Aerospace Instruments Overview
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Questions and Answers

What is the primary purpose of the International Standard Atmosphere (ISA)?

  • To standardize pilot training procedures
  • To provide standard values for meteorological studies
  • To provide standard values for calibration of barometric instruments (correct)
  • To regulate air traffic control procedures

Which of the following conditions does ISA define at Mean Sea Level (MSL)?

  • A temperature of 20° C and air pressure of 29.92 inches of mercury
  • A temperature of 0° C and air pressure of 1013.25 hPa
  • A temperature of 10° C and air pressure of 1012 hPa
  • A temperature of 15° C and air pressure of 14.7 psi (correct)

At what altitude does the stratosphere maintain a constant temperature according to ISA?

  • 50,000 feet
  • 40,000 feet
  • 20,000 feet
  • 36,089 feet (correct)

How does temperature change with altitude from Mean Sea Level (MSL) in the troposphere according to ISA?

<p>Temperature decreases by 2° C for every 1,000 feet (C)</p> Signup and view all the answers

Which of the following is NOT one of the terms defined for airspeed indicators?

<p>Equilibrium Airspeed (EAS) (A)</p> Signup and view all the answers

What does the abbreviation 'Q' in International Q Code by ICAO represent?

<p>Questions related to aviation meteorology (D)</p> Signup and view all the answers

What principle does a barometric altimeter primarily rely upon?

<p>Changes in air pressure with altitude (D)</p> Signup and view all the answers

What component is used in the Vertical Speed Indicator to measure changes in altitude?

<p>Diaphragm (C)</p> Signup and view all the answers

What is the standard atmospheric pressure at mean sea level (MSL)?

<p>1,013.25 hPa (D)</p> Signup and view all the answers

What is the temperature lapse rate with altitude according to standard conditions?

<p>2 degC./1000 ft (B)</p> Signup and view all the answers

During a descent, what causes the pointer of the airspeed indicator to deflect downwards?

<p>Higher pressure inside the chamber (A)</p> Signup and view all the answers

What happens to the airspeed indicator's diaphragm and pointer when the aircraft speed is increased?

<p>Diaphragm expands and pointer moves up (D)</p> Signup and view all the answers

What types of pressure are utilized in an airspeed indicator?

<p>Static and dynamic pressure (C)</p> Signup and view all the answers

What is the primary function of the Encoding Disc in an Encoding Altimeter?

<p>To encode altitude information (C)</p> Signup and view all the answers

What indicates a failure condition in the Encoding Altimeter?

<p>Altitude information is not encoded (D)</p> Signup and view all the answers

Which components are involved in encoding the altitude in the Encoding Altimeter?

<p>10 LEDs and 10 light-sensitive Darlington transistors (B)</p> Signup and view all the answers

What does the Vertical Speed Indicator measure?

<p>Rate of altitude change (C)</p> Signup and view all the answers

What is the role of the diaphragm in the Vertical Speed Indicator?

<p>To detect changes in static pressure (A)</p> Signup and view all the answers

How many concentric rings does the Encoding Disc have?

<p>10 rings (B)</p> Signup and view all the answers

What is the altitude range that the 10-bit encoding of the Encoding Altimeter covers?

<p>-1,000 feet to +63,000 feet (D)</p> Signup and view all the answers

What does the Vertical Speed Indicator primarily utilize to measure changes in altitude?

<p>Static pressure of the pitot static system (B)</p> Signup and view all the answers

What is the function of the triple-pointer type altimeter?

<p>To indicate altitude based on atmospheric pressure (B)</p> Signup and view all the answers

Which atmospheric pressure standard is typically used for intercontinental flights?

<p>QNE (D)</p> Signup and view all the answers

What does the acronym ICAO stand for?

<p>International Civil Aviation Organization (B)</p> Signup and view all the answers

What temperature does the ICAO standard atmosphere define at mean sea level (MSL)?

<p>15° C (C)</p> Signup and view all the answers

What is the air pressure specified in the ICAO standard atmosphere?

<p>1013.25 hPa (B)</p> Signup and view all the answers

When using QFE, what would the altimeter read when the aircraft is on the ground at the airfield?

<p>0 feet (A)</p> Signup and view all the answers

Which of the following is NOT a type of altimeter mentioned?

