20200807017779I

At approximately 1315 EDT, pilot and a photographer departed the beverly airport for londonderry, NH to record some video of a vehicle crash. After departing kbvy, pilot switched over to boston approach for advisories as well as a transition over the top of the lawrence class d airspace at 2500 feet. Upon clearing the northern boundary of the klwm airspace, with only a few minutes to be over our destination, pilot told approach he was going to start a decent to 1700 feet to work over the scene. That was approved and pilot lowered the collective, reducing power slightly and began a cruise decent. Perhaps 30 seconds or so later and around 2000 feet, the helicopter yawed to the left. Pilot looked at the instrument panel, noting the torque gage coming back up through 50% rising to 85%, then back down toward 50%. Very quick surges. At that point, pilot lowered the collective, and looked for a forced landing site that could be made without power. Pilot identified one and started maneuvering the helicopter into a position the assure making that spot. When pilot had that area assured, to his right, pilot then looked back to the left at the instrument panel to check the status of the engine. The engine was still running, (never had an engine out light or horn audible), also the engine was not surging, albeit at flat pitch decent using little power. With the landing are assured, pilot wanted to increase the power, check the engine for response. Pilot pulled in approximately 50% torque. The engine responded without surging. Pilot decided to find a better landing site as there were a few available, of which some had a better surface. Pilot moved toward a large vacant animal yard, without animals. It appeared vacant and large. After crossing over that field, (approximately 30 seconds had now passed since the pilot reintroduced the 50% power back into the engine), the engine started surging again. Pilot thinks it was about the same 50-80/85% range. At that point, pilot got the surface winds, told approach he was going to make a precautionary landing, and he would call them when he got on the ground. Pilot made the 180ISH degree turn back to the large vacant animal yard, set up for a low power, nearly flat collective pitch approach, (in case engine stopped running) into the vacant animal pasture. During the decent, a parking lot that he had noticed earlier, at a church, adjacent directly to the pasture had 2 cars on it. Pilot opted to land the helicopter on the hard surface of the parking lot and if the engine failed he could, if needed, extend the landing into the pasture. Nearing the bottom of the approach into the parking lot, the engine was still running, not surging. After slowing the helicopter down, pilot started adding power approximately the last 20 feet. The engine surged as before a couple times during the last 10 feet to landing (touchdown). Landing was uneventful. After touchdown, with the collective at flat pitch the engine was not surging. Pilot rolled the throttle back, all appeared normal with the engine at flight idle as well. Pilot then shut the aircraft down