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Aviation Instrumentation Notes-1

The document provides an overview of various aviation instrumentation, including thermocouples, tachogenerators, capacitance fuel quantity systems, magnetic compasses, and operational checks for instruments. It details the principles, construction, and factors affecting each instrument, along with their specific applications in aviation. Additionally, it lists the basic six instruments essential for flight operations.

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10 views5 pages

Aviation Instrumentation Notes-1

The document provides an overview of various aviation instrumentation, including thermocouples, tachogenerators, capacitance fuel quantity systems, magnetic compasses, and operational checks for instruments. It details the principles, construction, and factors affecting each instrument, along with their specific applications in aviation. Additionally, it lists the basic six instruments essential for flight operations.

Uploaded by

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Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Aviation Instrumentation Notes

1. Thermocouple

Definition:

A thermocouple is a temperature-sensing device that converts thermal energy into electrical voltage based on

the Seebeck effect.

Seebeck Effect:

When two dissimilar metals are joined at two junctions and the junctions are at different temperatures, an

EMF is generated.

Materials Used:

- ChromelAlumel (Type K)

- IronConstantan (Type J)

- CopperConstantan (Type T)

Factors Affecting:

- Material type

- Temperature gradient

- Wire length

- Oxidation/corrosion

- Electrical noise

Used For:

- EGT (Exhaust Gas Temp)

- TIT (Turbine Inlet Temp)

- CHT (Cylinder Head Temp)

2. Tachogenerator / Tachometer Generator

Purpose:

Converts mechanical rotation (RPM) into an electrical signal.

Working Principle:
Aviation Instrumentation Notes

Based on Electromagnetic Induction (EMI).

Construction:

- Armature

- Field magnets

- Output terminals

Precautions:

- Inspect with power OFF

- Avoid damage

- Check connections

3. Capacitance and Fuel Quantity Indicating System

Formula: C = (A) / d

Factors:

- Dielectric material

- Plate area

- Distance between plates

- Fuel density

Fuel Quantity Measurement:

- Capacitance sensors per tank

- Connected in parallel

- Capacitance changes with fuel level

- Commonly 3 sensors in A380

Series vs Parallel:

- Parallel gives average value

4. Magnetic Compass
Aviation Instrumentation Notes

Construction:

- Magnetic needle

- Fluid-filled (kerosene or alcohol)

- Lubber line

Purpose of Fluid:

- Reduces friction

- Stabilizes buoyancy

- Dampens oscillation

Errors:

- Magnetic deviation

- Magnetic dip

- Acceleration/deceleration error

Compass Swing Check:

- Rotate aircraft in 30 steps over 360

- Compare with compass rose or DG

- Deviation graph

- Correction screws (non-metallic screwdriver)

- Max acceptable deviation: 10

5. Operational Checks of Instruments

Tachometer:

- Check signal vs RPM

- Generator connection

- Inspect with switch OFF

Thermocouple:

- Compare reading to standard

- Check voltage

- Inspect wires
Aviation Instrumentation Notes

6. Pitot Tube and Heating System

Purpose:

Measures airspeed

Construction:

- Heater around pitot tube

- Switch on pilot side above ACP

Circuit:

- Breaker

- Heater switch

- Relay

- Pitot heater

Learjet/Bonanza Location:

Under wing or nose

7. Magnetic Compass Types

- Wet Compass: Kerosene filled

- Whiskey Compass: Alcohol filled

Use:

- More reliable for long flights

- DG used for short flights

8. Basic Six Instruments

1. Airspeed Indicator

2. Attitude Indicator

3. Altimeter

4. Turn Coordinator

5. Heading Indicator
Aviation Instrumentation Notes

6. Vertical Speed Indicator

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