not before, the throttle or the fuel shutoff lever is placed in  the OFF position. Generally, an engine should not be shut down by the fuel  shutoff lever until after the aircraft throttle has been retarded  to idle. Because the fuel shutoff valve is located on the fuel  control discharge, a shutdown from high thrust settings results  in high fuel pressures within the control that can harm the  fuel system parts. When an accurate reading of the oil level in the oil tank is  needed following an engine shutdown, the engine should  be operated and shut down with the oil check taking place  within not more than 30 minutes after shutdown. Check the  engine manuals for the specific procedure. Included in this section are typical guidelines for locating  engine malfunctions on most turbine engines. Since it would  be impractical to list all the malfunctions that could occur,  only the most common malfunctions are covered. A thorough  knowledge of the engine systems, applied with logical  reasoning, solves most problems that may occur. Figure 10-75  enumerates some malfunctions that may be  encountered. Possible causes and suggested actions are given  in the adjacent columns. The malfunctions presented herein  are solely for the purpose of illustration and should not be  construed to have general application. For exact information  about a specific engine model, consult the applicable  manufacturer’s instructions. Turboprop engine operation is quite similar to that of a  turbojet engine, except for the added feature of a propeller.  The starting procedure and the various operational features  are very much alike. The turboprop chiefly requires attention  to engine operating limits, the throttle or power lever setting,  and the torquemeter pressure gauge. Although torquemeters  indicate only the power being supplied to the propeller and  not the equivalent shaft horsepower, torquemeter pressure  is approximately proportional to the total power output  and, thus, is used as a measure of engine performance. The  torquemeter pressure gauge reading during the takeoff engine  check is an important value. It is usually necessary to compute  the takeoff power in the same manner as is done for a turbojet  engine. This computation is to determine the maximum  allowable exhaust gas temperature and the torquemeter  pressure that a normally functioning engine should produce  for the outside, or ambient, air temperature and barometric  pressure prevailing at the time. All test run-ups, inspections, and troubleshooting  should be performed in accordance with the applicable  engine manufacturer’s instructions. In  Figure 10-76 , the  troubleshooting procedure for the turboprop reduction gear,  torquemeter, and power section are combined because of their  inter-relationships. The table includes the principal troubles,  together with their probable causes and remedies.  Some of the most important factors affecting turbine engine  life are EGT, engine cycles (a cycle is generally a takeoff  and landing) and engine speed. Excess EGT of a few degrees  reduces turbine component life. Low EGT materially reduces  turbine engine efficiency and thrust. So, to make the engine  highly efficient, the exhaust temperatures need to be as high  as possible, while maintaining an EGT operating temperature  that does not damage the turbine section of the engine. If the  engine is operated at excess exhaust temperatures, engine  deterioration occurs. Since the EGT temperature is set by the  EGT temperature gauge, it is imperative that it is accurate.  Excessive engine speed can cause premature engine wear  and, if extreme, can cause engine failure. One older type of calibration test unit used to analyze the  turbine engine is the jetcal analyzer.  [Figure 10-77]  A  jetcal analyzer is a portable instrument made of aluminum,  stainless steel, and plastic. The major components of  the analyzer are the thermocouple, rpm, EGT indicator,  resistance, and insulation check circuits, as well as the  potentiometer, temperature regulators, meters, switches, and  all the necessary cables, probes, and adapters for performing  all tests.  Many different types of analyzers are used each with its own  function, including onboard systems that use computers to  test aircraft systems. Depending upon the specific analyzer  used, procedures vary somewhat, but the basic test are  outlined here. Always refer to the specific instructions  associated with the analyzer being used.  Most analyzers may be used to: 1.  Functionally check the aircraft EGT system for error,  without running the engine or disconnecting the  wiring. 2.  Check individual thermocouples before placement in  a parallel harness. 3.  Check each engine thermocouple in a parallel harness  for continuity. Turboprop Operation Turbine Engine Analyzer Uses Turbine Engine Calibration and Testing Troubleshooting Turbine Engines Troubleshooting Procedures for Turboprop Engines 10-60