Airport Engineering
PART 2 - AIRPORT ENGINEERING:
Unit- 1: Air transport development:
PDF Notes:
PDF Notes:
PART
2 - AIRPORT ENGINEERING:
Unit-
1: Air
transport development:
1-1. AIR TRANSPORT:
There has been considerable improvement and progress in the mode of
transport by air. This is the fastest mode of transport flying at more than 300
km p.h. to a modern speed which is nearly 3 times the speed of sound.
Following are the advantages of air transport:
(1) Accessibility: The air transport can reach otherwise inaccessible areas with other modes of transport and such areas
can, therefore, be economically developed with air transport only.
(2) Continuous journey: The aeroplanes can fly over
both, namely, land and water. They also do not require any artificial track as
in the case of railways and roadways. Thus, it grants the facility of a continuous
journey over long distances.
(3) Demand for technical skill: The manufacture of aeroplanes
and their maintenance as well as development, design, and construction of
airports have opened up new opportunities for highly technical manpower. The
air aviation industry can, therefore, claim to be the principal employer of highly
skilled professionals in the field.
(4) Emergency use: The air service can be used
for destroying the pests by an aerial spray of the chemicals. It is also extremely
useful in case of floods for dropping food packets to the affected people and
for observing the area to access the gravity of the situation.
(5) Engineering use: The air service is finding
at present an increasing engineering use in the preparation of maps by aerial
photography. The helicopters have been used in the construction of some high
rise buildings.
(6) Saving in time: It has resulted in a
tremendous saving in travel time because of the high speeds of aeroplanes.
Following are, however, the disadvantages of air
transport:
(1) Flight rules: There are certain rules
which are framed by the concerned authorities and these rules are to be
strictly observed for the smooth working of air transport.
(2) Operating expenses: This mode of transport
proves to be most expensive because heavy investments are required for the
construction of aeroplanes, airports, repair shops, meteorological stations,
etc. and special training is to be given to the pilots. The number of
passengers traveling by air as well as the quantity of cargo that can be
accommodated is the smallest as compared to other means of transport and hence,
the .fares are the highest.
(3) Safety: The accidents of aeroplanes are peculiar and alarming
in nature. It has led to the psychological fear among the passengers about the
safety in air travel. It has, therefore, become difficult to encourage the
general public to travel by air and to make them air-minded, especially in less
advanced countries.
(4) Weather conditions: This mode of transport can operate
only under favorable climatic conditions. For instance, the landing and taking
off operations of aircraft will be totally inconvenient during foggy days.
1-2. HISTORY OF AVIATION:
In several ancient countries, there exist traditional stories of unknown
authorship relating to flying boats and airships. Even in Ramayana, the great
popular Hindu epic, it is mentioned that Lord Ram returned to Ayodhya from
Lanka in 'Pushpak Viman' after defeating and killing Ravana. In the middle
ages, transport by air was considered impious and hence, there is no
mention of this mode of transport during this period. Mr. Roger Bacon studied
the flight of birds and he predicted in 1256 that the motive power required for
flying would be derived from fire.
In 1505, Mr. Leonardo da Vinci (1452-1519) wrote a book in which he
successfully incorporated the mechanical principles of the wing movement of birds.
He studied bird's motion, air resistance to a body moving in air and airflow. He
designed a parachute. He sketched many flying machines using human muscle. It
is understood that two French brothers took flight in a balloon in 1763 and Sir
John Cayley made an unsuccessful attempt in 1842 at applying steam-power to
such flights.
During the American Civil War, Mr. Count Zeppelin, a young German army
officer, made observations in an anchored balloon and after returning to
Germany, he constructed a plane lighter than air. This plane was fitted with
all necessary apparatus and propelling machinery. He improved his airship and
was able to make successful flights over the Alps. The flights in his airship
were full of dangers of fire and storm. It was also not provided with
sufficient lighting power and there were many mechanical drawbacks.
On December 17, 1903, a bicycle repairman by the name of Orville Wright
propelled himself through the air a distance of 35 m in the first powered
flight in a heavier-than-air craft known to man. The incident occurred at Kitty
Hawk, North Carolina, U.S.A. The two brothers, Mr. William Wright and
Mr. Orville Wright were the pioneers in the construction and use of
heavier-than-air flying airships. In 1909, Mr. Bleriot, a French aviator,
crossed the English Channel for the first time in a monoplane i.e. an aeroplane
with a single supporting wing or plane surface. The progress in the air was very
slow up to 1914.
The Zeppelin aeroplanes were freely used during the First World War
(1914-18) by Germany for carrying the passengers from one German city to
another. As a matter of fact, the gigantic strides were taken to produce
efficient machines to suit the needs of war. There was however no consideration
for the cost of production. But after the end of the war, attention was diverted in
reducing the cost of production and improving the design of aircraft.
Following are some of the events worth noting with respect to progress
in aviation after the First World War:
(1)
In 1918, the first international air service was
started in France between Toulouse and Barcelona.
(2)
In May 1918, the long-distance airmail service was
first introduced in the U.S.A. between Washington and New York.
(3)
In. 1924, the night flying on trans-continental
routes were commenced.
(4)
In 1926, the North Pole was air-conquered when Admiral
Byrd of U.S. Navy with pilot Bennet flew from Amsterdam Island to the North
Pole and back, a distance of 2575 km in about 16 hours.
(5)
In 1927, Mr. Charles Lindberg, an American aviator,
made the first solo flight i.e. a flight in which no other person participates,
across the Atlantic from New York to Paris in a monoplane.
(6)
In 1929, the first plane-to-ground radio
communication was established after which the air-travel became reasonably
safe.
(7)
In May 1930, Miss Anny Johnson reached Karachi from
London in 6 days.
(8)
In 1930, the round-the-world flight was made in
just 9 days by Post of U.S.A. and Gatty of Australia.
(9)
The first jet flight was made on August 27, 1939, in
Germany by the jet aircraft manufactured by Heinkel Aircraft Company.
The Second World War (1939-45) made a further impact on the development and
improvement of air transport techniques. In one sense, it can be said that the
development in aviation which took place during six years of war was nearly
equal to the one which would have required nearly 25 'to 30 years in normal
peacetime.
A vast network of passenger and freight carriage was set by the nations
at war with the main aim of achieving more speed and a minor emphasis on cost and
economy of operation. The bombers used during the war were subsequently
converted into commercial airlines.
In 1944, the delegates from 52 countries met in Chicago, U.S.A. to
consider the problems of International Civil Aviation. As per the
recommendation of this convention, International Civil Aviation Organization
(ICAO) was set up on April 4, 1947, with its headquarters in Montreal, Canada.
It is now a specialized agency of UNO and is mainly concerned with airport
development. Since then, the development in air navigation with respect to all
its aspects such as speed, landing facilities, etc. is quite steady.
The ICAO's membership comprises of 151 sovereign States. The ICAO has two
governing bodies, the Assembly and the Council. The Assembly is the
sovereign body of ICAO and it meets every 3 years at a place and time decided by the
Council. The Council is the permanent working group of (33 members elected by
the Assembly) the organization and is responsible to the Assembly for
discharging duties and obligations as per ICAO charter. The Council elects its own
President.
The objectives of ICAO as stated in its charter are to develop
the principles and techniques of international air transportation so as to:
(1)
Ensure the safe and orderly growth of the
international civil aviation throughout the world.
(2)
Encourage the arts of aircraft design and operation
for peaceful purposes.
(3)
Encourage the development of airways, airports, and air
navigation facilities for international aviation.
(4)
Meet the needs of the peoples of the world for
safe, regular, efficient and economical air transport.
