The test cell building is usually constructed of concrete and contains both the control room and engine room, although in some test cells only the control room is enclosed. A typical test cell and a control room are shown in figure 3.1. If an engine fails during a test run or does not perform to the standards set by the manufacturer, that engine and a specified number of previous engines are disassembled to check for faults.The mobile trailer unit contains engine testing equipment similar to that available in an engine test cell. The mobile unit increases engine availability by eliminating most of the need to return engines to an overhaul depot.
The engine is run in the test cell with the same demands placed upon it as if it were installed in an aircraft. The performance of any engine is considerably influenced by changes in ambient temperature and pressure, because of the way these conditions affect the weight of the air entering the engine.During the initial run after assembly, or after extensive maintenance or overhaul, engine statistics are recorded on a test log. This log sheet remains with the engine historical records until such time as another data sheet is completed.
In addition, oil temperature, bearing scavenge-oil temperature, seal leakage, and oil consumption must be within established limits. These tests are usually performed under other than standard day conditions, and data will then be computed to a standard day rating by using the charts and tables in the engine manual. This new information is entered on the engine test log sheet as shown in figure 3.2 and becomes a permanent part of the engine records.
At Takeoff power settings the propeller may pick up and throw loose dirt, gravel, and other debris over a considerable distance. Precautionary measures must be taken during the ground running of turbine engines to avoid injury to personnel and damage to property o other aircraft. Occasionally During the starting of a turbine engine, excess fuel accumulates in the exhaust ducting and when ignited causes long flames to be blown from the exhaust nozzles. Personnel must ensure that the run up area is clear of inflammable materials and ground equipment.
Engine testing & storage
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Before any engine is shipped to the user, the manufacturer or overhaul facility has test-run the engine in a test cell to ensure quality control. Ground operation, or testing of an engine may also be performed in the mobile engine test unit (METU).
Test-cell instrumentation usually includes temperature and pressure gages to monitor engine performance. To compare the performance of similar engines on different days, under different atmospheric conditions, a given engines performance must be corrected to the standard day condition of 29.92 inches of mercury and 59 F.
During testing, any problem that would limit the engines performance, such as exhaust gas temperature, torque, fuel flow, or maximum speed, is corrected.
Ground Testing is intended to give an engine a thorough test for mechanical soundness and for correct indications of operating parameters. Toavoid repeating the instructions, the following checks are based on reversing engines which utilize the fuel cut-off lever as means of controlling starting and shutdown.
On non-reversing engines this is accomplished by the initial movement of the power control ever to the IDLE detent. In cases of conflict between the instructions in this manual and those in the applicable aircraft manual, the latter will apply. To eliminate unnecessary ground running, ground testing is divided into ground test procedures o checks, as follows:
NOTE: Although Procedures for groundtesting are described herein, theappropriate air frame manufacturer’smanual must be consulted for detailedprocedures, curve so tables required tocarry out the tests.
Check No.1 PrestartCheck No.6 Engine Check No.2 Engine Shutdown Start Check No.5 Check No.3 Setting Acceleration Maximum GasCheck/Adjustment Generator Speed Check No.4 Engine Performance And Data Plate Speed
There are three categories of storage, that is: Flyable storage. Temporary storage. Extended storage.* The decision as to which category of storage is to be used depends upon the length of time the engine will be inactive.
An engine that will not be operated for a period of at least 72 hours, or more than 14 days, must be preserved and maintained with all components and systems in an operable condition. On the third day, the engine must be run-up or motored with the starter.
An engine that will not be operated for over 14 days, but less than 45 days, must be placed in temporary storage. Engines normally falling in this category are those undergoing minor repair or modification which requires idleness for a period not to exceed 45 days.
An engine that will be inactive for more than 45 days, but not exceeding 180 days, must be preserved and maintained in extended storage. Usually, this includes those engines undergoing major repair or modification, or any other circumstance that would warrant idleness for 45 to 180 days.
All preservation procedures require that any accumulation of dirt be removed from the engine with dry cleaning solvent. Under usual conditions, it will not be necessary to clean the entire external surface of the engine. If necessary, perspiration residues can be removed from close tolerance bare metal surfaces by wiping with a clean cloth dampened in fingerprint remover before cleaning with solvent.
To prevent oil contamination, never mix synthetic- base oils with mineral-base oils. Synthetic-base lubricating oil is required for the engine. Only a synthetic-base corrosion preventive oil can be used to spray the compressor for corrosion prevention.