Jeppesen Oral- Chapter 2 ( Sheet Metal Structures) Flashcards
(39 cards)
What is the major type of damage to aluminum structures that is caused by exposure to weather?
Corrosion
Name several methods for forming sheet metal?
Bending, folding, stretching, shrinking, bumping, crimping
What are the dimensions of a properly formed rivet?
Head should be 1.5x the shank diameter (width)
Head should be .5x shank diameter in height
What happens to the stem of a self-plugging (friction lock), rivet, when the rivet is installed?
The stem is pulled until it snaps off and the remaining projecting part is trimmed flush with the head
Name at leas three types of self-plugging mechanical rivets.
Cherry Maxx, CherryLock, Olympic-Locs, Huck
What is the difference between the ticks required to pull a Cherrylock rivet and a cherrymax rivet?
CherryMax only requires one tool for all sizes
Cherrylock, requires different tools for different sizes and heads
Which of the 5 stresses is the most common cause of rivet failure?
Shear
If a 20 24 rivet must be replaces with a 21 17 rivet, how do you determine the size to be used?
For a 5/32” diameter or smaller, use the next larger size 2117 rivet (assuming the edge distance and pitch requirements are met)
Describe the process for determing the total length of a solid rivet for a particular installation.
Add the grip length (thickness of the material being joined together) plus 1.5x diamter
What is the minimum edge distance and spacing that should be used for a single row of protruding head rivets?
Not less than two rivet diameters from the edge
Not less than three diameters apart
How can a mechanic determine whether the countersunk for a flush rivet should be dimpled or drilled?
By the thickness of the top sheet
What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals?
Hot dimpling to preheat and soften metal
What type of damage can occur when using a rivet set that does not properly fit the rivet?
If the radius is too small, the rivet might become damaged
If the set radius is too large it may damage the sheet metal
Why is it important to use the proper size and weight bucking bar when riveting sheet metal?
Bucking bar too big, difficult to control and cause damage
Too light, will not properly upset the rivet prior to work hardening
What procedures should be followed to properly remove a solid shank rivet?
Center punch the rivet and then drill a hole to the base of the rivet head with the same size or one smaller
Use a pin punch to tip off the head and drive out the rest of the shank
What are the two special calculations that must be made when bending sheet metal?
Bend allowance and setback
What are the factors that must be considered in order to determine setback?
Thickness of the material and bend radius
What is done to a corner where two bends intersect to prevent cracking?
Relief holes are drilled into the corner
What are the two reasons for installing a lighting hole n sheet metal wing ribs?
Reduces weight, increase stiffness
Describe a joggle and explain it’s function
Offset formed at an intersection of two or more sheet
Allows multiple sheets of metal to be stacked flat against each other
When preparing an all-metal aircraft, how do you determine what metals should be used?
Use the same metal and thickness
What are three requirements for a repair to a piece of sheet metal aircraft structure?
The repair must restore the lost strength and rigidity, and it must not change the aerodynamic shape of the part.
When making a riveted repair to an aircraft sheet metal structure, which should be stronger, the shear strength of the rivet, or the nearing strength of the metal sheet?
The two strengths should be close to each other, but the bearing strength should be greater.
What type of device is a Cleco fastener?
A patented fastener that is inserted in the rivet holes and is used to hold two pieces of sheet metal together until they can be riveted.
