[Federal Register Volume 61, Number 37 (Friday, February 23, 1996)]
[Rules and Regulations]
[Pages 6932-6934]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-3835]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-NM-215-AD; Amendment 39-9521; AD 96-04-09]


Airworthiness Directives; Fokker Model F28 Mark 0100 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to all Fokker Model F28 Mark 0100 series airplanes, that 
requires an inspection to detect the presence of a drain hole in 
certain mounting frames of the auxiliary power unit (APU). If a drain 
hole is present, the AD requires an inspection to detect corrosion of 
the mounting frame, and eventual replacement of the mounting frame. 
This amendment is prompted by a report indicating that corrosion was 
found on a number of mounting frames of the APU. The actions specified 
by this AD are intended to prevent such corrosion, which could lead to 
failure of the frame and consequently render the APU inoperative and/or 
create a potential fire hazard.

DATES: Effective March 25, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 25, 1996.

ADDRESSES: The service information referenced in this AD may be 
obtained from Fokker Aircraft USA, Inc., 1199 North Fairfax Street, 
Alexandria, Virginia 22314. This information may be examined at the 
Federal Aviation Administration (FAA), Transport Airplane Directorate, 
Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the 
Office of the Federal Register, 800 North Capitol Street NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Tim Dulin, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2141; fax (206) 227-1149.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to all Fokker Model F28 Mark 0100 
series airplanes was published in the Federal Register on December 20, 
1994 (59 FR 65514). That action proposed to require an inspection to 
detect the presence of a drain hole in certain mounting frames of the 
auxiliary power unit (APU). If a drain hole is present, the action 
proposed to require an inspection to detect corrosion of the mounting 
frame, and eventual replacement of the mounting frame.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter supports the proposal.
    Another commenter requests that the FAA withdraw the proposal for 
what this commenter perceives as lack of justification. This commenter 
purports that corrosion of the APU frame will not result in a critical 
safety of flight condition. The commenter contends that, even if the 
subject frame were to fail completely, the APU cannot fall or lean 
enough to sever any fuel or electrical lines; therefore, the 
possibility that the failure of the mounting frame could become a 
potential fire hazard is simply conjecture. Based on these assertions, 
the commenter considers that no unsafe condition exists, and requests 
that the FAA review its justification for the proposed rule to ensure 
that it is sufficient to satisfy the requirements of part 39 of the 
Federal Aviation Regulations (FAR).
    The FAA does not concur with either the commenter's request or 
assertions.
    First, the FAA points out that the existing design of the drain 
hole on certain APU mounting frames allows the accumulation of moisture 
on the frame. These frames have been found to be particularly sensitive 
to corrosion caused by such moisture accumulation. Corrosion of these 
frames could cause them to fail, especially when exposed to higher 
loads during airplane touchdown.
    Second, the Rijksluchtvaartdienst (RLD) (which is the airworthiness 
authority for the Netherlands) and the FAA, have determined that, if a 
mounting frame were to fail due to associated corrosion, the APU could 
be displaced and consequently sever APU fuel lines located in the 
adjacent area. The leaking fuel could then pose a fire hazard. This is 
the unsafe condition that this AD intends to prevent. In addition, the 
APU could be rendered inoperative because of the failure of its support 
assembly. If it were inoperative, electrical power may not be available 


