AD/BAe 146/75 - Removal of Altitude Limitation in Icing Conditions

Administered by Department of Infrastructure, Transport, Regional Development, Communications, Sport and the Arts

Legislation au F2006B03522 In force Legislative Instrument

Legislation content

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

 


British Aerospace BAe 146 Series Aeroplanes

 

AD/BAe 146/75 Removal of Altitude Limitation in Icing Conditions


11/99

 

Applicability: British Aerospace BAe 146-100, -200 and -300 aircraft with AlliedSignal ALF502R series engines.

 

Requirement: 1. For each engine installation, incorporate modifications to prevent uncommanded power reductions in icing conditions in accordance with British Aerospace Service Bulletin 71-72-30473A, Revision 1 dated 2 November 1998, Accomplishment Instructions, Paragraph 2.A.

 

Note 1: AD/ALF/16 mandates engine specific modifications to improve the fan core inlet anti-icing capability.

 

Note 2: CAA (UK) AD 004-02-94R1 and FAA AD 99-15-06 also refer.

 

2.    For fully modified aircraft, remove the existing altitude limitation and N2 limitation placards in accordance with British Aerospace Service Bulletin 71-72- 30473A, Revision 1 dated 2 November 1998, Accomplishment Instructions, Paragraph 2.B, Item 1.

 

For the purpose of this AD, a “fully modified aircraft” is one that incorporates the anti-icing improvement modifications referenced in Requirement 1 on all four engines.

 

3.    Ensure the respective aircraft flight manuals comply with the configuration specified in British Aerospace Service Bulletin 71-72-30473A, Revision 1 dated 2 November 1998, Accomplishment Instructions, Paragraph 2.B, Item 2.

 

Upon compliance with Paragraph 2.B, Item 2, remove the following “green” page amendments, titled Maximum Operating Altitude from the respective aircraft flight manuals:

 

AFM No. 3.7 - A/146-200/41 dated 8 August 1997

AFM No. 3.10..- A/146-300/9 dated 26 June 1996

AFM No. 3.12 - A/146-300/19 dated 26 June 1996

AFM No. 3.13 - A/146-100/20 dated 26 June 1996

 

4.    For each aircraft that has at least one unmodified engine fitted in any position, install altitude limitation and N2 limitation placards in accordance with British Aerospace Service Bulletin 11-137-30405A.

 

Use of a locally manufactured altitude limitation placard denoting a more restrictive altitude limitation (ie. < 26,000’) satisfies the intent of this Requirement.

 

For the purpose of this airworthiness directive an “unmodified “ engine in one that does not incorporate AlliedSignal Service Bulletin ALF/LF 72-1020, Revision 2.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

 

Note 3: Requirement 4 addresses the action previously mandated by AD/BAe 146/69 to identify aircraft subject to the altitude limitation when operating in icing conditions. AD/BAe/69 has been cancelled.

 

Note 4: Requirement 4 also provides for installation of an unmodified engine on a fully modified aircraft. If such action occurs the altitude restrictions in icing conditions must be re-applied. Operators are responsible to ensure flight crews and maintenance personnel are made aware of this requirement according to the dictates of their respective internal procedures.

 

Compliance: 1. Before installation of a modified engine or no later than 31 December 2003 whichever occurs first.

 

2.    On any occasion a fully modified aircraft is to be operated with the altitude limitation in icing conditions removed, but no later than 31 December 2003.

 

3.    Within 2 months after the effective date of this airworthiness directive or prior to operating a fully modified aircraft with the altitude limitation in icing conditions removed, whichever occurs first.

 

4.    Whenever an aircraft is operated after the effective date of this airworthiness directive with an unmodified engine installed in any position.

 

This Airworthiness Directive becomes effective on 4 November 1999.

 

Background: ALF502 engines installed on BAe146 aircraft are prone to a phenomenon known as “rollback” which is an uncommanded power reduction condition and loss of thrust control in certain icing conditions. There have been instances where simultaneous rollback occurred on multiple engines on the same aircraft.

 

Altitude restrictions have been successful as an interim means to prevent rollback events. The modifications mandated by this directive will restore the full certificated operating envelope of the aircraft.

