Trading Downtime for Burn Rate

Written by Henry Canaday

MLF 2010 Volume: 4 Issue: 1 (February)

 

The basic tactic is thus to trade downtime, the amount of time aircraft on the ground and unavailable for operation, for burn rate, the number of mechanics who work simultaneously on the aircraft, moving it through program maintenance quickly. Fewer jets on the ground means more capability in the short term and lower acquisition costs over the long term.

But putting this tactic into practice is complicated, and substantial up-front investment must be made, so it is most justified for fleets that will remain in service for a long time. Although HVM can be applied to many aircraft, the Air Force is thus concentrating first on HVM for the C-130J at Warner Robins Air Logistics Center, the B-1 at Tinker ALC and the F-22 at Hill ALC.

HVM is already being tested on C-130Js at Warner Robins. “We are trying to bring in best practices from commercial maintenance and use a mechanic-centric focus to increase the daily hours of touch labor,” summarized Jerry Mobley, chief engineer on the HVM team. “The Air Force keeps 200 aircraft on the ground at all ALCs,” adds team member Doug Keene. “Commercial aviation gets very high availability, sometimes more than 90 percent, while we are significantly lower than that. If we can reduce downtime, we will need to acquire fewer new aircraft.”

HVM planning began three years ago with three goals: understanding the airplane, ensuring it was ready for work, and getting that critical burn rate up. For example, putting 50 mechanics on an aircraft for eight hours a day yields a burn rate of 400 hours per day. “Some commercial shops put 100 to 110 people on an airplane for a couple shifts per day,” Mobley noted. “We generally [had] around 20 people on the airplane.”

The key is not hiring more mechanics, but planning and synchronizing their work. And that requires thorough preparation in three areas: knowing the condition of the aircraft, having tools and equipment ready, and having a plan for choreographing the work itself.

The old system has scheduled program depot maintenance (PDM) on C-130s once every six years, while the Air Force did isochronal inspections to assess conditions and identify future work in the field every 450 days. Under HVM, PDM is broken up into four visits at 18-month intervals, the first on fuselage, the second on wings, the third on the tail section and the fourth on flight controls. During each of these HVM visits, the ALC itself will do isochronal inspections on other sections of the airplane.

Isochronal inspections are essential to understanding the airplane and thus to HVM. “Some people said you can’t do that without opening the whole aircraft up,” Keene noted. “But if I can use bore-scope and visual inspections to identify 40 to 60 percent of the damage, I can order the right parts 18 months out. Before, we just had the probability of needing a part. Now that probability can be 0 or 100 percent.”

With two C-130Js through their first fuselage visit, Warner Robins is now validating its HVM concept. The validation phase will continue through 2010 with a third fuselage visit in late January, followed by two visits each on wings, tail section and flight controls.

Early results are encouraging on two fronts. Planners understood the condition of C-130J fuselages prior to the visit very well. “We have not had any major findings that we did not anticipate,” Keene said. Its kits of tools, equipment and parts were also ready. But on the third item, task planning, there is more to be done. “Our standard daily tasks did not work so well,” Keene acknowledged. “We tried to combine the normal PDM with the isochronal inspection and we duplicated some work.” Another problem was that not every operation was ready. “When we got out of sequence it was hard to re-sequence.”

Under traditional PDM, the burn rate has been about 125 to 145 hours per day of touch labor. Mobley is shooting for 500 hours per day under HVM. “That will reduce time in hangar and number of aircraft in hangar by half or more,” he predicted. Keene said the biggest challenge remains getting the choreography of daily tasks right. “We do not need more equipment and tools, we need to get the right parts and tools to the mechanic at the right time. You never want him to walk away from the airplane to a tool crib or a technical order library.”

He argued that this should be possible because most maintenance is predictable. “There is not much variability in taking an aircraft apart and putting it back together. There is even less variability in doing repairs.”

Warner Robins has a number of information systems to support HVM. Mobley says these will eventually need to be more integrated. Moreover, “we do need a more robust fleet-scheduling system pretty quick.”

Mechanics need new training for HVM less than do the engineers, planners and schedulers who support them. These staff must develop their instructions, plans and assignments in much more detail for HVM than they have under traditional maintenance. And they must collaborate much more closely. “Instead of throwing it over the wall, they must work in the same room,” Keene said.

Engines are not repaired at Warner Robins, except for isochronal inspection and some line work. But HVM team member Shelby Purser argued that the HVM concept applies in principle to all aircraft components, including engines. And HVM can apply, in principle again, to any weapon system, whether aircraft or non-aircraft.

