[Federal Register Volume 59, Number 49 (Monday, March 14, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-5850]


[[Page Unknown]]

[Federal Register: March 14, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-76-AD]

 

Airworthiness Directives; Fokker Model F-27 Mark 100, 200, 300, 
400, 500, 600, 700, and 800 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 Fokker Model F-27 series 
airplanes. This proposal would require the implementation of a 
corrosion prevention and control program either by accomplishing 
specific tasks or by revising the maintenance inspection program to 
include such a program. This proposal is prompted by reports of 
incidents involving corrosion and fatigue cracking in transport 
category airplanes that are approaching or have exceeded their economic 
design goal; these incidents have jeopardized the airworthiness of the 
affected airplanes. The actions specified by the proposed AD are 
intended to prevent degradation of the structural capabilities of the 
airplane due to the problems associated with corrosion.

DATES: Comments must be received by May 9, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 93-NM-76-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9 a.m. and 3 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Fokker Aircraft USA, Inc., 1199 North Fairfax Street, 
Alexandria, Virginia 22314. This information may be examined at the 
FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Mark Quam, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2145; fax (206) 227-1320.

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 93-NM-76-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. 93-NM-76-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    In April 1988, a high-cycle transport category airplane 
(specifically, a Boeing Model 737) was involved in an accident in which 
the airplane suffered major structural damage during flight. 
Investigation of this accident revealed that the airplane had numerous 
fatigue cracks and a great deal of corrosion. Subsequent inspections 
conducted by the operator on other high-cycle transport category 
airplanes in its fleet revealed that other airplanes had extensive 
fatigue cracking and corrosion.
    Prompted by the data gained from this accident, the FAA sponsored a 
conference on aging airplanes in June 1988, which was attended by 
representatives from the aviation industry and airworthiness 
authorities from around the world. It became obvious that, because of 
the tremendous increase in air travel, the relatively slow pace of new 
airplane production, and the apparent economic feasibility of operating 
older technology airplanes rather than retiring them, increased 
attention needed to be focused on the aging airplane fleet and 
maintaining its continued operational safety.
    The Air Transport Association (ATA) of America and the Aerospace 
Industries Association (AIA) of America agreed to undertake the task of 
identifying and implementing procedures to ensure the continued 
structural airworthiness of aging transport category airplanes. An 
Airworthiness Assurance Task Force (AATF) was established in August 
1988, with members representing aircraft manufacturers, operators, 
regulatory authorities, and other aviation industry representatives 
worldwide. The objective of the AATF was to sponsor ``Working Groups'' 
to:
    1. Select service bulletins, applicable to each airplane model in 
the transport fleet, to be recommended for mandatory modification of 
aging airplanes;
    2. Develop corrosion-directed inspections and prevention programs;
    3. Review the adequacy of each operator's structural maintenance 
program;
    4. Review and update the Supplemental Inspection Documents (SID); 
and
    5. Assess repair quality.
    The working group assigned to review the Fokker Model F-27 series 
airplanes has completed its work on Item (2) and has developed a 
baseline program for controlling corrosion problems that may jeopardize 
the continued airworthiness of the Model F-27 fleet. The program is 
contained in Fokker Document SE-291, ``F-27 Corrosion Control 
Program,'' with revisions through October 1, 1993. (Hereafter, this 
publication is referred to as ``the Document.'') The 
Rijksluchtvaartdienst (RLD), which is the airworthiness authority for 
the Netherlands, classified this Document as mandatory and issued 
Netherlands Airworthiness Directive (BLA) 91-113, Issue 2, dated June 
26, 1992, in order to assure the continued airworthiness of these 
airplanes in The Netherlands.
    Section 2.1 of the Document defines three levels of corrosion: 
Level l corrosion is that which does not exceed certain limits; Level 2 
corrosion is that which exceeds those limits; and Level 3 corrosion is 
significant corrosion which is potentially an urgent airworthiness 
concern.
    Sections 2.2 and 2.3 of the Document provide general guidelines to 
develop a corrosion prevention and control program. These guidelines 
address such things as a baseline program, implementation ages, access 
for inspection, repetitive inspection intervals, operating environment, 
newly-acquired airplanes, general cleanliness of the airplane, and the 
fact that sampling is unreliable in effectively controlling corrosion.
    Section 2.4 of the Document sets forth the general implementation 
schedule for the corrosion inspection/control program. As described in 
that section, each ``aircraft zone'' is assigned an ``Initial 
Inspection Time'' and a ``Repeat Inspection Time.'' The program is 
applicable to each aircraft zone on all Model F-27 series airplanes 
whose age has reached or exceeded the Initial Inspection Time for that 
zone. For airplanes that have not reached or exceeded the Initial 
Inspection Time of the specific aircraft zone, a particular inspection 
task has to be performed before the airplane has reached the Initial 
Inspection Time for the specific aircraft zone, or before the Repeat 
Inspection Time of the task is exceeded (a maximum of 6 years), 
