Date: 202105
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate; Pre-flight; Routine Inspection
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Company Policy; Human Factors; Procedure
Primary problem: Human Factors

Narrative: Showed up to the gate at XA am from being assigned trips off reserve; met the Captain and the gate agent where we learned from the Gate Agent we had 2 non rev maintenance guys coming along with us. Went down to the aircraft where I started doing my checks and setting up my stuff; I came round from my walk around and started doing my 1st flight of the day checks. In the middle of while I was doing my 1st flight of the day flows the maintenance person asked me if he could bring his stuff up to the aircraft instead of the cargo bay I said sure (I heard him say tools and something else) as he walked out the jet bridge I paused for a minute and the Captain walked into the cockpit; he asked me where the maintenance guy was going. I told the Captain he went to get his tools and I think he said something about hydraulic fluid; I told the Captain I haven't read DG (Dangerous Goods) in a while but don't know if we can take it he agreed and went outside to tell the maintenance personnel to hold on for a second; he came back in sat in his seat pulled out the FOM and searched [but] could not find anything specific so decided to ring the duty pilot; at this point I carried on with my first flight of the day flows over hearing the conversation the Captain was having on the phone with the duty pilot; I heard something along of the line as it being explained as a hydraulic pump by hand in a little crate basically a little hand pump; and Captain was assured we are not taking any hydraulic fluid it's been emptied out might have a drop or two that was missed with a paper towel that's all... Captain looked at me and said don't know if you heard most of that which I replied I have he assured me we are not taking any hydraulic fluid and if I was comfortable going in which I told him in that case I have no issue going to fly. Well I believe we did everything that could have been done to ensure we were following SOP and company policy and procedure but there was a breakdown in communication between duty pilot / Maintenance Control and base Maintenance Manager where they forget to tell us we're taking canisters of hydraulic fluid.


Second narrative: I was given Aircraft X on my first day of a four day reserve stretch. When I arrived at the gate I was informed that this was a maintenance (MX) reposition flight for an aircraft in ZZZ1. The two mechanics were sitting in the gate area and I went over to speak to them. I was informed the aircraft in ZZZ1 had issues with its hydraulic 2 quantity and that they had to head over and look at the system. I went back to the gate and got the paperwork; met my First Officer (FO); [Name]; and went down to the aircraft. As we began doing our first flight of day items and loading the flight plan; I told [name] that I would go upstairs and inform the gate agent he could let the mechanics board. Unfortunately the agent was having issues with scanning the mechanics on; so I called our Dispatcher so we could have them put on the release and they could come down. On the jet-bridge with the mechanics one of them told me he wanted to go check if they had got the tools out to the aircraft yet and that he wanted to also 'make sure the pump would not be leaking'. I immediately asked him if he was referring to a hydraulic pump and he confirmed he was. I told him I had to contact the Operations Controller because there should be no hydraulic fluid on the airplane; especially not any that could be leaking. at XA:01am I called the Operations phone tree and connected myself to the Chief Pilot; [Name 2]. I told [Name 2] that Maintenance told me they were worried about a hydraulic pump that could leak in the cargo compartment and needed to know exactly what was going on with this reposition and the equipment I was bringing. [Name 2] agreed with me that no hydraulic fluid was allowed to be transported and we went through the FOM looking for any guidance on hydraulic pumps and transporting that type of equipment. Our joint search of the FOM was in [the] chapter under the Hazardous Materials and Dangerous Goods section. This call lasted 13 minutes and 7 seconds and we agreed that there was no exceptions about equipment such as a hydraulic pump and [Name 2] told me he was going to talk to the Maintenance Head in the Operations. at XA:18 am I missed a call from [Name 2] and he left a message saying 'I just got a little more info on that hydraulic pump so to speak on your guys repo flight. Apparently it's a ground servicing pump; basically a tool we are bringing down there for maintenance.' I called back at XA:19am and he explained to me that we were bringing a pump that Maintenance would use on the ground to pump fluid into a hydraulic system on the other aircraft. He told me that Maintenance confirmed it was washed out and did not contain any hydraulic fluid.  I then went back and spoke to the mechanics to confirm this was the correct information. They said yes; the pump was indeed a servicing pump and it had been cleaned thoroughly prior to transport. With this information I and the conversation with Maintenance and the Operations Controller I decided that this was indeed a legal fight with cargo that was permitted in accordance with our FOM. On Date 2; I received a call from [Name 3] from the safety committee. He informed me that a Captain on the return flight for the broken aircraft was being asked to transport canisters of hydraulic fluid from ZZZ1 back to ZZZ and asked me if I knew anything about how they got there. I told [Name 3] that I had not transported any canisters from ZZZ to ZZZ1 and was under the impression that the pump and two tool kits were the only items aboard my aircraft. [Name 3] told me he would investigate further and call me back. [Name 3] called me back and informed me that we had unknowingly transported 2 canisters of Hy-Jet IV-A+ to ZZZ1 and informed me to fill out an ASAP with all pertinent details. Two Canisters of Hy-Jet IV-A+ were brought aboard Aircraft X ZZZ-ZZZ1 without knowledge to the flight crew. There was clear confusion and either misinformation or lack of information between the flight crew; Operations; and Maintenance. In the future on maintenance reposition flights; or any flight requiring equipment to be flown for maintenance; an itemized list of equipment that is being transported should be signed my maintenance personnel; one copy should go into records and the other copy should go to the flight deck to be reviewed by the flight crew. This way there is a clear paper trail of evidence and accountability in the event that anything like this should ever happen again.


Synopsis: Flight crew reported undocumented Hazmat cargo was going to be transported due to a communication breakdown between flight crew and Maintenance and Duty pilot.