Military, Products, Public Service

Making Maintenance Manageable

By Staff Writer | April 1, 2005

With the demands of combat and stiff competition for budget dollars, U.S. military leaders are insisting on less time-intensive and costly means of keeping rotorcraft flying.

U.S. military leaders love their rotorcraft.

During combat operations in Southwest Asia over the last three years and in activities elsewhere, helicopters have been able to move troops and supplies faster and more precisely than ground vehicles or fixed-wing aircraft, in many cases to places that those other transport options could not reach.


One flag officer after another has said that many of the combat successes achieved since U.S. forces launched Operation Anaconda in the mountains of Afghanistan in March 2002 would not have been possible without the support that U.S. Army, Navy, Marine Corps and Air Force helicopters provided. Yet in the next breath, these same general officers warn that these precious aircraft are simply too expensive to operate and that ways must be found soon to get those operating costs under control.

In their defense, the U.S. military rotorcraft are being run ragged. Flight rates are 2-3 times or greater the levels anticipated by operational and budget planners before 2001. That naturally increases consumption of spares and failure rates. (To their credit, the services' maintainers have been performing magic in achieving the availability rates that they have for some helicopters.)

Yes, most of these helicopters are combat aircraft and their use at current rates in combat must be expected. But the federal budgeting process is an extremely pragmatic exercise, focused more on the question of how you get by with the funding you've got than on the question of how much more you can get.

Before September 11, 2001, service officials had to come up with budgets that they could justify in a world that presented no imminent threat that would require a large portion of the U.S. military to fend off. Those budgets drove projections of how much flying the various rotorcraft fleets would do and how long their service lives could be extended. Pessimists (some might call them pragmatists now) could see then that aircraft lines were being starved for the sustainment needed to keep them healthy and available for a major crisis. But Chicken Littles don't get much of an audience, or a budget, on Capitol Hill.

As the mechanic in the old television commercial about preventative car maintenance said, "You can pay me now. Or you can pay me later."

Later has arrived.

While many problems in keeping military rotorcraft flying efficiently can be traced to stingy budget decisions years ago, most of them can also be pinned on what is now seen as a fundamental flaw in the way those aircraft are operated--or more specifically maintained.

The maintenance programs for most military aircraft are rooted in hard-time inspection intervals--checks that must be done after every 100 or 50 or even 10 hr. of flight. The intervals are dictated by probability when the aircraft is designed. Engineers are asked two questions: When is that component likely to fail? What is the consequence of its failure? Depending on the severity of the consequence of a particular failure, inspection intervals are set that range from conservative to extremely conservative. If a part is likely to fail at about 300 hr. of flight time, engineers come up with a plan that assumes a telltale sign of failure will be missed during one inspection, then set an interval that ensures (to the best that it can) that the part will be checked several times before it is likely to fail. Hence, a part whose mean time between failures (MTBF) is figured at 300 hr. might be inspected every 100 hr. or more frequently.

The problem with such schemes, which have served aviation well for decades, is that they rarely take into account the service history of an aircraft. While a whole slew of 300-hr.-MTBF parts may, in fact, run for 600 hr., that performance isn't always fed back in the calculations. Generally, inspection requirements get more stringent with time, not less. (In the commercial world, where folks make money off their aircraft, things are a bit different. Operators press manufacturers to test and improve their products to justify reduced inspection intervals, on the premise that an aircraft down for a check isn't earning any dough.)

A major shortcoming in this regard is data. Often, there is no data to say just what a component's service history is and whether it might justify less frequent inspections. The military maintenance and logistic systems aren't set up to collect and analyze such information efficiently, so data can't be fed back into recalculations of maintenance requirements.

In short, military maintenance is reactive and, therefore, overly conservative, in the minds of many. Commercial and civil aircraft operators since the early 1970s have been maintaining aircraft "on condition," that is fixing only what is broken and leaving hard-time inspections in place only for the most critical components. Some estimates say that 80 percent or more of military maintenance (including inspections) is done on components that are perfectly fine. Gen. Richard A. Cody, the U.S. Army's vice chief of staff and an Army aviator, dubs the process "exploratory maintenance."

A civil maintenance chief would get his walking papers fast practicing his trade like that and incurring the costs that come with such practices. So far, though, the philosophy of on-condition maintenance has penetrated very little into the military maintenance mindset. But that may be changing.

Both the U.S. Army and Marine Corps have launched initiatives to test their ability to collect the data needed to more efficiently manage maintenance programs, and by extension maintenance costs. In fact, on March 31, the American Helicopter Society's Redstone Arsenal chapter was to host a conference on on-condition maintenance and the Army's efforts to transition to it.

