2.23.1 Critical maintenance tasks
“Critical maintenance task” means a maintenance task that involves the assembly of a system or any part on an aircraft, engine or propeller that, if an error occurred during its performance, could directly endanger the flight safety.
Critical maintenance task are divided in two types:
1. maintenance task involving removal/installation or assembly/disassembly of several components of the same type fitted to more than one system, a failure of which could have an impact on safety, on the same aircraft or component during a particular maintenance check, and;
2. the assembly of a control system that, if errors occurred, could result in a failure, malfunction, or defect endangering the safe operation of the aircraft. A control system is an aircraft system by which the flight path, attitude, or propulsive force of the aircraft is changed, including the flight, engine and propeller controls, the related system controls and the associated operating mechanisms.
Performance of the first type of critical maintenance task is established in the MOE
chapter 2.25.
Performance of the second type of critical maintenance task is established in this chapter (also refer to the MOE chapter 3.7 and in the Company Procedure HC.S7E3-QCD-3.7-53).
Critical maintenance tasks are reviewed to assess the impact on flight safety.
The customized to scope of work lists of critical maintenance tasks are identified in the
AMOS by ED. The lists are not exhaustive and are amended as necessary by ED. The
following data sources may be used to identify and amend the lists: TCH data,
occurrence reporting, results of audit, feedback from training, etc. The examples of
critical tasks affecting safety are represented hereafter.
When the operator/ customer defines its own list of critical maintenance tasks the independent inspection required by this MOE chapter and the ones required by the operator/ customer are carried out.
Example of critical tasks affecting safety
1) Tasks that may affect the propulsive force of the aircraft:
- installation, rigging and adjustment power plant / engine;
- installation, rigging and adjustment thrust reverse controls, linkages and cables including their actuating components;
- installation fan blade and spinner;
- Installation borescope plug, engine gearbox crank.
2) Tasks that may affect the control of the aircraft flight path and attitude:
- Installation, rigging and adjustment flight control surface;
- Installation, rigging and adjustment control cable;
- Installation, rigging and adjustment flight control primary actuator
(hydraulic, electrical or mechanical);
- Installation, rigging and adjustment computer or unit except components of the
auto-pilot system.
3) Tasks that may affect the aircraft stability control systems:
- Installation, rigging and adjustment autopilot servo assembly;
- Installation primary altimeter or airspeed indicator;
- Installation fuel transfer components;
4) Tasks that may affect aircraft Landing gear:
- Installation, rigging and adjustment component in landing gear
extension/retraction system;
- Installation, rigging and adjustment component involving its indicating or warning
system, which requires an operational check during a particular maintenance
event.
5) Tasks that may affect aircraft Doors :
- Installation, rigging and adjustment door including entry, service and cargo doors;
- Installation, rigging and adjustment warning and locking mechanism or
emergency opening during a particular maintenance event.
6) Tasks that may affect aircraft Emergency Equipment:
- Installation, rigging and adjustment emergency escape slide/raft.
7) Tasks that may affect aircraft CDCCL:
- Any work inside the fuel tank;
- All works marked as CDCCL in the JOB CARD.
8) Tasks that may affect engine system
- overhaul, calibration or rigging of engines.
2.23.2 Error-capturing methods
This paragraph identifies and details the management of each possible error-capturing
method in use by the S 7 ENGINEERING.
The independent inspection is the primary error-capturing method to be used.
An independent inspection is an inspection performed by an qualifying inspectors of a
task carried out by an authorised person.
An independent inspection should ensure correct assembly, locking and sense of
operation. When inspecting control systems that have undergone maintenance, the
qualifying inspector should consider the following points independently:
- all those parts of the system that have actually been disconnected or disturbed
should be inspected for correct assembly and locking;
- the system as a whole should be inspected for full and free movement over the
complete range;
- cables should be tensioned correctly with adequate clearance at secondary
stops;
- the operation of the control system as a whole should be observed to ensure that
the controls are operating in the correct sense;
- if different control systems are interconnected so that they affect each other, all
the interactions should be checked through the full range of the applicable controls; and
- software that is part of the critical maintenance task should be checked, for
example: version, compatibility with aircraft configuration.
The independent inspection procedure and qualifying inspector’s activity is detailed in
the Company Procedure HC.S7E3-QCD-3.7-53. Requirements to the qualification of qualifying inspectors are represented in the MOE chapter 3.7.
Signed-off procedure of task requiring independent inspection is represented in the
MOE chapter 2.13.
The re-inspection is one more error-capturing method to be used, it is limited to unforeseen cases when only one person is available to carry out the task and perform the independent inspection. The cases cannot be considered unforeseen if the person or organisation has not assigned a suitable qualifying inspector to that particular shop/shift/ etc. In this case person must make record in the ATL / WO / Job Card for reinspection of the work. Re-inspection is carried out by the person after completion of all critical tasks.
Note: Method #4 is applicable when only one person is available to carry out the critical tasks. The person must make record in the ATL/ WO /Job Card for re-inspection of the work. Re-inspection is carried out by the person after completion of all critical tasks.
Completion of technical documentation after critical tasks performance:
- In the Job Card by signatures / stamps in the “Mech.” and “Insp.” areas.
- In the ATL, etc. by signatures in “Action” and “Status” area.
