Date: 201512
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Other
Operator: Corporate
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Cruise
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Hydraulic System
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: Pilot Flying; Instructor
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Human factors: Situational Awareness; Troubleshooting; Distraction
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; Flight Crew Inflight Shutdown
Contributing factors: Aircraft; Weather
Primary problem: Aircraft

Narrative: At XA:10am I departed ZZZ with a student in an airship for a local area training flight. At XB:04 we had an aft hydraulic level low light illuminate. The QRH was completed and finished with 'monitor pressure'. I called my ground crew to let them know I was going to return to the field for a precautionary landing. The Chief Mechanic said it may be a bad sensor; which at the time I would have agreed. At XB:07 I told the Mechanic that the hydraulic pressure though still normal was sitting at a lower than normal value. I was wondering if now that it may be more than a sensor. At XB:59 the hydraulic pressure dropped to 0 a couple times and back up to normal. This continued for the rest of the cruise portion of the flight. I informed the mechanic of this as well he acknowledged and we agreed now that it was probably more than a sensor. I briefed the approach plans and job roles to my student pilot (whose role is now pilot not flying PNF) and my ground crew. On downwind I vector my aft engine into Landing mode and the hydraulic pressure dropped to 0 and the hydraulic pressure low light illuminated. We ran the QRH and continued flight as per the QRH to 'landing as soon as practical'. On final the winds were 25-30 knots and shifting. For an airship this was a little too much to proceed safely. We decided to go around on the basis: we had 10 hours of fuel on board winds were supposed to come down later and it was VMC conditions with no weather in the area. Due to the fact we were going to be flying for a while; and the PNF and I at this point; assumed we lost hydraulic fluid in the engine compartment; we decided to shut the aft engine down. I discussed with my PNF and we figured this was the best course of action to avoid any chance of hydraulic fluid in engine compartment causing a fire. I advised tower of our situation and that we would be waiting on winds to calm down before we attempted an approach. They were extremely helpful with keeping us informed of wind conditions at the field. I briefed with the PNF that we would be doing a dynamic approach and what each of our functions were for this approach. We ran the QRH for the engine shutdown and securing and an approach to landing with one engine failed. At approximately XE:45 the tower call: 'winds are holding pretty steady at 14 with a very occasional gust to 18 if you are ready to try it. I'm sure you are aware that the winds aren't forecast to come down until after XK:00pm' I replied with 'thank you; let me talk to my ground crew and get them set up and we will try it.' During the wait for the winds I called the ground crew and had them call more nose line handlers out for a dynamic landing. They were able to call out enough crew to accomplish the landing. We briefed the approach one more time. I told ground crew I would try a low approach and see how smooth final was. If it was smooth; I would continue to a landing. I asked tower to keep the runway on either side of our landing site clear just for my short final and landing in case of a wind shift. They agreed and were very helpful on this request. I dumped 100kg of water to put my weight where I wanted it for the landing. We landed without further incident and secured on the mast. I thanked tower and let them know we were secured.




Synopsis: An instructor pilot; conducting training on an airship; reported observing an aft hydraulic low caution light; followed by a subsequent loss of hydraulic pressure. The appropriate QRH checklists were accomplished and the aft engine was shut down as a precaution. After gusty wind conditions improved; a successful recovery was accomplished.