DEM (Starter) three positions switch question

[BaD CrC]

So I understand to Marche/Arrêt (M/A) function of the DEM switch, but in what case would you need to use the VENT (Ventilation) position of this switch?

Thanks.

[Mt5_Roie]

In case you screw up and need to restart the startup process. So try only waiting 5 seconds after the fuel pump starts. If you turn on the starter, it won't work. So you need to vent for about 10-15 seconds before trying again.

[msalama]

Hmmm... to purge the turbine combustion chamber of excessive fuel after a failed start perhaps? EDIT: schniped again I see ;)

[rrohde]

Nice! Was wondering about the same. Thanks! :)

[OldE24]

Vent would be just that Vent the engine of fuel/hotair from a hot start or doing a compressor wash on the engine.

 

If you had just shut the engine down and the T4 is above a temp you may VENT the engine to get the T4 down to an acceptable temperature to restart the engine with out the risk of a hot start further turbine compressor need to be cleaned for efficiency and corosion, it is normally done on a Hourly or calendar basis...such as 25 hours or 14 days for corrosion and such depending on the climate the aircraft is operated in.

 

i dont understand how not holding the boost pump on long enough would cause this but i have never worked around this engine?

Edited May 6, 2016 by OldE24

[BaD CrC]

Thanks Poly_Roie!