“Critical maintenance task” means a maintenance task that involves the assembly of a system or any part on an aircraft, engine or propeller that, if an error occurred during its performance, could directly endanger the flight safety.
Critical maintenance task are divided in two types:
1. maintenance task involving removal/installation or assembly/disassembly of several components of the same type fitted to more than one system, a failure of which could have an impact on safety, on the same aircraft or component during a particular maintenance check, and;
2. the assembly of a control system that, if errors occurred, could result in a failure, malfunction, or defect endangering the safe operation of the aircraft. A control system is an aircraft system by which the flight path, attitude, or propulsive force of the aircraft is changed, including the flight, engine and propeller controls, the related system controls and the associated operating mechanisms.
Performance of the first type of critical maintenance task is established in the MOE
chapter 2.25.
Performance of the second type of critical maintenance task is established in this chapter (also refer to the MOE chapter 3.7 and in the Company Procedure HC.S7E3-QCD-3.7-53).
Critical maintenance tasks are reviewed to assess the impact on flight safety.
The customized to scope of work lists of critical maintenance tasks are identified in the
AMOS by ED. The lists are not exhaustive and are amended as necessary by ED. The
following data sources may be used to identify and amend the lists: TCH data,
occurrence reporting, results of audit, feedback from training, etc. The examples of
critical tasks affecting safety are represented hereafter.
When the operator/ customer defines its own list of critical maintenance tasks the independent inspection required by this MOE chapter and the ones required by the operator/ customer are carried out.
Example of critical tasks affecting safety
1) Tasks that may affect the propulsive force of the aircraft:
- installation, rigging and adjustment power plant / engine;
- installation, rigging and adjustment thrust reverse controls, linkages and cables including their actuating components;
- installation fan blade and spinner;
- Installation borescope plug, engine gearbox crank.
2) Tasks that may affect the control of the aircraft flight path and attitude:
- Installation, rigging and adjustment flight control surface;
- Installation, rigging and adjustment control cable;
- Installation, rigging and adjustment flight control primary actuator
(hydraulic, electrical or mechanical);
- Installation, rigging and adjustment computer or unit except components of the
auto-pilot system.
3) Tasks that may affect the aircraft stability control systems:
- Installation, rigging and adjustment autopilot servo assembly;
- Installation primary altimeter or airspeed indicator;
- Installation fuel transfer components;
4) Tasks that may affect aircraft Landing gear:
- Installation, rigging and adjustment component in landing gear
extension/retraction system;
- Installation, rigging and adjustment component involving its indicating or warning
system, which requires an operational check during a particular maintenance
event.
5) Tasks that may affect aircraft Doors :
- Installation, rigging and adjustment door including entry, service and cargo doors;
- Installation, rigging and adjustment warning and locking mechanism or
emergency opening during a particular maintenance event.
6) Tasks that may affect aircraft Emergency Equipment:
- Installation, rigging and adjustment emergency escape slide/raft.
7) Tasks that may affect aircraft CDCCL:
- Any work inside the fuel tank;
- All works marked as CDCCL in the JOB CARD.
8) Tasks that may affect engine system
- overhaul, calibration or rigging of engines.
2.23.2 Error-capturing methods
This paragraph identifies and details the management of each possible error-capturing
method in use by the S 7 ENGINEERING.
The independent inspection is the primary error-capturing method to be used.
An independent inspection is an inspection performed by an qualifying inspectors of a
task carried out by an authorised person.
An independent inspection should ensure correct assembly, locking and sense of
operation. When inspecting control systems that have undergone maintenance, the
qualifying inspector should consider the following points independently:
- all those parts of the system that have actually been disconnected or disturbed
should be inspected for correct assembly and locking;
- the system as a whole should be inspected for full and free movement over the
complete range;
- cables should be tensioned correctly with adequate clearance at secondary
stops;
- the operation of the control system as a whole should be observed to ensure that
the controls are operating in the correct sense;
- if different control systems are interconnected so that they affect each other, all
the interactions should be checked through the full range of the applicable controls; and
- software that is part of the critical maintenance task should be checked, for
example: version, compatibility with aircraft configuration.
The independent inspection procedure and qualifying inspector’s activity is detailed in
the Company Procedure HC.S7E3-QCD-3.7-53. Requirements to the qualification of qualifying inspectors are represented in the MOE chapter 3.7.
Signed-off procedure of task requiring independent inspection is represented in the
MOE chapter 2.13.
The re-inspection is one more error-capturing method to be used, it is limited to unforeseen cases when only one person is available to carry out the task and perform the independent inspection. The cases cannot be considered unforeseen if the person or organisation has not assigned a suitable qualifying inspector to that particular shop/shift/ etc. In this case person must make record in the ATL / WO / Job Card for reinspection of the work. Re-inspection is carried out by the person after completion of all critical tasks.
Note: Method #4 is applicable when only one person is available to carry out the critical tasks. The person must make record in the ATL/ WO /Job Card for re-inspection of the work. Re-inspection is carried out by the person after completion of all critical tasks.
Completion of technical documentation after critical tasks performance:
- In the Job Card by signatures / stamps in the “Mech.” and “Insp.” areas.
- In the ATL, etc. by signatures in “Action” and “Status” area.
