[Federal Register Volume 62, Number 17 (Monday, January 27, 1997)]
[Rules and Regulations]
[Pages 3784-3786]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-1826]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-192-AD; Amendment 39-9906; AD 97-02-21]
RIN 2120-AA64


Airworthiness Directives; Empresa Brasileira de Aeronautica, S.A. 
(EMBRAER) Model EMB-120 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-120 series airplanes, that 
requires repetitive inspections to detect cracks in the wing rib-to-
skin support brackets (shear clips), and replacement of cracked 
brackets with new or serviceable brackets. This amendment also requires 
the eventual replacement of certain brackets with new brackets, which 
terminates the requirement for the inspections. This amendment is 
prompted by reports of cracks in certain wing rib-to-skin support 
brackets in both the lower and upper skin of the wings. The actions 
specified by this AD are intended to prevent cracking of those support 
brackets, which can subsequently lead to the loosening of the rivets in 
the wing skin, leakage of fuel through the rivet holes, and, 
ultimately, the reduction of the structural integrity of the wing.

DATES: Effective March 3, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 3, 1997.

ADDRESSES: The service information referenced in this AD may be 
obtained from Empresa Brasileira de Aeronautica, S.A. (EMBRAER), Sao 
Jose dos Campos--SP, Brazil. 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, 
Atlanta Aircraft Certification Office, Small Airplane Directorate, 
Campus Building, 1701 Columbia Avenue, Suite 2-160, College Park, 
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 and Propulsion Branch, ACE-117A, FAA, Atlanta Aircraft 
Certification Office, Small Airplane Directorate, Campus Building, 1701 
Columbia Avenue, Suite 2-160, College Park, Georgia 30337-2748; 
telephone (404) 305-7358; fax (404) 305-7348.

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-120 
series airplanes was published in the Federal Register on April 24, 
1996 (61 FR 17853). That action proposed to require repetitive 
inspections to detect cracks in the wing rib-to-skin support brackets 
(shear clips), and replacement of cracked brackets with new or 
serviceable brackets. That action also proposed to require the eventual 
replacement of certain brackets with new brackets, which would 
terminate the requirement for the inspections.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the single comment received.

Request to Delete Inspection Requirement

    The only commenter, a U.S. operator, requests that the proposal be 
revised to delete the requirement to conduct repetitive inspections of 
the brackets. This commenter states that the subject area already is 
inspected by its flight crews on preflight inspections, and by its 
mechanics on daily inspections and line checks. The commenter considers 
that the need for the inspection requirement, and the extra paperwork 
that would be involved, cannot be justified by any data. This 
commenter, who operates 63 of the affected airplanes, indicates that it 
has analyzed the last 12 months of data on fuel leaks in its fleet; the 
data indicate that there have been 43 fuel leaks associated with 
leaking rivets, but there were no broken or cracked brackets found.
    The FAA does not concur with the commenter's request. While this 
commenter specifically may not have found cracked brackets, there have 
been several cases reported by other operators in which fuel leaks 
caused by broken or cracked brackets were discovered on in-service 
airplanes. The FAA finds that the proposed inspection requirement will 
be effective in finding and addressing fuel leakage, and any associated 
cracking of a support bracket, well before more serious problems 
associated with these conditions could occur. The FAA also points out 
that operators may discontinue the inspections once the newly designed 
brackets are installed and follow-on actions are accomplished.

Request to Clarify ``New'' and ``Old'' Bracket Design

    This same commenter requests clarification regarding the types of 
replacement brackets that are required to be installed. Specifically, 
the commenter questions whether it would be acceptable to install ``old 
style'' brackets as replacement parts in cases where no ``new style'' 
brackets are available.
    The FAA concurs that clarification is necessary. If cracking is 
found in the brackets at ribs 15, 16, or 18, and the extent of the 
cracking necessitates replacement, operators may install either another 
new or serviceable ``old style'' bracket having the same part number; 
or a ``new style'' bracket, having a part number that is specified in 
paragraph 3.1. of EMBRAER Service Bulletin 120-57-0031. However, 
terminating action consists of replacing

[[Page 3785]]

those brackets at ribs 15, 16, and 18 with only the ``new style'' 
brackets.
    On the other hand, if cracking is found in brackets at other rib 
locations (namely, ribs 19, 20, 21, and 22), only the ``old style'' 
brackets (same part number) are required to be installed as replacement 
parts at those locations.
    The final rule has been revised to clarify these points.

