A COMPLETE AND COMPREHENSIVE MAINTENANCE METHOD
The MORE STC affords an on condition maintenance concept by increasing the frequency and thoroughness of routine engine inspections. It combines five elements into an integrated, comprehensive and systematic maintenance method.
The main elements of the MORE STC are:
Periodic Engine Performance Monitoring
Periodic Oil and Oil Filter Debris Analysis
Periodic Engine Vibration Analysis
Periodic Borescope or Visual Inspection of the Hot Section
Periodic CT Blade Overhaul Inspection
The following inspections normally prescribed by P&WC are performed at a shorter inspection interval. (e.g. Fuel Nozzles, Bleed Valve(s), Chip Detector, Power Plant Cleaning, Fuel Pump Filters, Compressor Visual Inspection, Power Turbine Visual Inspection, & Propeller Balancing)
The engine is separated into four modules (i.e. Power Section, Compressor, Hot Section and Accessories). This is intended to allow the modules to be repaired separately, if / when appropriate.
Periodic borescope inspections of the internal parts of the engine (hot section and compressor) is used to identify many engine problems in their early stages and to enable corrective action. This avoids costly repairs and down time. Engine borescope inspection of internal parts without the need to disassemble the engine allows the hot section to operate “On Condition”.
Initial Inspection: This inspection will establish an initial baseline and the present condition of the engine. The earlier the engine is maintained in accordance with the MORE STC the better the engine health will be in the long run.
An FAA Form 337 or foreign equivalent (a sample of front and back can be found here) is required to incorporate the STC along with a notice to the FAA informing them that the engine will be using the STC for the maintenance per FAR 91.409.
When transferring aircraft ownership to a new owner, a notice to the FAA is required at the same time the new owner registers the aircraft. For convenience only, see FAA Note Transfer for details.
Continuing Inspections: Engine inspection intervals are required to keep the engine operating at its peak and to keep the maintenance costs to a minimum.
PT6A engines maintained under the Maintenance On Reliable Engines (MORE) Instructions For Continued Airworthiness are separated into modules for record keeping purposes. Experience has shown that some portions of the PT6A engine need inspection / repair more often than other portions. The purpose is to allow each module to be repaired or overhauled when appropriate and when the remainder of the engine is operating normally to allow the remainder of the engine in service until there is a reason for it to be repaired or overhauled.
The record keeping modules in the MORE Instructions For Continued Airworthiness are:
Accessories
Compressor Module
Hot Section Module
Power Section Module
Example: An engine with 4000 hours TSO experiences a lightning strike. The Power Section Module will require repair but the owner decides to overhaul it instead. The Power Section Module will then have 8000 hours before overhaul is required again. At 8000 hours TSO, the other three modules are removed for overhaul, but the Power Section Module will not need overhaul since it has 4000 hours to go before next overhaul.
This function is performed at specific time intervals. Oil & Filter Analysis can help detect excessive wear of oil-wetted engine components and provide early warning of an impending failure of specific parts. Oil Sampling & Oil Filter Analysis can only be performed using the MORE Company Filter Analysis Tool Kit and Oil Sampling Kit from MORE Company. There is no need for a spare oil filter. With this kit, only the debris is removed and analyzed. The final task is to clean the filter in accordance with the Pratt & Whitney Manual.
Performed at regular intervals, engine performance monitoring informs you if an engine needs repair. It is used to evaluate the efficiency of the engine on a regular basis, and to detect gradual changes over time that will help pinpoint problems while the corrective actions are small and less expensive, allowing continuous safety, reliability and high performance of the engine.
Performed on a routine basis, propellers are balanced using an electronic balancer. Once completed, the full spectrum of engine vibration is recorded using a Chadwick Vibration Analyzer 192A on chart cards, the MicroVib II Aircraft Analyzer (see MORE Service Bulletin 101 for more details), or the ACES GEN II Analyzers covering the ACES Model 2021 Cobra II, ACES Model 4041 Viper II, ACES Model 4041E Viper 2E (see MORE Service Bulletin 104 for more details). Specific speeds (rpm) and balances (ips) are reviewed and identified to the corresponding speeds of critical parts in the engine. The results are used to compare readings from one inspection to the next and any changes are noted or corrected. Increases in vibration can indicate a deterioration of rotating parts. Early identification will keep the engine running safer and keep maintenance costs down.