whichever occurs later. For airplanes that have already reached or 
exceeded the Initial Inspection Time of the specific aircraft zone, a 
particular inspection has to be performed before the Repeat Inspection 
Time of the task is exceeded or within 6 years, whichever occurs first.
    Section 2.4 of the Document also identifies the specific aircraft 
zones that are subject to the program, and describes the ``basic task'' 
to be accomplished in each defined aircraft zone as part of the 
baseline program, along with the initial inspection time and repeat 
inspection time for each area, and other information necessary to carry 
out the program for each area. The Document defines a ``basic task'' as 
including not only the pertinent visual inspections of all primary and 
secondary structures, but any necessary repairs, application of 
sealants or corrosion inhibitors, and other follow-on procedures, as 
well. A basic task may also include detailed visual and non-destructive 
inspections (NDI); where NDI's are employed, adequate standards and 
procedures must be developed and properly recorded for the area 
inspected.
    Section 2.5 establishes the procedures for reporting the results of 
the inspections conducted under the corrosion prevention and control 
program.
    Section 2.6 provides for periodic review and update of the data 
contained in the Document.
    This airplane model is manufactured in the Netherlands and is type 
certificated for operation in the United States under the provisions of 
Section 21.29 of the Federal Aviation Regulations and the applicable 
bilateral airworthiness agreement. Pursuant to this bilateral 
airworthiness agreement, the RLD has kept the FAA informed of the 
situation described above. The FAA has examined the findings of the 
RLD, 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 corrosion is likely to exist or develop on airplanes of this 
type design, an AD is proposed which would require adoption of a 
corrosion prevention and control program that is equivalent to or 
better than the program specified in the Document previously described. 
Operators would be permitted to accomplish this either by performing 
the specific basic tasks described in the Document (the ``task-by-task 
method''), or by revising their FAA-approved maintenance program to 
include such a program.
    Paragraph (a) of the proposal sets forth the proposed compliance 
times for the initial basic task of each affected aircraft zone. These 
compliance times are measured from a date one year after the effective 
date of the final rule. (The proposed compliance times are consistent 
with those of other similar AD's that the FAA has issued on this 
subject.) Generally, operators would be required to complete the 
initial basic task before reaching the ``Initial Inspection Time'' plus 
one ``Repeat Inspection Time'' interval for the aircraft zone, as 
detailed in the Document. The basic task would be required to be 
repeated at a time interval not to exceed the ``Repeat Inspection 
Time'' interval for that area, as detailed in the Document.
    Paragraph (a) includes paragraph (a)(1)(iii), which states that, 
for each area that exceeds the initial inspection time for that area, 
operators must accomplish the initial basic task at a minimum rate of 
one such area every two years, beginning one year after the effective 
date of the final rule. The FAA recognizes that this may cause a 
hardship on some small operators; in those circumstances, the FAA 
anticipates evaluating requests for adjustment to the implementation 
rate on a case-by-case basis under the provisions of paragraph (h) of 
the proposed rule. (A note to this effect is included in the proposal.)
    Operators should note that the proposal does not contain a 
paragraph specifically to address repair actions. The FAA considers 
that any repairs would be carried out necessarily as a part of each 
basic task, as it is defined in the Document. As discussed previously, 
a ``basic task'' is defined in the Document as including not only the 
pertinent inspection, but any necessary repairs, application of 
corrosion inhibitors, and other follow- on procedures, as well. 
Paragraph (a) contains a note to reference the portion of the Document 
that defines a basic task, and to emphasize the importance of these 
corrective actions.
    Paragraph (b) of the proposal provides for an optional method of 
complying with the rule. In lieu of performing the task-by-task 
requirements proposed in paragraph (a), operators may revise their FAA-
approved maintenance/inspection programs to include the corrosion 
prevention and control program defined in the Document or an equivalent 
program approved by the FAA.
    Paragraph (b) also would require that, subsequent to the 
accomplishment of the initial basic task, any extensions of Repeat 
Inspection Time intervals specified in the Document must be approved by 
the FAA.
    Any operator electing to comply with proposed paragraph (b) would 
be permitted to use an alternative recordkeeping method to that 
otherwise required by Federal Aviation Regulations (FAR) section 91.417 
or section 121.380, provided it is approved by the FAA and is included 
in a revision to the FAA-approved maintenance/inspection program. In 
response to questions raised previously concerning recordkeeping and 
record retention requirements as they relate to the programmatic 
approach proposed in this AD action and other similar proposals that 
have been issued applicable to other airplane models, the FAA offers 
the following:
    Sections 91.417(a)(2)(v) and 121.380(a)(2)(v) of the FAR require 
that a record be made of the current status of applicable AD's. With 
regard to proposed paragraph (b), such a record would be required to be 
made when the maintenance/inspection program is revised to incorporate 
the program specified in the Document; at that time, paragraph (b) of 
the AD would be fully complied with. Regarding paragraphs (d) through 
