/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 86 A small aircraft has a total win... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

A small aircraft has a total wing area of \(30 \mathrm{~m}^{2},\) a lift coefficient of 0.45 at takeoff settings, and a total mass of \(2800 \mathrm{~kg}\). (a) Determine the takeoff speed in \(\mathrm{km} / \mathrm{h}\) of the aircraft at sea level under standard atmospheric conditions. (b) Determine the wing loading. (c) Determine the required power to maintain a constant cruising speed of \(300 \mathrm{~km} / \mathrm{h}\) for a cruising drag coefficient of \(0.035 .\) Assume standard air.

Short Answer

Expert verified
(a) 221.52 km/h; (b) 916.67 N/m²; (c) 443.28 kW.

Step by step solution

01

Understand the Problem

Before solving, identify the known values from the problem: wing area \(A = 30 \, \text{m}^2\), lift coefficient \(C_L = 0.45\), mass of the aircraft \(m = 2800 \, \text{kg}\), cruising speed \(300 \, \text{km/h}\), and cruising drag coefficient \(C_D = 0.035\). You are asked to find (a) the takeoff speed \(V\) in \(\text{km/h}\), (b) the wing loading, and (c) the required power at cruising speed.
02

Calculate Takeoff Speed

Lift force at takeoff must equal weight: \(L = W\). The lift force \(L = \frac{1}{2} \rho V^2 A C_L\), and weight \(W = mg\). At sea level, \(\rho \approx 1.225 \, \text{kg/m}^3\). Set \(\frac{1}{2} \rho V^2 A C_L = mg\) and solve for \(V\):\[V = \sqrt{\frac{2mg}{\rho A C_L}}\]Substituting the values: \[ \rho = 1.225 \, \text{kg/m}^3, \quad g = 9.81 \, \text{m/s}^2 \]\[ V = \sqrt{\frac{2 \times 2800 \times 9.81}{1.225 \times 30 \times 0.45}} \Approx 61.53 \, \text{m/s} \]Convert \(V\) from \(\text{m/s}\) to \(\text{km/h}\): \(V \times 3.6 \approx 221.52 \, \text{km/h}\).
03

Compute Wing Loading

Wing loading is the weight of the aircraft divided by its wing area: \[\text{Wing loading} = \frac{W}{A} = \frac{2800 \cdot 9.81}{30} \approx 916.67 \, \text{N/m}^2\]
04

Determine Required Power for Cruising Speed

Power required is the drag force times the speed, \(P = D \cdot V\), where Drag force \(D = \frac{1}{2} \rho V^2 A C_D\). Substitute the cruising speed in \(\text{m/s}\) (\(300 \, \text{km/h} \equiv 83.33 \, \text{m/s}\)) and solve for power:\[D = \frac{1}{2} \cdot 1.225 \cdot (83.33)^2 \cdot 30 \cdot 0.035 \approx 5319.94 \, \text{N}\]\[P = D \cdot V = 5319.94 \times 83.33 \approx 443,282 \, \text{W} = 443.28 \, \text{kW}\]
05

