Aircraft towage. Starting process of aviation engines. (Topic 9)

Август 2, 2022

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Aircraft towage. Starting process of aviation engines. (Topic 9)

Содержание

2. 1. THE ORGANIZATION OF AIRCRAFT TOWING For good safety movement of the attendants on platform and
3. Tractors as a rule are applied to towing of airplanes. On a way of aircraft towing
4. The tow bar has the coupling device with a forward rack of the chassis of the
5. Recently universal carrier has found application, which has simplified process of towing. The light transitive crutches
6. The flight intercommunication is used for coordination of action of the tractor driver with the pilot
7. Towing of the plane with the help of a friction gear has a number of advantages,
8. At towing of an aircraft it is necessary to observe the following rules: towing of an
9. 2. STARTING PROCESS OF AVIATION ENGINES Aviation gas turbine engines and piston engines do not possess
10. ELECTRIC SYSTEMS OF START. There are three basic types of electric starter start of aircraft engines:
11. Step start is such start, during which the initial supply voltage of an electrostarter through the
12. One of the basic sources of power supplies for airplanes are air field mobile electrounits of
13. All modern airports receive the electric power from industrial three-phase alternating-current mains with voltage 380 V
14. At operation of power supply systems of an aircraft it is necessary to observe the following
15. AIR SYSTEM OF THE ENGINE START. The air system of start is applied on airplanes with
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1. THE ORGANIZATION OF AIRCRAFT TOWING
For good safety movement of the

attendants on platform and parking, economy of a resource of aviation engines and aviation fuel, and also protection of an environment against noise and pollution instead of taxiing the plane its towing is applied. However, towing increases aircraft staying in the airports that has an adverse effect on commercial speed of airtransportations which is the basic parameter describing efficiency of planes usage.
The increase in commercial speed increases flying time by one plane, accelerates delivery of passengers, mails, cargoes, etc. Hence, all positive parts connected to towing are necessary to use with the minimal loss for commercial speed of airtransportations.

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Tractors as a rule are applied to towing of airplanes. On

a way of aircraft towing tractors with towing adaptations, devices with a friction gear and with use of weight of the plane are applied.
The greatest distribution was found simple and reliable ways of aircraft towing with the help of machines - tractors which transfer drag force on the plane by means of tow bars - at movement of an aircraft by «forebody forward" and with use two sling of identical length at movement of an aircraft by «a tail unit forward».

Schopf aircraft towbar tug.

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The tow bar has the coupling device with a forward rack

of the chassis of the plane and a towing hook of the tractor. Thus it is carried out rigid coupling of the tractor with plane and transfer of drag force. At towing of an aircraft by «a tail unit forward» one end of everyone slings joins in special unit to racks of the basic chassis, and the second ends with the help of towing link are attached to a hook of the tractor. For improvement of maneuvering in this case, it is used manual carrier of a control which is attached with the help of pins to the forward rack of the chassis.

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Recently universal carrier has found application, which has simplified process of

towing. The light transitive crutches are jointed to forward rack of an aircraft. The complete set for different planes is transported in the tractor. They are connected also to the common for all planes carrier. It provides constant readiness of the tractor for towing of various types of airplanes. Now air field tractors such as БелАЗ-6411, БелАЗ-7421 КрАЗ-256 are applied. They are equipped with universal carriers and complete sets of transitive crutches.

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The flight intercommunication is used for coordination of action of the

tractor driver with the pilot or technician, carrying out control of an aircraft at towing.
Tractors should operate reliably at speeds of movement of 5 km/h and develop sufficient drag force on a hook. For reduction of wheelspin of the tractor the ballast is loaded into its body at the moment of breakaway from a place, the chain is put on wheels and sand blaster is mounted at each wheel.

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Towing of the plane with the help of a friction gear

has a number of advantages, namely: absence of a connecting link - carrier; small radius of turn of the plane at maneuvering; smooth breakaway of the plane from a place and soft braking. But these advantages are fair only at a dry air field covering that limits application of the given method.
The principle of action of the frictional device for towing the plane consists in transfer from it on a forward wheel of the plane chassis of the torque, sufficient for breakaway and movements of the plane. Such devices are applied, basically, for towing of light planes; they have found wide application abroad.

