[Federal Register Volume 61, Number 209 (Monday, October 28, 1996)]
[Rules and Regulations]
[Pages 55561-55563]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-26960]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-SW-12-AD; Amendment 39-9789; AD 96-21-13]
RIN 2120-AA64
Airworthiness Directives; LITEF GmbH Attitude Heading System
(AHRS) Unit Model LCR-92, LCR-92S, and LCR-92H
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This amendment adopts a new airworthiness directive (AD) that
is applicable to LITEF GmbH Attitude and Heading Reference System
(AHRS) Unit Model LCR-92, LCR-92S, and LCR-92H installed on but not
limited to Sikorsky Aircraft Model S-76 helicopters, McDonnell Douglas
Helicopter Systems Model MD-900 helicopters, Bell Helicopter Textron,
Inc. Model 412 helicopters, and Pilatus Model PC-12 airplanes. This
action requires either installing a placard adjacent to each primary
attitude indicator which states that flight is limited to Visual Flight
Rules (VFR) operations only, or modifying and inspecting the AHRS
wiring cables, requiring a repetitive inspection of the cable
shielding, and inserting a statement into the aircraft flight manual.
This amendment is prompted by a field report and verified by laboratory
tests that shows there is an unusual AHRS reaction to certain radio
frequency signals. The actions specified by this AD are intended to
prevent reliance on or to correct the cause of misleading roll and
pitch information produced by the AHRS when encountering certain radio
frequency signals.
DATES: Effective November 12, 1996.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of November 12, 1996.
Comments for inclusion in the Rules Docket must be received on or
before December 27, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Office of the Assistant Chief Counsel, Attention:
Rules Docket No. 96-SW-12-AD, 2601 Meacham Blvd., Room 663, Fort Worth,
Texas 76137.
The service information referenced in this AD may be obtained from
LITEF GmbH, Postfach 774, 79007 Freiburg, Germany or Sikorsky Aircraft
Corporation, 6900 Main Street, P.O. Box 9729, Stratford, CT 06497-9129.
This information may be examined at the FAA, Office of the Assistant
Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at
the Office of the Federal Register, 800 North Capitol Street, NW.,
suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT:
Mr. Robert McCallister, Aerospace Engineer, Rotorcraft Standards Staff,
FAA, Rotorcraft Directorate, 2601 Meacham Blvd., Fort Worth, Texas
76137, telephone (817) 222-5121, fax (817) 222-5961.
SUPPLEMENTARY INFORMATION: The Luftfahrt-Bundesamt (LBA), which is the
airworthiness authority for the Federal Republic of Germany, recently
notified the FAA that an unsafe condition may exist on aircraft
equipped with LITEF GmbH (LITEF) AHRS Unit Model LCR-92, LCR-92S, or
LCR-92H. The LBA advises that the AHRS unit may provide misleading roll
and pitch information to the attitude indicator, with no failure
indication, when exposed to radio frequency levels much lower than the
levels to which the AHRS unit was qualified.
LITEF has issued LITEF Alert Service Bulletin (ASB) No. VW/JH 6B751
dated June 12, 1996, which specifies that the AHRS unit should only be
used under Day VFR conditions. LITEF has also issued LITEF ASB No.
141450-0000-840-002, dated June 28, 1996, that gives directions for the
modification of the AHRS units. The LBA classified this service
bulletin as mandatory and issued LBA LTA No. 96-212, dated July 4,
1996, in order to assure the continued airworthiness of these AHRS
units in Germany. However, LITEF has also issued LITEF ASB No. 141450-
0000-840-003, dated July 9, 1996 which supersedes LITEF ASB No. 141450-
0000-840-002, dated June 28, 1996. Additionally, Sikorsky Aircraft, a
manufacturer that has installed the affected AHRS units on certain of
its helicopters, has issued Sikorsky Aircraft ASB No. 76-34-6A (287A),
dated September 12, 1996, which provides directions for the
modification of the AHRS units on those helicopters.
