DGCA Technical General: Propellers Questions
193 exam-style Propellers questions for the DGCA Technical General paper (CPL · ATPL · PPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
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Q1
What is the most common reason for increasing the number of blades on a propeller?
- A Increase aerodynamic efficiency.
- B Reduce propeller noise.
- C Increase power absorption capability.
- D Increase the effectiveness of the constant speed unit.
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Correct answer: C. Increase power absorption capability.
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Q2
Propeller blade angle is
- A The angle between the blade chord and the plane of rotation
- B The angle between the relative airflow and the chord
- C Dependent upon RPM and TAS
- D The difference between effective pitch and geometric pitch
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Correct answer: A. The angle between the blade chord and the plane of rotation
Propeller blade angle is the angle between the blade chord line and the plane of rotation of the propeller disc. It should not be confused with angle of attack, which is measured from the relative airflow.
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Q3
Which of the following will increase the gyroscopic precession effect of a propeller?
- A lncreased angle of attack.
- B Decreased TAS.
- C Pitch and roll.
- D lncreased RPM
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Correct answer: D. lncreased RPM
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Q4
Why is a propeller blade twisted
- A To reduce the thrust at the root of the blade
- B To prevent the blade from fully feathering
- C To reduce the tip speed
- D To even out the thrust force along the length of the blade
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Correct answer: D. To even out the thrust force along the length of the blade
A propeller blade is twisted, or has washout from root to tip, because the higher rotational speed at the tip would otherwise generate far more thrust there than at the slow-moving root. Decreasing the blade angle toward the tip evens out the thrust, and hence the loading, along the whole blade.
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Q5
A constant speed propeller aircraft is descending with the throttle closed and KPM lever set at 2000 RPM. What would be the effect of retarding the propeller lever?
- A Rate of descent would remain constant and RPM would increase.
- B Rate of descent would remain constant and RPM would decrease.
- C Rate of descent and RPM would increase.
- D Rate of descent and RPM would decrease.
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Correct answer: D. Rate of descent and RPM would decrease.
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Q6
What effect does the torque reaction of a single right handed tractor propeller have during the take-off roll?
- A Weight on the right wheel increases while that on the left decreases.
- B Weight on the right wheel decreases while that on the left increases.
- C Weight on the right and left wheels decreases.
- D Weight on the right and left wheels increases.
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Correct answer: B. Weight on the right wheel decreases while that on the left increases.
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Q7
What would be the result of propeller slipstream effect when taking-off using a single right handed tractor propeller?
- A Pitch up.
- B Pitch down
- C Yaw to the right.
- D Yaw to the left.
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Correct answer: D. Yaw to the left.
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Q8
432.How do we achieve efficient angle of attack over the propeller blade?
- A By increasing blade angle from propeller root to propeller tip
- B Reducing blade angle from propeller root to propeller tip
- C increasing blade angle from propeller tip to propeller root
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Correct answer: B. Reducing blade angle from propeller root to propeller tip
Because the tip of a propeller blade travels much faster than the root, the blade is twisted so the blade angle reduces progressively from root to tip, keeping the angle of attack efficient along the entire blade.
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Q9
Which of the following statements about propellersis true?
- A Angle of attack is the angle between the chord line of the blade and the plane of rotation.
- B Critical tip speed is the RPM at which there is a risk of some part of the blade stalling.
- C Geometric pitch is the distance that a propeller would move forward in one turn if there were no slip.
- D Blade angle is the angle between the chord line of the blade and the shaft axis.
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Correct answer: C. Geometric pitch is the distance that a propeller would move forward in one turn if there were no slip.
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Q10
What happens to the angle of attack of a fixed pitch propeller as the aircraft accelerates down the runway
- A Increases
- B Decreases
- C Remains the same
- D Blade angle changes to compensate for forward speed
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Correct answer: B. Decreases
With a fixed pitch propeller the blade angle cannot change, so as the aircraft accelerates the increasing forward speed alters the relative airflow and the blade angle of attack decreases. This is why a fixed pitch propeller is only efficient at one speed and RPM combination.
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Q11
Which of the following conditions will occur when a propeller is feathered?
- A The highest windmilling speed.
- B The maximum D:L ratio.
- C Minimum aerodynamic drag on the propeller.
- D Lowest blade angle.
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Correct answer: C. Minimum aerodynamic drag on the propeller.
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Q12
What happens to the AoA of a VP propeller with increasing TAS if the RPM and throttle levers are not moved.
- A Blade angle remains constant to compensate for forward speed
- B Increases
- C Decreases
- D Remains the same
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Correct answer: D. Remains the same
With the levers untouched, the constant speed unit maintains the selected RPM by coarsening the blade angle as true airspeed increases. Because the blade angle increases in step with the changing relative airflow, the blade angle of attack remains essentially the same.
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