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How BentProp and undersea robots found long-lost WWII bombers

Hundreds of families of Americans missing in action in Palau since World War II have long wondered what happened to their loved ones. Now cutting-edge oceanographic technology is helping find answers.

Daniel Terdiman Former Senior Writer / News
Daniel Terdiman is a senior writer at CNET News covering Twitter, Net culture, and everything in between.
Daniel Terdiman
9 min read

For 70 years, the waters off the island nation of Palau have hidden dozens of American planes shot down by the Japanese in World War II. Now a volunteer organization that's been hunting for the planes since 1993 has teamed up with some of the world's leading oceanographers and is applying the latest high-tech tools to the hunt. Illustration by James Martin/CNET

AIMELIIK STATE, Palau-- Pat Scannon glanced down at his waterproof notebook and prepared to read. Nearby, hovered around the stern of the Kemedukl, a 40-foot aluminum catamaran, the team responsible for finding a World War II torpedo bomber lost at sea waited for Scannon to start the flag ceremony for the plane's long-lost airmen.

In the second half of 1944, a TBM Avenger with a crew of three, flying with a Navy torpedo squadron, "took off from a fast attack aircraft carrier on a mission flying over the State of Aimeliik in the Republic of Palau," Scannon read, as part of a March 31 ceremony. "The crew was listed as missing in action and has remained listed as missing in action for the past 70 years."

The high-tech hunt for WWII MIAs (pictures)

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No more. The Kemedukl, which takes its name from the Palauan term for the bumphead parrotfish, bobbed on the gentle sea, just 100 feet above the Avenger crash site. The bomber was discovered on March 24, barely 300 yards from the mangrove jungles of Aimeliik.

As team leader of the BentProp Project, Scannon fronts a volunteer group that makes annual expeditions to Palau, an island country about 1,000 miles east of Manila. His aim is to find as many as possible of the 217 US Navy, Marine, and Army Air Corps planes -- and the remains of the airmen aboard them -- lost during 14 months of fighting around Palau between 1944 and 1945. Since 1993, the project has found 36 American planes, and a few dozen Japanese aircraft.

The search for the Avenger and its crew lasted nine years.

On March 31, 2014, BentProp Project team leader Pat Scannon opened a flag ceremony directly above the wreckage of an American F6F Hellcat shot down by the Japanese in Palau in 1944. Later that day, Scannon would lead a similar ceremony above the wreckage of a TBM Avenger also shot down in 1944. Daniel Terdiman/CNET

"It's always exciting to discover a new crash site," said Scannon, a thin, 67-year-old dressed in cargo pants and a weathered ball cap, a red bandana tied under his full white beard and mustache. "But what it really means to me is that we've begun a process whereby the families of these missing airmen are finally going to get answers."

For years, BentProp had used a combination of deep research and a smattering of technology to find missing planes. But the easy discoveries had been made, and the aircraft still hidden in the Palauan waters were the hardest to find. Fortunately, the organization now has new partners in its hunt, two groups of expert oceanographers (plus a team of smart high school roboticists) with expensive gear like autonomous underwater vehicles that can go much farther than Scannon and his crew ever could. This highly effective yet impersonal technology is now helping to answer some of the most personal, human questions left from World War II.

Nine bloody operations

To all but serious World War II buffs, Palau's place in the Pacific War isn't well known. But the Micronesian archipelago of 250 islands was key to allied victory. Between March 1944 and May 1945, the US mounted nine separate operations there, at first attacking (and largely destroying) the Japanese sea and air fleets there. American fighters went on to take the airfield at Peleliu in a brutal 10-week campaign that cost 1,285 American and 11,000 Japanese combatants their lives. Controlling that airfield was vital to protecting the US flank in the Philippines.

The story of how BentProp found the Avenger begins in 2005, when, taken there by a Palauan, Scannon and a seven-member team found a wing in the thick mangroves at the edge of Aimeliik. Despite exhaustive, and admittedly inefficient, searches on land and in the nearby waters, the team failed to locate the rest of the plane. Their fortunes changed in 2014, thanks to new documentation, additional information from locals, deep research at the National Archives, and, as important, access to cutting-edge technology run by the science teams from the Scripps Institution of Oceanography and the University of Delaware.