This AHRS unit is manufactured in Germany and was approved under
TSO C4c for operation in the United States under the TSO provisions of
14 CFR part 21 and the applicable bilateral airworthiness agreement.
Pursuant to the bilateral airworthiness agreement, the LBA has kept the
FAA informed of the situation described above. The affected AHRS units
have been installed on U.S. type certificated aircraft, including but
not limited to, Sikorsky Aircraft Model S-76 helicopters, McDonnell
Douglas Helicopter Systems Model MD-900 helicopters, Bell Helicopter
Textron, Inc. Model 412 helicopters, and Pilatus Model PC-12 airplanes.
The FAA has examined the findings of the LBA, reviewed all available
information, and determined that AD action is necessary for products of
this type that were approved for operation in the United States.
Since an unsafe condition has been identified that is likely to
exist or develop on other LITEF AHRS units installed on, but not
limited to, Sikorsky Aircraft Model S-76 helicopters, McDonnell Douglas
Helicopter Systems Model MD-900 helicopters, Bell Helicopter Textron,
Inc. Model 412 helicopters, and Pilatus Model PC-12 airplanes
registered in the United States, this AD is being issued to prevent
reliance on or to correct the cause of misleading roll and pitch
information produced by the AHRS when encountering certain radio
frequency signals. This AD requires either installing a placard
adjacent to each primary attitude indicator that states that flight is
limited to Day Visual Flight Rules (VFR) operations only, or if the
primary attitude instrument(s) have been deactivated, that states that
flight is limited to VFR operations only; or modifying and inspecting
the AHRS
[[Page 55562]]
wiring cables, requiring a repetitive inspection of the cable
shielding, and inserting a statement into the aircraft flight manual.
The actions are required to be accomplished in accordance with the
service bulletins described previously.
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All
communications received on or before the closing date for comments will
be considered, and this rule may be amended in light of the comments
received. Factual information that supports the commenter's ideas and
suggestions is extremely helpful in evaluating the effectiveness of the
AD action and determining whether additional rulemaking action would be
needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the 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
AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this rule must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket No. 96-SW-12-AD.'' The postcard will be date stamped and
returned to the commenter.
The regulations adopted herein will 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 final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft, and that it is not a ``significant regulatory
action'' under Executive Order 12866. It has been determined further
that this action involves an emergency regulation under DOT Regulatory
Policies and Procedures (44 FR 11034, February 26, 1979). If it is
determined that this emergency regulation otherwise would be
significant under DOT Regulatory Policies and Procedures, a final
regulatory evaluation will be prepared and placed in the Rules Docket.
A copy of it, if filed, may be obtained from the Rules Docket at the
location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 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. App. 106(G), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive
to read as follows:
AD 96-21-13 LITEF GmbH: Amendment 39-9789. Docket No. 96-SW-12-AD.
Applicability: Attitude and Heading Reference System (AHRS)
Model LCR-92, part number (P/N) 124210-1000, -2000, and -3000, Model
LCR-92S, P/N 141852-1000, -1100, -2000, -2100, -3000, -3100, and
-3200, and Model LCR-92H, P/N 141450-1000, -1100, -2000, -2100,
-3000, and -3100, installed in aircraft certificated in any
category.
Note 1: This AD applies to each aircraft equipped with an AHRS
unit identified in the preceding applicability provision, regardless
of whether the aircraft has been modified, altered, or repaired in
the area subject to the requirements of this AD. For aircraft that
have been modified, altered, or repaired so that the performance of
the requirements of this AD is affected, the owner/operator must use
the authority provided in paragraph (b) to request approval from the
FAA. This approval may address either no action, if the current
configuration eliminates the unsafe condition, or different actions
necessary to address the unsafe condition described in this AD. Such
a request should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any aircraft from the applicability of this AD.
Compliance: Required within 60 calendar days after the effective
date of this AD, unless accomplished previously.