[[Page 6933]]
during flight, or both electrical and pneumatic power may not be 
available when the airplane is on the ground, when such power is needed 
via the APU.
    Third, although there have been no reported cases of inoperative 
APU's or fuel leakage caused by the problems associated with the 
failure of the APU mounting frames, the potential for them to occur 
still exists. In fact, when Fokker examined the subject APU mounting 
frames removed from in-service airplanes, it found that up to 73% of 
the thickness at the place of the drain holes in these frames was 
fretted away. This reduced thickness, which is attributed to the 
typical effects of corrosion, weakens the integrity of the frames and, 
consequently, can lead to their failure.
    Finally, according to section 39.1 of the FAR (14 CFR 39.1), the 
issuance of an AD is based on the finding that an unsafe condition 
exists and that condition is likely to exist or develop in aircraft of 
a particular type design. The responsibilities placed on the FAA by the 
Federal Aviation Act do not limit it from making any unsafe condition 
the proper subject of an AD--regardless of whether or not the unsafe 
condition has actually occurred in service and led to an incident or 
accident. When sufficient data exist to demonstrate that an unsafe 
condition is likely to exist or develop on other products of the same 
type design, the issuance of an AD is appropriate in order to address 
that potential unsafe condition and to prevent its occurrence.
    This same commenter also requests clarification as to the 
applicability of the proposed rule. The commenter points out that, 
although both the proposed AD and the parallel Dutch AD are applicable 
to all Fokker Model F28 Mark 0100 series airplanes, the referenced 
Fokker service bulletin calls out only certain airplanes (serial 
numbers 11244 through 11402) in its effectivity listing. This commenter 
knows of four airplanes on which the suspect frames were found, but 
these airplanes were not included in the service bulletin's effectivity 
listing. The commenter believes that the service bulletin should be 
revised to specify that all airplanes must be inspected.
    The FAA does not concur that additional action is necessary. Since 
in-service experience has shown that APU mounting frames are regularly 
removed from and (re-) installed on aircraft upon removal of the APU, 
the FAA has determined that the suspect frames could be installed on 
any Fokker Model F28 Mark 0100 airplane. In light of this, the 
applicability of the AD, which makes all airplanes subject to the 
requirements, is correct. In any case, where there are differences 
between the AD and the service bulletin, the AD prevails.
    One commenter requests that the rule be revised to extend the 
compliance time for replacement of the mounting frames from the 
proposed 30 days or 90 days (depending upon the results of the 
inspection for corrosion) to one year for all cases. The commenter 
states that Fokker has indicated that it has only 2 frames in stock to 
support the replacement requirement. In addition, the lead time for 
procurement of a replacement frame is minimum of 127 days.
    The FAA concurs that some adjustment to this compliance time can be 
made. Reports received by the FAA indicate that most airplanes already 
have been inspected in accordance with the requirements of this AD, and 
have been found not to have the suspect APU mounting frames installed. 
Therefore, the FAA considers that only a limited number of replacement 
mounting frames actually will be required. However, the FAA 
acknowledges that timely parts availability may be a problem for some 
operators. In light of this, the FAA finds that the compliance time for 
replacement of the frame can be extended to 9 months for cases where no 
corrosion is found on the frame, and to 3 months for cases where 
corrosion is found. The FAA finds that safety will not be compromised 
by the extension of these compliance times. The final rule has been 
revised accordingly.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    The FAA estimates that 119 airplanes of U.S. registry will be 
affected by this AD, that it will take approximately 13 work hours per 
airplane to accomplish the required actions, and that the average labor 
rate is $60 per work hour. Based on these figures, the cost impact of 
the AD on U.S. operators is estimated to be $92,820, or $780 per 
airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the requirements of this AD 
action, and that no operator would accomplish those actions in the 
future if this AD were not adopted.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

96-04-09  Fokker: Amendment 39-9521. Docket 94-NM-215-AD.

    Applicability: All Model F28 Mark 0100 series 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 
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 (c) 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.


[[Page 6934]]

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent corrosion of certain mounting frames of the auxiliary 
power unit (APU), which could render the APU inoperative and may 
lead to a potential fire hazard, accomplish the following:
    (a) Within 30 days after the effective date of this AD, perform 
a detailed visual inspection to detect the presence of a drain hole 
in frame member M of the mounting frames, having part number (P/N) 
D67050-407, of the auxiliary power unit (APU), in accordance with 
Fokker Service Bulletin SBF100-49-022, dated August 27, 1992.
    (1) If no drain hole(s) is present, no further action is 
required by this AD.
    (2) If any drain hole is present, prior to further flight, 
perform a detailed visual inspection to detect corrosion on the 
mounting frame of the APU, in accordance with the service bulletin.
    (i) If no corrosion is detected, within 9 months after 
accomplishing the visual inspection, replace the mounting frame with 
a new mounting frame in accordance with the service bulletin.
    (ii) If any corrosion is detected, within 3 months after 
accomplishing the visual inspection, replace the mounting frame with 
a new mounting frame in accordance with the service bulletin.
    (b) As of the effective date of this AD, no person shall install 
on any airplane a mounting frame, having P/N D67050-407, that has a 
drain hole in frame member M.
    (c) 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (d) 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 December 14, 1994.
    (e) The inspection and replacement shall be done in accordance 
with Fokker Service Bulletin SBF100-49-022, dated August 27, 1992. 
This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Fokker Aircraft USA, Inc., 1199 
North Fairfax Street, Alexandria, Virginia 22314. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street NW., suite 700, Washington, DC.
    (f) This amendment becomes effective on March 25, 1996.

    Issued in Renton, Washington, on February 14, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-3835 Filed 2-22-96; 8:45 am]
BILLING CODE 4910-13-P