[Federal Register Volume 62, Number 207 (Monday, October 27, 1997)]
[Rules and Regulations]
[Pages 55500-55502]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-28082]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-CE-17-AD; Amendment 39-10173; AD 97-22-02]
RIN 2120-AA64


Airworthiness Directives; Pilatus Britten-Norman Ltd. Models BN-
2, BN-2A, BN-2B, and BN-2T Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
applies to Pilatus Britten-Norman Ltd. (PBN) BN-2, BN-2A, BN-2B, and 
BN-2T series airplanes. This action requires modifying the upper engine 
mounting brackets on the wing front spar as terminating action for the 
repetitive inspections that were required in AD 84-23-06. AD 84-23-06 
is being revised in a separate action, deleting the Pilatus BN-2, BN-
2A, BN-2B, and BN-2T series airplanes from its applicability. This AD 
is prompted by several reports of cracks in the upper engine mounting 
brackets and a new terminating action to eliminate the repetitive 
inspections for Pilatus BN-2, BN-2A, BN-2B, and BN-2T series airplanes. 
The actions specified by this AD are intended to prevent the failure of 
the upper engine mounting brackets on the wing mounted engines, which 
could possibly cause structural failure of the airplane.

DATES: Effective November 24, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of November 24, 1997.

ADDRESSES: Service information that applies to this AD may be obtained 
from Pilatus Britten-Norman Ltd., Bembridge, Isle of Wight, United 
Kingdom PO35 5PR; telephone 44-19-83-872511; facsimile 44-19-83-873246. 
This information may also be examined at the Federal Aviation 
Administration (FAA), Central Region, Office of the Regional Counsel, 
Attention: Rules Docket 96-CE-17-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106; or at the Office of the Federal Register, 
800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Mr. S. M. Nagarajan, Project Officer, 
Small Airplane Directorate, Aircraft Certification Service, FAA, 1201 
Walnut, suite 900, Kansas City, Missouri 64105; telephone (816) 426-
6932; facsimile (816) 426-2169.

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This AD

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an AD that would apply to Pilatus BN-2, BN-2A, 
BN-2B, and BN-2T series airplanes was published in the Federal Register 
on March 10, 1997 (62 FR 10754). The action proposed to require 
initially inspecting the upper engine mounting brackets on the wing 
mounted engines for:
    (1) Cracks at the bolt-holes,
    (2) Elongation of the bolt holes,
    (3) Fretting within the holes,
    (4) Cracks at the rivet holes,
    (5) Distortion or delamination of the lugs, and that
    (6) The bearings are the correct length and the bolts are not 
threadbound.
    If there is no evidence of damage or defects similar to any of the 
above-mentioned items, the proposed AD would require repetitive 
inspections at regular intervals until the accumulation of 2,000 hours 
time-in-service after the effective date of the AD, at which time the 
AD would require accomplishing Pilatus Modification NB/M/1147.
    If any damage or defects are found similar to any of the six items 
previously mentioned, this action would require immediately 
accomplishing Pilatus Modification NB/M/1147. This modification 
consists of replacing damaged brackets, bolts, and bushes with parts of 
an improved design. Accomplishing this modification is considered a 
terminating action to the repetitive inspections. Accomplishment of the 
AD would be in accordance with Pilatus Britten-Norman Service Bulletin 
No. BN-2/SB.61, Issue 5, dated December 9, 1981.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. No comments were received on the 
proposed rule or the FAA's determination of the cost to the public.

