How is the state of charge of a nickel-cadmium (Ni-Cad) battery determined?
By a measured discharge. The specific gravity of the electrolyte in a Ni-Cad battery does not change with the state of charge, so a hydrometer cannot be used.
What causes thermal runaway in a Ni-Cad battery?
Low internal resistance allows high current to flow, which generates heat. This heat further lowers the resistance, allowing even more current to flow, eventually destroying the battery.
How do you neutralize a spilled electrolyte from a lead-acid battery?
With a solution of bicarbonate of soda (baking soda) and water.
How do you neutralize a spilled electrolyte from a nickel-cadmium battery?
With a solution of boric acid or vinegar (an acid is needed to neutralize the potassium hydroxide base)
What is the relationship between the specific gravity of the electrolyte and the state of charge in a lead-acid battery?
The specific gravity decreases as the battery discharges. A fully charged reading is typically between 1.275 and 1.300.
Where can you find the specific dimensions and material required to fabricate a part?
In the detailed drawing.
What is the difference between “tolerance” and “allowance” on an aircraft drawing?
Tolerance: The difference between the extreme permissible dimensions (the “plus or minus” range).
Allowance: The prescribed difference between the dimensions of mating parts (the tightness or looseness of the fit).
What is a “station number” or “fuselage station”?
It is a location number measured in inches from the datum (zero point) of the aircraft. It is used to locate frames, bulkheads, and components.
Where is the revision block located on a blueprint, and what information does it contain?
It is usually located in the upper right-hand corner. It lists the changes made to the drawing, the date of the change, and the initials of the person who approved it.
How are rigid fluid lines sized
By their Outside Diameter (OD) in 1/16th inch increments.
How are flexible hoses sized?
By their Inside Diameter (ID) in 1/16th inch increments.
What is the difference between an AN fitting and an AC fitting?
AN (Army-Navy): Has a shoulder between the thread and the flare cone and uses a 37° flare. (Blue or Black).
AC (Air Corps): Has no shoulder and uses a 35° flare. (Gray or Yellow). Note: You cannot mix these.
What do the markings on the head of an AN standard steel bolt indicate?
They identify the material (standard steel, corrosion-resistant steel, aluminum) and usually consist of a cross, asterisk, or dashes.
What does a “lay line” on a flexible hose indicate?
It identifies the type of hose, date of manufacture, and pressure rating. If the line is spiraled, it indicates the hose was twisted during installation, which is not acceptable.
How can you identify a close-tolerance bolt?
By a triangle (or a triangle with an ‘X’) marked on the bolt head.
Where are self-locking nuts prohibited?
Where the nut and bolt are subject to rotation (e.g., a pulley).
In areas of high temperature (typically above 250°F for fiber-insert types).
What is the proper direction for installing a cotter pin?
The head of the cotter pin should fit into the slot of the nut, and the legs should be bent around the nut (one up over the stud, one down around the flat).
What is the standard number of twists per inch for safety wire
6 to 8 twists per inch.
What determines the correct grip length of a bolt?
The grip length (unthreaded portion) should be equal to the thickness of the material being bolted together.
Can a certificated Powerplant mechanic perform a major repair to a propeller?
No. Major repairs to propellers must be performed by an appropriately rated repair station.
Who is authorized to approve an aircraft for return to service after a Major Repair?
An Inspection Authorization (IA) holder, a Repair Station, or the FAA. A standard A&P cannot approve a Major Repair (they can only perform it)
What are the recent experience requirements for a mechanic?
To keep your certificate valid for use, you must have worked as a mechanic (or supervised/taught) for at least 6 months within the preceding 24 months.
What is the difference between an Airworthiness Directive (AD) and a Service Bulletin (SB)?
AD: Mandatory. It is a federal regulation used to correct an unsafe condition.
SB: Advisory (optional) for Part 91 operators, unless referenced in an AD
Which FAR Part governs the issuance of airman certificates (Mechanics)?
14 CFR Part 65.
