FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesMedium
A turbine engine fuel nozzle contains two separate internal flow passages that both discharge fuel from the same tip: one supplies fuel during starting and low power, and the other adds fuel flow as power is increased. This nozzle design is called a
- AAir-blast nozzle
- BSimplex nozzle
- CVaporizing nozzle
- DDuplex nozzle
Show answer & explanationAnswer & explanation
Correct answer: D. Duplex nozzle
A duplex fuel nozzle has a primary (low-flow) manifold used for starting and idle, and a secondary (main) manifold that adds fuel as power increases, improving spray pattern and combustion efficiency across the power range. A simplex nozzle has only a single flow passage and produces poor atomization at low flows.
Why the other options are wrong
- A. Air-blast nozzles use compressor discharge air to atomize fuel, a different atomization method entirely.
- B. A simplex nozzle has only one flow passage, giving poor atomization at idle power.
- C. Vaporizing nozzles mix fuel with air before injection but do not use separate primary/secondary manifolds.
Duplex Fuel Nozzle
A fuel nozzle with primary and secondary flow passages that improve fuel atomization across a wide range of engine power settings.
- Primary manifold used for starting/low power
- Secondary manifold adds flow at higher power
- Requires a flow divider valve to route fuel
Memory trick: 'DUPLEX = DUAL flow' for good spray at every power.