[Federal Register Volume 63, Number 57 (Wednesday, March 25, 1998)]
[Proposed Rules]
[Pages 14385-14387]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-7672]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-09-AD]
RIN 2120-AA64


Airworthiness Directives; Pilatus Aircraft Ltd. PC-6, PC-6/A, PC-
6/B, and PC-6/C Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to certain Pilatus Aircraft Ltd. (Pilatus) PC-6, 
PC-6/A, PC-6/B, and PC-6/C series airplanes equipped with turbo-prop 
engines. The proposed action would require modifying the fuel system to 
improve the venting between the collector tank, the main wing tanks, 
and the engine. The proposed AD is the result of mandatory continuing 
airworthiness information (MCAI) issued by the airworthiness authority 
for Switzerland. The actions specified by the proposed AD are intended 
to prevent engine fuel starvation during maximum climb and descent 
caused by poor fuel tank venting with low fuel levels, which, if not 
corrected, could result in a loss of engine power during critical 
phases of flight.

DATES: Comments must be received on or before April 27, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 97-CE-09-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 Aircraft Ltd., Customer Liaison Manager, CH-6370 Stans, 
Switzerland; telephone: +41 41-6196 233; facsimile: +41 41-6103 351. 
This information also may be examined at the Rules Docket at the 
address above.

FOR FURTHER INFORMATION CONTACT: Mr. Roman T. Gabrys, Aerospace 
Engineer, FAA, Small Airplane Directorate, Airplane Certification 
Service, 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-09-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

[[Page 14386]]

FAA, Central Region, Office of the Regional Counsel, Attention: Rules 
Docket No. 97-CE-09-AD, Room 1558, 601 E. 12th Street, Kansas City, 
Missouri 64106.

Discussion

    The Federal Office for Civil Aviation (FOCA), which is the 
airworthiness authority for Switzerland, notified the FAA that an 
unsafe condition may exist on certain Pilatus PC-6, PC-6/A, PC-6/B, and 
PC-6/C series airplanes. The FOCA reports that there have been 
incidents of engines stopping during flight on these airplanes during 
parachute dropping and sky-diving missions. The investigation disclosed 
that the circumstances leading to the incidents were: frequently 
running at minimum fuel levels; making long and steep climbs and 
descents; and, making immediate landing and take-off turn-arounds with 
the engine running. Operating these airplanes in this manner may not 
allow the collector fuel tank to completely refill, especially if the 
fuel level is low. Under sustained, maximum achievable climb and 
descent altitudes, the low fuel level, combined with the current fuel 
venting system, allows air inclusion in the fuel lines.
    These conditions, if not corrected, could result in engine fuel 
starvation and loss of engine power during critical phases of flight.

Relevant Service Information

    Pilatus has issued Service Bulletin No. PC-6-SB-171, dated October 
18, 1995, which specifies procedures for modifying the airplane fuel 
system, which improves the venting of the collector tank between the 
main wing tanks and the engine. This modification would assist in 
eliminating the possibility of air inclusion in the fuel lines while 
operating at maximum climb and descent altitudes. This service 
information also recommends inserting Airplane Flight Manual (AFM) 
Temporary Revision dated October 18, 1995, to remind the pilot to avoid 
repeated prolonged descents.
    The FOCA classified this service bulletin as mandatory and issued 
Swiss AD HB 95-451, dated November 1, 1995, in order to assure the 
continued airworthiness of these airplanes in Switzerland.

The FAA's Determination

    These airplane models are manufactured in Switzerland and are type 
certificated for operation in the United States under the provisions of 
Sec. 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the 
applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the FOCA has kept the FAA informed 
of the situation described above.
    The FAA has examined the findings of the FOCA, reviewed all 
available information, including the service information referenced 
above, and determined that AD action is necessary for products of this 
type design that are certificated for operation in the United States.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other Pilatus PC-6, PC-6/A, PC-6/B, and PC-6/C 
series airplanes of the same type design registered in the United 
States, the FAA is proposing AD action. The proposed AD would require 
modifying the airplane's fuel venting system. Accomplishment of the 
proposed modification would be in accordance with Pilatus PC-6 Service 
Bulletin No. PC-6-SB-171, dated October 18, 1995.

Differences Between the Service Information, the FOCA AD, and the 
Proposed AD Action

    The manufacturer recommends the modification of the fuel venting 
system and the insertion of a temporary revision to the AFM, and FOCA 
requires this temporary AFM insertion and modification for airplanes 
operated in Switzerland. The Swiss AD requires the AFM revision be 
accomplished prior to further flight and requires the revision to 
remain in the AFM until the venting modification is accomplished. The 
FOCA requires that the modification be accomplished within 90 days from 
receipt of the service bulletin.
    The FAA does not propose to require insertion of the temporary AFM 
revision. The FAA proposes the modification of the fuel venting system 
and the calendar compliance time that is required by the Swiss AD.

Cost Impact

    The FAA estimates that 29 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 10 
workhours per airplane to accomplish the proposed action, and that the 
average labor rate is approximately $60 an hour. Parts cost 
approximately $614 per airplane. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be $35,206 
or $1,214 per airplane.

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 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:

Pilatus Aircraft Ltd.: Docket No. 97-CE-09-AD.

    Applicability: Models PC-6, PC-6-H1, PC-6-H2, PC-6/350, PC-6/
350-H1, PC-6/350-H2, PC-6/A, PC-6/A-H1, PC-6/A-H2, PC-6/B-H2, PC-6/
B1-H2, PC-6/B2-H2, PC-6/B2-H4, PC-6/C-H2, and PC-6/C1-H2 airplanes 
(serial numbers 001 through 915), certificated in any category, that 
are equipped with turbo-prop engines.

    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

[[Page 14387]]

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.

    Compliance: Required within the next 3 calendar months after the 
effective date of this AD, unless already accomplished.
    To prevent engine fuel starvation during maximum climb and 
descent caused by poor fuel tank venting with low fuel levels, 
which, if not corrected, could result in a loss of engine power 
during critical phases of flight, accomplish the following:
    (a) Modify the fuel venting system in accordance with the 
Accomplishment Instructions section in Pilatus PC-6 Service Bulletin 
No. PC-6-SB-171, dated October 18, 1995.
    (b) 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.
    (c) 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.

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

    (d) Questions or technical information related to Pilatus 
Service Bulletin No. PC-6-SB-171, dated October 18, 1995, should be 
directed to Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6370 
Stans, Switzerland; telephone: +41 41-6196 233; facsimile: +41 41-
6103 351. This service information may be examined at the FAA, 
Central Region, Office of the Regional Counsel, Room 1558, 601 E. 
12th Street, Kansas City, Missouri 64106.

    Note 3: The subject of this AD is addressed in Swiss AD HB 95-
451, dated November 1, 1995.

    Issued in Kansas City, Missouri, on March 18, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-7672 Filed 3-24-98; 8:45 am]
BILLING CODE 4910-13-P