BAe 125 Series 800
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 96; Flight Crew Total 2600; Flight Crew Type 960
Troubleshooting; Human-Machine Interface; Confusion
Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors
During descent on the SPRTN3 Star via LAN; my Captain and I noticed a discrepancy between the information our FMS/GPS was showing as well as our HSIs. We were given a vector after SPRTN intersection to intercept the 9R localizer into PTK. When we turned to the assigned heading ATC queried us regarding our present heading and location. At this time we realized there was an apparent malfunction with our navigation systems. We were given a descent below the ceiling and became oriented visually using local landmarks and dead reckoning. While we didn't have any system warnings or flagged (failed) avionics; it was apparent that both of our headings were approximately 90 degrees different than our actual orientation.We were subsequently cleared for a visual approach and landed without any issue as ATC helped us gain situational awareness by providing directional cues to the airport once we were in VMC conditions.After discussing the event with Maintenance we are still waiting to hear back on what the issue was. The aircraft is an older model and it is not overly uncommon to have older components fail simply due to their age. Luckily my Captain and I had VMC weather conditions and were able to utilize ATC and good CRM to arrive at PTK safely.
A BAe 125 flight crew experienced a track deviation when their actual heading after receipt of a vector from Approach Control was approximately 90 degrees from the heading assigned.