 

This AD also identifies actions that are required if an unmodified engine is installed on an aircraft and removes CASA imposed altitude restrictions from the aircraft flight manual.

Overview

The Civil Aviation Regulations 1998, introduced by the Commonwealth of Australia, aim to maintain the highest possible safety standards in the aviation industry. This legislation, overseen by the Civil Aviation Safety Authority (CASA), was enacted to regulate various aspects of civil aviation, including aircraft maintenance, operations, and airworthiness. The specific problem addressed by this regulation is the uncommanded power reductions, known as "rollback," experienced by ALF502 engines installed on British Aerospace BAe 146 Series Aeroplanes under certain icing conditions, which can compromise flight safety. The policy objective is to ensure the safety of aircraft operations by mandating modifications to prevent such power reductions and restore the full operational capabilities of the aircraft. This is achieved through Airworthiness Directives, such as AD/BAe 146/75, which requires modifications to engine installations and updates to aircraft flight manuals to remove altitude limitations in icing conditions for fully modified aircraft.

Scope and Application

The Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, specifically AD/BAe 146/75, pertains to the British Aerospace BAe 146 Series Aeroplanes and applies to the BAe 146-100, -200, and -300 aircraft equipped with AlliedSignal ALF502R series engines. The directive mandates modifications to prevent uncommanded power reductions in icing conditions by incorporating modifications as per British Aerospace Service Bulletin 71-72-30473A, Revision 1 dated 2 November 1998. For fully modified aircraft, it requires the removal of existing altitude and N2 limitation placards and ensures the aircraft flight manuals comply with the specified configuration. Conversely, for aircraft with at least one unmodified engine, it mandates the installation of altitude limitation and N2 limitation placards. This Airworthiness Directive became effective on 4 November 1999, and compliance must be achieved by specified deadlines, primarily no later than 31 December 2003. The directive addresses the phenomenon known as "rollback," an uncommanded power reduction condition and loss of thrust control in certain icing conditions, by restoring the full certificated operating envelope of the aircraft.

Key Provisions

The Civil Aviation Regulations 1998, specifically in PART 39 - 105, outline an airworthiness directive concerning the British Aerospace BAe 146 Series Aeroplanes, with particular focus on the BAe 146-100, -200, and -300 models equipped with AlliedSignal ALF502R series engines. The directive, AD/BAe 146/75, mandates modifications to address uncommanded power reductions in icing conditions. For each engine, modifications must be incorporated to prevent such reductions, in line with British Aerospace Service Bulletin 71-72-30473A, Revision 1 dated 2 November 1998. Additionally, aircraft must remove existing altitude limitation and N2 limitation placards if fully modified. Compliance with this directive also requires updates to the aircraft flight manuals to reflect the specified configuration. Operators of these aircraft must ensure that modifications are implemented according to the outlined schedule. Specifically, before installing a modified engine or by 31 December 2003, whichever comes first, and within two months of the directive’s effective date, or prior to operating a fully modified aircraft with the altitude limitation removed. If an aircraft is operated with an unmodified engine after the directive’s effective date, altitude limitation and N2 limitation placards must be installed as per British Aerospace Service Bulletin 11-137-30405A. Furthermore, operators must ensure that their flight crews and maintenance personnel are aware of these requirements. Failure to comply with the provisions of this airworthiness directive can result in significant consequences. Operators who do not adhere to the mandated modifications and compliance timelines may face regulatory action. The directive highlights that non-compliance could lead to the continued operation of aircraft under unsafe conditions, potentially resulting in severe safety risks. The directive becomes effective on 4 November 1999, and operators must ensure all modifications are completed by the specified deadlines to avoid any regulatory penalties or risks to air safety.

Legal classification tags

Area of Law
Aviation Law
Instrument
Legislative Instrument
Concepts
Compliance Obligations
Prohibited Conduct
Reporting & Disclosure Obligations

Interactions

Authorises

All Versions

Sourced from the Federal Register of Legislation at 26 August 2026. For the latest information on Australian Government law please go to https://www.legislation.gov.au.