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Advantages and Limitations of Supersonic Planes 2015 SEMINAR REPORT ADVANTAGES AND LIMITATIONS OF SUPERSONIC AIRCRAFTS Submitted by: 153106004 Page 1

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Page 1: Supersonic Planes

Advantages and Limitations of Supersonic Planes 2015

SEMINAR REPORT

ADVANTAGES AND LIMITATIONS OF SUPERSONIC

AIRCRAFTS

Submitted by:

Sana Syed(153106004)

M.Tech (Design)

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Advantages and Limitations of Supersonic Planes 2015

Mech. Engg. Dept.

IIT BOMBAY

ADVANTAGES AND

DISADVANTAGES OF

SUPERSONIC AIRCRAFTS

ABSTRACT:

A detailed study of the operational and

ergonomic requirements of a supersonic

aircraft for various applications, either

military or commercial passenger flights

is essential to understand the nuances of

supersonic flight. Further, the control of

various factors that affect supersonic

flights and its mitigation techniques is

essential to reduce sonic boom, achieve

low supersonic wave drag, and offer

high subsonic performance. This report

discusses the various advantages and

limitations of a supersonic aircraft.

Further, it introduces a new innovative

concept of a supersonic bi-directional

(SBiDir) flying wing (FW) concept,

which has the potential to overcome the

major limitations of supersonic aircraft,

i.e. sonic boom and efficiency.

According to the case study for the

SiBiDir FW, it is possible to reduce or

completely eliminate sonic boom and

achieve low supersonic wave drag.

INTRODUCTION :

Supersonic flights have been a popular

choice for military applications since

common enemy surveillance radars are

unable or find it quite difficult to detect

objects flying at supersonic speeds [1].

In addition, the commercial sector has

been interested in these flights due to its

great potential to reduce the inter-

continental travel time [2].

However, various disadvantages are

associated with Supersonic flight, the

major factors of these being the sonic

boom, supersonic wave drag and low

efficiency during supersonic flight. The

Concorde, which was the only

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Advantages and Limitations of Supersonic Planes 2015

commercialized civil Supersonic

aircraft, was discontinued from service

in 2003 due to high operating costs and

infeasibility constraints. Since that time,

various efforts have been made to make

supersonic commercial flights

economically and environmentally

feasible for passenger flights. The

introduction of the concept of SBiDir is

one such effort in this direction, which

has the potential to overcome and

possibly eliminate the drawbacks of a

conventional supersonic flight.

SUPERSONIC FLIGHT : A BASIC

INTRODUCTION

A bullet fired from a gun travels at supersonic

speeds. This picture shows a bullet and the air

flowing around it. The bullet is traveling at 1.5

times the speed of sound.

Credits: Andrew Davidhazy/Rochester

Institute of Technology

An F/A-18 Hornet aircraft speeds up to

supersonic speed. The Hornet is flying through

an unusual cloud. This kind of cloud sometimes

forms as aircraft break the sound barrier.

Credits: Ensign John Gay, USS

Constellation, U.S. Navy

The aerodynamics of supersonic flight

is called compressible flow because

of the compression

(physics) associated with the shock

wavesor "sonic boom" created by any

object travelling faster than sound.

Supersonic aircraft are the

aircraft that travels with the

speed more than mach 1. Mach

1 is the speed of sound. The

aircraft travelling with the speed

very large than the speed of

sound is known as hypersonic

aircraft (above mach 5). In the

current global economy, where

individual companies as well as

business partnerships, transcend

national boundaries, and

mandate collaborations across

the globe, the required time for

travel has become a valuable

resource, prompting interest in

high speed transportation.

Compared to today’s typical

transport aircraft mission

profiles with cruise flight speeds

of Mach M=0.8 and design

ranges of 4000 nautical miles

(nm), up to a 55% time savings

can be achieved by increasing

the cruise speed to M=1.8 [1].

However, a successful

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supersonic aircraft design has to

overcome numerous challenges

to meet opposing requirements.

1. History:

60 years ago Chuck

Yeager, captain of United States

air force, broke the sound barrier

while flying his bell X-1 aircraft.