(5)
Prevent economic waste caused by unreasonable competition.
(6)
Ensure that the rights of the contracting States are
fully respected and that every contracting State has a fair opportunity to
operate international airlines.
(7)
Avoid discrimination between contracting States.
(8)
Promote the safety of flight in the international air,
navigation.
(9)
Promote generally the development of all aspects of
the international civil aeronautics.
The ICAO works in close co-operation with other members of the United
Nations such as the World Meteorological Organization (WMO), World Health
Organization (WHO), etc. The ICAO Secretariat is headed by a Secretary-General
and it is divided into the following five divisions:
(1) air navigation bureau;
(2) air transport bureau;
(3) bureau of administration and services;
(4) legal bureau; and
(5) technical assistance bureau.
In addition to the regular staff, the services of experts are taken by a loan from member States as and when required.
There are various other international organizations active in the field
of airport engineering. The International Airport Transport Association (IATA)
is such other organization. It has the strength of more than 100 scheduled
international carrier members and its objectives are as follows:
(1) to promote the interests of civil aviation;
(2) to provide a forum for industry views;
(3) to establish industry practices; etc.
11-3. AIR TRANSPORTATION IN INDIA:
The aviation developments in India took place rather late. The first
recorded flight in India was performed by a Frenchman Henri Piquet when he
carried mail from Allahabad to Naini in the year 1911. In the same year, Sir
George Lloyd undertook the organization of air flying between Bombay and
Karachi. The air service between these two cities was purely a
government venture and it was established as a temporary and experimental
measure during the winter season with the object of testing the extent to which
airmail service was likely to be used by the public. As soon as sufficient
data regarding its running expenses had been collected, it was found quite
expensive as a commercial concern and hence, it was closed down.
During the next two decades or so, India observed more or less a
complete dull period in the aviation activities. In 1927, the Civil Aviation
Department was established and this organization helped in constructing a few
aerodromes and forming of some f1ying clubs. On December 30, 1929 a regular air
service between Karachi and Delhi was opened under the Imperial Airways
Service. On October 15 in 1932, the internal services were started by the Tata
Airways Ltd. It was an effective Indian enterprise which conducted air service
between Karachi and Madras once a week with calls at Ahmedabad, Bombay and
Hyderabad. In 1933, Indian Trans-continental Airways Ltd. was formed for
conducting foreign flights.
The civil aviation in India made a great headway between 1933 and 1938.
By the end of 1938, 153 aircraft were registered with details as follows:
65 for private individual flying
43 for training at flying clubs
31 for regularly scheduled air services
14 for miscellaneous commercial services.
153 Total
The Second World War gave stimulus to air transport in India and during
1939 to 1945, a large number of technical personnel were trained and much the experience was obtained in handling modern machines. For recruiting students in
airforce, a good deal of propaganda was also carried out in universities and
colleges.
To have control over the air-operating companies, the Air Transport
Licensing Board was established in October, 1946 and after the establishment of
this Board, an all-round development in aviation activities was visible in the
country. Within 2 years, the Board granted licenses to 11 air-operating companies.
India achieved political independence in 1947 and thereafter, the
development of air transport took place on scientific footing. The Tata
Airlines changed its name to Air India Limited. The Govt. established another
company known as Air India International Ltd. for the external services. It
inaugurated its first international service to London on June 8, 1948.
The Air Transport Corporations Bill was introduced in the Lok Sabha on
March 21, 1953, and in Rajya Sabha, on May 14, 1953. Under the provision of the
Bill, the two corporations were established - one for operating domestic
services and others for operating international services. Thus, the airlines
were nationalized and the two corporations began to function from August
1, 1953 with the set up of organization as follows:
(1) Indian Airlines Corporation:
It was organized for internal air services and was formed by the merger
of eight companies, namely, Bharat Airways, Deccan Airways, Himalayan
Aviation, Airways India, Air India, Air Services of India, Kalinga Airways and
Indian National Airways.
(2) Air India International Corporation:
It was organized for conducting international air services from four international
airports, namely, Santa Cruz (Bombay), Dum Dum (Calcutta), Palam (Delhi), and
Meenambakkam (Madras). It may be noted that the airport of Trivandrum was
updated on 2-1-1991 as an international airport, the first airport to attain
this status after independence. The up-gradation of the Trivandrum airport meant
the fulfillment of a long-standing and pressing demand of Kerala and it would
open up an entirely new vista for the overall development of the State.
From 26-1-1991, the international flight has begun from the city of
Ahmedabad, Gujarat State. The airport of Ahmedabad would however continue to
remain domestic. The Air India is operating five times a week flights
from Ahmedabad connecting passengers with international flights from Bombay and
Delhi to London and New York. The construction work of the new terminal
building for the Ahmedabad airport is nearly completed and attempts are made to
provide it with modern navigational aids.
The installation of the radar facility at the airport would make the
operations of domestic and international flights to be carried out more
efficiently. The majority of international flights zipping across from West to
East are flying over Ahmedabad after leaving Karachi and the airport could
handle any emergency landing of these flights including that of advanced Boeing
747s. The airport is also provided with two most sophisticated
Australian-made navigational aids - Daupler Very High-Frequency Omni Range
(DVOR) and Distance Measuring Equipment (DME). The DVOR with its 51 antennae,
known as 'counter-pois' provides the most accurate direction guidelines
to the pilots between one airport and another within a radius of 300 km.
The DME gives the exact distance between the aircraft and the airport to
the pilot. The Ahmedabad city airport has also the most modern and
technologically advanced radar system, namely, the US-made Monopulse Secondary Surveillance
Radar (MSSR) and the Airport Surveillance Radar (ASR). It enhances air safety
within a range of 500 km encircling the city and thus, it has resulted in
tightening vigil over the States' airspace.
There has been steady growth of the frequency of domestic and
international services since the formation of these two corporations.
The Indian Airlines (IA) is a full member of the International Airport
Transport Association (IATA) and it also provides services to the neighboring
countries, namely Burma, Ceylon, Afghanistan, and Nepal. In our country, the flying
conditions are good and the distances are vast.
The Indian Airlines possesses a vast fleet of Airbuses, Boeings,
Caravelles, HS 748, Viscounts, Avros, Fokker Friendships, and Dakotas. At
present, nearly all the important industrial, commercial and administrative
centers of the country are connected by air through a network of 88 domestic airports.
The Vayudoot was incorporated as a jointly owned company of IA and AI
with an intention to provide low-cost connections to the inaccessible parts of
the North East region. The short-haul services of the Vayudoot have also been introduced
in other parts of the country. The expansion of Vayudoot is indeed rapid and
depending upon the availability of aircraft, infrastructural facilities, etc.,
it aims to expand its services to nearly 130 stations.
The Air India International Corporation, now known as Air India, also
operates extensive scheduled services to various foreign countries at present.
The International Airport Authority of India (IAAI) was set up in April, 1972
for the operation, management, planning, and development of the four international
airports. However, the facilities of air traffic control, aeronautical
communication and navigation are provided to these four international
airports by the Civil Aviation Department.
Air India possesses a vast fleet of aircraft. But the latest to
join is Boeing 747 -400 named as 'Konark'. It is a part of a major fleet
renewal scheme and modernization to prepare the country to attract foreign
tourists of the 21st century. This aircraft is controlled by the latest
system of computers and it is designed in such a way that it can be loaded or
unloaded in seven minutes only.
Civil Aviation Department:
The National Airport Authority (NAA) was established on 1-6-1986 through
an Act of Parliament and it is managed by a board consisting of Chairman, four
full-time members and eight part-time members.