(g) of this proposal, those paragraphs would impose separate 
requirements; therefore, except as discussed below, separate entries 
would have to be made to reflect compliance with each of those 
paragraphs.
    Section 121.380(a)(2)(iv) of the FAR concerns recording ``the 
identification of the current inspection status of the aircraft.'' 
Section 91.417(a)(2)(iv) contains a similar requirement. Because 
proposed paragraph (b) would require operators to revise their 
maintenance/inspection program to include the program specified in the 
Document, each operator's program would be required to identify each 
inspection (e.g., ``C'' check) at which each basic task specified in 
the Document will be performed on each airplane. By recording the 
current inspection status of each airplane, and by maintaining a cross-
reference system between these records and the maintenance/inspection 
program revision, it will be possible to determine the current status 
of each basic task on each airplane. Once this cross-reference system 
has been established, this recording provision of Sections 91 and 121 
requires no additional recording beyond what would otherwise be 
required normally.
    Section 121.380(a)(1) concerns ``records necessary to show that all 
requirements for the issuance of an airworthiness release under section 
121.709 have been met.'' Section 91.417(a)(1) contains a similar 
requirement. These are also referred to as ``dirty fingerprint 
records.'' This provision of sections 91 and 121 requires most of the 
recording that would result from this proposed AD. Each time a basic 
task is performed, the operator would be required to make a ``dirty 
fingerprint'' record of the task, identifying what actions were 
accomplished. It should be noted, however, that these records are not 
different from the records made for any other actions taken under the 
operator's maintenance/inspection program.
    In addition to the record making requirements, discussed above, 
sections 91 and 121 of the FAR impose requirements for record 
retention:
    Section 121.380(b)(1) and Section 91.417(b)(1) require that the 
``dirty fingerprint'' records be retained until the work is repeated or 
superseded by other work, or for one year after the work is performed. 
Therefore, most of the records resulting from this proposed AD would 
not have to be retained indefinitely. However, such retention might 
facilitate subsequent transfers, or substantiate requests for 
repetitive interval escalations, and therefore, may be in the 
operator's interest.
    Section 121.380(b)(2) requires that the records specified in 
paragraph 121.380(a)(2) [current status of AD's and current inspection 
status] be retained and transferred with the airplane at the time it is 
sold. Section 91.417(b)(2) contains a similar requirement.
    These recording requirements are not considered to be unduly 
burdensome and are considered the minimum necessary to enable the 
cognizant FAA Maintenance Inspector to perform proper surveillance and 
to ensure that the objectives of the proposed rule are being fulfilled.
    However, because of the numerous concerns expressed previously by 
operators regarding the recordkeeping obligations imposed by section 
121.380 with regard to similar rulemaking on corrosion prevention and 
control programs, the FAA has included in this proposal certain 
provisions for alternative recordkeeping methods. Proposed paragraph 
(b)(1) would provide for the development and implementation of such 
alternative methods, which must be approved by the FAA. For example, 
operators may choose to submit proposals to record compliance with 
paragraphs (d) through (g) of the AD by a means other than they 
normally use to record AD status. (The FAA has developed guidance 
material that will contain information to be considered by FAA 
Principal Maintenance Inspectors (PMI) when reviewing proposals for 
alternative recordkeeping methods.)
    Paragraph (c) of the proposal provides for increasing a ``Repeat 
Inspection Time'' interval by up to 10% in order to accommodate 
unanticipated scheduling requirements. Operators would be required to 
inform the FAA within 30 days of such increases.
    Paragraph (d)(1) of the proposal sets forth the reporting actions 
that are necessary to be accomplished when Level 3 corrosion is 
determined to exist. Within 7 days after such a determination is made, 
an operator would be required to accomplish one of the following 
actions:
    1. Submit a report of the determination to the FAA and complete the 
basic task in the affected area on the remainder of the Model F-27 
series airplanes in the operator's fleet; or
    2. Submit a proposed schedule, for approval by the FAA, for 
performing the basic tasks in the affected area on the remainder of the 
operator's Model F-27 series fleet; or
    3. Submit data substantiating that the Level 3 corrosion was an 
isolated occurrence.
    Once the FAA has received such a report, it may, in conjunction 
with normal surveillance activities, request additional information 
regarding the results of the basic tasks performed on the remainder of 
the operator's Model F-27 series fleet.
    Paragraph (d)(2) of the proposal specifies that the FAA may impose 
schedules different from what an operator has proposed under paragraph 
(d)(1), if it is found that changes are necessary to ensure that any 
other Level 3 corrosion in the operator's Model     F-27 series fleet 
is detected in a timely manner.
    Paragraph (d)(3) of the proposal would require that, within the 
time schedule approved by the FAA, the operator must accomplish the 
basic tasks in the affected areas on the remaining airplanes in its 
Model F-27 series fleet to ensure that any other Level 3 corrosion is 
detected.
    Paragraph (e) would require that, upon finding corrosion exceeding 
Level 1 during a repetitive inspection, an operator must adjust its 
program to ensure that future corrosion findings are limited to Level 1 
or better. Where corrective action is necessary to reduce corrosion to 
