Chapter 5- Induction Systems Flashcards
The typical induction system on a normally aspirated engine consists of four major components. What are they?
- Air Intake
- Induction air filter
- Fuel metering system
- Induction manifold
Name three types of filters used to clean incoming air.
- Paper Type
- Flock Type
- Polyurethane Foam
What are the three types of inducton system icing?
Fuel Evaporation Ice
Throttle Ice
Impact Ice
What is Fuel Evaporation Ice?
What are the optimum weather conditions for carburetor ice to exist?
Also known as Carburetor Ice
In a carburetor, as fuel is released into the airstream, it turns into a vapor and absorbs heat from the surrounding air. This can cause a drop in air temperature and in some cases, this loss of heat is enough to cause the moisture in the air to condense and freeze.
Optimum weather conditions for carburetor ice to exist when the outside air temperature is between 30 and 40 degrees F and the relative humidity is above 60%
What is Throttle Ice?
Throttle ice forms on the downstream side of a throttle, or butterfly valve, when it is ina partially closed position. Air flowing across and around the throttle valve creates an area of low pressure on the down-stream side. This has a cooling effect on the fuel/air mixtur, which can cause moisture to accumulate and freeze on the downstream side of the butterfly valve.
What is Impact Ice?
Impact ice is caused by visible moisture striking an aircraft and then freezing. The air intake and air filter are the areas most susceptible to impact icing.
What is the first indication of icing within the induction system is what?
Decrease in engine power
What are the disadvantages of Carb Ice?
- Excessive use increases the chance of dirt and foreign material entering the engine
- If placed in “hot” position on engine start-up, damage to a carburetor heat air box could result if the engine backfires
- Fuel/air mixture becomes richer and causes a noticible loss in power
- High intake air temperatures from carb heat can lead to detonation during high power settings
What position should the carb heat be left in when starting the engine?
Cold position
What are the sources for carb heat?
- Air inside a heater muff surrounding a hot exhaust pipe become heated then directed to a carburetor air box
- An carburetor air box alternate air supply that can draw air from the main intake or from inside the cowling
- Fuel-injected engines use an alternate air door that lets warm unfiltered air flow into the induction system
An engine-driven air pump that increases manifold pressure is called what?
Supercharger
A type of supercharger that has a single gear-driven impeller that increases the power produced by an engine at all altitudes is called what?
Single stage, single-speed supercharger
A single impeller that can be operated at two speeds is called what?
What are the names of the two speeds?
Single stage, two-speed supercharger
- Low Speeds - also known as a low blower setting has a impeller gear ratio of 8:1
- High Speeds - alos known as a high blower setting has a impeler gear ratio of 11:1
What powers a turbocharger?
Exhaust gases
The maximum altitude that a turbocharged engine is able to produce its rated horsepower under standard atmospheric conditions is called what?
Critical altitude
What is used to lube the bearing housing of a turbocharger and why?
The friction caused by high rotation speeds, exhaust gases flowing through the turbine, and the compression air intake all causes heat in the turbocharger so a continuous flow of engine oil must be poured through the bearing housing to cool and lubricate the bearings
A small heat exchanger that uses outside air to cool the hot compressed air before it enters the fuel metering device is called what?
Intercooler
A valve that controls the amount of exhaust gases that flow past a turbocharger turbine is called what?
A wastegate
What forces are used to open and close the wastegate?
- Manually through controls in the cockpit
- Automatically through either:
- A wastegate actuator that uses a spring to hold open the wastegate and oil pressure that closes the wastegate
- Absolute Pressure Control
- Pressure-Ratio Controller
A turbocharger system on an engine designed to maintain sea level engine performance from sea level up to their critical altitude is called what?
Sea level-boosted engines
What are the four units that permit automatic control in sea level-boosted engines?
- Exhaust bypass valve assembly
- Density controller
- Differential pressure controller
- Turbocharger
A spring tension pistion that closes the wategate valve with increased oil pressure and opens the wategate valve when oil pressure is released and also controlled by the density controller and differential pressure controller is called what?
Exhaust Bypass Valve Assembly
What regulates the bleed oil flow from the exhaust bypass valve assembly only during full throttle operations.
Density Controller
What regulates turbocharger output when sea level-boosted engines is operated at less than full throttle?
Differential Pressure Controller
Which controller controls boot-strapping?
Differential Pressure Controller
When a turbocharger system senses small changes in temperature or speed and continually changes the turbocharger output in attempt to establish equilibrium is called what?
Boot Strapping
What type of damage can overboosting cause?
It can cause damage to the turbocharger, intake manifold, pistons and cylinders
What is the term called when turbocharger controllers are not able to keep up with throttle movements which causes the manifold pressure to overshoot the desired value.
Overshoot
Aside from it’s primary function, what other aditional tasks can the turbocharger do?
Fuel atomizing
Cabin Pressurazation
Even fuel distribution
What is the meaning of P.R.T?
Power Recovery Turbine
A system which enables an engine to recover energy from the velocity of exhaust gases that would otherwise be lost.
When an air inlet duct recovers as much as possible total pressure from the free airstream before delivering it to the compresser is known as what?
Ram Recovery
What shape do subsonic inlets have?
A divergent shape
Pressure in increased and velocity is decreased
What are the two types of airflow that produce thrust?
Primary airflow
- responsible for 20-30% thrust
Secondary Airflow
- also known as bypass airflow and used for cooling
What are bellmouth inlets?
Convergent inlets designed specifically for obtaining high aerodynamic efficiency when stationary or in slow flight typically used on helicopters and slow moving aircrafts
What engine guage should you first check when troubleshooting?
Oil Pressure Guage
What two methods are used to boost manifold pressure?
Supercharger
Turbocharger
What are the three carberator inherent problems?
Prone to icing
uneven fuel distribution
uneven atomizing
