An EMB145 compass system heading was aligned with the departure runway but after takeoff disagreed b...

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.

Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	919744
Time
Date	201011
Local Time Of Day	1801-2400
Place
Locale Reference	ORD.Airport
State Reference	IL
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	Climb Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	AHRS/ND
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Commercial
Person 2
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Clearance Deviation - Track / Heading All Types

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 hydraulic low qty 1 ECAM alert.