Level 1 or better, an operator must submit a proposal for a means of 
corrective action for the FAA's approval within 60 days after the 
determination of corrosion is made. That means, approved by the FAA, 
must then be implemented to reduce future findings of corrosion in that 
area to Level 1 or better.
    With regard to paragraph (e), it should be noted that if corrosion 
is found and it is not considered representative of the operator's 
fleet, no further corrective action may be necessary, since a means to 
reduce any corrosion to Level 1 or better will have already been 
implemented in the operator's program in accordance with proposed 
paragraph (a) or (b). For example, if a finding of corrosion is 
attributable to a particular spill of mercury or other unique event, or 
if corrosion is found on an airplane recently acquired from another 
operator, the means specified in the existing program may be adequate 
for controlling corrosion in the remainder of the operator's fleet. 
Similarly, if an operator has already implemented means to reduce 
corrosion in an airplane area based on previous findings, no additional 
corrective action may be necessary. In reviewing the reports submitted 
in accordance with the AD, the FAA will monitor the effectiveness of 
the operator's means to reduce corrosion. If the FAA determines that an 
operator has failed to implement adequate means to reduce corrosion to 
Level 1 or better, appropriate action will be taken to ensure 
compliance with this paragraph.
    Paragraph (f) of the proposal concerns adding airplanes to an 
operator's fleet, and the procedures that must be followed with regard 
to corrosion prevention and control. This paragraph differentiates 
between procedures applicable to added airplanes that previously were 
maintained in accordance with this AD and those that were not so 
maintained. For airplanes that previously have been maintained in 
accordance with the proposed requirements of this AD action, the first 
basic task in each aircraft zone to be performed by the new operator 
would be required to be performed in accordance with either the 
previous operator's or the new operator's inspection schedule, 
whichever would result in the earlier accomplishment date for that 
task. For airplanes that have not been maintained in accordance with 
the proposed requirements of this AD action, the first basic task in 
each aircraft zone to be performed by the new operator would be 
required to be performed before the airplane is placed in service, or 
in accordance with a schedule approved by the FAA.
    With regard to the requirements of paragraph (f), the FAA considers 
it essential that operators ensure that transferred airplanes are 
inspected in accordance with the baseline corrosion prevention and 
control program on the same basis as if there were continuity in 
ownership. Scheduling of the inspections for each airplane must not be 
delayed or postponed due to a transfer of ownership; in some cases, 
such postponement could continue indefinitely if an airplane is 
transferred frequently from one owner to another. The proposed rule 
would require that the specified procedures be accomplished before any 
operator places into service any airplane subject to the requirements 
of the proposed AD.
    Paragraph (g) of the proposal would require that reports of Level 2 
and Level 3 corrosion be submitted to Fokker within certain time 
periods after such corrosion is detected. A note has been included in 
this paragraph indicating that reporting to the FAA of any Level 2 or 
Level 3 corrosion found as a result of any opportunity inspections is 
highly desirable. Operators are not relieved, however, from reporting 
corrosion findings as required by FAR section 121.703.
    The FAA estimates that 55 airplanes of U.S. registry would be 
affected by this proposed AD. It would take an average of approximately 
7 work hours per basic task to accomplish the 75 basic tasks called out 
in the Document; this represents a total average of 525 work hours. The 
average labor rate is $55 per work hour. Based on these figures, the 
total cost impact of the proposed AD on U.S. operators for the 6-year 
average inspection cycle is estimated to be $1,588,125, or $28,875 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 FAA recognizes that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. Because AD's 
require specific actions to address specific unsafe conditions, they 
appear to impose costs that would not otherwise be borne by operators. 
However, because of the general obligation of operators to maintain 
aircraft in an airworthy condition, this appearance is deceptive. 
Attributing those costs solely to the issuance of this AD is 
unrealistic because, in the interest of maintaining safe aircraft, most 
prudent operators would accomplish the required actions even if they 
were not required to do so by the AD.
    A full cost-benefit analysis has not been accomplished for this 
proposed AD. As a matter of law, in order to be airworthy, an aircraft 
must conform to its type design and be in a condition for safe 
operation. The type design is approved only after the FAA makes a 
determination that it complies with all applicable airworthiness 
requirements. In adopting and maintaining those requirements, the FAA 
has already made the determination that they establish a level of 
safety that is cost-beneficial. When the FAA, as in this proposed AD, 
makes a finding of an unsafe condition, this means that this cost-
beneficial level of safety is no longer being achieved and that the 
proposed actions are necessary to restore that level of safety. Because 
this level of safety has already been determined to be cost-beneficial, 
a full cost-benefit analysis for this proposed AD would be redundant 
and unnecessary.
    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 14 
CFR part 39 of the Federal Aviation Regulations 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.


