POWERPLANT PPT7

ACCESSORY SECTION ALLER REDUCTION GEARS

Accessory Rear Section

is of cast construction and the material may be either aluminum alloy, which is used most widely, or magnesium, which has been used to some extent.

Accessory Drive Shaft

are mounted in suitable drive arrangements that are carried out to the accessory mounting pads. In this manner, the various gear ratios can be arranged to give the proper drive speed to magnetos, pumps, and other accessories to obtain correct timing or functioning,

Carburetor

It is a device that mixes air and fuel for internal combustion engines to give proper fuel-air ratio

Float-Type Carburetors and Pressure-Type Carburetors

Two Categories of aircraft carburetors

Venturi

A narrow throat in the carburetor and it creates an area of low pressure

Float-type Carburetor

Acquires its name from a float that rests on fuel within the float chamber. This meters the amount of fuel entering into the carburetor, depending upon the position of the float, which is controlled by the level of fuel in the float chamber.

Needle

It is attached to the float which opens and closes an opening at the bottom of the carburetor bowl

Closes

When the level of the fuel forces that float to rise, the needle valve ________the fuel opening and shuts off the fuel flow of the carburetor.

Throttle Valve or Butterfly Valve

It is controlled by the throttle in the flight deck as it regulates the flow of the fuel-air mixture to the combustion chambers.

Fuel-air Mixture

The blend of fuel and air is routed to the combustion chambers to be burned

Discharge Nozzle

Fuel is forced through this section into the venturi by greater atmospheric pressure in the float chamber

Air inlet

This is where air enters in a carburetor

Air bleed

Allows air to be mixed with fuel being drawn out of the discharge nozzle to decrease fuel density and promote fuel vaporization

Mixture Needle

Controls fuel to the discharge nozzle. Its position can be adjusted using the mixture controls .

Carburetor Icing

This is prone in higher altitude due to higher temperatures which causes fuel and air mixture will have an icing formation due to the temperatures affecting the metal encasing the fuel. This will disrupt the flow possibly leading to reduction of power

Carb Heat

Instead of getting ram air going through the intake to cool the engines, activating this will instead utilize the heat of the engine towards the carburetor as means to melt the icing formations in the carburetor. Simply, this is a counter for carbureting Icing.

Pressure-Type Carburetors

Delivers fuel under pressure by a fuel pump. Discharges fuel into the airstream at a pressure well above atmospheric pressure. This results in better vaporization and permits the discharge of fuel into the airstream on the engine side of the throttle valve.

Offset

With the discharge nozzle in this position fuel vaporization takes place after the air has passed through the throttle valve and at a point where the drop in temperature is________ by heat from the engine

Negligible

The effect of rapid maneuvers and rough air on the pressure-type carburetors are _______, since their fuel chambers remain filled under all operating conditions

Volume airflow

Determines the rate of fuel discharge

Magneto

Uses a permanent magnet to generate an electrical current completely independent of the aircraft’s electrical system

High voltage

The magneto generates sufficiently _____________ to jump a spark across the spark plug gap in each cylinder. The system begins to fire when the starter is engaged and the crankshaft begins to turn. It continues to operate whenever the crankshaft is rotating .

Dual Ignition System

Most standard certificated aircraft incorporate a _________________ with two individual magnetos, separate sets of wires, and spark plugs to increase reliability of the ignition system. Each magneto operates independently to fire one of the two spark plugs in each cylinder.

True

\[ T/F \] The firing of two spark plugs improves combustion of the fuel-air mixture and results in a slightly higher power output. If one of the magnetos fails, the other is unaffected. The engine continues to operate normally, although a slight decrease in engine power can be expected. The same is true if one of the two spark plugs in a cylinder fails.

Starter Motor

It is a device used to rotate an internal-combustion engine so as to initiate the engine’s operation under its own power . It engages the aircraft flywheel, rotating the engine at a speed that allows the engine to start and maintain operation

Engine-Driven Alternators or Generators

Supply electric current to the electrical system. They also maintain a sufficient electrical charge in the battery.

Electrical Energy

It is stored in a battery which provides a source of electrical power for starting the engine and a limited supply of electrical power for use in the event the alternator or generator fails

Spur-Type Gears

are generally used to drive the heavier loaded accessories or those requiring the least play or backlash in the gear train

Bevel-Type Gears

Angular location of short stub shafts leading to the various accessory mounting pads. On opposed, reciprocating engines, the accessory gear trains are usually simple arrangements

Propeller Reduction Gear System

Permits a propeller to turn slower than the engine. this allows an engine to turn at a relatively fast speed and a propeller to turn at a more efficient slower speed

Spur Gears, Planetary Gears or a combination of the two

Reduction gear systems currently used on aircraft engines utilize _______, _______, or _______

True

\[ T/F \]

As a general rule, the faster an engine turns, the more power it produces; however, this same rule does not apply to propellers.

