Dual GPS failures result in track deviation for E145 on akuna RNAV SID from dfw.

Attributes
ACN	782913
Time
Date	200804
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	792913
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	782912
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : overcame equipment problem
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

After takeoff from dfw with both FMS's loaded correctly; I selected navigation and watched the aircraft guide itself to the first fix. Both my side and first officer's side showed normal navigation and tracking. Looking outside I could see; however; that we were actually drifting left of the normal visual references on the ground. I checked my mfd and it showed tracking normal. A glance at my first officer's mfd showed we were drifting left. I disconnected the autoplt and started to turn back right. About that time ATC gave us a heading of 180 degrees. We selected conventional navigation at this point and advised ATC we had lost our GPS capability. They gave us vectors and we continued to ZZZ. Later; center frequency asked us to call dfw TRACON. We did upon arrival. We told them what happened and we advised them as soon as possible. Troubleshooting the problem later we discovered that both GPS 1 and GPS 2 had failed.

Original NASA ASRS Text

Title: DUAL GPS FAILURES RESULT IN TRACK DEV FOR E145 ON AKUNA RNAV SID FROM DFW.

Narrative: AFTER TKOF FROM DFW WITH BOTH FMS'S LOADED CORRECTLY; I SELECTED NAV AND WATCHED THE ACFT GUIDE ITSELF TO THE FIRST FIX. BOTH MY SIDE AND FO'S SIDE SHOWED NORMAL NAV AND TRACKING. LOOKING OUTSIDE I COULD SEE; HOWEVER; THAT WE WERE ACTUALLY DRIFTING L OF THE NORMAL VISUAL REFS ON THE GND. I CHKED MY MFD AND IT SHOWED TRACKING NORMAL. A GLANCE AT MY FO'S MFD SHOWED WE WERE DRIFTING L. I DISCONNECTED THE AUTOPLT AND STARTED TO TURN BACK R. ABOUT THAT TIME ATC GAVE US A HDG OF 180 DEGS. WE SELECTED CONVENTIONAL NAV AT THIS POINT AND ADVISED ATC WE HAD LOST OUR GPS CAPABILITY. THEY GAVE US VECTORS AND WE CONTINUED TO ZZZ. LATER; CTR FREQ ASKED US TO CALL DFW TRACON. WE DID UPON ARR. WE TOLD THEM WHAT HAPPENED AND WE ADVISED THEM ASAP. TROUBLESHOOTING THE PROB LATER WE DISCOVERED THAT BOTH GPS 1 AND GPS 2 HAD FAILED.

Data retrieved from NASA's ASRS site as of May 2009 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.