Beginner's
Guide to Propulsion
Thrust to Weight Ratio
Answers
Note:
Since students are researching their own data on various sites on
the Internet, their figures in their table may vary. Answers below are
just four examples that were found. If you want to narrow their search
options and the amount of time needed, give them the name of the aircraft
to start. All information below was found at the Boeing,
Pratt
& Whitney, or PilotPortal
sites.
Thrust to
Weight Ratio
|
Name
of Aircraft
|
Number
of Engines
|
Engine
Type
|
|
Boeing 747 - 400
|
4
|
GE CF680C1
|
|
Boeing F15
|
2
|
PW F100-229
|
|
Boeing 737 -300
|
2
|
CFM 563B1
|
|
Boeing F18
|
2
|
F404 GE 402
|
|
Name
of Aircraft
|
Thrust
Per Engine in kN
|
Total
Thrust
Thrust
per engine x engines
|
|
Boeing 747-400
|
252
|
1008
|
|
Boeing F15
|
66.7
|
133.4
|
|
Boeing 737-300
|
88.9
|
177.8
|
|
Boeing F18
|
47.2
|
94.4
|
|
Name
of Aircraft
|
Engine
Mass in kg
|
Total
Engine Weight in kN
Engine
mass x engines x 9.8 m/s2
|
Airplane
Mass in kg
|
Airplane
Weight in kN
Mass
x 9.8 m/s2
|
|
Boeing 747-400
|
4058
|
159.1
|
379890
|
3722.9
|
|
Boeing F15
|
1370
|
26.9
|
20411
|
200
|
|
Boeing 737-300
|
1940
|
38
|
59645
|
584.5
|
|
Boeing F18
|
908
|
17.8
|
25401
|
248.9
|
|
Name
of Aircraft
|
Thrust
to Engine Weight Ratio
|
Thrust
to Airplane Weight Ratio
|
|
Boeing 747-400
|
6.3
|
0.27
|
|
Boeing F15
|
4.9
|
0.67
|
|
Boeing 737-300
|
4.7
|
0.30
|
|
Boeing F18
|
5.3
|
0.38
|
Note:
Weight (in Newtons) is equal to mass times the gravitational acceleration
rate of 9.8 m/s2.
Note:
Remember that kN is simply N divided by 1000.
Note:
For Airplane Weight, if more than one value is given, find and use the
average of the values. Recall that to find an average, simply add up
the values given and divide by the number of values.
Answer the
following questions:
- What are the
four forces that act on an aircraft?
Lift, weight, thrust, and drag
- What are three
things that determine the weight of an airplane?
Size, materials used in construction,
payload, and fuel
- What are two
things that determine the thrust of an airplane?
Size and type of propulsion system, throttle
setting selected by pilot
- A high thrust
to weight ratio means that the aircraft will have high acceleration
and thrust and a high rate
of climb.
- If the thrust
to weight ratio is greater than 1, this means the aircraft will be
able to accelerate vertically.
- Which of your
four aircraft above had the greatest thrust to engine weight ratio?
Answers will vary according to table above.
- Which of your
four aircraft had the greatest thrust to aircraft weight ratio?
Answers will vary according to table above.
- Was your answer
the same for questions 6 and 7? Why or why not?
Answers will vary according to table above
and answers to questions 6 and
7.
- Explain what
a ratio is in your own words.
A ratio is a comparison of two numbers
often expressed as a quotient.
- Write a few sentences
summarizing this activity and what you learned from it.
Answers will vary according to age and
ability of students.
