DOVER AIR FORCE BASE, Del. — “Smoke in the cockpit! Smoke in the cockpit!” the flight crew yells in unison. Then the dreaded radio transmission goes out: “Declaring an IFE (in flight emergency); request immediate return to base for landing.”

Moments before the troubling exclamations occurred, the flight crew of the massive C-5M Super Galaxy was settling into their duties after taking off from Dover Air Force Base. Conversations had waned as each crewmember focused on mission tasks at hand while taking the aircraft for its first functional check flight since undergoing isochronal (heavy) maintenance at Dover. And then it happened; smoke in the cockpit … again.

An IFE is not the way anyone wants to end a flight, especially after the aircraft has been cleared to fly by maintainers hours before.

John Greim, a 436th Maintenance Squadron isochronal maintenance dock controller, said each time a post-maintenance test flight came to an end like this, the maintenance troops would spend sometimes more than 700 hours troubleshooting the problem and would inevitably come up empty-handed.

If the smoke in the cockpit problem occurred immediately after departing from Dover AFB, the aircraft would return here. In some cases it happened closer to the aircraft’s home station and the aircraft would land there; then the home-station maintenance troops would begin to track down the problems.

It seemed there were smoke phantoms lurking in the planes and they were doing all they could to remain hidden.

In 2014, the problem was occurring repeatedly after aircraft came out of ISO maintenance; when the Air Force C-5s undergo the most intensive maintenance outside of depot-level maintenance. Dover is the sole location within the Air Force where the C-5A/B/C Galaxy and C-5M fleet undergo ISO maintenance. Each C-5 comes through Dover approximately every eight years to allow preventative maintenance, as needed, and as required maintenance to be accomplished on the aircraft and components. During ISO, the C-5 is essentially stripped, inspected and repaired and then put back together again to accomplish its airlift mission around the globe.

Troubleshooters with the 436th MXS, led by Master Sgt. Michael Childers, the 436th MXS ISO production supervisor, determined the smoke phantoms were being introduced to the airplanes during ISO, but not through a flawed process or other nefarious ways, but through prescribed maintenance practices.

This problem troubled the maintenance personnel, and Childers especially, who takes great pride in delivering the aircraft in mission capable status.

“It was concerning to all of us here,” Childers said. “It looked bad on our ISO processes; it looked bad when other maintainers at another station had to work on an airplane to troubleshoot this problem after it had been here for a period of 45 to 50 days. We had to figure out what was going wrong and come up with a fix.”

Childers said the flight crews who experienced the problem said the smoke had a smell of burning petroleum. Efforts to pin-point the source of the smoke were intense with reviews of countless items from ensuring technical orders were being performed correctly, use of the right oil and lubricant products and trying to find where and how the petroleum was burning to create the smoke.

“We finally troubleshot it down to the MC-7 air cart,” Childers said.

The MC-7 air cart is the manufacturers prescribed equipment to be used for aircraft pressurization checks. The MC-7 is an industrial air compressor that provides high-volume, low-pressure air and is similar to large air compressors used in construction to power jackhammers and sandblasters. These machines are designed to add small amounts of aerosolized lubricants for the air tools they generally run.

“The reason why the MC-7 was causing this problem is because they were designed for air tools,” Childers said. “So, it put oil into the lines. The oil ended up getting into the duct work and causing smoke in the cockpit.”

The problem would not appear on subsequent flights because the oil had already burned off.

So, how did they fix the problem?

They fixed it by taking decisive action to come up with an in-house solution for less than $1,000. Childers teamed with dock controller Greim and Master Sgt. Jason Smith, assigned to the 512th MXS, to identify potential solutions, parts and supplies available and then produced a prototype for testing.

Childers said the entire length of time from pinpointing the source of the problem to having a working fix took about two weeks.

The system, which has been dubbed the Childers Filtration System (CFS), was created using a repurposed wheeled cart and has a set of two filters through which the air from the MC-7 cart passes. The first filter is a large particle filter, which is connected in sequence to a second fine particle filter. From there, the now contaminant-free air flows to the pressure gauge and finally to the aircraft. The cart has two separate sets of filters.

Smith repurposed an unused cart originally designed for storing wrapped hoses by mounting an aluminum sheet vertically to allow hardware to be mounted. The design team kept the concept simple to prevent it from being hooked up incorrectly.

“It was important to us that this is easy for a maintainer to walk up to and connect,” Greim said.

After building the system, they went about testing it by running the MC-7 cart for a short period.

“After running for 45 minutes, there were a couple ounces of oil that were picked-up and removed from the system,” Smith said. “They knew they were on the right track. They then conducted a second test for a period of one hour during which almost a half-gallon of oil and water mix was removed. A remarkable affirmation the system worked as designed and would eliminate the problem.”

The next major step to putting the CFS to use was filling out paperwork to obtain official approval to use it on an aircraft. A ‘Request for Engineering/Maintenance Assistance,’ known as a 107, was sought for C-5A, serial number 70-0456, in June 2015. After approval was received from Air Force Life Cycle Management Center at Robins AFB, Georgia, the system was validated and resulted in no smoke in the cockpit after the aircraft was release from ISO dock.

The CFS has been in use on every aircraft rolling through the ISO process since then. A blanket approval has been obtained from AFLCMC and the 107 reads, until the tech data is changed.

Childers, who has retired since the CFS received initial approval said, “It wasn’t just me. It was a team effort.”

Greim does not let Childers share the credit so easily by insisting, “He was steering the boat.”

Finalized changes to technical orders are in the works and have the potential to prevent other problems not just for the C-5 fleet, but across the entire Air Force where the MC-7 cart is mandated for similar use, Greim said. This will eliminate future smoke phantoms from appearing.

“Since the introduction of the Childers Filtration System there have been no recurrences whatsoever. It has definitely fixed the problem,” Greim said.