Airworthiness Directives; Bombardier Inc. Model Otter DHC-3 Airplanes

[Federal Register Volume 63, Number 166 (Thursday, August 27, 1998)]
[Rules and Regulations]
[Pages 45682-45684]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-22824]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-120-AD; Amendment 39-10724; AD 98-18-08]
RIN 2120-AA64


Airworthiness Directives; Bombardier Inc. Model Otter DHC-3 
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 certain Bombardier Inc. (formerly deHavilland Inc) Model 
DHC-3 (Otter) airplanes that have been modified in accordance with A.M. 
Luton Supplemental Type Certificate (STC) No. SA3777NM. This AD 
requires modifying the airplane's electrical system. The actions 
specified by this AD are intended to prevent electrical system failure 
caused by inadequate electrical system design, which could result in 
the loss of the engine instruments or a possible electrical fire in the 
airplane's cockpit.

DATES: Effective October 10, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 10, 1998.

ADDRESSES: Service information that applies to this AD may be obtained 
from A.M. Luton, 3025 Eldridge Avenue, Bellingham, Washington 98225; 
telephone: (360) 671-7817, facsimile: (360) 671-7820. This information 
may also be examined at the Federal Aviation Administration (FAA), 
Central Region, Office of the Regional Counsel, Attention: Rules Docket 
No. 97-CE-120-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. Mike Pasion, Aerospace Engineer, Seattle Aircraft Certification 
Office, FAA, 1601 Lind Avenue, SW, Renton, Washington 98055-4056; 
telephone: (425) 227-2594; facsimile: (425) 227-1181.

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 certain Bombardier 
Inc. Model DHC-3 (Otter) airplanes was published in the Federal 
Register as a notice of proposed rulemaking (NPRM) on April 13, 1998 
(63 FR 17970). The airplanes affected have electrical system 
modifications in accordance with A.M. Luton STC No. SA3777NM. The NPRM 
proposed to require replacing the voltage regulator and voltage-ammeter 
gauge, and modifying the auxiliary bus systems. These modifications 
would bring the airplane's electrical system into compliance with the 
current regulations.
    Accomplishment of the proposed action as specified in the NPRM 
would be in accordance with A.M. Luton Electrical Systems Schematic 
Drawing 20075, Rev. G and E, Sheets 1, 2, and 3, dated May 15, 1998, 
which is referenced in A.M. Luton Service Information Letter SA-SIL-98-
11-03, ``Electrical Systems'', Revision A, dated May 15, 1998.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Comment No. 1: Change in Compliance Time

    Three commenters state that the proposed compliance of 100 hours 
time-in-service (TIS) would be an economic hardship because of the way 
they operate the affected airplanes. Some operators utilize their 
airplanes more than 100 hours in a month's time, with many in revenue 
operations, i.e., air taxi, etc. One operator estimates losing as much 
as $50,000 if the airplanes had to be out of service for approximately 
three days to accomplish the proposed modification. All of the 
commenters state that their fleets have not had any service history 
problems related to electrical fires and proposed that the compliance 
time be lengthened to coincide with the next annual inspection.
    The FAA concurs. In reviewing the service history of the U.S. 
registered fleet and the operational levels of the affected airplanes, 
the FAA has determined that the compliance time should coincide with 
the airplanes' annual maintenance programs. For this reason, the 
compliance time of the proposed AD is changed from 100 hours TIS after 
the effective date of the AD to

[[Page 45683]]

14 calendar months after the effective date the AD. This will give all 
owners/operators of the affected airplanes the opportunity to schedule 
the actions specified in this AD to coincide with regularly scheduled 
maintenance. The final rule will be changed accordingly.

Comment No. 2: Circuit Breaker Requirement

    One commenter states that there isn't a need for the installation 
of a circuit breaker on the wire to the auxiliary bus. The commenter 
expresses that the components drawing from the auxiliary bus utilize 
individual circuit breakers, and there are other distribution wires in 
the original electrical system that are not protected by a circuit 
breaker that have not had any adverse effects.
    The FAA does not concur. The subject of this Ad addresses the 
electrical system changes affected by STC SA3777NM. As installed, the 
electrical system is not in compliance with part 23 of the Federal 
Aviation Regulations (14 CFR part 23). The electrical distribution bus 
was added as part of STC SA3777NM to provide electrical power to the 
additional engine-related loads. This distribution bus is connected to 
the battery through the master solenoid with a 10-gauge wire. If a 
fault in this wire should occur, a hazard in the form of smoke or fire 
in the cockpit could result. If a determination is made that the 
original electrical system is similarly protected and poses a safety 
hazard, then another NPRM may be issued to address that condition. The 
final rule will not change as a result of this comment.

