From the latest issue of Combat Aircraft:
When someone asked him in May what his organization’s biggest equipment need was, U.S. Navy Vice Admiral Robert Moeller, second in command of the new U.S. Africa Command, didn’t hesitate: Airlifters, he said. Africom “will need a whole lot of air support.”
In a world increasingly wracked by small wars and insurgencies – and increasingly vulnerable to natural disasters and the mass movements of refugees – the ability to move people and supplies quickly and efficiently is more important than ever. The U.S. military’s fleets of transport aircraft – more than 1,000 strong – is one of its most important resources. Indeed, in May, American transport crews were among the first responders to both the devastating cyclone in Burma and China’s killer earthquake.
But these vital airlift fleets face major challenges across the board. The Air Force, which overseas maintenance for all the service’s cargo planes, has had to get creative in finding ways to keep hard-working aircraft flying well into old age.
The mammoth C-5 Galaxies, built in two batches in the 1970s and 1980s, suffer readiness rates as low as 50 percent and are badly in need of new engines and avionics. In February the Pentagon decided to re-engine only the roughly 49 younger C-5B and C models, at a cost of $8 billion, while inching forward with a planned avionics overhaul for the entire 111-strong fleet.
The smaller C-17 Globemasters are only a few years old, on average, but have piled on hard flying hours over Iraq and Afghanistan. Despite this, Congress is considering shutting down the Boeing factory that builds the jets, in order to save money for new fighters and tankers.
In the lightest weight class, a plan to buy small C-27J Spartan two-engine airlifters for the Air Force and Army is moving slowly, with money authorized for just seven in 2009, all for the Army. The C-27Js are meant to help take the strain off the military’s most numerous and hardest-working cargo plane, the middle-weight C-130 Hercules, built by Lockheed Martin.
Old Herks Need Love
The U.S. military has been buying C-130s almost non-stop since the mid-1950s. “Tails” from the ‘60s and ‘70s – E-models and early H-models, respectively – still comprise a large proportion of the roughly 600-strong fleet, 500 of which belong to the Air Force and the rest to the Navy, Marine Corps and Coast Guard. The latest-generation C-130Js, with new six-bladed Rolls-Royce turboprops, have had serious teething and performance problems that delayed their full introduction into service. It wasn’t until late 2006 – a decade after the first C-130J rolled off the assembly line – that the type achieved full combat capability. This spring the Pentagon floated the idea of a new multi-year purchase of 64 J-model Hercules at a cost of $60 million apiece. These Js will join some 200 ordered previously for U.S. forces.
The J’s slow progress means old C-130Es and Hs will have to soldier on for years to come. To keep the old warhorses’ “front offices” up to date, Boeing is developing the Avionics Modernization Program, or AMP, which will replace up to 13 different Hercules cockpit configurations with a common avionics suite comprising “glass” displays and new computers. But AMP, like so many airlift programs, has suffered major delays and cost increases since it began in 2001.
Last year AMP’s cost ballooned 25 percent to $4 billion, an increase that mandated a Congressional inquiry. To save money, and the program, the Pentagon removed 170 older C-130s plus Special Operations models from the AMP plan, leaving just over 220 to get the full cockpit overhaul. The first AMP bird, a C-130H, in June 2008 belatedly completed the 100th of 200 test flights. The program should enter low-rate production in 2009, years later than initially planned.
The news is somewhat more encouraging in a parallel effort to revitalize old C-130s’ airframes. That work has only gotten more urgent in recent years as structural cracks have grounded a dozen older C-130s and placed around 30 others on tight restrictions. At two sprawling depots – Ogden, located at Hill Air Force Base in Utah; and Warner Robins in Georgia – more than a thousand technicians tear apart, repair and rebuild up to 90 U.S. military C-130s every year, sending them back to the Air Force, Navy, Marine Corps and Coast Guard flying squadrons with stronger wings, less corrosion and a number of structural upgrades that should keep them flying – and largely off restriction – until enough new J models enter service to replace them.
It’s far from glamorous, but with airlifters in increasing demand, the work going on at these depots is some of the most important in the U.S. military.
U.S. C-130s undergo “programmed depot maintenance” on average every 69 months at either Ogden or Warner Robins, according to Rich Hornick, an official at the Warner Robins depot. Exactly how long each bird spends in maintenance depends on the owner’s requirements – work on Navy Hercules usually lasts around 130 days; Air Force Herks typically stick around for 160 days – and on the condition of the individual aircraft.