Sec. 39.13  [Amended]

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

Fokker: Docket 93-NM-76-AD.

    Applicability: Model F-27 Mark 100, 200, 300, 400, 500, 600, 
700, and 800 series airplanes (does not include Model F-27 MK 050 
series airplanes), certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.

    Note 1: This AD references Fokker Document SE-291, ``F-27 
Corrosion Control Program,'' including all revisions through October 
1, 1993, (hereafter referred to as ``the Document''), for basic 
tasks, definitions of corrosion levels, compliance times, and 
reporting requirements. In addition, this AD specifies inspection 
and reporting requirements beyond those included in the Document. 
Where there are differences between the AD and the Document, the AD 
prevails.
    Note 2: As used throughout this AD, the term ``the FAA'' is 
defined differently for different operators, as follows: For those 
operators complying with paragraph (a) of this AD, ``the FAA'' is 
defined as ``the Manager of the Standardization Branch, ANM-113, 
FAA, Transport Airplane Directorate.'' For those operators operating 
under Federal Aviation Regulation (FAR) part 121 or 129, and 
complying with paragraph (b) of this AD, ``the FAA'' is defined as 
``the cognizant Principal Maintenance Inspector (PMI).'' For those 
operators operating under FAR part 91 or 125, and complying with 
paragraph (b) of this AD, ``the FAA'' is defined as ``the cognizant 
Maintenance Inspector at the appropriate FAA Flight Standards 
office.''
    Note 3: The FAA recommends that priority for implementing the 
corrosion prevention and control program, specified in this AD, be 
given to older aircraft and areas requiring a significant upgrade of 
previous maintenance procedures to meet the program requirements.

