Bolts EASA

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Questions and Answers

What must be considered when fitting a hylok?

The hylok should be installed with a loose fit.

The hole must allow for more clearance than the hylok size.

The hyloks should be lubricated beforehand.

The torque for each hylok needs to be calculated and applied. (correct)

Which surface treatment is appropriate for magnesium castings?

Painting with epoxy.

Powder coating with polyester.

Electroplating with zinc.

Chromating process. (correct)

What is the correct definition of the nominal length of a UNF bolt?

The total length including the head and threads.

The length measured from the top of the head to the end of the threads.

The length from under the head to where the threads start. (correct)

The length of the unthreaded portion alone.

Under what temperature conditions is it not advisable to use a nyloc nut?

Under temperatures higher than 120 °C. Signup and view all the answers

What does the nominal screw length represent?

The overall length of a countersunk screw plus the bolt’s non-threaded section. Signup and view all the answers

How is a unified thread identified?

By having two or three raised rings on the head. Signup and view all the answers

For a hylok installation, what should the fit be in relation to the drilled hole?

The hole must be an interference fit. Signup and view all the answers

What temperature threshold is critical for the performance of nyloc nuts?

120 °C. Signup and view all the answers

What type of bolt is classified with a single dash on the head?

AN corrosion resistant steel bolt Signup and view all the answers

Which classification is indicated by a bolt with an 'X' inside a triangle on the head?

NAS close tolerance bolt Signup and view all the answers

What fit is commonly used for the threads of aircraft bolts?

Class 3 fit Signup and view all the answers

What material is the cage of an Instrument Mounting nut made from?

Phosphor bronze Signup and view all the answers

What is the primary material used for the speed nut of an Instrument Mounting nut?

Brass Signup and view all the answers

How are Instrument Mounting nuts designed to prevent dropping behind the instrument panel?

Prevented by magnetism Signup and view all the answers

What does the length of a clevis bolt include?

Threads but not the head Signup and view all the answers

What characteristic does NOT pertain to Instrument Mounting nuts?

They are soldered in place Signup and view all the answers

Which characteristic is true for NAS close tolerance bolts?

They are used in high-stress applications Signup and view all the answers

Which option represents a likely material for a non-corrosive bolt in aviation?

Corrosion-resistant steel Signup and view all the answers

Which marking identifies an AN steel bolt on its head?

An 'x' Signup and view all the answers

How is a British close tolerance bolt identified?

A raised ring on the head Signup and view all the answers

What type of fastener is described as having an external sleeve and internally threaded?

A jo bolt Signup and view all the answers

What are studs with a larger thread size at one end called?

Stepped studs Signup and view all the answers

A bolt marked with a raised dash indicates what material type?

Corrosion Resistant Steel Signup and view all the answers

Which type of load can a dowel handle?

Shear Signup and view all the answers

What function do Dzus fasteners provide?

Quick release fasteners at inspection panels Signup and view all the answers

What does the abbreviation U.N.C signify in relation to aircraft bolts?

Unified National Coarse Signup and view all the answers

What is the purpose of capped nuts?

To prevent over-torquing as the bolt makes contact first Signup and view all the answers

Comparing bolt part number AN25C15 to AN25-15, which feature differentiates these parts?

Corrosion resistance Signup and view all the answers

Which marking indicates a close tolerance BSF bolt?

A raised disk on the head face Signup and view all the answers

In context of a BSF bolt, what represents the nominal length?

Representation A Signup and view all the answers

An aluminium alloy bolt can typically be identified by which characteristic?

Its color (dyed green) Signup and view all the answers

What diameter code letter corresponds to a British 3/8 inch diameter UNF bolt?

J Signup and view all the answers

Which identification is marked on an AN steel bolt?

X on head. Signup and view all the answers

Rivnuts were primarily designed for which of the following applications?

Securing rubber de-icing boots. Signup and view all the answers

What is a requirement for fork end fittings on control rod ends?

