[Federal Register Volume 60, Number 155 (Friday, August 11, 1995)]
[Proposed Rules]
[Pages 41029-41033]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-19917]
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[[Page 41030]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 91-CE-45-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) 78-26-02, which currently requires repetitively inspecting the
fuselage side frame flanges at Fuselage Station (FS) 218.125 and FS
219.525 for cracks on certain de Havilland DHC-6 series airplanes, and
repairing or 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 fuselage side frames at the referenced FS areas as
terminating action for the repetitive inspections that are currently
required by AD 78-26-02. The actions specified in the proposed AD are
intended to prevent failure of the fuselage because of cracks in the
fuselage side frames, which, if not detected and corrected, could
result in loss of control of the airplane.
DATES: Comments must be received on or before October 16, 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-45-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, 10 Fifth Street, 3rd Floor,
Valley Stream, New York 11581; telephone (516) 256-7523; facsimile
(516) 568- 2716.
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-45-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-45-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 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 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 78-26-02, Amendment 39-
3370, 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 78-26-02 currently requires
repetitively inspecting the fuselage side frame flanges at Fuselage
Station (FS) 218.125 and FS 219.525 on certain de Havilland DHC-6
series airplanes, and repairing or replacing any cracked part.
De Havilland Service Bulletin (SB) No. 6/371, dated June 2, 1978,
specifies procedures for inspecting, repairing, and modifying
(Modification Nos. 6/1461 and 6/1462) the fuselage side frame flanges
at FS 218.125 and FS 219.525. Modification No. 6/1461 introduces
fuselage side frames manufactured from material having improved stress
corrosion properties at FS 218.125, and Modification No. 6/1462
introduces fuselage side frames of this material at FS 219.525.
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 bilateral airworthiness agreement between the United States and
Canada. 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 78-26-02, Amendment 39-3370, and to prevent
failure of the fuselage because of cracks in the fuselage side frames,
which, if not detected and corrected, 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 without Modification Nos. 6/1461 and 6/1462
incorporated, the proposed AD
[[Page 41031]]
would supersede AD 78-26-02 with a new AD that would (1) retain the
current requirement of repetitively inspecting the fuselage side frame
flanges at FS 218.125 and FS 219.525, as applicable, and repairing or
replacing any cracked part; and (2) require modifying the fuselage side
frame flanges in the referenced FS areas (Modification Nos. 6/1461 and
6/1462) as terminating action for the repetitive inspections.
Accomplishment of the proposed actions would be in accordance with de
Havilland SB No. 6/371, dated June 2, 1978.
The FAA estimates that 94 airplanes in the U.S. registry would be
affected by the proposed AD, that it would take approximately 300
workhours per airplane to accomplish the proposed modification, and
that the average labor rate is approximately $60 an hour. Parts cost
approximately $16,200 (average) per airplane. Based on these figures,
the total cost impact of the proposed modification on U.S. operators is
estimated to be $3,214,800 or $34,200 per airplane. This cost figure is
based upon the assumption that none of the affected airplane owners/
operators have incorporated Modification Nos. 6/1461 and 6/1462.
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 94 airplanes in the U.S. registry that would be
affected by the proposed AD, the FAA has determined that approximately
45 percent are operated in scheduled passenger service. A significant
number of the remaining 55 percent are operated in other forms of air
transportation such as air cargo and air taxi.
The proposed AD allows 4,800 hours time-in-service (TIS) after the
proposed AD would become effective 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 24 to 48 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 24 to
48 years before the proposed modification would be mandatory.
The following paragraphs present cost scenarios for airplanes where
no cracks were found and where cracks were found during the
inspections, and where the remaining airplane life is 15 years with 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-45-AD, Room
1558, 601 E. 12th Street, Kansas City, Missouri.
No Cracks Scenario: Under the provisions of AD 78-26-02,
an owner/operator of an affected de Havilland DHC-6 series airplane in
scheduled service who operates an average of 1,600 hours TIS annually
would inspect every 400 hours TIS. This would amount to a remaining
airplane life (estimated 15 years) cost of $18,420; this figure is
based on the assumption that no cracks are found during the
inspections. The proposed AD would incur the same inspections except at
600-hour TIS intervals until 4,800 hours TIS after the proposed AD
would become effective where the operator would have to replace the
fuselage side frame flanges (eliminating the need for further
repetitive inspections), which would result in a present value cost of
$31,433. The incremental cost of the proposed AD for such an airplane
would be $13,013 or $4,959 annualized over the three years it would
take to accumulate 4,800 hours TIS. An owner of a general aviation
airplane who operates 800 hours TIS annually without finding any cracks
during the 600-hour TIS inspections would incur a present value
incremental cost of $7,598. This would amount to a per year amount of
$1,594 over the six years it would take to accumulate 4,800 hours TIS.
Limited Cracking Found Scenario: Under the provisions of
AD 78-26-02, an owner/operator of an affected de Havilland DHC-6 series
airplane who found limited cracking (as defined in SB No. 6/371) during
an inspection would have to inspect each 300 hours TIS or 45 days,
whichever occurs first, and replace the part within 360 days after
finding the cracking. The proposed AD would require inspections every
300 hours TIS, and then require replacement at 4,800 hours TIS after
the proposed AD would become effective. This would result in a present
value total cost of $34,908 per airplane in scheduled service, which
would make immediate replacement more economical ($32,400) than
repetitively inspecting. With this scenario, the proposed AD would
result in an incremental present value cost savings over that required
in AD 78-26-02 of $1,491 per airplane in scheduled service (or $568
annualized over 3 years) and $6,517 ($1,367 annualized over 6 years)
for airplanes operating in general aviation service.
