An EMB145 compass system heading was aligned with the departure runway but after takeoff disagreed by more than 40 degrees with an erroneous wind read out of 143 KTS. After a second Directional Gyro reset the system slaved correctly. The crew was also distracted by a HYD LOW QTY 1 ECAM alert.
Synopsis
An EMB145 compass system heading was aligned with the departure runway but after takeoff disagreed by more than 40 degrees with an erroneous wind read out of 143 KTS. After a second Directional Gyro reset the system slaved correctly. The crew was also distracted by a HYD LOW QTY 1 ECAM alert.
Narrative
On takeoff departure we were given a heading of 040. After rotation and through 500 FT we turned to a 040 heading and noticed that the PFD and MFD on the Captain and First Officer side were showing a 140 KTS wind. Shortly there after ATC Tower asked us to verify heading. We stated 040 heading because all PFD's and MFD's indications showed we were on a 040 heading. ATC advised us they were showing a 350 heading. We verified with standby compass and saw the error. After correcting our course we tried to recycle our DG. After second attempt at cycling between DG mode and Slaved modes both PFD's and MFD's reset to their correct positions; and we had no further problems. On the runway before starting our takeoff roll everything appeared fine. Both PFD's and MFD's showed the correct runway heading and winds. It wasn't until after we lifted off and started our turn we noticed the problems. We aren't really sure what caused this anomaly. To the best of my knowledge it was just a glitch in the computer system. I have seen the wind error before on the MFD and PFD; but not on both sides at the same time. Maintenance was notified upon landing and think it may have been a glitch.
Second reporter narrative
As we lift off and the First Officer calls for gear up; I raise the gear and he tells me that winds were showing 143 KTS crosswind at lift off. At the same time we get a HYD LOW 1 QTY status on the EICAS. As I am finishing the after takeoff checklist ATC asked us what our heading was and we told him 040 heading. He replied we were on a 360 heading. We cross checked our instruments and saw we showed 040; however the standby compass was showing 330 heading. We told ATC our situation and that we were trying to figure our problem out. He gave us a turn to 090 heading. On a heading using the roads and the standby compass as reference we realigned our DG's and were able to fix the problem. ATC said there was no traffic conflict. When we landed we notified maintenance about the incident. We suspect some kind of 'gremlin' might have happened just as we took off. The fact that it showed winds aloft of 143 KTS at less than 1;000 FT was also a concern to us. We were in VFR conditions and both heads were inside the cockpit. If we would have looked outside we would have probably noticed we were flying off course but we were taken by the HYD LOW QTY 1 and the erroneous indication of the winds in the PFD.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.