Bolts heads should be fitted upright. Signup and view all the answers

Which feature identifies the AN526 truss-head screw?

It is a pan-head screw. Signup and view all the answers

What is the primary purpose of capped nuts?

To stop leaks. Signup and view all the answers

A pin in a fork end fitting is primarily subjected to which type of loading?

Shear loading. Signup and view all the answers

Hylocks require which specific type of maintenance?

They are pre-lubricated. Signup and view all the answers

What does UNF stand for in the context of bolt specifications?

Unified fine. Signup and view all the answers

In a control cable fork end, a clevis bolt is loaded in which manner?

Only in shear. Signup and view all the answers

Which characteristic primarily differentiates Lockbolt and Hucbolt fasteners?

Method of installation. Signup and view all the answers

One advantage of the Hi-Lok type fasteners over older versions is that they can be installed using which tools?

Ordinary hand-tools. Signup and view all the answers

What do the markings on the head of a Dzus fastener indicate?

Diameter, type of head and length. Signup and view all the answers

How is the stud length of the Dzus turnlock fastener measured?

In hundredths of an inch. Signup and view all the answers

Threaded rivets, or Rivnuts, are commonly used to achieve what?

Attach components with screws. Signup and view all the answers

How can you identify aircraft bolts that feature a cross or asterisk marking?

They are standard steel bolts. Signup and view all the answers

Study Notes

Hi-Lok Fasteners

Hi-Loks are pre-lubricated to ease installation.
Hole for Hi-Loks should be drilled to create an interference fit, about 0.0015 inch.

Magnesium Castings

Surface treatment options:
- Anodizing
- Phosphating
- Correct answer: Chromating

UNF Bolt Specifications

Nominal length refers to the distance from under the head to the screw threads (plain shank).

Nyloc Nuts

Not suitable for use above 120 °C (250 °F).

Screw and Bolt Measurements

Nominal screw length includes the overall length of a countersunk screw and the non-threaded portion of a bolt.
Unified threads are identified by 2 or 3 rings on the head.

Bolt Identification

AN steel bolt marked with an 'x' on the head.
British close tolerance bolts identified by a raised ring on the head.
Capped nuts prevent leaks by providing an air/fluid tight seal.
Stepped studs have a larger thread size at one end.

Fastener Types and Loading

Dowel pins take shear loads.
Dzus fasteners allow for quick release at inspection panels.
Rivnuts initially used for securing rubber de-icing boots.
Fork end fittings on control rod ends must have bolt heads fitted upwards.

Threaded Fasteners

Capped nuts prevent overtightening by allowing the bolt to contact the captive part first.
Clevis bolts are loaded in shear.

Bolt Standard Identifications

AN526 truss-head screws are pan-head screws.
Capped nuts can be used for dry bolting or to stop leaks due to fitted metal caps.
Capped nuts are noted for preventing overtightening and ensuring a secure fit.

Markings and Classifications

AN corrosion-resistant steel bolts have a single dash on the head.
NAS close tolerance bolts marked with an 'X' inside a triangle on the head.
Aircraft bolts generally manufactured with a class 3 fit for threads.

Material Composition

Instrument Mounting nut components include:
- Cage made from phosphor bronze.
- Speed nut constructed from brass.
Non-magnetic characteristics prevent dropping behind the instrument panel.

General Terminology

UNF signifies "Unified National Fine".
Close tolerance BSF bolts characterized by a raised disc on the head.

Fastener Measurement Units

Dzus fastener stud lengths measured in hundredths of an inch.
Rivnuts used for attaching components with screws to sheet metal.

This comprehensive overview focuses on the key facts and context needed to understand the specifications and applications of various fasteners used in aviation maintenance and assembly.

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Description

Test your knowledge on various fasteners, including Hi-Loks, Nyloc nuts, and bolt specifications. This quiz covers essential information about fasteners' measurements, types, and load capacities. Perfect for engineering students and professionals looking to refresh their understanding of fastener applications.