Airworthiness Directive · Amendment 39-22323 · Navigation
BAE Systems (Operations) Limited Airplanes
This AD applies to BAE Systems (Operations) Limited Model Avro 146-RJ70A, 146-RJ85A, and 146-RJ100A airplanes, certificated in any category, equipped with Honeywell inertial reference unit (IRU) part number (P/N) HG2001BC02 or P/N HG2001BC04.
The FAA is adopting a new airworthiness directive (AD) for certain BAE Systems (Operations) Limited Model Avro 146-RJ series airplanes. This AD was prompted by a report that certain inertial reference units (IRUs) have out-of-date magnetic variation (MagVar) tables. This AD requires assessing the values between the MagVar tables of the affected IRUs and the most recently published MagVar data tables, and corrective actions if necessary. The FAA is issuing this AD to address the unsafe condition on these products.
For the purpose of this AD, the following definitions apply:
(1) Affected IRU: A Honeywell IRU having P/N HG2001BC02 using a MagVar lookup table from 1990, or P/N HG2001BC04 using a MagVar lookup table from 1995.
(2) WMM: World Magnetic Model, which is the standard model for navigation, altitude, and heading referencing systems using the geomagnetic field. The WMM is produced at 5-year intervals. The existing WMM as of November 16, 2022 was released December 10, 2019.
Within 3 months after the effective date of this AD, and thereafter at intervals not to exceed 5 years, assess the accuracy of an affected IRU's MagVar data table, in accordance with the Recommendations of BAE Systems All Operator Message 21-011V-1, Issue 1, dated September 27, 2021.
(1) If the difference between an affected IRU's MagVar data table and the existing WMM MagVar data tables is less than or equal to 2 degrees for the routes that the airplane may operate, no further action is required until the assessment is repeated, as required by the introductory text to paragraph (h) of this AD.
(2) If the difference between an affected IRU's MagVar data table and the existing WMM MagVar data tables is greater than 2 degrees for the routes that the airplane may operate: Do the actions required by paragraph (h)(2)(i) or (ii) of this AD.
(i) Within three months after the effective date of this AD or before further flight after the assessment in the introductory text to paragraph (h) of this AD, whichever occurs later: Update the airplane's affected IRU MagVar data tables in accordance with the Recommendations of BAE Systems All Operator Message 21-011V-1, Issue 1, dated September 27, 2021.
(ii) Comply with the provisions specified in, and at the times specified in, paragraphs (h)(2)(ii)(A) and (B) of this AD.
(A) Further flight is prohibited in areas where the difference between the installed and the existing MagVar values exceeds the 2 degree tolerance unless both terrain awareness warning system (TAWS) and traffic collision avoidance system (TCAS) are installed and operative.
(B) Before further flight, revise the operator's existing FAA-approved minimum equipment list (MEL) to prohibit dispatch unless both TAWS and TCAS are installed and operative.
(3) If an affected IRU's MagVar data table cannot be determined, follow the procedures specified in the Recommendations of BAE Systems All Operator Message 21-011V-1, Issue 1, dated September 27, 2021.
(4) This AD does not require operators to provide flightcrews with certain operating procedures as those actions are already required by existing FAA operating regulations (see 14 CFR part 91).
Updating both affected IRUs, as specified in paragraph (h)(2)(i) of this AD, terminates the MEL prohibition specified in paragraph (h)(2)(ii)(B) of this AD, provided both TAWS and TCAS are installed and operative.
