[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: 94-26878]


[[Page Unknown]]

[Federal Register: October 31, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 91-CE-22-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) 81-10-11, which currently requires repetitively inspecting the 
elevator root ribs for cracks on 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 modifying the elevator root rib as 
terminating action for the repetitive inspections that are currently 
required by AD 81-10-11. The actions specified in the proposed AD are 
intended to prevent failure of the elevator root rib, which could 
result in loss of control of the airplane.

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

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 91-CE-22-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, M3K 1Y5. 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-22-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-22-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) de Havilland; (2) the Regional Airlines Association 
(RAA); and (3) several operators of the affected airplanes.
    From this review, the FAA has identified AD 81-10- 11, Amendment 
39-4112, as one that should be superseded with a new AD that would 
require a modification that could eliminate the need for short-interval 
and critical repetitive inspections. AD 81-10-11 currently requires 
repetitively inspecting the elevator root rib for cracks on certain de 
Havilland DHC-6 series airplanes, and replacing any cracked part.
    De Havilland has issued Service Bulletin (SB) No. 6/399, Revision 
E, dated May 25, 1984, which specifies procedures for (1) inspecting 
the elevator root rib; and (2) modifying the elevator root rib 
(Modification No. 6/1769). Modification No. 6/1769 consists of pulling 
back the elevator skins, removing the torque tube assembly, replacing 
the root rib assembly and doubler, replacing the second outboard nose 
rib, installing a new intercostal, and reinstalling the torque tube 
assembly and new skin.
    This airplane model is manufactured in Canada and is 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, 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, the FAA has determined that AD 
action should be taken to eliminate the repetitive short-interval 
inspections required by AD 81-10-11, and to prevent failure of the 
elevator root rib, which could result in loss of control of the 
airplane.
    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 that do not have Modification No. 6/1769 incorporated, 
the proposed AD would supersede AD 81-10-11 with a new AD that would 
(1) retain the current requirement of inspecting the elevator root rib 
for cracks, and replacing any cracked part; and (2) require modifying 
the elevator root rib (Modification 6/1769) as terminating action for 
the repetitive inspections. The proposed actions would be accomplished 
in accordance with de Havilland SB No. 6/399, Revision E, dated May 25, 
1984.
    The FAA estimates that 169 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 54 
workhours per airplane to accomplish the proposed action, and that the 
average labor rate is approximately $60 an hour. Parts cost 
approximately $4,200 per airplane. Based on these figures, the total 
cost impact of the proposed AD on U.S. operators is estimated to be 
$1,257,360. This figure is based upon the assumption that none of the 
affected airplane owners/operators have incorporated Modification 6/
1769.
    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 169 airplanes in the U.S. registry that would be 
affected by the proposed AD, the FAA has determined that approximately 
50 percent are operated in scheduled passenger service. A significant 
number of the remaining 50 percent are operated in other forms of air 
transportation such as air cargo and air taxi.
    The following paragraphs present cost scenarios for airplanes where 
no cracks were found and where cracks were found, utilizing an average 
remaining airplane life of 15 years and an average annual utilization 
rate of 1,600 hours TIS. De Havilland Models DHC-6-100 and DHC-6-200 
airplanes have probably already accumulated 15,000 hours TIS; 
therefore, those airplanes would have 100 hours TIS after the effective 
date of the AD to incorporate Modification 6/1769. Some Model DHC-6-300 
airplanes have not yet accumulated 15,000 hours TIS. This analysis is 
based upon the assumption that these airplanes yet to accumulate 15,000 
hours TIS have 10,000 hours TIS if operated in scheduled service and 
5,000 hours TIS if operated in general aviation. 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-22-AD, Room 
1558, 601 E. 12th Street, Kansas City, Missouri.
     No Cracks Scenario for Models DHC-6-100 and DHC-6-200: 
These airplanes would be inspected at 50 hours TIS after the effective 
date and modified within 100 hours TIS after the effective date. The 
incremental present value cost of the proposed AD over that required by 
AD 81-10-11 is $5,919 for an airplane utilized in sheduled service, and 
$6,642 for an airplane utilized in general aviation.
     No Cracks Scenario for Model DHC-6-300 Airplanes: These 
airplanes would be inspected at 50 hours TIS after the effective date 
and thereafter at 600-hour TIS intervals until the elevator root rib is 
replaced upon the accumulation of 15,000 hours TIS. The incremental 
present value cost of the proposed AD over that required by AD 81-10-11 
is $4,962 for an airplane utilized in sheduled service, and $3,099 for 
an airplane utilized in general aviation.
    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 169 U.S.-registered airplanes affected by the proposed AD, 6 
airplanes are owned by the federal government. Of the other 163, one 
business owns 26 airplanes, two businesses own 9 airplanes each, one 
business owns 8 airplanes, one business owns 7 airplanes, one business 
owns 5 airplanes, four businesses own 3 airplanes each, sixteen 
businesses own 2 airplanes each, and fifty-five businesses own 1 
airplane each.
    Because the FAA has no readily available means of obtaining data on 
the 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 proposed AD could have a 
significant impact on a substantial number of small entities. Because 
of this, the FAA conducted a regulatory flexibility analysis. A copy of 
this analysis may be obtained by contacting the Rules Docket at the 
location provided under the caption ADDRESSES.
    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, may 
have a significant economic impact on a substantial number of small 
entities. The FAA has conducted an Initial Regulatory Flexibility 
Determination and Analysis and has considered alternatives to this 
proposal that could minimize the impact on small entities. A copy of 
this analysis may be obtained by contacting the Rules Docket at the 
location provided under the caption ADDRESSES. After careful 
consideration, the FAA has determined that the proposed action is the 
best course to achieve the safety objective of returning the airplane 
to its original certification level of safety.
    Alternative actions and views are solicited from interested persons 
and will be considered by the FAA in the development of the final rule.

