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ENGINEERING, AE 2024 HSC 22b

The mass of a single-engine propeller aeroplane, without pilot or passengers, is 906 kg . It has a maximum lift to drag ratio of 10.5. When fully loaded, the plane needs to produce 1050 N of thrust to maintain cruising speed and altitude.

What is the maximum total allowable mass for the pilot and passengers in kilograms?   (3 marks)

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\(\text{Max allowable mass (pilot and passengers)}\ =196.5\ \text{kg}\)

Show Worked Solution

\(mg\ \text{(empty plane)}\ = 906 \times 10=9060\ \text{N}\)

\(\text{When plane cruising}\ \ \Rightarrow \ \ \text{Thrust = Drag = 1050 N}\)

\(\text{Max Lift to Drag ratio = 10.5}\)

Mean mark 54%.
\(\dfrac{\text{Max Lift}}{\text{Drag}} \) \(=10.5\)  
\(\text{Max Lift}\) \(=1050\ \text{N}\ \times 10.5=11\ 025\ \text{N}\)  

 
\(\text{Max}\ mg\ \text{(pilot and passengers)}\ = 11\ 025-9060=1965\ \text{N}\)

\(\therefore\ \text{Max allowable mass (pilot and passengers)}\ =196.5\ \text{kg}\)

ENGINEERING, AE 2024 HSC 12 MC

What is the effect of increasing the angle of attack on the lift and induced drag of an aircraft?

\begin{align*}
\begin{array}{c}
\rule{0pt}{2.5ex}  \ & \rule[-1ex]{0pt}{0pt} \\
\rule{0pt}{2.5ex}  \textbf{A.} \rule[-1ex]{0pt}{0pt} \\
\rule{0pt}{2.5ex}  \textbf{B.} \rule[-1ex]{0pt}{0pt} \\
\rule{0pt}{2.5ex}  \textbf{C.} \rule[-1ex]{0pt}{0pt} \\
\rule{0pt}{2.5ex}  \textbf{D.} \rule[-1ex]{0pt}{0pt} \\
\end{array}
\begin{array} {|c|c|}
\hline
\rule{0pt}{2.5ex} \text{Lift} \rule[-1ex]{0pt}{0pt} & \text{Induced drag} \\
\hline
\rule{0pt}{2.5ex} \ \ \ \ \ \text{Decreases} \ \ \ \ \ \rule[-1ex]{0pt}{0pt} & \ \ \ \ \ \text{Decreases} \ \ \ \ \ \\
\hline
\rule{0pt}{2.5ex} \text{Decreases} \rule[-1ex]{0pt}{0pt} & \text{Increases} \\
\hline
\rule{0pt}{2.5ex} \text{Increases} \rule[-1ex]{0pt}{0pt} & \text{Decreases} \\
\hline
\rule{0pt}{2.5ex} \text{Increases} \rule[-1ex]{0pt}{0pt} & \text{Increases} \\
\hline
\end{array}
\end{align*}

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\(D\)

Show Worked Solution

As the angle of attack increases:

  • it creates greater lift due to increased airflow deflection under the wing
  • it creates greater induced drag due to stronger wingtip vortices and pressure differential effects.

\(\Rightarrow D\)

ENGINEERING, AE 2023 HSC 16 MC

An aircraft weighing 3 tonne is ascending as shown. The lift to drag ratio is \(11: 1\).
 

Which row of the table correctly identifies the lift, drag and thrust values for the aircraft?

  \( \text{Lift} \) \( \text{Drag}\) \( \text{Thrust}\)
\( \text{A.} \) \(29.8\ \text{kN}\) \(2.7\ \text{kN}\) \(5.8\ \text{kN}\)
\( \text{B.} \) \(29.8\ \text{kN}\) \(2.7\ \text{kN}\) \(3.1\ \text{kN}\)
\( \text{C.} \) \(2.7\ \text{kN}\) \(3.1\ \text{kN}\) \(5.8\ \text{kN}\)
\( \text{D.} \) \(2.7\ \text{kN}\) \(3.1\ \text{kN}\) \(29.8\ \text{kN}\)
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\(  A \)

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\(\Rightarrow  A \)

ENGINEERING, AE 2017 HSC 6 MC

The diagram shows an aerofoil.
 

Which condition needs to be achieved for lift to occur?

  1. Pressure 1<Pressure 2
  2. Pressure 1= Pressure 2
  3. Pressure 1> Pressure 2
  4. Pressure 1+ Pressure 2=0
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`A`

Show Worked Solution
  • For a net upwards force, the force from pressure below (pushing up) must exceed the force from pressure above (pushing down).
  • Therefore Pressure 1<Pressure 2.

