Eurocopter AS 350/355/EC130 - Astar/Twinstar/Ecureuil
Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Commercial
Flight Crew Last 90 Days 60; Flight Crew Total 5000; Flight Crew Type 2500
Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification
Aircraft
I was in the PIC (Pilot In Command) (right) seat conducting training for a CFI student in the left seat. We were performing simulated hydraulics failures in the traffic pattern at ZZZ airport. We were using the hydraulics isolate switch on the right seat collective to shut off the hydraulics on downwind and performing simulated run on landings at hover height over the runway. While climbing away from the runway I told the left seat pilot I was ready for the hydraulics to be turned back on. I felt him flip the switch on my collective back up and heard the normal warning horn come on briefly. Normal control forces returned; however; the HYDR light remained on. We turned crosswind and decided to recycle the switch again to see if the light would turn off. It did not. Instead of turning downwind at ZZZ we turned back towards our home base of ZZZ1. We discussed if there was anything we were missing and how we could determine if it was just the light or if it was an actual hydraulics failure and we were on the backup accumulators which only offered a limited amount of time before they would deplete. The other pilot and I determined that there was no way to determine if we still had the main hydraulics system functioning normally so we has to assume they were off-line. The emergency procedure is to level the aircraft and fly between 40-60 kts. ; then use the collective HYDR cut off switch and shut down the system before the accumulators start to deplete before performing a run on landing. I [advised ATC] with ZZZ1 and told them I would need Runway XX/XY for a run-on landing. The run on landing was performed normally. Once on the ground I reengaged the hydraulics system and manipulated the controls long enough to determine that we were not working off the limited supply of the back up accumulators. We hover taxied over the taxiways back to our ramp. After landing our Maintenance staff found the switch for the hydraulics warning light needed to be replaced. After replacement of the switch the system worked properly. I contacted ZZZ1 Tower and Airport Rescue and Fire asking if they required any reports from us and both indicated that the phone call was sufficient.
Eurocopter pilot reported failure of hydraulic switch resulted in return to home airport.