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For decades, it has been a part of the folklore shared by those who grew up around Lake Massabesic in Manchester — a piece of World War II history is rumored to have been lying at the bottom of the lake since the winter of 1945. Over 80 years later, a team of researchers, engineers, and students from UNH is using state-of-the-art underwater mapping technology to try and locate a missing gun ball turret — a spherical, rotating gun platform designed for firing heavy weapons — that was reportedly dropped into the lake from a B-17 aircraft during an attempt to refuel. 

“This has been an exciting opportunity to search for a part of New Hampshire history,” says Val Schmidt, research project engineer at UNH’s Center for Coastal and Ocean Mapping. “Our team has been a part of some interesting projects around the globe, but this one has allowed us to partner with the local community as well as learn more about the Granite State’s role in World War II.”

Engineers and experts, from UNH’s Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM) and the Chase Ocean Engineering Lab, went to work to locate the ball turret from a WWII B‑17 aircraft (serial #44‑6694) — known as the Flying Fortress — which belonged to the 99th Bombardment Group that was en route to Tortorella Airfield in Foggia, Italy. The gun turret was purposely dropped into the lake after an aborted landing attempt at the Grenier Air Base — now Manchester-Boston Regional Airport — which was home to the 1377th Army Air Force Base Unit during World War II. 

“The story is that the B-17 bomber broke off its tailwheel during a landing attempt and then had to go around. To help make it safer to land, the crew were instructed to drop the lower ball turret into a nearby lake,” says Alex Saidel, a Manchester resident and history enthusiast who grew up around the reservoir. “I’d forgotten about the incident until a chance meeting with local author Dennis Sasseville, who mentioned it during a conversation about local World War II crash sites. I told him that we need to find it, remove it, and restore it for the aviation museum and started searching for underwater sonar which led me to UNH.”

In collaboration with the Manchester Water Works — which maintains the reservoir — and the Aviation Museum of New Hampshire, the UNH team set up an ocean mapping mobile control van along the shores of the lake. They used a battery powered robotic boat known as an uncrewed surface vessel (USV) that was integrated with an M3 Multibeam Echosounder — on loan from KONGSBERG, one of the university’s industry partners — to help with the exploration. A small Garmin sidescan sonar was also integrated into the robotic system to provide acoustic imagery of the lakebed. The advanced high-resolution multibeam sonar allows the team to collect data for 3D topographic maps while the Garmin side scan provides acoustic shadows of objects to characterize any potential finds.

Graduate students in UNH’s summer hydrographic field course also took part in the search, which offered a unique opportunity to explore a local body of water for a historical artifact. The class is composed of graduate students from the United States and around the world who are enrolled at the center which is known for being the nation's premier Category A Hydrographic mapping training program. 

“The fact that this historical search is happening in New Hampshire has been a great hands-on opportunity for our students,” says Semme Dijkstra, clinical professor at UNH’s Center for Coastal and Ocean Mapping. “During the course, they get training on UNH’s ocean mapping vessel, the R/V Gulf Surveyor, but this type of uncrewed, remote vehicle is being used more and more in the quest to map the world’s oceans, and this has just been a wonderful experience for them.”

Sasseville, the local historian who connected with Saidel, was able to locate the Army Air Force report from January 1945. The document indicates that the airfield was covered with “patches of ice” and the plane’s tailwheel was smashed off during the first missed landing, making a second landing attempt too dangerous. The B-17 ball turret is attached under the middle of the plane in a way that could break the back of the fuselage if they tried to land without landing gear (called a belly landing). According to the accident report, the pilot was told to “let the ball turret out over the lake”, most likely because of the size and proximity of Lake Massabesic.

UNH’s CCOM is a national center of expertise and the team has traveled the world on similar historic missions as part of high-profile exploration teams, including a mission with National Geographic Explorer-at-Large Robert Ballard to look for the plane wreckage of pilot Amelia Earhart and a search by the Ocean Exploration Trust (OET) for sunken Naval ships from World War II in their deep-water resting place in the Solomon Islands. UNH also played a key role on a NOAA/OET exploration team locating the Ironton, a 191-foot sailing ship that sank in Lake Huron in 1894. 

After two weeks of mapping the 2,500-acre lake, the turret remains elusive, although the team did identify areas of interest. The UNH team is working with the historians on next steps, although no plans have been confirmed. If located, a recovery and restoration plan would be put into place. The Aviation Museum of New Hampshire, which published the book , has already offered to give a new home to the wreckage that may help solve the decades-long mystery.

"For many years, we've known that the ball turret from a B-17 at Grenier Air Base was dropped into Lake Massabesic during World War II. It's exciting that there's an effort to locate and retrieve it," says Jeff Rapsis, executive director of the Aviation Museum of New Hampshire. “Almost no physical trace remains of Grenier Air Base, where once thousands of troops from all over the nation trained for deployment on missions in Europe and all over the world. It was often the last U.S. ground on which soldiers set foot before shipping out and should not be forgotten.”