[Federal Register Volume 62, Number 62 (Tuesday, April 1, 1997)]
[Proposed Rules]
[Pages 15443-15446]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-8252]


-----------------------------------------------------------------------


DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 91-CE-87-AD]
RIN 2120-AA64


Airworthiness Directives; De Havilland DHC-6 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); Reopening of 
the comment period.

-----------------------------------------------------------------------

SUMMARY: This document proposes to revise an earlier proposed 
airworthiness directive (AD), which would have superseded AD 80-13-11 
R2. That AD currently requires repetitively inspecting the elevator, 
flap, aileron, and rudder control rods for cracks on certain de 
Havilland DHC-6 series airplanes, replacing any cracked rod, and 
installing rod sleeves. The previous document would have required 
replacing the elevator trim and elevator/flap interconnect rods, the 
aileron control rods, the elevator control rods, and the rudder control 
rods with parts of improved design, and repetitively inspecting these 
rods thereafter at certain intervals. These replacements would reduce 
the need for the number of repetitions of the inspections currently 
required by AD 80-13-11 R2. The Federal Aviation Administration (FAA) 
has determined that the flap control rods should also be replaced with 
parts of improved design as terminating action for repetitive 
inspections currently required by AD 80-03-08. The proposed action 
would supersede both AD 80-13-11 R2 and AD 80-03-08 and would require 
the replacements as terminating action to the repetitive inspections 
currently required. The proposed action is part of the FAA's policy on 
commuter class aircraft, which briefly states that, when a modification 
exists that could eliminate or reduce the number of required critical 
inspections, the modification should be incorporated. The actions 
specified by the proposed AD are intended to prevent cracking of these 
control rods, which, if not detected and corrected, could result in 
loss of control of the airplane.

DATES: Comments must be received on or before June 13, 1997.

ADDRESSES: Submit comments in triplicate to the FAA, Central Region, 
Office of the Assistant Chief Counsel, Attention: Rules Docket No. 91-
CE-87-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-87-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of Supplemental NPRM

    Any person may obtain a copy of this supplemental NPRM by 
submitting a request to the FAA, Central Region, Office of the 
Assistant Chief Counsel, Attention: Rules Docket No. 91-CE-87-AD, Room 
1558, 601 E. 12th Street, Kansas City, Missouri 64106.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an AD that would apply to certain de Havilland 
DHC-6 series airplanes was published in the Federal Register as a 
notice of proposed rulemaking (NPRM) on October 12, 1993 (58 FR 52714). 
The NPRM proposed to supersede AD 80-13-11 R2 with a new AD that would 
(1) require replacing elevator trim and elevator/flap interconnect 
rods, and the flap, aileron, elevator, and rudder control rods with 
parts of improved design; and (2) retain the aileron control rod 
inspections currently required by AD 80-13-11 R2, but reduce the number 
of repetitions of these inspections. Accomplishment of the proposed 
replacement as specified in the NPRM would be in accordance with de 
Havilland Service Bulletin (SB) No. 6/502, dated March 24, 1989. 
Accomplishment of the proposed inspections as specified in the NPRM 
would be in accordance with de Havilland SB No. 6/390, Revision E, 
dated December 20, 1991.
    Interested persons have been afforded an opportunity to participate 
in the making of this AD. No comments were received on the NPRM or on 
the FAA's determination of the cost on the public.

The FAA's Aging Commuter-Class Aircraft Policy

    The actions specified in the NPRM are part of the FAA's aging 
commuter class aircraft policy, which briefly states that, when a 
modification exists that could eliminate or reduce the number of 
required critical inspections, the modification should be incorporated. 
This policy is based on the FAA's determination that reliance on 
critical repetitive inspections on aging commuter-class airplanes 
carries an unnecessary safety risk when a design

[[Page 15444]]

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.

Events Leading to the Issuance of This Supplemental NPRM

    Since issuing the NPRM, the FAA has determined that AD 80-03-08 is 
also one that should be superseded by this action to coincide with the 
FAA's aging commuter aircraft policy. AD 80-03-08 currently requires 
repetitively inspecting the flap control rods on de Havilland DHC-6 
series airplanes. De Havilland SB No. 6/502 also specifies procedures 
for replacing the flap control rods with parts of improved design. The 
FAA has determined that when these replacements are incorporated, the 
number of repetitive inspections of these control rods can be reduced.
    After reviewing all information related to the events leading to 
this supplemental NPRM, the FAA has determined that (1) the flap 
control rod replacements should be added to the document; and (2) AD 
action should be taken to prevent cracking of the elevator trim and 
elevator/flap interconnect rods, the aileron control rods, the elevator 
control rods, the rudder control rods, and the flap control rods. If 
not detected and corrected, a cracked control rod could result in loss 
of control of the airplane.

