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DETAILED STUDY 3.2: INVESTIGATIONS: AEROSPACE (FLIGHT)
Students should demonstrate the knowledge and skills to:
 apply the concepts of forces, moments and equilibrium to balancing an
aircraft;
 explain lift in terms of Bernoulli’s equation and the rate of change of
momentum;
 explain drag; skin friction drag, pressure drag and principles of thrust;
 analyse aircraft performance including takeoff, climb, descent and cruise;
 use computer models to investigate phenomena associated with flight;
Students are asked to identify a focused problem or research question and formulate
a set of responses to a set of questions.
AEROSPACE (FLIGHT): AN EMERGING AN INNOVATIVE INDUSTRY
The history of sustained powered flight celebrates its one hundredth anniversary in
2003. It is indeed startling that that first sustained powered flight of Wilbur and
Orville Wright on 17 December 1903 lasted 12 seconds and covered 36.6 m which is
less than the wingspan of a Boeing 747 airplane (wingspan of 64.4 m).
http://www.ueet.nasa.gov/StudentSite/historyofflight.html
From those early days to today’s
technologically sophisticated aircraft
represents a huge quantum leap, and the story
of the men and women involved in making the
breakthroughs throughout the history of
powered flight, and those making the
breakthroughs today, is extremely interesting.
www.edwards.af.mil/.../splash/
mar98/cover/spaceage.htm
APPLYING THE CONCEPTS OF FORCES, MOMENTS AND EQUILIBRIUM TO
BALANCING AN AIRCRAFT
To look at forces, moments and equilibrium the following diagrams from the text
Aeroplane General Knowledge and Aerodynamics are very useful. This useful book
is used by Victorian students studying for their private and commercial pilot licences
and is available from:
http://www.aviationtheory.net.au/
The diagram below from Aeroplane General Knowledge and Aerodynamics (Chapter 2:
Forces in Flight, p.11.) shows the equilibrium conditions required in the vertical
direction for the plane to be stable both on the ground and in the air: on the ground
the Weight Force down (acting though the geometric centre of mass of the aircraft) is
balanced by the Reaction Force up, while in straight and level flight the Weight
Force down is balanced by the Lift Force up. These concepts tie in neatly with
Newton’s three laws of motion studied in Area of Study 1: Movement.
The diagram below from Aeroplane General Knowledge and Aerodynamics (Chapter 2:
Forces in Flight, p.11.) illustrates the equilibrium condition in the horizontal
direction. In steady straight and level flight, the Drag Force (caused by air friction)
needs to be balanced by the Thrust Force (provided by the engine).
These two diagrams can be combined to give the diagram below (Aeroplane General
Knowledge and Aerodynamics (Chapter 2: Forces in Flight, p.12.)).
If the lift force is more than the weight force the plane goes up and if the weight force
is more than the lift force the plane goes down. If the thrust force is more than the
drag force then the plane speeds up (accelerates) and if the drag force is more than
the thrust force the plane slows down (decelerates).
Although the Lift Force may be the same magnitude as the Weight Force sometimes
it may not be acting through the same point. Such a misalignment of forces causes an
imbalance. This imbalance is called a turning moment (or torque) and needs to be
balanced say by the tailplane wing or the trim creating a balancing force. Such a
situation is shown in the diagram below (Aeroplane General Knowledge and
Aerodynamics, Chapter 2: Forces in Flight, p. 12.).
http://www.grc.nasa.gov/WWW/K-12/airplane/bga.html
At the ‘howstuffworks’ website there is also a good explanation and useful diagrams
of the four main forces acting on airplanes:
http://travel.howstuffworks.com/airplane1.htm
The Physics of Flight website run by the United States Air Force also contains useful
information and diagrams covering these concept areas:
http://www.usafa.af.mil/dfp/cockpit-phys/cp_pf0.htm
The Dryden Flight Research Centre – Education website has a good Adobe PDF file
titled ‘Flight Testing Newton’s Laws’ which can be downloaded for free and which
covers many of the concepts studied:
http://www.dfrc.nasa.gov/Education/OnlineEd/NewtonsLaws/index.html
Unfortunately, it does not use SI units. A version of the document with the units
converted to SI units is available from RMIT University (Contact Prof Lachlan
Thompson (RMIT Aerospace) who has a number of aerodynamics resources
available on CD, including the SI version of ‘Flight Testing Newton’s Laws’, for a
nominal cost).