That was the beginning of the

supersonic flight era. Since then,

numerous advances have been

made, from the introduction and

design improvements of military

supersonic jets to the innovation

aimed at passenger supersonic

flight. Concorde was the first

supersonic aircraft used for

passenger travel [2].

Fig.1 The Concord Jet

Concorde ceased to fly from

2003 because of following

reasons.

1. Sonic boom, a very loud

shockwave that sounds a lot

like an explosion when

aircraft breaks the sound

barrier.

2. Fall in number of passengers

travel because of high cost.

3. Large amount of fuel used to

propel the aircraft.

4. High maintenance cost.

5. Air pollution (exhaust

emission).

2. Functional requirements:

1. The aerodynamics of

supersonic flight are

dramatically different

from those of subsonic

flight (i.e., flight at

speeds slower than

that of sound). In

particular,

aerodynamic drag

rises sharply as the

aircraft passes the

transonic regime,

requiring much greater

engine power and

more streamlined

airframes.

2. To keep drag low, wing

span must be limited,

which also reduces the

aerodynamic efficiency

when flying slowly.

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Since a supersonic

aircraft must take off

and land at a relatively

slow speed, its

aerodynamic design

must be a compromise

between the

requirements for both

ends of the speed

range.

3. The structural sizing needs

to balance minimum weight

with adequate safety margin

to support high loads at high

speed.

4. Engine must be

compact and should

consume less fuel.

5. The need for efficient

fuels is tied to the

need to reduce the

fuel contribution to the

weight of the aircraft,

both in terms of fuel

weight and the weight

of the rest of the

aircraft using this fuel

for propulsion,

because the weight is

a major contributor to

the sonic boom and

the drag. The fuel and

propulsion system also

affects the emission

levels of NOx at high

altitudes as well as the

cruise efficiency,

leading to changes in

aircraft

configuration[2].

6. Environmental

constraints are

becoming more and

more stringent. The

high altitude emission

should be as low as

possible. Again the

sound produce by

supersonic aircraft

while taking and

landing should be

within the limit, so that

it is not harmful to

human beings. The

sound produce by

sonic boom should also

be less[3].

7. The heat generated by

friction as the air flows

over the aircraft is

very high therefore the

material should have

the capacity to

withstand the high

temperature.

8. The ticket price should

be low.

3. Advantages of supersonic

aircraft:

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1. The value of time has been

growing, resulting in a

premium being placed on the

ability to get to the

destination faster.

a. Supersonic aircraft

reduces travel time for

business leading to

increased productivity. It

also shortens travel time

for leisure.

b. It has the ability to

provide rapid response in

disaster situations and

faster delivery of time-

critical goods[2].

2. Supersonic aircraft quickly

delivers the time-critical

cargo which could save

lives, as in the case of organ

transplants[2].

3. It is also useful for defence

in military.

a. Supersonic speed with

manoeuvrability

provides amazing dog

fighting ability to fighter

aircraft. 

b. Supersonic aircraft can

quickly and safely attack

enemy targets. 

c. Supersonic speed allows

fighter jets to intercept

enemy airplanes.

Supersonic interceptors

can quickly reach their

target if the target is

slow, in a matter of

minutes if they are close

by. (The hijacked

airplanes of 9/11 should

have been intercepted.)

4. Disadvantages:

1. Sonic boom:

A major problem, which all

supersonic aircrafts face, is

sonic boom. The term sonic

boom is used to refer to the

shocks caused by the

supersonic flight of an

aircraft. Sonic booms

generate enormous amounts

of sound energy, sounding

much like an explosion[4].

Sonic boom is the reason

why supersonic flights are

not allowed over populated

areas.