Conclusion: Presenting the Results

(a) The takeoff speed is approximately \(221.52 \, \text{km/h}\). (b) The wing loading is \(916.67 \, \text{N/m}^2\). (c) The required power at cruising speed is about \(443.28 \, \text{kW}\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Takeoff Speed Calculation
Takeoff speed is a critical parameter for an aircraft. It is the minimum speed needed for the airplane to become airborne. Calculating this speed ensures that the aircraft can safely lift off the runway. To determine the takeoff speed, we need to look at the balance of lift force and weight.The lift force must equal the weight of the aircraft at takeoff. This is expressed as:\[ L = \frac{1}{2} \rho V^2 A C_L \]Where:- \(L\) is the lift force,- \(\rho\) is the air density at sea level, approximately \(1.225 \, \text{kg/m}^3\),- \(V\) is the velocity or speed,- \(A\) is the wing area, and- \(C_L\) is the lift coefficient.To find the takeoff speed \(V\), we set the lift equal to the weight \(W = mg\), and rearrange the equation to solve for \(V\):\[ V = \sqrt{\frac{2mg}{\rho A C_L}} \]Once calculated, convert \(V\) from meters per second (m/s) to kilometers per hour (km/h) by multiplying by 3.6. This provides us with an accurate takeoff speed under standard conditions.
Wing Loading
Wing loading is an efficient way to describe the stress placed on an aircraft's wings during flight by the weight of the aircraft. Essentially, it is the weight per unit area of the wing.This concept is vital because it influences the takeoff speed, maneuverability, and stability of the aircraft. Lower wing loading generally means a lighter aircraft or larger wings—which results in better maneuverability and shorter takeoff distances. Conversely, high wing loading might indicate a heavier aircraft, possibly requiring more runway to achieve takeoff.To calculate wing loading, we use the formula:\[ \text{Wing loading} = \frac{W}{A} \]Where:- \(W\) is the total weight,- \(A\) is the wing area.This calculation shows us how much weight the wings must support per square meter, helping in evaluating aircraft performance at different speeds and altitudes.
Cruising Power Requirements
Understanding the cruising power requirements of an aircraft helps in planning fuel consumption and ensuring efficiency during flights. Cruising speed is the speed at which the aircraft travels with the best fuel efficiency while maintaining a balance between speed and fuel consumption.The required power to maintain this speed can be calculated using the drag force multiplied by velocity:\[ P = D \cdot V \]Where:- \(P\) is the power required,- \(D\) is the drag force, and- \(V\) is the velocity or cruising speed of the aircraft.Now, drag force can be calculated by the following equation:\[ D = \frac{1}{2} \rho V^2 A C_D \]Where:- \(\rho\) is the air density,- \(C_D\) is the drag coefficient.By calculating the drag at cruising speed and using it to find the power, one can predict the fuel efficiency and effectively manage flight operations. The balance between lift, drag, and thrust plays a crucial role in maintaining desired cruising speeds and optimizing performance.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Show that the terminal velocity of a rising spherical body in a surrounding fluid of different density can be expressed in nondimensional terms using the so-called densimetric Froude number, \(\mathrm{Fr}_{\mathrm{d}},\) as $$ \mathrm{Fr}_{\mathrm{d}}^{2}=\frac{4}{3 C_{\mathrm{D}}} $$ where \(C_{\mathrm{D}}\) is the drag coefficient and the densimetric Froude number, \(\mathrm{Fr}_{\mathrm{d}},\) is defined by the relation $$ \mathrm{Fr}_{\mathrm{d}}=\frac{V}{\sqrt{\frac{\Delta \rho}{\rho} g D}} $$ where \(V\) is the terminal velocity, \(\Delta \rho\) is the difference in density between the surrounding fluid and the sphere, \(\rho\) is the density of the surrounding fluid, \(g\) is gravity, and \(D\) is the diameter of the sphere. Comment on whether Equation 10.57 is also applicable to a falling spherical body. Note that \(\Delta \rho / \rho \cdot g\) is the effective gravity on a submerged body, commonly represented by \(g^{\prime}\).

A baseball with a mass of \(145 \mathrm{~g}\) and a diameter of \(71.6 \mathrm{~mm}\) is dropped from a height of \(1 \mathrm{~km}\) in a standard atmosphere. (a) Estimate the terminal velocity attained by the baseball, assuming that atmospheric conditions remain constant and equal to those at the release height. (b) Determine the time it takes the baseball to attain \(90 \%\) of its terminal velocity. (c) Determine the distance traveled for the baseball to attain \(90 \%\) of its terminal velocity. Based on your results, comment on whether the assumption of constant atmospheric conditions is reasonable.

Firing tests on a \(10-\mathrm{mm}\) -diameter bullet with a mass of \(20 \mathrm{~g}\) show that in standard air, the bullet speed decreases from \(300 \mathrm{~m} / \mathrm{s}\) to \(180 \mathrm{~m} / \mathrm{s}\) over a distance of \(200 \mathrm{~m}\). Estimate the average drag coefficient of the bullet. Neglect compressibility effects.

A model aircraft has a total wing area of \(6 \mathrm{~m}^{2}\). Based on experimental results from similar aircraft, it is estimated that the lift and drag coefficients are around 0.71 and 0.17 , respectively. It is intended that the model airplane fly at a speed of \(15 \mathrm{~m} / \mathrm{s}\) under standard sea-level conditions. (a) What is the maximum allowable weight of the airplane? (b) What is the power required to fly the airplane at its design speed?

A relatively small cruise ship has a length of \(100 \mathrm{~m}\), a draft of \(5 \mathrm{~m}\), and an estimated roughness height of \(0.1 \mathrm{~mm}\). The ship is designed for a cruising speed of \(10.30 \mathrm{~m} / \mathrm{s}\). (a) Under design conditions, determine whether the submerged surface of the ship is (hydrodynamically) smooth, rough, or transitional. (b) Estimate the frictional drag force on the ship under design conditions. (c) If the submerged surface was to vary between the smooth and rough surface regime, what would be the corresponding range of the drag force? Assume seawater at \(20^{\circ} \mathrm{C}\).

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.