In a turboprop engine, the nozzle exhaust air velocity is the speed at which the exhaust gases exit the engine nozzle. Turboprop engines combine features of both jet engines and propeller engines, utilizing a gas turbine to drive a propeller. The nozzle in a turboprop engine plays a role in accelerating and directing the exhaust gases.
The formula essentially indicates that the product of the cross-sectional area and velocity is constant between the nozzle inlet and exit for an incompressible flow (assuming no losses). As the cross-sectional area decreases, the velocity must increase to maintain mass flow continuity.
The continuity equation is based on the principle of mass conservation, and Bernoulli’s equation expresses the conservation of energy.
The continuity equation is given by:
where:
-  and  are the cross-sectional areas at the nozzle entrance and exit, respectively,
-  and  are the velocities at the nozzle entrance and exit, respectively.
which gives
where,
- A1Â is the Area of Nozzle Inlet in m2
- A2Â is the Area of Nozzle Exhaust in m2
- V1Â is the Inlet air Velocity in m/s
- V2Â is the Exhaust Air Velocity in m/s