[Federal Register Volume 61, Number 137 (Tuesday, July 16, 1996)]
[Proposed Rules]
[Pages 37019-37022]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-17983]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-72-AD]
RIN 2120-AA64


Airworthiness Directives; de Havilland Model DHC-8-100 and -300 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to all deHavilland DHC-8-100 
and -300 series airplanes, that currently requires repetitive 
inspections to detect loose bolts at the retract actuator support 
fitting of the main landing gear, and various follow-on actions, if 
necessary. That AD was prompted by a report of loose actuator 
supporting bolts and cracks in the relief radius of the boss at the 
forward surface of the fittings. This action would add a requirement to 
accomplish a new modification, which, when accomplished, would 
terminate the repetitive inspections. The actions specified by the 
proposed AD are intended to prevent loss of hydraulic systems and 
reduced controllability of the airplane due to loose actuator support 
bolts or cracks in the relief radius of the boss at the forward surface 
of the fittings.

DATES: Comments must be received by August 26, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-72-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, 
Garratt Boulevard, Downsview, Ontario, Canada M3K 1Y5. This information 
may be examined at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:
Jon Hjelm, Aerospace Engineer, Airframe and Propulsion Branch, ANE-173, 
FAA, New York Aircraft Certification Office, Engine and

[[Page 37020]]

Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New 
York 11581; telephone (516) 256-7523; fax (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 shall 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 summarizing 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 Number 95-NM-72-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, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 95-NM-72-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On September 12, 1991, the FAA issued AD 91-20-12, amendment 39-
8046 (56 FR 47901, September 23, 1991), applicable to all de Havilland 
Model DHC-8-100 and -300 series airplanes. That amendment superseded AD 
91-15-51, amendment 39-8016 (56 FR 41928, August 26, 1991), to add de 
Havilland Model DHC-8-300 series airplanes to the applicability; to 
require repetitive inspections to detect loose bolts at the retract 
actuator support fitting of the main landing gear (MLG); and, if 
necessary, to require a magnetic particle inspection, replacement of 
loose bolts, and replacement of cracked fittings. That action was 
prompted by a report of loose actuator supporting bolts and cracks in 
the relief radius of the boss at the forward surface of the fittings. 
The requirements of that AD are intended to prevent these conditions, 
which could result in loss of the hydraulic systems and reduced 
controllability of the airplane.
    In the preamble to AD 91-20-12, the FAA indicated that inspections 
of the MLG's were considered ``interim action'' and that further 
rulemaking action was being considered. As a follow-on action from that 
determination, the FAA is now proposing additional, final action.

Explanation of Relevant Service Information

    Since the issuance of AD 91-20-12, de Havilland has issued Service 
Bulletin S.B. 8-54-34, Revision `A', dated July 21, 1995, which 
describes procedures for modification of the frame and the retraction 
actuator fitting of the MLG. This modification involves removing the 
enamel application from the interface surfaces of the frame and 
fitting.
    This modification will allow the bracket to seat properly on the 
MLG frame and will prevent preload stress in the bracket.
    De Havilland has also issued Service Bulletin S.B. 8-54-27, 
Revision `B', dated August 22, 1994, which also describes procedures 
for modification of the frame and the retraction actuator fitting of 
the MLG. This modification involves installing modified brackets with 
improved fasteners. This modified bracket incorporates a material 
change to preclude hydrogen embrittlement cracking.
    Accomplishment of these modifications eliminates the need for the 
repetitive inspections.
    Transport Canada Aviation classified these service bulletins as 
mandatory and issued Canadian airworthiness directive CF-91-25R2 in 
order to assure the continued airworthiness of these airplanes in 
Canada.

FAA's Conclusions

    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, the Transport Canada Aviation has 
kept the FAA informed of the situation described above., The FAA has 
examined the findings of Transport Canada Aviation, reviewed all 
available information, and determined that AD action is necessary for 
products of this type design that are certificated for operation in the 
United States.

