[Federal Register Volume 60, Number 51 (Thursday, March 16, 1995)]
[Proposed Rules]
[Pages 14233-14235]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-6321]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 95-NM-15-AD]
Airworthiness Directives; Boeing Model B-17E, F, and G Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to all Boeing Model B-17E, F, and G
airplanes. This proposal would require inspections to detect cracking
and corrosion of the wing spar chords, bolts and bolt holes of the spar
chords, and wing terminals; and correction of any discrepancy found
during these inspections. This proposal is prompted by reports of
cracking and corrosion of the wing spar. The actions specified by the
proposed AD are intended to prevent reduced structural integrity of the
wing of the airplane due to the problems associated with corrosion and
cracking of the wing spar.
DATES: Comments must be received by April 18, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 95-NM-15-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.
FOR FURTHER INFORMATION CONTACT: Philip Forde, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2771; fax (206) 227-1181.
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-15-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-15-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
Recently, during routine inspections of several Boeing Model B-17
series airplanes, extensive corrosion and numerous cracks were found on
the tubular spar chords of the inner wing. These tubular spar chords
mate with the circular inner wing attach fitting inserts that are held
together by close tolerance bolts. (There are four such joints on each
wing of the airplane.) Investigation revealed that moisture trapped in
the inner wing spars caused some of the bolts in the joint assemblies
to seize and corrode. The FAA has determined that the wing spar
assembly is susceptible to moisture accumulation, which may result in
internal corrosion and subsequent cracking in this area. Since this
area is subject to maximum bending and stress loads, cracking in this
area is particularly critical.
This condition, if not corrected and detected in a timely manner,
could result in reduced structural integrity of the wing of the
airplane.
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would require a dye penetrant inspection to
[[Page 14234]] detect cracking and corrosion of the aluminum wing spar
chords; an eddy current inspection to detect cracking and corrosion of
the bolts and bolt holes of the spar chords; and correction of any
discrepancies found. The FAA has determined that the spar-to-wing
terminal joint must be separated, including removing the wing of the
airplane from the fuselage, to adequately detect cracking and corrosion
of the bolts, inner wing fittings, and tubular spar chords. This action
would also require visual and eddy current inspections to detect
cracking and corrosion of the wing terminals and spar chords; and
repair of any cracking or corrosion found.
There are approximately 12 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 10 airplanes of U.S. registry
would be affected by this proposed AD, that it would take approximately
1,500 work hours per airplane to accomplish the proposed actions, and
that the average labor rate is $60 per work hour. Based on these
figures, the total cost impact of the proposed AD on U.S. operators is
estimated to be $900,000, or $90,000 per airplane.
The total cost impact figure discussed above is based on
assumptions that no operator has yet accomplished any of the proposed
requirements of this AD action, and that no operator would accomplish
those actions in the future if this AD were not adopted.
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 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 95-NM-15-AD.
Applicability: All Model B-17E, F, and G airplanes, certificated
in any category.
Note 1: For airplanes on which the terminal fitting-to-spar
chord joint was separated prior to the effective date of this AD,
and inspection(s) of and/or repair(s) to the wing terminals-to-spar
chords were accomplished prior to the effective date of this AD:
Applications for an alternative method of compliance to the
requirements of paragraphs (a) and (b) of this AD should be
submitted to the FAA, in accordance with the provisions of paragraph
(d) of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent reduced structural integrity of the wing of the
airplane, accomplish the following:
(a) Within 90 days after the effective date of this AD,
accomplish the requirements of paragraphs (a)(1), (a)(2), and (a)(3)
of this AD.
(1) Perform a dye penetrant inspection to detect cracking of
each inboard end of the eight aluminum wing spar chords, in
accordance with MIL-STD-6866. If any cracking is detected that is
beyond the limits specified in the acceptance/rejection criteria
contained in sensitivity level Group IV, MIL-I-25135, prior to
further flight, repair in accordance with a method approved by the
Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport
Airplane Directorate.
Note 2: The part number (P/N) for the upper wing spar chords is
3-14231-0, and the P/N for the lower wing spar chords is 3-14231-1.
(2) Perform a high frequency eddy current inspection to detect
cracking of the bolt holes of the spar chords, in accordance with a
method approved by the Manager, Seattle Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. The inboard-most
bolt on each of the eight wing terminal fitting-to-wing spar chord
tube joints must be removed to perform this inspection.