    To preclude degradation of the structural capabilities of the 
airplane due to the problems associated with corrosion, accomplish 
the following:
    (a) Except as provided in paragraph (b) of this AD, complete 
each of the basic tasks specified in section 2.4 of the Document in 
accordance with the procedures of the Document, and the schedule 
specified in paragraphs (a)(1) and (a)(2) of this AD.

    Note 4: A ``basic task,'' as defined in section 2.4 of the 
Document, includes inspections; procedures for a corrective action, 
including repairs, under identified circumstances; application of 
sealants or corrosion inhibitors; and other follow-on actions.
    Note 5: Airplane ``areas'' are those items listed in columnar 
form in the ``ACTION'' statement of each task, as listed in the 
Document.
    Note 6: Basic tasks completed in accordance with the Document 
before the effective date of this AD may be credited for compliance 
with the initial basic task requirements of paragraph (a)(1) of this 
AD.
    Note 7: Where non-destructive inspection (NDI) methods are 
employed, in accordance with section 2.4 of the Document, the 
standards and procedures used must be acceptable to the 
Administrator in accordance with FAR section 43.13.

    (1) Complete the initial basic task of each aircraft zone 
specified in section 2.4 of the Document as follows:
    (i) For airplane areas that have not yet exceeded the ``Initial 
Inspection Time (IIT)'' for a basic task as of one year after the 
effective date of this AD: Initial compliance must occur no later 
than the IIT, or no later than one Repeat Inspection Time (RIT) 
interval measured from a date one year after the effective date of 
this AD, whichever occurs later.
    (ii) For airplane areas that have exceeded the IIT for a 
particular basic task as of one year after the effective date of 
this AD: Initial compliance must occur within one RIT interval for 
that task, or within 6 years, measured from a date one year after 
the effective date of this AD, whichever occurs first.
    (iii) Notwithstanding paragraphs (a)(1)(i) and (a)(1)(ii) of 
this AD, accomplish the initial basic task, for each area that 
exceeds the IIT for that area, at a minimum rate of one such area 
every two years, beginning one year after the effective date of this 
AD.

    Note 8: This paragraph does not require inspection of any area 
that has not exceeded the IIT for that area.
    Note 9: This minimum rate requirement may cause an undue 
hardship on some small operators. In those circumstances, requests 
for adjustments to the implementation rate will be evaluated on a 
case-by-case basis under the provisions of paragraph (h) of this AD.

    (2) Repeat each basic task at a time interval not to exceed the 
RIT interval specified in the Document for that task.
    (b) As an alternative to the requirements of paragraph (a) of 
this AD: Prior to one year after the effective date of this AD, 
revise the FAA-approved maintenance/inspection program to include 
the corrosion control program specified in the Document; or to 
include an equivalent program that is approved by the FAA. In all 
cases, the initial basic task for each airplane area must be 
completed in accordance with the compliance schedule specified in 
paragraph (a)(1) of this AD.
    (1) Any operator complying with paragraph (b) of this AD may use 
an alternative recordkeeping method to that otherwise required by 
FAR section 91.417 or section 121.380 for the actions required by 
this AD, provided it is approved by the FAA and is included in a 
revision to the FAA-approved maintenance/inspection program.
    (2) Subsequent to the accomplishment of the initial basic task, 
extensions of RIT intervals specified in the Document must be 
approved by the FAA.
    (c) To accommodate unanticipated scheduling requirements, it is 
acceptable for an RIT interval to be increased by up to 10%, but not 
to exceed 6 months. The FAA must be informed, in writing, of any 
such extension within 30 days after such adjustment of the schedule.
    (d)(1) If, as a result of any inspection conducted in accordance 
with paragraphs (a) or (b) of this AD, Level 3 corrosion is 
determined to exist in any airplane area, accomplish either 
paragraph (d)(1)(i) or (d)(1)(ii) within 7 days after such 
determination:
    (i) Submit a report of that determination to the FAA and 
complete the basic task in the affected aircraft zones on all Model 
F-27 series airplanes in the operator's fleet; or
    (ii) Submit to the FAA for approval one of the following:
    (A) A proposed schedule for performing the basic tasks in the 
affected aircraft zones on the remaining Model F-27 series airplanes 
in the operator's fleet, which is adequate to ensure that any other 
Level 3 corrosion is detected in a timely manner, along with 
substantiating data for that schedule; or
    (B) Data substantiating that the Level 3 corrosion found is an 
isolated occurrence.