EXPLAINING LIFT IN TERMS OF BERNOULLI’S EQUATION AND THE RATE
OF CHANGE OF MOMENTUM
Bernoulli
Daniel Bernoulli (1700-1782), son of a family of famous Swiss mathematicians,
contributed much to our understanding of hydrodynamics. He was the first to
solve the differential equation now known as Bernoulli’s Equation. He held chairs
in anatomy, botany and physics at Basle in Switzerland.
Bernoulli’s Equation
Static Pressure + Dynamic Pressure = Constant Total Pressure (C) and how it relates
to flight is covered in Aeroplane General Knowledge and Aerodynamics (pp.15-17). The
authors introduce air density. They explain, using a non-mathematical treatment,
how lift is created by reaction forces generated via pressure differentials above and
below the wing (which in turn are due to velocity differences in the respective
airstreams).
The Dryden Flight Research Centre – Education website downloadable Adobe PDF
file titled ‘Flight Testing Newton’s Laws’ has a good section on developing lift using
the rate of change of momentum (See page 3.4 of Developing Lift in the Adobe PDF
file):
http://www.dfrc.nasa.gov/Education/OnlineEd/NewtonsLaws/index.html
At the ‘howstuffworks’ website there is a good discussion as well as some useful
diagrams concerning popular explanations of lift, viz:
‘Two of the most popular explanations today are the Longer Path explanation (also known
as the Bernoulli or equal transit time explanation) and the Newtonian explanation (also
known as the momentum transfer or air deflection explanation). While many versions of
these explanations are fundamentally flawed, they can still contribute to an intuitive
understanding of how lift is created.’
http://travel.howstuffworks.com/airplane2.htm
Halliday, Resnick and Walker provide a nice concise explanation (with a clear
diagram) in terms of Newton’s third law (An Airplane Wing p.461, Fundamentals of
Physics Extended with Modern Physics, 4th edn, John Wiley and Sons, 1993).
A useful investigation of the Bernoulli Effect can be undertaken by using the air
stream from a vacuum cleaner (in reverse mode) and placing a number of light balls
(e.g. table tennis balls) and other light objects of various shapes in the air stream.
Some interesting demonstrations of various aspects of the Bernoulli Effect can also be
found at:
http://onezine.s-one.net.sg/@School/Standrew/mech_bernoulli.htm
The San Francisco Exploratorium has some interesting experiments on the Bernoulli
Effect and also some interesting images (for example, the one below where the beach
ball is being held at an angle in the airstream):
http://www.exploratorium.edu/books/bernoulli/
The following resources are also useful for investigations in this area.
Aviation and Space Science Projects, Dr Ben Millspaugh, TAB Books, 1992 contains a
number of experimental investigations in aerodynamics including the Bernoulli
Effect.
NASA has a free airfoil simulator program: FoilSim II (80KB) which can be
downloaded from:
http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html
With this free software from NASA you can investigate how an aircraft wing
produces lift by changing the values of different factors that affect lift.
FoilSim II computes the theoretical lift of a variety of airfoil shapes. The user can
control the shape, size, and inclination of the airfoil and the atmospheric conditions
in which the airfoil is flying. The program includes a stall model for the airfoil, a
model of the Martian atmosphere, and the ability to specify a variety of fluids for lift
comparisons. The program has graphical and numerical output, including an
interactive probe which you can use to investigate the details of flow around an
airfoil.
