[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
