[Federal Register Volume 59, Number 209 (Monday, October 31, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-26876]


[[Page Unknown]]

[Federal Register: October 31, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 91-CE-46-AD]

 

Airworthiness Directives; de Havilland DHC-6 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) 83-18-03, which currently requires repetitively inspecting the 
tailplane outboard hinge assembly for cracks on certain de Havilland 
DHC-6 series airplanes, and replacing any cracked part. The Federal 
Aviation Administration's policy on aging commuter-class aircraft is to 
eliminate, or in certain instances, reduce the number of certain 
repetitive short-interval inspections when improved parts or 
modifications are available. The proposed action would require 
eventually modifying the tailplane outboard hinge arm and tailplane 
hinge plate as terminating action for the currently required repetitive 
inspections. The actions specified in the proposed AD are intended to 
prevent tailplane failure caused by cracks in either the outboard hinge 
arm or the hinge plate.

DATES: Comments must be received on or before January 4, 1995.

ADDRESSES: Submit comments on the proposal in triplicate to the Federal 
Aviation Administration (FAA), Central Region, Office of the Assistant 
Chief Counsel, Attention: Rules Docket No. 91-CE-46-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 de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario, 
Canada, M3K1Y5. This information also may be examined at the Rules 
Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Jon Hjelm, Aerospace Engineer, FAA, 
New York Aircraft Certification Office, 181 South Franklin Avenue, Room 
202, Valley Stream, New York 11581; telephone (516) 791-6220; facsimile 
(516) 791-9024.

