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## Homework Statement

The Predator UAV has the following characteristics: wingspan = 14.85 m,

wing area = 11.45 m2

, maximum mass = 1020 kg, and fuel mass = 295 kg. Note the

weights are given in kg. You should covert them to weight force W in N. The power

plant is a Rotax four-cylinder, four-stroke engine of 85 horsepower driving a two-blade,

variable pitch pusher propeller. Assume the Oswald efficiency is 0.7, the zero-lift drag

coefficient is 0.03, the propeller efficiency is 0.9, and the specific fuel consumption is 0.2

kg(note this mass, not weight) of fuel per horsepower hour

## Homework Equations

1.calculate the maximum range.

Hint) Please make sure you use the correct weight of the fuel (Wf=m*g= W0- W1

Also, please compute the correct value of c (SFC) in the SI unit, N/(second*Nm/s).

You have to convert 0.2kg/(hour*hp).

2. calculate the maximum endurance at sea level and

## The Attempt at a Solution

1.I think when TR(thrust required) is at min, R(range) is at max, and when CD,0(zero-lift-drag)=CD,i(induced drag), TR is at min.

By doing in this way, I get 7.91*10^6meters, which is much larger than what wikipedia says about the Predator's range.

2.I think when PR(Power required) is at min, E(endurance) is at max, and when CD,0(zero-lift-drag)=1/3*CD,i(induced drag), PR is at min.

By doing in this way, I get 2.674*10^5s, which is much larger than what wikipedia says about the Predator's endurance.

Am I using a wrong method or making a mistake in calculation?