By Tom Memering
There are many reasons why operators of TFE731-powered business jets perform engine removal and reinstallation in the field. Maybe you want to accomplish an airframe inspection in house and to minimize the aircraft's downtime, you simultaneously ship the engine out for scheduled maintenance. Or perhaps you want to minimize the costs associated with flying the aircraft to an engine service provider, and you remove the engine and ship it to the service provider. Possibly your aircraft is grounded due to Foreign Object Damage (FOD) or performance problems and you have no choice but to change the engine where the aircraft is located. Whatever the reason, there are many factors that need to be taken into consideration before you start. The following will provide some useful tips.
One of the first considerations that may appear obvious, but is often overlooked, is the need for an appropriate shipping container. Honeywell Authorized TFE731 service centers have standard shipping containers for these engines. These containers utilize a preformed, engine contoured, foam enclosure that the engine rests in, free-float style. If you are going to be installing a rental engine while yours is being serviced you'll just use the container that the rental arrived in for your engine. If you aren't using a rental, have your service center ship you a container.
If your engine service needs require access to the engine's compressor for repair or for core zone inspection, it will likely require approximately four to eight weeks to complete the repair process, depending on the workscope, method of shipment, etc. In these cases a rental engine can be utilized to keep the aircraft working during the engine service process. The service center you are working with can supply you with a rental engine from either Honeywell's or its own rental pool. You should make arrangements to secure the rental engine 30 to 60 days prior to the actual removal date to ensure its availability. This way you can utilize ground shipment to minimize costs.
After you confirm the availability and delivery of the rental engine, you must then make sure that you have the tooling and equipment that is needed for the engine change. Again, many of these items would appear to be obvious requirements, but are frequently overlooked. To remove an engine you will need some type of apparatus to lift the engine off of the airframe. This will require the use of a heavy-duty overhead crane system or forklift. Either of these should be capable of lifting a minimum of 1,200 pounds and be able to lift it up to 12 feet in the air. Another piece of equipment that you'll need is an engine sling. The engine sling attaches to the engine hard points that are located on the fore and aft parts of the engine. The overhead crane system or forklift will lift the engine off of the aircraft with the use of this sling. You will also need a place to put the engine once it is removed from the aircraft so that the engine can be "undressed" and prepared for shipment. An engine stand is recommended to perform this function. Your service center can provide you with the engine sling and stand. Appropriate forklifts can be rented in most parts of the world.
If using a rental engine, the first thing that you should do when it arrives is inspect it. Verify that you have received the correct model. Further inspect for any obvious damage and verify that the engine is configured per your needed airframe configuration. Honeywell TFE731 engines (especially rentals) have many configurations and applications so you should verify this at your earliest opportunity.
The airframe requirements associated with an engine change need to be understood. Most TFE731-powered aircraft have engine removal inspection requirements in their respective Chapter 5 maintenance manuals. These inspections range from a simple visual inspection to sophisticated non-destructive testing (NDT) requirements. Some of these inspection requirements differ if you are performing a scheduled vs. unscheduled engine removal. Review Chapter 5 of your aircraft maintenance manual so that you are adequately prepared for the inspections. Most of the inspections include the engine mounts. Often these can be exchanged for the same price as performing the NDT thus saving you time.
You also cannot overlook the need for engine change 100 percent replacement items. Every service center, along with every field engine change, is different. The easiest way to ensure that you have all of the required hardware is to simply purchase an engine change kit from the service center. This will include seals, O-rings, gaskets, etc. Also, you will need 10 quarts of your engine's appropriate engine oil (for each engine), grease and anti-seize compounds to lubricate splines and bolts, high-temp sealant, assorted harness clamps, calibrated torque wrenches, and the appropriate airframe and engine maintenance manuals.
Now that we have adequately planned for the engine removal requirements, it's time to begin the engine removal process. If your engine is being removed to accomplish scheduled maintenance such as an Major Periodic Inspection (MPI) or Core Zone Inspection (CZI) or, if the engine is being removed due to a performance problem, the first thing that must be accomplished prior to removing the engine is to perform a five-point engine performance run. This will provide your service center with the general health of your powerplant by measuring the engine's cumulative N2 and T5 margins at five different power settings.
The five-point engine performance run procedure is listed in the Honeywell light maintenance manual in Chapter 72-00-00 under check instructions page 198.32. Once again, this will require specific equipment and instrumentation to accomplish. Additionally, you should have someone assist you who has experience in performing these performance runs. Also, you should perform this at an airport area that is approved for high power aircraft run-ups and must be performed into the wind. The following will provide the necessary tooling and steps to follow while performing the engine runs.
Before engine run setup:
Note: Make DEEC adjustments in accordance with appropriate light maintenance manual and service bulletin TFE76-3057.
1. Disconnect the engine computer and install the harness adapter cable to the computer airframe harness, the engine computer, and the JEDA box.
