ATE 258
To provide for engine operation under various loads and at different engine speeds, each carburetor has six systems:
1. Main metering 2. Idling 3. Accelerating 4. Mixture control 5. Idle cutoff 6. Power enrichment or economizer
The engine develops maximum power with a mixture of approximately __ parts of air and __ part of gasoline by weight.
12 : 1
______ fan engines take the fan airflow and direct it through closed ducts along the engine. Then, it flows into a common exhaust nozzle.
Ducted
When the velocity of the exhaust gases at the nozzle opening becomes _______, the flow passes only at this speed—it does not increase or decrease.
Mach 1
___________ blockage is accomplished by placing a removable obstruction in the exhaust gas stream, usually somewhat to the rear of the nozzle.
Mechanical
______________________ systems were more prone to vapor lock.
Older gravity-feed
When a turbocharger or a turbosupercharger system is included, the engine exhaust system operates under greatly __________ pressure and temperature conditions.
increased
The _________ _________ is a hydromechanical device employing a closed feed system from the fuel pump to the discharge nozzle
injection carburetor
Most thrust reverser systems can be divided into two categories: ____________-blockage and ___________-blockage.
mechanical, aerodynamic
A ________ ____ is really a certain size hole that the fuel passes through
metering jet
The terms afterburning and thrust augmentation generally pertain to _________ _________ ___________
military engine applications.
When performing maintenance on exhaust systems, _____ use galvanized or zinc-plated tools on the exhaust system
never
Cowl flaps are used mostly with:
older aircraft and radial engine installations.
The ________ section consists of a fuel diaphragm that opposes the air metering force.
regulator
The purpose in leaning is to ____ ____. Air is free and available in limitless quantities
save fuel
The air measuring unit is the _______, which makes use of a basic law of physics: as the velocity of a gas or liquid increases, the pressure decreases.
venturi
The fuel must be raised in the discharge nozzle to a level at which it discharges into the airstream. To accomplish this, a pressure differential of ________ "Hg is required.
0.5
The large surplus of air cools the hot sections of the engine to acceptable temperatures ranging from ___________ to _________
1,500° to 2,100 °F.
A float-type carburetor consists essentially of six subsystems that control the quantity of fuel discharged in relation to the flow of air delivered to the engine cylinders.
1. Float chamber mechanism system 2. Main metering system 3. Idling system 4. Mixture control system 5. Accelerating system 6. Economizer system
Excessive heat is undesirable in any internal combustion engine for three principal reasons:
1. It affects the behavior of the combustion of the fuel/ air charge. 2. It weakens and shortens the life of engine parts. 3. It impairs lubrication.
The cowling performs two functions:
1. It streamlines the bulky engine to reduce drag. 2. It forms an envelope around the engine that forces air to pass around and between the cylinders, absorbing the heat dissipated by the cylinder fins.
The venturi performs three functions:
1. Proportions the fuel/air mixture 2. Decreases the pressure at the discharge nozzle 3. Limits the airflow at full throttle
Turboprop exhaust nozzles provide small amounts of thrust (__-__ percent) but are mainly used to discharge the exhaust gases from the aircraft.
10-15
From a chemist's point of view, the perfect mixture for combustion of fuel and air would be 0.067 pounds of fuel to 1 pound of air (mixture ratio of __:_). The scientist calls this chemically correct combination a stoichiometric mixture (pronounced stoy-key-o-metric).
15:1
Through the use of a converging nozzle, the exhaust gases increase in velocity before they are discharged from the exhaust nozzle. Increasing the velocity of the gases increases their momentum and increases the thrust produced __-__ percent total thrust.
20-15
__________ systems are not used much on modern aircraft
Augmentor
______ ____ around an exhaust gasket shows the gasket has failed. The exhaust system should be inspected very thoroughly.
Black soot
reduces vapor lock and keeps the fuel in the lines to the engine-driven pump under pressure.
Booster Pump
____________ drain almost potential leaks overboard to prevent fluids from building up in the nacelle
Case drains
__________________________ are frequently provided around the exterior of the engine to permit the entrance of air to cool the turbine case, the bearings, and the turbine nozzle.
Cooling-air inlets
______ is a kerosene-based fuel that is clear to straw in color.
Jet A
The engine compartment frequently is divided into two sections:
The forward section is referred to as the cold section and the aft section (turbine) is referred to as the hot section.
________ _________ is the ability of an aircraft's main engines to direct thrust other than parallel to the vehicle's longitudinal axis
Thrust vectoring (Example: Vertical takeoff)
contains fiberglass as the low conductance material and aluminum foil as the radiation shield.