Explanation of the Provisions of the Proposed AD

    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 both AD 80-13-11 R2 
and AD 80-03-08 with a new AD that would (1) require replacing 
elevator, flap, aileron, and rudder control rods and elevator trim and 
elevator flap/interconnect control rods with improved parts; and (2) 
retain the aileron control rod inspections currently required by AD 80-
13-11 R2, but reduce the number of repetitions of these inspections. 
Accomplishment of the proposed replacements would be in accordance with 
de Havilland SB No. 6/502, dated March 24, 1989. Accomplishment of the 
proposed inspections would be in accordance with de Havilland SB No. 6/
390, Revision E, dated December 20, 1991, and de Havilland SB No. 6/
388, Revision C, dated October 29, 1982.
    The FAA prepared a Regulatory Flexibility Determination and 
Analysis for the original proposal. This analysis was based on all 
owners/operators of de Havilland DHC-6 airplanes replacing all control 
rods specified in de Havilland SB No. 6/502. Because the replacement 
flap control rods that the FAA is adding to the proposal are already 
included in de Havilland SB No. 6/502, there is no need to accomplish a 
separate Regulatory Flexibility Determination and Analysis. The FAA is 
reprinting the synopsis of this analysis in this document.

Cost Impact

    The FAA estimates that 169 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 20 
workhours (4 workhours/ inspection and 16 workhours/replacement) per 
airplane to accomplish the proposed action, and that the average labor 
rate is approximately $60 an hour. Parts cost approximately $15,600 per 
airplane. Based on these figures, the total cost impact of the proposed 
AD on U.S. operators is estimated to be $2,839,200.
    AD 80-13-11 R2 and AD 80-03-08, which would both be superseded by 
the proposed action, currently require inspecting these control rod 
assemblies. These inspections take approximately 32 workhours at an 
average cost of $60 per hour; approximately $1,920 per airplane or 
$324,480 for the entire fleet. The inspection procedures of the 
proposed AD would be less costly and less frequent than those required 
by AD 80-13-11 R2 and AD 80-03-08.
    With the above figures in mind, including the costs for the 
modification proposed by this action, the proposed AD would cost an 
additional $14,880 per airplane over that already required by AD 80-13-
11 R2 and AD 80-03-08, or a total additional fleet cost of $2,524,860. 
These figures do not account for the recurring costs through the 
repetitive inspection requirement of AD 80-13-11 R2 and AD 80-03-08, 
and the proposed AD. The proposed AD would only require repetitive 
inspections every 2,400 hours time-in-service (TIS) after the control 
rod assembly is replaced, where AD 80-13-11 R2 currently requires 
repetitive inspections every 800 hours TIS and AD 80-03-08 requires 
repetitive inspections every 200 hours TIS.
    The incremental costs of the proposed AD would depend on the 
remaining service life of a DHC-6 airplane and its utilization, i.e., 
the number of hours TIS per year. The proposed AD would provide a cost 
savings over that already required to most owner/operators of de 
Havilland DHC-6 airplanes. The following examines the incremental costs 
to owners of de Havilland DHC-6 series airplanes with remaining service 
lives of 10, 20, and 30 years if the airplanes are utilized between 100 
and 2,500 hours TIS annually.
    The proposed AD would provide a cost savings at a service life of 
10 years for operators utilizing their airplanes less than 135 hours 
TIS or more than 1,000 hours TIS annually, and would provide a cost 
savings at service lives of 20 and 30 years for all de Havilland DHC-6 
series airplanes, regardless of airplane usage. The savings resulting 
from the less frequent inspections more than offset the costs of 
replacing the control rods. The cost savings would be at least $2,800 
at an average 20-year remaining service life and utilizing a 7 percent 
interest rate. For a 30-year remaining service life, the operator 
should realize a cost savings of at least $6,000 (with a 7 percent 
interest rate).
    De Havilland DHC-6 series airplanes that are utilized between 135 
and 1,000 hours TIS annually may not see a cost savings when replacing 
the control rods based upon a 10-year remaining service life. Before 
issuing this supplemental notice of proposed rulemaking, the FAA took 
into account that the costs of replacing the rods could be greater than 
the savings from the inspections required by the proposed AD for 
operators utilizing their airplanes within this range.

The Proposed AD's Impact Utilizing the FAA's Aging Commuter Class 
Aircraft Policy

    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 by 14 different 
operators. A significant number of the remaining 50 percent are 
operated in other forms of air transportation such as air cargo and air 
taxi.
    The proposed AD allows 500 hours time-in-service (TIS) before 
accomplishment of the design modification would become mandatory. The 
average utilization of the fleet for those airplanes in commercial 
commuter service is approximately 25 to 50 hours TIS per week. Based on

[[Page 15445]]

these figures, operators of commuter-class airplanes involved in 
commercial operation would have to accomplish the proposed modification 
within two to five calendar months after the proposed AD would become 
effective. Based on these scheduled operation figures, repetitive 
inspections for the proposed AD for operators who had accomplished the 
modification would be required approximately every one to two years. 
For private owners, who typically operate between 100 to 200 hours TIS 
per year, this would allow two to five years before the proposed 
modification would be mandatory. Based on these nonscheduled operation 
figures, repetitive inspections for the proposed AD for operators who 
had accomplished the modification would be required approximately every 
12 to 24 years.