<p>Analog-barometric altimeter (C)</p> Signup and view all the answers

What does QNH represent in altimeter settings?

<p>Prevailing pressure at an airfield (B)</p> Signup and view all the answers

What is the role of the diaphragm in an airspeed indicator?

<p>It measures the difference between total pressure and static pressure. (B)</p> Signup and view all the answers

What happens to the airspeed indicator pointer when the forward speed of the aircraft increases while maintaining a constant altitude?

<p>It moves up-scale. (D)</p> Signup and view all the answers

Which of the following pressure types is measured by the Pitot static tube?

<p>Total pressure and static pressure. (B)</p> Signup and view all the answers

What is dynamic pressure in the context of the airspeed indicator?

<p>Total pressure minus static pressure. (A)</p> Signup and view all the answers

What is indicated by the airspeed indicator when the aircraft's altitude is ascending but the forward speed remains constant?

<p>Pointer remains unchanged. (C)</p> Signup and view all the answers

If the diaphragm of the airspeed indicator becomes punctured, what effect does this have on functionality?

<p>It may lead to fluctuating airspeed indications. (A)</p> Signup and view all the answers

In an airspeed indicator, how does the diaphragm respond to increased dynamic pressure?

<p>It expands. (A)</p> Signup and view all the answers

Which of the following is NOT a marked pressure connection on an airspeed indicator?

<p>D for Dynamic pressure pipe. (C)</p> Signup and view all the answers

What happens to the speed of sound as temperature falls with altitude?

<p>It decreases. (B)</p> Signup and view all the answers

At what temperature is the speed of sound at 36,000 feet recorded?

<p>-56.5°C (A)</p> Signup and view all the answers

If an aircraft is flying at an indicated 0.7 Mach at MSL, what is its speed?

<p>462.7 knots (D)</p> Signup and view all the answers

What effect does an increase in altitude have on static pressure?

<p>It decreases. (D)</p> Signup and view all the answers

What function do the mechanical stops serve in the airspeed indicator?

<p>To prevent exceeding the maximum safe airspeed. (B)</p> Signup and view all the answers

What is the relationship between maximum safe airspeed and Mach number?

<p>Maximum safe airspeed is a function of both static pressure and Mach number. (A)</p> Signup and view all the answers

What is the purpose of colour markings on airspeed indicators?

<p>To highlight specific operating limits. (C)</p> Signup and view all the answers

What is the speed of an aircraft at 0.7 Mach when flying at 40,000 feet?

<p>401.1 knots (D)</p> Signup and view all the answers

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Flashcards

What is the purpose of ISA?

The purpose of the International Standard Atmosphere (ISA) is to establish a set of standard atmospheric conditions.

What values does ISA define?

The International Standard Atmosphere (ISA) provides standard values for pressure, temperature, and density at different altitudes.

What are the standard conditions at MSL in ISA?

At Mean Sea Level (MSL), the ISA defines a standard temperature of 15°C, air pressure of 1013.25 hectopascals (hPa), and a standard density.

What does the Airspeed Indicator display?

The Airspeed Indicator (ASI) shows the speed of an aircraft relative to the air it's flying through.

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What is Indicated Airspeed (IAS)?

Indicated Airspeed (IAS) is the speed shown on the Airspeed Indicator.

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What is Calibrated Airspeed (CAS)?

Calibrated Airspeed (CAS) is corrected for instrument error, but not for air density.

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What is Equivalent Airspeed (EAS)?

Equivalent Airspeed (EAS) is adjusted for air density, providing a closer representation of the aircraft's actual motion.

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What is True Airspeed (TAS)?

True Airspeed (TAS) is the actual speed of the aircraft relative to the air, accounting for all factors.

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What is ICAO?

International Civil Aviation Organization (ICAO) is a specialized agency of the United Nations which sets standards and regulations for international air travel, communication and navigation.

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What is the value of Standard Atmospheric Pressure?

Standard atmospheric pressure at mean sea level (MSL) is 1013.25 hectopascals (hPa), 29.92 inches of mercury (inHg), or 14.7 pounds per square inch (psi).

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What is the temperature lapse rate with altitude?