"Two of the biggest cost drivers in maintenance of military aircraft are fault identification and fault isolation," said Col. Cory Mahanna. Labor hours and dollars are spent finding and fixing maintenance problems. "Unfortunately, we also waste our efforts working on what turn out to be perfectly good parts or subassemblies."

The U.S. Army's program manager for utility helicopters, Mahanna is smack in the middle of this maintenance dilemma. Utility aircraft must fly, but they must do so more efficiently. How to get there?

Mahanna's Utility Helicopters Project Management Office has launched an initiative to examine more effective "life-cycle management" approaches to maintenance and the related effects they can have on the bigger problem of logistics support.

Working with the 159th Aviation Brigade of the 101st Air Assault Div., Mahanna's team looked at how to better collect and track data on both maintenance and the condition of aircraft being maintained. A primary tool was Goodrich's Integrated Mechanical Diagnostics System, an advanced health and usage monitoring system, or HUMS. That system looked at numerous elements of an aircraft's performance, including rotor tuning, vibration diagnostics, mechanical diagnostics, absorber tuning, engine performance, events and faults. The data collected on board was used to generate reports on both diagnostics and prognostics of the aircraft's systems.

Mahanna's team deployed 30 HUMS sets on the 159th's aircraft. The brigade then tested the systems under wartime conditions in Iraq. As Mahanna noted, "the outcomes are quite encouraging."

The 159th was able to cut roughly 1,920 maintenance labor hours a year on their UH-60 fleet on vibration checks alone.

The results were so impressive that the managers of the Army's CH-47 Chinook fleet are working to have HUMS integrated on their aircraft as well.

The Goodrich system permits a maintainer or crew chief to play back the flight and system parameters from a mission and analyze the data with a number of different graphical tools.

"We no longer have to guess what loads a rotor system saw or how long an engine operated at a particular temperature," Mahanna said

Perhaps most importantly, that data can be relayed to aircraft managers in the Army and Sikorsky for analysis of potential fleet-wide matters (including the possibility that data would support more efficient revisions of the maintenance program).

As the database of information collected by HUMS builds, the possibilities become awe-inspiring for those lashed for years to rigid, hard-time maintenance programs.

"We will be able to accurately forecast the parts we will need based on the actual status of each aircraft component," Mahanna said. In addition to shaving the operating costs of the aircraft, that would permit unit's to deploy with a smaller stockpile of spares with the confidence that the parts left behind aren't likely to be needed in the field.

Mahanna foresees numerous other benefits. Managers of parts in the Army's "life-cycle management" commands would know the actual status of all the items within their area of responsibility. Time between overhaul dates could be replaced with measurements of how much useful life remained in a part.

"Our best and brightest logisticians and acquisition professionals will have the true status of the fleet depicted in a dynamic way," he said. "We will couple this data with a knowledge-based data-sharing system that will give all our leaders the `real picture.'"

Last but not least, "we will move from scheduled maintenance, through condition-based maintenance to planned maintenance," he said.

Those advancements would both improve the readiness of aviation units and reduce the logistics train needed to support that readiness.

The Army's experience with HUMS helped that service's leaders to embrace the technology. The Goodrich HUMS is now incorporated as a pre-planned produced improvement on the UH-60M that Sikorsky is developing as the next-generation Black Hawk. That company is building 1,200 new UH-60Ms for the Army under a revision of the original plan, which called for conversion of older UH-60As and Ls. With HUMS installed throughout its fleet, Army aviation maintenance truly could be transformed in the coming years.

The MH-60M program for the US Special Operations Command is expected to closely follow the UH-60M upgrades. In addition to offering a high degree of commonality among the aircraft, that development could help improve the maintenance and availability of Secom's critical aircraft.

The Marine Corps is taking similar steps.

The CH-53E has been described as the military's most maintenance-hungry aircraft, and that reputation has only been aggravated by the operational tempo the aircraft has been running at since the opening of combat activities in Afghanistan three years ago. More than 40 maintenance labor hours are required to keep the -53E in the air, and its direct operating costs now often exceed $20,000 an hour.

The Super Stallions are showing their age and the effects of years of budgetary neglect stemming from the Marine Corps's focus on other, higher-priority aviation initiatives. That service has plans for a replacement in the form of the CH-53X and is marching steadily toward moving that aircraft from the drawing boards into development. But plans don't call for the CH-53X to be operational before 2015, so the Marines must find ways to keep the Super Stallions flying. More to the point, they must find ways to do that that also fit in with the realities of a defense budget that is focused on rebuilding Army aviation and, nonetheless, is likely to face intense scrutiny from budget cutters in Congress.