Explanation of the Requirements of the Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, the proposed AD would supersede AD 91-20-12. The 
proposed AD would continue to require repetitive inspections to detect 
loose bolts at the retract actuator support fitting of the MLG; and, if 
necessary, to require a magnetic particle inspection, replacement of 
loose bolts, and replacement of cracked fittings. In addition, this new 
proposed AD would require modification of the frame and the retraction 
actuator fitting of the MLG, which would constitute terminating action 
for the repetitive inspection requirements. The actions would be 
required to be accomplished in accordance with the service bulletins 
described previously.
    Operators should also note that the applicability of the proposed 
rule differs from the current applicability of AD 91-20-12. The 
proposed AD would limit the applicability to include only those 
airplanes having serial numbers 3 through 400 inclusive, except serial 
number 391. The FAA points out that, during production, Modifications 
8/1830 and 8/2049 were installed on Model DHC-8-100 and -300 series 
airplanes having serial number 400 and subsequent; therefore, these 
airplanes are not subject to the requirements of this AD.

Differences Between Proposed AD and Relevant Service Information

    Operators should note that, unlike the effectivity listing 
specified in de Havilland Service Bulletin 8-54-27, Revision `B', dated 
August 22, 1994, the proposed AD would require that the modification be 
accomplished on Model DHC-8-100 and -300 series airplanes, serial 
numbers 3 through 400 inclusive, except serial number 391. The FAA 
points out that de Havilland inadvertently excluded the serial numbers 
of some affected airplanes from the effectivity listing of its service 
bulletin.

Cost Impact

    There are approximately 125 de Havilland Model DHC-8-100 and -300 
series airplanes of U.S. registry that would be affected by this 
proposed AD.
    The actions that are currently required by AD 91-20-12, and 
retained in this proposed AD, take approximately

[[Page 37021]]

1 work hour per airplane to accomplish, at an average labor rate of $60 
per work hour. Based on these figures the cost impact on U.S. operators 
of the actions currently required is estimated to be $7,500, or $60 per 
airplane.
    The installation of modified brackets with new fasteners that would 
be required by this proposal would take approximately 10 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Required parts would cost approximately $3,500 per airplane. Based on 
these figures, the cost impact of the modification requirement of this 
proposal on U.S. operators is estimated to be $512,500 or $4,100 per 
airplane.
    The removal of the enamel application (Modification 8/1830) that 
would be required by this proposal would take approximately 5 work 
hours per airplane to accomplish, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact on U.S. operators of 
the proposed requirements of this AD is estimated to be $37,500, or 
$300 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.

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 proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the 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 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, 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), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-8046 (56 FR 
47901, September 23, 1991), and by adding a new airworthiness directive 
(AD), to read as follows:

De Havilland, Inc.: Docket 95-NM-72-AD, Supersedes AD 91-20-12, 
Amendment 39-8046.