The standard temperature lapse rate is 2 degrees Celsius per 1,000 feet (or 6.5 degrees Celsius per 1,000 meters).

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What is the purpose of the Air Speed Indicator?

The Air Speed Indicator (ASI) measures an aircraft's speed relative to the surrounding air, crucial for navigation and flight control.

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What unit are Airspeed Indicators calibrated in?

Airspeed indicators typically measure airspeed in knots (nautical miles per hour).

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ICAO Standard Atmosphere (ISA)

A standard set of atmospheric conditions used for aviation calculations and measurements.

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QFE

The pressure at a specific airfield, measured at sea level, that makes the altimeter read zero when the aircraft is on the ground at that airfield.

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QNE

The standard atmospheric pressure at sea level, used for altitude calculations.

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QNH

The pressure at a specific airfield, adjusted to sea level, that makes the altimeter read the airfield's elevation when the aircraft is on the ground at that airfield.

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Triple-pointer Altimeter

A type of altimeter that uses three pointers to indicate altitude.

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Single-pointer Altimeter with Digital Counter

A type of altimeter that uses a single pointer and a digital counter to display altitude.

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Single-pointer Altimeter with Drum Presentation

A type of altimeter that uses a single pointer and a drum to indicate altitude.

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QNH

The pressure at a specific airfield, adjusted to sea level, that makes the altimeter read the airfield's elevation when the aircraft is on the ground at that airfield.

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Dynamic Pressure

The difference between the total pressure and static pressure. The greater the dynamic pressure, the greater the airspeed indicator reading.

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Static Pressure

The pressure measured at a point where there is no airflow, representing the atmospheric pressure.

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Total Pressure (Pt)

The total pressure measured at the point where the air is struck by the aircraft, influenced by both static and dynamic pressure.

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Airspeed Indicator Diaphragm

A flexible, sealed diaphragm, typically made of metal, used in airspeed indicators to measure the difference between total pressure and static pressure (dynamic pressure).

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Forward Speed Increases (Constant Altitude)

If forward speed increases while maintaining altitude, dynamic pressure increases. This causes the diaphragm to expand, resulting in a higher airspeed indication.

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Aircraft Ascend (Constant Speed)

When the aircraft ascends, the static pressure decreases, resulting in a higher dynamic pressure. This causes the diaphragm to expand, but the airspeed indication decreases as the dynamic pressure change is a result of altitude change.

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Aircraft Diaphragm Puncture

If the diaphragm is punctured, it loses its ability to sense air pressure. This results in an inaccurate or erratic airspeed indication, as the diaphragm can no longer measure the dynamic pressure.

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Airspeed Indicator (ASI)

The airspeed indicator (ASI) provides visual information about an aircraft's speed relative to the surrounding air.

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Speed of Sound and Altitude

The speed of sound decreases as altitude increases due to the decrease in air temperature.

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Mach Number

Mach number is a unitless measure of an aircraft's speed relative to the speed of sound. An indicated Mach number of 0.7 means the aircraft is flying at 70% of the speed of sound.

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Maximum Safe Airspeed (VMO/MMO)

The maximum safe airspeed (VMO/MMO) is the highest speed an aircraft can fly safely without causing structural damage. It is determined by the aircraft's design and is typically lower at higher altitudes due to the decrease in air density.

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Aneroid Capsule

An aneroid capsule is a sealed container that expands and contracts with changes in static pressure. This movement is used to measure altitude in an altimeter and airspeed in an airspeed indicator.

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Airspeed Indication and Altitude

As altitude increases, static air pressure decreases, causing the aneroid capsule in the airspeed indicator to expand. This expansion rotates the airspeed pointer counterclockwise, indicating a lower maximum safe airspeed.

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Color Marking on Airspeed Indicators

Airspeed indicators are marked with color bands to highlight specific speed limits or ranges for different operations. These markings help pilots maintain safe flight parameters.

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Importance of Airspeed Indicators

Aircraft operators must adhere to published speed limits and color-coded markings on airspeed indicators to maintain safe flight operations. These markings are essential for structural integrity and preventing overspeeding.

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Mechanical Stop

A mechanical stop is a device built into an airspeed indicator to prevent the pointer from indicating a speed higher than the aircraft's maximum safe airspeed. This safety feature protects the aircraft from structural damage during overspeeding.