Turbine Engine Insulation Blankets
______ installed in the augmentors control the volume of air. These _____ are usually left in the trail position to permit maximum flow.
Vanes
Air bled into the main metering fuel system decreases the fuel density and destroys surface tension. This results in better vaporization and control of fuel discharge, especially at lower engine speeds.
a small air bleed is bled into the fuel nozzle slightly below the fuel level.
When the throttle valve is opened quickly, a large volume of air rushes through the air passage of the carburetor; the amount of fuel that is mixed with the air is less than normal due to the slow response rate of the main metering system. As a result, after a quick opening of the throttle, the fuel/air mixture leans out momentarily. This can cause the engine to accelerate slowly or stumble as it tries to accelerate. To overcome this tendency, the carburetor is equipped with a small fuel pump called an ________________ _____
accelerating pump
In the __________ blockage type of thrust reverser, used mainly with unducted turbofan engines, only fan air is used to slow the aircraft. A modern aerodynamic thrust reverser system consist of a translating cowl, blocker doors, and cascade vanes that redirect the fan airflow to slow the aircraft.
aerodynamic
in a pressure carburater system the discharge nozzle is.......
after the throttle valve
________ to the cylinders is regulated and controls the power output of the engine.
airflow
On a typical 18-cylinder radial engine, two exhaust assemblies and two _______ assemblies are used.
augmentor (This system is only used with older aircraft that generally use radial engines.)
Some aircraft use __________ to provide additional cooling airflow.
augmentors
many carburetors have _________ ________ _________ so that the fuel/air ratio, once it is selected, does not change with variations in air density.
automatic mixture controls
If the mixture is excessively lean, the engine may __________ through the induction system or stop completely.
backfire (Backfire results from slow burning of the lean mixture.)
The thermocouple end that connects to the cylinder is either the _________ or ________ type.
bayonet, gasket
The level of fuel in the float chamber is kept nearly constant by means of a float-operated needle valve and a seat. The needle seat is usually made of _________.
bronze
The airflow to the engine is controlled by the ___________ or fuel/air control unit.
carburetor
Sufficient flow to maintain Mach 1 at the nozzle opening and have extra flow (flow that is being restricted by the opening) creates what is called a ______ _____.
choked nozzle
A common cause of malfunction is ______ _______ in the wastegate unit causing erratic system operation.
coke deposits (carbon buildup) Excessive deposit buildups may cause the wastegate valve to stick in the "closed" position, causing an overboost condition.
Although the ___________ system raises the back pressure of the exhaust system, the gain in horsepower from turbosupercharging more than offsets the loss in horsepower that results from increased back pressure.
collector
The _________ exhaust system is used on most large Non supercharged engines and on all turbosupercharger engines and installations on which it would improve nacelle streamlining or provide easier maintenance in the nacelle area.
collector
The advantage of a _____________-__________ nozzle is greatest at high Mach numbers because of the resulting higher pressure ratio across the engine exhaust nozzle.
convergent-divergent
This type of nozzle is generally used on very high-speed aerospace vehicles.
convergent-divergent
Whenever the engine pressure ratio is high enough to produce exhaust gas velocities which might exceed Mach 1 at the engine exhaust nozzle, more thrust can be gained by using a ____________-_________ type of nozzle
convergent-divergent
The very first part of the exhaust nozzle and the exhaust plug form a divergent duct to reduce turbulence in the airflow, then the exhaust gases flow into the convergent component of the exhaust nozzle where the flow is restricted by a smaller outlet opening.
converging exhaust nozzle
The noise suppressors in current use are either of the __________-_________ type, or the _____-_____ type.
corrugated-perimeter, multi-tube
The most common means of controlling cooling is the use of _____ _______.
cowl flaps
Ceramic coated stacks should be cleaned by ____________ only
degreasing
Turboshaft engines in helicopters can have an exhaust nozzle that forms a __________ duct.
divergent
An __________ is essentially a valve that is closed at throttle settings below approximately 60-70 percent of rated power. This system, like the accelerating system, is operated by the throttle control.
economizer
The power enrichment system is sometimes called an ___________ or a power compensator
economizer
Many engines use an interactive system that senses engine parameters and feeds the information to the onboard computer (___________ _________ _________).
electronic engine control
Adjusting the area of the ________ __________ changes both the engine performance and the exhaust gas temperature.
exhaust nozzle
Turbine powerplants can be divided into primary zones that are isolated from each other by ______ ________ and ______.
