during this ground check, shut the engine down and repeat the  inspection for metal particles in the oil system. Metal particles in the engine oil screens or the magnetic chip  detectors are generally an indication of partial internal failure  of the engine. Carbon tends to break loose from the interior  of the engine in rock-like pieces that have the appearance  of metal. It is necessary to consider these possibilities when  foreign particles are found on the engine oil screens or  magnetic chip detectors. Before removing an engine for suspected internal failure, as  indicated by foreign material on the oil screens or oil sump  plugs, determine if the foreign particles are ferrous metal by  placing them close to a magnet to see if they are magnetic. If  the material is not magnetic, it is not attracted by the magnet.  Any ferrous metal in the oil screens is cause for concern.  Very small amounts of nonferrous metal, especially after  major engine maintenance, can sometimes be normal. If the  particles are metal, determine the probable extent of internal  damage. For example, if only small particles are found that  are similar in nature to filings, drain the oil system, and refill  it. Then, ground-run the engine and reinspect the oil screens  and magnetic chip detectors. If no further evidence of foreign  material is found, continue the engine in service or per the  manufacturer’s instructions. However, engine performance  should be closely observed for any indication of difficulty  or internal failure. Spectrometric oil analysis program allows an oil sample  to be analyzed and searched for the presence of minute  metallic elements. Due to oil circulation throughout an  aircraft engine, every lubricant that is in service contains  microscopic particles of metallic elements called wear  metals. As the engine operates over a certain amount of time,  the oil picks up very small particles that stay suspended in  the oil. Oil analysis programs identify and measure these  particles in parts per million (PPM) by weight. The analyzed  elements are grouped into categories, such as wear metals  and additives, and their measurement in PPM provides the  data that expert analysts can use as one of many tools to  determine the engine’s condition. If certain metals have an  increase in PPM, it can be a signal of component wear or  pending failure of the engine. The amount of wear metals  is recorded and noted each time a sample is taken. If the  amount of wear metals increases beyond a normal rate, then  the operator can be notified quickly so repair, a recommended  specific maintenance procedure, or inspection can be ordered.  The advantage of oil analysis is an increase in safety by  noticing an engine problem before engine failure. It also saves  money by finding engine problems before they become large  problems or complete engine failure. This procedure can be  used for both turbine and reciprocating engines. Oil analysis  can be used to diagnose impending engine failure and would  be a reason for removing the engine from the aircraft and  sending it to overhaul. Many turbine engines are monitored by an engine condition  program that helps determine the health of the engine in  service. This can also be called trend analysis performance  monitoring, but it consists mainly of monitoring certain  engine parameters daily and watching for trend shifts or  changes in the engine parameters. A shift in key parameters  (change over time) could be a warning that the engine has  serious internal deterioration and should be overhauled. Engines are usually removed when there are consistent  engine operational problems. Engine operational problems  generally include, but are not limited to, one or more of the  following conditions: After the decision has been made to remove an engine, the  preparation of the replacement engine must be considered.  The maintenance procedures and methods used vary widely.  Commercial operators, whose maintenance operations  require the most efficient and expeditious replacement of  aircraft engines, usually rely on a system that utilizes the  quick-engine-change assembly (QECA), also sometimes  referred to as the engine power package. The QECA is  essentially a powerplant and the necessary accessories  installed in the engine. Spectrometric Oil Analysis Engine Inspection  Program Metal Particles in the Oil Turbine Engine Condition Monitoring Programs Engine Operational Problems General Procedures for Engine Removal  and Installation Preparation of Engines for Installation 1.  Excessive engine vibration; this is especially true with  turbine engines. 2.  Backfiring, or misfiring, either consistent or  intermittent due to valve train or other mechanical  defect in reciprocating engines. 3.  Turbine engines that exceed normal operating  parameters or life limited components exceeding  maximum time in service or cycles. 4. Low power output, generally caused by low  compression, with reciprocating engines and internal  engine deterioration or damage with turbines. 8-3