Pitot Tube Questions and Answers

Aerodynamics Questions and Answers – Pitot Tube

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Pitot Tube”.

1. In a pitot tube, the kinetic energy is converted into _________
a) potential energy
b) total energy
c) pressure energy
d) internal energy

Explanation: When the flow velocity reaches zero, the pressure rises as kinetic energy is converted to pressure energy, resulting in the formation of the pressure differential.

2. The lower end of the pitot tube is bet at an angle of ____________
a) 120 degrees
b) 360 degrees
c) 90 degrees
d) 45 degrees

Explanation: The tube’s lower end is curved at a 90-degree angle. Due to the conversion of kinetic energy into pressure energy, the liquid rises in the tube. The rising of the liquid in the tube is used to calculate the velocity.

3. The errors generated in the pitot tube due to the location are called __________
a) position errors
b) normal errors
c) negligible errors
d) positive errors

Explanation: Position errors are errors that occur as a result of the positioning of the pitot tube on an aircraft as well as the effect of localised airflow over the pitot tube. These inaccuracies must be taken into account when performing calculations.

4. When an aircraft is grounded, the pitot static tube is generally covered.
a) True
b) False

Explanation: The pitot static tubes are normally covered in the grounded condition to protect them from the effects of the atmosphere. It may exhibit various fluctuations in the reading if ambient air enters it.

5. The pressure measured relative to vacuum is ______
a) total pressure
b) static pressure
c) dynamic pressure
d) absolute pressure

Explanation: The measurement of absolute pressure is done in relation to vacuum. The absolute pressure of a vacuum is 0 psi. It’s also known as the total of gauge and atmospheric pressures.

6. The most common device used for measuring air speed is __________
a) altimeter
b) thermometer
c) pressure gauge
d) pitot tube

Explanation: A pitot tube is an L-shaped tube. The pitot tube’s one end is exposed to the air, allowing it to come into direct touch with the flow velocity. The velocity is measured by the pressure inside the tube.

7. The randomness of the molecules gives us ________ pressure.
a) Stagnation
b) Static
c) Dynamic
d) Absolute

Explanation: The static pressure of a gas is a measure of the molecules’ totally random motion. It’s the pressure we experience when we’re riding along with the gas at the local flow rate. For the sake of clarity, we always refer to pressure as static pressure.

8. How does the pitot tube help in measuring the airspeed?
a) Using temperature
b) Using velocity
c) Using mach number
d) Using the pressure difference

Explanation: The pitot tube has one end that is closed and the other end that is open. When the tube is filled with air, the pressure at the open end equals total pressure and is different from the pressure outside. The speed of air can be determined using this pressure differential and Bernoulli’s equation.

9. The instrument which combines both the static and total pressure is _______
a) Dynamic probe
b) Static probe
c) Pitot static probe
d) Stagnation probe

Explanation: A pitot static probe combines static and total pressure measurements. It monitors p0 at the probe’s nose and p1 at a suitable static pressure tap downstream of the nose on the probe surface.

10. The dynamic pressure can be used in all flows from incompressible to hypersonic.
a) True
b) False

Explanation: The dynamic pressure can be applied to any flow. It is the grouping of density and velocity in which the density is halfed and the velocity is squared, and it is symbolised by the letter ‘q.’

11. The dynamic pressure can be given by ____________
a) difference of total and static pressure
b) sum of total and static pressure
c) product of total and static pressure
d) double of total and static pressure

Explanation: In incompressible flow, the dynamic pressure has a special meaning, it is a difference between the total pressure and the static pressure. Let p0 be the total pressure and p1 be the static pressure.
Therefore, the dynamic pressure (q)= total pressure (p0)- static pressure (p1).

12. The pressure difference (p0-p1) holds good only for incompressible flow.
a) True
b) False

Explanation: The difference between total pressure (p0) and static pressure (p1) gives dynamic pressure holds true only for incompressible flow. The Bernoulli’s equation cannot be solved for compressible flow and also the pressure difference is not equal to dynamic pressure (q).

13. When the local flow velocity is zero itself then _________
a) total pressure is not equal to static pressure
b) total pressure is equal to static pressure
c) 0
d) infinity

Explanation: When the total pressure, the static pressure, and the local flow velocity are all the same. Assume that the air in the room is stationary and that the standard sea level pressure is 101314.1 pa (1 atm).

14. An aircraft is flying at cruise level with a velocity of 110m/s at an altitude of 10 km and the dynamic pressure is 5.43kN/m2. Now assume the aircraft is flying is at sea level with a speed of 65m/s and the same dynamic pressure. In the above data, the velocity 65m/s refers to __________
a) true air speed
b) equivalent airspeed
c) free stream velocity
d) cruising speed

Explanation: The speed at which an aircraft should fly in order to retain the same dynamic pressure is referred to as equivalent airspeed. The corresponding airspeed at an altitude of 10km flying at a true airspeed of 110 m/s is 65 m/s in the case above.

15. Pitot tube with flat faces are more sensitive.
a) True
b) False

Explanation: Flat-faced pitot tubes are the least sensitive. For misalignment as large as 20 degrees, the total pressure measurement differs only 1% for these tubes.

To obtain the velocity pressure from which air velocity may be calculated, a Pitot tube detects total pressure and static pressure. The tip of the Pitot tube is directed toward the airflow as it is put into the duct. After then, the manometer will show velocity pressure, which may be translated to velocity. A pitot tube is just a tube that points straight into a fluid flow. Because this tube contains fluid, a pressure can be measured; however, because there is no outlet, the moving fluid comes to a halt (stagnates). The front hole is inserted into the airstream to determine the pressure of stagnation.

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