3H Airplane Systems - Powerplant Flashcards
- Describe how each of the following engine gauges work.
Oil Temperature—Electrically powered from the aircraft electrical system.
Oil Pressure—A direct-pressure oil line from the engine delivers oil at engine operating pressure to the gauge.
Cylinder Head Temperature—Electrically powered from the aircraft electrical system.
Tachometer—Engine-driven mechanically.
Manifold pressure—Direct reading of induction air manifold pressure in inches of mercury.
Fuel pressure—Indicates fuel pressure to the carburetor.
- What type of engine does this aircraft have?
The airplane is powered by an engine manufactured by Avco-Lycoming, rated at 180 horsepower at 2,700 rpm. It may be described as follows:
a. Normally aspirated
b. Direct-drive
c. Air-cooled
d. Horizontally-opposed
e. Carburetor-equipped
f. Four-cylinder
g. 361-cubic-inch displacement
- What four strokes must occur in each cylinder of a typical four-stroke engine in order for it to produce full power? (FAA-H-8083-25)
The four strokes are:
Intake—fuel mixture is drawn into cylinder by downward stroke.
Compression—mixture is compressed by upward stroke.
Power—spark ignites mixture forcing piston downward and producing power.
Exhaust—burned gases pushed out of cylinder by upward stroke.
- What does the carburetor do? (FAA-H-8083-25)
Carburetion may be defined as the process of mixing fuel and air in the correct proportions to form a combustible mixture. The carburetor vaporizes liquid fuel into small particles and then mixes it with air. It measures the airflow and meters fuel accordingly.
- How does the carburetor heat system work? (AFM)
A carburetor heat valve, controlled by the pilot, allows unfiltered, heated air from a shroud located around an exhaust riser or muffler to be directed to the induction air manifold prior to the carburetor. Carburetor heat should be used anytime suspected or known carburetor icing conditions exist.
- What is fuel injection? (FAA-H-8083-25)
Fuel injectors have replaced carburetors in some airplanes. In a fuel injection system, the fuel is normally injected into the system either directly into the cylinders or just ahead of the intake valves; whereas in a carbureted system, the fuel enters the airstream at the throttle valve. There are several types of fuel injection systems in use today, and though there are variations in design, the operational methods are generally simple. Most designs incorporate an engine-driven fuel pump, fuel/air control unit, fuel manifold valve, discharge nozzles, auxiliary fuel pump, and fuel pressure/flow indicators.
- What are some advantages of fuel injection? (FAA-H-8083-25)
a. Reduction in evaporative icing
b. Better fuel flow
c. Faster throttle response
d. Precise control of mixture
e. Better fuel distribution
f. Easier cold weather starts
- Are there any disadvantages associated with fuel-injected engines? (FAA-H-8083-25)
a. Difficulty in starting a hot engine
b. Vapor locks during ground operations on hot days
c. Problems associated with restarting an engine that quits because of fuel starvation
- What is an alternate induction air system and when is it used? (FAA-H-8083-3)
It is a device which opens, either automatically or manually, to allow induction airflow to continue should the primary induction air opening become blocked. In the event of impact ice accumulating over normal engine air induction sources, alternate air should be selected. On some fuel injected engines, an alternate air source is automatically activated with blockage of the normal air source.
- What is the condition known as vapor lock? (FAA-H-8083-32)
Fuel-injected engines are more susceptible to vapor lock during ground operations on hot days. Vapor lock occurs when fuel vapor and/or air collect in different sections of the fuel system. The fuel may actually boil in the lines, creating a condition which interferes with the normal operation of valves, pumps, etc. Other causes of vapor lock can be low fuel pressure and excessive fuel turbulence.
- What does the throttle do? (FAA-H-8083-25)
The throttle allows the pilot to manually control the amount of fuel/air charge entering the cylinders. This in turn regulates the engine manifold pressure.
- What does the mixture control do? (FAA-H-8083-25)
It regulates the fuel-to-air ratio. Most airplane engines incorporate a device called a mixture control, by which the fuel/air ratio can be controlled by the pilot during flight. The purpose of a mixture control is to prevent the mixture from becoming too rich at high altitudes, due to decreasing air density. Leaning the mixture during cross-country flights conserves fuel and provides optimum power.
- What are turbochargers? (FAA-H-8083-25)
Higher performance aircraft typically operate at higher altitudes where air density is substantially less. The decrease in air density as altitude increases results in a decreased power output of an unsupercharged engine. By compressing the thin air by means of a supercharger, the turbocharged engine will maintain the preset power as altitude is increased. The turbocharger consists of a compressor to provide pressurized air to the engine, and a turbine driven by exhaust gases of the engine to drive the compressor.
- What are cowl flaps? (FAA-H-8083-32)
Cowl flaps are located on the engine cowling and allow the pilot to control the operating temperature of the engine by regulating the amount of air circulating within the engine compartment. Cowl flaps may be manually or electrically activated and usually allow for a variety of flap positions.
- When are cowl flaps used? (FAA-H-8083-32)
a. Normally the cowl flaps will be in the “open” position in the following operations:
• During starting of the engine
• While taxiing
• During takeoff and high-power climb operation
The cowl flaps may be adjusted in cruise flight for the appropriate cylinder head temperature.
b. The cowl flaps should be in the “closed” position in the following operations:
• During extended let-downs
• Anytime excessive cooling is a possibility (i.e., approach to landing, engine-out practice, etc.)
