COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Instruments and Automatic Pilots
AD/INST/40 LITEF Attitude Heading Reference System 2/97 DM
Applicability: Attitude Heading Reference Systems (AHRS) manufactured by Litef GmbH, Freiburg, Germany listed below:
Model | Part Number | Model | Part Number |
LCR-92 | 124210-1000 | LCR-92S | 141852-1000 |
| 124210-2000 | | 141852-1100 |
| 124210-3000 | | 141852-2000 |
LCR-92H | 141450-1000 | | 141852-2100 |
| 141450-1100 | | 141852-3000 |
| 141450-2000 | | 141852-3100 |
| 141450-2100 | | 141852-3200 |
| 141450-3000 | | |
| 141450-3100 | | |
Note: Litef Model LCR-92, LCR-92H and LCR-92S AHRS are known to be fitted, but not limited to, Pilatus PC-12 aeroplanes, Sikorsky Aircraft Model S-76 helicopters, Bell Helicopter Textron Inc Model 412 helicopters and McDonnell Douglas Helicopter Systems Model MD-900 helicopters .
Requirement: 1. Carry out one of the following actions:
- Obliterate the United States Federal Aviation Administration (FAA) Technical Standard Order (TSO) C4c information from the TSO label on the exterior of the AHRS and install a placard adjacent to each primary attitude indicator that states:
“Flight Limited to Day VFR Operations Only”, or if the primary attitude instrument(s) have been deactivated, “Flight Limited to VFR Operations Only”,
or;
b. Modify the AHRS wiring in accordance with either the accomplishment instructions of Litef GmbH Service Bulletin 141450-0000-840-003 dated
9 July 1996 or, for Sikorsky S-76 helicopters, the accomplishment instructions of Sikorsky Aircraft Alert Service Bulletin 76-34-6A dated 12 September 1996.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Note 1: A Flight Manual Particular Amendment is required if the Requirement 1b modification is incorporated. This is available from a CASA District Airworthiness Office.
2. Inspect the modified AHRS wiring cable, using a calibrated bonding meter, 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.
Note 2: Compliance with Requirement 1a or alternatively, with both Requirements 1b and 2 will satisfy this Directive.
Note 3: FAA AD 96-21-13 Amdt 39-9789 and LBA AD 96-212/2 refer.
Compliance: For Requirement 1 - Prior to 1 February 1997.
For Requirement 2 - Prior to further flight, immediately following the Requirement 1b modification and thereafter, at intervals not exceeding one calendar year.
This Directive takes effect on 27 November 1996.
Background: The LBA has reported that certain Litef AHRS do not meet the radio frequency (RF) susceptibility requirements of RTCA Inc Document RTCA/DO-160C Section 20 Category W, this may cause the AHRS to generate misleading pitch and roll information. Action specified by this directive are intended to prevent reliance on, or to correct the cause of, misleading roll and pitch information produced by the AHRS when certain RF are encountered.
The FAA approach has been adopted by CASA, rather than that of the LBA, this is due to CASA not being aware of individual aircraft configurations that may effect the RF susceptibility of the AHRS installed in that particular aircraft.
Overview
The Civil Aviation Regulations 1998, as amended, contain provisions for ensuring the safety of civil aviation within Australia. One specific legislative instrument within this framework is the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives AD/INST/40, which addresses issues with certain Litef Attitude Heading Reference Systems (AHRS). This directive was introduced to address problems associated with the AHRS manufactured by Litef GmbH, which can generate misleading pitch and roll information due to radio frequency susceptibility, potentially compromising flight safety. The directive was enacted by CASA to align with the approach taken by the United States Federal Aviation Administration (FAA), aiming to ensure consistent safety standards across international aviation operations. The primary policy objective of this directive is to mandate corrective actions to mitigate the risk of misleading information from the AHRS, thus enhancing overall flight safety and reliability.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 107 Civil Aviation Safety Authority Schedule of Airworthiness Directives, pertains to the compliance of certain Attitude Heading Reference Systems (AHRS) manufactured by Litef GmbH, Freiburg, Germany. This regulation applies to AHRS models LCR-92, LCR-92H, and LCR-92S, identified by their respective part numbers, which are known to be fitted in various aircraft including Pilatus PC-12 aeroplanes, and Sikorsky, Bell, and McDonnell Douglas helicopters. The primary objective of this directive is to address the issue of radio frequency susceptibility, which can lead to misleading pitch and roll information. The regulation mandates compliance with specific actions to ensure the AHRS operates correctly, such as obliterating certain FAA TSO information or modifying the AHRS wiring according to specified service bulletins. Additionally, it requires an inspection of the modified AHRS wiring cable to ensure proper shielding and bonding, with resistance checks not exceeding 0.005 ohms. Compliance is required before certain dates, with ongoing inspections mandated at regular intervals. The directive extends its reach across all aircraft equipped with the specified AHRS within the Commonwealth of Australia, ensuring safety and adherence to aviation standards.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 – 107, outlines directives for airworthiness, including the requirements for the Attitude Heading Reference Systems (AHRS) manufactured by Litef GmbH, Freiburg, Germany (Section 1). These AHRS, identified by specific model and part numbers, must undergo certain modifications or actions to ensure compliance with safety standards. For instance, the regulations mandate either the obliteration of certain FAA TSO C4c information from the AHRS label and the installation of a specific placard (Requirement 1a), or the modification of the AHRS wiring as per specified service bulletins (Requirement 1b) (Section 2). Furthermore, after implementing Requirement 1b, the wiring must be inspected to ensure proper shielding and grounding, with resistance values not exceeding 0.005 ohms (Requirement 2).
The entities governed by these regulations, primarily aircraft operators and maintenance providers, have specific obligations to adhere to these directives. For Requirement 1, compliance is mandated prior to 1 February 1997. For Requirement 2, inspections must occur before further flight immediately following the modification and at intervals not exceeding one calendar year thereafter. Additionally, if Requirement 1b is implemented, a Flight Manual Particular Amendment is necessary, which can be obtained from a CASA District Airworthiness Office (Section 3).
Failure to comply with these directives can lead to significant consequences. The primary concern is the potential for misleading pitch and roll information, which could compromise flight safety. The regulations reference FAA AD 96-21-13 Amdt 39-9789 and LBA AD 96-212/2, indicating that non-compliance could result in safety violations and potential grounding of the aircraft. Although specific penalties are not detailed in the excerpt, non-compliance with Civil Aviation Regulations can generally lead to fines, enforcement actions, and in severe cases, criminal charges against individuals or corporations responsible for the non-compliance (Section 4).