Date: 201411
Local time of day: 1801-2400
Location: CIC.Airport, CA
Flight conditions: IMC
Weather elements / visibility: Rain; 4
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Initial Climb
Airspace: Class D CIC; Class E ZOA
ATC / advisory: Center ZOA
Aircraft component: Compass (HSI/ETC)
Component problem: Failed
Reporter organization: Personal
Reporter function: Instructor
Reporter qualification: Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Workload; Troubleshooting; Distraction; Human-Machine Interface; Confusion
Anomaly: Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Automation Air Traffic Control; Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: IFR Instructional flight for a new IFR student (his third IFR training flight) in [a] Cessna 172. We departed normally IFR on the departure procedure (Gongs 1) [but the] student was having difficulty maintaining the radial outbound; which I initially attributed to a case of vertigo. Coaching him to correct his course; I soon realized that the directional gyro (DG) was acting erratic. The heading bug was frozen and the DG I perceived to be lagging. Taking control of the aircraft I leveled the wings. Cross reference with the GPS track indicated that the DG was more than 40 degrees off. The heading bug wouldn't follow the DG card but would stay frozen where it was placed. I reset the DG to the wet compass and decided to return to our departure airport (Our evening flight was to be an IFR [round trip]). I then asked center for vectors back to the airport. He indicated that I should [have] ask[ed] for the vectors before turning towards the airport since he had an aircraft on the approach. I indicated I was having an equipment malfunction and difficulty in that arena. I leveled off at the assigned altitude; and Center asked if I needed a no gyro approach. The gyro seemed stable for the moment; so I reset it and indicated that we should be able to take vectors. I asked him what my heading was while being vectored onto the approach to ensure that I was flying the vectors he was assigning. He indicated I was off by 20 degrees. I checked the compass and set the gyro again and corrected. As we were vectored onto the ILS 13L approach; the gyro seemed stable. As the approach progressed; the gyro became erratic again. We weaved down the ILS and popped out VFR around 2000 feet. We then cancelled IFR with Center and landed without incident. In retrospect; I should have accepted the controller's offer of no gyro approach. Funny how you want to trust the instruments; and tough it is to ignore one; even one that is acting up. Machines don't heal themselves; so once it began acting up; I should have abandoned its information and relied on the controller. I did alert him to our problem as soon as I recognized it; however I could have handled the situation better; I feel.




Synopsis: An instructor pilot and his instrument rating student were on a training flight in IMC when the directional gyro failed.  ATC provided assistance to return them to their departure airport where they combined resources to exit IMC descending through approximately 2000 feet on approach.