AVIATION HISTORY Lecture 8: Speeds of Flight. Introduction After the invention of the airplane, designers and engineers created new aircraft for a variety.

AVIATION HISTORYLecture 8: Speeds of Flight

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 can be 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 small engine 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 includes biplanes, 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 within this speed regime.

Supersonic (760-3500 MPH ) Supersonic aircraft can go faster

than speed of sound. The range of Mach No. is between

Mach 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

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.

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 in landing Weight Saving

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

flight controls systems, no hydraulic system.

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 to high fuel cost.

As, SST consume higher fuel, this leads to higher ticket costs.

As a results, only low passengers demand on this aircraft services

Challenges of Supersonic Transport Aircraft

1. High Costs – high fuel consumption

2. Narrower fuselage-limited passenger

3. Takeoff Noise – environmental issues

4. Poor Range – uneconomical

Narrower fuselage

SST demand narrower fuselage designs.

Therefore, capacity for passengers on this aircraft are very limited.

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.

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 airline trying 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.