause of these conditions have not

been determined at this time. The FAA recognizes that the suggested

change provides improved technical accuracy. However, since the

``Discussion'' paragraph of the preamble to the NPRM is not restated in

the final rule, no change to the final rule is necessary.

That same commenter also requests revising the ``Explanation of

Relevant Service Information'' paragraph of the proposed AD to change

one of the discrepancies listed in that paragraph from ``wear of

plates'' to ``excessive distortion of the wear plates.'' The FAA

acknowledges that the suggested change improves technical accuracy.

Even though the referenced paragraph does not appear in the final rule,

the FAA considers that the suggested change is appropriate for

paragraph (a) of the final rule and has changed that paragraph

accordingly.

Request to Revise the Cost Impact in the Proposed AD

One commenter requests revising the Cost Impact paragraph of the

proposed AD. The commenter states that the referenced service bulletins

estimate that the inspection at a tire change would be 15 minutes per

brake, or one hour per airplane. However, if the inspections were not

accomplished at a tire change, additional time and cost (approximately

2 hours per airplane) would be required to jack the airplane and remove

the wheel/tire assembly to enable the inspection.

The FAA does not concur. As explained earlier in this AD, no

additional time would be required for the inspections because the

compliance times are extended in the final rule, which should allow the

operator to perform the inspection during a tire change. No change to

the final rule was necessary in this regard.

Differences Between Service Bulletin and This AD

Operators should note that BFGoodrich Service Bulletins 2-1585-32-1

and 2-1479-32-2, both Revision 1, dated June 17, 1998, specify an

``examination'' of the brake assembly and a ``visual examination'' of

each stator disk expansion slot. However, this final rule requires a

``detailed visual inspection'' to determine the existence of any

discrepancies of the brake assemblies on the MLG. A note has been added

to the final rule to define that inspection.

Conclusion

After careful review of the available data, including the comment

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

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will

[[Page 49976]]

neither increase the economic burden on any operator nor increase the

scope of the AD.

Interim Action

This is considered to be interim action until final action is

identified, at which time the FAA may consider further rulemaking.

Cost Impact

The FAA estimates that 227 Model EMB-120RT and -120ER series

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

take approximately 1 work hour per airplane to accomplish the required

inspection, and that the average labor rate is $60 per work hour. Based

on these figures, the cost impact of the AD on U.S. operators is

estimated to be $13,620, or $60 per airplane, per inspection cycle.

The 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.

Regulatory Impact

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. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

99-19-28 Empresa Brasileira De Aeronautica S.A. (EMBRAER):

Amendment 39-11315. Docket 98-NM-261-AD.

Applicability: Model EMB-120RT and -120ER series airplanes,

equipped with BFGoodrich brake assemblies having part number (P/N)

2-1585 or 2-1479-1; certificated in any category.

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

modified, altered, or repaired in the area subject to the

requirements of this AD. For airplanes that have been modified,

altered, or repaired so that the performance of the requirements of

this AD is affected, the owner/operator must request approval for an

alternative method of compliance in accordance with paragraph (d) of

this AD. The request should include an assessment of the effect of

the modification, alteration, or repair on the unsafe condition

addressed by this AD; and, if the unsafe condition has not been

eliminated, the request should include specific proposed actions to

address it.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the brake assemblies of the main landing

gear (MLG) due to cracking or splitting of the stator disk, which

could result in loss of brake effectiveness and could cause the

airplane to leave the runway surface, accomplish the following:

(a) Within 400 flight hours after the effective date of this AD,

perform a detailed visual inspection for discrepancies (e.g.,

locking or hanging up, broken or damaged stators, and excessive

distortion of the wear plates) of the brake assemblies on the MLG,

in accordance with paragraph (a)(1) or (a)(2) of this AD, as

applicable. Repeat the inspections thereafter at intervals not to

exceed 400 flight hours.

(1) For airplanes equipped with BFGoodrich main brake assemblies

having P/N 2-1479-1: Inspect in accordance with BFGoodrich Service

Bulletin 2-1479-32-2, Revision 1, dated June 17, 1998.

(2) For airplanes equipped with BFGoodrich main brake assemblies

having P/N 2-1585: Inspect in accordance with BFGoodrich Service

Bulletin 2-1585-32-1, Revision 1, dated June 17, 1998.

Note 2: For the purposes of this AD, a detailed visual

inspection is defined as: ``An intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc., may be used. Surface cleaning

and elaborate access procedures may be required.''

(b) If any discrepancy is detected during any inspection

required by paragraph (a) of this AD, prior to further flight,

replace the brake assembly with a new or serviceable brake assembly,

in accordance with section 32-41-05 of EMBRAER EMB-120 Brasilia

Maintenance Manual, dated April 30, 1992. Repeat the inspections

required by paragraph (a) of this AD thereafter at intervals not to

exceed 400 flight hours.

(c) Within 10 days after accomplishing any inspection required

by this AD, if a discrepant brake assembly is detected, submit a

report of the inspection results to BFGoodrich, Aircraft Wheels and

Brakes, P.O. Box 340 Troy, Ohio, 45373. Information collection

requirements contained in this regulation have been approved by the

Office of Management and Budget (OMB) under the provisions of the

Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have

been assigned OMB Control Number 2120-0056.

Alternative Methods of Compliance

(d) 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 3: Information concerning the existence of approved

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

obtained from the Atlanta ACO.

Special Flight Permits

(e) 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.

Incorporation by Reference

(f) Except as provided by paragraph (b) of this AD, the

inspections and replacement shall be done in accordance with

BFGoodrich Service Bulletin 2-1479-32-2, Revision 1, dated June 17,

1998, and BFGoodrich Service Bulletin 2-1585-32-1, Revision 1, dated

June 17, 1998, as applicable. 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

BFGoodrich, Aircraft Wheels and Brakes, P.O. Box 340, Troy, Ohio

45373. 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, One Crown Center, 1895 Phoenix Boulevard, suite 450,

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

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

[[Page 49977]]

(g) This amendment becomes effective on October 20, 1999.

Issued in Renton, Washington, on September 2, 1999.

Dorenda D. Baker,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-23473 Filed 9-14-99; 8:45 am]

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