Reciprocating engines and gas turbine engines are used in  this chapter to describe and represent general and typical  procedures for engine buildup, removal, preservation,  storage, and installation. Although these two types of engines  have some common areas, each procedure has been included  to ensure adequate coverage of the engines used in both  heavy and light aircraft. It should be emphasized that while  procedures for specific engines and aircraft are included  in this chapter, many pertinent or mandatory references  have been omitted because of their irrelevance to a general  discussion. For this reason, always reference the applicable  manufacturer’s instructions before performing any phase of  engine removal or installation. The following paragraphs outline the most common reasons  for removing and replacing an engine. Information to aid  in determining engine conditions that require removal  is included; however, in every case, consult applicable  manufacturer’s instructions as the final authority in  establishing the basis for engine replacement. Engine life is dependent upon such factors as operational  use, the quality of manufacture or overhaul, the type of  aircraft in which the engine is installed, the kind of operation  being carried out, and the degree to which maintenance is  accomplished. Thus, the manufacturer sets engine removal  times. Based on service experience, it is possible to establish  a maximum expected time before overhaul (TBO) or span of  time within which an engine needs to be overhauled. Certain  critical components of turbine engines such as turbine blades,  turbine disks or combustion liners may have shorter life  limits established by the manufacturer due to the stresses  imposed on those parts during operation. The FAA requires  that the manufacture identify and establish which parts have  mandatory replacement times. Sudden stoppage is a very rapid and complete stoppage of the  engine. It can be caused by engine seizure or by one or more  of the propeller blades striking an object in such a way that  revolutions per minute (rpm) goes to zero in less than one  complete revolution of the propeller. Sudden stoppage may  occur under such conditions as complete and rapid collapse  of the landing gear, nosing over of the aircraft, or crash  landing. Sudden stoppage can cause internal damage, such  as cracked propeller gear teeth, gear train damage, crankshaft  counterweights becoming detuned or misalignment, or  damaged propeller bearings. When sudden stoppage occurs,  the engine usually requires replacement or disassembly and  inspection as per manufacturer’s instructions. Sudden reduction in engine speed can occur when one or  more of the propeller blades strike an object at a low engine  rpm. After impact, the foreign object is cleared and the engine  recovers rpm and continues to run unless stopped to prevent  further damage. While taxiing an aircraft, sudden reduction  in speed can occur when the propeller strikes a foreign object,  such as a raised section in the runway, a tool box, or a portion of  another airplane. When the accident occurs at high engine rpm,  shocks are much more severe. When sudden reduction in rpm  occurs, the following procedure can be used as a general rule,  but you must comply with the manufacturer’s information.  Make a thorough external inspection of the engine mount,  crankcase, and nose section to determine whether any parts  have been damaged. If damage is found that cannot be  corrected by line maintenance, remove the engine. Internal  components can be damaged, especially counter weights on  the crankshaft. Remove the engine oil screens or filters. Inspect them for  the presence of metal particles. Remove the engine sump  plugs, drain the oil into a clean container, strain it through a  clean cloth, and check the cloth and the strained oil for metal  particles. Heavy metal particles in the oil indicate a definite  engine failure, and the engine must be removed. However, if  the metal particles present are similar to fine filings, continue  the inspection of the engine to determine its serviceability.  If there are no heavy metal particles in the engine oil, check  again for metal in the oil system after operating the engine.  Metal in the screens is a sign that the bearings have been  compromised and are in the process of failing. Remove the propeller and check the crankshaft, or the  propeller drive shaft on reduction-gear engines, for  misalignment. Clamp a test indicator to the nose section of the  engine. Use the dial-indicator that has  1 ⁄ 1,000-inch graduations.  Remove the spark plugs from all the cylinders. Then, turn the  crankshaft, and observe if the crankshaft, propeller shaft, or  flange turns straight without any bending taking place. If there  is an excessive runout (bend in the crankshaft or propeller  flange) reading at the crankshaft or propeller-drive shaft at  the front seat location, the engine should be removed. Consult  the applicable manufacturer’s instructions for permissible  limits. If the crankshaft or propeller drive shaft runout does  not exceed these limits, install a serviceable propeller. Make  an additional check by tracking the propeller at the tip in the  same plane, perpendicular to the axis of rotation, to assure  that blade track tolerance is within the prescribed limits. Start the engine to see if operation is smooth, without vibration,  and the power output adequate. If the engine operates properly  Sudden Stoppage Engine or Component Lifespan Exceeded Reasons for Removal of Reciprocating  Engines Sudden Reduction in Speed 8-2