To prevent reliance on or to correct the cause of misleading
roll and pitch information produced by the AHRS unit when
encountering certain radio frequency levels, accomplish the
following:
(a) Perform the procedures contained in paragraph (1) or
paragraph (2):
(1) Obliterate Technical Standard Order (TSO) C4c information
from the TSO label on the exterior of the AHRS unit and install a
placard made of material that is not easily erased, disfigured, or
obscured, adjacent to each primary attitude indicator that states:
(i) ``Flight Limited to Day VFR Operations Only,'' or
(ii) If the primary attitude instrument(s) have been
deactivated, ``Flight Limited to VFR Operations Only'' or
(2) Modify and inspect the AHRS unit and insert a statement into
the operating limitation section of the Airplane or Rotorcraft
Flight Manual as follows:
(i) Modify the AHRS wiring cable in accordance with either the
Accomplishment Instructions of LITEF Alert Service Bulletin 141450-
0000-840-003, dated July 9, 1996, or, for Sikorsky S-76 helicopters,
in accordance with the Accomplishment Instructions of Sikorsky
Aircraft Alert Service Bulletin No. 76-34-6A (287A), dated September
12, 1996.
(ii) Prior to the first flight after modifying the AHRS wiring
cable and thereafter at intervals not to exceed 365 calendar days,
using a calibrated bonding meter, inspect the modified AHRS wiring
cable for proper shielding, proper bonding of the wiring cable
shields, and proper unit grounding. The electrical shielding and
grounding resistance should be less than 0.005 ohms. If the
electrical resistance of the shielding bond is 0.005 ohms or
greater, the cable shielding bond is unacceptable.
(iii) Insert into the operating limitation section of the FAA-
approved Airplane or Rotorcraft Flight Manual the following
statement:
``Switching from DG to MAG or operation of the
switch (MAG mode only) in flight with any bank angle will induce an
unannounced heading error. Activation of either switch at bank
angles over approximately 5 deg. will induce a large fixed heading
error that will not self-align and will force the AHRS into memory
with no heading OFF flag appearing for 5 minutes. If switching
occurs at less than approximately 5 deg. bank angle, self alignment
will occur with a variable slewing rate. Verification of heading
accuracy should be accomplished utilizing cross checking of other
available
[[Page 55563]]
heading systems. If a fixed heading error and/or a heading OFF flag
is present, then realignment can be performed by either the
switch or by the MAG/DG/MAG switch at bank angles less
than approximately 5 deg..''
This revision may be accomplished by inserting a copy of this AD
into the aircraft flight manual.
(b) 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, Rotorcraft Standards Staff, FAA,
Rotorcraft Directorate. Operators shall submit their requests
through an FAA Principal Maintenance Inspector, who may concur or
comment and then send it to the Manager, Rotorcraft Standards Staff.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Rotorcraft Standards Staff.
(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 aircraft to a location where
the requirements of this AD can be accomplished.
(d) The modification and inspections shall be done in accordance
with the Accomplishment Instructions of LITEF SB No. 141450-0000-
840-003, dated July 9, 1996, or, for Sikorsky S-76 helicopters, with
the Accomplishment Instructions of Sikorsky Aircraft ASB No. 76-34-
6A (287A), Revision A, dated September 12, 1996. This incorporation
by reference was approved by the Director of the Federal Register in
accordance with 5 U.S.C. 552(a) and CFR part 51. Copies of the LITEF
ASBs may be obtained from LITEF GmbH, Postfach 774, 79007 Freiburg,
Germany. Copies of the Sikorsky Aircraft ASB may be obtained from
Sikorsky Aircraft Corporation, 6900 Main Street, P.O. Box 9729,
Stratford, CT 06497-9129. Copies may be inspected at the FAA, Office
of the Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort
Worth, Texas; or at the Office of the Federal Register, 800 North
Capitol Street, NW., suite 700, Washington, DC.
Issued in Fort Worth, Texas, on October 10, 1996.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 96-26960 Filed 10-25-96; 8:45 am]
BILLING CODE 4910-13-U
