[Federal Register Volume 61, Number 79 (Tuesday, April 23, 1996)]
[Proposed Rules]
[Pages 17853-17855]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-9934]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-192-AD]


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain EMBRAER Model EMB-120 
series airplanes. This proposal would 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. 
This proposal also would require the eventual replacement of certain 
brackets with new brackets, which would terminate the requirement for 
the inspections. This proposal is prompted by reports of cracks in the 
wing rib-to-skin support brackets in both the lower and upper skin of 
the wings. The actions specified by the proposed 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: Comments must be received by June 3, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-192-AD, 1601 Lind Avenue SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays. -
    The service information referenced in the proposed rule may be 
obtained from EMBRAER, Empresa Brasileira De Aeronautica S/A, Sao Jose 
dos Campos - SP, Brazil. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, 
Washington.

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:

Comments Invited -

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received. -
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket. -
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-NM-192-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs -

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 95-NM-192-AD, 1601 Lind Avenue SW., Renton, Washington 
98055-4056.

Discussion -

    The Departamento de AviaCao Civil (DAC), which is the airworthiness 
authority for Brazil, recently notified the FAA that an unsafe 
condition may exist on certain EMBRAER Model EMB-120 series airplanes. 
The DAC advises that it has received reports of cracks in the rib-to-
skin fitting brackets (shear clips) both in the lower and upper skin of 
the wings on Model EMB-120 series airplanes. The development of 
cracking of the shear clips can occur in the wing skin riveting line 
and can cause the complete failure of the ledge of the shear clips, 
resulting in separation of the skin from the shear clip on the affected 
area. Although there are several shear clips per rib, the simultaneous 
occurrence of cracking in several shear clips will affect the wing's 
structural integrity. The cause of the cracking is attributed to 
fatigue. Cracking of those support brackets can cause rivets in the 
wing skin to loosen and, consequently, permit fuel to leak into the 
wing through the rivet holes. Propagation of such cracking, if not 
corrected, could reduce the structural integrity of the wing and permit 
fuel leakage into the wing.
    EMBRAER has issued Service Bulletin (SB) 120-57-0031, dated July 6, 
1995, which describes procedures for repetitive internal visual 
inspections to detect cracks in the wing rib-to-skin support brackets 
(shear clips), and replacement of cracked brackets with new or 
serviceable parts. The service

[[Page 17854]]

bulletin also describes procedures for a terminating action for the 
repetitive inspections. That action involves replacement of all wing 
rib-to-skin support brackets of ribs 15 and 16 with brackets having a 
new part number; inspection to detect cracking of the wing skin support 
brackets of ribs 18, 19, 20, 21, and 22; and replacement of cracked 
brackets with new or serviceable brackets having the same part number. 
The DAC classified this service bulletin as mandatory and issued 
Brazilian airworthiness directive (DA) 95-05-01 R1, dated August 25, 
1995, in order to assure the continued airworthiness of these airplanes 
in Brazil . -
    This airplane model is manufactured in Brazil and is type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the DAC has kept the FAA informed of 
the situation described above. The FAA has examined the findings of the 
DAC, reviewed all available information, and determined that AD action 
is necessary for products of this type design that are certificated for 
operation in the United States. -
    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, the 
proposed AD would require repetitive internal visual inspections to 
detect cracks in the wing rib-to-skin support brackets (shear clips). 
If cracks are found that are within certain limits (in length), this 
proposed AD would permit flights to continue, but the inspections would 
be required to be conducted more often. If cracks are found that are 
outside certain limits, the bracket would be required to be replaced 
prior to further flight, and additional inspection of other adjacent 
support brackets would be required to be accomplished. This proposed AD 
also would require that all wing rib to skin support brackets of ribs 
15 and 16 be replaced with new brackets. This replacement would 
constitute terminating action for the required inspections. The actions 
would be required to be accomplished in accordance with the service 
bulletin described previously. -
    Operators should note that, in addition to the inspection for 
cracking of the wing skin brackets recommended in the referenced 
Embraer service bulletin, this proposed AD would require that a 
repetitive visual inspection of the wing skin for fuel leakage be 
accomplished within every 50 flight hours until the terminating action 
has been accomplished. The FAA finds that inspections for such fuel 
leakage [fuel leakage as defined and classified in the Airplane 
Maintenance Manual (AMM)] are necessary to provide an indication of the 
urgency of need to inspect for cracking of the wing skin brackets. -
    The FAA estimates that 169 airplanes of U.S. registry would be 
affected by this proposed AD. -
    It would take approximately 6 work hours per airplane to accomplish 
the proposed visual inspection for cracking, at an average labor rate 
of $60 per work hour. Based on these figures, the cost impact of this 
proposed inspection action on U.S. operators is estimated to be 
$60,840, or $360 per airplane, per inspection cycle. -
    It would take approximately 56 work hours to accomplish the 
proposed replacement of support brackets, at an average labor rate of 
$60 per work hour. Required parts would cost approximately $1,000 per 
airplane. Based on these figures, the cost impact of the proposed 
replacement 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 
proposed AD, and that no operator would accomplish those actions in the 
future if this proposal were not adopted. However, the FAA has been 
advised that the terminating modification already has been installed on 
a number of airlines that are subject to this AD. Therefore, the future 
economic cost impact of this rule on U.S. operators is expected to be 
less than the cost impact figures indicated above.
    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that 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) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

EMBRAER: 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 have been accomplished.
    (b) For airplanes on which fuel leakage is detected during any 
inspection required by

[[Page 17855]]

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 of EMBRAER Service Bulletin 120-57-0031, 
dated July 6, 1995, at the time specified in paragraph (b)(1), 
(b)(2), or (b)(3) of this AD, as applicable.
    (1) If no cracking is detected: Repeat the internal visual 
inspection required by paragraph (b) of this AD thereafter at 
intervals not to exceed 1,200 flight cycles until the requirements 
of paragraph (d) of this AD have been 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 the internal visual 
inspection required by paragraph (b) of this AD thereafter at 
intervals not to exceed 400 flight cycles, until the requirements of 
paragraph (d) of this AD have been accomplished. -
    (3) If any cracking is detected other than that specified in 
paragraph (b)(2) of this AD: Prior to further flight, replace any 
support bracket that is cracked beyond the limits specified in 
paragraph (b)(2) of this AD with a new bracket, in accordance with 
the Accomplishment Instructions of the service bulletin. Following 
any replacement, 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 service bulletin. -
    (i) If no cracking is found, repeat the internal visual 
inspection required by paragraph (b) of this AD 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, prior to further flight, replace 
any cracked bracket with a serviceable part, in accordance with the 
service bulletin. -
    (c) For airplanes on which no wing fuel leakage is detected 
during any inspection required by paragraph (a) 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 of EMBRAER Service Bulletin 120-57-0031, dated July 6, 
1995, at the time specified in paragraph (c)(1), (c)(2), (c)(3), or 
(c)(4) of this AD, as applicable. Thereafter, repeat this inspection 
as intervals not to exceed 1,200 flight cycles until the 
requirements of paragraph (d) of this AD are accomplished. -
    (1) 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. -
    (2) 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. -
    (3) 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. -
    (4) 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. -
    (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 brackets in accordance with EMBRAER Service Bulletin 120-57-
0031, dated July 6, 1995. Prior to further flight following the 
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 cracked brackets 
with serviceable brackets in accordance with the service bulletin. 
Accomplishment of these requirements 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.

    Issued in Renton, Washington, on April 17, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-9934 Filed 4-22-96; 8:45 am]
BILLING CODE 4910-13-U