Comment No. 3: Loadmeter vs. Ammeter

    A commenter states that installing a loadmeter should not be 
mandatory. The commenter states that the ammeter is more useful to 
pilots and mechanics in performing their duties.
    The FAA does not concur. In the original, unmodified electrical 
system, the ammeter shunt is placed between the battery and the 
electrical distribution busses, so it properly indicates that the 
current load. With the incorporation of STC SA3777NM, the additional 
engine-related electrical loads were added to the battery side of the 
shunt. As a result, the ammeter does not indicate the total and actual 
electrical load from (and to) the battery. The ammeter is providing 
misleading information. The loadmeter was proposed by the STC holder as 
a solution and as a means to keep the disturbance to existing wiring to 
a minimum. If the commenter wants to use an ammeter in lieu of a 
loadmeter, he/she may submit the appropriate information and apply for 
an alternative method of compliance (AMOC), as specified in paragraph 
(c) of the AD. The final rule will not change as a result of this 
comment.

Comment No. 4: Over-Voltage Protection

    Two commenters agree with the proposal and state that addressing 
over-voltage protection is a necessity for the voltage regulator.

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 
the change in compliance time and minor editorial corrections. The FAA 
has determined that the compliance time change and the 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 17 airplanes in the U.S. registry will be 
affected by this AD, that it will take approximately 20 workhours per 
airplane to accomplish this action, and that the average labor rate is 
approximately $60 an hour. Parts cost approximately $2,000 per 
airplane. Based on these figures, the total cost impact of this AD on 
U.S. operators is estimated to be $54,400, or $3,200 per airplane.

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:

98-18-08 Bombardier Inc. (formerly deHavilland, Inc.): Amendment 39-
10724; Docket No. 97-CE-120-AD

    Applicability: Model (Otter) DHC-3 airplanes, all serial 
numbers, certificated in any category, that have been modified by 
A.M. Luton Supplemental Type Certificate (STC) No. SA3777NM.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision that has the applicable STC 
incorporated, 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.

    Compliance: Required within the next 14 calendar months after 
the effective date of this AD, unless already accomplished.
    To prevent electrical system failure caused by inadequate 
electrical system requirements, which could result in the loss of 
the engine instruments or a possible electrical fire in the 
airplane's cockpit, accomplished the following:
    (a) Replace the voltage regulator and the voltage-ammeter gauge, 
and modify the auxiliary bus systems in accordance with A.M. Luton 
Electrical System Schematic, Drawing 20075, Rev. G and E, Sheets 1, 
2, and 3, dated May 15, 1998, which is referenced in A.M. Luton 
Service Information Letter No. SA-SIL-98-11-03, ``Electrical 
Systems'', Revision A, dated May 15, 1998.

[[Page 45684]]

    (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, Seattle Aircraft Certification Office 
(ACO), FAA, 1601 Lind Avenue, SW, Renton, Washington 98055-4056. The 
request shall be forwarded through an appropriate FAA Maintenance 
Inspector, who may add comments and then send it to the Manager, 
Seattle ACO.

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

    (d) Questions or technical information related to A.M. Luton 
Electrical Systems Schematic, Drawing 20075, Rev. G and E, Sheets 1, 
2, and 3, dated May 15, 1998, and A.M. Luton Service Information 
Letter No. SA-SIL-98-11-03, ``Electrical Systems'', Revision A, 
dated May 15, 1998, should be directed to A.M. Luton, 3025 Eldridge 
Ave., Bellingham, WA 98226; telephone: (360) 671-7817, facsimile: 
(360) 671-7820. 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.
    (e) The replacements and modifications required by this AD shall 
be done in accordance with A.M. Luton Electrical System Schematic, 
Drawing 20075, Rev. G. and E, Sheets 1, 2, and 3, dated May 15, 
1998, which is referenced in A.M. Luton Service Information Letter 
No. SA-SIL-98-11-03, ``Electrical Systems'', Revision A, dated May 
15, 1998. 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 A.M. Luton, 3025 
Eldridge Ave., Bellingham, WA 98226. 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.
    (f) This amendment becomes effective on October 10, 1998.

    Issued in Kansas City, Missouri, on August 18, 1998.
James E. Jackson,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-22824 Filed 8-26-98; 8:45 am]
BILLING CODE 4910-13-U

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