The main object of NAA is to ensure the highest standard of air
traffic control by using modern sophisticated equipments and to maintain the
international standards with respect to air traffic control, aeronautical
communications, ground safety operations, etc.
The major responsibilities of NAA can' be enumerated as follows:
1.
to ensure the safety of all the operations
performed by the aircraft;
2.
to manage all domestic civil airports and civil
enclaves;
3.
to provide all the essential facilities like
managing the runways, technical buildings, air traffic control services, airport
environment, civil aviation training centers, navigational and radar services
at domestic and international airports, visual aid ground safety service at
domestic airports, etc.
The regulatory functions such as airworthiness of aircraft, licensing of
personnel, approval of tariffs, preparation of schedules, etc. are looked after
by the Director-General of Civil Aviation (DGCA).
The achievements of NAA are numerous and deserve to be appreciated. The
NAA, with its future plans and well managed vast network of airspace, is
hopeful to meet the challenges to be faced by the civil aviation department in
21st century.
Open Sky Policy:
January 29, 1994 marked an important day in the calendar of civil
aviation of our country. The Air Transport Corporation Act of 1953 was repealed
for introducing the open sky policy. The private airlines are now permitted to fly
in air under the supervision of DGCA.
Among the various private air operators, the currently largest in the
East-West with 11 planes. The other important operators are Damania Airways,
Jet Airways, Modiluft, Sahara Airways, etc. The introduction of open sky policy
will certainly improve the air travel conditions because of competition among Indian
Airlines (IA) and the private operators.
1-4.
AIRPORT TERMINOLOGY:
Following are some of the important terms and definitions, the meanings
of which are explained at this stage, for the easy understanding of the subject
of airport engineering:
(1) Aerodrome:
Any defined area on land or water (including any buildings, installations
and equipment) intended to be used for the arrival and departure of an aircraft
is called aerodrome. It may be provided with the facilities for shelter and
repair of aircraft and also for processing of passengers, baggage, mail and
cargo. It may not necessarily be used for all scheduled air flights. Sometimes
the term aerodrome is used to mean an airport.
(2) Aeroplane:
An aeroplane is a power-driven heavier-than-air flying machine with
fixed wings. It derives its lift in atmosphere chiefly from the aerodynamic
reactions on its surfaces.
(3) Aircraft:
An aircraft is a general term which is used to mean any machine for
navigating the air and deriving support from the reactions of the air. It may
or may not be power-driven. It may be lighter or heavier than air. It thus
includes glider, aeroplane, helicopter, rocket, etc. An aircraft that travels
with a speed less than the speed of sound is a subsonic aircraft while
an aircraft that travels with a speed greater than the speed of sound is a supersonic
aircraft. The speed of sound depends on temperature and it increases with
the increase in temperature. The average speed of sound may be taken at 1130 km
p.h.
(4) Airfield:
An airfield is an area which is used for landing and takeoff of an
aircraft. It may or may not be provided with facilities for convenience of
passengers and for shelter, repair and servicing of aircraft.
(5) Airport:
An airport is an aerodrome which is principally intended for the use of
commercial services. It is provided with custom facilities in addition to other
normal facilities, if it serves any international traffic.
(6) Airport capacity:
The number of aircraft movements which an airport can process or handle
within a specified period of time, usually an hour, is called the airport
capacity. A landing or take-off operation is taken as one movement.
(7) Airport established elevation:
It is the elevation above mean sea level of the highest point of the
landing area.
(8) Airships:
A power-driven lighter-than-air aircraft is known as an airship.
(9) Approach area or approach zone:
An aircraft neither gains nor loses height all at once, but does so
gradually along an inclined path. The approach area or approach zone indicates the
wide-area on either side of a particular runway up to a certain distance which
is kept clear of any obstruction. The center-line of approach area coincides
with that of the runway. The area on ground is trapezoidal in shape with its
width increasing from the runway-end outwards. The approach areas are measured
on horizontal surfaces.
(10) Approach surface:
A line rising at a particular slope from the runway end represents the
obstruction clearance line and the imaginary inclined plane containing this line
and directly above the approach area is known as approach surface.
(11) Apron:
It indicates a defined area of the airport to accommodate aircraft for
loading and unloading of cargo and passengers, parking, refueling, etc. It is
usually paved and is located in front of the building or adjacent to hangars.
(12) Balloon:
A non-power-driven and lighter-than-air aircraft are known as a balloon.
(13) Beaufort scale:
In 1805, Admiral Beaufort of the British Navy devised a scale of wind
force and it is widely known after his name. It consists of numbers 0 to 12 and
higher numerals are indicative of higher speeds. The International
Meteorological Committee for wind velocities adopted the scale in 1874 as a
part of the code employed in communicating the weather conditions. Table 1-1
gives the phrases along with the corresponding Beaufort numbers and approximate
wind velocities.
(14) Blast pads:
The specially designed shoulders provided at the takeoff ends of the
runway and along taxiway are known as the blast pads. They protect the
shoulders from erosion due to high velocity of the jet exhaust.
(15) Boundary lights:
The aeronautical ground lights which delineate or trace the outline of
the boundary of a landing area are known as boundary lights.
(16) Boundary markers:
The markers used to indicate the boundary of a landing area are known as
boundary markers.
(17) Calm period:
The absence of appreciable wind, generally considered as 6 kmph. or
less, is called the calm period. The knowledge of calm periods of a particular
place throughout the year plays an important role in designing an airport.
(18) Cargo:
The term cargo is used to indicate the freight, other than passengers,
baggage and mail, which is carried by a transport aircraft.
(19) Clearway:
It is defined as a rectangular area at the end of a strip or channel in
the direction of takeoff over which the aircraft may make its initial climb.
(20) Conical surface:
It is the internal surface of the frustum of an imaginary hollow
inverted cone extending upwards and outwards from the periphery of the
horizontal surface with a slope of 1 in 20 measured in a vertical plane.
(21) Control area:
The airspace of the defined dimension within which air traffic control is exercised
is known as a control area.
(22) Control tower:
A tower that is usually situated at the top of the terminal building
with its walls enclosed in glass enabling the operator to have an unobstructed
view of the entire airfield is known as the control tower. It controls the air
traffic at the airport by supervising and directing the flight of the arriving
and departing aircraft within the airport control area.
(23) Control zone:
The term control zone is used to indicate airspace of defined
dimension within which rules additional to those governing flight in control
area apply for the protection of air traffic.
(24) CTOL:
The term CTOL is used to mean conventional takeoff and landing.
(25) Design landing weight:
The maximum aeroplane weight for landing conditions at the maximum
velocity of descent is known as design landing weight.
(26) Design take-off weight:
The maximum aeroplane weight for flight load conditions is known as
design take-off weight and it is used for the structural design of the runways,
taxiways, and aprons.
(27) Elevator: The movable part of the tail whose only purpose is
to grant longitudinal control for achieving longitudinal stability is known as an elevator.
(28) Flight time:
The total time from the moment an aircraft first moves under its own
power for the purpose of taking off to the moment it comes to rest at the end
of the flight is known as flight time.
(29) Flight visibility:
The term flight visibility is used to indicate the average range of
visibility in a forward direction from the cockpit of an aircraft in flight.
(30) Fuselage:
It indicates the main body of an aircraft to which wings and other parts
are attached.
(31) Gate position:
The space allotted to an aircraft parking at a loading apron is known as
gate position.
(32) Hangar:
The large shed erected at the airport for the purpose of housing,
servicing and repairing of aircraft is known as a hangar.
(33) Helicopter:
It is a type of airplane in which the machine is equipped with one
or more lifting propellers rotating horizontally about an approximately
vertical axis.
