What are the two primary types of wood used in aircraft construction, and which is the standard?
Sitka Spruce is the standard. Douglas Fir is an acceptable substitute but is much heavier and harder to work
Name three wood defects that are cause for immediate rejection
Compression wood, dry rot (decay), and check/shakes/splits.
What is the most commonly used joint for splicing a wood aircraft spar?
A scarf joint.
What is the maximum grain deviation allowed in aircraft-grade wood?
1:15 (one inch of grain slope for every 15 inches of length).
How do you determine if a glued wood joint is sound?
By visual inspection for “squeeze out” and by performing a “feel” test or a light tapping test. If a joint fails, the wood fibers should ideally pull apart before the glue itself fails.
Define “Setback” in sheet metal bending
Setback is the distance the jaws of a brake must be set back from the mold line to allow for the bend radius. The formula is: Setback = K(R + T).
What is “Rivet Pitch”?
The distance between the centers of adjacent rivets in the same row.
What is the purpose of “Alclad” aluminum?
It consists of a pure aluminum coating rolled onto an aluminum alloy core to provide superior corrosion resistance.
What are the three types of oxy-acetylene flames
Neutral (preferred for most welding), Oxidizing (too much oxygen), and Carburizing (too much acetylene).
What is “Undercutting” in a weld?
A defect where the weld metal is thinner than the base metal at the edges of the weld bead, usually caused by excessive heat or improper torch angle.
How should oxygen and acetylene cylinders be stored?
Upright, secured, and separated (ideally by a fire-resistant wall) with their protective caps on
Why is a “tensiometer” used when rigging aircraft control cables?
To ensure the cables are at the correct tension for the ambient temperature, as the airframe expands and contracts.
What is the maximum number of threads that can be exposed outside a turnbuckle barrel?
No more than three threads on either side of the barrel.
What two units are used in a conventional shock strut (Oleo strut) to absorb shock?
Compressed air (or nitrogen) and hydraulic fluid (typically MIL-H-5606)
What does excessive wear in the center of an aircraft tire tread indicate?
Over-inflation. (Wear on the shoulders indicates under-inflation).
How do you distinguish between MIL-H-5606 and Skydrol hydraulic fluid?
MIL-H-5606 is mineral-based and red in color. Skydrol is phosphate-ester based and typically light purple/amber in color. They are not compatible and will destroy each other’s seals.
What is the difference between a “Continuous-Flow” oxygen system and a “Demand” oxygen system?
Continuous-flow provides a steady stream of oxygen (common for passengers), while a Demand system only provides oxygen when the user inhales (common for crew).
What component is responsible for controlling the cabin pressure in a pressurized aircraft?
The Outflow Valve. It regulates how much air is allowed to leak out of the cabin.
What are the three “Gimbal” errors or characteristics of a gyroscope?
Precession, Rigidity in Space, and Drift.
Which instruments are connected to the static system?
The Altimeter, Vertical Speed Indicator (VSI), and Airspeed Indicator.
What is “Magnetic Deviation” in a compass?
Error caused by local magnetic fields within the aircraft (electronics, engines, etc.). This is corrected using a “Compass Swing” and recorded on a correction card.
What is the maximum allowable leak rate for a static system test on an unpressurized aircraft?
loss of no more than 100 feet of altitude in one minute.
