AME Aircraft Fuel Systems and Fire Protection 2 — Questions and Answers
Question 1: In an aircraft fire detection system, what does a 'thermal switch' type detector do?
- Detects smoke particles in the air
- Closes an electrical circuit when temperature exceeds a preset threshold (Correct answer)
- Measures continuous temperature and sends an analog signal
- Detects fuel vapor concentration in the engine nacelle
Correct answer: Closes an electrical circuit when temperature exceeds a preset threshold
A thermal switch is a simple on/off sensor that closes its electrical circuit when the ambient temperature reaches a predetermined value, triggering a fire warning.
Question 2: A 'continuous-loop' fire detector (such as Kidde or Fenwal) works by:
- Sampling nacelle air every few seconds
- Sensing a change in electrical resistance or capacitance along a sensing element due to heat (Correct answer)
- Detecting infrared signatures of flames using a photoelectric cell
- Measuring CO2 levels in the nacelle atmosphere
Correct answer: Sensing a change in electrical resistance or capacitance along a sensing element due to heat
Continuous-loop systems use a sensing element that changes its electrical properties when heated, allowing fire detection anywhere along the loop's length.
Question 3: What type of fire extinguishing agent is most commonly used in aircraft engine nacelle fire suppression systems?
- Water mist
- Halon 1301 or approved replacements such as HFC-227ea (Correct answer)
- Dry chemical powder
- Carbon dioxide (CO2)
Correct answer: Halon 1301 or approved replacements such as HFC-227ea
Halon 1301 and its approved replacements are standard for aircraft engine fire suppression due to their effectiveness, low toxicity, and minimal residue.
Question 4: An aircraft fuel vent system primarily prevents:
- Fuel contamination from water entry through vent openings
- Tank structural collapse or rupture from pressure differential during altitude changes (Correct answer)
- Fuel evaporation during long-term storage
- Fuel overflow during ground fueling operations
Correct answer: Tank structural collapse or rupture from pressure differential during altitude changes
Fuel vent systems equalize pressure between tanks and atmosphere, preventing the tank structure from being subjected to excessive differential pressure as altitude changes.
Question 5: What is the proper procedure before entering an aircraft fuel tank for internal inspection?
- Enter immediately after defueling to minimize exposure time
- Purge fuel vapors, verify safety with a gas detector, and follow confined space entry procedures (Correct answer)
- Use a portable fan to blow fresh air in for 5 minutes before entry
- Wear only a dust mask since fuel vapors are not toxic in small quantities
Correct answer: Purge fuel vapors, verify safety with a gas detector, and follow confined space entry procedures
Fuel tank entry requires complete vapor purging, confirmation with a calibrated gas detector that vapors are below explosive and toxic levels, and full confined space procedures.
Question 6: What is the purpose of a fuel tank bladder (fuel cell)?
- To increase the structural rigidity of the wing
- To provide a flexible, leak-resistant liner inside a structural fuel bay (Correct answer)
- To filter fuel as it exits the tank
- To measure fuel quantity using internal pressure sensors
Correct answer: To provide a flexible, leak-resistant liner inside a structural fuel bay
Fuel bladders are flexible, fuel-resistant bags installed inside structural cavities that provide leak-proof containment while conforming to the shape of the tank bay.
AME Aircraft Fuel Systems and Fire Protection 2
In an aircraft fire detection system, what does a 'thermal switch' type detector do?