AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
General Electric Turbine Engines - CT7 Series
AD/CT7/9 Compressor Variable Geometry Schedule 6/2003
TX
Applicability: All CT7-9B engines.
Note 1: These engines are known to be installed on but not limited to SAAB Aircraft 340B aeroplanes.
Requirement: 1. Determine the Variable Geometry (VG) rigging schedule for both engines. If the compressor VGs are rigged to VG schedule N using GEAE Service Bulletin (SB) CT7-TP S/B 72-0328 or GEAE Alert Service Bulletin (ASB) CT7-TP S/B 72- A0328 Revision 1 no further action is required.
Note 2: The engines with Serial Numbers (S/Ns) listed in Table 1 of this directive are known to have been rigged to VG schedule N1.
2. If the compressor VGs on both engines on the aeroplane are rigged to VG schedule N1, accomplish the following:
- rig the compressor VG on one engine to VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment instructions of GEAE ASB No. CT7-TP S/B 72-A0328 Revision 1; and
- rig the compressor VG on the remaining engine to VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment instructions of GEAE ASB No. CT7-TP S/B 72-A0328 Revision 1.
3. If the compressor VG on one engine on the aeroplane is rigged to VG schedule N1, rig the engine to the VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment instructions of GEAE (ASB) No. CT7-TP S/B 72-A0328 Revision 1.
4. Do not install any GE CT7-9B engine rigged to VG schedule N1 on a SAAB Aircraft AB 340B aircraft.
Table 1 S/N’s of Engines Known to Have Been Rigged to VG Schedule N1.
785102 | 785104 | 785106 | 785107 | 785109 | 785111 |
785112 | 785113 | 785117 | 785118 | 785125 | 785128 |
785129 | 785131 | 785133 | 785136 | 785138 | 785148 |
785150 | 785151 | 785152 | 785154 | 785160 | 785185 |
785188 | 785211 | 785231 | 785232 | 785234 | 785235 |
785237 | 785239 | 785241 | 785257 | 785259 | 785265 |
785266 | 785275 | 785322 | 785325 | 785326 | 785334 |
785375 | 785391 | 785400 | 785459 | 785460 | 785462 |
785465 | 785474 | 785476 | 785477 | 785480 | 785481 |
785487 | 785499 | 785506 | 785534 | 785538 | 785554 |
785569 | 785591 | 785592 | 785598 | 785603 | 785700 |
785759 | | | | | |
Note 3: FAA Emergency AD 2003-08-52 refers.
Compliance: 1. Within 30 flight hours or 3 days from the effective date of this directive. 2a. Within 30 flight hours or 3 days from the effective date of this directive,
whichever is the later.
2b. Within 100 flight hours or 10 days from the effective date of this directive, whichever occurs first.
3. Within 100 flight hours or 10 days from the effective date of this directive, whichever occurs first.
4. From the effective date of this directive.
This Airworthiness Directive becomes effective on 17 April 2003.
Background: This directive is in response to 12 stall events that occurred over a 6- month period. It has been determined that in the majority of the stall events the VG was rigged to the N1 schedule. Re-rigging the VG to the N schedule will give a highe r stall margin. If the VG schedule is not adjusted to the N schedule the aircraft could suffer a dual inflight shutdown or power loss during deceleration from take off power to climb power.
David Villiers
Delegate of the Civil Aviation Safety Authority 16 April 2003
The above AD is notified in the Commonwealth of Australia Gazette on 17 April 2003.
Overview
The Civil Aviation Safety Authority Airworthiness Directive (AD) CT7/9, issued in 2003, targets compressor variable geometry (VG) rigging issues in General Electric CT7-9B turbine engines installed on Saab Aircraft 340B aeroplanes. This legislative instrument was introduced in response to a series of stall events linked to engines rigged to the VG schedule N1, which was identified as a contributing factor in the majority of these incidents. The directive aims to ensure the airworthiness of these aircraft by requiring specific actions to adjust the VG rigging, thereby enhancing safety by preventing potential in-flight shutdowns or power losses. The AD was enacted under the authority of the Civil Aviation Safety Authority delegate and specifies precise compliance timelines to ensure prompt implementation of the necessary corrective actions.
Scope and Application
The Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 applies to all CT7-9B engines, which are predominantly installed on Saab Aircraft 340B aeroplanes. The directive mandates specific actions to correct the unsafe condition identified in certain compressor Variable Geometry (VG) schedules. If the compressor VGs are already rigged to the N schedule according to GE Aviation Engine Service Bulletin (SB) CT7-TP S/B 72-0328 or Alert Service Bulletin (ASB) CT7-TP S/B 72-A0328 Revision 1, no further action is required. However, if the engines are rigged to the N1 schedule, the directive requires that the VG on both engines be re-rigged to the N schedule as per the instructions in GEAE ASB No. CT7-TP S/B 72-A0328 Revision 1. Additionally, engines with specific serial numbers listed in the directive must not be installed on Saab Aircraft 340B aircraft. The AD became effective on 17 April 2003, and compliance is required within 30 flight hours or 3 days from the effective date, or within 100 flight hours or 10 days, whichever occurs first, for certain actions. This directive extends its application through subordinate instruments, ensuring that all relevant parties adhere to the specified requirements to maintain airworthiness.
Key Provisions
The Airworthiness Directive (AD) CT7/9 pertains to the CT7-9B series of turbine engines, specifically those installed on SAAB Aircraft 340B aeroplanes. The AD outlines the requirements for the Variable Geometry (VG) rigging schedule of these engines, which are critical to ensuring safe operation (Requirements section). For engines already rigged to VG schedule N using GEAE Service Bulletin CT7-TP S/B 72-0328 or GEAE Alert Service Bulletin CT7-TP S/B 72-A0328 Revision 1, no further action is required (Requirement 1). However, if the compressor VGs are rigged to VG schedule N1, then the engines must be re-rigged to VG schedule N in accordance with specific instructions (Requirements 2, 3, and 4).
The AD imposes several obligations on the entities governed by it. Firstly, it mandates that the compressor VG rigging schedules of all CT7-9B engines must be determined (Requirement 1). If the engines are rigged to VG schedule N1, they must be re-rigged to VG schedule N in accordance with detailed instructions provided in GEAE ASB No. CT7-TP S/B 72-A0328 Revision 1 (Requirements 2 and 3). Additionally, it prohibits the installation of any GE CT7-9B engine rigged to VG schedule N1 on a SAAB Aircraft AB 340B aircraft (Requirement 4). These actions must be completed within specified timeframes following the effective date of the AD, which is 17 April 2003 (Compliance section).
Failure to comply with the AD can result in serious consequences. The directive is issued in response to multiple stall events caused by the incorrect rigging of the VG to the N1 schedule, which can lead to dual inflight shutdowns or power loss. The AD does not specify any explicit civil or criminal penalties for non-compliance, but it is clear that adherence is mandatory for maintaining airworthiness. Non-compliance could potentially lead to enforcement actions by the Civil Aviation Safety Authority (CASA), which may include grounding of the aircraft, fines, or other regulatory sanctions.