Note 3: The following are the P/N's for the terminal fitting-to-
spar chord joint assemblies:
------------------------------------------------------------------------
Assembly
Assemblies- part No.
------------------------------------------------------------------------
Left Upper Front Spar Joint Assembly-..................... 75-4781-0
Right Upper Front Spar Joint Assembly-.................... 75-4781-1
Left Lower Front Spar Joint Assembly-..................... 65-4782-512
Right Lower Front Spar Joint Assembly-.................... 65-4782-513
Left Upper Rear Spar Joint Assembly-...................... 75-4783-0
Right Upper Rear Spar Joint Assembly-..................... 75-4783-1
Left Lower Rear Spar Joint Assembly-...................... 75-4784-0
Right Lower Rear Spar Joint Assembly-..................... 75-4784-1
------------------------------------------------------------------------
Note 4: The following are the P/N's for the bolts for the spar
chords:
------------------------------------------------------------------------
Bolts for Bolt part No.
------------------------------------------------------------------------
Upper and Lower Front Spar Chords-.................... NAS56A36
Upper Rear Spar Chord-................................ NAS56A34
Lower Rear Spar Chord-................................ NAS56A40-5
------------------------------------------------------------------------
(3) Perform a visual inspection to detect corrosion of the bolts
and replace any corroded bolt with a new bolt having a P/N in the
NAS 6606 series in accordance with Army Technical Order Number 01-
20EF-2. Prior to further flight, accomplish the requirements of
paragraphs (a)(3)(i), (a)(3)(ii), and (a)(3)(iii) of this AD in
accordance with Army Technical Order Number 01-20EF-2.
Note 4: The following are the P/N's for the replacement bolts
for the spar chords:
------------------------------------------------------------------------
Replacement bolt
Replacement bolts for- part No.
------------------------------------------------------------------------
Upper and Lower Front Spar-........................... NAS 6606-51
Upper Rear Spar-...................................... NAS 6606-47
Lower Rear Spar-...................................... NAS 6606-56
------------------------------------------------------------------------
(i) Install a washer having P/N MS 20002C6 under the head of the
bolt, a self-locking nut having P/N NAS 1804-6, and a washer having
P/N MS 200026 under the nut, for each replacement bolt.
(ii) Torque any replacement bolt to 95-105 inch-pounds.
(iii) Oversize replacement bolts by 1/16 inch, as necessary.
(b) Within 18 months after the effective date of this AD,
accomplish the requirements of either paragraph (b)(1) or (b)(2) of
this AD.
(1) Perform visual and high frequency eddy current inspections,
that include separating all eight wing terminal-to-spar chord
joints, to detect cracking and corrosion of the wing terminals and
spar chords, in accordance with a method approved by the Manager,
Seattle ACO. Or
(2) Perform an equivalent inspection(s) to that required by
paragraph (b)(1) of this AD, [[Page 14235]] that may not include
separating the terminal fitting from the spar chord to detect
cracking and corrosion of all eight wing terminal-to-spar chord
joints, in accordance with a method approved by the Manager, Seattle
ACO. To be considered acceptable, the equivalent inspection(s) must
include, at a minimum, the criteria specified in paragraphs
(b)(2)(i), (b)(2)(ii), and (b)(2)(iii) of this AD.
(i) The inspection must include removal of all 64 bolts that
join the eight wing terminals to the eight spar chords; and
(ii) The inspection must adequately detect cracking of the spar
chord, and corrosion between the terminal fitting and the spar
chord; and
(iii) The inspection must include a visual inspection to detect
corrosion of the attachment bolts; and a high frequency eddy
current, and boroscope inspection at 10 power magnification, of the
bolt holes common to the spar chord-to-wing terminal interface.
(c) If any cracking and/or corrosion is detected during any of
the inspections required by paragraphs (a) and (b) of this AD, prior
to further flight, repair in accordance with a method approved by
the Manager, Seattle ACO.
(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, Seattle ACO. Operators shall submit
their requests through an appropriate FAA Principal Maintenance
Inspector, who may add comments and then send it to the Manager,
Seattle ACO.
Note 5: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(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.
Issued in Renton, Washington, on March 9, 1995.
Neil D. Schalekamp,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-6321 Filed 3-15-95; 8:45 am]
BILLING CODE 4910-13-U
