FAA Flight Instructor Airplane (FIA)Aircraft Systems and InstrumentsMedium
A pilot flying at 16,000 feet MSL is using a diluter-demand oxygen system. What distinguishes this system from a continuous-flow oxygen system?
- AIt supplies a constant, unregulated flow of pure oxygen regardless of altitude or breathing rate
- BIt uses liquid oxygen instead of gaseous oxygen for greater efficiency
- CIt delivers 100% oxygen at all times but only to passengers, not crew
- DIt automatically blends cabin air with oxygen and delivers the mixture only during inhalation, adjusting the ratio with altitude
Show answer & explanationAnswer & explanation
Correct answer: D. It automatically blends cabin air with oxygen and delivers the mixture only during inhalation, adjusting the ratio with altitude
A diluter-demand system mixes cabin air with oxygen in proportions that vary with cabin altitude, delivering more oxygen and less dilution as altitude increases, and it flows only when the user inhales, making it far more efficient than a continuous-flow system.
Why the other options are wrong
- A. That describes a continuous-flow system, not diluter-demand.
- B. Diluter-demand systems typically use gaseous, not liquid, oxygen.
- C. Diluter-demand systems are typically used by crew for efficiency; passengers often use continuous-flow masks.
Diluter-Demand Oxygen System
An oxygen delivery system that mixes cabin air with oxygen in proportion to altitude and delivers the mixture only during inhalation.
- More economical than continuous-flow
- Automatically adjusts oxygen percentage with altitude
- Common in crew oxygen masks in pressurized aircraft
Memory trick: 'Demand it, dilute it—breathe only what you need'