Wind-powered backup generator. /"Emergency mill"


Most common question about the airplain.

What is this?

Wind-powered backup generator. /"Emergency mill


The reserve unit consists of a mechanically speed-regulated ram air turbine and an alternating current generator.


The unit folds out hydraulically.


Minimum speed for safe operation is 300 km/h.


When a fault has occurred in the electrical power supply from the aircraft generator, the reserve unit is automatically deployed on impulse from the control panel and begins to supply voltage to the grid.


Correct voltage is obtained, depending on the speed of the aircraft, 1-6 seconds after the reserve unit has reached the extended position.

Flying with the reserve unit extended at speeds above 700 km/h means the risk of blade breakage.


The spare unit folds out automatically when the nose wheel springs in during landing, and folds in when the landing gear folds in after take-off. However, connection to the grid only takes place if a fault occurs in the electricity supply.


The aircraft generator is a 3-phase oil-cooled alternator providing 200V, 400 Hz alternating voltage and providing an output of 60 kVA. The generator is driven by the aircraft motor via a constant speed gearbox, whose built-in mechanical speed regulator keeps the generator speed constant at varying engine speed and load.