[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