EXPLAINING DRAG; SKIN FRICTION DRAG, PRESSURE DRAG AND
PRINCIPLES OF THRUST
Although the concepts of drag, skin friction drag, pressure drag and principles of
thrust and how these relate to flight are covered in Aeroplane General Knowledge and
Aerodynamics (pp.25-29, 33-34 and 39), the explanations and diagrams provided by
this text might be too complex for some Unit 2 Physics students.
LIST OF USEFUL ELECTRONIC RESOURCES/WEBSITES
At the ‘howstuffworks’ website there are also good explanations and useful
diagrams covering these concepts:
http://travel.howstuffworks.com/airplane1.htm
The Physics of Flight website run by the United States Air Force also contains useful
information and diagrams covering these concept areas:
http://www.usafa.af.mil/dfp/cockpit-phys/cp_pf0.htm
The Dryden Flight Research Centre – Education website has a very useful Adobe
PDF file titled “Flight Testing Newton’s Laws” (which can be downloaded for free)
which also covers these concepts.
http://www.dfrc.nasa.gov/Education/OnlineEd/NewtonsLaws/index.html
NASA
History of Flight
http://www.ueet.nasa.gov/StudentSite/historyofflight.html
NASA
High speed research aircraft
www.edwards.af.mil/.../splash/ mar98/cover/spaceage.htm
Women in Aviation
Educational, historical, and networking resources to empower women in all aspects
of aviation
http://www.women-in-aviation.com/
Aviation Theory Centre
Has texts such as: Aeroplane General Knowledge and Aerodynamics
http://www.aviationtheory.net.au/
Aerodynamics and Aircraft Design
http://www.flyg.kth.se/education/msc/courses/4E1212/downloads/aerolinks.ht
m
Aerodynamics of Flight
Langley research centre
http://history.nasa.gov/SP-367/cover367.htm
NASA
Aerospace Activities and Lessons
http://www.grc.nasa.gov/WWW/K-12/aeroact.htm
Walter Fendt
A Java applet on Levers which looks at Turning Moments and Torque
http://www.walter-fendt.de/ph14e/lever.htm
http://www.walter-fendt.de/ph11e/lever.htm
NASA
Beginner's Guide to Aerodynamics
http://www.grc.nasa.gov/WWW/K-12/airplane/bga.html
Howstuffworks
Forces acting on airplanes
http://travel.howstuffworks.com/airplane1.htm
Howstuffworks
Explanations of lift
http://travel.howstuffworks.com/airplane2.htm
Physics of Flight
United States Air Force
http://www.usafa.af.mil/dfp/cockpit-phys/cp_pf0.htm
Dryden Flight Research Centre – Education
“Flight Testing Newton’s Laws”
http://www.dfrc.nasa.gov/Education/OnlineEd/NewtonsLaws/index.html
Double Helix Club
Plane designs
http://www.publish.csiro.au/helix/cf/issues/th64b4.cfm
Bernoulli Effect
Interesting experiments re the Bernoulli Effect
http://onezine.s-one.net.sg/@School/Standrew/mech_bernoulli.htm
http://www.exploratorium.edu/books/bernoulli/
NASA
Airplane simulator
http://www.grc.nasa.gov/WWW/K-12/Enginesim/index.htm
Microsoft’s Flight Simulator 2002
Commercial flight simulator
http://www.microsoft.com/games/fs2002/
FlightGear
Non-Commercial flight simulator
http://www.flightgear.org/Docs/InstallGuide/getstartch1.html
National Aerospace Training
Trial Introductory Flights
www.nationalaerospace.net
Forces in Flight Flash Animation
www.aviationnow.com/content/ncof/ncflearn.htm
NASA sites:
http://education.nasa.gov
http://www.dfrc.nasa.gov/
NASA Dryden Flight Centre PDF document ‘Flight Testing Newton’s Laws’ available free online
(an SI Units version is available from RMIT) at
http://www.dfrc.nasa.gov/Education/OnlineEd/NewtonsLaws/index.html
http://www.dfrc.nasa.gov/gallery