Fig.2 Propagation of sound waves produced by

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aircrafts at different speeds

When aircraft travels at the

speed less than sound, the

sound it creates will

propagate in all the

directions ahead of the plane

as shown in fig.2 when it

travels with mach 1 the wave

propagation is also shown in

fig.2. Now when it travels

with the speed greater than

sound, it travels faster than

the sound wave it creates and

it breaks the sound barrier

and it forms the cone like

structure behind the aircraft

as shown in fig.2. The visual

impact of the sonic boom is

shown in fig.3. It is because

of the speed with which

aircraft is travelling causing

the pressure to drop

significantly which in turn

reduces the temperature

causing condensation in the

air.

Fig.3 Sonic Boom

2. Emission:

Atmospheric effects of

supersonic aircraft depend

on the number of aircraft, the

altitude of operation, the

exhaust emissions, and the

background chlorine and

aerosol loading. Emissions

from the engines are

functions of engine

technology and the operation

of the aircraft on which the

engines are installed.

Primary engine exhaust

products are C02 and H20,

which are directly related to

the burned fuel, with minor

variations due to the precise

carbon-hydrogen ratio of the

fuel. Secondary products

include NOx (=NO + N02),

CO, unburned and partially

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burnt fuel hydrocarbons

(HC), soot

particulates/smoke, and SOx.

NOx is a consequence of the

high temperature in the

engine combustor; the

incomplete combustion

products (CO, HC, and

soot/smoke) are functions of

the engine design and

operation and may vary

widely between engines.

SOx is directly related to

fuel composition.

Rough estimates of the

impact of future supersonic

operations (assuming 500

aircraft flying at Mach 2.4 in

the stratosphere and emitting

15 grams of nitrogen oxides

per kilogram of fuel)

indicate an increase of the

North Atlantic flight corridor

concentrations of NOx up to

about 250%, water vapour

up to about 40%, S Ox up to

about 40% , H2S04 up to

about 200%, soot up to about

1 00%, and CO up to about

20%[5].

Since supersonic aircraft

engines may emit significant

amounts of NOx, the fear is

that large fleets of

supersonic aircraft flying at

stratospheric levels, where

maximum ozone

concentrations exist, might

seriously deplete the

stratospheric ozone layer,

leading to increased

ultraviolet radiation flux on

the biosphere. Also, climate

sensitivity studies have

shown that ozone changes in

the upper troposphere and

lower stratosphere will have

greater radiative effects on

changing surface and lower

tropospheric temperatures

than would ozone changes at

other levels[5].

3. Climatic Effects:

Supersonic aircraft

emissions include

constituents with the

potential to alter the local

and global climate. Species

important in this respect

include water vapor, NOx

(through its impact on 03),

sulfur, soot, cloud

condensation nuclei, and

C02 .

Increases of C02 and water

vapor, and alterations of

ozone and cirrus clouds have

the potential to alter in situ

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Advantages and Limitations of Supersonic Planes 2015

and global climate by

changing the infrared

(greenhouse) opacity of the

atmosphere and solar

forcing[5].

Sulfuric acid:

Sulfuric acid, which results

from SOx emissions, may

cool the climate through

producing aerosols that give

increased scattering of

incoming solar radiation.

Effect of ozone depletion:

The impact of ozone changes

on the radiation balance of

the surface troposphere

system depends on the

vertical distribution of the

ozone changes. Reduction in

tropospheric and lower

stratospheric ozone tends to

cool the climate, by reducing

the atmospheric greenhouse

effect. Reduction in middle

and upper stratospheric

ozone tends to warm the

climate, by allowing more

shortwave radiation to reach

the surface.

Water Vapour:

Water vapour is the primary

atmospheric greenhouse gas.

Increases in water vapor

associated with aircraft

emissions have the potential

to warm the climate at low

tropospheric levels, while

cooling at altitudes of

release, due to greater

thermal emission. The

effects are largest when

water vapor perturbations

occur near the tropopause as

is likely to be the case[5].

4. Some supersonic fighter jets

use afterburners to gain

speed, which can reveal

there position on enemy

radar due to heat signatures.

5. The heat generated by

friction as the air flows

over the aircraft limits

the speed of aircraft to

around mach 2.2. It

implies that new

material should be

developed such that it

should withstand the

heat[6].

6. High Wave Drag, high fuel

consumption/cost[7].