2. Place the JEDA box in the baggage compartment.
Steps 3 - 8 are required for performance troubleshooting:
3. Install the L/P port probe P/N 298036-1 (P2.35) in L/P bleed port at the 3:00 or 9:00 position depending on engine position. (Note: The hole in probe plate is a calibrated orifice. Do not obstruct.)
4. Install the fitting (-2 to -4 AN reducer) to P3 on FCU (top fitting of P3 limiter).
5. Set transducer on the side of the JEDA box and connect the wires to the P3.0 and P2.35 connectors on the JEDA box.
6. Connect the P2.35 hose from the probe on engine to the transducer mounted on the side of JEDA box. Make sure the transducer marked P2.35 is used.
7. Connect the P3.0 hose from the FCU to P3.0 transducer on the side of the JEDA box. Again, make certain the P3.0 transducer is used.
8. Connect the OAT probe harness P/N 10-320-232 to the JEDA box and probe. Locate the probe in the shade under A/C fuselage and tape the cable to fuselage.
9. Place the ACES box in the cockpit, and then run the wire harness from the JEDA box communication port to the RS232 port of ACES box. Ensure connection of RS232 connector to prevent data loss. Ensure the wire harnesses and equipment are properly secured.
10. Check condition of JEDA and ACES box batteries. (We recommend you use the spare batteries for the engine run.)
11. Turn on the ACES machine and check for the "TFE731 main menu." If it does not appear, load the data card from the ACES storage box.
12. Select "TFE731 Performance Test" and press enter. Then select "line 1) Define test setup" and press enter.
13. Select the engine model and A/C type using the side arrows until the proper configuration is displayed. Special attention should be paid to ensure the engine model includes APR and exhaust nozzle configurations. Input the engine S/N, hours, cycles, N1 compensator dash numbers, and number of test points (always five test points) to match tested engine condition. Please note, if you do not know the dash number of the compensator, enter 1 as the default. You can find the dash number by either physically checking the part or looking in the engine logbook.
Engine performance run:
Note: Make sure the A/C and engine anti-ice bleed air are off and that the aircraft has adequate fuel to complete the test - approximately 1,500 pounds will be needed. The aircraft must be facing into the wind during testing. Caution: The aircraft should not be tested above 12-knot winds because wind speed and direction affect data accuracy.
1. Select "2) Start test" and press enter.
2. The prompt "A data card is not installed, continue anyway?" will appear. Select "Y" and press enter.
3. Enter N1 of the day and set the pressure altitude.
4. Advance the engine to N1 of the day (making certain not to exceed any engine limits). Press enter.
Note: The ACES box requires a two-minute stabilization period and a one-minute scan period at each of the five points of the run, with the exception of the first point, which requires three minutes.
5. Follow the prompts from the test box and use the down arrow to enter the cockpit gauge readings. Entering cockpit readings is optional, as long as the engine indications are verified as accurate during the run. Press enter. As an option and precaution, it is advisable to record the engine run data on a separate engine run sheet. After each point is complete, ACES will display the finished acquired data. This is your redundant data for Medra input.
6. Follow the prompts to test points two to five. Approach target power using displayed N1 and ACES box, not engine instruments. When test point two is achieved, press enter. Allow the stabilization and scan period to be completed.
NOTE: Reduce power slowly using care not to miss the target. Do not chase power setting. Do not re-advance the power lever. If the target isn't achieved, settle for a figure close to it.
7. Once you have completed all five points, return the engine to idle. At this point you can accomplish additional available checks using the ACES/JEDA boxes. These checks are Overspeed Shutdown, Overtemp Test and Manual Mode. Make sure to reset the engine computers after each test.
Once you have completed the engine run, remove all the equipment and ensure the engine computer is properly hooked up and a leak and operation check is accomplished prior to releasing the engine. When your run is complete, download the engine run data into the Honeywell Medra program for reduction. The program is a tool developed to assist engine shops in troubleshooting TFE731 engine performance. This program takes data gathered either by cockpit instrumentation or by TEC's JEDA equipment, a sophisticated data acquisition device. A successful on-wing, five-point performance run can reveal problems with cockpit instrumentation, engine performance, and engine components. When performed prior to an MPI input, a good five-point performance run can assist the engine shop in making the proper internal adjustments to the engine during assembly, ensuring enhanced outgoing engine performance.
Only qualified individuals using OEM/FAA-approved aircraft flight and maintenance manuals should perform engine runs. With the exception of leak checks, the engine should not be operated unless the full configuration of exhaust ducts is installed. The engine cowling should be completely removed for performance runs. When conducting leak checks, a mini duct (leakage test nozzle) may be used when operating the engine, but idle should not be exceeded.
Once the engine runs have been completed it is now time to remove the engine from the airframe. You should follow the procedures outlined in your airframe manufacturer maintenance manual.
Tom Memering is the service and support manager at Premier Turbines.
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