False

\[ T/F\] As a propeller blade tip approaches the speed of sound, the propeller can still efficiently convert the power produced by an engine into thrust.

Specific Speed

To achieve maximum efficiency, most propeller must be operated with this.Therefore, to allow an engine to run at the speed required to produce its maximum rated power output while, at the same time, maintain a reasonable propeller speed, some high-powered engines must use a propeller reduc­tion gear system.

Spur Gear

have their teeth cut straight across their circumfer­ence and can be either external or internal.

Two

The sim­plest type of reduction gearing consists of ________ external tooth spur gears, one small gear on an engine crankshaft and one larger gear on the pro­peller shaft.

size; larger; slower

When configure in spur gears, the amount of reduction is based primarily on the ______ of the propeller shaft gear. The ______ the gear, the ______ the propeller turns.

Opposite; Gyroscope; Torsional

This reduction system does have some disadvantages. for example, when using two extremal tooth spur gears, the propeller turns ______ the crankshaft. Furthermore, since the propeller shaft is off-center from the engine crankshaft, the propeller acts like a ______ and places severe ______ loads on the engine case

1:2

With a gear reduction system that uses two externally driven spur gears, the amount of reduction is determined by the ratio of the gear teeth. For example, if the drive gear has 25 teeth and the driven gear has 50 teeth, a ratio of ______ exists and the propeller turns at one half the crankshaft speed.

Internal-Tooth Spur Gear; External-Tooth Spur Gear

One way to overcome some of the drawbacks of a simple spur gear arrangements is to use an ____________ on the propeller shaft and an ____________ on the crankshaft

False

\[ T/F \] In the spur gears, allowing the propeller to turn in the opposite direction as the engine, this arrangement keeps the propeller shaft more closely aligned with the crankshaft, thereby eliminating much of the stress placed on the crankcase

One; Same

With a gear reduction system that uses _____ internal-tooth gear and _____ external-tooth gear the propeller and crankshaft turn in the_____ direction and are more closely aligned

Quill Shaft

is a hardened steel shaft that is splined on both ends and installed between two gears, or shafts, to absorb torsional vibration.

Vibration

Whenever a reduction gear is used that does not keep the propeller shaft perfectly aligned with the crankshaft, additional ________ is induced into an engine. To help minimize this, some engines use a quill shaft between the crankshaft and propeller shaft.

Propeller Shaft and Crankshaft

A quill shaft minimizes torsional vibration between the ________ and ________

Planetary Reduction Gears

Keep the propeller shaft and crankshaft perfectly aligned to reduce vibration

Planetary Gears

In a planetary gear system, the propeller shaft is attached to a housing which contains several small gears called __________. These are used on some horizontally opposed engines, as well as radial or turboprop engines.

Sun Gear and a Ring or Bell Gear

The planetary gears rotate between a _____ and _____. The crankshaft drives either one of this depending on the individual installation

Planetary Gear Reduction System

keeps the propeller shaft aligned with the crankshaft, transmit power with a minimum of weight and space, and keeps the propeller’s direction of rotation the same as the engine

Planetary Gear Spider

In a planetary gear reduction system, the propeller is attached to the _________ and the crankshaft turns either the sun gear or the ring gear

Gear Ratio=Teeth On the Ring Gear + Teeth on the Sun Gear/ Teeth on the Ring Gear

The reduction rate that a particular gearing arrangements achieves is found by the formula?

Propeller Shaft

It is a shaft that carries a propeller at its end and carries and transmits power from engine to propeller.

Tapered Propeller Shaft

Were used on most of the early, low-powered engines. The shaft tapers or gets smaller in diameter, as you move out toward the end of the shaft

Splined Propeller Shaft

Most high power radial engines utilize this type of propeller shaft

Spline

Is a rectangular groove that is machined into the propeller shaft. Most of this have a master spline that is approximately twice the size of any other spline.

Master Spline

Assures that a propeller is attached to a propeller shaft specific way so that vibration is kept minimum

Flanged Propeller Shaft

Most modern horizontally opposed aircraft engines use this type of propeller shaft

Flat Flange

With the flanged propeller shaft, this is forged directly onto the end of a crankshaft and a propeller is bolted to the flange.

True

\[ T/F\] To provide additional support for the propeller, most flanged propeller shafts incorporate a short shaft forward of the flange and a series of studs around the flange circumference.

Mixture Lever

This allows for fuel to be regulated properly

Rich mixture

Greater parts of fuel versus the air. For example two parts of fuel and one part of air. usually used at lower altitudes or at sea levels

Lean Mixture

Less parts of fuel compared to air. Starts when altitude increases at 3000 ft.