The tiny island nation of Palau is located about 1,000 miles southeast of Manila. Screenshot by CNET

But first some history on Scannon, who began his searches for American MIAs almost by accident. In 1993, he and some scuba buddies from Xoma, a Berkeley, Calif., biotechnology company he co-founded, traveled to Palau. Their goal was to be the first people to find the Japanese trawler that, in the summer of 1944, was the initial kill of then-Ensign George H.W. Bush.

That search was successful, and flush with excitement at being so close to history, Scannon began trolling the Palauan islands for other sunken World War II artifacts. If there was any doubt that Scannon, a doctor and a scientist, would devote a big part of his life, and substantial financial resources, to hunting for lost airmen he'd never known, two early successes cemented his resolve. In 1994, he returned to Palau armed with information about three missing B-24 Liberators that crashed during bombing raids in 1944. In just 48 hours, he found two.

Watch this: Underwater robots helping find missing WWII planes, airmen

At first working alone, and then with a few confederates, Scannon realized his annual efforts required more structure, particularly if he wanted the respect and cooperation of US military representatives tasked with investigating MIA sites and notifying family members. The work is slow, and on many expeditions, despite spending a full month in Palau, they don't find any American aircraft.

Sometimes, the discovery of a plane, such as that of the third Liberator -- chronicled in Wil Hylton's compelling 2013 book "Vanished" -- is due more to luck, and exhaustive research, than to the scientific method.

A poster for the P-MAN XVI expedition, on the wall of the meeting room at the Coral Reef Research Foundation in Koror, Palau, where oceanographers from Scripps and the University of Delaware debriefed each night about progress in the hunt for lost World War II airplanes. Scripps brought the poster as part of its STEM outreach program sponsored by the Office of Naval Research. Daniel Terdiman/CNET

In 2002, the BentProp Project became a formal organization. Now Scannon and other members, each of whom pay their own costs, return each year on what the group refers to as P-MAN (for Palau-Marine, Army Air Force, Navy) missions.

The monthlong 2014 expedition, dubbed P-MAN XVI, began March 15. By coincidence, it was at about that time that the world was getting caught up in the high-profile search for another aircraft presumed lost deep underwater, the missing Malaysia Airlines Flight 370.

Side-scanning sonar

One night in 2012, the BentProp crew ran into a group of diners at the Drop Off Bar and Grill, a popular seaside watering hole on the south end of the main drag in Koror, Palau's only real population center. They were led by Eric Terrill, director of Scripps' Coastal Observing and Research Center, and Mark Moline, director of the University of Delaware School of Marine Science and Policy.

The two veteran oceanographers were together running their own annual mission, a scientific effort started in 2010 and funded by the US Office of Naval Research, to track sea level rise, currents, and weather data in the Palauan islands. Terrill and Moline travel with fancy toys, most notably three remote environmental sampling units, $300,000 programmable underwater robots, known as Remus, packed with cameras and sensors, that are fantastic at surveying underwater environments. The robots also include a sophisticated side-scanning sonar system that generates imagery of the sea bottom, even when visibility is poor.

BentProp was familiar with side-scanning sonar, and had been towing a tethered device from a boat. But that approach was slow and inefficient. The Remus, said Moline, could be sent out on autonomous missions, methodically covering huge grids. "It was hard watching them work so hard at getting nowhere," Moline said of BentProp's efforts. "They'd see targets and dive those. They were not able to cover much area effectively."

It didn't take long for BentProp and the oceanographic teams to figure out they should join forces, and throw a Remus at the recovery problem. "Eric and I said, 'We could run a couple missions for you,'" Moline recalled in an interview in Palau in early April.

Scripps development engineer Myles Syverud helps collect a Remus autonomous underwater vehicle after a surveying mission. Daniel Terdiman/CNET

After both teams returned to the US following their 2012 Palau expeditions, they began serious talks about working together. Moline and Terrill secured additional ONR funding, with the goal of linking their scientific efforts to BentProp. They also brought on Michigan's Stockbridge High School -- and its robotics program -- as part of a science, technology, engineering, and math (STEM) educational program. In 2013, the groups converged on Palau, a set of specific airplanes in their sights.

The 2013 expedition was not a success. Since it found no American aircraft, BentProp on that occasion was unable to fulfill its core mission, which is to bring families of MIAs information about the fate of their lost loved ones. But the initial technology partnership led to the discovery of a sunken Japanese World War II float plane, and expanded in 2014 with oceanographers using a suite of technologies, such as 3D imaging sonar, LIDAR, advanced statistical modeling, and Autodesk 3D modeling software deployed on aerial drones. The 2013 effort, though, demonstrated "to BentProp and us that the interaction between the two groups would be beneficial," Moline said.