(34) Heliport:
The area for landing and taking off of helicopter is known as a heliport.
(35) Holding apron:
It is the designated portion placed adjacent to the ends of runways for
allowing to check aircraft instruments and engine operation prior to take off
and also to wait till clearance for takeoff is given.
(36) Horizontal surface:
The imaginary horizontal surface which is circular in plan and which is
located at a level of 45 m above the airport established elevation is known as a horizontal
surface.
(37) Instrument landing system (I.L.S.):
The aircraft, by this system of landing, is brought to rest upon the
ground with the help of radio beam facilities installed on the airport and the manipulation
of the control instruments by the operator of the aircraft as directed by the
radio beams. The I.L.S. thus provides lateral and vertical guidance to the
aircraft during ·landing and it is also popularly known as a blind landing
system. During bad weather conditions and poor visibility, the operator can
make safe landing of aircraft without seeing the runway with the help of I.L.S.
(38) Instrument runway:
The runway which is adequately equipped with the radio beam facilities
and on which landing can be made according to I.L.S. rules is known as an instrument
runway.
(39) International airport:
It is an airport that handles international air traffic and functions
according to international aviation rules framed by ICAO. It serves as a place
of entry and departure from the country and necessary facilities for customs,
immigration and other procedures are also provided on such an airport.
(40) International air service:
The air service which passes or crosses the air space of the territory
of more than one country is known as an international air service.
(41) Landing area:
The portion of airport, excluding the terminal area, which is used for
landing and takeoff of the aircraft is known as landing area.
(42) Landing strip:
A long and narrow area that is suitable for the landing and takeoff of
the aircraft is known as landing strip. It forms part of an airport and it
consists of a runway plus the shoulders on either side of the runway.
(43) Mach number:
The speed relative to the speed of sound is indicated by a number known
as the Mach number. Mach 1 means the speed which is equal to that of sound.
(44) Missed approach:
When landing is not effective after an instrument approach, it is known
as a missed approach.
(45) Parachute:
The device resembling an umbrella made of silk sheet with cords attached
to it and opening automatically on the pulling of a rip-cord is known as a parachute. When in use, it breaks the speed of a falling person or object from a
great height under gravitational force. The parachute jumping can be treated as
a sport and it can be carried out from the aircraft flying at great heights.
(46) Pressure altitude:
The altitude at which the pressure corresponding to the standard
atmosphere is obtainable is known as pressure altitude.
(47) Rudder:
It is one of the major controls while the aircraft is in flight. It
helps the pilot to turn the nose of the airplane in any particular direction.
It can move to and fro about a vertical axis through about 30°. It is usually
hinged to the fin at the tall.
(48) Runway:
It is defined as a long and comparatively narrow strip of land which is
selected or prepared for the landing and takeoff of aircraft along its length.
It is usually paved except for small aerodromes.
(49) Standard atmosphere:
It is a fictitious atmosphere of dry air and it has been defined by the
ICAO to have the following conditions:
(i)
The air is a perfect dry gas.
(ii)
The temperature at sea level is 15°C.
(iii)
The pressure at sea level is 760 mm of mercury.
(iv)
The temperature gradient from sea level to the
altitude at which the temperature becomes -15.5°C is -0.0065°C per m and zero
above.
(50) STOL:
It indicates short takeoff and landing.
(51) STOLport:
The area used for landing and take-off of STOL aircraft is known as
STOLport.
(52) Stopway:
It is defined as a rectangular area at the end of the runway in the
direction of takeoff in which an aircraft can be stopped after an interrupted
take off. Its width is equal to the width of runway and thickness sufficient to
bear the weight of the aircraft.
(53) Surveillance radar:
The radar which provides an overall picture of the surrounding
atmosphere within a radius of 50 km to 100 km is known as surveillance radar.
It moves through 360° and the information about any aircraft within the range
is received on a scope in the form of pip or dot having a luminous tail behind
and thus indicating the path of its movement.
(54) Taxiway:
A defined path on a land aerodrome, selected or paved for the use of
taxiing aircraft to and from the runway and loading apron is known as a taxiway.
(55) Terminal area:
The portion of the airport other than the landing area is known as
terminal area and it includes terminal building, aircraft· apron, cargo storage
building, hangars, automobile parking area, etc.
(56) Terminal building:
The building or buildings which are meant for providing facilities to
all passengers, for serving as office for airport management and for carrying
out other non-aeronautical functions are known as terminal buildings. They act
as focal points of the terminal area.
(57) Transition surface:
The imaginary inclined plane with a slope of 1:7 measured upward and
outward in a vertical plane at right angles to the center-line of the runway is
known as transition surface.
(58) Visual flight rules (VFR):
The rules which are observed for the landing of an aircraft by visual
reference to the ground are known as VFR. When the weather conditions are good,
the landing of an aircraft is made by making use of VFR.
(59) Visibility:
The greatest distance to which a prominent object of certain specified
dimension is perceivable to the eye, the object being observed in the daylight
during day and properly lit during night under the existing atmospheric conditions
is known as visibility.
(60) Wind rose:
The diagram showing direction, duration, and intensity of wind over a
certain period in a specified region is known as wind rose. Its shape resembles
a rose.
(61) Zero fuel weight:
The term zero fuel weight is used to indicate the weight above which all
additional weight must be in fuel.
(62) Zoning:
It pertains to the enactment of legislation for a restricted development
of the area surrounding the airport so that no structure protrudes above the
obstruction clearance line and thus cause a hazard to safe air navigation,
especially in the approach and turning areas.
1-4. COMPONENT PARTS OF AEROPLANE:
Following are the seven essential parts of an airplane:
I.
Engine
II.
Flaps
III.
Fuselage
IV.
Propeller
V.
Three controls
VI.
Tricycle undercarriage
VII.
Wings.
Fig. 1-1 shows the component parts of an aeroplane. Each of the above
component will now be described briefly.
Fig. 1-1
I. Engine:
The main purpose of providing an engine to the aircraft is to make
available the force for propelling the aircraft through the air. According to
the method of propulsion, the aircraft can be classified in the following three
categories:
(1) Piston engine
(2) Jet engine
(3) Rocket engine.
(1) Piston engine:
These are the conventional types of aircraft engines which are suitable
to operate at low altitudes with moderate speeds. The aircraft is provided with a gasoline fed reciprocating engine which is driven by propeller or airscrew. The
engine rotates a shaft with huge torque and the torque so developed is
absorbed by the propeller, mounted on the shaft. When the rated speed is
attained by the propeller, a large quantity of air is hurled rearward which pulls
the aircraft forward and lifts the wings.
(2) Jet engine:
The main advantage of the jet engine is that it eliminates propellers
and thus, the aircraft can move at high altitudes at high forward speeds. It
thus eliminates the main drawback of the piston engine and for the purpose of convenience,
it can be grouped in the following three types:
(i) Turbojet: In the case of turbojet
aircraft, the hot exhaust gases having high velocity give a forward thrust to
the engine. It is reported that the gases coming out with the speed of 1600
kmph may push the plane with a speed of about 800 kmph. The efficiency of
aircraft is greatly improved at high altitudes because of the following two reasons:
a) There is a drop in the atmospheric density and thus, the resistance
to the passage of aircraft is reduced.
b) There is a great temperature
difference through the turbine.
(ii) Turbo propulsion: The performance of turbo propulsion
aircraft is similar to that of turbojet except that a propeller is provided in
it. However, its performance is equally satisfactory in low as well as high
altitudes as compared to the turbojet which gives better performance at
moderate altitudes. The speed of turbo propulsion is limited by propeller
efficiency.