7. Low Subsonic performance,

long takeoff/landing

distance[7].

5. Mitigation techniques:

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1. Sonic boom:

The following are some

factors affecting sonic boom

strength[6]:

a. Aircraft weight, shape

and length:

The bigger the aircraft is,

the more air molecules

push aside. Thus a big

aircraft will produce a

stronger sonic boom.

b. Aircraft altitude:

The altitude of the

aircraft and the strength

of the sonic boom are

reciprocal. As the

altitude increases, the

strength of the sonic

boom decreases.

c. Aircraft maneuvers:

Maneuvers such as

pushovers, S-turns and

accelerating can amplify

the intensity of the shock

wave. Hills, valleys and

other topographic

features can create

multiple reflections of

shock waves thus

affecting intensity.

d. Location in sonic boom

carpet [8]:

Special topographic

features in each area

such as mountains, hills

and valleys can create

multiple reflections of

shock waves thus

affecting intensity.

e. Attitude: orientation of

the aircraft’s axes

relative to its direction of

motion[9].

Quiet Spike project [10] showed

that by extending the length of

the nose, and by changing the

position of the wings, sonic

boom would be reduce to about

55 dB[11]. But the capacity of

Quiet Supersonic Jet suggested

by Gulfstream is about 8-11

passengers. Extended and

shaped nose of the aircraft will

propagate the shock waves. The

nose will break up the initial

shock into a series of very weak

shocks.

2. Emission:

Hydrogen fuel can be

used to reduce the

emission and it is also

very light. If more

efficient propulsion

systems are created

then smaller amounts

of hydrogen fuel could

be used for the same

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Advantages and Limitations of Supersonic Planes 2015

flight distance.

Hydrogen fuels do not

eliminate pollution, but

their use significantly

reduces its level.

Development of new

synthetic fuels that are

highly efficient,

produce less

pollutants, and are

inexpensive appears to

be very promising[2].

3. The lift/drag ratio of a

supersonic jet is much

lower than that of a

subsonic aircraft.

Reducing the drag

could in part be

accomplished by

reducing the weight of

the aircraft. The new

light weight,

innovative composite

materials, in particular

those that can

withstand high

temperatures could be

a part of solution. It is

one of the ways to

reduce fuel needed per

passenger-mile[2].

References:

[1] Deremaux, Y., 2009, “Why a

Small Size Supersonic Transport

Aircraft? Objectives and Trade-

Offs,” HISAC 2009 Conference,

Paris.

[2] Making the Small Supersonic

Airliner

a Reality: Obstacles and Solutions.

Gail M. Krutov, Bard High School,

New York, NY.

NASA Fundamental Aeronautics

Student Competition 2008-2009

Academic Year.

[3] Joel brezillon, Gerald carrier and

Martin laban, “Multidisciplinary

optimization of supersonic aircraft

including low-boom considerations,”

journal of mechanical design, ASME,

October 2011,vol.133/105001.

[4] Wikipedia, Sonic Boom,

Available at:

http://en.wikipedia.org/wiki/Sonic_

boom.

[5] Scientific Assessment of ozone

depletion:1994. World

Metrological Organisation Global

Ozone Research And Monitoring

Project-Report No:37( US

department of commence/National

Oceanic And Atmosphereic

Administration/NOAA Research).

Chapter 11, book by A.Wahner and

M.A.Geller.

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Advantages and Limitations of Supersonic Planes 2015

[6] NASA Fundamental

Aeronautics Student Competition,

Supersonic flight project by

Emmanuel Vasileios and Dimitrios

Tsounis, high school of Kareas

(Greece).

[7]Toward Zero Sonic-Boom and

High Efficiency Supersonic Flight: A

Novel Concept of

Supersonic Bi-Directional Flying

Wing. Gecheng Zha, Hongsik Im ,

Daniel Espinal,

University of Miami, Dept. of

Mechanical and Aerospace

Engineering,AIAA Paper 2010-1013.