`=A>`

ENGINEERING, AE 2016 HSC 25c

A taut cable and aerofoil of similar thickness are tested in a wind tunnel. The results show that the aerofoil produces significantly less drag than the cable.

Explain how the aerofoil produces less drag than the taut cable. Use the diagram to assist your response.   (3 marks)


 

 

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  • Significant surface drag is created by the cable due to its rough surface.
  • Low pressure is created behind the cable due to its non aerodynamic shape, thus pulling the cable backwards and creating sizeable drag.
  • Vortices (turbulence) created behind the cable also produce drag.
  • The smooth surface, and aerodynamic shape of the symmetrical aerofoil, help minimise turbulence at the rear of the aerofoil, resulting in substantially less drag.
Show Worked Solution

  • Significant surface drag is created by the cable due to its rough surface.
  • Low pressure is created behind the cable due to its non aerodynamic shape, thus pulling the cable backwards and creating sizeable drag.
  • Vortices (turbulence) created behind the cable also produce drag.
  • The smooth surface, and aerodynamic shape of the symmetrical aerofoil, help minimise turbulence at the rear of the aerofoil, resulting in substantially less drag.

ENGINEERING, AE 2016 HSC 25ai

An image of a small drone is shown.
 


  

Explain how this drone achieves flight.   (3 marks)

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  • The weight of the drone is counteracted by rotating propellers that produce vertical thrust (lift).
  • The drone will achieve flight if the vertical thrust exceeds the weight.
  • Controlled climb or descent is achieved by varying the speed of the motor.
  • The direction of flight or thrust can be affected by a change in the rotational speed of the propellers.
  • Power for flight is supplied by battery systems.
Show Worked Solution
  • The weight of the drone is counteracted by rotating propellers that produce vertical thrust (lift).
  • The drone will achieve flight if the vertical thrust exceeds the weight.
  • Controlled climb or descent is achieved by varying the speed of the motor.
  • The direction of flight or thrust can be affected by a change in the rotational speed of the propellers.
  • Power for flight is supplied by battery systems.

Mean mark 54%.

ENGINEERING, AE 2018 HSC 25c

 A two-engine aircraft with mass 330 tonnes is climbing at 15°. Each engine produces 510 kN of thrust. The aircraft maintains a constant velocity.

  1. Complete the space diagram by indicating the four key forces of flight for this situation.   (2 marks)
     
     

  1. Determine the induced drag force for this situation.   (3 marks)
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i.

ii.   `166\ text{kN}`

Show Worked Solution

i.

ii.  `text{Find Induced drag} (D):`

`text{Weight}\ (W)=text{m} xx text{g}=330 xx 10^3 xx 10=33 xx 10^5\ text {N}`

`text{Thrust}\ (T)=510 xx 10^3 xx 2=102 xx 10^4\ \text{N}`

`T` `= D + W\ sin\ gamma`  
`D` `= T-W\ sin\ gamma`  
  `=102 xx 10^4  –  33 xx 10^5\ sin15^\circ`  
  `=165\ 897.1512`  
  `=166 xx 10^3`  
  `=166\ text{kN}`  

♦♦ Mean mark (ii) 34%.

ENGINEERING, AE 2019 HSC 25d

The photograph shows a board with a hydrofoil attached underneath.

The hydrofoil is used to lift the board out of the water as the rider is towed behind a boat at high speed.

Explain why the hydrofoil can lift the board out of the water when it is travelling at high speed.   (3 marks)

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  • Water flows around and over the board as it moves forwards.
  • A difference in pressure is created above (low pressure) and below (high pressure) the hydrofoil due to its shape.
  • The board lifts upwards due to the higher pressure created by the hydrofoil from under the board.
  • The deflection of water downwards also creates lift (an upward reaction force) at the trailing edge.
  • The board is lifted out of the water once a critical speed is reached.
Show Worked Solution
  • Water flows around and over the board as it moves forwards.
  • A difference in pressure is created above (low pressure) and below (high pressure) the hydrofoil due to its shape.
  • The board lifts upwards due to the higher pressure created by the hydrofoil from under the board.
  • The deflection of water downwards also creates lift (an upward reaction force) at the trailing edge.
  • The board is lifted out of the water once a critical speed is reached.

ENGINEERING, AE 2019 HSC 25a

Modern racing yachts are now designed using aeronautical engineering principles.

   

The diagram shows the hull of a racing yacht.
 

How can engineers use an understanding of the effects of drag to improve the design of racing yacht hulls?   (3 marks) 

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  • Drag minimisation leads to increased speeds as maximum forward thrust can be achieved.
  • Streamlining the hull leads to less countercurrents (vortices).
  • Surfaces with a high sheen minimise drag.
  • The use of lightweight construction materials creates less drag.
Show Worked Solution
  • Drag minimisation leads to increased speeds as maximum forward thrust can be achieved.
  • Streamlining the hull leads to less countercurrents (vortices).
  • Surfaces with a high sheen minimise drag.
  • The use of lightweight construction materials creates less drag.