Revision of Format of Final Rule

    The format of the final rule has been revised somewhat to follow 
more closely the format of procedures as they are presented in the 
referenced EMBRAER Service Bulletin 120-57-0031, dated July 6, 1995. 
The FAA considers that this reformatting will help to clarify the 
required procedures for affected operators.

Conclusion

    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 changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    The FAA estimates that 169 airplanes of U.S. registry will be 
affected by this AD.
    It will take approximately 6 work hours per airplane to accomplish 
the required visual inspection for cracking, at an average labor rate 
of $60 per work hour. Based on these figures, the cost impact of the 
inspection action on U.S. operators is estimated to be $60,840, or $360 
per airplane, per inspection cycle.
    It will take approximately 56 work hours to accomplish the required 
replacement of support brackets, at an average labor rate of $60 per 
work hour. Required parts will cost approximately $1,000 per airplane. 
Based on these figures, the cost impact of the replacement action on 
U.S. operators is estimated to be $736,840, or $4,360 per airplane.
    The cost impact figures discussed above are 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:

97-02-21  Embraer: Amendment 39-9906. Docket 95-NM-192-AD.
    Applicability: Model EMB-120 airplanes, serial numbers 120001, 
120003, 120004, and 120006 through 120304 inclusive; certificated in 
any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (e) 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 reduced wing structural integrity and fuel leakage of 
the wing due to cracking of wing rib-to-skin support brackets, 
accomplish the following:

    Note 2: The term ``fuel leakage'' and ``stain,'' as used 
throughout this AD, are used as they are defined and classified in 
Chapter 28, Fuel, of the Airplane Maintenance Manual (AMM).

    (a) Within 10 days after the effective date of this AD: Perform 
a visual inspection of the wing skin along rib lines 15 and 16 to 
detect any fuel leakage other than a stain. Thereafter, repeat this 
inspection every 50 flight hours until the requirements of paragraph 
(d) of this AD are accomplished.
    (b) As a result of the inspection required by paragraph (a) of 
this AD, accomplish either paragraph (b)(1) or (b)(2), as 
applicable:
    (1) If fuel leakage is detected during any inspection required 
by paragraph (a) of this AD: Within 50 flights after detection of 
fuel leakage, perform an internal visual inspection to detect 
cracking of the wing rib-to-skin support brackets (shear clips) that 
connect the lower and upper wing skins to ribs 15 and 16, in 
accordance with the Accomplishment Instructions, PART I, of EMBRAER 
Service Bulletin 120-57-0031, dated July 6, 1995.
    (2) If no fuel leakage is detected during any inspection 
required by paragraph (a) of this AD: At the applicable time 
specified in paragraph (b)(2)(i) through (b)(2)(iv) of this AD, 
perform an internal visual inspection to detect cracking of the wing 
rib-to-skin support brackets (shear clips) that connect the lower 
and upper wing skins to ribs 15 and 16, in accordance with the 
Accomplishment Instructions, PART I, of EMBRAER Service Bulletin 
120-57-0031, dated July 6, 1995.
    (i) For airplanes that have accumulated less than 4,000 total 
flight cycles as of the effective date of this AD: Inspect prior to 
the accumulation of 5,200 total flight cycles, or within 1,200 
flight cycles after the effective date of this AD, whichever occurs 
later.
    (ii) For airplanes that have accumulated 4,000 or more total 
flight cycles, but less than 8,000 total flight cycles as of the 
effective date of this AD: Inspect within 1,200 flight cycles after 
the effective date of this AD.
    (iii) For airplanes that have accumulated 8,000 or more total 
flight cycles, but less than 12,000 total flight cycles as of the 
effective date of this AD: Inspect within 800 flight cycles after 
the effective date of this AD.
    (iv) For airplanes that have accumulated 12,000 or more total 
flight cycles as of the effective date of this AD: Inspect within 
400 flight cycles after the effective date of this AD.
    (c) As a result of the internal visual inspection to detect 
cracking of the wing rib-to-skin support brackets (shear clips) that 
connect the lower and upper wing skins to ribs 15 and 16, as 
required by paragraph (b) of this AD, accomplish the actions 
specified in paragraph (c)(1), (c)(2), or (c)(3), as applicable:

[[Page 3786]]

    (1) If no cracking is detected: Repeat that internal visual 
inspection thereafter at intervals not to exceed 1,200 flight cycles 
until the requirements of paragraph (d) of this AD are accomplished.
    (2) If any cracking is detected in only one wing skin support 
bracket, and that cracking is more than half the length of the 
bracket; and if any cracking also is detected in up to two 
additional wing skin support brackets and that cracking is less than 
half the length of the bracket: Repeat that internal visual 
inspection thereafter at intervals not to exceed 400 flight cycles, 
until the requirements of paragraph (d) of this AD are accomplished.
    (3) If any cracking is detected other than that specified in 
paragraph (c)(2) of this AD: Prior to further flight, replace any 
support bracket that is cracked beyond the limits specified in 
paragraph (c)(2) of this AD either with a new or serviceable bracket 
having the same part number, or with a new style bracket having a 
part number specified in paragraph 3.1. of EMBRAER Service Bulletin 
120-57-0031, dated July 6, 1995.
    Following replacement and prior to further flight, perform an 
additional internal visual inspection to detect cracking of the 
support brackets that connect the wing skins to ribs 18, 19, 20, 21, 
and 22 in accordance with the EMBRAER service bulletin.
    (i) If no cracking is found in the support brackets that connect 
the wing skins at ribs 18, 19, 20, 21, or 22: Repeat that internal 
visual inspection thereafter at intervals not to exceed 1,200 flight 
cycles until the requirements of paragraph (d) of this AD are 
accomplished.
    (ii) If any cracking is found in the support brackets that 
connect the wing skins at ribs 18, 19, 20, 21, or 22: Prior to 
further flight, replace the cracked bracket with a new or 
serviceable bracket having the same part number; rib 18 may also be 
replaced with a ``new style'' bracket having a part number specified 
in paragraph 3.1. of the EMBRAER service bulletin.
    (d) Within 2 years after the effective date of this AD: Replace 
all wing rib-to-skin support brackets of ribs 15, 16, and 18 with 
``new style'' brackets having a part number specified in paragraph 
3.1. of EMBRAER Service Bulletin 120-57-0031, dated July 6, 1995. 
Replacement procedures shall be accomplished in accordance with the 
Accomplishment Instructions, PART II, of that service bulletin. 
Prior to further flight following that replacement, perform a visual 
inspection to detect cracking of the wing skin support brackets of 
ribs 19, 20, 21, and 22. If any cracking is found, prior to further 
flight, replace the cracked bracket with a new or serviceable 
bracket having the same part number, in accordance with the EMBRAER 
service bulletin. Accomplishment of these actions constitutes 
terminating action for the requirements of this AD.
    (e) 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.
    (f) 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.
    (g) The actions shall be done in accordance with EMBRAER Service 
Bulletin 120-57-0031, dated July 6, 1995. 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 Empresa Brasileira de Aeronautica, S.A. (EMBRAER), Sao 
Jose dos Campos--SP, Brazil. Copies may be inspected at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Atlanta Aircraft Certification Office, 
Small Airplane Directorate, Campus Building, 1701 Columbia Avenue, 
Suite 2-160, College Park, Georgia; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (h) This amendment becomes effective on March 3, 1997.

    Issued in Renton, Washington, on January 17, 1997.
S. R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-1826 Filed 1-24-97; 8:45 am]
BILLING CODE 4910-13-U