
Propulsion System Analysis
Activity


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.

M = Mach

M =V/A

V = Air Velocity

M = ________________

A = 762 mph. (speed of sound)

 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.

M = Mach

M = V/A

V = Air Velocity

V = ________________

A = 762 mph. (speed of sound)

 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

SOUND SPEED

PRESSURE

TEMPERATURE

1,000 ft.




5,000 ft.




10,000 ft.




20,000 ft.




25,000 ft.




30,000 ft.




 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

SOUND SPEED

MACH NUMBER

1,000 ft.



10,000 ft.



20,000 ft.



30,000 ft.



 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 JT8D17 jet engine (17,000 pounds at sea level)
at different altitudes using the temperature and pressure results
from Question 9, and the following equation:








F = thrust at altitude









F sl = sea level static thrust at
takeoff (17,000 pounds)









P = static pressure at
altitude









P sl = sea level static pressure (14.7
psi)

F

=

F sl

x

P/P sl

x

sqrt(T sl/T)


T = absolute temp (temp + 460) at altitude









T sl = sea level absolute temperature
(520 R)

ALTITUDE

PRESSURE

TEMPERATURE

#

THRUST

1000 ft.



A.


10,000 ft.



B.


20,000 ft.



C.


30,000 ft.



D.


 Graph the change in thrust with altitude for the Pratt &
Whitney JT8D17 jet engine.
 Give your conclusions on thrust and flying at different
altitudes.