(iii) Ramjet: It is a jet engine which
does not have any moving parts. The fuel flow and combustion are continuous. The
spark plug is used at the start only. The heated air expands and rushes out of
the exhaust nozzle at high velocity which creates the jet. The main features of
this aircraft are simplicity of design and high speeds of about 1280 to 2400 kmph.
However, the consumption of fuel is very high. It is used as pilotless aircraft
for guided missiles.
The jet engines have numerous attractive features over the conventional
engines and they can be enumerated as follows:
(1) No radiators or other cooling devices are required.
(2) The chances of fire hazards are decreased.
(3) The controls are simple.
(4) The operation is noiseless.
(5) The specific weight is low.
(6) There are no vibrations.
(7) There is less consumption of lubricating oil.
(8) There is no necessity of spark plugs or carburetors.
The jet engine because of its many advantages has been universally
recognised as proper mode of aircraft propulsion and the conventional aircrafts
propelled by piston engines are replaced by jet aircrafts.
(3) Rocket engine:
The manner of production of thrust in case of rocket engine is the same
as that of the ram jet except that it does not depend on the oxygen in the atmosphere
for the combustion. It carries its own supply of oxygen and hence, it can
operate at high altitude or outside oxygen bearing atmosphere at extremely high
speed of about 4600 kmph. However, the rocket engine has the highest specific
fuel consumption as compared to all other engines.
An aeroplane may have one, two, three or four engines. The engine is
placed in the nose of the aircraft for a single engine aeroplane. If engines
are two or four in number, they are placed symmetrically about the nose of the
aircraft. In case of aircraft with three engines, one is placed in the nose and
one on each side of the two wings. The advantages of using more than one
engine are as follows:
(I)
Chances of accidents: In case of multi-engine
aircraft, it is possible to continue the flying even if one engine has failed
or gone out of order till area for safe landing is reached. Thus, the chances
of accidents are greatly reduced.
(II)
Increase in power: Depending upon the number
of engines, the power and weight carrying capacity of the aircraft are
increased proportionally.
(III)
Reliability: A single engine even of
highly sophisticated nature cannot be relied upon for its performance for all
the time. If a breakdown occurs during flying, it becomes difficult for the
pilot to avoid crash unless satisfactory landing ground is available. Thus, the
multi-engine aircrafts are more reliable.
II. Flaps:
A flap is a hinged section of an airplane wing, used in landing or take
off. The flaps, when projected into air, produce an immediate reduction in
speed of the aircraft and thus; they are intended to serve as air brakes. They
are fitted only to the inner portion of the wing and it is so arranged that the
flaps on either side are pulled down together. They are somewhat similar to the
ailerons and it is so arranged that they can be operated by the pilot
from his cabin. The flaps provide necessary lift at low speed and hence, they
are helpful for landing the aircraft satisfactorily. Thus, they serve as an
important control during the landing operation of the aircraft.
III. Fuselage:
It provides space for the accommodation of the plant, fuel, cockpit,
cargo, passengers, mail, service tables, ovens, bathrooms, etc. It must possess
the following characteristics:
(1)
It is shaped to a fine point at the rear end and
yet it should not be too fine so as to make it unable to resist twisting
stresses due to the wind.
(2)
It must be large enough to give sufficient tankage space.
But at the same time, it should be as small as possible to reduce the wind
resistance.
(3)
It should have enough depth for strength. But it
should not be very deep because in that case, the side area may become very
large which is undesirable for safety and efficiency.
IV. Propeller:
The propeller is provided in the conventional piston engine as well as
in the turbo propulsion engine. It has usually two or more blades which are
driven round in a circular path. The blades deflects air backwards with an
acceleration and thus, forward thrust is imparted to the aeroplane. When the engine
and propeller are in front, the machine is described as a tractor type. When
the engine and airscrew are behind the wing, it is known as a pusher installation.
The latter type is generally not preferred.
V. Three controls:
An aircraft in space can move in three principal axes, namely X-axis,
Y-axis and Z-axis, as shown in fig. 1-2.
The movement of aircraft about the X-axis is called the lateral or
rolling movement. This axis passes through the centre-line of nose and
tail of the aircraft. A hinged flap, known as aileron, is fixed in the
trailing edge of wing near the wing tip to serve as control of the aircraft
along X-axis or longitudinal axis.
The aileron is rigged in such a way that when in one wing is pulled up,
that in other wing is pulled down. The net effect of doing these operations
simultaneously is to give a very powerful rolling control to the aircraft about
its X-axis. The function of aileron is to enable the pilot to balance the aeroplane
when it is tilted by a gust of wind. It also permits to tilt the machine
purposely, say when the aeroplane describing a circle and it is desired to tilt
it laterally.
The movement of aircraft about the Y-axis is called the pitching. This
axis passes through the centre-line of wings and it is perpendicular to the
X-axis. The elevator in the form of two flaps is provided at the
extreme rear end of fuselage to control the pitching or up and down movements of
the aircraft. The elevator is capable of moving up and down through an angle of
50° to 60°. The flaps of elevator are hinged to a fixed horizontal surface
known as stabilizer or tail plane. When the elevator flap is
raised, there is increased air pressure on it which results in tail to go down
and nose to point up. When the air pressures are equal at the top and bottom of
the flaps, the elevator is in a neutral position and the aircraft flies along
the normal line of flight.
The movement of aircraft about the Z-axis is called the yawing. This
axis passes at right angles through the meeting point of X-axis and Y-axis. The
turning or yawing movement of the aircraft to the right or left of the vertical
axis through an angle of about 30° is achieved by the rudder which
consists of a stream-lined flap hinged to a vertical axis at the tail end of
the fuselage. The rudder makes it possible to steer the aeroplane in the air
along Z-axis.
Thus, there are three devices in an aircraft to control the
movements in three directions, namely, aileron, elevator and rudder.
The combined assembly of elevator and rudder provided at the tail end of
the fuselage is also known as the empennage. It is also so arranged that
each control can be operated by the pilot from his cabin.
VI. Tricycle undercarriage:
The landing-gear system which is provided to support aircraft while it
is in contact with the ground is known as tricycle undercarriage and it serves
the following two main purposes:
(1)
To enable easy manoeuvring: The suitable assembly of wheels
allows the aircraft to move on the runway carrying its entire weight.
(2)
To permit smooth landing: The aircraft during landing
touches the ground with certain vertical velocity. A certain amount of energy
has therefore to be dissipated during the touch down operation. The
undercarriage permits this phenomena to occur as smoothly as possible.
Fig. 1- 3 shows the basic wheel configurations or arrangements of the
aircraft landing-gear system. There -are generally two main gears which
are provided in the fuselage or in the wings near the junction of fuselage and
wings. The major portion of the load to the extent of about 90% is carried by
these two main gears. The third wheel is provided either at the tail as
shown in fig. 1-3(a) or at the nose as shown in fig. 1-3(b) and it carries only
a very small portion of about 10% of total load. The provision of third wheel
at tail is not preferred because it keeps the nose up and the wings are at
greater angle of incidence. If wind blowing is powerful, the aircraft may be lifted
off the ground or pushed backwards even when it is stationary and the engine is
not working. On the other hand, when the third wheel is kept at the nose, it
keeps the nose in down position and the wing angle is reduced. However, such an
arrangement is slightly inconvenient for the loading of the goods and
passengers.
If at each of the three points, there is one wheel only, the
arrangement is known as single wheel assembly, as shown in fig.1-3(a) and fig.