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At towing of an aircraft it is necessary to observe the

following rules:
towing of an aircraft is necessary to provide according to the operating instruction of the given type of the plane;
strictly carry out commands of responsible for towing which should be in sight the driver of the tractor and the person who are taking place in a cabin of the plane;
drivers of the tractors trained to the towing rules of corresponding types of planes are admitted to towing of an aircraft;
the tractors used for towing, should be equipped with means of radio communication, dimensional and flashing fires;
speed of towing should correspond to the instruction on towing of given type of plane;
Towing should be carried out without jerks and sharp turns, breakaway and stop is made smoothly.

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2. STARTING PROCESS OF AVIATION ENGINES
Aviation gas turbine engines and piston

engines do not possess the starting moment. Their start needs preliminary rotation of a rotor up to the certain frequency of rotation providing reliable submission, ignition of fuel and an output of the engine on an idle mode.
Process of preliminary rotation of a rotor of the aviation engine up to the set frequency of rotation (small gas) is called start of the engine. All operations of start and its control are automated. As ground means of automation of power supplies for start of aircraft engines electric and pneumatic devices are used.

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ELECTRIC SYSTEMS OF START.
There are three basic types of electric starter

start of aircraft engines: direct, step and smooth. They differ among themselves on character of change of a voltage and consumed by an electrostarter current during start.
The direct start is such start, during which the value of a supply voltage 24 V (28,5 V) of an electrostarter for whole cycle of start of an aircraft engine remains almost constant. Direct start is applied to aircraft engines which during start are consumed a small amount of the electric power.
As power supplies at direct start direct current generators, rectifiers with a voltage 28,5 V and storage batteries with a voltage 24 V are applied.

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Step start is such start, during which the initial supply voltage

of an electrostarter through the certain time interval is doubled (for example, from 24 V to 48 V) due to series connection of two independent current sources by their switching during start from parallel connection on series. Such system of start is called «System of start 24/48 V». It increases reliability of engine start, excludes sharp dynamic loadings on the coupling mechanism of a starter, raises efficiency of energy use of power supplies.
Smooth start is such start during which the value of a voltage supply of an electrostarter of an aircraft engine changes smoothly from 0 up to 70 V. Smooth start excludes occurrence of dynamic loadings in kinematics of an aircraft engine, provides an optimum mode of start, and reduces charges of the electric power. This system finds application at start of aircraft engines of heavy planes at which capacity of a starter makes some tens kilowatt.

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One of the basic sources of power supplies for airplanes are

air field mobile electrounits of types: АПА-352МУ, АПА-50, АПА-35/30, АПА-5Д, АПА-100, etc., mounted on the chassis of the automobiles.

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All modern airports receive the electric power from industrial three-phase alternating-current

mains with voltage 380 V and frequency of 50 Hz. However this electric power is not suitable for a supply of onboard systems of airplanes. For transformation of the industrial electric power to the necessary electric power for aircrafts rectifiers and converters are used which can be stationary (СК-60, СК-100) and mobile (АВП-20У1, АВ-2Ф, АМГА-17, АМГЭ-60/30М).

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At operation of power supply systems of an aircraft it is

necessary to observe the following key rules of the safety precautions:
to be convinced, that all switches in cabins of the plane are in the neutral or switched off position at connection of aircraft to a source of power supply;
to be convinced in value of a necessary voltage after connection to an onboard network of a ground source of the electric power;
to make correct switching on of the control units, stipulated only for a set operating mode;
all additional loadings, including plane units are disconnected at engine start;
to connect corresponding cable connections at start on system «24/48 V»;
to eexclude application of fuses;
to supervise a degree charging storage batteries.

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AIR SYSTEM OF THE ENGINE START.
The air system of start

is applied on airplanes with powerful engines. They also can be onboard and ground.

In ground air systems of start the compressed air from a ground source on a hose moves on an air starter which represents the air turbine with the big frequency of rotation. This turbine starter with the help of a reducer is connected to shaft of an aircraft engine and provided its rotation up to necessary frequency. Air starters are posses by smaller weight in comparison with electrostarters of identical capacity.

THE AIR START UNIT TLD ASU-600