[Federal Register Volume 62, Number 52 (Tuesday, March 18, 1997)]
[Proposed Rules]
[Pages 12768-12771]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6718]


      
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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

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Federal Register / Vol. 62, No. 52 / Tuesday, March 18, 1997 / 
Proposed Rules

[[Page 12768]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-73-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 de Havilland Model DHC-
8-100 and -300 series airplanes, that currently requires an inspection 
to detect discrepancies and damage of the low fuel pressure switch 
adapter/snubber (located on each engine fuel heater), and replacement, 
if necessary. That AD also requires an inspection to detect gaps or 
openings in each nacelle and engine-mounted firewall area, and in 
certain weather seals in the nacelles; and correction of discrepancies. 
The proposed AD would require certain new modifications to the nacelles 
that will minimize the passage of flammable fluid through the zones of 
the nacelle of each engine. The actions specified by the proposed AD 
are intended to prevent the spread of fire through these zones in the 
event of an explosion during flight, and consequent structural damage 
to the airplane.

DATES: Comments must be received by April 25, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-73-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: Richard Fiesel, Aerospace Engineer, 
Airframe and Propulsion Branch, ANE-171, FAA, New York Aircraft 
Certification Office, Engine and Propeller Directorate, 10 Fifth 
Street, Third Floor, Valley Stream, New York 11581; telephone (516) 
256-7504; 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 96-NM-73-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. 96-NM-73-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On July 15, 1992, the FAA issued AD 92-13-11, amendment 39-8281 (57 
FR 37872, August 21, 1992), applicable to all de Havilland Model DHC-8-
100 and -300 series airplanes, which requires repetitive inspections to 
detect discrepancies of the low fuel pressure switch adapter/snubber 
(located on each engine fuel heater), and replacement of discrepant 
parts. The installation of de Havilland Modification 8/1208 is provided 
as an optional terminating action for these repetitive inspections. AD 
92-13-11 also requires an inspection for gaps and openings that could 
allow flammable fluids to pass through the firewall areas of each 
engine nacelle; an inspection of the presence and condition of weather 
seals around certain access panels to each nacelle; and the application 
or reapplication of sealant to discrepant areas. The requirements of 
that AD are intended to prevent an in-flight explosion and fire within 
the zones of the nacelle.

Actions Since Issuance of Previous AD

    Since the issuance of that AD, the manufacturer has developed 
several modifications that are intended to correct discrepancies within 
the nacelle so that an engine fire can be contained within this area. 
These additional modifications will further minimize the spread of fire 
through these zones which, if not contained, could cause structural 
damage to the airplane.

Explanation of Relevant Service Information

    Bombardier, the manufacturer of this airplane model, has issued 5 
de Havilland Dash 8 service bulletins pertaining to modifications that 
are intended to prevent the spread of fire through the zones of the 
nacelle.
    1. Service Bulletin S/B No. 8-54-12, dated January 27, 1989, 
describes procedures for modifying the firewalls of the lower cowlings 
by installing new angle-gasket assemblies; and applying sealant to gaps 
and openings in this area. This modification seals areas where latch 
fittings penetrate the firewalls of the lower cowlings; these areas are 
potential paths for flammable fluid to travel within the nacelle.
    2. Service Bulletin S.B. 8-54-25, Revision `A,' dated July 29, 
1994,

[[Page 12769]]

describes procedures for conducting an inspection of the upper access 
panels of each nacelle for the presence and condition of weather 
sealing, and application or reapplication of sealant, if necessary. It 
also describes procedures for conducting an inspection of the firewall 
areas of each nacelle for gaps and openings at lap joints, between 
bolts, and at carry-through fittings and grommets; and the application 
of sealant, if necessary. Furthermore, this service bulletin describes 
procedures for applying exterior labels on these access panels so that 
maintenance personnel will be notified of the requirement to apply 
sealant whenever these panels are re-installed.
    3. Service Bulletin S.B. 8-54-30, Revision `B,' dated February 5, 
1993, describes procedures for modifying each nacelle by replacing 
Camloc receptacles made of silicon bronze with receptacles of stainless 
steel. The replacement receptacles are able to withstand higher 
temperatures than those now being used.
    4. Service Bulletin S.B. 8-54-31, dated March 8, 1994, describes 
procedures for conducting another inspection of the firewall areas of 
each nacelle for gaps and openings after the modification described in 
Service Bulletin S.B. 8-54-30 has been installed. This service bulletin 
also describes procedures for applying additional sealant to these 
areas.
    5. Service Bulletin S.B. 8-71-19, Revision `B,' dated February 24, 
1995, describes procedures for replacing the door seals of the cowlings 
with improved seals.
    Transport Canada Aviation classified these service bulletins as 
mandatory and issued Canadian airworthiness directive CF-94-10R1, dated 
March 7, 1995, 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 
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 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 Requirements of 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 92-13-11. It 
would continue to require the actions currently required by that AD, 
and would add a requirement that the following actions be performed on 
each engine nacelle:
    <bullet> Installation of new angle-gasket assemblies on the 
firewalls of the lower cowlings, and application of sealant to gaps and 
openings in these areas;
    <bullet> Inspection of the upper access panels of each nacelle for 
the presence and condition of weather sealing, and application or 
reapplication of sealant, if necessary;
    <bullet> Inspection of the firewall areas for gaps and openings at 
lap joints, between bolts, and at carry-through fittings and grommets; 
and the application of sealant, if necessary;
    <bullet> Modification of the nacelle by replacing Camloc 
receptacles made of silicon bronze with receptacles of stainless steel;
    <bullet> Application of additional sealant to the firewall areas 
after the Camloc receptacles have been replaced; and
    <bullet> Replacement of the seals on the cowling doors with 
improved seals.
    These actions would be required to be accomplished in accordance 
with the applicable service bulletins described previously.

