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AVIATION HISTORY
Lecture 9: Speeds of Flight
By: Zuliana Ismail, 2010
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Introduction
After the invention of the airplane,
designers and engineers created new
aircraft for a variety of uses. Airplanes became a part of daily life.
They were used regularly to ship cargo
and to transport people.
Over time, the speed of aircraft has
increased.
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Introduction
Aircraft can be grouped based upon how
fast they can fly.
These groups called as speeds of flight or
regimes of flight
There are three basic speeds of flight
which are Subsonic (low, medium and
high), Supersonic and Hypersonic . These include the earliest aircraft to the
most modern.
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Speed of sound and Mach No.
Speed of sound means how fast the sound waves
travel.
Roughly speaking, the speed of sound is 343 m/s (or
1236 km/h, or 768 mph).
When we refer to the speed of sound, we measure it
in Mach numbers.
In the late 19th century, physician named Ernst Mach
developed Mach Number theory.
Mach number are used to show the pilot¶s speed in
comparison to speed of sound.
Mach
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Speed of Sound and Mach No.
If an airplane is flying slower than the speed of
sound, we say it is moving at subsonic speed.
If it is flying faster than the speed of sound, it
is traveling at supersonic speed. So, if an airplane is traveling at the speed of
sound, we say it is flying at Mach 1.
If it is traveling at two times the speed of
sound, we say it is flying at Mach 2.
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Subsonic (0-700 MPH )
Subsonic aircraft
travel below the
speed of sound. The Mach number M
is much less than
one, M << 1.
Subsonic aircraft canbe divided into three:
low speed, medium
speed and high
speed
Low speed
Medium speed
High speed
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Subsonic (Low speed)
Low speed aircraft travel at speeds between 0
and 100 miles per hour (mph).
They were lightweight vehicles with a smallengine or no engine at all.
The aircraft in this group include the earliest
types of aircraft, such as kites, balloons and
early airplanes. Modern aircraft in this speed regime are hang
gliders and ultra lights aircraft.
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Subsonic (Medium speed)
Medium speed aircraft fly
between 100 and 350
mph.
These vehicles are
usually airplanes with
straight, thick wings.
This category includesbiplanes, propeller
planes, helicopters, small
plane like the modern
Cessna
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Subsonic (High speed)
High speed aircraft are the
powerful jet planes that fly
between 350 and 700 mph.
The Boeing 747 Jumbo Jet,
the Lear Jet, the Sikorsky
Blackhawk helicopter and
many fighter planes fly withinthis speed regime.
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Supersonic (760-3500 MPH )
Supersonic aircraft can go faster
than speed of sound.
The range of Mach No. is betweenMach 1 and Mach 5(1.0<M<5.0).
These vehicles have high-
powered jet engines, a sleek
fuselage and super thin wings. The Concorde, the F-15 Eagle,
and the SR-71 Blackbird are some
examples of airplanes that can fly
at supersonic speeds.
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Hypersonic (3500-7000 MPH )
Hypersonic aircraft has Mach
No. greater than 5 (M>5).
This is more than five times the
speed of sound.
These vehicles have high-
powered rocket engines with
short, thin wings. The best known examples of
hypersonic aircraft are the X-15
and the space shuttle
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What is SST (Super sonic
Transport) aircraft?
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SST: Supersonic Transport
A Supersonic Transport (SST) is a civil aircraft
designed to transport passengers at speeds
greater than the speed of sound .
The only SST to see regular service was theConcorde , and the only other design built in
quantity was the Tupolev Tu-144 .
The last passenger flight of the Tu-144 was in June1978, and the Concorde's last flight was on 26
November 2003 .
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Tu-144, first supersonic transport
aircraft (SST),
The Tupolev Tu-144 was the first supersonic
transport aircraft (SST), constructed under the
direction of the Soviet
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Concorde: Fastest Commercial
Aircraft. Primary Users: British
Airways & Air France
First flown in 1969, Concorde service commenced in 1976 and continued for 27
years. It flew regular transatlantic flights from London Heathrow (British Airways)
and Paris Charles de Gaulle (Air France) to New York JFK and Washington Dulles,
flying these routes at record speeds, in under half the time of other airliners.
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Advantages of Supersonic
Transport Aircraft High Speed
Special shaped wings- to gain more lift.
Droop-nose section for improved visibility inlanding
Weight Saving
Aircraft skin was made from Aluminium
Fully electrically controlled fly-by-wire flight
controls systems, no hydraulic system.
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Why Airliners have failed to go
Supersonic?
However, as of 2005 , there are no more
SSTs used in regular commercial service.
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Challenges of Supersonic Transport
Aircraft1. High Costs ± high fuel consumption
2. Narrower fuselage-limited passenger
3. Takeoff Noise ± environmental issues
4. Poor Range ± uneconomical
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High Costs
The faster the speed the higher the air
resistance, thus the higher the drag.
As the drag increases, more power/fuel
require to overcome the drag which lead tohigh fuel cost.
As, SST consume higher fuel, this leads to
higher ticket costs.
As a results, only low passengers demand on
this aircraft services
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Narrower fuselage
SST demand narrower fuselage designs.
Therefore, capacity for passengers on this
aircraft are very limited.
Both Concorde and the Boeing 747 useapproximately the same amount of fuel tocover the same distance, but the 747 can
carry more than four times as manypassengers.
This factor will not give profit to the airlines.
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Takeoff noise
SST has very high engine noise levels,
associated with very high jet velocities used
during take-off.
This noise disturbing the communities near
the airport.
This is an environmental hazard ± Noise
pollution
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Poor range
Range means how far can the aircraft fly with
a tank of fuel.
SST can only carry lesser fuel due to airlinetrying to increase passenger volume.
This means that SST can not cover many
routes.
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Conclusion
The cost of operating supersonic aircraft do
not outweigh the benefits that airlines could
get from them.
Thus, today supersonic transport aircraft
services has stopped.
Only the military consistently use supersonic
aircraft these days.
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Question Bank
a) Write the equation of Mach number and define
the speed of sound.(3M)
b) Explain the CHARACTERISTICS of subsonic,supersonic and hypersonic aircraft. Give
examples for each type. (12M)