The FAA's Aging Aircraft Policy

    The FAA has determined that reliance on critical repetitive 
inspections on aging commuter-class airplanes carries an unnecessary 
safety risk when a design change exists that could eliminate or, in 
certain instances, reduce the number of those critical inspections. In 
determining what inspections are critical, the FAA considers (1) the 
safety consequences if the known problem is not detected during the 
inspection; (2) the probability of the problem not being detected 
during the inspection; (3) whether the inspection area is difficult to 
access; and (4) the possibility of damage to an adjacent structure as a 
result of the problem.
    These factors have led the FAA to establish an aging commuter-class 
aircraft policy that requires incorporating a known design change when 
it could replace a critical repetitive inspection.
    For Pilatus BN-2, BN-2A, BN-2B, and BN-2T series airplanes, the 
manufacturer has incorporated a design change that would replace 
damaged bolts, brackets, and bushes with parts of improved design, 
which would

[[Page 55501]]

terminate the repetitive inspections of the upper engine mounting 
brackets on the wing mounted engines required by AD 84-23-06. It is AD 
84-23-06 that required the repetitive inspections on the Pilatus BN-2, 
BN-2A, BN-2B, and BN-2T series airplanes and the Pilatus BN-2A MK. 111 
series airplanes. A separate action (Docket 84-CE-18-AD) is being 
published concurrently with this AD, and revises AD 84-23-06 so that 
the BN-2A MK.111 series airplanes will be the only airplanes to which 
AD 84-23-06 applies.
    Based on its aging commuter-class aircraft policy and after 
reviewing all available information, the FAA has determined that AD 
action should be taken to modify the upper engine wing mounting 
brackets of the affected airplanes to eliminate the repetitive short-
interval inspections, and to prevent failure of the upper engine wing 
mounting brackets on wing mounted engines, which could possibly cause 
structural failure of the airplane.

The FAA's Determination

    After careful review of all available information related to the 
subject presented above, the FAA has determined that air safety and the 
public interest require the adoption of the rule as proposed except for 
minor editorial corrections. The FAA has determined that these minor 
corrections will not change the meaning of the AD and will not add any 
additional burden upon the public than was already proposed.

Cost Impact

    The FAA estimates that 112 airplanes in the U.S. registry will be 
affected by the AD, that it will take approximately 37 workhours per 
airplane to accomplish the initial inspection and modification, and 
that the average labor rate is approximately $60 an hour. Parts cost 
approximately $800 per airplane to accomplish the modification. Based 
on these figures, the total cost impact of the AD on U.S. operators is 
estimated to be $338,240 or $3,020 per airplane. This figure is based 
on the initial inspection and modification only. It does not take into 
account the cost for the repetitive inspections that may be incurred 
over the life of the airplane until the modification is accomplished. 
The FAA has no way of determining how many owners/operators have 
accomplished the proposed action and, therefore assumes that none of 
the owners/operators of the affected airplanes have accomplished the 
proposed action.

The AD Action's Impact Utilizing the FAA's Aging Commuter Class 
Aircraft Policy

    The intent of the FAA's aging commuter airplane program is to 
ensure safe operation of commuter-class airplanes that are in 
commercial service without adversely impacting private operators. Of 
the approximately 112 airplanes in the U.S. registry that will be 
affected by this AD, the FAA has determined that approximately 18 
percent are operated in scheduled passenger service by 11 different 
operators. A significant number of the remaining 82 percent are 
operated in other forms of air transportation such as air cargo and air 
taxi.
    This AD allows 2,000 hours time-in-service (TIS) after the 
effective date of the AD before mandatory accomplishment of the design 
modification. The average utilization of the fleet for those airplanes 
in commercial commuter service is approximately 25 to 50 hours TIS per 
week. Based on these figures, operators of commuter-class airplanes 
involved in commercial operation will have to accomplish the 
modification within 10 to 20 calendar months after the effective date 
of the AD. For private owners, who typically operate between 100 to 200 
hours TIS per year, this will allow 5 to 10 years before the 
modification will be mandatory.

Regulatory Impact

    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 copy of the final 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, 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 a new airworthiness directive 
(AD) to read as follows:

97-22-02  Pilatus Britten-Norman LTD.: Amendment 39-10173; Docket 
No. 96-CE-17-AD.

