Aircraft fasteners

Types of aircraft fasteners

Helical Inserts

Helical inserts are also called helical coils or helicals. These are wire-threaded inserts that are coiled into a helix shape and inserted into drilled holes in metals. A matching screw or bolt is threaded into the coil so that the coil remains in the host material while the bolt or screw rotates in the coil. They are used on fatigued or worn-tapped components, extending the life of mount systems.

Tapered Inserts

A tapered insert is an internal thread system with an outer cylindrical thread that allows it to be screwed into tapered holes. Besides the tapered hole, the other mounting method is similar to a helical insert. The standard screw or bolt is rotated into the insert to secure it in the component.

The tapered design enables a reinforced connection, so tapered inserts aren't prone to loosening and can be used in dynamic mount systems. They have mostly been used in military aircraft components and other critical applications.

Rivets

Aircraft rivets have been a popular fastening system in the aerospace industry for durability and reliability. Rivets are permanent fasteners made from metal alloys and can be installed by hand, using an automatic riveting machine, or a pneumatic riveter. Fixing a rivet requires hammering or compressing it to deform the pointed end and form a head that holds the rivet in place while the shaft is embedded in the host material.

Screws

Machine screws and other screws are popular as they can be easily installed and removed. Aviation screws are uniquely developed while considering the restrictions and duty of flying applications. Common types of screws include countersunk, dome, and carriage screws.

Locking Fasteners

Locking fasteners have been perfect for security-enhanced applications. Such fasteners are designed not to loosen under vibrations and are mostly used in dynamic mount systems like engines and rotors. Lock-nuts, wedge-lock fasteners, and friction-based locking bolts are all examples.

Studs and Nuts

Studs and nuts are conventionally applied in areas where disassembly for maintenance is often done. A stud is a part that has threads on both ends or one end only with a shank in between. The end that has threads is fixed into one component, while the nut that is threaded onto the stud fixes another component on the opposite end.

Durability & Materials of aircraft fasteners

What Parts Constitute Durability

The durability of fasteners is concerned with the key following aspects:

• Fatigue Resistance: Fasteners experience numerous cycles of load variations, especially in aircraft operating under different flight conditions. Durable fasteners are manufactured to resist fatigue, hence preventing formation cracks or warping over time.
• Corrosion Resistance: Due to the constant exposure of aircraft to harsh weather conditions, fasteners are produced with corrosion-resistant elements to reduce the probability of weakening or failure that may be brought about by rust or other forms of corrosion. Durable materials include stainless steel, titanium, and nickel-based alloys.
• Abrasion and Wear Resistance: Fasteners need to be fitted with tolerances and surface finishes fitted to resist wear from mechanical interactions like rubbing and abrasive disassembly/reassembly.
• Thermal Resistance: Aircraft fasteners are required to perform under extreme temperature variations in the atmosphere, during takeoff, landing, and incesant operation of engines. The materials used must possess the ability to withstand thermal expansion and contraction without compromising structural integrity.

Materials Used to Make the Fasteners

Various materials are used for the durable construction of aircraft fasteners:

• Titanium Alloys: Titanium alloys have a high strength to weight ratio. They possess good fatigue and corrosion resistance properties. These properties make titanium fasteners ideal for critical safety and high-performance aircraft zones.
• Stainless Steel: Stainless steel is common in the manufacture of fixed-wing aircraft and is also widely used for fasteners due to its excellent rust resistance. Aviation screws and rivets are made of stainless steel because of its strength, durability, and ability to resist tempering.
• Aluminum Alloys: Although not as strong as steel, these alloys have a good strength to weight ratio. They are lighter and therefore have been used in making fasteners for light aircraft. They are also used in non-structural applications where resistance to corrosion is required.
• Nickel Alloys: Nickel alloys are commonly used, particularly in high-temperature environments, like engine components. They have excellent strength, corrosion resistance, and thermal properties, thus fitting for extreme condition fasteners.
• Carbon Steel: Carbon steel fasteners are economical and are typically used in non-critical applications. They are comparatively weaker and more vulnerable to corrosion. Often, they are coated with zinc or chromate for enhanced protection against corrosion.

Scenarios of aircraft fasteners

• Riveted Joints in Airliner Fuselage

  An airline company has operated a fleet of aluminum-bodied airliners for over a decade. The aircraft fuselages have riveted joints, and durability and corrosion resistance have come to distinguish the fasteners used in these joints over the years.

