Small gas

Small gas - the minimum stable mode of the aircraft engine. The term " idle " in this case is not used, since the aircraft engine , as a rule, is always associated with the propeller: a turbojet with a small gas always creates a slight thrust, a piston, turboshaft or turboprop engine is usually rigidly connected with a screw (except for many piston helicopters , some turboprop engines) and also always, during operation, transmit power to the propeller for its rotation.

For many engines two small gas regimes are regulated:

• ground small gas (ZMG) - the minimum possible mode of operation of the engine, not taking into account the effect of the engine on the aerodynamics of the aircraft - in this mode, the screw may fall below the equilibrium or negative thrust will appear in flight (due to the low speed / blades, as a consequence, at negative angles of attack);

• Flight Small Gas (SGP) - the minimum mode in which the engine ensures the operation of an aircraft or propeller in design modes - does not create negative thrust and provides an equilibrium (working) propeller speed.

On an airplane in flight, it is possible to use ZMG to accelerate the reduction - in this case, the engine fan or screw switches to autorotation or windmill mode and creates negative thrust, since the kinetic energy of the flow goes to maintain engine speed.