[Federal Register Volume 62, Number 26 (Friday, February 7, 1997)]
[Proposed Rules]
[Pages 5785-5787]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-3028]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-137-AD]
RIN 2120-AA64


Airworthiness Directives; Construcciones Aeronauticas, S.A. 
(CASA) Model CN-235 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 CASA Model CN-235 series 
airplanes. This proposal would require repetitive inspections of the 
torsion tubes and fittings of the elevator and rudder assemblies to 
detect stress corrosion cracking, and replacement of cracked parts. 
This proposed action also would require the accomplishment of a 
modification that would constitute terminating action for the 
repetitive inspections. This proposal is prompted by reports indicating 
that stress corrosion cracking in these parts has been found on some 
airplanes. The actions specified by the proposed AD are intended to 
prevent loss of control of the elevator and/or rudder, due to failure 
of the elevator and/or rudder assemblies as a result of stress 
corrosion cracking.

DATES: Comments must be received by March 20, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-137-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 Construcciones Aeronauticas, S.A., Getafe, Madrid, Spain. 
This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Greg Dunn, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2799; fax (206) 227-1149.

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 96-NM-137-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. 96-NM-137-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Direccion General de Aviacion (DGAC), which is the 
airworthiness authority for Spain, has notified the FAA that an unsafe 
condition may exist on certain CASA Model CN-235 series airplanes. The 
DGAC advises that it has received reports indicating that stress 
corrosion cracks were detected in the torsion tubes and fittings of the 
elevator and rudder assemblies on some of these airplanes. This 
condition, if not corrected, could result in failure of these 
assemblies and subsequent loss of control of the elevator and/or 
rudder.

Explanation of Relevant Service Information

    CASA has issued Service Bulletin SB-235-27-05, Revision 1, dated 
September 29, 1993 (for non-military airplanes), and Service Bulletin 
SB-235-27-05M, Revision 2, dated January 25, 1996 (for military 
airplanes). These service bulletins describe procedures for conducting 
repetitive visual inspections of the torsion tubes for the rudder and 
elevator to detect stress corrosion cracking, and replacement of 
discrepant tubes with tubes of a new design. Installation of the newly-
designed torsion tubes is intended to preclude stress corrosion 
cracking and eliminates the need for repetitive visual inspections.
    The DGAC classified Service Bulletin SB-235-27-05 (for non-military 
airplanes) as mandatory and issued Spanish airworthiness directive 06/
94, dated August 1994, in order to assure the continued airworthiness 
of these airplanes in Spain. The DGAC classified Service Bulletin SB-
235-27-05M (for military airplanes) as ``recommended.''

FAA's Conclusions

    This airplane model is manufactured in Spain 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 DGAC has kept the FAA informed 
of the situation described above. The FAA has examined the findings of 
the DGAC, 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.

[[Page 5786]]

Explanation of Requirements of Proposed Rule

    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 visual inspections of the torsion 
tubes and fittings of the rudder and elevator assemblies to detect 
stress corrosion cracking, and replacement of discrepant parts. This 
proposed AD also would require the eventual installation of newly-
designed torsion tubes assemblies on all airplanes, which, when 
accomplished, would constitute terminating action for the required 
inspections. The actions would be required to be accomplished in 
accordance with the applicable service bulletin described previously.

Differences Between Proposed AD and Parallel Spanish Action

    Operators should note that the Spanish DGAC has not mandated the 
accomplishment of the terminating modification; however, this AD 
proposes to require it.
    The FAA has determined that long term continued operational safety 
will be better assured by design changes to remove the source of the 
problem, rather than by repetitive inspections. Long term inspections 
may not be providing the degree of safety assurance necessary for the 
transport airplane fleet. This, coupled with a better understanding of 
the human factors associated with numerous continual inspections, has 
led the FAA to consider placing less emphasis on inspections and more 
emphasis on design improvements. The proposed modification requirement 
is in consonance with these considerations.