    Applicability: Models BN-2 (serial numbers 1 through 2033), BN-
2A and BN-2B (serial numbers 1 through 2116), and BN-2T (serial 
numbers 419, and 2030 through 2033) 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 (g) 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 within the next 500 hours time-in-service 
(TIS) after the last inspection required by AD 84-23-06, or within 
the next 100 hours TIS after the effective date of this AD, 
whichever occurs later, unless already accomplished, and thereafter 
as indicated in the body of this AD.
    To prevent failure of the upper mounting brackets on both wing 
mounted engines, which could cause structural failure of the 
airplane, accomplish the following:
    (a) Inspect the upper mounting brackets, bolts, and bushes on 
both wing mounted engines in accordance with the ``ACTION-
Inspection'' section in Pilatus Britten-Norman (Pilatus) Service 
Bulletin (SB) No. BN-2/SB.61, Issue 5, dated December 9, 1981, for:
    (1) Cracks at the bolt holes,
    (2) Elongation of the bolt holes,
    (3) Fretting within the bolt holes,
    (4) Cracks at the rivet holes,
    (5) Distortion or delamination of the lugs, and

[[Page 55502]]

    (6) Incorrect bearing length and threadbound bolts, b) If the 
inspection reveals any evidence of damage or defects similar to the 
items in paragraphs (a)(1) through (a)(6), prior to further flight, 
accomplish Pilatus Modification NB/M/1147 by replacing the brackets, 
bushes, and bolts with brackets, bushes, and bolts of improved 
design in accordance with paragraphs 1, 2, 3, and 5 of the 
``ACTION--Rectification/Modification'' section in Pilatus SB No. BN-
2/SB.61, Issue 5, dated December 9, 1981.
    (c) If damage or defects are found on just one of the two 
brackets on each engine, then both brackets must be replaced, prior 
to further flight, in accordance with paragraph 1 of the ``ACTION--
Rectification/Modification'' section in Pilatus SB No. BN-2/SB.61, 
Issue 5, dated December 9, 1981.
    (d) If no damage or defects are found similar to the items in 
paragraphs (a)(1) through (a)(6) of this AD, continue to inspect at 
intervals not to exceed 500 hours TIS, until the accumulation of 
2,000 hours TIS after the effective date of this AD, at which time 
Modification NB/M/1147 must be accomplished on both upper mounting 
brackets on both engines in accordance with paragraphs 1, 2, 3, and 
5 of the ``ACTION--Rectification/Modification'' section of Pilatus 
SB No. BN-2/SB.61, Issue 5, dated December 9, 1981.
    (e) Accomplishing Modification NB/M/1147 in the ``ACTION--
Rectification/Modification'' section of Pilatus SB No. BN-2/SB.61, 
Issue 5, dated December 9, 1981, is considered terminating action to 
the repetitive inspections required in paragraph (d) of this AD.
    (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.
    (g) An alternative method of compliance or adjustment of the 
initial or repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, Small Airplane 
Directorate, Aircraft Certification Service, FAA, 1201 Walnut, suite 
900, Kansas City, Missouri 64105. The request shall be forwarded 
through an appropriate FAA Maintenance Inspector, who may add 
comments and then send it to the Manager, Small Airplane 
Directorate.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from Small Airplane Directorate.

    (h) The inspections and modifications required by this AD shall 
be done in accordance with Pilatus Britten-Norman Ltd. Service 
Bulletin No. BN-2/SB.61, Issue 5, dated December 9, 1981. 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 Pilatus Britten-Norman Ltd., 
Bembridge, Isle of Wight, United Kingdom PO35 5PR. Copies may be 
inspected at the FAA, Central Region, Office of the Regional 
Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.
    (i) This amendment (39-10173) becomes effective on November 24, 
1997.

    Issued in Kansas City, Missouri, on October 16, 1997.
Mary Ellen A. Schutt,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-28082 Filed 10-24-97; 8:45 am]
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