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What is the function of the Vertical Speed Indicator?

This instrument tells you how fast the aircraft is climbing or descending in feet per minute (or meters per second). It works by measuring changes in static air pressure.

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How does the encoding disc in an Encoding Altimeter work?

The encoding disc is made of glass and has concentric rings with etched sections that either block or allow light to pass through. These rings represent a 10-bit code called 'MOA-GILHAM' that indicates the altitude in 100-foot increments.

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What is the altitude range covered by the 10-bit encoding on an Encoding Altimeter?

The 10-bit encoding covers a wide range of altitudes, from -1,000 feet to +63,000 feet.

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What does the Warning Flag on an Encoding Altimeter signify?

The Encoding Altimeter's Warning Flag indicates problems like power failure, lost altitude information, or a malfunctioning vibrator.

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How does a diaphragm-based Vertical Speed Indicator operate?

It uses static pressure from the Pitot-static system to detect changes in air pressure. This pressure difference is sensed by a diaphragm, which moves according to the rate of climb or descent.

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How is altitude represented on an Encoding Altimeter?

The Encoding Altimeter's disc uses a 10-bit code to represent altitude. Each revolution of the disc corresponds to a change of 100 feet in altitude.

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How does the Encoding Altimeter measure altitude?

Sensor modules contain LEDs and light-sensitive transistors that detect the passing light patterns on the encoding disc to determine altitude.

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What are the conditions that trigger the warning flag on an Encoding Altimeter?

Encoding Altimeter's warning flag comes ON in case of power failure, loss of altitude information, or vibrator malfunction.

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Study Notes

Barometric Instruments

  • Barometric instruments are used to measure atmospheric pressure and altitude.
  • Different types of instruments exist for different purposes.

ICAO Standard Atmosphere (ISA)

  • The ISA provides standard atmospheric values, used for calibrating instruments.
  • Standard conditions at mean sea level (MSL) are 15°C temperature, 14.7 psi/1013.25 hPa/29.92 in Hg pressure.

Airspeed Indicator (ASI)

  • Displays the speed of an aircraft relative to the surrounding air.
  • Calculated using dynamic pressure (pitot pressure - static pressure)
  • Airspeed types: IAS (uncorrected), CAS (compensated for instrument and installation errors), EAS (compensated for compressibility), TAS (compensated for actual altitude density), and Mach number (relative to the speed of sound).
  • Important components: diaphragm, pointer, temperature compensation (bimetallic strip), pitot tube and static pressure pipe.

Mach Number Indicator

  • Indicates the speed of an aircraft relative to the speed of sound (Mach number).
  • Mach number is the ratio of the aircraft's speed to the speed of sound.

Altimeter

  • Measures the altitude of the aircraft.
  • Uses atmospheric pressure to determine altitude, accounting to air pressure changes
  • QFE- airfield height above local MSL
  • QNH- airfield height above standard MSL, using standard atmospheric pressure.
  • QNE, standard pressure (1013.25 hPa)
  • Different types include multi-pointer, counter-pointer, Encoding altimeter.

Vertical Speed Indicator (VSI)

  • Measures the rate of change of altitude (vertical speed).
  • Uses static pressure.
  • A differential pressure gauge.
  • Shows if the aircraft is climbing/descending/maintaining altitude.

Encoding Altimeter

  • A type of altimeter that transmits height information to ground control / ATC.
  • Uses a 10-bit code "MOA-GILHAM".

Colour Marking of Indicators

  • Colour markings on instruments provide visual cues for operational limits of the aircraft.
  • Different colour codes indicate safe altitudes, precautionary levels, maximum/minimum or restricted speed ranges.

Summary of Barometric Instruments

  • Barometric instruments include the Airspeed Indicator, Altimeter, Vertical Speed Indicator, and Mach Number indicator.
  • Instruments differ in how they measure and display data.

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Barometric Instruments PDF

Description

This quiz explores various aerospace instruments used to measure atmospheric pressure, altitude, and airspeed. Participants will learn about barometric instruments, the ICAO Standard Atmosphere, airspeed indicators, and Mach number indicators. Test your knowledge on their functions and components.

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