Regulatory Flexibility Determination and Analysis

    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 the proposed rule, or any 
number of small entities subject to the rule which is substantial in 
the judgment of the rulemaking official. A ``significant economic 
impact'' is defined as 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 nine aircraft owned and the 
annualized cost threshold at $65,300 for scheduled operators and $5,000 
for unscheduled operators.
    The 169 U.S.-registered airplanes affected by the proposed AD are 
owned according to the following breakdown: 13 by individuals, 8 by 
U.S. government agencies, and 148 by businesses or not-for-profit 
enterprises. Of the 148 entities, one owns 26 airplanes, one owns 11 
airplanes, nineteen own between 2 and 9 airplanes, and fifty own 1 
airplane each.
    The FAA cannot determine the sizes of all the 148 owner entities 
nor the relative significance of the costs or cost savings estimated 
above. However, more than one-third of these entities operate de 
Havilland DHC-6 series airplanes in scheduled service. According to 
statistics obtained by the FAA, these airplane operators in scheduled 
service utilize the affected airplanes an average of 1,383 hours TIS 
annually, and general aviation operators utilize their airplanes an 
average of 706 hours TIS annually. These figures may have a standard of 
error of 14.4 percent and the general aviation average may include some 
airplanes in commuter service. The FAA cannot reasonably estimate the 
distribution of these hours among the de Havilland DHC-6 fleet.
    Because of these uncertainties, no cost thresholds for significant 
economic impact can be reasonably determined. The FAA solicits comments 
concerning the impact of this proposed AD on small entity owners of the 
affected airplanes. Based on the possibility that this proposed AD 
could have a significant impact on a substantial number of small 
entities, the FAA conducted a Regulatory Flexibility Determination and 
Analysis. A copy of this analysis may be obtained by contacting the 
Rules Docket at the location provided under the caption ADDRESSES.

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 USC 106(g), 40113, 44701.

Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing both AD 80-13-11 R2, 
Amendment 39-4703, and AD 80-03-08, Amendment 39-3682, and by adding 
the following new AD:

De Havilland: Docket No. 91-CE-87-AD. Supersedes AD 80-13-11 R2, 
Amendment 39-4703, and AD 80-03-08, Amendment 39-3682.

    Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-
300 airplanes (all serial numbers), certificated in any category.

    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 request approval for an 
alternative method of compliance in accordance with paragraph (d) 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 as indicated, unless already accomplished.
    To prevent loss of control of the airplane caused by cracked 
elevator, flap, aileron, elevator trim, elevator/flap interconnect, 
and rudder control rods, accomplish the following:
    (a) Within the next 500 hours time-in-service
    (TIS) after the effective date of this AD, replace the following 
2024-T3 or 2024-T81 control rods with 6061-T6 control rods in 
accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de 
Havilland Service Bulletin (SB) No. 6/502, dated March 24, 1989:
    (1) Flap Control Rods: Modification No. 6/1781;

[[Page 15446]]

    (2) Elevator Trim and Elevator/Flap Interconnect Control Rods: 
Modification No. 6/1785;
    (3) Aileron Control Rods: Modification No. 6/1791;
    (4) Elevator Control Rods: Modification No. 6/1792; and
    (5) Rudder Control Rods; Modification No. 6/1802.

    Note 2: The specific part numbers of the 2024-T3 or 2024-T81 
control and interconnect control rods and their 6061-T6 replacement 
part numbers are contained in de Havilland SB No. 6/502, dated March 
24, 1989.

    (b) Within 2,400 hours TIS after the replacement required by 
paragraph (a) of this AD, and thereafter at intervals not to exceed 
2,400 hours TIS, inspect all the affected control rods for cracks in 
accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de 
Havilland SB No. 6/390, Revision E, dated December 20, 1991; or de 
Havilland SB No. 6/388, Revision C, dated October 29, 1982, as 
applicable. Prior to further flight, replace any cracked rod with a 
new 6061-T6 rod as specified in and in accordance with the 
ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 6/502, 
dated March 24, 1989.
    (c) 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.
    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an equivalent level of safety may be 
approved by the Manager, New York Aircraft Certification Office 
(ACO), 10 Fifth Street, 3rd Floor, Valley Stream, New York 11581. 
The request shall be forwarded through an FAA Maintenance Inspector, 
who may add comments and then send it to the Manager, New York 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.

    (e) All persons affected by this directive may obtain copies of 
the documents referred to herein upon request to de Havilland, Inc., 
123 Garratt Boulevard, Downsview, Ontario, Canada, M3K 1Y5; or may 
examine these documents at the FAA, Central Region, Office of the 
Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, 
Missouri 64106.
    (f) This amendment supersedes AD 80-13-11 R2, Amendment 39-4703, 
and AD 80-03-08, Amendment 39-3682.

    Issued in Kansas City, Missouri, on March 26, 1997.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 97-8252 Filed 3-31-97; 8:45 am]
BILLING CODE 4910-13-U