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 81-10-11, Amendment 39-
4112, and adding a new AD to read as follows:

De Havilland: Docket No. 91-CE-22-AD. Supersedes AD 81-10-11, 
Amendment 39-4112.

    Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-
300 airplanes (all serial numbers), certificated in any category, 
that do not have Modification No. 6/1769 incorporated.
    Compliance: Required as indicated in the body of the AD, unless 
already accomplished.
    To prevent failure of the elevator root rib, which could result 
in loss of control of the airplane, accomplish the following:
    (a) Within the next 50 hours time-in-service (TIS) after the 
effective date of this AD, unless already accomplished (compliance 
with AD 81-10-11), inspect the elevator root rib, part number (P/N) 
C6TE1022, for cracks in accordance with the ACCOMPLISHMENT 
INSTRUCTIONS section of de Havilland Service Bulletin (SB) No. 6/
399, Revision E, dated May 25, 1984.
    (1) If any crack is found, prior to further flight, accomplish 
one of the following:
    (i) Replace the cracked part with an airworthy part and 
reinspect thereafter at intervals not to exceed 600 hours TIS until 
the modification required in paragraph (b) of this AD is 
incorporated; or
    (ii) Incorporate Modification 6/1769 in accordance with the 
ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 6/399, 
Revision E, dated May 25, 1984.

    Note 1: Modification 6/1769 consists of pulling back the 
elevator skins, removing the torque tube assembly, replacing the 
root rib assembly and doubler, replacing the second outboard nose 
rib, installing a new intercostal, and reinstalling the torque tube 
assembly and new skin.

    (2) If no cracks are found, reinspect thereafter at intervals 
not to exceed 600 hours TIS until the modification required in 
paragraph (b) of this AD is incorporated.
    (b) Upon the accumulation of 15,000 hours TIS or within the next 
100 hours TIS after the effective date of this AD, whichever occurs 
later, unless already accomplished in accordance with paragraph 
(a)(1)(ii) of this AD, incorporate Modification 6/1769 in accordance 
with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 
6/399, Revision E, dated May 25, 1984.
    (c) Incorporating Modification 6/1769 as specified in paragraphs 
(a)(1)(ii) and (b) of this AD is considered terminating action for 
the inspection requirement 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 2: 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.
    (g) This amendment supersedes AD 81-10-11, Amendment 39-4112.

    Issued in Kansas City, Missouri, on October 25, 1994.
John R. Colomy,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-26878 Filed 10-28-94; 8:45 am]
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