AVIATION HISTORYLecture 9: Speeds of Flight

Mach Number

Speed of sound: How fast the sound waves travel. At sea level, 760 miles per hour (mph) Speed of sound decreases as the altitude increases

Mach number are used to show the pilot’s speed in comparison to speed of sound.

Speeds of Flight

Speeds of flight can be classified based on Mach Numbers to 4 categories: Subsonic Transonic Supersonic Hypersonic

Subsonic

Aircraft speeds which are very much less than the speed of sound

The Mach number M is much less than one, M << 1.

2 categories:

1. Medium Speed (100-350mph) Small planes such as crop dusters and

seaplanes are examples of planes that travel at this speed

2. High Speed (350-750mph) Most of the commercial aircrafts that are used

for passenger & cargo

Transonic Aircraft travelling between Mach 0.8

and Mach 1.0 (0.8<M<1.2)

Supersonic

Flying faster than the speed of sound. Faster than Mach 1 (1.2<M<5.0).

Majority supersonic aircraft designed for high speed aircraft, military & experimental.

Example: Concorde

Hypersonic

Greater than Mach 5. This is more than five times the speed of sound.

It is the speed traveled by rockets and the space shuttle as they go into orbit.

Supersonic Military: SR-71 Blackbird Role: Strategic Reconnaissance Primary users: United States Air Force NASA The world's fastest aircraft. Advanced, long-range, Mach 3 Was in service from 1964 to 1998 Number built: 32

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 the Concorde , and the only other design built in quantity was the Tupolev Tu-144 .

The last passenger flight of the Tu-144 was in June 1978, and the Concorde's last flight was on 26 November 2003 .

As of 2005 , there are no more SSTs used in regular commercial service.

British-French Concorde SST

Manufacturers: BAC (now BAE Systems) , EADS.

Introduction: 21 January 1976 Retired: 26 November 2003 Primary users

British Airways Air France

Number built: 20 Unit cost: £23 million in 1977

Fastest Commercial Aircraft: Concorde

Advantages of Supersonic AircraftAdvantages of Supersonic Aircraft

High Speed Double-delta shaped wings- to gain

more lift. Droop-nose section for improved

visibility in landing Weight Saving

Aircraft skin was made from Aluminium Fully electrically controlled fly-by-wire

flight controls systems

Explain the reasons why airliners have failed to go supersonic?

Factors about airliners have failed to go supersonic

1. High operating costs – high fuel consumption

2. Takeoff noise – environmental issues

3. Poor range – uneconomical

4. Aerodynamics – airframe design

5. Structural issue

6. Need to operate aircraft over a wide range of speed

High operating costs

High fuel consumption, thus higher ticket costs. Low passengers demand.

Lower passenger capacities due to the aerodynamic requirement for a narrow fuselage.

Both Concorde and the Boeing 747 use approximately the same amount of fuel to cover the same distance, but the 747 can carry more than four times as many passengers.

Takeoff noise

High engine noise levels, associated with very high jet velocities used during take-off, disturbing 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 airline trying to increase passenger volume

This means that SST can not cover many routes.

Aerodynamics (Drag increases) 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 to high fuel cost.

Structural issues

SST speeds demand narrower wing and fuselage designs, thus are subject to greater stresses and temperatures .

SST also require a much stronger (and therefore heavier) structure to operate at the high altitudes.

Need to operate aircraft over a wide range of speeds The aerodynamic design of a supersonic

aircraft needs to change with its speed for optimal performance. Thus, SST would ideally change shape during flight to maintain optimal performance at both subsonic and supersonic speeds – e.g. swing wing

Such a design would introduce complexity which increases maintenance needs, operations costs, and safety concerns.

Aircraft Types

Military Aircraft: Swing Wings of F-14 Tomcat

fighterPassenger/ Cargo Aircraft

Airbus A380

V/STOL( Vertical and short take-off and landing) Aircraft

Aircraft Utilization

Military Fighters Transport Helicopter Reconnaissance

Private Aircraft VIPs Personal Crop spraying

Airlines Passengers Cargo

Aircraft Types

Tilt Rotor plane’s

Business Jets

Military

Fighter: Detecting & attacking enemy targets Air to air missiles/guns Air to ground: Bombs, Missiles Supplying weapons to other aircraft Transport: Soldiers, VIP/VVIP Helicopters with rapid fire machine guns Reconnaissance Air to air refueling

Sidewinder AIM-9

Missile

Military Helicopter

Refueling an airplane in mid-air

Military aircraft

Black WidowWorld’s Smallest Spy

Aircraft

Northrop B-2 Stealth Bomber

Observation Aircraft

Private Aircraft

Light aircraft owned or rented by the pilot. Used for a wide range of commercial tasks, such

as flight training, passenger and freight transport, policing, crop spraying and medical evacuations.

Crop Spraying Medical Evacuations