1-3(b). If there are two wheels at each; of the three points of
support, as shown in fig. 1-3(c), the arrangement is known as dual wheel
assembly. If the nose point has two wheels and the main gear consists of
four points of support, each point having two wheels, the
assembly is known as twin tandem gear assembly, as shown in fig. 1-3(d). In
this case, there are eight main gear wheels in two rows in tandem
and each row has two points of support. Thus, there are two main
gear wheels at each point as in the case of dual wheel assembly.
When one of the main gears has more than one wheel, it is known as
multi-wheel assembly and such an arrangement allows the aircraft load to be
distributed over a large area of runway pavement and its thickness can be
reduced.
The two main gears along with nose or tail gear forms the
tricycle arrangement. When the load is distributed on two gear
assemblies placed along the axis of the fuselage without any nose or tail
wheel, as shown in fig. 1-3(e), the system is known as twin-twin bicycle
gear arrangement.
VII. Wings:
An aircraft is provided with wings to support the machine in the air.
The term aerofoil is used to mean a wing like structure which may be flat or
curved and is designed to obtain reactions upon its surface from the air
through which it moves. The wings are slightly curved in section and are set at
a small angle of incidence to the horizontal. Fig. 1-4 shows the various parts
of a cambered aerofoil.
It is easy to understand how a cambered aerofoil obtains the vertical
lift from air pressure. As shown in fig. 1-5, the areas of reduced pressure and
increased pressure are formed simultaneously on the top surface and bottom
surface of the aerofoil because of its streamline shape. A cambered aerofoil receives
a current of air in an upward direction and directs it downwards. Thus, a lift
reaction is obtained. The ideal design of an aerofoil will be the one which
gives the greatest area of positive pressure at the bottom. The shape of the
aerofoil should be such that no back currents or eddies are formed in the
streamline airflow over its surfaces.
As the machine gathers speed, the lifting force finally becomes equal to
its weight and the aeroplane rises. If the flying speed becomes too much less,
the lifting force becomes less than the weight of machine and the aeroplane
stalls i.e. develops the tendency to drop or go out of control. To prevent stalling
and to allow smooth landing at comparatively low speed, various devices have
been introduced in the aerofoil which suitably alter the resistance of the
wings to air and thus modify the lifting force.
The wings may be in the form of a single pair i.e. a single wing on
either side of the fuselage. Such planes are known as monoplanes. A plane
having two wings, one above the other, is known as a biplane. In such a
case, the wings are connected by vertical struts. The triplanes and
quadriplanes having triple and quadruple pairs of wings respectively are also
used as aeroplanes. But the biplane is the most prevailing type of aeroplane.
The monoplanes have the advantage of lightness or less air resistance and
hence, they are speedier than the biplanes. On the other hand, the biplanes
possess greater stability and are safer as compared to the monoplanes. The wing
structure consists of the following:
(1) spares which are
the two principal longitudinal members;
(2 ribs which are in the form of numerous cross members to
maintain the curvature of upper and lower covering area of the wing;
(3) stringers which are light spanwise members provided between
the ribs to provide attachment for the skin plating; and
(4) covering which may consist of a light metal alloy like duralumin.
The wing structure should be sufficiently strong enough to resist bending
forces and it must possess torsional stiffness. The spars carry the bending
forces and the box like construction grants the necessary torsional stiffness.
1-5. AIRCRAFT CHARACTERISTICS:
Following are the characteristics of a conventional type aircraft:
(1)
Aircraft capacity
(2)
Aircraft speed
(3)
Aircraft weight and wheel arrangement
(4)
Fuel spilling
(5)
Jet blast
(6)
Minimum circling radius
(7)
Minimum turning radius
(8)
Noise
(9)
Range
(10)
Size of aircraft
(11)
Takeoff and landing distances
(12)
Type of propulsion
(13)
Tyre pressure and contact area.
Each of the above characteristic of an aircraft will now be briefly described.
(1) Aircraft capacity:
The capacity of aircraft will determine the number of passengers,
baggage, cargo and fuel that can be accommodated in the aircraft. The terminal facilities
are planned to receive the aircraft of the highest capacity likely to land.
(2) Aircraft speed:
The aircraft speed is referred in many ways. But the difference between
the following two terms is worth noting:
(i)
air speed; and
(ii)
ground speed.
The term air speed is used to mean the speed of the aircraft
relative to the medium in which it is travelling. The ground speed which
is sometimes also referred to as the cruising speed is the speed of the
aircraft relative to the ground. Suppose an aircraft is flying at a ground
speed of 500 kmph. in air having wind velocity of 50 kmph. In the opposite
direction. Then, (500 - 50) = 450 kmph. will be the air speed.
On the other hand, if the wind is blowing in the same direction, the
speed will be (500 + 50) = 550 kmph. Thus, the air speed indicates the speed
that the aircraft wing or airfoil encounters.
There is a slight difference of about 2 per cent between the true air
speed and the indicated air speed. The pilot obtains the speed from an air
speed indicator which is a highly sensitive instrument with respect to the
density of air at different altitudes. Thus, the indicated speed is found
slightly less than the true air speed.
With the introduction of jet aircrafts and other high-speed aircrafts,
the reference datum for speed is often the speed of sound. After the great
Austrian scientist Ernst Mach, the speed of sound is defined as Mach 1 and
hence, Mach 2 means double the speed of sound. Most of the present jet aircrafts
are subsonic i.e. slower than the speed of sound and they have true air speed
of about 0.8 to 0.9 Mach. Many military aircrafts are supersonic i.e. faster
than the speed of sound.
(3) Aircraft weight and wheel arrangement:
It is necessary to understand the components of aircraft which make up
its weight during take offs and landings because weight is one of the major
factors which will govern the length and thickness of a runway. The wheel
arrangements or configurations also play a similar role and the aircraft wheel arrangements
have already been explained in fig. 1-3.
Following terms are used for different weights in the airline operations:
(i) Maximum gross takeoff weight: It is the maximum load
which the aircraft is certified to carry during take off and the airport
pavements are designed for this load.
(ii) Maximum structural landing weight: It is the difference
between the gross takeoff weight and the weight of fuel consumed during the
trip. The main gear of an aircraft is designed to support the maximum
structural weight because such situation rarely occurs. For instance, if an
aircraft starts trouble immediately after takeoff, the pilot has to carefully return
the aircraft to the airport and it should be so manipulated that the maximum
landing weight is not exceeded.
(iii) Operating empty weight: The weight of an aircraft including
crew and all the necessary gear required for flight is known as the operating
empty weight and it does not include pay load and fuel. For a passenger
aircraft, the operating empty weight will not be constant. But it will depend
on the seating arrangement.
(iv) Pay load: The term pay load is used
to mean the total revenue-producing load and it includes the weight of passengers
and their baggage, mail and cargo.
(v) Zero fuel weight: It is the weight above
which all additional weight must be fuel so that when the aircraft is in
flight, the bending moments at the junction of the wing and fuselage do not
become excessive.
The aircraft weight is thus composed of the operating empty weight and three
variables of pay load, trip fuel and fuel reserve. The weight of an
aircraft on landing is composed of the operating empty weight, the pay load and
the fuel reserve, assuming that the aircraft lands at its destination and is
not diverted to an alternate airport. This landing weight should not exceed the
maximum structural landing weight of the aircraft. The takeoff weight is the
sum of the landing weight plus the trip fuel and it should not exceed the
maximum gross takeoff weight of the aircraft.
Table 1- 2 shows the approximate estimate of the distribution of the
components of aircraft weight. It may be noted that as the range of aircraft
increases, the percentage of pay load decreases and that of trip fuel
increases.