Regardless, the process is largely the same for all the planes, according to John Grubb from the Ogden depot.
“A standard package runs 17,000 to 20,000 hours of maintenance on an aircraft,” Grubb says. “We de-paint it chemically after it’s brought out to Hill Air Force Base [or Ogden] and de-fueled to make sure it’s safe. We do a ‘strip and inspect,’ stripping components off – and during that time period, we will have mechanical inspectors looking at the aircraft, guided by work control documents, looking for corrosion, cracks and defects. Once that’s complete, we can get into the repair portion – sheet-metal repair. There are work control documents generated for mechanics to repair any of those defects …
“The last portion is putting the aircraft back together, then testing for airworthiness. Once production is complete, we hand it over for the flight testing. We put fuel back on the aircraft, paint it for a week to 10 days, check it, run the engines and then perform approximately two test flights where pilots will go through a flying profile and make sure all systems are functioning.”
In the last decade, C-130s have worked harder than ever, and that’s having an effect on the depot work. “Air National Guard and Reserve C-130s, prior to 9/11, would fly 400 to 450 hours per year,” Hornick says. “Now some mission profiles fly up to 900 or 1,100.”
More flying – plus advancing age – means new maintenance problems. “A couple issues from aging aircraft are the center wing box, where the outer wing connects to the center wing, in addition to what we refer to as the ‘rainbow fitting,’ where the outer wing box attaches to the center wing,” Hornick explains.
“Another area is corrosion,” Grubb adds. “We’re seeing more corrosion, which increases the time spent in sheet-metal production.”
Many aircraft are reaching the 38,000 flight hours, at which point certain restrictions on load weight and flying profile kick in. A special inspection is also required to lift the restrictions, according to Hornick. It “consists of inspecting the lower surface of the center wing box. Basically what we’re doing is removing the fasteners from the panels. Any damage found is ID’ed to engineering and either given a fix or we recommend that the aircraft is not economically able to be fixed. Then the decision is made by the major command whether we do the repairs, which restores the aircraft to full flight status until it reaches 45,000 hours. At that point, that aircraft is grounded until we either put in a brand-new center wing box … or the aircraft is retired.”
Some maintenance needs were less predictable. “Peeling polyurethane, that’s recently become an issue starting in 2006,” Hornick says. “It’s an issue with the way the polyurethane was applied during production inside the fuel tanks. The process had changed in the late ‘80s on how they applied that polyurethane in the tanks: it created an overspray when they started to spray it on instead of brushing it on. Because of the overspray, there’s peeling, and the polyurethane has to be removed from the tanks, or one of the after-effects is you could start to contaminate the filters.”
The new polyurethane fix, Grubb says, alone has increased the average maintenance requirement by up to 1,200 hours per C-130.
Learning from the Airlines
To deal with the mounting workload, the depots are investing in new equipment, and looking at entirely new maintenance processes based on commercial airline practices.
“Eighteen months ago we decided to invest dollars in building permanent work-stands for mechanics,” says Doug Neel from Ogden. “They back the aircraft into these stands. It takes away the need to push around work-stands or man-lifts. We’ve improved non-destructive inspection technology – we’re doing ultra-scanning now. There’ve been a lot of improvements in he last four or five years.”
Grubb says Ogden just added a dedicated maintenance building – Number 680 – just for C-130s. “That’s a huge improvement to our capability to produce aircraft.”
But the depots can get even more efficient by adopting commercial maintenance practices, Hornick proposes. This includes “condition-based maintenance.” “Right now what we do is base the depot maintenance schedule on given amount of time, computed in months. On average every 69 months a C-130E or H comes in for programmed depot maintenance. … With condition-based maintenance, you look at factors to determine if that’s the right time. Some factors are … were you deployed to a saltwater or sand environment?
“Another thing we’re looking at is high-velocity maintenance,” Hornick adds. “It’s more how airlines perform their maintenance, bringing an aircraft in more frequently but for shorter amounts of time – 20 to 25 days, tops. You have the parts waiting when the aircraft arrives. If there are safety-of-flight issues, obviously they get fixed. But if there are things that can wait until the next check, they put it off.”
One way or another, the depots must find ways to contend with airplanes that are getting older while working harder and harder performing important missions that aren’t going away any time soon. “We recognize that the C-130 is a key piece of equipment that the military needs to prosecute the ‘War on Terror,’” Grubb says.
(Photo: BW Jones)
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