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. 91-CE-46-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. 91-CE-46-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    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 of the airplane if the known problem is not 
detected by the inspection; (2) the reliability of the inspection such 
as the probability of not detecting the known problem; (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. With this policy in 
mind, the FAA recently conducted a review of existing AD's that apply 
to de Havilland DHC-6 series airplanes. Assisting the FAA in this 
review were (1) Transport Canada, which is the airworthiness authority 
for Canada; (2) de Havilland, Inc.; (3) the Regional Airlines 
Association (RAA); and (4) several U.S. and foreign operators of the 
affected airplanes.
    From this review, the FAA has identified AD 83-18-03, Amendment 39-
1658, as one that should be superseded with a new AD that would 
eliminate short-interval and critical repetitive inspections. AD 83-18-
03 currently requires repetitively inspecting the tailplane outboard 
hinge assembly for cracks on certain de Havilland DHC-6 series 
airplanes, and replacing any cracked part.
    De Havilland, Inc. (formerly Boeing of Canada, Ltd.) has issued 
Service Bulletin (SB) No. 6/421, Revision B, dated November 11, 1983. 
This service bulletin specifies procedures for replacing the tailplane 
outboard hinge arm and tailplane hinge plate with parts of improved 
design. This replacement is known as Modification No. 6/1799.
    As a result of the previously discussed AD review, Transport Canada 
considers Modification 6/1799 mandatory and has issued Transport Canada 
AD CF-83-11 in order to assure the continued airworthiness of these 
airplanes in Canada.
    This airplane model is manufactured in Canada and is 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. Pursuant to this 
bilateral airworthiness agreement, Transport Canada has kept the FAA 
informed of the situation described above.
    Based on its aging commuter-class aircraft policy and after 
reviewing all available information including that received from 
Transport Canada, the FAA has determined that AD action should be taken 
to eventually eliminate the repetitive short-interval inspections 
required by AD 83-18-03, and to prevent tailplane failure caused by 
cracks in either the outboard hinge arm or the hinge plate.
    Since an unsafe condition has been identified that is likely to 
exist or develop in other de Havilland DHC-6 series airplanes of the 
same type design, the proposed AD would supersede AD 83-18-03 with a 
new AD that would (1) initially retain the requirement of repetitively 
inspecting the tailplane outboard hinge assembly for cracks, and 
replacing any cracked part; and (2) eventually require modifying the 
tailplane outboard hinge arm and tailplane hinge plate with parts of 
improved design (Modification No. 1799) as terminating action for the 
currently required repetitive inspections. The proposed actions would 
be accomplished in accordance with de Havilland SB No. 6/421, Revision 
B, dated November 11, 1983.
    The FAA estimates that 141 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 35 
workhours per airplane to accomplish the proposed action, and that the 
average labor rate is approximately $60 an hour. Parts cost 
approximately $4,400 per airplane. Based on these figures, the total 
cost impact of the proposed AD on U.S. operators is estimated to be 
$916,500. This figure is based on the assumption that no affected 
airplane owner/operator has accomplished the proposed action.
    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 141 airplanes in the U.S. registry that would be 
affected by the proposed AD, the FAA has determined that approximately 
40 percent are operated in scheduled passenger service. A significant 
number of the remaining 60 percent are operated in other forms of air 
transportation such as air cargo and air taxi.
    The proposed AD allows 2,400 hours time-in-service (TIS) 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 would have to accomplish the proposed modification within 12 
to 24 calendar months after the proposed AD would become effective. For 
private owners, who typically operate between 100 to 200 hours TIS per 
year, this would allow 12 to 24 years before the proposed modification 
would be mandatory.
    The following paragraphs present cost scenarios for airplanes where 
no cracks are found and where cracks are found, utilizing an average 
remaining airplane life of 15 years and an average annual utilization 
rate of 1,600 hours TIS. A copy of the full Cost Analysis and 
Regulatory Flexibility Determination for the proposed action may be 
examined at the FAA, Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 91-CE-46-AD, Room 1558, 601 E. 
12th Street, Kansas City, Missouri.
     No Cracks Scenario: Under the provisions of AD 83-18-03, 
an owner/operator of a de Havilland DHC-6 series airplane in scheduled 
service who operates an average of 1,600 hours TIS annually would 
inspect every 1,200 hours TIS. This would amount to a remaining 
airplane life (estimated 15 years) amount of $4,769; this figure is 
based on the assumption that no cracks are found during the 
inspections. The proposed AD would incur the same 1,200-hour TIS 
inspection until 2,400 hours TIS where the operator would have to 
replace the tailplane outboard hinge arm assembly (eliminating the need 
for further repetitive inspections), which would result in a present 
value cost of $6,574. The incremental cost of the proposed AD for such 
an airplane would be $1,805 ($6,574-$4,769) or $1,309 annualized over 
the 1.5 years it would take to accumulate 2,400 hours TIS. An owner of 
a general aviation airplane who operates 800 hours TIS annually without 
finding any cracks during the 1,200-hour TIS inspections would incur a 
present value incremental cost of $3,843 ($5,990-$2,507). This would 
amount to a per year amount of $1,327 over the three years it would 
take to accumulate 2,400 hours TIS.
     Cracks Found Scenario: Under the provisions of AD 83-18-
03, an owner/operator of a de Havilland DHC-6 series airplane who found 
cracks during an inspection would have to repair the crack prior to 
further flight and resume inspections every 1,200 hours TIS. The 
proposed AD would require immediate replacement of the arm assembly if 
cracks were found as terminating action for the repetitive inspection 
requirement. The repair cost is the same as the replacement except that 
the repair does not terminate the inspection requirement. For this 
reason, the proposed AD would result in present-day cost savings, which 
would continue to grow over the remaining life of the airplane since 
repetitive inspections would not be required. Using the assumed 15-year 
remaining life, the cost savings would be $4,409 for scheduled service 
airplane owners/operators and $2,149 for general aviation airplane 
owners/operators.
    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily or 
disproportionally burdened by government regulations. The RFA requires 
government agencies to determine whether rules would have a 
``significant economic impact on a substantial number of small 
entities,'' and, in cases where they would, conduct a Regulatory 
Flexibility Analysis in which alternatives to the rule are considered. 
FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance, 
outlines FAA procedures and criteria for complying with the RFA. Small 
entities are defined as small businesses and small not-for-profit 
organizations that are independently owned and operated or airports 
operated by small governmental jurisdictions. A ``substantial number'' 
is defined as a number that is not less than 11 and that is more than 
one-third of the small entities subject to a proposed rule, or any 
number of small entities judged to be substantial by the rulemaking 
official. A ``significant economic impact'' is defined by an annualized 
net compliance cost, adjusted for inflation, which is greater than a 
threshold cost level for defined entity types. FAA Order 2100.14A sets 
the size threshold for small entities operating aircraft for hire at 9 
aircraft owned and the annualized cost thresholds, adjusted to 1994 
dollars, at $69,000 for scheduled operators and $4,850 for unscheduled 
operators.
    Of the 141 U.S.-registered airplanes affected by the proposed AD, 6 
airplanes are owned by the federal government. Of the other 135, one 
business owns 26 airplanes, one business owns 9 airplanes, one business 
owns 8 airplanes, 1 business owns 7 airplanes, one business owns 4 
airplanes, two businesses own 3 airplanes each, thirteen business own 2 
airplanes each, and forty-nine businesses each own 1 airplane.
    Because the FAA has no readily available means of obtaining data on 
sizes of these entities, the economic analysis for the proposed AD 
utilizes the worst case scenario using the lower annualized cost 
threshold of $4,850 for operators in unscheduled service instead of 
$69,000 for operators in scheduled service. With this in mind and based 
on the above ownership distribution, the 64 entities owning 3 or fewer 
airplanes would not experience a ``significant economic impact'' as 
defined by FAA Order 2100.14A. Since the remaining five entities do not 
constitute a ``substantial number'' as defined in the Order, the 
proposed AD would not have a ``significant economic impact on a 
substantial number of small entities.''
    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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing AD 83-18-03, Amendment 39-
4719, and adding a new AD to read as follows:

