# Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft Engines

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A94-5942

## Record

- **Collection:** Federal Register
- **Document type:** Uncategorized Document
- **Published:** March 15, 1994

## Text

DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-ANE-78]

Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to Turbomeca Arriel 1 series
turboshaft engines, that currently requires a gearbox chip detector
inspection prior to further flight, subsequent inspection at designated
intervals, and if necessary, removal of the gearbox, and also requires
modification of the gearbox if not accomplished previously. This action
would require modification to the intermediate gear that would
constitute terminating action to the repetitive chip detector
inspections. On certain engines this proposal would require immediate
modification of the intermediate gear prior to further flight. This
proposal is prompted by the availability of design improvements to the
intermediate gear. The actions specified by the proposed AD are
intended to prevent damage to the aircraft resulting from engine debris
following an uncontained engine failure.

DATES: Comments must be received by May 16, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Assistant Chief
Counsel, Attention: Rules Docket No. 93-ANE-78, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at
this location between 8 a.m. and 4:30 p.m., Monday through Friday,
except Federal holidays.
The service information referenced in the proposed rule may be
obtained from Turbomeca Engine Corporation, 2709 Forum Drive, Grand
Prairie, TX 75051. This information may be examined at the FAA, New
England Region, Office of the Assistant Chief Counsel, 12 New England
Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (617)
238-7137, fax (617) 238-7199.

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 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 93-ANE-78.'' 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, New England Region, Office of the Assistant Chief Counsel,
Attention: Rules Docket No. 93-ANE-78, 12 New England Executive Park,
Burlington, MA 01803-5299.

Discussion

The Direction Generale de L'aviation Civile (DGAC), which is the
airworthiness authority of France, notified the Federal Aviation
Administration (FAA) that an unsafe condition may exist on Turbomeca
Arriel 1B, 1D, 1D1, 1A with TU13, and 1A1 with TU13, turboshaft
engines. The DGAC advises that they have received reports of seven
inflight engine shutdowns and three uncontained failures of the power
turbine disk. The DGAC also advises that these failures were caused by
failure of the reduction gearbox intermediate gear.
This engine model is manufactured in France and is type
certificated for operation in the United States under the provisions of
Sec. 21.29 of the Federal Aviation Regulations and the applicable
bilateral airworthiness agreement. Pursuant to this bilateral
airworthiness agreement, the DGAC has kept the FAA informed of the
situation described above. The FAA has examined the findings of the
DGAC, 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.
On June 25, 1992, the FAA issued telegraphic airworthiness
directive (TAD) T92-13-52 to require a gearbox chip detector inspection
prior to further flight, subsequent inspection at intervals not to
exceed 5 hours time in service since the last inspection, and if
necessary, removal of the gearbox. The FAA determined after review of
the results of the investigation and analysis performed by the
manufacturer that these failures are due to high cycle fatigue that
initiates from vibration induced by gear teeth wear. Failure of the
intermediate gear can result in an overspeed condition and possible
failure of the power turbine disk. That condition, if not corrected,
can result in damage to the aircraft resulting from engine debris
following an uncontained engine failure.
On October 26, 1992, the FAA issued AD 92-24-08, Amendment 39-8413
(57 FR 54293, November 18, 1992), to supersede AD T92-13-52. That
action requires gearbox chip detector inspection at intervals not to
exceed 8 hours time in service on TU39 modified gearboxes, and requires
modification of the reduction gearbox to standard TU39, if not already
modified to standard TU39.
Since the issuance of that AD, the manufacturer has developed a
modification to the intermediate gear that will inhibit the gear teeth
wear and consequent vibration-induced high cycle fatigue.
Turbomeca has issued Service Bulletin (SB) No. 292 72 0157, Update
No. 2, dated July 30, 1993, that describes procedures for a gearbox
chip detector inspection to find evidence of metal chips that may
indicate impending gear failure, prohibits further operation of
gearboxes that have not been modified to the TU39 standard, and defines
suspect gearboxes that require rework of the gear train components to
prevent failure. Turbomeca has also issued SB No. 292 72 0169, dated
July 12, 1993, that describes procedures for modification (TU232) of
the intermediate gear.
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would supersede AD 92-24-08 to remove gearboxes that were
overhauled prior to June 1, 1992, within 30 days after the effective
date of this AD. Those gearboxes have intermediate gears that are prone
to gear teeth wear due to mixing of used gear train components with new
components. This proposed AD would also require immediate modification
of certain engines to the TU39 which introduces a thicker web
intermediate gear that is more resistant to HCF failure. Finally, this
proposed AD would also continue to require repetitive inspections of
the chip detector for evidence of metal chips until installation of
modification TU232 to the intermediate gear at the next overhaul or
repair of the reduction gearbox. Installation of modification TU232
would constitute terminating action to the inspection requirements of
this AD.
The FAA estimates that 270 engines installed on aircraft of U.S.
registry would be affected by this proposed AD, that it would take
approximately 80 work hours per engine to accomplish the proposed
actions, and that the average labor rate is $55 per work hour.
Turbomeca has advised the FAA that required parts would be provided at
no cost to the operator. Based on these figures, the total cost impact
of the proposed AD on U.S. operators is estimated to be $1,188,000.
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 14
CFR part 39 of the Federal Aviation Regulations 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 amendment 39-8413 (57 FR
54293, November 18, 1992) and by adding a new airworthiness directive
to read as follows:

Turbomeca: Docket No. 93-ANE-78. Supersedes AD 92-24-08, Amendment
39-8413.

Applicability: Turbomeca Arriel Model 1B, 1D, 1D1, 1A with TU13,
and 1A1 with TU13, turboshaft engines installed on but not limited
to Aerospatiale AS-350B helicopters.
Compliance: Required as indicated, unless accomplished
previously.
To prevent damage to the aircraft resulting from engine debris
following an uncontained engine failure, accomplish the following:
(a) For the following Turbomeca Arriel engine models: 1D not
modified to TU232, 1D1 not modified to TU232, 1B modified to TU39
but not modified to TU232, 1A with TU13 modified to TU39 but not
modified to TU232, and 1A1 with TU13 modified to TU39 but not
modified to TU232, accomplish the following:
(1) Except for those engines that have been inspected in
accordance with AD 92-24-08 within 8 hours time in service (TIS)
prior to the effective date of this AD, prior to further flight
remove and inspect the reduction gearbox chip detector for evidence
of metal chips in accordance with Turbomeca Service Bulletin (SB)
No. 292 72 0157, Update No. 2, dated July 30, 1993.
(2) Remove from service reduction gearbox modules that do not
meet the return to service criteria described in Turbomeca SB No.
292 72 0157, Update No. 2, dated July 30, 1993, and replace with a
serviceable part.
(3) Thereafter, at intervals not to exceed 8 hours TIS since the
last inspection, accomplish the following:
(i) Remove and inspect the reduction gearbox chip detector in
accordance with paragraph (a)(1) of this AD.
(ii) Remove from service, if necessary, the reduction gearbox
module in accordance with paragraph (a)(2) of this AD, and replace
with a serviceable part.
(4) At the next overhaul or repair of the reduction gearbox
module after the effective date of this AD, incorporate modification
TU232 in accordance with Turbomeca SB No. 292 72 0169, dated July
12, 1993. Incorporation of modification TU232 constitutes
terminating action to the inspections, and replacement, if
necessary, required in paragraphs (a)(1), (a)(2), and (a)(3) of this
AD.
(b) For the following Turbomeca Arriel engine models: 1B not
modified to TU39, 1A with TU13 not modified to TU39, and 1A1 with
TU13 not modified to TU39, prior to further flight replace reduction
gearbox module No. 5 with a reduction gearbox module No. 5 modified
to standard TU39.
(c) For the following Turbomeca Arriel engine models: 1B, 1A
with TU13, and 1A1 with TU13; with reduction gearbox modules
identified by serial numbers specified in paragraph C.(c) of
Turbomeca SB No. 292 72 0157, Update No. 2, dated July 30, 1993,
that were overhauled prior to June 1, 1992, but not overhauled
between that date and the effective date of this AD, and with less
than 200 hours TIS since overhaul, remove from service and return
for overhaul within 30 days after the effective date of this AD, in
accordance with Turbomeca Service Bulletin (SB) No. 292 72 0157,
Update No. 2, dated July 30, 1993.
(d) 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 Manager, Engine Certification Office. The
request should be forwarded through an appropriate FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager, Engine Certification Office.

Note: Information concerning the existence of approved
alternative methods of compliance with this airworthiness directive,
if any, may be obtained from the Engine Certification Office.

(e) Except for engines specified in paragraph (b) of this AD,
special flight permits may be issued in accordance with FAR 21.197
and 21.199 to operate the aircraft to a location where the
requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on March 8, 1994.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification
Service.
[FR Doc. 94-5942 Filed 3-14-94; 8:45 am]
BILLING CODE 4910-13-P

---

Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A94-5942. Public record. Not legal advice.