Mobley’s big lessons so far have been these three: “It doesn’t go as fast as you hope. Mechanics welcome it. And parts are less of an issue than getting the standard daily work right.”

“We were with the Air Force every step of the way,” explained Tom Wetherall, deputy vice president for business development for global sustainment at Lockheed Martin. Lockheed added its expertise and technical data to the Air Force’s experience in operating and maintaining the C-130Js to support the HVM effort.

Unlike the older C-130B/E/Hs, the J has a structural health monitoring system, which makes the predictive part of HVM easier. That is one reason the Air Force started HVM with the new Js, but it plans to back-fit HVM to older models as well. Experience and more inspection will likely have to replace some heath monitoring results on these older models.

At present, the Air Force is doing all the HVM trial maintenance on C-130Js. If the service needs to outsource HVM maintenance when the approach goes into full production on all C-130s, Lockheed will submit bids for this work, along with 12 other firms that have qualified for FAST-2 [Flexible Acquisition and Sustainment Team] bidding. As the manufacturer of the F-22, Lockheed expects to be similarly involved as HVM is developed at Hill on this platform. And Wetherall said HVM is also applicable to other C-130J customers around the world, which is an advantage. Lockheed thinks smarter maintenance practice could make acquisition of C-130Js more attractive to many customers.

TINKER READIES HVM FOR B-1

HVM planning on the B-1 kicked off a year ago at Tinker, according to HVM team leader Lieutenant Colonel Richard Buckley. PDM has been done on the B-1 every five years. Under HVM, it will be done in phases every 15 months.

“We started hard-core work in September 2009,” Buckley said. Preparatory work has included mapping events in current processes, standardizing daily operating processes, progress tracking, developing metrics for planned versus executed work and training first-line supervisors on the HVM approach.

The B-1 HVM team has acquired emergency-procurement capability so it can order parts quickly when unexpected events are encountered. It is now defining the functions of the maintenance team in resolving unexpected issues. It is also establishing a kitting area for point-of-use kits. “We have cleaned out a cage area, will have our first kits in February and by October should have 100 percent of the kits on the shop floor,” Buckley explained.

Field managers on the HVM team have identified the top 25 drivers of maintenance on the B-1 that they want to see field kits developed for, and they have submitted these to the Defense Logistics Agency. Buckley expects field kits will be on the flight line by the second quarter of 2010.

Tinker will induct its first B-1 for inspection in February, then start prototyping HVM in October 2011 and plans to deploy it in Fiscal 2012. As with C-130s, HVM will divide work into four checks, one for landing gear, one for ejection pads and the other two allocated generically to even out work flow, man-hours and use of skill types. Isochronal inspections will be built into these phased HVM checks.

Also as for C-130s, a key objective is to get burn rate up. It has been 145 to 150 hours per day under traditional PDM at Tinker. Aided by moving from two to three shifts a day in Fiscal 2011, Buckley wants to ramp up to 400 hours per day.

Boeing has been supporting Buckley’s B-1 HVM team. Mahesh Reddy, Boeing’s B-1 program director, sees the basic philosophy of HVM as changing unscheduled maintenance into scheduled maintenance and using mechanic-centered processes to do this maintenance. Merely changing unscheduled to scheduled maintenance will save a lot of downtime. Reddy estimates that, overall, 86 percent of maintenance events in military aviation are now unscheduled.

But the transition to commercial maintenance methods is not simple, partly because military aviation is a very different animal. Reddy ticked off some major differences: “Commercial aviation changes parts before they fail, while the military has flown aircraft until they break. Commercial aviation tracks specific LRUs [line replaceable units] by serial number, but the military has not because, given the age of its fleets, it did not have a UID [unique identifier] program at the outset. Commercial aircraft fly standard and steady missions, while military missions are more diverse and conducted under rougher conditions. Huge fleets of commercial types can rely on long-term partnerships with part suppliers, while small and old military fleets, such as the 66 B-1s, often face a diminishing base of part suppliers. Finally, commercial aircraft can tap the aftermarket for needed parts, while the rigid mil-spec requirements prevent the military from doing so.”

Boeing is working on supporting the Air Force’s HVM effort under three engineering assignments: CDDS [CITS deployable diagnostic system], a web-based tool for tracking failure data in real time; reliability- centered decision-making; and kitting for repair work. Reddy summarized these under three headings: fault data, maintenance scheduling and point-of-use kitting integration.

