[Federal Register Volume 62, Number 129 (Monday, July 7, 1997)]
[Proposed Rules]
[Pages 36240-36242]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-17545]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-12-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to supersede airworthiness directive 
(AD) 97-03-03, which is applicable to Pilatus Britten-Norman Ltd. 
(Pilatus) BN-2, BN-2A, and BN-2B series airplanes that do not have 
generator terminal diodes installed with Modification NB/M/1571. This 
AD currently requires removing the terminal diodes that have a 70 amp 
direct current (DC) Generation System, referred to as Modification NB/
M/1148, and installing Modification NB/M/1571, which consists of new 
terminal diodes with a higher amp rating. The proposed action would 
retain the same actions required in AD 97-03-03, and would change the 
applicability section of the proposed AD. Reports from operators that 
one or both diodes were failing prompted this action, as well as 
reports from operators that the applicability section of AD 97-03-03 
was wrong. The actions specified by this AD are intended to prevent a 
loss of electrical power to the navigation, communications, and light 
systems, which could impair the pilot's ability to maintain control of 
the airplane.

DATES: Comments must be received on or before September 5, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 97-CE-12-AD, Room 1558, 601 E. 
12th Street, Kansas City, Missouri 64106. Comments may be inspected at 
this location between 8 a.m. and 4 p.m., Monday through Friday, 
holidays excepted.
    Service information that applies to the proposed AD may be obtained 
from Pilatus Britten-Norman, Ltd., Bembridge, Isle of Wight, United 
Kingdom, PO35 5PR. This information also may be examined at the Rules 
Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Mr. S.M. Nagarajan, Project Officer, 
Small Airplane Directorate, 1201 Walnut, suite 900, Kansas City, 
Missouri, 64106; telephone (816) 426-6932, facsimile (816) 426-2169.

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 should 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 that summarizes 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 No. 97-CE-12-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, Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket No. 97-CE-12-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    The Civil Airworthiness Authority (CAA), which is the airworthiness 
authority for the United Kingdom, notified the FAA that an unsafe 
condition may exist on certain Pilatus Britten-Norman (Pilatus) BN-2, 
BN-2A, and BN-2B series airplanes. The CAA reports that several owners/
operators of these airplanes have experienced diode failure, which 
leads to generator failure during flight. Further investigation has 
shown that the diode rating is not sufficient to maintain the 
generators used to operate the navigation, communication, and light 
system. This condition, if not detected and corrected, could result in 
loss of power to the navigation, communication, and light systems, 
which could result in impairing the pilot's ability to maintain control 
of the airplane.
    Airworthiness Directive 97-03-03, Amendment 39-9909 (62 FR 4908, 
February 3, 1997), currently requires removing the diodes (type 10B1 or 
10D1) installed on the terminals of the STBD (RIGHT) GEN and PORT 
(LEFT) GEN switches (SW2 and SW3), and installing new approved diodes 
that are type 60S6 on Pilatus BN-2, BN-2A, and BN-2B series airplanes.
    These airplane models are manufactured in the United Kingdom and 
are 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 between the 
United Kingdom and the United States. Pursuant to this bilateral 
airworthiness agreement, the CAA has kept the FAA informed of the 
situation described above.

Actions Since Issuance of Previous Rule

    Since publication of AD 97-03-03, the FAA has been informed that 
the applicability section of the AD was misleading. Modification NB/M/
1571 is the increased rated diode used on the Pilatus BN-2, BN-2A, and 
BN-2B series airplanes, if they have a 70-amp DC

[[Page 36241]]

generation system installed. Some of these Pilatus airplanes have a 50-
amp DC generation system and do not require Modification NB/M/1571. The 
proposed action would not apply to certain Pilatus BN-2, BN-2A, and BN-
2B series airplanes with a 50-amp DC generation system installed. If 
Modification NB/M/1148 is incorporated (which is the installation of 70 
amp DC generators with type 10B1 or 10D1 diodes), but Modification NB/
M/1571 is not incorporated, the proposed action would require the 
incorporation of Modification NB/M/1571.

