60 Questions
What happens to the strength of the metal affected by exfoliation corrosion?
It greatly decreases
What is the recommended remedy when exfoliation corrosion is evident on the metal surface?
Complete removal of the affected sections
Where do microbiological growths in aircraft fuel tanks primarily live and feed?
In the water collected in the tanks
What type of organic bodies are microbes found in aircraft fuel tanks?
Fungi
What do microbes in aircraft fuel tanks produce that promotes corrosion?
A scum
What flight conditions contribute to water condensation in aircraft fuel tanks?
High-altitude, low-temperature
What type of corrosion is described as an extreme case of intergranular corrosion?
Exfoliation corrosion
In fretting corrosion, what destroys the protective film that develops on surfaces?
Continued rubbing action
What visual indication can appear around rivets in skin if fretting corrosion is occurring?
Dark deposits around rivet heads
Which type of materials are most susceptible to exfoliation corrosion?
Extruded materials
Why must rivets showing signs of fretting corrosion be replaced as soon as possible?
To prevent further damage to the parts
What characteristic makes exfoliation corrosion distinct from other types of corrosion?
Causes the material to separate or delaminate along grain boundaries
What happens if prompt treatment is not provided when white, puffy areas are discovered on a structure?
The corrosion will penetrate through the structure
In what type of environment does the natural oxide-carbonate film on magnesium alloys not provide sufficient corrosion protection?
Mild environment
What is a consequence of titanium absorbing gases at high temperatures from the surrounding air?
It becomes very brittle
What effect can chlorides and some chlorinated solvents have on certain titanium alloys?
Induces stress corrosion cracking
What does the oxide film that forms on titanium surfaces provide?
Protective barrier against corrosion
Why is electrical insulation necessary between titanium and other metals?
To prevent galvanic corrosion
What is a common application of pure nickel?
Electroless coating
How does the stress corrosion resistance of stainless steel alloys change with increasing nickel content?
Increases
In what areas are nickel-based alloys commonly used?
High-temperature areas like engines
What is a common application of copper and copper-based alloys in avionics systems?
Contacts, springs, leads
What is a common sign of copper corrosion on a part?
Accumulation of blue-green corrosion products
What can lead to flaking of the nickel coating?
Pitting corrosion of the nickel
Why is tarnish removal critical on gold components?
To prevent corrosion on the less noble metals underneath
What is the result of gold corrosion over silver or copper in thin layers?
Darkening of the silver or blue-green deposits on the copper
What is 'Purple plague' in the context of gold-aluminium compounds?
A brittle gold-aluminium compound formed when bonding gold to aluminium
Which metal offers the best combination of solderability and corrosion resistance?
Tin
What tends to grow 'whiskers' on tin-plated wire and other plated applications?
Tin
Why is corrosion accelerated over less noble metals when gold plated over them in thin layers?
Due to the formation of darkening deposits
What determines whether a power header or a hand beading tool is used to accomplish beading of a tube?
The diameter and wall thickness of the tube
What is the purpose of the inner liner in a flexible hose used in aircraft fluid systems?
To carry the fluid and offer least resistance to flow
Why does the inner liner of a flexible hose need to be chemically compatible with the material being carried?
To ensure it does not corrode or degrade
What is the main function of an outer cover in the construction of a flexible hose?
To protect from physical damage
What is essential for the inner liner of a flexible hose in terms of porosity?
It must have minimal porosity
Why is flexibility throughout an entire range of operating temperatures essential for the inner liner of a flexible hose?
To allow smooth flow of fluid
What is the angle of the external flare in AN fittings?
37°
What material are AN steel fittings colored as for identification purposes?
Black
What type of tube is used with flareless fittings?
Straight-cut tube
Which metal base alloys are flared-tube fittings made of?
Aluminium and steel
What color are AN aluminium fittings for identification?
Blue
How many parts does a flared-tube fitting consist of?
Three parts
Which synthetic compound is best suited for carrying phosphate ester-base hydraulic fluids?
Butyl
Which synthetic rubber is more suitable for carrying petroleum products than neoprene?
Buna-N
Which synthetic compound breaks down if used with petroleum products?
Butyl
Which synthetic compound has an extremely broad operating temperature range and offers minimum resistance to fluid flow?
Teflon
Which synthetic rubber is used with petroleum-based fluids and is abrasion resistant?
Neoprene
Which compound has a unique chemical structure that leads to less volumetric expansion than rubber?
Teflon
What is the purpose of O-rings in some applications of banjo fittings?
To replace aluminium gaskets
What feature allows the banjo to rotate before the bolt is torqued during installation?
Positive visual engagement
In which fluid systems are quick-disconnect couplings commonly used?
Fuel, hydraulic, and water/waste servicing adaptors
What is the primary function of the sliding collar in some quick-disconnect couplings?
Snap-lock attachment
What type of lines are typically joined using rubber hoses and screw-type hose clamps?
Large-diameter lines carrying low-pressure fluids
What is the advantage of having a built-in shutoff valve in quick-disconnect couplings?
No-spill connection
What is the purpose of the outer cover in a hose?
To provide protection from physical damage
What information can be found on the lay line of an aircraft flexible hose's outer cover?
The MIL-SPEC number, hose size, manufacturer's details, and manufacturing date
Why are reinforcement layers essential in hoses?
To reduce the pressure-induced dimensional changes in the hose
What is generally marked on the outer cover of an aircraft flexible hose?
A lay line with identification information
How can one determine if a hose is twisted during installation?
By observing the lay line on the outer cover
What materials are commonly used for reinforcement layers in hoses?
Cotton, rayon, polyester fabric, and steel wire braid
Learn about fretting corrosion in materials and hardware from the training materials for CASA Part 66. Understand how surfaces erode when they fit tightly together but can move relative to each other, leading to the destruction of the protective film due to rubbing action.
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