De Havilland: Docket No. 91-CE-46-AD. Supersedes AD 83-18-03, 
Amendment 39-4719.

    Applicability:  Models DHC-6-1, DHC-6-100, DHC-6-200 and DHC-300 
airplanes (serial numbers 1 to 810), certificated in any category, 
that have not incorporated Modification 6/1799 in accordance with 
the ACCOMPLISHMENT INSTRUCTIONS, Replacement, section of de 
Havilland Service Bulletin (SB) No. 6/421, Revision B, dated 
November 11, 1983.
    Compliance: Required as indicated in the body of this AD, unless 
already accomplished.
    To prevent tailplane failure caused by cracks in either the 
outboard hinge arm or the hinge plate, accomplish the following:
    (a) Within the next 50 hours time-in-service (TIS) after the 
effective date of this AD or within the next 1,200 hours TIS after 
the last inspection accomplished in accordance with superseded AD 
83-18-03, Amendment 39-4719, whichever occurs later, inspect the 
tailplane outboard hinge arm assembly for cracks in accordance with 
the ACCOMPLISHMENT INSTRUCTIONS, Inspection, section of de Havilland 
SB No. 6/421, Revision B, dated November 11, 1983.
    (1) If cracks are not found, reinspect every 1,200 hours TIS 
until Modification 6/1799 (tailplane outboard hinge arm and 
tailplane hinge plate) is installed as required by paragraph (b) of 
this AD.
    (2) If cracks are found, prior to further flight, replace the 
tailplane outboard hinge arm assembly with Modification 6/1799 in 
accordance with the ACCOMPLISHMENT INSTRUCTIONS, Replacement, 
section of de Havilland SB No. 6/421, Revision B, dated November 11, 
1983.
    (b) Within 2,400 hours TIS after the effective date of this AD, 
replace the tailplane outboard hinge arm assembly with Modification 
6/1799 in accordance with the ACCOMPLISHMENT INSTRUCTIONS, 
Replacement, section of de Havilland SB No. 6/421, Revision B, dated 
November 11, 1983, unless already accomplished in accordance with 
paragraph (a)(2) of this AD.
    (c) Compliance with paragraph (a)(2) or (b) of this AD is 
considered terminating action for the inspection requirements of 
this AD.
    (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.
    (e) 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, New York Aircraft 
Certification Office (ACO), FAA, 181 South Franklin Avenue, Room 
202, Valley Stream, New York 11581. The request shall be forwarded 
through an appropriate FAA Maintenance Inspector, who may add 
comments and then send it to the Manager, New York ACO.

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

    (f) All persons affected by this directive may obtain copies of 
the document referred to herein upon request to de Havilland, Inc., 
123 Garratt Boulevard, Downsview, Ontario M3K 1Y5 Canada; 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.

    Issued in Kansas City, Missouri, on October 25, 1994.
John R. Colomy,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-26876 Filed 10-28-94; 8:45 am]
BILLING CODE 4910-13-P