[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]



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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).

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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]
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