Planetary production gears Fuel nozzle Second-stage centrifugal compressor First-stage centrifugal compressor Air inlet Igniter Three stage axial turbine Reverse-flow annular combustion chamber Exhaust outlet Figure 14-2.  Fixed shaft turboprop engine. forward thrust. The power lever is also used to provide  reverse thrust. The condition lever sets the desired engine rpm  within narrow range between that appropriate for ground  operations and flight. Powerplant instrumentation in a fixed shaft turboprop  engine typically consists of the following basic indicators.  [Figure 14-4] In the fixed shaft constant-speed engine, the engine rpm  may be varied within a narrow range of 96 percent to 100  percent. During ground operation, the rpm may be reduced  to 70 percent. In flight, the engine operates at a constant  speed that is maintained by the governing section of the  propeller. Power changes are made by increasing fuel flow  and propeller blade angle rather than engine speed. An  increase in fuel flow causes an increase in temperature and  a corresponding increase in energy available to the turbine.  The turbine absorbs more energy and transmits it to the  propeller in the form of torque. The increased torque forces  the propeller blade angle to be increased to maintain the  constant speed. Turbine temperature is a very important  factor to be considered in power production. It is directly  related to fuel flow and thus to the power produced. It must  be limited because of strength and durability of the material  in the combustion and turbine section. The control system  schedules fuel flow to produce specific temperatures and to  limit those temperatures so that the temperature tolerances  of the combustion and turbine sections are not exceeded. The  engine is designed to operate for its entire life at 100 percent.  All of its components, such as compressors and turbines, are  most efficient when operated at or near the rpm design point. Powerplant (engine and propeller) control is achieved by  means of a power lever and a condition lever for each engine.  [Figure 14-3]  There is no mixture control and/or rpm lever  as found on piston-engine airplanes. On the fixed shaft constant-speed turboprop engine, the  power lever is advanced or retarded to increase or decrease  Figure 14-3.  Powerplant controls—fixed shaft turboprop engine. 14-4 • Torque or horsepower • Interturbine temperature (ITT) • Fuel flow •  RPM GA Power levers Condition levers