  As a result of periodic inspection, no sign of fatigue was found in the rivets, and corrosion had not affected the fasteners since the fleet was coated with zinc. The aircraft was ascertained to still be safe and airworthy after attending to it with minimal maintenance duties after years of service.

• Engine Mounts on Military Fighter Jets

  Military fighter jets operated under extreme conditions are required to have fasteners with superior locking properties and resistance to vibrations. Wedge-lock fasteners were applied here as they had superior hold under the intense vibrations produced during combat maneuvers. Maintenance records indicated the fasteners had exceptional wear resistance and required minimal retightening between routine checks.

• Used on Racing Drone Frame

  Racing drones need fasteners manufactured with lightweight yet very strong materials like titanium as they are affected by extreme aerodynamic forces in racing. A team found a combination of titanium screws and carbon fiber reinforced polymer washers offered great strength and flexibility to the drone frame under impact and strain. The fasteners had excellent fatigue resistance after multiple races.

• High-Temperature Fasteners on Spacecraft

  Fasteners in spacecraft are exposed to outer space and are built from bona fide materials like nickel alloys. A team developing a re-entry vehicle was concerned about thermal expansion and asked for fasteners that would not destabilize during the vehicle re-entry sequence. They settled on hex-headed screws made from Inconel that withstood over 1000 °C with no deformation.

• Fastener Replacement in Vintage Warbird

  A historical group owns a 1940s vintage warbird with rivets that had to be replaced as the fuselage fasteners showed signs of fatigue after years of scrutiny. The group used aviation-grade aluminum rivets resistant to corrosion and with long fatigue life. Their tensile strength matched that of the historical material, therefore not weakening the structure and at the same time assisting in preserving the historical value of the aircraft.

How To Choose the aircraft fasteners

The following factors help in choosing the right aircraft fasteners:

• Material

  The fastener material should possess strength, durability, and corrosion resistance. Stainless steel and titanium are ideal because of their strength, resistance to fatigue and corrosion, and ability to withstand extreme temperature. Such materials aside from being lightweight contribute to not overwhelming the aircraft and still keeping it secure.

• Type of Fastener

  Aircraft fasteners include: rivets, screws, helical inserts, tapered inserts, fastener studs, nuts, locking fasteners, etc, each befitting specific applications. Rivets provide permanent and robust fastening suitable for fuselage and wing structures. Screws allow removability and fit for access panels or interiors. Picked-in locking fasteners for critical security applications.

• Standards and Certification

  Aircraft fasteners must abide by set industry standards and have certification from relevant authorities like the FAA and EASA. Such adherence guarantees that the fasteners have been put through rigorous testing for safety and performance. Using only certified fasteners here prevents legal issues and ensures the aircraft meets airworthiness requirements.

• Fastener Compatibility

  To ensure proper functioning, fasteners should be compatible with the materials they interact with and the load they carry. Using the right size fastener goes against penetration or stripping of the fastener, hence preserving integrity. Moreover, fasteners used should be compatible with other fastener systems, particularly where disassembly is often undertaken for maintenance purposes.

• Maintenance and Inspection

  Fasteners that ease maintenance and inspection should be considered. Certain screws have safety lock provisions that enable easy access with minimal intrusion. Corrosion-resistant coatings prolong the life of aircraft fasteners without the need for frequent inspections and maintenance.

Q & A

How does one maintain aircraft fasteners?

This is done by frequently inspecting them for corrosion, fatigue, and wear and tear. It is performed by cleaning fasteners to remove debris and check for signs of loosening while using torque wrenches to attain the proper tightness during the reassembly of components.

What role do fasteners play in aircraft performance?

Fasteners provide an aire free structural integrity that affects performance by maintaining the shape of an aircraft under variable loads, reducing drag. It ensures the safe operation of the elements and thus contributes towards proper functioning and system separation during flight.

Can corrosion-resistant coatings be applied to all aircraft fasteners?

Corrosion-resistant coatings may not be applied to all fasteners as some may be undergoing the influence of extreme heat where the coatings will degrade or have an adverse effect on the fastener. Anti-corrosion coatings are applied to nearly all fasteners that are exposed to environmental elements.

What is the significance of using certified fasteners?

These certified fasteners have been rigorously tested for safety, performance, and they comply with industry standards. They are fit for critical applications because they meet regulated requirements. They prevent failures during operations and contribute to overall aircraft safety.