Float carburettor metering
Float-type carburettor parts:
- Float rests on fuel in the float chamber; its needle valve shuts off fuel as the level rises, opens as fuel is used (PHAK ch.7).
- Venturi throat low pressure forces fuel through the main jet into the airstream (PHAK ch.7).
- Throttle valve sits on the engine side of the discharge nozzle, controls mixture flow (PHAK ch.7).
- Mixture needle sets fuel flow to the discharge nozzle (PHAK ch.7).
A pressure-type carburettor discharges fuel downstream of the throttle, largely avoiding icing (PHAK ch.7).
Trap: the float holds the fuel level, not the throttle or the mixture needle.
References
- PHAK ch.7