Both of a CE750's ahrs malfunctioned after a lga runway 13 takeoff and required ATC vectors referenc...

Attributes
ACN	1005978
Time
Date	201204
Local Time Of Day	1201-1800
Place
Locale Reference	LGA.Airport
State Reference	NY
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	Citation X (C750)
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Vectors SID LGA 4
Flight Plan	IFR
Component
Aircraft Component	AHRS/ND
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 25000 Flight Crew Type 3500
Events
Anomaly	Aircraft Equipment Problem Critical Conflict Airborne Conflict Deviation - Track / Heading All Types
Miss Distance	Horizontal 33000 Vertical 1500

Narrative:

During the SID climb departure it became immediately apparent that ahrs headings had both malfunctioned and were 30-45 degrees off from each other. Navigation information was extremely unreliable. Dg fast slave did not work on either ahrs and autopilot could not be used. Mag compass was only immediate heading source. When ATC cleared us on a heading it was way off due to mfd map error. Down track VOR's were given but again displayed info was erroneous and direct course could not be flown precisely even with raw data green needles. It was during an attempted direct to a VOR that we began to deviate toward another aircraft in the vicinity of 34;000 ft. ATC controller put us back on a divergent heading so conflict would not occur. We got no TCAS warning or loss of min separation indication from the controller. Finally at higher altitudes and in smooth air; mag compass settled down enough to steer a reasonably accurate heading. Right ahrs also settled down enough at cruise to use in conjunction with autopilot.

Original NASA ASRS Text

Title: Both of a CE750's AHRS malfunctioned after a LGA Runway 13 takeoff and required ATC vectors referencing the magnetic compass until the compass systems returned to normal at cruise operating independently.

Narrative: During the SID climb departure it became immediately apparent that AHRS headings had both malfunctioned and were 30-45 degrees off from each other. NAV information was extremely unreliable. DG Fast Slave did not work on either AHRS and autopilot could not be used. Mag Compass was only immediate heading source. When ATC cleared us on a heading it was way off due to MFD map error. Down track VOR's were given but again displayed info was erroneous and direct course could not be flown precisely even with raw data green needles. It was during an attempted direct to a VOR that we began to deviate toward another aircraft in the vicinity of 34;000 FT. ATC Controller put us back on a divergent heading so conflict would not occur. We got no TCAS warning or loss of min separation indication from the Controller. Finally at higher altitudes and in smooth air; mag compass settled down enough to steer a reasonably accurate heading. Right AHRS also settled down enough at cruise to use in conjunction with autopilot.

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.

Both of a CE750's ahrs malfunctioned after a lga runway 13 takeoff and required ATC vectors referencing the magnetic compass until the compass systems returned to normal at cruise operating independently.