ENGINEERING, AE 2022 HSC 24c

An image of a glider is shown.

The glider is currently on a descent at an angle of 19 degrees. The total lift force is 6250 N.

  1. Draw a free-body diagram, indicating all forces acting on the glider.   (1 mark)   
  1. If the mass of the pilot is 95 kg, calculate the mass of the glider.   (3 marks)
  1. Calculate the lift-to-drag ratio.   (2 marks)
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i.   Free-body diagram

ii.  Mass of the glider

`text{cos}19°` `=6250/W`  
`W` `=6250/(\text{cos}19°)=6610.13N`  

 
`m=6610.13/10=661.01\ text{kg}`

`:. m_text{glider} =661.01-95=566.01\ text{kg}`
 

iii.    `(text{Lift})/(text{Drag})` `=(Wcos19°)/(Wsin19°)=1/(tan19°)`

 
`:.\ text{Lift : Drag}\ = 2.9 : 1`

Show Worked Solution

i.   Free-body diagram
 


♦ Mean mark (i) 49%.

ii.  Mass of the glider

`text{cos}19°` `=6250/W`  
`W` `=6250/(\text{cos}19°)=6610.13N`  

 
`m=6610.13/10=661.01\ text{kg}`

`:. m_text{glider} =661.01-95=566.01\ text{kg}`


♦ Mean mark (ii) 46%.
iii.    `(text{Lift})/(text{Drag})` `=(Wcos19°)/(Wsin19°)=1/(tan19°)`

 
`:.\ text{Lift : Drag}\ = 2.9 : 1`


♦♦ Mean mark (iii) 37%.

ENGINEERING, AE 2022 HSC 10 MC

Which of the following identifies two causes of parasitic drag?

  1. Aircraft lift, angle of attack
  2. Aircraft lift, material of aircraft skin
  3. The movement of air over the wing, angle of attack
  4. The movement of air over the wing, material of aircraft skin
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`D`

Show Worked Solution
  • Parasitic drag is all drag that is caused by the shape, construction-type and material of an aircraft.

`=>D`


♦♦ Mean mark 37%.

ENGINEERING, AE 2020 HSC 7 MC

Which of the following best describes how an unpowered aircraft will glide, in a controlled descent, when the lift-to-drag ratio is high?

  1. Long distance at a steep glide angle
  2. Short distance at a steep glide angle
  3. Long distance at a shallow glide angle
  4. Short distance at a shallow glide angle
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`C`

Show Worked Solution
  • High lift to drag ratio means the aircraft will travel a long distance (low drag) at a shallow angle (high lift).

`=>C`

ENGINEERING, AE 2020 HSC 2 MC

What is the main purpose of the flaps on the wings of an aircraft?

  1. To make the aircraft safer at higher speeds
  2. To decrease lift to allow faster take-off speeds
  3. To increase lift at lower speeds for take-off and landing
  4. To decrease drag to allow higher take-off and landing speeds
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`C`

Show Worked Solution
  • The purpose of the flaps is to generate more lift at lower speeds.
  • This enables aircraft to fly at greatly reduced speeds with a lower risk of stalling.

`=>C`

ENGINEERING, AE 2021 HSC 23c

A 3000 kg aircraft is flying in level flight at constant speed.

Using a free-body diagram, calculate the thrust on the plane if the lift to drag ratio of the aircraft is 11:1.   (3 marks)

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`2.73\ text{kN}`

Show Worked Solution

`text{Lift} = 30\ 000\ text{N}↑`

`text{Find drag}\ (D):`

`L/D` `= 11/1\ \ text{(given)}`  
`(30\ 000)/D` `= 11/1\ text{N}`  
`D` `= (30\ 000)/11= 2730\ text(N)`  

 
`:.\ text{Plane’s thrust} = 2.73\ text(kN)`


Mean mark 56%.

ENGINEERING, AE 2021 HSC 13 MC

Two identical aircraft, `Q` and `R`, are travelling at 500 km per hour. Aircraft `Q` is at an altitude of 1000 m and aircraft `R` is at an altitude of 10 000 m.

Compared to aircraft `Q`, aircraft `R` generates

  1. less lift and less drag.
  2. less lift and more drag.
  3. more lift and less drag.
  4. more lift and more drag.
Show Answers Only

`A`

Show Worked Solution
  • Flying at higher altitude produces less lift as there is lower air pressure under the wing.
  • The low air pressure at high altitude also decreases drag.

`=>A`

♦ Mean mark 44%.