Corrosion
For corrosion to form, three requirements must be met:
An electrical potential difference within the metal.
A conductive path between the two areas of potential difference.
Some form of electrolyte or fluid covering the two areas.
When do we use the cross filing technique
for general work, roughing down, squaring
What are the most common aircraft hardware standards you will encounter?
American Standards
Air force Navy (AN)
Military Standards (MS)
National Aerospace Standards (NAS).
European or French Standards
NATO Standardisation Agency (NSA).
Aircraft Manufacturers' Standards
Boeing Aircraft Corporation (BAC)
Fokker (FON)
Aeronautical Materials Specifications (AMS).
In Aviation what are castellated nuts used for?
used when the bolt is subjected to either shear or tensile loads and the nut is required to be held in place with a split pin
What is the most commonly used lockwire?
Stainless Steel
What is the best way to control corrosion?
Cleanliness of the surface is one of the best ways to control corrosion
When do we use draw filing technique?
This is used for finishing. Most surfaces, after being cross-filed flat, are draw filed until all the cross filing marks have disappeared
True or False: AN fasteners can be replaced by NAS and MS equivalent fasteners. NAS and MS standard hardware must not be replaced by AN standard hardware
True
What locking device is used when it is not convenient to use self-locking nuts or split pins on bolts
Lock Washer
where would I look to determine the correct type and diameter of lockwirs
Manufacturer AMM or SPM
Wet corrosion takes place in environments where the relative humidity exceeds?
60%
What must a centre punch mark must be?
Accurate in position
Large enough to take the chisel edge of the drill
What are the Unified Standard thread classifications
Unified National Coarse (UNC)
Unified National Fine (UNF)
Unified National Extra Fine (UNEF).
A clevis pin is secured with ?
a split pin or AN416 safety pin
What is copper lockwire used for?
to hold controls or switches into their normal operating position
What is an indication of mercury contamination on brass?
brass takes on a slippery, chromed
appearance
Pilot drills, i.e. a small drill used prior to a large one, are used for the following reasons
Large drills have such a large chisel edge that the centre-punch mark would have to be so large that it could not possibly be positioned accurately enough if it could be made large enough.
The chisel edge is inefficient in cutting and considerable pressure is needed to force it through the metal. The larger the drill the larger the chisel edge and, consequently, the greater the pressure needed. This pressure can be relieved by drilling a pilot hole
What are the 4 Classes of thread fit?
Class 1 is a loose fit
Class 2 is a free fit
Class 3 is a medium fit
Class 4 is a close fit.
Why were countersunk rivets developed?
streamline aerofoils and permit a smooth flow over an aircraft's wings or control surfaces
When lock wiring the lay of the wire must always be such as to?
resist any tendency of the locked part or parts to become loose
What is the most Anodic and most Cathodic metals
Anodic - Magnesium
Cathodic - Gold
What will happen to the drill Without a centre punch mark?
the drill will tend to wander creating a hole that is misshapen and in the wrong place or causing the drill to skid off and damage the surface.
What aircraft applications are machine screws used for?
for attaching fairings, inspection plates, fluid line clamps and other light structural parts
What are the most widely used methods of preventing fasteners coming loose in flight?
Safety wire, Split pins, Lock washers, Circlips
Special nuts such as: Self-locking nuts, Pal nuts, Jam nuts.
How many twists per inch should we be aiming for when we lockwire?
6-8