    Note: 10: Notwithstanding the provisions of section 2.1 of the 
Document, which would permit corrosion that otherwise meets the 
definition of Level 3 corrosion (i.e., which is determined to be a 
potentially urgent airworthiness concern requiring expeditious 
action) to be treated as Level 1 if the operator finds that it ``can 
be attributed to an event not typical of the operator's usage of 
other airplanes in the same fleet,'' this paragraph requires that 
data substantiating any such finding be submitted to the FAA (ref. 
Note 2 of this AD) for approval.

    (2) The FAA may impose schedules other than those proposed, upon 
finding that such changes are necessary to ensure that any other 
Level 3 corrosion is detected in a timely manner.
    (3) Within the time schedule approved under paragraph (d)(1) or 
(d)(2) of this AD, accomplish the basic tasks in the affected 
aircraft zones of the remaining Model F-27 series airplanes in the 
operator's fleet.
    (e) If, as a result of any inspection after the initial 
inspection conducted in accordance with paragraph (a) or (b) of this 
AD, it is determined that corrosion findings exceed Level 1 in any 
area, within 60 days after such determination, implement a means, 
approved by the FAA, to reduce future findings of corrosion in that 
area to Level 1 or better.
    (f) Before any operator places into service any airplane subject 
to the requirements of this AD, a schedule for the accomplishment of 
basic tasks required by this AD must be established in accordance 
with paragraph (f)(1) or (f)(2) of this AD, as applicable:
    (1) For airplanes previously maintained in accordance with this 
AD, the first basic task in each aircraft zone to be performed by 
the new operator must be accomplished in accordance with the 
previous operator's schedule or with the new operator's schedule, 
whichever would result in the earlier accomplishment date for that 
task. After each basic task has been performed once, each subsequent 
task must be performed in accordance with the new operator's 
schedule.
    (2) For airplanes that have not been previously maintained in 
accordance with this AD, the first basic task for each aircraft zone 
to be performed by the new operator must be accomplished prior to 
further flight or in accordance with a schedule approved by the FAA.
    (g) Within 7 days after the date of detection of any Level 3 
corrosion, and within 3 months after the date of detection of any 
Level 2 corrosion, submit a report to Fokker of such findings, in 
accordance with section 2.5 of the Document.

    Note 11: Reporting to the FAA of Level 2 and Level 3 corrosion 
found as a result of any opportunity inspections is highly 
desirable.

    (h) An alternative method of compliance or adjustment of the 
compliance time, which provides an acceptable level of safety, may 
be used when approved by the Manager, Standardization Branch, ANM-
113, FAA, Transport Airplane Directorate. Operators shall submit 
their requests through the cognizant Maintenance Inspector at the 
appropriate FAA Flight Standards office, who may concur or comment 
and then send it to the Manager, Standardization Branch, ANM-113.

    Note 12: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (i) Special flight permits may be issued in accordance with FAR 
21.197 and 21.199 to operate the airplane to a location where the 
requirements of this AD can be accomplished.
    (j) Reports of inspection results required by this AD have been 
approved by the Office of Management and Budget (OMB) under the 
provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et 
seq.) and have been assigned OMB Control Number 2120-0056.

    Issued in Renton, Washington, on March 8, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-5850 Filed 3-11-94; 8:45 am]
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