Metallic Structures Flashcards
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 the stronger, the shear strength of the rivet, or the bearing strength of the metal sheet?
The two strengths should be close to each other, but the bearing strength of the sheet should be the 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.
What is the main function of a throatless shears in an aircraft sheet metal shop?
Throatless shears are used to cut mild carbon steel up to 10-gage, and stainless tell up to 12-gage. They can be used to cut irregular curves in the metal.
What is the purpose of a sight line when laying out sheet metal to be bent in a cornice brake?
The sight line allows the jaws of a cornice brake to be positioned so the bend made by the brake will start at the bend tangent line.
What kind of metal forming is done by a slip roll former?
Simple curves with a large radius.
What kind of metal forming is done by bumping?
Compound curves in sheet metal.
What must be done to the flanges of an angle for it to be curved?
The flanges must be stretched for a convex curve and shrunk for a concave curve.
What is meant by the bend allowance used in making a bend in a piece of sheet metal?
The amount of metal that is actually used in making the bend in a piece of sheet metal.
What determines the minimum bend radius that can be used with a piece of sheet metal?
The thickness of the material and its hardness.
What is meant by setback when bending a piece of sheet metal in a cornice brake?
Setback is the distance the jaws of the brake must be set back from the mold line to form the bend.
Why are the lightening holes in a sheet metal wing rib flanged?
They give the rib rigidity.
When hand-forming a piece of sheet metal that has a concave curve, should the forming be started in the center of the curve, or at its edges?
Start at the edges and work toward the center.
What is meant by a joggle in a piece of sheet metal?
A joggle is a small offset near the edge of a piece of sheet metal that allows the sheet to overlap another piece of metal.
When drilling stainless steel, should the drill be turned fast or slow?
It should be turned slowly.
What is the minimum edge distance allowed when installing rivets in a piece of aircraft sheet metal structure?
Two times the diameter of the rivet.
What is the recommended transverse pitch to use when making a riveted two-row splice in a piece of sheet metal?
Three-fourths of the pitch of the rivets in the rows.
Why should aluminum alloy rivets be driven with as few blows as is practical?
Excessive hammering will work-harden the rivets and make them difficult to drive.
What determines whether a piece of sheet metal should be dimpled or countersunk when installing flush rivets?
The thickness of the sheet. Countersinking should be done only when the thickness of the sheet is greater than the thickness of the rivet head.
What type of metal should be hot-dimpled?
7075-T6, 2024-T81 aluminum alloys, and magnesium alloys should be hot-dimpled.
Why is TIG (GTA) welding preferred over oxyacetylene welding for building and repairing welded steel tube aircraft structure?
The heat is concentrated in the weld and does not cause as much distortion as gas welding.
Why is it important that the pressure of the gas in an acetylene cylinder be kept low?
Acetylene gas becomes unstable when it is kept under pressure of more than about 15 psi.
What is the difference in the appearance of an oxidizing flame, a neutral flame, and a reducing flame produced by an oxy-acetylene torch?
An oxidizing flame has a pointed inner cone, and the torch makes a hissing noise. A neutral flame has a rounded inner cone, and there is no feather around the inner cone. A reducing flame has a definite feather around the inner cone.
What is meant by tack welding?
Tack welding is the use of small welded spots to hold the material together until the final bead is run.
