MAKAPU'U — It was April 5, 1942, four months after the Pearl Harbor attack, and a Navy flight crew of nine men patrolled the waters off O'ahu.

The weather was bad — rainy, windy, with poor visibility. They had flown more than 12 hours on a long-range patrol, searching for enemy subs and ships.

The crew was aboard one of four Navy planes that flew out of Kane'ohe Naval Air Station that day. One returned to Kane'ohe before the storm worsened. Another went to Kaua'i, and a third touched down at Pearl Harbor. But the crew of the PBY-5A "Catalina" was dangerously off course.

In their confusion, the crew mistook the lighthouse beacon from Makapu'u for the Barbers Point lighthouse.

The plane slammed into the hillside 200 yards south of the Makapu'u lighthouse.

All nine men died in the crash, which has remained shrouded in obscurity.

At the time, the Islands were under martial law and the military didn't report such accidents to the newspapers, said Colin Perry, a historian with the Hawai'i Aviation Preservation Society. During the war, there were crashes almost daily on O'ahu. From 1942 to 1945, there were about 800 aviation deaths on the island, Perry said.

"No one has ever done anything for these men," he said.

The preservation society doesn't want those deaths forgotten. After months of planning and working with the state Department of Land and Natural Resources, the society has obtained permission to erect a granite monument listing the men's names and ranks.

The monument marker will be installed at the site Wednesday.

At first, the society didn't know the home states of the Navy men. That information came from WFI Research Group, an Internet aviation database of more than 700,000 World War II aviation and at-sea casualties.

To this day, one can find some rusted-out landing gear, engine parts, and small pieces of metal at the crash site. The society was able to determine the type of plane by matching aircraft data plates found at the site, said Perry, a retired Air Force and airline pilot.

"I've looked at all the archive stuff in Washington, D.C., and in Florida (the Naval Air Museum in Pensacola), and the only documentation I've found is the War Diary that gave the account of the crash," he said. (The War Diary is a military log documenting World War II flights).

But with the strict wartime censorship that was imposed on the media and personal mail, there isn't much information on these military crashes.

The Navy plane wasn't even the only one to go down that night. An Army plane crashed into the Pali, killing all 10 aboard. The preservation society plans to place a granite marker at that site next year.

The small group that makes up the Hawai'i Aviation Preservation Society has worked for the past eight months to mark the spot at Makapu'u. The society is responsible for other such markers along the 'Aiea Loop Trail, the Pali Lookout and the Honouliuli Contour Trail and at the former Barbers Point Naval Air Station.

No date has been set for a dedication, but the group hopes to have a Navy chaplain say a prayer for the men who died.

"They died in obscurity," Perry said. "It will be nice to know that someone doesn't forget."

Reach Suzanne Roig at sroig@honoluluadvertiser.com.