    Applicability: Model DHC-8-100 and -300 series airplanes, serial 
numbers 3 through 400 inclusive, except serial number 391; 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 accomplished 
previously.
    To prevent loss of hydraulic systems and reduced controllability 
of the airplane due to loose actuator support bolt or cracks in the 
relief radius of the boss at the forward surface of the fittings, 
accomplish the following:
    (a) For Model DHC-8-100 series airplanes: Within 24 hours after 
September 9, 1991 (the effective date of AD 91-15-51, amendment 39-
8016), inspect the three actuator attachment fitting bolts on the 
right- and left-hand main landing gears (MLG) to detect loose bolts 
by applying a torque of not less than 10 foot-pounds to each bolt.
    (1) If no loose bolt is found as a result of the inspection 
required by paragraph (a) of this AD, repeat this inspection 
thereafter at intervals not to exceed 500 landings.
    (2) If any loose bolt is found as a result of the inspection 
required by paragraph (a) of this AD, accomplish paragraphs 
(a)(2)(i), (a)(2)(ii), and (a)(2)(iii) of this AD.
    (i) Prior to further flight, replace the loose bolt with a new 
bolt of the same part number.
    (ii) Within 250 landings after October 7, 1991 (the effective 
date of 91-20-12, amendment 39-8046) accomplish paragraphs 
(a)(2)(ii)(A) and (a)(2)(ii)(B) of this AD.
    (A) Remove the associated support fitting having part number (P/
N) 85410084.
    (B) Perform a magnetic particle inspection to detect cracks 
throughout the fitting, paying particular attention to the relief 
radius at the forward surface boss. If any crack is detected as a 
result of this inspection, prior to further flight, replace the 
fitting with a serviceable part.
    (iii) Repeat the inspection required by paragraph (a) of this AD 
thereafter at intervals not to exceed 500 landings.
    (b) For Model DHC-8-300 series airplanes: Within 250 landings 
after October 7, 1991 (the effective date of AD 91-20-12, amendment 
39-8046), inspect the three actuator attachment fitting bolts on the 
right- and left-hand MLG's to detect loose bolts by applying a 
torque of not less than 10 foot-pounds to each bolt.
    (1) If no loose bolt is found as a result of the inspection 
required by paragraph (b) of this AD, repeat this inspection 
thereafter at intervals not to exceed 500 landings.
    (2) If any loose bolt is found as a result of the inspection 
required by paragraph (a) of this AD, accomplish paragraphs 
(b)(2)(i), (b)(2)(ii), and (b)(2)(iii) of this AD.
    (i) Prior to further flight, replace the loose bolt with a new 
bolt of the same part number.
    (ii) Within 250 landings after October 7, 1991 (the effective 
date of AD 91-20-12, amendment 39-8046), accomplish (b)(2)(ii)(A) 
and (b)(2)(ii)(B) of this AD.
    (A) Remove the associated support fitting (P/N 85410084 for 
Model DHC-8-301 airplanes, and P/N 85411701 for Model DHC-8-311 
airplanes).
    (B) Perform a magnetic particle inspection to detect cracks 
throughout the fitting, pay particular attention to the relief 
radius at the forward surface boss. If any crack is detected as a 
result of this inspection, prior to further flight, replace the 
fitting with a serviceable part.
    (iii) Repeat the inspection required by paragraph (b) of this AD 
thereafter at intervals not to exceed 500 landings.
    (c) Within 90 days after the effective date of this AD, 
accomplish paragraphs (c)(1) and (c)(2), as applicable, of this AD. 
Accomplishment of this paragraph constitutes terminating action for 
the inspections required by paragraphs (a) and (b) of this AD.
    (1) For Model DHC-8-100 and -300 series airplanes, having serial 
numbers 3 through 400 inclusive, except serial number 391: Modify 
the frame and the retraction actuator fitting of the MLG, in 
accordance with de Havilland Service Bulletin S.B. 8-54-34, Revision 
`A', dated July 21, 1995.
    (2) For Model DHC-8-100 and -300 series airplanes, having serial 
number 3 through 332 inclusive: Modify the retraction actuator 
fitting of the MLG, in accordance with de Havilland Service Bulletin 
S.B. 8-54-27, Revision `B', dated August 22, 1994.
    (d) An alternative method of compliance or adjustment of the 
compliance time that

[[Page 37022]]

provides an acceptable level of safety may be used if approved by 
the Manager, New York Aircraft Certification Office (ACO), FAA, 
Engine and Propeller Directorate. Operators shall submit their 
requests through an appropriate FAA Principal 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 Standardization Branch ANM-113.

    (e) Special flight permits may be used in accordance with 
section 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. Any loose bolt 
found as a result of the inspections required by paragraph (a) or 
(b) of this AD, must be retorqued prior to application for a special 
flight permit. The upper bold, P/N 81812-7-22, must be retorqued to 
36-39 foot-pounds; the lower two bolts, P/N 81812-6-22, must be 
retorqued to 22-25 foot-pounds.

    Issued in Renton, Washington, on July 10, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-17983 Filed 7-15-96; 8:45 am]
BILLING CODE 4910-13-M