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Propulsion System Analysis
Activity
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If so instructed by your teacher, print out a worksheet
page for these problems.
- Why do different aircraft have different types of
propulsion systems?
- When would you use a ramjet
on an airplane?
- Find the Mach number
for a subsonic airplane flying at 650 mph.
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M = Mach
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M =V/A
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V = Air Velocity
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M = ________________
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A = 762 mph. (speed of sound)
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- Find the Mach number for a subsonic airplane flying at 525 mph.
M = ____________
- Find the Mach number for a suubsonic airplane flying at 725
mph.
M = ____________
- Find the velocity of a subsonic airplane flying at Mach number
of .65.
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M = Mach
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M = V/A
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V = Air Velocity
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V = ________________
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A = 762 mph. (speed of sound)
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- Find the velocity of a subsonic airplane flying at Mach
number of .80.
V = ____________
- Find the velocity of a supersonic airplane flying at Mach number
of 1.5.
V = ____________
- Using the interactive
Atmosphere Calculator,
find the speed of sound, pressure and temperature at the following
altitudes using English Units.
ALTITUDE
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SOUND SPEED
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PRESSURE
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TEMPERATURE
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1,000 ft.
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5,000 ft.
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10,000 ft.
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20,000 ft.
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25,000 ft.
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30,000 ft.
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- Produce three graphs from the data recorded above, showing
speed of sound, pressure, and temperature versus altitude.
- What effect does altitude have on the speed of sound?
- What effect does altitude have on pressure?
- What effect does altitude have on temperature?
- Flying at a constant speed of 600 feet per second, find the speed of
sound and the Mach number at the following altitudes.
ALTITUDE
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SOUND SPEED
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MACH NUMBER
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1,000 ft.
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10,000 ft.
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20,000 ft.
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30,000 ft.
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- Graph the changes in Mach Number
at the different altitudes.
- How does the change in altitude affect Mach Number when
flying at a constant speed?
- The thrust of a jet engine is also affected by changes in altitude.
Calculate the thrust of a Pratt & Whitney JT8D-17 jet engine (17,000 pounds at sea level)
at different altitudes using the temperature and pressure results
from Question 9, and the following equation:
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F = thrust at altitude
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F sl = sea level static thrust at
takeoff (17,000 pounds)
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P = static pressure at
altitude
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P sl = sea level static pressure (14.7
psi)
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F
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=
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F sl
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x
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P/P sl
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x
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sqrt(T sl/T)
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T = absolute temp (temp + 460) at altitude
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T sl = sea level absolute temperature
(520 R)
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ALTITUDE
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PRESSURE
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TEMPERATURE
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#
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THRUST
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1000 ft.
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A.
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10,000 ft.
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B.
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20,000 ft.
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C.
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30,000 ft.
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D.
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- Graph the change in thrust with altitude for the Pratt &
Whitney JT8D-17 jet engine.
- Give your conclusions on thrust and flying at different
altitudes.
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