The fuel requirement of any aircraft can be divided into two categories,
namely, trip fuel and fuel reserve. The fuel for trip will depend on various
factors such as pay load, altitude of travel, speed of aircraft, distance to be
travelled, atmospheric conditions, etc. The reserve fuel will depend on trip
length, traffic condition, location of alternate airport in the event of emergency
landing, etc.
(4) Fuel spilling:
The spilling of fuel and lubricants usually found in the loading aprons
and hangars. It is difficult to avoid spilling completely, but efforts are made
to bring it within minimum limit. The pavement of bituminous material is
seriously affected by the fuel spilling and hence, the area of bituminous
pavement below the fueling inlets, the engines and the main landing gears are
kept under constant watch by the airport authorities.
(5) Jet blast:
The turbo jet and turbo prop aircrafts eject hot exhaust gases at
relatively high velocities. The velocity of jet blast may be as high as 300
kmph and it may even cause inconvenience to the passengers boarding the aircraft.
For this purpose, several types of blast fences are available to serve as an
effective measure for diverting the smoke ejected by the engine.
The deteriorating effect on the bituminous pavement by the commercial
aircrafts is practically negligible because of the following two facts:
(a) Most of the civil jets have the tail pipes inclined a an angle of
about 2° relative to the pavement surface
(b) The height of the engine above the pavement surface is about 150 cm.
It is desirable to provide cement concrete pavement to resist the effect
of jet blast in preference to the bituminous pavement. The effect of jet blast
should also be studied for determining the size, position and location of
gates.
(6) Minimum circling radius:
A certain minimum radius in space is required for the aircraft to take
smooth turn is known as the minimum circling radius and it depends upon the
type of aircraft, air traffic volume and weather conditions.
The knowledge of minimum circling radius helps in separating two nearby
airports by an adequate distance so that the aircrafts landing simultaneously
on them do not interfere with each other. If it is not possible to provide such
distance, the timings of landing and takeoff of aircrafts in each airport will
have to be suitably adjusted. This aspect will reduce the capacity of each
airport.
Table 1-3 shows the minimum circle radii for different types of the
aircrafts.
Table 1-3
(7) Minimum turning radius:
It is necessary to know the minimum turning radius of an aircraft to
decide the radius of taxiways and to ascertain its position in the landing
aprons and hangars. Fig. 1-6 shows the method of determining the minimum
turning radius.
The procedure adopted is as follows:
(i)
The line through the axis of nose gear when it is at
its maximum angle of rotation is drawn. The maximum angle of rotation is
specified by the manufacturers and for a large turbo jet, it is between 50° to
60°.
(ii)
Another line through the axis of the two main
gears is then drawn.
(iii)
The intersection of the above two lines
forms the centre of rotation.
(iv)
The line joining the centre of rotation with the
tip of the farther wing of the aircraft is known as the minimum turning
radius. The paths of nose gear and main gear can also be drawn.
(8) Noise:
The most serious problem facing aviation is the noise and efforts are
made to bring it to the minimum possible level. The major sources of noise in
an engine are the machinery noise and the primary jet. During takeoff, the
dominant source of noise is the primary jet and during approach or landing, the
dominant source is the machinery noise. The disturbance caused during takeoff
is more severe than that caused during landing.
The noise is measured by an instrument known as a sound-level meter and
it indicates the total amount of sound present at any location. It is described
as the overall sound pressure level in decibels (dB),
For complex noises such as those produced by the aircrafts, the overall
sound pressure level provides an inadequate physical description and the two
noises can have the same overall sound pressure level and yet, they may be judged
differently subjectively. It has led to the development of the perceived
noise level intensity (PNdB). It is a quantity that is calculated from
measured noise levels and adjusted by weighing more heavily those frequencies
which are more annoying and disturbing to the distances.
The effective perceived noise level (EPNdB) is a further refinement
of the PNdB. The EPNdB is the PNdB corrected for the duration of sound and
adjusted for the presence of pure tones. The EPNdB is used for the
certification of aircraft and for the calculation of noise exposure
forecasts (NEF).
The modern technology has made it possible:
(i)
to dramatically increase thrust without
significantly increasing noise levels; and
(ii)
to substantially reduce noise for a given amount of
thrust.
The prospects of producing reasonably quieter engines in future are
promising. The reduction in field length is also found to be the most effective
way of minimising the impact of aircraft noise.
(9) Range:
The distance that an aircraft can fly without refuelling is known as the
range. There are a number of factors which influence the range of an aircraft,
the most important one being the pay load. Usually, as the range is decreased, the
pay load is increased and vice versa. The relationship between pay load and
range is also affected by factors such as meteorological conditions during
flight, speed, fuel, wind, flight altitude and amount of reserve fuel.
(10) Size of aircraft:
Fig. 1-7 illustrates the definition of the principal dimensions of an
aircraft. They are as follows:
(i)
Fuselage length: The length of aircraft
decides the widening of taxiway on curves, size of aprons and hangars.
(ii)
Gear tread: It is the distance between
the main gears and it governs the minimum turning radius of the aircraft.
(iii)
Height: It decides the height of
the hangar gate and other miscellaneous installations inside the hangar.
(iv)
Tail width: It helps in deciding the
size of the parking and apron.
(v)
Wheel base: It decides the minimum
radius of the taxiway.
(vi)
Wing span: It governs the width of
taxiway, clearance distance between two parallel traffic ways, size of
aprons and hangars, width of hangar gate, etc.
(11) Takeoff and landing distances:
The takeoff and landing distances for an aircraft will help in
determining the minimum runway length required for a particular type of aircraft.
These distances depend on the following factors:
(i)
altitude of the airport;
(ii)
gradient of the runway;
(iii)
intensity and direction of the wind;
(iv)
manner of landing and takeoff;
(v)
temperature;
(vi)
weight of the aircraft at the time of landing and
takeoff.
(12) Type of propulsion:
The types of engines used in an aircraft have already been discussed
earlier. The method of propulsion adopted for a particular aircraft will decide
.the size, speed, weight carrying capacity, noise nuisance, circ1ing radius,
etc.
(13) Tyre pressure and contact area:
The tyre pressure and the wheel load will give an indication of the
width, type and strength of pavement required for the different types of aircraft.
Characteristics of the jet aircraft:
In addition to the general features of conventional aircrafts, the jet
aircrafts and other high-speed aeroplanes possess the following additional
characteristics:
(1) Channelization
(2) Fuel spilling
(3) High-pressure tyres and small contact areas
(4) High velocities
(5) Hot blasts
(6) Noise
(7) Porpoising effect
(8) Pumping of the joints
(9) Sucking effect.
Each of the additional features of the jet aircrafts will now be briefly
described.
(1) Channelization: The channelization occurs
on the narrow transverse widths of the pavement due to movement of the
landing-gear system. To avoid this effect, it becomes necessary to provide
heavy 'duty pavements in the channelized areas.
(2) Fuel spilling: The spilling of fuel occurs
when the engine is shut down or is losing speed. It causes dissolution of
bitumen. The tar is comparatively insoluble in the jet fuel. The maximum damage
occurs to the aprons and taxiways.
(3) High-pressure tyres and smell contact areas: The loads on the wheels are
very high and it results into tyre pressure of 15 to 30 kg/cm2 as compared to 3
kg/cm2 in the case of DC-3. The small contact area causes high punching effect
on the pavement and it has to be designed accordingly.
(4) High velocities: The tremendous speed of the
jet blast effects the shoulders and hence, a width of about 8 m on either side
of full strength pavement should be provided with dense turf on a thin
bituminous pavement. The texture of the surface material should be rugged i.e.
made uneven and rough to withstand disintegration from the let blast.
