Transcript Scenario #1 - Navy STEM for the Classroom

OCEAN LANDING
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BACKGROUND & LESSON OBJECTIVES
Four forces of flight and the factors that
affect each of these forces
Takeoff conditions of a jet from an aircraft
carrier, calculating airspeed
Average force of a catapult system,
applying the impulse-momentum theorem
Paper airplane landing within a designated
target zone
Video analysis of two-dimensional motion
Results summary in a Flight
Analysis Report
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BERNOULLI’S PRINCIPLE: Air Pressure & Flight
What happens to the cans when the student
blows through the straw?
Why do the cans move closer together?
Reason: change in fluid (air) pressure. Air
speeds up to pass between the cans,
causing a drop in pressure. Pressure
outside the cans remains higher.
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FORCES OF FLIGHT: Internet Research
Lift
Thrust
Drag
Weight
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FREE BODY DIAGRAM
Which force pairs have equal magnitude and
opposite direction assuming the jet flight is in
equilibrium (level with constant velocity)?
Lift
Thrust Force = Drag Force
Force Due to Lift = Force Due to Weight
Thrust
Drag
Explain how the free body diagram would
change, if the plane flies straight up.
If the jet flies straight up at a constant speed,
thrust is no longer equal to the drag. Thrust
would equal the combination of weight and drag.
Weight
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FORCES OF FLIGHT: Graphic Organizer
Name of Force
Direction of Force Vector
Factors Affecting This Type of Force
Thrust
Direction of Motion
(In this case, left.)
Thrust is primarily controlled and adjusted by the pilot. But
any factor that changes the density of air will affect thrust,
such as temperature and pressure change at various
altitudes and climates.
Drag
Opposite Direction
of Motion
(In this case, right.)
Drag is affected by the size and shape of the object, the
motion of the object through the air and properties of the
air.
Lift
Upward
The shape and size of a wing and the speed of air
moving over it will affect the lift force.
Straight Down
Weight is a force caused by Earth’s gravitational attraction. As
the jet burns up its fuel during flight, mass (and therefore weight)
decreases. This disrupts the jet’s equilibrium state and therefore
the pilot has to make adjustments to bring it back to a balanced
state.
Weight
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FLIGHT SCENARIOS: Assumptions & Calculations
Complete Calculations to make a
“Go” or “No Go” Determination
If “No Go”, describe adjustments needed to ensure minimum
airspeed is reached for takeoff
Airspeed = VS + VC + VHW
Vship = ship speed
VC = catapult speed
VHW = headwind speed
Note: assume positive wind
velocity is in the direction opposite
the ship’s motion
(tailwind = negative wind)
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FLIGHT SCENARIOS: “Go” or “No Go”?
Equation / Calculations
Scenario #1:
Airspeed = 20 + 150 + 30 = 200 mph
Scenario #2:
Airspeed = 20 + 150 + (-10) = 160 mph
Decision (“Go” or “No
Go”?) with Justification
Go
No Go
Adjustments (If Necessary)
N/A
-
Scenario #3:
Airspeed = 20 + 150 + 10 = 185 mph
Scenario #4:
Airspeed = 20 + 150 + (-15) = 135 mph
Increase the ship speed
Increase jet engine throttle to maximize
forward thrust
Turn ship into the wind to maximize lift
Go
N/A
No Go
-
Set ship in motion with speed ≧35 mph
Turn ship into the wind to maximize lift
Increase jet engine throttle to maximize
forward thrust
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EXTEND YOUR THINKING: Calculations
Should the Navy invest in a new catapult system?
Solution:
Favg. = [(mvf – mvi) / t] - Fthrust
For this situation, Newton’s Second Law:
Fnet = ma can be rewritten in terms of momentum as:
Fthrust = 140,000 N
m = 20,000 kg
Fnet = (Favg.)catapult + Fthrust = p / t
vi = 0 m/s (rest condition)
vf = 76 m/s
(Favg.)catapult = [p / t] - Fthrust
Note: p = final momentum (mvf) - initial momentum (mvi)
ti = 0 s
tf = 2 s
t = 2 seconds
t = final time (tf) – initial time (ti)
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EXTEND YOUR THINKING: Conclusions
Plugging into the equation and solving for average
force gives:
Average Force = (20,000 kg) (76 m/s) / 2 s =
760,000 kg*m/s2 - 140,000 kg*m/s2 = 620,000
kg*m/s2 which is equivalent to 620,000 N.
This force is significantly less than that generated
by the electromagnetic system (810,000 N).
Therefore, the improved average force
and other advantages associated with the
Electromagnetic Aircraft Launch system (EMALS)
technology make this a smart decision.
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WHAT DOES A SAFE LANDING LOOK LIKE?
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KEY CONSIDERATIONS: Successful Landing
During an “arrested” landing the jet is
decelerated on the runway using a tailhook.
The wires are attached to a hydraulic system
that absorbs the energy of impact and
brings the plane to a halt. The pilot aims for
the third wire which is the safest and most
effective target.
All crew members on board the carrier work
together. The Landing Signal Officers (LSOs)
assist in guiding the plane in through radio
communication and lights.
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RESEARCH YOUR PLANE DESIGN
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BUILD & TEST YOUR PLANE DESIGN
Review Airplane Landing Challenge:
• Build Your Design
• Complete Trials 1 & 2 (landing in a
designated target zone)
• Conduct Video/Graphical Analysis
• Make Design Modifications and
Complete Trial 3
• Create Flight Analysis Report
(as a group)
Review Grading Rubric
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FLIGHT ANALYSIS REPORTS
Conduct and Video Trials
#1 & #2
Background – How research informed
initial plane design. Include steps used to
design and build the paper airplane. Use
terms such as weight, lift, thrust, drag, and
a describe how Newton’s Laws apply.
Results of Flight Trials –
Include data table
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VIDEO/GRAPHICAL ANALYSIS
Focus on the plane’s:
• apex,
• time of flight,
• angle of approach, and
• linear displacement on the
runway to determine
possible modifications that
should be made before
completing the
third and final flight trial.
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DESIGN MODIFICATIONS?
What modifications (if any) does your
group need to make to your airplane
design? Be sure to use the results and
video analysis of your first two trials to
justify any modifications.
Conduct and record the results of your
third and final trial in your data table.
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COMPLETE FLIGHT ANALYSIS REPORTS
Was the goal met during the first
two trials?
If not, what modifications or
changes in design were made for
the final trial? How did the video
analysis inform your decisions?
Which conditions yielded optimal
results for landing on the runway?
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LESSON SUMMARY
Various factors affect the four forces of flight (lift, drag, thrust, weight) and
lift is created by a difference in pressure between the area above the wing
and the area below the wing.
Airspeed calculations are used to predict safe conditions for launching an
aircraft from an aircraft carrier.
Takeoff and landing of an aircraft on an aircraft carrier involves the
coordinated effort of engineers, pilots, flight deck operators and landing
signal officers.
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