Aviation Maintenance Technician Series Airframe textbook, Vol. 1 ASA Pages 138–168
Aviation Maintenance Technician Airframe Handbook FAA-H-8083-31 Vol. 1 FAA Chapter 5
Advisory Circular 43.13-1B FAA Pages 4-53–4-80
1. 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.
2. What are two types of electric resistance welding used in aircraft construction?
Spot welding and seam welding.
3. 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.
4. What determines the amount of heat that is put into a weld by an oxy-acetylene torch?
The size of the orifice in the torch tip.
5. 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.
6. 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.
7. Why must thick plates of metal be preheated before they are welded?
Preheating is a method of controlling the expansion and contraction of the metal that is being welded. Preheating minimizes the stresses that are caused when welding thick metal.
8. Why is it important that all traces of the welding flux be removed after a piece of aluminum or magnesium is welded?
Welding flux is corrosive and it must be removed to keep the metal from corroding.
9. What is the function of the inert gas that is used in TIG (GTA) and MIG (GMA) welding?
The inert gas forms a shield to keep oxygen away from the weld puddle so oxides cannot form and weaken the weld.
10. What is the difference between brazing and welding?
In brazing, the base metal is not melted, but is covered with a low-melting-point alloy. In welding, the base metal is melted.
11. What is used as the electrode in TIG (GTA) welding?
A small-diameter tungsten wire.
12. Is a heat-treated steel part normally repairable by welding?
No, welding destroys the heat treatment.
13. What is the function of the flux in brazing and soldering?
Flux covers the cleaned and heated metal to keep oxygen away from it. Oxides keep the solder or brazing material from adhering to the surface of the metal.
14. What kind of solder is recommended for soldering electrical wires?
60/40 resin-core solder.
15. What kind of flame should be used when gas welding aluminum?
A soft, neutral oxy-hydrogen flame is recommended.
16. What is an acceptable acetylene line pressure to use when welding with an oxyacetylene rig?
About five psi.
17. What kind of flame should be used when gas welding stainless steel?
A slightly carburizing flame.
18. How much should the bead penetrate the material when welding two pieces of steel with a butt weld?
The joint should have 100% penetration.
19. What is meant by a soft flame?
A soft flame is one that is made when the pressures of the gases are low enough that the flame does not make a noise and does not blow the puddle.
20. What must be done to an aircraft fuel tank before it can be repaired by welding?
The gas fumes must all be purged from the tank by running live steam through it for at least 30 minutes, by soaking it in hot water, or by filling it with nitrogen or carbon dioxide.
1. Demonstrate to the examiner the correct way to set up an oxy-acetylene welding rig, to light the torch, to adjust it to get a neutral flame, and to shut down the rig.
2. Demonstrate to the examiner the correct way to install, light, and adjust an oxy-acetylene cutting torch. Demonstrate the correct way to cut across a piece of steel.
3. Prepare two pieces of steel tubing, and weld them together to form a T.
4. Using examples of welds furnished by the examiner, select the ones that are not airworthy, and explain the reasons the welds are not acceptable.
5. Correctly set up a TIG (GTA) welding rig, and make a proper bead across a piece of steel.
6. Correctly prepare and join two pieces of steel by brazing.
7. Correctly prepare and solder a stranded copper wire into an electrical connector.
8. Demonstrate the correct use of tack welds and skip welding to prevent thin sheets of metal warping when they are being butt welded.
9. Demonstrate forehand and backhand welding and explain to the examiner the reason each type of welding is used.
10. Demonstrate the correct way to remove flux from a piece of aluminum that has been welded.
11. Make a paper template of a reinforcing patch that would be properly used to repair a longeron in a steel tube fuselage that has been dented at a cluster weld.