"Beneficial" may be an understatement. Within nine days of starting the 2014 expedition, the combined teams found the Avenger. Four days later, they discovered an F6F Hellcat fighter that BentProp had been seeking for at least 10 years.

Scannon was ecstatic. "To find two MIA sites in a single season is unprecedented in our experience."

'It's a blessing to know them'

For now the names of the planes remain out of the public eye. Notifying family members that their loved ones have finally been found is specifically not part of BentProp's purview. That job falls to the US military itself, and only after a meticulous recovery process by archaeologists and anthropologists from the Hawaii-based Joint POW/MIA Accounting Command. Official notification can take just a few months if dental remains are in good shape, or an average of 18 months if DNA is required to make a match, according to Bill Belcher, a JPAC archaeologist and forensic anthropologist who is also a BentProp member.

As for the planes, once JPAC has excavated them, they remain US military property but are left where they've been for the last 70 years.

That's just fine with BentProp, which exists for one reason and one reason only: finding the MIAs, no matter if it takes a week or more than a decade.

"They're searching for people they don't even know, that they're not related to, and they respect them," said Jo Schumacher, whose uncle Arthur Schumacher parachuted in 1944 out of the doomed B-24 Liberator at the heart of "Vanished," and who was captured and executed by the Japanese. "It's just indescribable the amount of effort, and time, and love, that they put into finding family members. I can't even explain it. It's huge. It's a blessing to know them."

Casey Doyle agrees. His grandfather, Jimmie Doyle, was on that same B-24, and died when it crashed into the sea. But until BentProp finally found it, in 2004, the plane's fate was unknown. Doyle's father spent decades listening to whispers from family members that Jimmie was alive and had abandoned him and his mother. "The discovery meant so much to my father," recalled Casey Doyle, who joined BentProp to "lend a hand." "It has totally changed the foundation upon which all his assumptions of who he is and where he comes from are based upon."

'For the fallen'

The Avenger found on March 24 was part of a torpedo squadron that took off from an aircraft carrier in the South Pacific in the second half of 1944.

The plane, which had retractable landing gear and tail-wheel, could launch from land or a carrier, and had a crew of three: a pilot, a bombardier-gunner, and a radio operator-gunner. From 1942 to 1945, the Avenger was the US military's main torpedo bomber. For Scripps' Terrill, helping find the Avenger had special meaning: His grandfather was manager of the paint and body shop at the Grumman factory in Tarrytown, N.Y., where it was built. "That was kind of a cool feeling," Terrill said, sitting in a Koror office in early April.

On a sunny March 31, with Terrill and his Scripps team standing alongside those from the University of Delaware and BentProp, Scannon started the ceremony that marks the beginning of the slow, methodical process that one day will lead to the military formally notifying the families of the Avenger's crew that they've been found.

In the late afternoon, the three teams stood in shadow on the Kemedukl. Two oceanographers held three American flags, and to their left, two Palauans held their nation's flag. Then, in a series of crisp, tight moves, BentProp members Casey Doyle and Derek Abbey (both US Marines, though Abbey recently retired from the service) folded the flags into thick, taut triangles before handing them, one after another, to fellow team member, and former Navy lieutenant commander, Flip Colmer, who will ensure they are given to the families of the airmen.

BentProp team member and former U.S. Navy Lt. Commander Flip Colmer holds the three folded American flags at the end of the March 31, 2014, ceremony for the airmen of the TBM Avenger found last month. Daniel Terdiman/CNET

"The open flags are symbolic of the sacrifices made by these naval aviators in defense of our country, and also the consequent sacrifices of the families of this aircrew," Scannon said. "The joint folding of the American flag and the Palauan flag is also representative of the close partnership between the American people and the Palauan people in making this day possible."

Everyone aboard the Kemedukl remained silent, though several people had tears in their eyes, as Scannon closed the ceremony by reciting a passage from "For the Fallen," a World War I poem by Laurence Binyon: "They shall not grow old, as we that are left grow old: / Age shall not weary them, nor the years condemn. / At the going down of the sun and in the morning / We will remember them."