lecture 9-speeds of flight

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AVIATION HISTORY

Lecture 9: Speeds of Flight

By: Zuliana Ismail, 2010



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.



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.



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



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.



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



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.



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



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.



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.



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



What is SST (Super sonic

Transport) aircraft?



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 .



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



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.



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.



Why Airliners have failed to go

Supersonic?

However, as of 2005 , there are no more

SSTs used in regular commercial service.



Challenges of Supersonic Transport

Aircraft1. High Costs ± high fuel consumption

2. Narrower fuselage-limited passenger

3. Takeoff Noise ± environmental issues

4. Poor Range ± uneconomical



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



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.



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



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.



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.



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)



Question Bank

a) Define SUPERSONIC TRANSPORT (SST)

Aircraft. Provide examples. (5M)

b) Explain four (4) REASONS why airlinershave failed to go supersonic? (10M)

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