Cost Impact

    The FAA estimates that 1 CASA Model CN-235 series airplane of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 6 work hours per airplane to accomplish 
each proposed visual inspection, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the proposed 
inspections on the single affected U.S. operator is estimated to be 
$360 per inspection.
    It would take approximately 40 work hours to accomplish the 
proposed terminating modification, at an average labor rate of $60 per 
work hour. (The work hour figure does not include the time needed for 
preparation of the airplane or equipment: familiarization with the 
service bulletin; curing times for adhesive, sealant, paint, etc.; tool 
collection; or down time.) Required parts would cost approximately 
$8,900 per airplane. Based on these figures, the cost impact of the 
proposed modification on the single affected U.S. operators is 
estimated to be $9,140.
    The 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.

Regulatory Impact

    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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

CASA: Docket 96-NM-137-AD.

    Applicability: Model CN-235 airplanes as listed in CASA Service 
Bulletin SB-235-27-05, Revision 1, dated September 29, 1993 (non-
military airplanes), and CASA Service Bulletin SB-235-27-05M, 
Revision 2, dated January 25, 1996 (military airplanes); 
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 loss of control of the elevator and/or rudder, due to 
failure of the elevator and/or rudder assemblies as a result of 
stress corrosion cracking in the torsion tubes and fittings, 
accomplish the following:

    Note 2: Actions required by this AD that were accomplished 
previous to the effective date of this AD, and in accordance with 
earlier versions of the specified CASA service bulletins, are 
considered acceptable for compliance with the applicable 
requirements of this AD.

    (a) At the applicable time specified in either paragraph (a)(1) 
or (a)(2) of this AD, conduct a visual inspection of the torsion 
(torsion) tubes on the elevator and rudder assemblies to detect 
stress corrosion cracking, in accordance with CASA Service Bulletin 
SB-235-27-05, Revision 1, dated September 29, 1993 (for non-military 
airplanes) or CASA Service Bulletin SB-235-27-05M, Revision 2, dated 
January 25, 1996 (for military airplanes), as applicable.
    (1) For airplanes that have accumulated more than 600 total 
hours time-in-service, or more than 1,000 total landings, as of the 
effective date of this AD: Conduct the inspection required by 
paragraph (a) of this AD prior to the accumulation of 50 hours time-
in-service, or 100 landings, or within 3 months, after the effective 
date of this AD, whichever occurs first.
    (2) For all other airplanes: Conduct the inspection required by 
paragraph (a) of this AD prior to the accumulation of 600 total 
hours time-in-service, or 1,000 total landings, or within 6 months, 
after the effective date of this AD, whichever occurs first.
    (b) If no cracking is detected during the inspection required by 
paragraph (a) of this AD, repeat that inspection at intervals not to 
exceed 600 hours time-in-service, or 1,000 landings, or 6 months, 
whichever occurs first.
    (c) If any cracking is detected during the inspection required 
by paragraph (a) of this AD, prior to further flight, accomplish 
either paragraph (c)(1) or (c)(2) of this AD.
    (1) Replace cracked parts with a new parts of the original 
design, in accordance with the

[[Page 5787]]

service bulletin. After replacement, repeat the visual inspection 
required by paragraph (a) of this AD at intervals not to exceed 600 
hours time-in-service, or 1,000 landings, or 6 months, whichever 
occurs first. OR
    (2) Replace cracked parts with a newly-designed parts, in 
accordance with CASA Service Bulletin SB-235-27-05, Revision 1, 
dated September 29, 1993 (for non-military airplanes); or CASA 
Service Bulletin SB-235-27-05M, Revision 2, dated January 25,1996 
(for military airplanes); as applicable. This replacement 
constitutes terminating action for the repetitive visual inspections 
of that part required by paragraph (b) of this AD.
    (d) Within 2 years after the effective date of this AD, replace 
all original design parts comprising the torsion tube assemblies on 
the elevator and rudder assemblies with newly-designed parts, in 
accordance with CASA Service Bulletin SB-235-27-05, Revision 1, 
dated September 29, 1993 (for non-military airplanes); or CASA 
Service Bulletin SB-235-27-05M, Revision 2, dated January 25, 1996 
(for military airplanes); as applicable. This action constitutes 
terminating action for the inspection 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, Standardization Branch, ANM-113, 
FAA, Transport 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, 
Standardization Branch, ANM-113.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (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 January 31, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-3028 Filed 2-6-97; 8:45 am]
BILLING CODE 4910-13-U