Hi all, The APU bleed normally supplies only the left pneumatic duct. If you are going to start right engine first as most of real world operations, you must set the isolation valve switch to OPEN before turning the start switch of right engine to GRD. So if you forget to open the isolation valve before attempting to start the right engine, there should be no air pressure to open the starter valve or to rotate the N2 spool. The NGX actually simulates this system correctly except for the starter nice roaring sound. This nice roar actually plays even when there is no N2 rotation as described above. Please advise if any one has experienced this condition. I will include here brief steps to reproduce the problem from cold and dark state: 1. Turn up the volume at your system, and you better use a high quality headset so that you can clearly hear the very nice realistic roaring of the starter. 2. Battery switch ON. 3. Standby Power switch AUTO. 4. Bus Transfer switch AUTO. 5. APU switch START then ON. 6. After APU GEN OFF BUS light comes on, both APU GEN switches ON. 7. APU bleed switch ON. 8. Make sure ISOLATION VALVE switch is in CLOSE position. 9. Set right engine staring switch to GRD. You now should be seeing no N2 rotation, but unfortunately starter roaring sound plays! Please give me your feedback before I file a ticket.