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ISO Docks keep C-130J fleet flying

Senior Airman Josh Thompson, 403rd Maintenance Squadron aerospace propulsion mechanic, checks for the next step during the process of removing turbine vibration sensors from an engine on a WC-130J January 13, 2019. The 403rd MXS is responsible for major inspections that take place on their isochronal maintenance docks. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Senior Airman Josh Thompson, 403rd Maintenance Squadron aerospace propulsion mechanic, checks for the next step during the process of removing turbine vibration sensors from an engine on a WC-130J January 13, 2019. The 403rd MXS is responsible for major inspections that take place on their isochronal maintenance docks. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Members of the 403rd Maintenance Squadron work on a WC-130 aircraft in the isochronal maintenance docks at Keesler Air Force Base, Mississippi.  Required routine inspections are performed to the maintain the aircraft's capabilities.  (U.S. Air Force photo by Senior Airman Kristen Pittman)

Members of the 403rd Maintenance Squadron work on a WC-130 aircraft in the isochronal maintenance docks at Keesler Air Force Base, Mississippi. Required routine inspections are performed to the maintain the aircraft's capabilities. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Tech. Sgt. Christopher Botts, 403rd Maintenance Squadron aircraft engine mechanic, works to remove a turbine vibration sensor from a WC-130J engine Jan. 13, 2019. Once removed, Botts will inspect the sensor, thoroughly clean it and reconnect it. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Tech. Sgt. Christopher Botts, 403rd Maintenance Squadron aircraft engine mechanic, works to remove a turbine vibration sensor from a WC-130J engine Jan. 13, 2019. Once removed, Botts will inspect the sensor, thoroughly clean it and reconnect it. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Senior Airman Landis Lee, 403rd Maintenance Squadron crew chief, prepares a tire for removal from a WC-130J  Jan. 13, 2019. This is a requirement that is performed during the routine inspections required to the maintain the aircraft's capabilities. (U.S. Air Force photo by Senior Airman Kristen Pittman)

Senior Airman Landis Lee, 403rd Maintenance Squadron crew chief, prepares a tire for removal from a WC-130J Jan. 13, 2019. This is a requirement that is performed during the routine inspections required to the maintain the aircraft's capabilities. (U.S. Air Force photo by Senior Airman Kristen Pittman)

KEESLER AIR FORCE BASE, Miss. --

Like cars need regular maintenance such as oil changes, tire rotations and tune-ups, so do aircraft.

For the Air Force Reserve 403rd Wing’s fleet of 20 C-130J Super Herclules at Keesler Air Force Base, Mississippi, there is no quick oil change service for aircraft and it is not physically possible to maneuver one up to the service station located next to the mini market to make sure everything is up to standard.

To maintain standards and keep aircraft for the 53rd Weather Reconnaissance Squadron Hurricane Hunters and the 815th Airlift Squadron Flying Jennies mission ready, the 403rd Maintenance Group employs the use of their isochronal maintenance docks.

On the outside, the ISO docks look like a warehouse, but on the inside it looks like a construction zone or a scene from a movie, except it’s a 40-ton aircraft surrounded by hardworking Airmen and instead of ropes, the aircraft is flanked on all sides by elevated platforms, lights and various tools.

The docks provide space to inspect and maintain aircraft through three phases of what Master Sgt. David Workman, 403rd MXG ISO dock supervisor, said are called letter checks.

Simply enough, the letter checks go by A, B and C, and increase in degree of meticulousness as each one is performed, said Workman. Aircraft go through these checks in order with 270 days between each one.

A-checks are fairly superficial inspections. Lasting only five work days, Workman said these are “glorified BPOs” or basic post-flight operations inspections. Ideally, as many people as are available perform these, but the job can be done with one crew chief and one ISO technician.

The next letter check is B and this is when the crew gets more in-depth with their inspection, spending 18 days on it. Workman said in this phase they do things such as check the landing gear and there is a greater emphasis on checking the engines to search for popped indicators which alerts the Airman working on it to take action.

“The C check is the most in-depth check we do,” said Workman. “We’re pulling leading edge access panels, the bread baskets behind the engines come off, and all the hydraulic filters are changed.”

Workman said the list goes on and on for what Letter C checks consist of; thus, these intrusive checks require the aircraft to remain in the ISO dock for 22 days.

For letter B and C checks the required manpower is more demanding. There is an Airman per area, of which there are five, four Airmen for the engine, two hydraulics troops, and three electricians, and all of these are either Air Reserve Technicians or traditional reservists.

In the event that the inspecting crew finds something amiss, a discrepancy document is filed, parts are ordered, and it is then, depending on how serious the issue is, determined whether the aircraft is grounded or limited in its mission ability.

Though it is uncommon, the 403rd MXG has supported other units’ needs by providing their docking facilities, said Chief Master Sgt. Christopher Linthicum, 403rd MXS superintendent. One example is the Connecticut Air National Guard performed inspections on a couple of their Legacy C-130s while their facilities were under maintenance.

The ISO docks and those who man them are crucial to the 403rd Wing’s flying missions, as they provide preventive care, and if a letter check does not get done, the aircraft is grounded, said Linthicum.

“The main purpose of the ISO is to have scheduled inspections to minimize unscheduled downtime between letter checks and ultimately improve the life-span of our aircraft,” said Linthicum.