Aircraft Maintenance: Torque and Fasteners

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Questions and Answers

What type of nuts typically require lower torque values?

Shear nuts (correct)

Pipe union nuts

Critical bolted joints

Bolted joints

What is the purpose of a torque wrench?

To measure the length of a fastener

To determine the material of a fastener

To measure the amount of torque required to turn a fastener (correct)

To apply a fixed amount of force to a fastener

Why is correct torquing important for bolts?

To ensure the bolt is subject to its metallic stress strain (correct)

To ensure the bolt is over-torqued

To ensure the bolt is not subject to any stress

To ensure the bolt is tightened loosely

How is the amount of torque calculated?

By multiplying the applied force and the lever arm Signup and view all the answers

How should a torque wrench (except dial type) be held to operate accurately?

At the knurled handle Signup and view all the answers

What type of torque wrench uses a beam that deflects under load?

Flexible beam type torque wrench Signup and view all the answers

What is a unique characteristic of PLI washers?

They can only be used once and must be replaced if slackened Signup and view all the answers

Why is accurate measurement essential in aircraft maintenance?

To ensure the correct functioning and reliability of engines Signup and view all the answers

What is the first step in using a precision measuring instrument?

Zero the instrument Signup and view all the answers

What is required to ensure precision measuring instruments are reliable?

Regular inspection, service, and calibration Signup and view all the answers

Why is it important to observe in-service limits?

To ensure wear limits are not exceeded Signup and view all the answers

What should a technician do if a precision measuring instrument does not zero correctly?

Calibrate the instrument Signup and view all the answers

What is the pitch of the spindle of the English micrometer?

1/40 Signup and view all the answers

What does each vertical line on the sleeve of the English micrometer designate?

1/40 or 0.025 in. Signup and view all the answers

What is the distance moved by the spindle longitudinally when the thimble is rotated from one division to the next?

0.001 in. Signup and view all the answers

What is the total distance represented by 25 divisions on the thimble?

0.025 in. Signup and view all the answers

What is the typical range increment of metric micrometers?

25 mm Signup and view all the answers

What is the purpose of the vernier scale on a micrometer?

To measure in 0.002 mm increments Signup and view all the answers

When using a micrometer other than 0–25 mm, what must be added to the reading on the scale?

The gap in the frame Signup and view all the answers

How do you read the metric Vernier micrometer scale?

By adding the normal reading to the vernier scale reading Signup and view all the answers

What type of micrometer gives a digital read-out of measurements?

Electronic micrometer Signup and view all the answers

What is the accuracy of measurements using a Vernier micrometer?

Two thousandths of a millimetre (0.002 mm) Signup and view all the answers

What is the primary purpose of the internal micrometer?

To measure internal dimensions Signup and view all the answers

What is the range of the sleeve scale on an internal micrometer?

1/2 inch Signup and view all the answers

What is the purpose of the collar on an internal micrometer?

To extend the measuring range Signup and view all the answers

What is used to lock the collar in place on an internal micrometer?

A locking screw Signup and view all the answers

What determines the measuring range of an internal micrometer?

The length of the extension rod Signup and view all the answers

What is the purpose of the extension rods on an internal micrometer?

To vary the measuring range Signup and view all the answers

Study Notes

Shear Nuts and Torque Values

Lower torque values are critical for shear nuts and pipe union nuts to prevent failure.
Accurate torque application is essential for the integrity of fasteners, particularly in aviation.

Torque Wrenches

Torque wrenches measure the amount of torque needed to turn fasteners.
The force required to turn is directly related to the internal tensile stress within the fastener.
Torque is calculated as the product of applied force and lever arm length, where lever arm is the distance from the applied force to the driving adapter.
Proper handling is required for accurate torque measurement, especially with non-dial types, which should be held at the knurled handle.

Types of Torque Wrenches

Deflecting Beam Type Wrench: This flexible beam type measures torque through deflection; it must be replaced after use due to compression.
PLI (Preload Indicating) Washers are used in critical bolted joints with self-locking nuts, indicating when proper preload has been achieved.

Calibration and Precision Measurements

Precision measurements are vital in aircraft maintenance to ensure correct part fit and compliance with dimensional tolerances.
Technicians must verify measurement tools by zeroing them before use; instruments that do not zero correctly require calibration.
Regular inspection and calibration of precision measuring tools are essential for maintaining accuracy in measurements.

Standard English Micrometer

English micrometers feature a spindle with a thread of 40 TPI, allowing precise measurement of 0.025 inches per complete revolution.
The sleeve divides the measurement into major divisions of 0.100 inches and smaller divisions of 0.001 inches.
Reading a micrometer involves noting major divisions and counting smaller divisions to achieve a precise measurement down to thousands of an inch.

Metric Micrometers

Metric micrometers are available in increments of 25 mm, with specific ranges for accurate measurement of internal and external dimensions.
The gap in the frame must be added to readings when using micrometers outside of the 0–25 mm range.

Vernier and Electronic Micrometers

Some micrometers are equipped with a vernier scale, providing measurements to an accuracy of 0.002 mm.
Electronic micrometers modernize measurement processes, allowing for quick conversions between imperial and metric systems.

Internal Micrometers

Internal micrometers measure internal dimensions and consist of a measuring head with extension rods.
The measuring range can be adjusted by varying the length of the rods and attaching collars as needed.

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Description

Test your knowledge of torque values and fastener applications in aircraft maintenance, including shear nuts and pipe union nuts. Learn about the importance of correct torquing and the use of torque wrenches and preload indicating washers.