Cost Impact

    There are approximately 100 de Havilland Model DHC-8-100 and -300 
series airplanes of U.S. registry that would be affected by this 
proposed AD.
    Each inspection of the low fuel pressure switch adapter/snubber 
that is currently required by AD 92-13-11 takes approximately 4 work 
hours per airplane to accomplish, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of this currently 
required inspection on U.S. operators is estimated to be $24,000, or 
$240 per airplane, per inspection.
    The inspection for gaps or openings in each nacelle, engine-mounted 
firewall area, and certain nacelle weather seals that is currently 
required by AD 92-13-11 takes approximately 12 work hours per airplane 
to accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of this currently required inspection on 
U.S. operators is estimated to be $72,000, or $720 per airplane.
    The installation of new angle-gasket assemblies that is proposed in 
this new AD would take approximately 2 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Required 
parts would be provided by the manufacturer at no cost to operators. 
Based on these figures, the cost impact of this proposed action on U.S. 
operators is estimated to be $12,000, or $120 per airplane.
    The inspection of the upper access panels and firewalls of both 
nacelles, and the application of labels, that is proposed in this new 
AD would take approximately 7 work hours per airplane to accomplish, at 
an average labor rate of $60 per work hour. Required parts would cost 
approximately $43 per airplane. Based on these figures, the cost impact 
of these proposed actions on U.S. operators is estimated to be $46,300, 
or $463 per airplane.
    The replacement of the Camloc receptacles with improved receptacles 
that is proposed in this new AD would take approximately 8 work hours 
per airplane to accomplish, at an average labor rate of $60 per work 
hour. Required parts would cost approximately $15 per airplane. Based 
on these figures, the cost impact of this proposed action on U.S. 
operators is estimated to be $49,500, or $495 per airplane.
    The inspection and application of additional sealant to the 
firewalls of the nacelles that is proposed in this new AD would take 
approximately 4 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. The cost of required parts is 
estimated to be minimal. Based on these figures, the cost impact of 
these proposed actions on U.S. operators is estimated to be $24,000, or 
$240 per airplane.
    The replacement of the seals on the cowling doors that is proposed 
in this new AD would take approximately 4 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Required 
parts would be provided at no cost to operators or would cost $1,270, 
depending on the kit required. Based on these figures, the cost impact 
on U.S. operators of this proposed action is estimated to be between 
$24,000 and $151,000, or between $240 and $1,510 per airplane, 
depending on the kit required.
    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.

[[Page 12770]]

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 39-8281 (57 FR 
37872, August 21, 1992), and by adding a new airworthiness directive 
(AD), to read as follows:

De Havilland, Inc.: Docket 96-NM-73-AD. Supersedes AD 92-13-11, 
Amendment 39-8281.

    Applicability: All Model DHC-8-100 and-300 series airplanes, 
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 (h) 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 the spread of fire through the zones of each nacelle, 
in the event of an explosion during flight, and consequent 
structural damage to the airplane, accomplish the following:

    Note 2: The requirements of paragraphs (a) and (b) of this AD 
are restatements of the same paragraphs that appeared in AD 92-13-
11, amendment 39-8281. These paragraphs require no additional action 
by operators who have already completed the specified actions.

