[Federal Register: January 10, 2001 (Volume 66, Number 7)]
[Notices]
[Page 2043-2044]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10ja01-154]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
[Policy Statement No. ANE-1993-33.28TLD-R1]
Policy for Time Limited Dispatch (TLD) of Engines Fitted With
Full Authority Digital Engine Control (FADEC) Systems
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed policy statement; request for comments.
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SUMMARY: The Federal Aviation Administration (FAA) announces the
availability of a proposed policy for the
[[Page 2044]]
time limited dispatch (TLD) of engines fitted with full authority
digital engine control (FADEC) systems. This proposed policy would
revise the current policy to clarify it; the basic intent of the policy
would not change.
DATES: Comments must be received by February 9, 2001.
ADDRESSES: Send all comments on the proposed policy to the individual
identified under FOR FURTHER INFORMATION CONTACT.
FOR FURTHER INFORMATION CONTACT: Gary Horan, FAA, Engine and Propeller
Standards Staff, ANE-110, 12 New England Executive Park, Burlington, MA
01803; e-mail: gary.horan@faa.gov; telephone (781) 238-7164; fax: (781)
238-7199.
SUPPLEMENTARY INFORMATION:
Comments Invited
The proposed policy statement is available on the internet at the
following address: http://www.faa.gov/avr/air/ane/ane110/hpage.htm. If
you do not have access to the Internet, you may request a copy by
contacting the individual listed under FOR FURTHER INFORMATION CONTACT.
The FAA invites interested parties to comment on the proposed policy.
Comments should identify the subject of the proposed policy and be
submitted to the individual identified under FOR FURTHER INFORMATION
CONTACT. The FAA will consider all comments received by the closing
date before issuing the final policy.
Background
The FAA Engine and Propeller Directorate (EPD) issued a policy on
time limited dispatch (TLD) on October 28, 1993. The purpose of this
policy is to assure uniformity in applying TLD to engines fitted with
FADEC systems. The objective of the TLD approach is to preserve
suitable FADEC system integrity while minimizing dispatch delays and
cancellations by allowing dispatch of the FADEC system with faults
present. The control system is allowed to continue to operate with
faults present, provided the resulting system operation and overall
average reliability are adequate, and operating exposure in this less
redundant state is appropriately limited.
The dispatchable configrations for the FADEC system and their
associated dispatch intervals are an engine airworthiness limitation
specified in the FAA-approved Airworthiness Limitations Section (ALS)
of the Instructions for Continued Airworthiness (ICA) for the engine.
Although TLD is not a requirement for engine certification, entries in
the ALS become part of the engine type design. In addition, the type
certificate data sheet (TCDS) notes that the engine model has TLD
approval and references the ALS for detailed dispatch interval
information. In this revision, the FAA recommends that an applicant for
engine type design approval include appropriate TLD information in the
engine installation manual.
The applicant must submit a statistical TLD analysis to
substantiate that the overall average reliability of the control system
resulting from the applicant's proposed TLD approach meets the
integrity requirements in the FAA TLD policy. The applicant is also
required to establish a formal, auditable reporting system that
provides periodic reports to the FAA office that oversees the engine
type certificate. This system compares in-service experience with the
analysis on which the TLD approval is granted.
The proposed revision to the TLD policy:
1. Clarifies where the manufacturer must include the TLD approval
statements.
2. Adds a fourth category of faults, for manufacturer/operator
defined dispatch intervals that have no impact on the loss-of-thrust-
control (LOTC) analysis and whose repair time is not specified through
the TLD analysis.
3. Clarifies the engine-aircraft interface regarding the fault
recording means required for TLD.
4. Clarifies that the provision for a temporary extension of the
dispatch interval must be substantiated in the TLD, analysis; also
clarifies the authority of the FAA Principal Maintenance or Avionics
Inspector (PMI/PAI) to temporarily extend the dispatch interval based
on the TLD analysis.
5. Clarifies descriptions of the full-up and single-fault system
models used in the TLD analysis.
6. Clarifies the maintenance strategies, including eliminating the
use of the maintenance terms ``On-Condition'' and ``Condition
Monitoring.''
7. Modifies Table 2 to specify both the short time and long time
fault limitations in terms of the maximum operating time in flight
hours only; to accommodate the addition of a fourth dispatch category.
8. Adds Table 3 to show the time limitations for both the short
time and long time fault conditions associated with the maintenance
approach used to address those fault categories.
9. Adds Figure 1 to show the typical graph used to substantiate the
analysis for compliance with the requirement for equivalent or better
reliability than the hydromechanical technology of early systems.
10. Adds Figure 2 to show a typical aircraft avionics system
associated with FADEC system maintenance information and displays.
(Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.)
Issued in Burlington, Massachusetts, on January 2, 2001.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 01-704 Filed 1-9-01; 8:45 am]
BILLING CODE 4910-13-M