Date: 201606
Local time of day: 0601-1200
Location: ZZZ.TRACON, US
Flight conditions: VMC
Light: Daylight
Aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class D ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Hydraulic Main System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload
Anomaly: Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Upon reaching the airport I was told that a plane had a hydraulic problem. I arrived at the gate and was informed that we would be taking the aircraft that had the hydraulic issue. When we got to the plane the log book was not in the cockpit so we contacted maintenance and requested the log book. They said they were finishing up with it and they would be out soon. A mechanic arrived with the log book and we asked him to brief us on what happened to the aircraft and what was accomplished. He told us that a Hydraulic line on the Green system was resting on another line. There had been a Teflon shield between the two but one line had worn through the Teflon and subsequently wore a hole in the other line causing a leak. I looked at the log book and confirmed the write up and corrective action that replaced the line and returned the aircraft to service. During preflight the green Hydraulic pressure indicated in the normal fill range. I discussed with the FO (First Officer) our plan which would be to check the hydraulic system after startup; during taxi and prior to takeoff. We did this and each time we checked all conditions were normal. We agreed we were O.K. for a takeoff and continued and for this leg the FO would be flying. After takeoff the gear and flaps were retracted on schedule without issue. Once we were turned north and passing through 3000 ft. I chose to check the Hydraulic system in the clean configuration. The green system hydraulic quantity was showing a significant change from what was indicated on the ground. It was indicating just above the amber range. I told the first officer that we would be leveling off and set the altitude to 5000 ft. Because of the recent occurrence with the same hydraulic system; my FO and I chose to [advise ATC] and make plans to return to the field. Not knowing if the fluid was draining out or not my first officer asked if we should go ahead and extend the gear while we had fluid and pressure. I agreed and we lowered the gear. At that time we received a master warning 'Landing Gear Not Down Locked'. The red warning lights above the gear lever were illuminated as well as all gear positions on the wheel page. After approximately 30 to 40 seconds the gear finally extended fully and we started to see green indications but it still took a few more seconds for the gear doors to close after that. Once that was complete the ECAM Fault disappeared and we had a normal working aircraft. The Hydraulic page was showing that the hydraulic fluid in the green system was not higher than it was before with a clean aircraft. We chose to configure to flaps 1 at that time as well and during the extension we monitored the hydraulics with the indications stable. ATC was updated that we did not have a total loss of fluid but were at a reduced level. Since we were in a normal state with the aircraft ECAM we started to move forward with our next decision. The aircraft was currently overweight for a landing and we had to determine whether or not to make an overweight landing. ATC was able to get us set up for holding so we could address the issues. I pulled out QRH and from what was stated we determined that it would be safer to burn the fuel off and get below 142;000 lbs and make a normal landing. I ran the numbers in the MCDU (ACARS) and at our current weight the performance worked and at 142;000 lbs the numbers worked for a landing. I set up the aircraft for an ILS approach and I briefed the FO that I would be taking the controls for the approach and landing. I asked him to request that [ATC would] give us time to configure in the event something would happen to the green system. We planned to start configuring either on a downwind or the base (Flaps 2). I briefed that once we were established on the approach we would configure prior to GS intercept to verify the systems were working properly prior to landing. I had previously called the FA's (Flight Attendants) and updated them with whatwas going on and what the plan was. At that time; I told them the landing would be normal with no brace and that I would update if there were any changes. I then made an announcement to the passengers to what was going on and reassured them we were operating normally but would need to burn off fuel prior to landing. I continued to update the FA's and the passengers regularly through the remainder of the flight. During our downwind vector I was watching the TCAS and noticed there was a target at our 12 o'clock 500 ft below but climbing. The target was about 7 miles and the altitude got to 300 ft. I called [ATC] and informed them of the target and they gave me an immediate 90 degree turn to the right. I saw the target at the 5 mile rage indicating 100 ft below and in the turn we received a TCAS Alert (TA). We made contact with the aircraft and saw it pass off of our left wing.We were vectored onto the approach course and configured as planned. All conditions were normal and I chose to disconnect the A/P and hand fly the rest of the way to the runway. We touched down and the roll out was normal except we received a Master Caution 'Landing Gear Disagree'. We observed that the Hyd and Wheel pages were all showing green and normal indication and continued to taxi. The Green system still indicated the lower quantity that was seen in the air. We stopped at the gate and continued the shutdown process.Once maintenance came aboard we explained to them what happened and they said that it sounded like that was still air in the lines from the previous hydraulic issue the day before.At this point I was mentally spent/fatigued and subsequently left the aircraft without making a log book entry. My FO called me and asked if I had made the entry and [I] said no. I was still at the airport and I asked the FO to come with me to confirm the log book entry. We filled it out in the maintenance shack and left for the day. Possibly had my head down too much. Completely focused on the matter at hand (Overly Consumed). Needed to step back; take a drink of water every once in a while. As a result of not doing this I was completely depleted once we got to the gate.




Synopsis: MD-80 Captain reported returning to departure airport following loss of Green hydraulic system.