Excessive cracking scenario: AD 78-26-02 requires
repairing or replacing the fuselage side frames if excessive cracking
is found (as defined by SB No. 6/371), as would the proposed AD. The
difference is that AD 78-26-02 requires immediate crack repair and then
replacement within 360 days after finding the crack, and the proposed
AD would require immediate repair and mandatory replacement of the
fuselage side frames within 4,800 hours TIS after the proposed AD would
become effective. This would result in a present value total cost of
$34,709 per airplane in scheduled service, which would make immediate
replacement more economical ($32,400) than repetitively inspecting.
With this scenario, the proposed AD would average a present value cost
savings over that required in AD 78-26-02 of $2,083 ($794 annualized
over 3 years) for each airplane operated in scheduled service, and
$6,607 ($1,386 annualized over 6 years) for each airplane operated in
general aviation service.
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 $5,000 for unscheduled
operators.
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Of the 94 U.S.-registered airplanes affected by the proposed AD, 4
airplanes are owned by the federal government. Of the other 90, one
business owns 26 airplanes, two businesses own 7 airplanes each, one
business owns 3 airplanes, seven businesses own 2 airplanes each, and
thirty-three businesses own 1 airplane each.
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 $5,000 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 33 entities owning two or
fewer airplanes would not experience a ``significant economic impact''
as defined by FAA Order 2100.14A. Since the remaining 11 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. 106(g), 40101, 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing AD 78-26-02, Amendment 39-
3370, and adding the following new AD to read as follows:
De Havilland: Docket No. 91-CE-45-AD. Supersedes AD 78-26-02,
Amendment 39-3370.
Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-
300 airplanes (serial numbers 1 through 411), certificated in any
category, that do not have Modification Nos. 6/1461 and 6/1462
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 use the authority
provided in paragraph (e) of this AD to request approval from the
FAA. This approval may address either no action, if the current
configuration eliminates the unsafe condition, or different actions
necessary to address the unsafe condition described in this AD. Such
a request should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless already accomplished.
To prevent failure of the fuselage because of cracks in the
fuselage side frames, which, if not detected and corrected, could
result in loss of control of the airplane, accomplish the following:
(a) Within the next 200 hours time-in-service (TIS) after the
effective date of this AD, unless already accomplished (compliance
with AD 78-26-02), and thereafter as indicated below, inspect the
fuselage side frames for cracks at Fuselage Station (FS) 218.125 and
FS 219.525, as applicable (see chart below) in accordance with the
Accomplishment Instructions section of de Havilland Service Bulletin
(SB) No. 6/371, dated June 2, 1978. Utilize the following chart to
determine which fuselage stations are affected:
------------------------------------------------------------------------
Fuselage
Modification 6/ stations
Serial Nos. 1553 affected (both
incorporated sides)
------------------------------------------------------------------------
1 through 395........................... No............ 218.125 and
219.525.
1 through 395........................... Yes........... 219.525 only.
396 through 411......................... N/A........... 219.525 only.
------------------------------------------------------------------------
Note 2: Modification 6/1553 incorporates fuselage side frames of
improved stress corrosion resistant material at FS 218.125.
(1) If cracks are found that exceed the limits specified in
Figure 3 of de Havilland SB No. 6/371, prior to further flight,
accomplish one of the following:
(i) Repair the cracks in accordance with the Accomplishment
Instructions: Repair: section of de Havilland SB No. 6/371, dated
June 2, 1978. Reinspect thereafter at intervals not to exceed 600
hours TIS until the modification specified in paragraph (b) of this
AD is incorporated; or
(ii) Replace the cracked fuselage side frame in accordance with
the Accomplishment Instructions: Replacement: section of de
Havilland SB No. 6/371, dated June 2, 1978. Reinspect any fuselage
side frame not replaced at intervals not to exceed 600 hours TIS
until the modification specified in paragraph (b) of this AD is
incorporated.
(2) If cracks are found that are within the limits specified in
Figure 3 of de Havilland SB No. 6/371, reinspect at intervals not to
exceed 300 hours TIS until the modification specified in paragraph
(b) of this AD is incorporated.
(3) If no cracks are found, reinspect thereafter at intervals
not to exceed 600 hours TIS until the modification specified in
paragraph (b) of this AD is incorporated.
(b) Within the next 4,800 TIS after the effective date of this
AD, incorporate Modification Nos. 6/1461 and 6/1462 in accordance
with the Accomplishment Instructions: Replacement: section of de
Havilland SB No. 6/371, dated June 2, 1978. This consists of
replacing all fuselage side frames required as specified in the
following chart:
------------------------------------------------------------------------
Fuselage
Modification 6/ stations
Serial Nos. 1553 affected (both
incorporated sides)
------------------------------------------------------------------------
1 through 395........................... No............ 218.125 and
219.525.
1 through 395........................... Yes........... 219.525 only.
396 through 411......................... N/A........... 219.525 only.
------------------------------------------------------------------------
(c) Incorporating Modification Nos. 6/1461 and 6/1462 as
specified in paragraph (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
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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, 10 Fifth Street, 3rd Floor, 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 Aircraft ACO.
Note 3: 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 78-26-02, Amendment 39-3370.
Issued in Kansas City, Missouri, on August 7, 1995.
Gerald W. Pierce,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-19917 Filed 8-10-95; 8:45 am]
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