Barrier maintenance takes a brake, protects joint assets

MISAWA AIR BASE, Japan -- In the event an aircraft has an in-flight emergency, hindering a pilot’s ability to land a plane, they engage with a barrier kit-12 arresting system with their tail-hook in order to come to a safe stop.

“Barrier maintenance refers to upkeeping the BAK-12 aircraft arresting systems,” said Staff Sgt. Ronald Mench, the 35th Civil Engineer Squadron generator maintenance NCO in charge. “These are a ground-based braking system designed for tail-hook equipped aircraft, such as the F-16 Fighting Falcon or the Navy EA-18G Growler.”

In Layman's terms, the pilot will drop the hook attached to the aircraft, so it will drag on the ground until it grabs a cable, forcing the aircraft to stop abruptly.

Lined with four sets of BAK-12 arresting systems, Misawa Air Base’s flight line provides emergency landing capabilities--effectively hooking a Viper and bringing it to a hault-- if any problem arise.

“Each set includes a physical barrier on each side of the runway connected by their tapes and a shared pendant on the runway,” continued Mench. “The pendant maintains two inches off the runway, allowing planes to engage it while kept under pressure, allowing aircraft to run over it.”

As the plane engages the pendant with the tail-hook, it pulls the pendant down the runway applying increased hydraulic brake pressure until the aircraft comes to a halt.

This capable system’s 65 million foot pound stopping capacity can be rewound in three to five minutes allowing up to 20 engagements an hour. It takes the dedicated Airmen of the barrier maintenance shop to inspect and fix any discrepancies.

“Typically, the maintenance we perform ensures the parallel barriers are synced,” said Senior Airman Kyle Gergel, a 35th CES aircraft arresting systems supervisor. “The sync ensures the barriers apply the same amount of hydraulic pressure to the brakes during the arrestment.”

Gergel said there are four stages of checks, ensuring the barriers are synced. They first bleed the brakes, confirming no air is in the system, then check that the control valve linkage is at .006 plus or minus .001 of an inch gap. Afterward, they start the engine and adjust the speed to 760 revolutions per minute plus or minus 20 and hydraulic pressure at 1,500 pounds per square inch and lastly, they perform a popping test to protect the hydraulic system if there is an equipment failure or a bad engagement.

“The test has us get the engine speed and pressure back to 760 RPM and 1,500 PSI,” explained Gergel. “We then pull the control valve linkage to the fully open position. We check the brake pressure gauge securing it at 2,700 PSI plus or minus 100, if it's in tolerance then the sync is complete, but if not, we adjust it until it’s at the correct tolerance.”

After running tests, the three-man team sets the barriers back up in the battery position, meaning it’s ready to be utilized in case an engagement is needed.

“If the two shacks were out of sync and one was braking faster than the other, it would pull the aircraft off the runway toward the barrier that was braking faster and probably crash,” said Gergel. “Also, if the syncs were not accomplished at all, the aircraft would pull the tapes out and never receive any braking causing severe damages to the plane and the barriers once there is no more tape to pull out.”

Due to the meticulous work put into maintaining and syncing these barriers, both Air Force and Navy pilots can rest assured they have the extra line needed in case of an emergency.