fireproof bulkheads and seals
The characteristics of a given mixture can be measured in terms of ______ _______ and ___________ temperature
flame speed, combustion
An exhaust leak is indicated by a ____________________ streak on the pipes in the area of the leak.
flat gray or a sooty black
The ______________, or bowl, serves as a reservoir for fuel in the carburetor
float chamber
If fuel is found leaking from the discharge nozzle of the carburetor when the engine is not running, the most likely cause is that the ______ _____ ______ and _______ is leaking and needs to be replaced.
float needle valve and seat
The LL stands for low lead although it contains ____ times the lead of 80 octane AVGAS
four
Approximately ____ of all muffler and heat exchanger failures can be traced to cracks or ruptures in the heat exchanger surfaces used for cabin and carburetor heat sources.
half
The bayonet or gasket of the thermocouple is inserted or installed on the ________ cylinder of the engine, as determined in the block test.
hottest
As soon as the throttle is closed far enough to stop the spray from the main discharge nozzle, fuel flows out the idling jet.
idling jet
erosion and carburization caused by the extreme thermal conditions are the primary causes of ________ failures.
internal
Exhaust system parts should never be marked with a _____ pencil.
lead
at cruising speeds, a _____ mixture is desirable for economy reasons
lean
The secondary air passing through the engine cools the combustion-chamber __________
liners
Coke deposit buildup in the turbo itself causes a gradual loss of power in flight and _____ manifold pressure reading prior to takeoff.
low
The ___________ _______ system supplies fuel to the engine at all speeds above idling
main metering
On float-type carburetors, two types of purely manual or cockpit controllable devices are in general use for controlling fuel/air mixtures, the _____ type and the _____________ type
needle, back-suction
Excessive deposit buildups may cause the wastegate valve to stick in the "closed" position, causing an ___________ condition.
overboost
The thrust reverser system consists of several components that move either the clam shell doors or the blocker door and translating cowl. Actuating power is generally ___________ or __________ and uses gearboxes, flexdrives, screwjacks, control valves, and air or hydraulic motors to deploy or stow the thrust reverser systems.
pneumatic, hydraulic
It is this _________ _________, or metering force, that causes fuel to flow from the discharge nozzle.
pressure difference
The extra flow builds up pressure in the nozzle, which is sometimes called _________ _______.
pressure thrust
For an engine to develop maximum power at full throttle, the fuel mixture must be _______ than for cruise.
richer
Less air due to altitude tends to make carburetors run _______ at altitude than at ground level
richer
The reciprocating engine exhaust system is fundamentally a __________ system that collects and disposes of the high temperature, noxious gases being discharged by the engine.
scavenging
The _______ _______ exhaust system is generally used on nonsupercharged engines and low-powered engines where noise level is not too objectionable.
short stack
A measure of the economical use of fuel is called ______ _________ ___________
specific fuel consumption (SFC)
On some turboprop aircraft, an exhaust duct is often referred to as a ________, although the duct itself is essentially a simple, stainless steel, conical or cylindrical pipe.
tailpipe
The basic parts of a fuel system include:
tanks, boost pumps, lines, selector valves, strainers, engine-driven pumps, and pressure gauges
If too much of the cooling fin area is broken off:
the cylinder cannot cool properly, and a hotspot develops.
The fuel discharged by this system is determined by:
the drop in pressure in the venturi throat
The engine cooling system of most reciprocating engines usually consists of:
the engine cowling, cylinder baffles, cylinder fins, and some use a type of cowl flaps. In addition to these major units, there are also some temperature-indicating systems, such as cylinder head temperature, oil temperature, and exhaust gas temperature.
The three general causes of vapor lock are:
the lowering of the pressure on the fuel, high fuel temperatures, and excessive fuel turbulence.
There are two general types of exhaust systems in use on reciprocating aircraft engines:
the short stack (open) system and the collector system.
The exhaust gas temperature indicator consists of a ___________ placed in the exhaust stream just after the cylinder port.
thermocouple
simple venturi is a passageway or tube in which there is a narrow portion called the _______.
throat
A ________ _________ must not have any adverse effect on engine operation either deployed or stowed. Generally, there is an indication in the flight deck with regard to the status of the reverser system.
thrust reverser
The thermocouple consists of:
two dissimilar metals, generally constantan and iron, connected by wiring to an indicating system.
The _________ fan has two nozzles, one for the fan airflow and one for the core airflow. These both flow to ambient air separate from each other and have separate nozzles.
unducted
