Induction, Cooling, Exhaust Flashcards
What are some indications of a leak in the induction system?
Leaks in the induction system can cause an engine to idle improperly, run rough, or overheat. In severe cases, the engine may not start or may cut out. It also could fail to develop full power.
What are some inspection procedures for ice control systems?
Controlling ice in the induction system of a reciprocating aircraft engine is primarily accomplished by raising the temperature of the induction air. This is done with what is known as carburetor heat. The air intake ducting is equipped with a valve controlled from the flight deck. Inspection procedures for this ice control system must include the integrity and free motion of this valve and its control cable. It must fully open and fully close to ensure safe operation. Follow the manufacturer’s instruction for lubricating the cable and valve hinge.
Describe the automatic and manual operation of the alternate air valve.
An engine may be fitted with an alternate induction system air inlet that incorporates a dust filter. This type of air filter system normally consists of a filter element and a door that is electrically operated from the flight deck. The pilot opens the door manually with the electric actuator when operating in dusty conditions. Some installations have a spring loaded filter door that automatically opens when the filter is excessively restricted. This prevents the air from being cut off when the filter is clogged with dirt or ice.
What can be done to troubleshoot ice control systems?
An ice control system like carburetor heat is very simple and relatively trouble free. Regular inspection of the ducting, valve, and operating mechanism should reveal any operational problems. When the carburetor heat valve is fully opened, it should only be a matter of a few minutes until the ice is cleared. If this is reported as not being the case, then, if application of the heat was timely, it is likely that the valve is not opening all the way. Check the cable and the valve itself for unrestricted movement and full travel. Any report of low power could be the result of the carburetor heat valve not closing fully. Again, inspect the cable and the valve for proper operation.
Explain how a carburetor heat system operates and the procedure to verify proper operation.
Eliminating ice in the induction system of a reciprocating engine is primarily accomplished by raising the temperature of the induction air. This is done with a carburetor heat system. The air intake ducting is equipped with a valve controlled from the flight deck. When opened, warm air that has been circulated around the exhaust system is diverted into the carburetor.
Inspection procedure for this ice control system must include the integrity and free motion of this valve and its control cable. It must fully open and fully close to ensure safe operation. If running up the engine on the ground, application of full carburetor heat should be accompanied by a reduction in manifold pressure because the intake air becomes less dense.
What is the cause and effect of one kind of induction system ice?
Fuel evaporation ice is formed because of the decrease in temperature resulting from the evaporation of fuel when it is introduced into the intake airstream at the fuel discharge nozzle. The temperature of the air and components around the evaporating fuel reduces to below freezing and any moisture present becomes ice that settles on the discharge nozzle and nearby structure. This ice builds up and can interfere with fuel flow, affect mixture distribution and lower manifold pressure.
Explain the function and operation of one type of supercharging.
A turbosupercharger or turbocharger system functions to increase manifold pressure on a reciprocating engine. It is an externally driven supercharger that compresses the intake air before it is delivered to the fuel metering device. Engine exhaust gases are directed against a turbine that drives an independent impeller mounted on the same shaft. The impeller compresses the intake air and sends it to the fuel metering device. A controller modulates a wastegate valve in the exhaust stream. The amount of gases directed against the turbine is varied by the position of the wastegate. Thus, the amount of intake air compression is controlled which directly affects the power output of the engine.
Name some indicators of an exhaust leak or methods of detecting exhaust leaks.
An exhaust leak is indicated by a flat gray or sooty black streak on the pipes near the leak. Misaligned exhaust system pipes or components are an indicator that a leak may exist.
Explain thrust reverser system operation and some of the main components.
Without any adverse effect of the engine, a thrust reverser system prevents continued forward thrust of the engine by not allowing the engine fan and/or exhaust airflow to flow aft. Typically, a mechanical blockage or redirection of the air occurs through the use of hydraulic or pneumatic power. When the thrust lever on the flight deck is moved aft of idle, and the aircraft has weight on wheels, a control valve diverts the power to a motor. Through the use of jackscrews, flex-drives, and gear boxes, the reverser mechanism unlocks and deploys to change the direction of the engine outflow. When the aircraft has slowed, the power lever is moved forward and the thrust reverser mechanism stows.
Explain the differences between a cascade and a mechanical blockage door thrust reverser.
The two types of thrust reverser systems are the mechanical blockage and the aerodynamic blockage systems. The mechanical blockage system places a removable obstruction in the exhaust gas stream. This is usually done rear of the exhaust nozzle. The exhaust gases therefore are mechanically blocked and diverted at a suitable angle in the reverse direction. The aerodynamic blockage type of thrust reverser is used on turbofan engines. Since 80 percent of the forward thrust comes from the fan of a turbofan engine, the aerodynamic thrust reverser redirects the fan air to slow the aircraft. Typically, a translating cowl slides aft and as it does so, blocking panels are deployed into the fan airstream. These redirect the air through cascade vanes that further direct the air forward to slow the aircraft. Since the aerodynamic thrust reverser system deflects fan air, it does not have to be particularly resistant to heat.
What are the hazards of exhaust system failure?
Any exhaust system failure should be regarded as a severe hazard. Depending on the location and type of failure, it can result in carbon monoxide poisoning of crew and passengers, partial or complete loss of engine power, or an aircraft fire.
What are the effects of using improper materials to mark on exhaust system components?
Exhaust systems marked with a lead pencils as well as the use of galvanized or zinc-plated tools must be avoided. The lead, zinc, or galvanized mark is absorbed by the metal of the exhaust system when heated. This creates a distinct change in the molecular structure of the metal. This change softens the metal in the area of the mark causing cracks and eventual failure.
What is the function and operation of a turbine engine exhaust nozzle?
A turbine engine exhaust nozzle directs the exhaust gases. While doing so, it aids in the extraction of power from the engine. A converging nozzle will speed up the gases and extract more thrust. A divergent nozzle will slow the gases and reduce thrust. A nozzle can also help straighten the gases when they exit the turbine or reduce turbulence.
