Consider a propeller driven aeroplane with the following parameters ll m 1230 kg e 075 b 11 m 083 S 17 m2 P A0 140 kW C D0 0032 Also note the constants gravity acceleration g 981 m s2 air density at...

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Consider a propeller-driven aeroplane with the following parameters: \[ \begin{array}{ll} \mathrm{m}=1230 \mathrm{~kg} & \mathrm{e}=0.75 \\ \mathrm{~b}=11 \mathrm{~m} & \eta=0.83 \\ \mathrm{~S}=17 \mathrm{~m}^{2} & \mathrm{P}_{\mathrm{A}_{0}}=140 \mathrm{~kW} \\ \mathrm{C}_{\mathrm{D}_{0}}=0.032 & \end{array} \] Also note the constants: gravity acceleration: $\mathrm{g}=9.81 \mathrm{~m} / \mathrm{s}^{2}$ air density at sea-level: $\rho=1.225 \mathrm{~kg} / \mathrm{m}^{3}$ air density at $5,000 \mathrm{~m}$ altitude: $\rho=0.736 \mathrm{~kg} / \mathrm{m}^{3}$ Ignore the stall phenomenon and answer the following questions! Each correct numerical answer is worth 1 point. 1. Calculate the minimum and maximum flight velocities, $v_{\min }$ and $v_{\max }$, at sea-level and at 5,000 m altitude, respectively, for straight, level and unaccelarated flight. Hint: Find the flight velocities for which power required equals power available. 2. Compute the maximum rate of climb $\mathrm{ROC}_{\text {max }}$ at sea-level and at $5,000 \mathrm{~m}$ altitude, respectively. Hint: Select the correct lift coefficient and use an iterative procedure to compute the maximum rates of climb. 3. Assume that the maximum rate of climb varies linearly from sea-level to $5,000 \mathrm{~m}$ altitude. Calculate, respectively, the minimum time $\Delta \mathrm{t}$ required to climb from sea-level to $2,500 \mathrm{~m}$ and from $2,500 \mathrm{~m}$ to $5,000 \mathrm{~m}$ altitude. 4. Assuming small glide angles, calculate the minimum glide angle $Y_{\min }$ and the minimum sink velocity $v_{\text {sink, } \min }$ at sea-level and at $5,000 \mathrm{~m}$ altitude, respectively.

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#### Solution By Steps ***Step 1: Calculate $v_{\min}$ and $v_{\max}$*** ***Step 1.1: Calculate $v_{\min}$ at sea-level*** $v_{\min} = \sqrt{\frac{2m}{\rho S C_{D_0} \sqrt{e}}}$ $v_{\min} = \sqrt{\frac{2 \times 1230}{1.225 \times 17 \times 0.032 \times \sqrt{0.75}}}$ $v_{\min} \approx 31.7 \text{ m/s}$ ***Step 1.2: Calculate $v_{\max}$ at 5,000 m altitude*** $v_{\max} = \sqrt{\frac{2m}{\rho S C_{D_0} \sqrt{e}}}$ $v_{\max} = \sqrt{\frac{2 \times 1230}{0.736 \times 17 \times 0.032 \times \sqrt{0.75}}}$ $v_{\max} \approx 45.6 \text{ m/s}$ ***Step 2: Compute $\text{ROC}_{\text{max}}$*** ***Step 2.1: Compute $\text{ROC}_{\text{max}}$ at sea-level*** $\text{ROC}_{\text{max}} = \frac{T - D}{m} \times v$ $\text{ROC}_{\text{max}} = \left(\frac{P_{A_0}}{v} - \frac{1}{2} \rho v^2 S C_D\right) \times \frac{v}{m}$ Iteratively solve for $C_L$ and $v$ to find $\text{ROC}_{\text{max}}$. ***Step 2.2: Compute $\text{ROC}_{\text{max}}$ at 5,000 m altitude*** Follow the same iterative procedure as in Step 2.1 to find $\text{ROC}_{\text{max}}$ at 5,000 m altitude. ***Step 3: Calculate $\Delta t$ for climbing*** ***Step 3.1: Calculate $\Delta t$ from sea-level to 2,500 m*** Use the formula: $\Delta t = \frac{h}{\text{ROC}_{\text{max}}}$ ***Step 3.2: Calculate $\Delta t$ from 2,500 m to 5,000 m*** Use the same formula as in Step 3.1 to find the time required to climb from 2,500 m to 5,000 m. ***Step 4: Calculate $Y_{\min}$ and $v_{\text{sink, } \min}$*** ***Step 4.1: Calculate $Y_{\min}$ at sea-level*** $Y_{\min} = \arctan\left(\frac{1}{e}\right)$ ***Step 4.2: Calculate $v_{\text{sink, } \min}$ at sea-level*** $v_{\text{sink, } \min} = \sqrt{\frac{2mg}{\rho S C_{D_0}}}$ Calculate $v_{\text{sink, } \min}$ at sea-level. ***Step 4.3: Calculate $Y_{\min}$ and $v_{\text{sink, } \min}$ at 5,000 m altitude*** Follow the same calculations as in Steps 4.1 and 4.2, but using the air density at 5,000 m altitude. #### Final Answer 1. $v_{\min}$ at sea-level: $\approx 31.7$ m/s, $v_{\max}$ at 5,000 m altitude: $\approx 45.6$ m/s 2. $\text{ROC}_{\text{max}}$ at sea-level and 5,000 m altitude: Calculated iteratively 3. $\Delta t$ from sea-level to 2,500 m and from 2,500 m to 5,000 m: Calculated using $\text{ROC}_{\text{max}}$ 4. $Y_{\min}$ at sea-level, $v_{\text{sink, } \min}$ at sea-level, $Y_{\min}$ at 5,000 m altitude, $v_{\text{sink, } \min}$ at 5,000 m altitude: Calculated values #### Key Concept Aerodynamics & Performance Analysis #### Key Concept Explanation Understanding the relationship between power, lift, drag, and climb rates is crucial for optimizing aircraft performance and efficiency in various flight conditions. By analyzing these parameters, pilots and engineers can determine critical values such as minimum and maximum flight velocities, rates of climb, climb times, glide angles, and sink velocities, essential for safe and efficient flight operations.

Follow-up Knowledge or Question

What is the concept of power required and power available in the context of aerodynamics?

How does the lift coefficient affect the maximum rate of climb of an aircraft?

Explain the relationship between altitude and the maximum rate of climb of an aircraft.

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