If you’ve ever spent hours walking around your yard staring at the ground — going back and forth, back and forth — to find an earpod that you think fell off while weeding the lawn last week, you can sympathize with the University of New Hampshire’s Center for Coastal and Ocean Mapping.
Except the goal of center’s stint at Lake Massabesic in Manchester was to find a ball turret from a Flying Fortress bomber that was dropped on the lake bottom eight decades ago, and its carried out its search with sonar operated out of a remote-controlled boat. The center hasn’t found the turret yet but its people are still holding out hope.
“This is an interesting project,” is how Val Schmidt, research project engineer at the center, put it.
But it’s not a novel one for the center. As part of its contracts with NOAA’s Office of Coastal Survey and Office of Ocean Exploration, the center has has done underwater searches and analyses in places as disparate as Lake Erie, the Solomon Islands and the Atlantic seaboard.
With those under their belt, you’d think finding a four-foot-wide metal ball in a lake that averages 17 feet deep would be easy. It sure looks easy when they do it in TV documentaries! So, what happened?
World War II in Manchester
The backstory of the search involves Manchester airport’s role in World War II as a staging area for the Army Air Corps (precursor to the Air Force), where air crews were trained before heading to Europe. According an official report from January 1945, a F-17 Flying Fortress bomber hit some ice on the runway while trying to land and smashed its tailwheel, forcing it to try again and make a “belly landing.”
The Flying Fortress famously has a rotating ball turret armed with heavy machine guns sticking out from its belly, allowing a gunner to defend the plane as enemy fighters approached from below. The turret would have damaged the fuselage in a belly landing, so it was released over an unnamed lake that presumably was Massabesic. There it lay forgotten for decades until local military buff Alex Saidel heard about it and began pushing to have it found.
The Center for Coastal and Ocean Mapping was an obvious candidate for the search, especially when it was incorporated into summer hydrographic field course with graduate students.
The search used two types of sonar to get “pictures” of the lake bottom, seeking the turret. There were some complications, Schmidt explained.
One is that the lake bottom isn’t flat. This rules out a simple back-and-forth search pattern, also known as boustrophedon, which is one of my favorite words.
The sonar “view” from the ocean-mapping vessel, R/V Gulf Surveyor, is wedge-shaped going down from the boat.
“The deeper the water, the wider the swath we can map is. So we can’t run constant interval lawnmower lines like you’d do on the flat bottom of a pool,” he said. That greatly complicated the search algorithm.
Glacier lake drawback
The second, bigger problem: “This is a glacier-formed lake. It’s got boulders in it, lots of boulders, many of which are roughly the right size. … There’s a potential for lots of false positives,” Schmidt said.
Massabesic also has a long history of recreational usage, meaning the bottom has its share of stuff that has fallen off boats or the occasional unlucky snowmobile. That doesn’t help.
Students are going over the data now to weed out bad examples but definitive answers will probably require going down with a diver or remote-operated underwater vehicle, Schmidt said. Another possibility is using a marine magnetometer, similar to a metal detector, to separate an artificial metal ball from a natural stone one. However, UNH doesn’t own one, and even if they bought one, it would require underwater towing beyond the Gulf Surveyor’s capabilities, so that might not happen.
Finally, there’s a third issue: The turret might not even be in Lake Massabesic.
“It’s possible that the army pulled it out of the lake and didn’t put it in a report,” Schmidt said.
Even if the turret isn’t there or is there is never found, the project is still good training for students, a good look into a forgotten bit of local history (I’m associated with the Aviation Museum of New Hampshire, and so far as I know, we’d never heard of this incident) and a good chance for us to see some of the interesting stuff they do at that big school in Durham.
As for me, I’ve just about given up on finding that earpod. Maybe I can get UNH to help.
