AM Blueprint Reading & Interpretation 3 — Questions and Answers
Question 1: On an aircraft wiring diagram, what does a circle with an 'X' inside typically represent?
- A junction box
- A ground connection
- A lamp or light bulb (Correct answer)
- A circuit breaker
Correct answer: A lamp or light bulb
In aircraft wiring diagrams, a circle with an X inside is the standard symbol for a lamp or light bulb.
Question 2: What is the meaning of the abbreviation 'REF' placed next to a dimension on an engineering drawing?
- The dimension requires special inspection
- The dimension is for reference only and does not control manufacturing (Correct answer)
- The dimension references a separate drawing
- The dimension has been revised
Correct answer: The dimension is for reference only and does not control manufacturing
A REF dimension is provided for information only; it is not used to inspect the part or control manufacturing tolerances.
Question 3: In aircraft blueprint reading, what does the term 'DATUM' refer to?
- The maximum allowable weight of a component
- A fixed reference plane or point from which measurements are taken (Correct answer)
- The date the drawing was originally created
- The required surface finish specification
Correct answer: A fixed reference plane or point from which measurements are taken
A datum is an exact theoretical reference plane, axis, or point established on a drawing from which all feature locations are measured.
Question 4: An aircraft hydraulic schematic shows a triangle pointing toward a line. What does this symbol represent?
- A filter or strainer
- A check valve allowing flow in one direction only (Correct answer)
- A pressure relief valve
- A hydraulic pump
Correct answer: A check valve allowing flow in one direction only
A solid triangle (arrowhead) pointing in the direction of permitted flow represents a check valve in hydraulic and pneumatic schematics.
Question 5: What does 'CRES' stand for in aircraft material callouts on drawings?
- Corrosion Resistant Electronic System
- Corrosion Resistant Steel (Correct answer)
- Chromate Resistant External Surface
- Compression Resistant Elastic Substrate
Correct answer: Corrosion Resistant Steel
CRES is the abbreviation for Corrosion Resistant Steel, commonly used in aircraft structural and fluid system components.
Question 6: On a multi-view drawing, what is the standard arrangement of views in third-angle projection (used in the US)?
- Front view center, top view below, right side view to the left
- Front view center, top view above, right side view to the right (Correct answer)
- Front view center, top view above, right side view to the left
- Front view center, top view below, right side view to the right
Correct answer: Front view center, top view above, right side view to the right
In US third-angle projection, the top view appears above the front view and the right side view appears to the right of the front view.
Question 7: A drawing callout reads '4X Ø.250 ±.005'. What does this specify?
- A single hole with a diameter tolerance between .245 and .255 inches
- Four holes each with a diameter of .250 inches with a tolerance of ±.005 inches (Correct answer)
- A 4-inch diameter hole with a .250 tolerance
- Four features with a surface finish of 250 microinches
Correct answer: Four holes each with a diameter of .250 inches with a tolerance of ±.005 inches
The '4X' multiplier means the feature is repeated four times; Ø.250 ±.005 specifies a diameter of .245 to .255 inches for each hole.
AM Blueprint Reading & Interpretation 3
On an aircraft wiring diagram, what does a circle with an 'X' inside typically represent?