Hi,
Posted originally by Aerotech
IN GENERAL after drift-down (twin, tri, or quad after engine shutdown) and in steady state and in stabilized flight, is N1 always > N2 ???(let's say especially in medium or high bypass engines, or even low bypass if it is possible).
The question posted above leads to me to wonder and think about the windmill itself:
-How the N1 & N2 are driven during windmill?
-Is it because of the airflow that drives the fan and the compressor? (in this case the fan and compressor drive the turbine which is the opposite when engine is operating)
OR
-The airflow drives the turbine which turns the fan and the compressor even though the airflow goes through the fan and the compressor first? which means there is no inversion of the role between the turbines and compressors during windmill or engine operation).
-What are the position of the VSV's (variable stator vanes) during windmill? Can this affect the N1 and N2?
Finally I am still wondering about the oil pressure (the lubrication problem) for a windmilling engine after drift-down, in steady state, and in stabilized flight since the trijet and quadjet are allowed to continue the flight after one engine shutdown. For example A340 engine can windmill up to 7 or 8 hours), is this regardless of the oil pressure?
Any toughts, comments, or feedback are very appreciated. Thank you.
Best regards