CDDS will draw fault data from the B-1’s onboard CITS, or central integrated test system. And Boeing’s reliability-centric decision tool will connect directly to parts warehouses in a closed-loop system that ensures mechanics have the tools they need.

Boeing has just begun work on these HVM engineering assignments. Reddy hopes to have these completed so that, pending Air Force decisions, the first prototype aircraft can be inducted toward the end of 2010. Boeing’s structural tests show the B-1 can fly until 2060, so there should plenty of work ahead for HVM when it goes into full deployment.

Reddy argued that Boeing’s role as prime integrator for the B-1 makes it uniquely suited to support HVM on the strategic bomber. In addition to commercial experience, Boeing’s lean maintenance program on KC-135 in San Antonio has provided important lessons on efficient maintenance and kitting. ♦

Speeding Maintenance Up

A major effort like HVM requires collaboration with many private firms. For example, Derco Aerospace works as a subcontractor for M1 Support Services on the integration team of Warner Robins’ C-130J HVM. “In the first 18 months we designed the process and defined task kits,” Logistics Sales Manager J.J. Arnold explained. “In the current 18-month contract, we are physically testing the process.”

The integration team designs, populates and delivers task kits to mechanics. Instead of charging upfront for materials, Derco charges only for materials actually used and manages the supply chain.

Derco also provided Andon, an audio-visual system mechanics use when they have a problem—involving tools, materials or manpower—that could slow work down. The integrator sends a runner with necessary gear or staff, making sure mechanics do not need to leave the aircraft. Arnold says Andon has been very successful.

The main integration task remains building task kits and ensuring supply chain support. “The bill of work and bill of materials need to be clearly defined,” Arnold said. “It’s working well. The task kits are a plus right now.”

The basic principles of HVM apply throughout Air Force maintenance in a wide variety of ways. Whether a program is called HVM or not, the basic aim is always to get work done as fast, effectively and economically as possible. Private firms are contractually committed to conduct their own assignments efficiently, and they help the Air Force do its work that way as well.

BAE Systems provides full lifecycle support for both fixed and rotary wing military aircraft, chiefly for the Air Force. BAE maintains an Advanced Component Obsolescence Management (AVCOM) tool, helping the Air Force plan for and deal with obsolescence, a critical maintenance challenge. John Wall, VP of aviation programs, said BAE engineers can reverse-engineer electrical and mechanical parts to replace obsolete ones, and its metal back-shops in Albertville, Ala., can produce replacements.

BAE’s Crestview, Fla., facility does modifications on C130s, mostly gunships flown by the U.S. Air Force Special Operations Command (AFSOC). Dave Nagy, who leads this program, notes that reducing downtime for modification is just as critical as for PDM.

BAE has a unique program under which other contractors do their modifications while BAE mechanics are also working in Crestview hangars. This eliminates transport time to other facilities and means several modifications are done simultaneously, cutting total downtime by a month or more. Shifts are scheduled to maximize the tasks done each day without conflicts.

Modifications typically take longer in first trial, a bit less in kitting test, and then less time in production. BAE recently cut modification time from four weeks to 13 days from first trial to production.

With a total contract value of more than $1 billion over the next nine years, Chromalloy is providing a variety of highly specialized support services for engines. It repairs stators and vanes on Pratt & Whitney TF33s, which power the B-52H Stratofortress, the C-141 Starlifter and many KC-135 Stratotankers. It supports vanes and inner shrouds on Pratt’s F100, which powers F-15 Eagles and F-16 Fighting Falcons and supports or repairs components of CFM International’s F108s, including nozzle segments and high-pressure turbine blades. Chromalloy overhauls GE’s CF650 on the KC-10 Extender and repairs modules of GE’s TF39 for the C-5 Galaxy.

“All Air Force contracts mandate turn time and we compete for contracts based on that,” said Jim Diehl, Chromalloy military sales director. “We work to meet or exceed turn-time requirements, and performance has resulted in many contract renewals.”

The primary metric is on-time delivery. “Chromalloy military programs have met or exceeded this metric for many years,” Diehl said. Sometimes this required quick reaction. Under emergency contracts in 2009 Chromalloy provided F108 modules needed during work stoppages at Tinker ALC. “Chromalloy delivered on-time or ahead of schedule,” Diehl stressed.

Economy as well as speed is at stake. “A majority of engine expenditures are allocated to sole-source OEM providers,” Diehl noted. “Our services and parts provide an alternative and help ensure a competitive contracting environment.” ♦

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