Narrative:

When we received the aircraft; the previous crew had written up the #2 AC generator. Maintenance came and deferred the generator. Per the MEL operations instructions; we were to keep the APU running for the entire flight. The captain and I discussed this as part of our pre-departure briefing. When tower cleared us to position and hold; I ran the takeoff checklist and habitually turned off the APU. I realized my mistake and informed the captain. We notified the tower that we would need to exit the runway and get back in line to restart the APU. As we taxied back to the runway; we restarted the APU. As we taxied into position the 2nd time; the EFIS comp mon caution message briefly appeared and then cleared. We verified the runway heading on both pfd's and they were correct. ATC cleared us for takeoff (RNAV) and we began the takeoff roll. At rotation and wheels off; both pfd's displayed the flight director red flag. I continued to hand fly the aircraft and the captain immediately requested a heading from ATC. We were assigned a heading. We decided to turn on the autopilot to see if that would return our flight director. The autopilot was engaged and it was following the correct heading and climbing at the assigned speed of 250 KTS. The flight director did not display on either pfd's. After approximately 5 minutes; the flight director flags disappeared and the flight director displayed correctly. The flight continued without further incident. I believe the cause of this problem was the power transfer that occurred during the shutdown and restart of the APU prior to takeoff. After our flight director was restored en-route; we checked the FMS and saw that the perf init and initialize page data were missing. This typically happens when the AC power is disrupted to the aircraft. Since the APU was providing the AC source to bus 2 when it was shutdown; a transfer to AC # 1 occurred. Once the APU was restarted; a transfer occurred again when the APU generator started supplying power to bus 2. This incident illustrates why it is important to slow down when completing checklists and flows during abnormal operations to ensure they are completed properly. I shutdown the APU due to 'muscle memory' during the takeoff checklist even though we had discussed the MEL procedures for the deferred AC generator during the pre-departure briefing.

Related reports:

Google
 

Original NASA ASRS Text

Title: While taking the runway; a CRJ200 First Officer mistakenly shut down the APU which was needed because of a MEL'ed #2 engine generator but because navigation equipment was on #2 Bus when the APU was again started and put on Bus the equipment was confused by the power transfers so that the FMS and compass system did not display correctly on takeoff.

Narrative: When we received the aircraft; the previous crew had written up the #2 AC Generator. Maintenance came and deferred the generator. Per the MEL operations instructions; we were to keep the APU running for the entire flight. The Captain and I discussed this as part of our pre-departure briefing. When Tower cleared us to position and hold; I ran the Takeoff Checklist and habitually turned off the APU. I realized my mistake and informed the Captain. We notified the Tower that we would need to exit the runway and get back in line to restart the APU. As we taxied back to the runway; we restarted the APU. As we taxied into position the 2nd time; the EFIS COMP MON caution message briefly appeared and then cleared. We verified the runway heading on both PFD's and they were correct. ATC cleared us for takeoff (RNAV) and we began the takeoff roll. At rotation and wheels off; both PFD's displayed the flight director red flag. I continued to hand fly the aircraft and the Captain immediately requested a heading from ATC. We were assigned a heading. We decided to turn on the autopilot to see if that would return our flight director. The autopilot was engaged and it was following the correct heading and climbing at the assigned speed of 250 KTS. The flight director did not display on either PFD's. After approximately 5 minutes; the flight director flags disappeared and the flight director displayed correctly. The flight continued without further incident. I believe the cause of this problem was the power transfer that occurred during the shutdown and restart of the APU prior to takeoff. After our flight director was restored en-route; we checked the FMS and saw that the PERF INIT and Initialize page data were missing. This typically happens when the AC power is disrupted to the aircraft. Since the APU was providing the AC source to Bus 2 when it was shutdown; a transfer to AC # 1 occurred. Once the APU was restarted; a transfer occurred again when the APU generator started supplying power to Bus 2. This incident illustrates why it is important to slow down when completing checklists and flows during abnormal operations to ensure they are completed properly. I shutdown the APU due to 'muscle memory' during the Takeoff Checklist even though we had discussed the MEL procedures for the deferred AC Generator during the pre-departure briefing.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.