Understanding Altimeters and Pitot Tubes

What does a standard aircraft altimeter measure?

• Temperature

• Atmospheric pressure

• Airspeed

• Lift force

Answer explanation

A standard aircraft altimeter measures atmospheric pressure. It uses changes in pressure to determine altitude, as pressure decreases with an increase in altitude.

How does the altitude reading on an aneroid barometer altimeter change as an aircraft climbs?

• Increases as atmospheric pressure decreases

• Increases as atmospheric pressure increases

• Decreases as temperature increases

• Stays the same unless manually adjusted

Answer explanation

As an aircraft climbs, atmospheric pressure decreases. An aneroid barometer altimeter measures this pressure change, causing the altitude reading to increase. Thus, the correct answer is that altitude increases as atmospheric pressure decreases.

What principle is used to determine airspeed in a Pitot-static system?

• Newton’s Third Law

• Bernoulli’s Principle

• Archimedes’ Principle

• Pascal’s Law

Answer explanation

Bernoulli’s Principle explains how the pressure difference created by varying airspeed in a Pitot-static system allows for the measurement of airspeed. It relates the speed of fluid flow to its pressure.

What is the likely result if a Pitot tube becomes completely blocked?

• The altimeter will give false readings

• The airspeed indicator will freeze at its last reading

• The aircraft will lose lift

• The static port will malfunction

Answer explanation

If a Pitot tube is completely blocked, the airspeed indicator will not receive any dynamic pressure changes and will freeze at its last reading, leading to inaccurate airspeed information.

What happens if the static port is blocked while the Pitot tube remains clear?

• The altimeter reads normally, but airspeed readings are incorrect

• Both the altimeter and airspeed indicator stop working

• The airspeed indicator shows incorrect readings based on altitude changes

• The airspeed indicator functions normally

Answer explanation

When the static port is blocked, the airspeed indicator will show incorrect readings because it relies on static pressure to measure airspeed. The readings will vary with altitude changes, leading to inaccuracies.

Describe the function of an aneroid barometer altimeter and how it determines altitude.

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Answer explanation

An aneroid barometer altimeter measures atmospheric pressure to determine altitude. As altitude increases, pressure decreases; the altimeter calibrates this change to provide an accurate altitude reading.

List two sources of error that may affect the accuracy of an altimeter and explain how they impact altitude readings.

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Answer explanation

Two sources of error for altimeters are temperature variations and atmospheric pressure changes. Temperature affects air density, leading to inaccurate altitude readings, while pressure changes can cause the altimeter to misinterpret altitude, resulting in errors.

Explain how a Pitot tube is used to measure airspeed and describe how Bernoulli’s Principle applies.

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Answer explanation

A Pitot tube measures airspeed by comparing static and dynamic pressure. According to Bernoulli’s Principle, as airspeed increases, dynamic pressure rises while static pressure drops, allowing the calculation of airspeed from these pressure differences.

Describe the effects of the following blockages in an aircraft’s Pitot-static system:

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Answer explanation

Blockages in the Pitot-static system can lead to incorrect airspeed and altitude readings. A blockage in the Pitot tube results in a loss of airspeed indication, while a static port blockage can cause erroneous altitude and vertical speed readings.

A pilot notices the airspeed indicator is reading unusually high while descending. Suggest a possible reason for this and how the issue can be resolved.

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Answer explanation

The high airspeed reading during descent may be due to a malfunctioning airspeed indicator or incorrect static pressure input. To resolve this, the pilot should cross-check with other instruments and consider switching to an alternate static source.