Relevant Service Information

    Pilatus has issued Service Bulletin (SB) BN-2/SB.228, Issue 2, 
dated January 17, 1996, which specifies procedures for removing the 
already installed diodes (type 10B1 or 10D1) in accordance with 
Modification NB/M/1148 and installing the diodes (type 60S6) approved 
for Modification NB/M/1571.
    The CAA classified this service bulletin as mandatory and issued 
CAA AD No. 004-01-96, in order to ensure the continued airworthiness of 
these airplanes in the United Kingdom.

The FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the information described above, the FAA has 
determined that AD action should be taken to prevent a loss of 
electrical power to the navigation, communications, and light systems, 
which could impair the pilot's ability to maintain control of the 
airplane.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in certain Pilatus BN-2, BN-2A, and BN-2B series 
airplanes of the same type design registered in the United States, the 
proposed AD would supersede AD 97-03-03 with a new AD that would change 
the applicability to include the airplanes that have Modification NB/M/
1148 incorporated, but do not have Modification NB/M/1571 incorporated. 
The proposed AD would also retain the same actions as AD 97-03-03, 
which requires removing the diodes (type 10B1 or 10D1), also referred 
to as Modification 1148 installed on the terminals of the STBD (RIGHT) 
GEN and PORT (LEFT) GEN switches (SW2 and SW3), and installing new 
approved diodes that are type 60S6. Accomplishment of the proposed 
action would be in accordance with Pilatus SB BN-2/SB.228, Issue 2, 
dated January 17, 1996.

Cost Impact

    The FAA estimates that one airplane currently on the U.S. registry 
would be affected by the proposed AD, that it would take approximately 
one workhour per airplane to accomplish the proposed action, and that 
the average labor rate is approximately $60 an hour. Parts cost 
approximately $40 per airplane. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be $100. 
The FAA has no way of determining whether or not the owner/operator of 
this airplane has accomplished this action.

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 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) 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 has been placed 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 USC 106(g), 40113, 44701.

Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Airworthiness Directive 
(AD) 97-03-03, Amendment 39-9909, and by adding a new AD to read as 
follows:

Pilatus Britten-Norman Ltd.: Docket No. 97-CE-12-AD; Supersedes AD 
97-03-03, Amendment 39-9909.

    Applicability: BN-2, BN-2A, and BN-2B series airplanes (all 
serial numbers), certificated in any category, that have Pilatus 
Britten-Norman (Pilatus) Modification NB/M/1148 (70 amp DC 
Generation System) incorporated, and do not have Pilatus 
Modification NB/M/1571 (Introduction of Increased Rated Diode-70 amp 
DC Generation System) incorporated.

    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 (d) 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 50 hours time-in-service 
(TIS) after the effective date of this AD, unless already 
accomplished.
    To prevent loss of electrical power to the navigation, 
communications and light systems, which could impair the pilot's 
ability to maintain control of the airplane, accomplish the 
following:
    (a) Remove the diodes (quantity 2, part number (P/N) 340502014, 
type 10B1 or 10D1) installed on the terminals of the STBD (RIGHT) 
GEN and PORT (LEFT) GEN switches (SW2 and SW3), and install new 
approved diodes (quantity 2, P/N NB-81-5873, type 60S6) in 
accordance with the Accomplishment Instructions section in Pilatus 
Britten-Norman Aircraft Manufacturers Service Bulletin (SB) BN-2/
SB.228, Issue 2, dated January 17, 1996.
    (b) Accomplishment of paragraph (a) of this AD is considered 
incorporation of Modification NB/M/1571.
    (c) 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.
    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an equivalent level of safety may be 
approved by the Manager, Small Airplane Directorate, 1201 Walnut, 
suite 900, Kansas City, Missouri, 64106. 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. Alternative methods of compliance approved in 
accordance with AD 97-03-03 are

[[Page 36242]]

considered approved as alternative methods of compliance for this 
AD.

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

    (e) All persons affected by this directive may obtain copies of 
the document referred to herein upon request to Pilatus Britten-
Norman, Ltd., Bembridge, Isle of Wight, United Kingdom, PO35 5PR; or 
may examine this document at the FAA, Central Region, Office of the 
Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, 
Missouri 64106.
    (f) This amendment supersedes AD 97-03-03, Amendment 39-9909.

    Issued in Kansas City, Missouri, on June 27, 1997.
James E. Jackson,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-17545 Filed 7-3-97; 8:45 am]
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