Rotorcraft pilot reported no oil pressure during two consecutive post maintenance engine runs and elected to forego any additional engine runs until maintenance could investigate.

Narrative

After a transport lasting from approximately XA00-XH30; the med crew and I returned to base and were informed that we would be out of service for maintenance. At this time; I placed the helicopter in the hanger; debriefed with the crew; and returned to my office to complete the manifest.At approximately XI30 I approached the aircraft to check in on the maintenance with Person B and Person A. I inquired about the filter; asking Person A if that was the filter that was sent in to be weighed and he answered 'Yes'. I observed Person A show Person B the replacement of the O rings for the filter housing and filter. I then returned to my office. At approximately XJ00 Person B came to my office and stated maintenance was complete; requesting me to complete a maintenance ground run up leak check; to which I agreed. Person B informed me that he did an auto pilot visual check and removed three panels. At this time; he showed me the panels (the first was located underneath the aircraft attached to the ELT antenna; the second was under the pilot's seat; and the third panel was located in the baggage compartment) I assessed each panel to ensure they were secured properly (which they were). He also informed me they completed the 150-hour oil filter change; together we assessed the filter location and confirmed it was installed and securely tightened. I was informed by Person B that there may be some residual oil trapped in the heat shield that could potentially leak out. I noticed Person A using the Honeywell computer and asked Person B what he was doing. I was told by Person B that he was clearing a maintenance light that was induced by prematurely engaging the power before a sensor wire was plugged in. I was also informed that once this was cleared; we would be able to do the run up. I confirmed with Person B that we just needed to do a run up for a leak check and was told yes just for the leak check. I proceeded to complete my walk around; both engine cowlings were open at this time. I visually inspected each side of the engine for items such as rags and tools as well as loose nuts and bolts. I went to step on the right side step and removed a rag; then I looked into the right transmission cowling and upper deck where nothing abnormal was discovered. I stepped down; moved the ladder away from the aircraft; walked around the tail boom and continued to visually inspect cowlings and fasteners. On the left side I retrieved the step stool to look in the engine cowling that was open as well as the left side transmission cowling; continuing to inspect and nothing abnormal was discovered. I got off the step stool and placed it to the side. At this time; I noticed Person A was speaking on the phone regarding the Honeywell computer; which he was still working on. I was notified it would take a few more minutes before I could transport the aircraft outside for the run up. I walked into Person C's office to inform them that I would be doing a maintenance run up; also inquiring if there was night shift pilot coverage; to which I was told there was not. I returned to the hanger to find Person A was done with the computer. I assisted Person B with placement of the heliporter under the aircraft and proceeded to transport the aircraft outside. Person A remained in the hanger. I removed the heliporter from under the aircraft and placed it in front of the hanger door. At this time; I completed another walk around check around the aircraft inspecting for abnormalities; with exception of the opened cowlings for leak check inspection nothing was out of the ordinary. I spoke with Person B and asked him how he wished to perform the run up; he informed me he would like a normal startup; once ready take it to 100 percent and run it for approximately ten minutes; if there were any leaks or abnormalities; he would immediately give me the cutoff signal to shut down the helicopter. I entered the aircraft as Person B retrieved his hearing protection; once he returned; he stated he was ready and clear to start. I placed my helmet on and fastened my belts. Per prestart and startup checklists I started the helicopter. Engine ignition at approximately 12 percent Ng; MGT temperature rise normal; voltage normal; blades turning by approximately 18 percent; transmission and oil pressure gauge with pressure increase; and no lights were observed. Start completed with starter light out and approximately 62 percent Ng. Start checklist completed; alternator on; FADEC reset; no lights observed; gauges in the green. I proceeded to roll up throttle while observing the torque gauge increasing abnormally slow. I rolled throttle back down to idle then rolled it back up observing the torque gauge to once again increase abnormally slow; simultaneously the low engine oil pressure light illuminated. When assessing the oil pressure gauge; I saw zero oil pressure and rolled throttle off; engaged rotor break below 40 percent; turned off generator; and turned off the battery. Once the aircraft was shut down; I informed Person B what had occurred. While I exited the aircraft; Person B went to get Person A from the maintenance hanger. I returned to the helicopter hanger; where I waited for Person A and Person B to join with their assessment of the findings and plan for diagnosing the problem. Approximately five minutes later both Person A and Person B returned to the helicopter with their ladder; tools and oil. I observed Person A adding oil and consulted with Person B regarding what they felt the problem was. Person B stated there was approximately two quarts of oil noted in the reservoir and there may be some air in the line; the plan was to add more oil then proceed to complete another ground run. Once Person A was finished adding oil he informed me that he was ready for the ground run. I went to the oil reservoir and assessed the oil level as well as ensured the cap was secured. I discussed with Person B the plan for the ground run; and was informed that we would proceed like the prior ground run; keeping a close eye on the oil pressure. I completed another walk around the aircraft ensuring all rags; tools and equipment were removed before entering the helicopter. Per prestart and startup checklists I started the helicopter with Person B next to me. Engine ignition at approximately 12 percent Ng; MGT temperature rise normal; voltage normal; blades turning by approximately 18 percent; zero indication of oil pressure increase; and transmission oil pressure was increasing. Focusing my attention on the oil pressure gauge I allowed the Ng to increase approximately another 20 percent; with zero indication of oil pressure increase. At this point Person B instructed me to shut down the aircraft; I rolled throttle off; engaged rotor break; and turned battery off. I exited the aircraft and went to the helicopter hanger. In the hanger I spoke with Person A and Person B; inquiring what they thought the problem may be. I was informed by Person A that they may have to bleed the lines out; although he has never had to do this before. Both Person A and Person B went to the Maintenance hanger. It was now approximately XJ50; I returned to the office where I gathered my stuff to complete my shift. Approximately five minutes later Person A entered the office and I asked if he would like me to return the aircraft to the hanger. He informed me that he would like it returned to the hanger and the aircraft would be out of service for the night as he was awaiting more information from Person C regarding the next steps for maintenance of the aircraft. I returned the aircraft to the hanger using the heliporter; securing it for the night; and completed my shift as there was no Relief Pilot for the night shift to report off to.