• It is a hard complicated solution to obtain natural crossing point between inline compressor and PO mode, • Inline compressor must always decelerate when the engine is accelerating, • Crossing maneuver must be done as close as possible to PO surge line, • At low boost pressure the compressor’s solicitations are less then at high boost pressure in maneuver time, • We get more airflow and/or boost pressure than necessary as a result of crossing maneuver if both compressors have the same speed. • Flat compressor’s flow characteristics could be an advantage.