    (a) For airplanes having serial numbers 3 through 248, 
inclusive, on which Modification No. 8/1208 has not yet been 
accomplished, accomplish the following:
    (1) Within 30 days after September 8, 1992 (the effective date 
of AD 92-13-11, amendment 39-8281), remove and inspect the low fuel 
pressure switch adapter/snubber located on each engine fuel heater 
for damage to threads, indication of over-torque, and for proper 
seating, in accordance with the accomplishment instructions of de 
Havilland Alert Service Bulletin A8-73-14, Revision B, dated April 
24, 1992. If the adapter/snubber is damaged or if evidence of over-
torque is present, prior to further flight, replace the adapter/
snubber with a serviceable part, in accordance with that service 
bulletin.
    (2) Thereafter, at any time in which the low fuel pressure 
switch adapter/snubber assembly is removed, accomplish the 
inspection of the assembly as described in paragraph (a)(1) of this 
AD.
    (3) Installation of Modification 8/1208, in accordance with de 
Havilland Service Bulletin 8-28-15, Revision A, dated April 17, 
1992, constitutes terminating action for the inspections required by 
paragraphs (a)(1) and (a)(2) of this AD.
    (b) For all Model DHC-8-100 and -300 series airplanes: Within 30 
days after September 8, 1992 (the effective date of AD 92-13-11, 
amendment 39-8281), accomplish the procedures specified in 
paragraphs (b)(1) and (b)(2) of this AD.
    (1) Inspect the nacelle vertical firewall section, firewall 
extension, and engine mounted firewall (reference: Maintenance 
Manual section 71-30-00) for gaps and openings that could permit 
flammable fluid to pass through. Gaps and openings may be found at 
lap joints, between bolts, and at carry-through fittings and 
grommets. If gaps are found, prior to further flight, seal the gaps 
using PR812, Pro-Seal 700, or other approved firewall sealants 
(reference: Maintenance Manual section 20-21-20). Allow the sealant 
to cure for at least 4 hours prior to further flight.
    (2) Inspect access panels 419AT and 429AT as specified in DHC-8 
Maintenance Manual [section 40-10, pages 12 and 14] (reference: 
Illustrated Parts Catalog 54-30-00, Figure 5, Items 410 and 420) for 
the presence and condition of the weather seal in the gap between 
the panels and the adjacent structure. If the gap is not sealed, 
prior to further flight, seal the panels using PR1422, PR1435, or 
other sealant specified in the DHC-8 Maintenance Manual, section 20-
21-16. A release agent, applied prior to sealing, also may be used 
as specified in DHC-8 Maintenance Manual, section 20-21-19. Allow 
the sealant or release agent to cure for at least 4 hours, prior to 
further flight.
    (c) For airplanes having serial numbers 3 through 137, 
inclusive, on which Modification No. 8/1126 has not been installed: 
Within 1 year after the effective date of this AD, seal the firewall 
of the lower cowling of each engine by installing angle-gasket 
assemblies and applying sealant, in accordance with de Havilland 
Service Bulletin S/B No. 8-54-12, dated January 27, 1989.
    (d) For airplanes having serial numbers 003 through 331, 
inclusive, on which Modification No. 8/1885 has not been installed: 
Within 1 year after the effective date of this AD, accomplish the 
procedures specified in paragraphs (d)(1), (d)(2), and (d)(3) of 
this AD in accordance with de Havilland Service Bulletin S.B. 8-54-
25, Revision `A,' dated July 29, 1994.
    (1) Inspect the vertical firewall section, firewall extension, 
and engine-mounted firewall of the upper structure of each nacelle, 
including the lap joints between bolts and at carry-through fittings 
and grommets, to detect gaps and openings through which flammable 
fluid could pass, in accordance with the service bulletin. If any 
gap or opening is detected, prior to further flight, seal the gap or 
opening, in accordance with the service bulletin.
    (2) Inspect the upper access panels of each nacelle to detect 
the presence and condition of sealant in any gap between each panel 
and its adjacent structure, in accordance with the service bulletin. 
If there is no sealant or the sealant is discrepant, prior to 
further flight, apply or replace sealant, as applicable, in 
accordance with the service bulletin.
    (3) Apply exterior labels and protective coatings to each access 
panel of the left and right nacelle in accordance with the service 
bulletin.
    (e) For airplanes having serial numbers 003 through 332, 
inclusive, on which Modification No. 8/1887 has not been installed: 
Within 1 year after the effective date of this AD, replace the 
Camloc receptacles in each nacelle with stainless steel receptacles, 
and apply additional sealant to the firewall of each nacelle, in 
accordance with de Havilland Service Bulletin S.B. 8-54-30, Revision 
`B,' dated February 5, 1993.
    (f) For airplanes having serial numbers 003 through 357, 
inclusive, on which Modification No. 8/1996 has not been installed: 
Within 1 year after the effective date of this AD, inspect the 
forward and rearward faces of the firewall, firewall extension, and 
engine mounted firewall of the lower structure of each nacelle for 
any gap or opening at lap joints, between bolts,

[[Page 12771]]

and at carry-through fittings and grommets through which flammable 
fluid could pass, in accordance with de Havilland Service Bulletin 
S.B. 8-54-31, dated March 8, 1994. If any gap or opening is 
detected, prior to further flight, apply sealant in accordance with 
the service bulletin.
    (g) For airplanes having serial numbers 003 through 369, 
inclusive, on which Modification No. 8/2001 has not been installed: 
Within 1 year after the effective date of this AD, replace the 
existing seals on the cowling doors of each nacelle with improved 
seals, in accordance with de Havilland Service Bulletin S.B. 8-71-
19, Revision `B,' dated February 24, 1995.
    (h) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the 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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the New York ACO.

    (i) 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.

    Issued in Renton, Washington, on March 11, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-6718 Filed 3-17-97; 8:45 am]
BILLING CODE 4910-13-U