The Marines took a step toward helping themselves in February, when the Integrated Mechanical Diagnostic System for the H-53 fleet (which includes the CH-53s and the MH-53 Sea Dragons) passed its operational evaluation at MCAS Cherry Point, N.C. That clears the way for that system to enter full-rate production and be introduced fleet-wide. (The system has been in low-rate initial production and undergoing installation on HMT-302 aircraft at MCAS New River, N.C.) The expectation is that the system will both improve flight safety for the CH-53E and simplify maintenance of it.

"IMDS will take Big Iron maintainers somewhere they've never been before," said Col. Paul Croisetiere, the Navy's program manager for H-53 heavy lift helicopters here. "Home for dinner."

The system is also under consideration for installation in MH-60 and H-1 helicopters.

The Goodrich system is the first fully integrated multi-functional health and usage monitoring system to be fielded on Navy and Marine helicopters, according to Navy officials. Like the application on the Army's UH-60's, IMDS applies full-time diagnostic monitoring to the entire H-53 mechanical drive train--from engines to rotor system.

Once installed on the aircraft and integrated with the onboard systems and the CH-53E's mission computer, the system automatically performs a variety of functions currently done with separate test equipment, manual data collection and labor-intensive (and time consuming) maintenance troubleshooting.

"The biggest money-maker for the H-53 is going to be the IMDS rotor track and balance capability," said Maj. Hank Vanderborght, H-53 project pilot at the Rotary Wing Test Sqdn. at NAS Patuxent River, Md. "The H-53's seven-blade main rotor system takes a lot of effort for track and balance, both in terms of maintenance adjustments and functional check flight to verify the adjustments. IMDS collects that information on each flight and offers adjustments to minimize rotor vibration."

Vanderborght said the Goodrich system has let Marine maintainers balance the rotor head many times with a single set of adjustments. "That's significantly less work for our maintainers and a much smoother ride for everyone onboard."

With its complex rotor head, three engines, a massive transmission and gearboxes driving a tail rotor bigger than some other helicopters' main rotor, the Super Stallion also requires a lot of checking, calibrating and fixing of its powerful, and constantly vibrating, drive train.

"There are more than 40 vibration sensors on components that we want to monitor throughout the aircraft," said Eric Schwartz, H-53 systems engineer. "The system is capturing data all the time, and the software has been trained to recognize significant changes that suggest that a component could be failing. Depending on its criticality, we can take some immediate action, or we can flag that component for inspection and maintenance at a more opportune time."

In addition to helping maintainers diagnose mechanical issues, IMDS also automates some of the previous manual inspections and record keeping.

"Flight time and engine operating time are two examples of operational usage data that IMDS automatically records," explained Mark Bailer, the deputy program manager for in-service H-53s and IMDS integrated product team leader. "IMDS records usage data more consistently and accurately and relieves the crew of these bookkeeping chores. It will also step through the engine power assurance checks and eliminates the need to go into charts and tables confirm that an engine is healthy."

Data collected in-flight by IMDS is recorded on a standard PCMCIA memory card, which the crew downloads into a server after a flight to highlight anything needing maintenance attention.

"Before IMDS, we did it the hard way," said Croisetiere. "We did phase maintenance to check components manually on a regular schedule, which is very time-consuming, or we replaced components when they failed, which is expensive, inefficient and also time-consuming. With IMDS, the long-range goal is to fix things when we actually need to - the components will tell us when they need attention.

"That's a huge shift," Croisetiere added.

The Navy's top aviation test official called the Goodrich IMDS a "welcome enhancement" for improving vibration reduction-related maintenance functions.

"IMDS is on the right track for the long-range benefits of decreased scheduled maintenance and on-condition maintenance repair/inspection of components," said Rear Adm. David Architzel, commander of the Operational Test and Evaluation Force. "IMDS is operationally effective and suitable, and recommended for fleet introduction in the CH-53E."

In addition to the work with the Army and Marines, Goodrich has been selected to install its IMD-HUMS on the Navy MH-60R and MH-60S helicopters--the newest variants of the Sikorsky Seahawk helicopter. Goodrich has been working with the Navy since 1997 on applications of HUMS to its rotorcraft operations.

In addition, Goodrich has system health monitoring products on the V-22, and the AH-1Z and UH-1Y being developed under the Marine's H-1 upgrade program.

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