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HW 7

1. Performance calculations are done for a C172D and CJ-1 aircraft at sea level. Lift coefficient, drag coefficient, L/D ratio, and thrust required are computed. 2. Similar performance calculations are done for the CJ-1 aircraft at 341 mph true airspeed at sea level. 3. Calculations are shown to convert the CJ-1's airspeed at sea level to an equivalent airspeed at 22,000 feet. Performance parameters are then computed for this condition. It is observed that maximum velocity and rate of climb are higher at sea level compared to 22,000 feet, due to lower density at higher altitude.

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149 views3 pages

HW 7

1. Performance calculations are done for a C172D and CJ-1 aircraft at sea level. Lift coefficient, drag coefficient, L/D ratio, and thrust required are computed. 2. Similar performance calculations are done for the CJ-1 aircraft at 341 mph true airspeed at sea level. 3. Calculations are shown to convert the CJ-1's airspeed at sea level to an equivalent airspeed at 22,000 feet. Performance parameters are then computed for this condition. It is observed that maximum velocity and rate of climb are higher at sea level compared to 22,000 feet, due to lower density at higher altitude.

Uploaded by

Raul
Copyright
© © All Rights Reserved
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HW 7

1. For the C172D flying at sea level (density = 0.002377 slug/ft33) with V∞V∞ =
95 knots (160ft/s), compute:
A. Lift coefficient
𝑊 2300
𝐶𝐿 = 1 2𝑆
=𝐶𝐿 = 1 =0.434
𝜌∞ 𝑉∞ (0.002377)(1602)(174)
2 2

B. Drag coefficient

𝐶𝐿2 (0.434)2
𝐶𝐷 = 𝐶𝐷,0 + = 0.025 + = 0.0351
𝜋𝑒𝐴𝑅 𝜋(0.8)(7.37)

C. (L/D) ratio

𝐿 𝐶𝐿 0.434
= = = 12.4
𝐷 𝐶𝐷 0.0351

D. Find Thrust Required, TR

𝑊 2300
𝑇𝑅 = = = 185.5𝑙𝑏
𝐿⁄ 12.4
𝐷
HW 7

2. For the CJ-1 flying at sea level (density = 0.002377 slug/ft33) with V∞V∞ = 341
mi/h (500ft/s), compute:

A. Lift coefficient
𝑊 19815
𝐶𝐿 = 1 2𝑆
=𝐶𝐿 = 1 =0.209
𝜌∞ 𝑉∞ (0.002377)(5002)(318)
2 2

B. Drag coefficient

𝐶𝐿2 (0.209)2
𝐶𝐷 = 𝐶𝐷,0 + = 0.025 + = 0.027
𝜋𝑒𝐴𝑅 𝜋(0.81)(8.93)

C. (L/D) ratio

𝐿 𝐶𝐿 0.209
= = = 7.7
𝐷 𝐶𝐷 0.027
D. Find Thrust Required, TR

𝑊 19815
𝑇𝑅 = = = 2600𝑙𝑏
𝐿⁄ 7.7
𝐷
3. For the CJ-1 flying at 22,000 (density = 0.001184 slug/ft33) with V∞ = ???,
compute:
𝜌 1⁄ 0.001184 1⁄
𝑉𝑠𝑒𝑎 𝑙𝑒𝑣𝑒𝑙 = 𝑉22,000 (𝜌 ) 2 => 500 = 𝑉22,000 (0.002377) 2 = 568.3 𝑓𝑡/𝑠
𝑠𝑒𝑎 𝑙𝑒𝑣𝑒𝑙
Type equation here.

A. Find Thrust Required, TR

𝑊 19815
𝑇𝑅 = = = 2600𝑙𝑏
𝐿⁄ 7.7
𝐷
B. Lift coefficient
𝑊 19815
𝐶𝐿 = 1 =𝐶𝐿 = 1 =0.33
𝜌 𝑉2 𝑆 (0.001184)(568.32)(318)
2 ∞ ∞ 2

C. Drag coefficient

𝐶𝐿2 (0.33)2
𝐶𝐷 = 𝐶𝐷,0 + = 0.025 + = 0.025
𝜋𝑒𝐴𝑅 𝜋(0.81)(8.93)

D. (L/D) ratio

𝐿 𝐶𝐿 0.33
= = = 13.2
𝐷 𝐶𝐷 0.025

E. The maximum velocity and maximum R/C for the CJ-1 at sea level and
22,000ft are different at values of 200ft/s and -866.94ft/min respectively
for at sea level and 400ft/s and -1221.77ft/min respectively for at
22,000ft. From what can be observed from the two performance
parameters is that the altitude of 22,000ft is almost double than when it
is at sea level. This is due to the differing densities existing at the
different altitudes.

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