(5) Hot blasts: The heat of the blasts
which will cause damage to the pavement surface will depend on the height of
the tail pipe from the ground and the angle at which it is resting. Just as in
case of fuel spilling, the maximum damage occurs to the aprons and taxiways.
The plain concrete, rubberised tar concrete and asphaltic concrete have been recommended
for the construction of aprons and taxiways to bring down to' minimum the
effect of hot blasts and fuel spilling.
(6) Noise: The problem of unbearable noise during take off and
landing of the jet aircrafts is very serious and care should be taken to keep
the urban development sufficiently away from the approach flight.
(7) Porpoising effect: Due to various reasons such
as improper compaction of the subgrade, use of flexible type of gears, impact
of heavy wheel loads, etc., there are depressions and undulations on the
pavement. This effect is known as the porpoising effect and it results
into the longitudinal bouncing of an aircraft between the nose and main landing
gear. To avoid this effect, it becomes necessary to provlde rigid type pavement
in place of the flexible pavement.
(8) Pumping of the joints: When the rigid pavements are
built on clay subgrades, the mud which is a mixture of subgrade material and
undrained water may come out through the joint cracks and edges under the
repeated blows of heavy loads. The pumping of joints will result in loss of
subgrade material and as there is loss of support from below, the pavement
starts cracking.
(9) Sucking effect: The jet. engines are likely
to be damaged badly by the debris sucked into the air-intake.
Civil and military aircrafts:
As the functions of civil and military aircrafts are different, it is
natural that they possess divergent characteristics. The main aim of the civil
aircraft is to earn from the commercial activity and hence, the design is aimed
to grant as much comfort as possible to the passengers. The amenities may
include efficient ventilation, comfortable chairs, sanitary provision,
refreshments, meals on long journey, less noise of engine, air-conditioning,
etc.
At the same time, it should be seen that running cost and maintenance cost
are economical to compete with other companies.
The military aircrafts are designed as the fighter planes during
emergency or war. The essential characteristics of such aircrafts would be
weight carrying capacity, manoeuvrability, speed, rapid climbing, effective
equipment, etc. In fact, the entire layout of the military aircraft is made to
achieve its fier-ce or cruel purpose.
The Britishers acknowledged the courage and value of the Indian pilots
during. World War I and Indian Sand hurst Committee was set up with the
objective of providing military education to the Indian youth. The Indian Air
Force (IAF) was finally formed on 8 October, 1932 and at present, it is the
fourth largest airforce in the world. The onus of national security falls on
the IAF and since its inception, it has risen befittingly to every challenge
posed - be it in war or in peace time duties. Each day of IAF starts on a war
footing to take off at the shortest possible time. Most important in armed forces
is the human resources and IAF is proud to possess the same at par with the
best in the world.
Classification of aerodromes:
The aerodromes in India are classified as follows:
I. (a) Central Govt.
aerodromes.
(b) Privately owned licensed aerodromes,
II. (a) State Govt.
aerodromes normally maintained in a serviceable condition.
(b) State Govt. aerodromes not necessarily maintained in a serviceable
condition.
III. Air force aerodromes
available for limited civil use.
An Air force aerodrome is generally not expected to be used for scheduled
or non-scheduled air service nor even for local flights or flying displays. The
classification is based on the use by the civil aircrafts and military
aircrafts.
Classification of airports:
The airports are classified by various agencies, the most popular one
being by ICAO. The airport classification aims at achieving the uniformity in
the design standards. The classification by ICAO is based in the following two
ways:
( 1) The code letters A to E
are used, as shown in table 1-4, to indicate basic runway length, width of
runway pavement and maximum longitudinal grade.
(2) The numbers 1 to 7 are mentioned, as shown in table 1-5, to indicate
single isolated wheel load and tyre pressure.
Thus, an airport classified as B-2 would have basic runway width between
1500 m to 2099 m and would be capable of handling single isolated wheel load of
34000 kg with a tyre pressure of 7 kg/cm2.
Flying activities:
The most flexible means of transport is flying and the possible flying
activities can be classified as follows:
(1)
Military operational flights: These flights are for
flight training or for tactical flights in connection with light bombing, heavy
bombing, patrol, observation, photography, transport of personnel, medical aid,
etc.
(2)
Non-scheduled commercial flights: These flights are not
according to any plan nor at a particular fixed time. They are carried out for
scientific research, crop dusting, aircraft testing, aerial photography, aerial
police, etc.
(3)
Personal flights: These may be local or
across the country, aircraft sales, glider and autogiro.
(4)
Scheduled commercial flights: These flights operate
according to a certain plan at a fixed time. They may be on domestic or on
international routes.
QUESTIONS
1. What is the meaning of term transport?
2. What is the economic significance of transport?
3. Give illustrations showing the social significance of transport.
4. What are the serious drawbacks of transport?
5. Mention the advantages of air transport.
6. Enumerate the disadvantages of air transport.
7. Write short notes on:
(1) ICAO (9)
Fuselage
(2) IAAI (10) Propeller
(3) Beaufort scale (11)
Empennage
(4) Parachute (12) Wings
(5) Instrument landing system (13)
Aircraft weight
(6) Standard atmosphere (14)
Fuel spilling
(7) Open sky policy. (15) Jet blast
(8) Flaps
8. Briefly outline the history of aviation.
9. Mention the worth noting events with respect to progress in aviation
after the First World War.
10. Write a critical note on air transportation in India with special reference
to the civil aviation department.
11. Draw a neat sketch showing the component parts of an aeroplane.
12. Define the following terms:
Aerodrome; Airport capacity; Apron; Blast pads; Clearway; CTOL; Flight
time; Heliport; Mach number; STOL; Stopway; Transition surface; Zoning.
13. What are the advantages of using more than one engine in an aeroplane?
14. Describe the movement of an aircraft in three principal axes with
the help of a neat sketch.
15. Describe in detail the tricycle undercarriage.
16. What are the characteristics of a conventional type aircraft?
17. How is the minimum turning radius decided?
18. Explain with the help of a neat sketch the principal dimensions of
an aircraft.
19. What are the factors affecting takeoff and landing distances?
20. What are the characteristics of the jet aircrafts?
21. How are aerodromes classified in India?
22. Give the classification of airports as per ICAO.
23. How can the flying activities be classified?
24. Differentiate between the following:
(1)
National defence and national unity
(2)
Subsonic aircraft and supersonic aircraft
(3)
Airfield and airport
(4)
Aeroplane and airship
(5)
Approach area and approach surface
(6)
Boundary lights and boundary markers
(7)
Control area and control tower
(8)
Design landing weight and design takeoff weight
(9)
Landing area and landing strip
(10)
Taxiway and terminal area
(11)
Turbo jet and turbo propulsion
(12)
Pitching and yawing
(13)
Air speed and ground speed
(14)
Pay load and zero fuel weight
(15)
Trip fuel and fuel reserve
(16)
Civil and military aircrafts.
(17)
PNdB and EPNdB.
25. Give reasons for the following:
1)
The transport has been recognised as a great public
utility service.
2)
The transport has a great impact on distribution.
3)
The lands enjoying better transport facilities will
appreciate considerably in their values.
4)
The air transport proves to be the most expensive.
5)
The I.L.S. provides lateral and vertical guidance
to the aircraft during landing.
6)
The jet engine has been universally recognised as
proper mode of aircraft propulsion.
7)
The indicated speed is found slightly less than the
true air speed.
8)
The deteriorating effect on the bituminous pavement
by the commercial aircraft is practically negligible.
9)
It is necessary to know the minimum turning radius
of an aircraft.
PDF Notes
PDF Notes
Comments
Post a Comment