[8]Martin K. Chan, “Supersonic

Aircraft Optimization for

Minimizing Drag and Sonic

Boom”, Available at:

http://aero.stanford.edu/Reports/Ma

rtinFinalThesis.pdf, 2003

[9] David Gallo, AP Physics project

on propagation of sonic boom,

Available at:

http://library.thinkquest.org/

12228/page6.html

[10] NASA, Supersonic Jousting,

Available at:

http://www.nasa.gov/vision/earth/

improvingflight/

supersonic_jousting.html Accessed

10 April 2004.

[11] Preston A. Henne, Sr VP

Programs, Engineering, & Test

Gulfstream Aerospace Corp

Available at:

http://www.aiaa.org/events/aners/Pr

esentations/ANERS-Henne.pdf,

Accessed May 2005.

ake supersonic co, Supersonic flight is

one of the four speeds of flight.

Objects moving at supersonic speeds

are going faster than the speed of

sound. Supersonic includes speeds up

to five times faster than the speed of

sound. When the aircrafts exceed the

speed of sound, the pressure wave’s

mix and form shock waves that travel

forward from where they were

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Advantages and Limitations of Supersonic Planes 2015

released. As the plane flies at

supersonic speed, it continuously

generates shock waves, dropping

sonic boom along the flight path. The

sonic boom is swept backwards as it

travels way from the plane. This

boom later hits the ground in front of

it. The aerodynamics of supersonic

flight is called compressible

flow because of the compression

associated with the shock wavesor

"sonic boom" created by any object

travelling faster than sound.

ADVANTAGES :

- With the use of delta-wing design, it

can attain a high angle of attack at low

speeds, which generates a vortex on

the upper surface which greatly

increases lift and gives a lower

landing speed.

-Supersonic speed with

maneuverability provides amazing

dog fighting ability to fighter aircraft.

- The major advantage of a modern

supersonic commercial aircraft over

the commercial subsonic aircraft is

more passengers carried on overseas

flights per day per aircraft

- With the use of a variable-geometry

wing, commonly known as the

"swing-wing," which spreads wide for

low-speed flight and then sweeps

sharply, supersonic aircraft able to

take off and land at a relatively slow

speed.

- Most supersonic designs use

aluminum alloys such as Duralumin,

which are cheap and easy to work.

DISADVANTAGES :

- Expensive flights (passenger use) 

- Supersonic flights cause sonic boom

and noise pollution. 

-Some supersonic fighter jets use

afterburners to gain speed, which can

reveal their position on enemy radar

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due to heat signatures

- Supersonic flights uses aluminum

alloys which loses their strength

quickly at high temperatures. 

FUNCTIONAL REQUIREMENT :

1) Supersonic airfoils : -

A supersonic airfoil is a cross-section

geometry designed to

generate lift efficiently at supersonic

speeds. The need for such a design

arises when an aircraft is required to

operate consistently in the supersonic

flight regime. Supersonic airfoils

generally have a thin section formed

of either angled planes or opposed

arcs, with very sharp leading and

trailing edges. The sharp edges

prevent the formation of a detached

bow shock in front of the airfoil as it

moves through the air.This shape is in

contrast to subsonic airfoils, which

often have rounded leading edges to

reduce flow separation over a wide

range of angle of attack. A rounded

edge would behave as a blunt body in

supersonic flight and thus would form

a bow shock, which greatly

increases wave drag. The airfoils'

thickness, camber, and angle of attack

are varied to achieve a design that will

cause a slight deviation in the

direction of the surrounding airflow.

2) Propelling Nozzle :

Propelling nozzles accelerate the

available gas to subsonic, transonic,

or supersonic velocities depending on

the power setting of the engine, their

internal shape and the pressures at

entry to, and exit from, the nozzle.

The internal shape may be convergent

or convergent-divergent (C-D).C-D

nozzles can accelerate the jet to

supersonic velocities within the

divergent section, whereas a

convergent nozzle cannot accelerate

the jet beyond sonic speed. Propelling

nozzles may have fixed geometry, or

they may have variable geometry to

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give different exit areas to control the

operation of the engine when

equipped with an afterburner or a

reheat system. When afterburning

engines are equipped with a C-D

nozzle the throat area is variable.

