Last December, a KC-135 Stratotanker aerial refueling jet out of MacDill Air Force Base was forced to shut down one of its four engines during a flight over Florida.
No one was injured, and the aging plane, which rolled off the assembly line when John F. Kennedy was president, landed safely.
But Air Force Col. April Vogel, the base commander, wasn't taking any chances. She immediately ordered inspections of each of MacDill's 16 tankers, shared and maintained by the 6th Air Mobility Wing and the 927th Air Refueling Wing. It took crews working 12-hour shifts three months to complete the inspections on the aircraft, valued at a total of nearly $1 billion.
Such efforts highlight the challenges MacDill crews face trying to keep the KC-135s in the air at a time when they are flying nearly 2 1/2 times their scheduled hours fleet-wide, largely as a result of the ongoing fight against the Islamic State.
Every five minutes, tankers like the ones at MacDill refuel an aircraft heading to strike ISIS. Overall, they made more than 110,000 refueling flights last year just in the U.S. Central Command region alone, according to the Air Force.
Each tanker carries a maximum of 200,000 pounds of fuel, enough to fill the average car about 2,500 times. It's delivered midair via an extending boom at the back. MacDill tankers fly 19,000 hours and deliver 186 million pounds of fuel to about 14,000 aircraft every year.
All that flying gas delivery takes a toll on MacDill's 600-plus aircraft maintenance personnel, who know their task can have fatal consequences.
So far, their work has paid off. No MacDill tanker has ever crashed. And though they are old, the jets' safety record actually has improved through the years. There's been just one fatal Stratotanker accident across the entire fleet since 1999, a 2013 crash in Kyrgyzstan that killed all three crew members.
"These are antique aircraft," said Capt. Jessica Brown, a spokeswoman for the 6th Air Mobility Wing. "But they are still very much capable because of the airmen tasked with keeping them relevant. Failure is not an option."
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On a blistering Friday afternoon, seven Stratotankers — nearly half of MacDill's fleet — are lined up on the flight line.
The base clock thermometer shows the air temperature is 95 degrees, but the sun reflecting off the flight line makes it seem even hotter. And hotter still inside the parked tanker jets when the air conditioning systems aren't running.
High above the surface, sweating members of the 6th Aircraft Maintenance Squadron are perched in a bucket, making repairs to a navigation system. Elsewhere on the flight line, a Stratotanker is missing a landing gear door. The story of its repair illustrates the challenges of fixing things on airplanes that were made between 1957 and 1964.
The door had loose rivets, according to Master Sgt. Roger Mitchell, the squadron's lead production superintendent. When it was brought into the shop, crews found that the rib underneath the surface was cracked.
From a purely technical standpoint, it would be relatively easy to take off the sheet metal, repair or replace the rib and cover it back up again. But this is the Air Force, and nothing is ever simple.
The landing gear door rib is one of many items on the Stratotanker that requires permission from a higher headquarters to repair. That takes time. So would finding a spare rib from one of the many bases that might have one. To save time, the wing just ordered an entire new door assembly.
It's a matter of quality assurance, said Maj. Ryan Garlow, commander of the 6th Aircraft Maintenance Squadron.
"Before you are allowed to make something that goes on an airplane, we have to make sure the Air Force is willing to take that risk," said Garlow, a pilot whose grandfather also flew Stratotankers.
Not every maintenance job involves fixing things.
Near the northern end of the flight line, crews give one of the Stratotankers a good scrub-down. It is a routine procedure, usually carried out by the newest airmen, to battle some of the Stratotanker's toughest enemies — Florida's highly corrosive salt air and scorching sun.
It's such a big problem that every couple of years, Air Mobility Command moves Stratotankers from base to base to help reduce the corrosive effects.
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The following Monday, a Stratotanker built in 1961 fills the cavernous Hangar 2.
Airmen peer into cracks and crevices. They check hundreds of nuts and bolts and tube fittings. They even remove the jet engines' 44 fan blades one by one, after numbering each one so they fit back in perfect balance.
As maintainers work inside a wheel well, a laptop sits atop one of the jet's landing gear so the airmen can check schematics and find out which parts they can fix themselves and which require permission from someone higher up.
While the wing command sends at least a few maintainers overseas to keep planes flying in a war zone, there is some work that can be performed only at MacDill.
This 900-hour inspection is one of those jobs. It is expected to take two shifts of 12 people each about a week to complete. There is an even more thorough 1,800-hour inspection that takes nearly three weeks.
It can be arduous, dangerous work.
"Almost everything we do is dangerous," said Lt. Col. Leah Vanagas, commander of the 6th Maintenance Squadron. "Of course, these are flying gas stations."
Repairing the problem that led a crew to shut down one of the Stratotanker's engines in December is a good example of the dangers, Vanagas said.
The suspected problem: Specialized coating on a wing fuel tank came loose, clogging up the engine. The inspections took three months of crews working 12-hour shifts. At one point, one of the airman's breathing masks failed and he had to be quickly extricated from the tight confines of the Stratotanker's wing tank because of deadly fumes.
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The KC-135 Stratotanker was made by Boeing, based on the manufacturer's 707 civilian airliner. There are 414 in the inventory, and they are expected to continue delivering fuel, evacuating the injured and carrying cargo until about 2050. That's when they are all scheduled to be replaced by the new KC-46 Pegasus and future airframes still in the concept phase.
In addition to the current roster of 16 jets, MacDill will begin receiving eight additional Stratotankers starting this year and is in the running for another dozen. Keeping them flying is a complicated juggling act, moving aircraft, crews and parts around the world while ensuring they are safe and able to perform missions.
"We've been at it for 15 years," Vanagas, the squadron commander, said of the frantic pace of operations. "It's been very busy and it won't be ending any time soon."
Contact Howard Altman at firstname.lastname@example.org or (813) 225-3112. Follow @haltman.