C-130 News: Mystery solved: Keesler AFB team solves riddle of illness aboard C-130

casey · April 10, 2015

BILOXI -- For years, a strange problem with the U.S. Air Force's C-130 aircraft had pilots and crews reporting sickness, discomfort and, in some cases, excruciating pain after routine flight missions. The phenomenon remained a mystery until February, when a handful of reservists at Keesler Air Force Base took the initiative to solve the mystery. They made a tiny discovery that's affecting airplanes worldwide.
The problem was with the pressurization system on the C-130 Hercules -- the longest-produced and perhaps most-popular aircraft in military history. The versatile airplane serves as an attack gunship, a troop transport, a surveillance plane and many other roles.

Keesler's famed Hurricane Hunters fly the C-130J for weather reconnaissance.

In February, maintenance technicians from the 403rd Wing began a hunt for a solution to the problem. At times, the C-130s' pressurization systems could not be controlled manually or automatically. Cabins would over-pressurize at certain altitudes, causing the physiological problems.

The health effects typically surfaced after the flights. Crew members were on the ground yet still felt as if they were in the air, Tech. Sgt. Fernando Betancourt said.

The effects were mostly minor but had the potential to be severe.

"It can be dangerous," Tech. Sgt. Vincent Hawkins said. "We've had people that had nasal-cavity problems, ear problems, excruciating pain."

Some would vomit, and others experienced pressure buildup in their eye sockets, Hawkins said.

"Flight crews were constantly writing it up, which basically grounded (the affected) airplane every time,"
Master Sgt. James Rials said. "It could cause excruciating pain to the point you can't function."

The technicians noticed something strange. They were finding tiny metal shards in the pressurization system's air lines.

'It would mask itself'

As similar reports and findings mounted over the years, airmen tried every repair listed in the maintenance manuals. The problem would usually go away for one or two flights, then return.

They even collected the metal particles and gave them to Lockheed Martin, the C-130's manufacturer, hoping the company's engineers could find their source.

But no one had any answers.

"When the book failed us and didn't tell us what the problem was, we just went with experience," Hawkins said. "We had to think outside the box."

Because they try not to keep planes grounded for more than a day or two, Rials, Hawkins and Betancourt decided to put together a team. They spent two days stripping the pressurization system off one of 403rd Wing's planes and inspecting each part.

"We changed parts from the tail to the nose," Rials said.

It took 500 man hours and disassembly of about 65 percent of the system before they made the crucial discovery. The metal particles were coming from a corroded rivet, no larger than a pencil point, inside an air valve.

The corrosion had remained hidden for years because every other part of that valve is stainless steel. But not the tiny rivet, which is composed of plain pot metal -- an inexpensive, low-quality alloy.

Moisture in the air could cause the rivet to rust and fall apart. Whenever the pressurization system was used, the air in the lines would push the metal particles to another valve at the very front of the system. Maintenance personnel sometimes found them there but couldn't work out where they came from.

Often, technicians would receive a maintenance order but when they inspected the system the particles had moved, causing the blockage to disappear. They would move again on a later flight, creating a new blockage elsewhere in the air line.

"It was one of those things you just could not find," Rials said. "It was so insidious, it would mask itself."
'And no one knows'

Problems with the C-130J's pressurization system cropped up after 2004, when Lockheed Martin implemented field installations of new check valves, Rials said.

As no one seemed to know the valves contained rivets prone to corrosion, they weren't part of regular fault-isolation manuals used by maintenance crews for troubleshooting.

Because of the work done by Keesler's 403rd, however, Lockheed Martin is expected to update the manuals. It's a victory for the often-overlooked role served by maintenance teams in the military.

"Once that information makes it to Lockheed, then it goes out worldwide," Hawkins said.

The rust-prone rivets were not on just a few airplanes.

Keesler's 403rd has already replaced the valves on 13 of its 20 planes.

Every unit in the U.S. Air Force with a C-130J will now be performing regular inspections of the valves, and other nations that use the plane will more than likely follow suit, Hawkins said.

"When you do something like this, the changes go to so many different people throughout the world," he said. "And no one knows."