Nozzles for supersonic flight speeds,

at which high nozzle pressure ratios

are generated,also have variable area

divergent sections

3) Scramjet :

-A scramjet (supersonic combusting r

amjet) is a variant of a ramjet air

breathing jet engine in which

combustion takes place in

supersonic airflow.

- As in ramjets, a scramjet relies on

high vehicle speed to forcefully

compress the incoming air before

combustion (hence ramjet), but a

ramjet decelerates the air

to subsonic velocities before

combustion, while airflow in a

scramjet is supersonic throughout the

entire engine. This allows the scramjet

to operate efficiently at extremely

high speeds: theoretical projections

place the top speed of a scramjet

between Mach 12 (8,400 mph;

14,000 km/h) and Mach 24

(16,000 mph; 25,000 km/h).

MITIGATION TECHNIQUES:

1)JET NOISE REDUCTION :

Jet aircraft noise is a combined effect

of aircraft noise and the jet engine.

And this can be reduced by

Controlling The Source i.e. Reduce

exhaust velocity and Enhance jet

mixing (like chevrons). And one of

the other possible ways to reduce jet

noise and aircraft noise is to make use

of bypass turbofan engines instead of

turbojet engines as the noise created

by turbofan engines is lesser than that

generated by turbojet engines.

2)SONIC BOOM REDUCTION:

When an aircraft passes through the

air it creates a series of pressure

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waves in front of it and behind it,

similar to the bow and stern

waves created by a boat. These waves

travel at the speed of sound, and as

the speed of the object increases, the

waves are forced together, or

compressed, because they cannot get

out of the way of each other.

Eventually they merge into a single

shock wave, which travels at the

speed of sound.For sonic-boom

mitigation can be achieved by

increasing the wing dihedral angle—

the angle between the left wing and

right wing—on the ground sonic-

boom noise

3)SHOCK WAVE MITIGATION:

To modify the shock structure and to

move the shock wave upstream, the

flow perturbations have to move

upstream beyond the original shock

front. Shock wave appears in the form

of a steep pressure gradient. It

introduces a discontinuity in the flow

properties. plasma spike serves the

same purpose, which encounters the

flow in the region upstream of the

location of the original shock front20.

The induced flow perturbations from

the plasma spike coalesce with the

flow perturbations from the object

into a new shock front, which replaces

the original one located behind it.

4) REDUCTION IN DRAG:

drag reductions allow lower fuel

requirements and can lead to reduced

operating costs and reduced sonic

boom and noise effects. The drag on

supersonic vehicles can be classified

into three different categories: 1) skin-

friction drag, 2) drag caused by lift,

and 3) zero-lift bluntness (thickness-

wave) drag. Linearised supersonic

theory indicates that for an airfoil of a

given thickness the shape that gives

minimum zero-lift bluntness drag is

the sharp diamond airfoil. However,

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very sharp leading edges are not

practical. During takeoff, landing,

climb and maneuvering light, blunted

leading edges are desirable so that

flow separation is prevented .this is

required because at higher speed there

are chances that due to higher heating

the sharp edge would melt.

REFERANCES :

1)  Bill Gonston, "The

Development of Jet and Turbine

Aero Engines", 2006, 4th

edition, pp. 160.

2)

http://www.brown.edu/research/p

rojects/scientific-computing/sites/

brown.edu.research.projects.scien

tific-computing/files/uploads/

Demonstrating%20Shock

%20Mitigation%20and%20Drag

%20Reduced%20Pulsed

%20Energy%20Lines.pdf

3) http://eeweb.poly.edu/faculty/

kuo/publications/Mitigation-

review.pdf

4) http://web.stanford.edu/group/

frg/publications/recent/sonic-

boom3.pdf

5) http://

www.langleyflyingschool.com/

Pages/

CPGS+4+Aerodynamics+and+T

heory+of+Flight+Part+1.html

6) http://

digitalcommons.calpoly.edu/cgi/

viewcontent.cgi?

article=1081&context=aero_fac

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