Sensors aboard helicopters can help predict parts failures.

Seeking to cut maintenance costs and improve the readiness of its helicopter fleets, the U.S. Army is considering expanding the use of so-called "health monitoring" systems, which will allow maintainers to predict when parts will need replacement. Health-and-usage monitoring systems (HUMS) now are in development for the Army's new UH-60M Black Hawk and Block III AH-64D Apache helicopters. HUMS help track the wear and tear of aircraft components

Meanwhile, a new cargo platform maintenance environment (CPME) is being fielded for the CH-47 Chinook heavy lift helicopter. The technology could be applicable to the broader helicopter fleet, officials said.

The first CH-47 unit with the CPME will deploy to Afghanistan later this year and demonstrate "tele-maintenance" capability with links back to the United States. CPME will record maintenance actions, aircraft configurations and routine business metrics to help the Army manage its Chinook fleet more efficiently, officials said.

"Right now, we have no visibility on the root cause of [component] failures," says Ted Schmidt, chief of logistics at the Aviation and Missile Command cargo helicopter program office. "We don't know if a part was removed for a fault, time between overhauls or a false removal."

False or premature part removals unnecessarily decrease aircraft availability and increase support costs. While today's Army supply system simply processes requisitions, future fleet managers will use a database to tie maintenance actions to specific parts, aircraft and units. "We'll be able to track a failure all the way through the maintenance structure and see what will be the effect," says Schmidt. The CH-47 program manager, for example, has already cited CPME data to support doubling the Chinook inspection interval from 200 hours to 400 hours.

The 160th Special Operations Aviation Regiment already maintains its Chinooks, Black Hawks and Little Birds with a homegrown digital data system based on the paper forms used by the Standard Army Maintenance Information System.

CPME will not replace the current system, but it will provide the means to integrate comprehensive maintenance recording and schedule planning with aircraft HUMS.

The combination of a ground-based maintenance management system and helicopter-borne HUMS will monitor transmission, drive-train and control components in specific missions and theaters. Tied to cockpit displays, a predictive HUMS can warn aircrews of impending failures.

"If you prevent one accident, it pays itself off," notes Larry Plaster, manager of Apache modernization at the Boeing Company.

The cancelled RAH-66 Comanche was to carry a portable intelligent maintenance aid to help troubleshoot faults. The PMA notebook computer was meant to store interactive electronic technical manuals and download maintenance information to Army-wide support systems. Some of the same functions will be performed by the Chinook CPME and other helicopter maintenance management systems.

Chinook technical manuals and maintenance schedules, along with instructional graphics and embedded training videos, are stored on electronic cards loaded into the computers. As maintainers complete assigned tasks and check off corresponding blocks, the CPME records data known as "P2T3," which stands for people, parts, tools, time and training. P2T3 information from the field is collected at the Army Logistics Support Authority, in Huntsville, Ala., and the Boeing information center, near Philadelphia.

CPME has been tested by Chinook units at Fort Campbell, Ky., and Reno, Nev., for more than two years. Boeing received a contract in September to field the system at 33 sites for the entire CH-47 fleet, over a two-year period.

In parallel with the new maintenance technology, the Army also is fielding a digital parts identification system for the Chinook. Boeing recently patented the mobile parts marking suite after working on bar-coding technology with the Army Aviation Applied Technology Directorate at Fort Eustis, Va.

Parts in newly built CH-47Fs and MH-47Gs are marked at the factory, and Boeing expects the growing inventory of marked parts to provide a usable CPME database in about two years.

Fleet-wide P2T3 data will make it possible to compare maintainers in the United States with those in Iraq or other operating theaters. "We can start seeing what parts they really use in a task-based maintenance environment," says Robert Beggs, senior manager at Boeing Aerospace Support.

The technology also may eliminate unnecessary inspections that drive up maintenance costs and risk damage to healthy parts.

The computer system will collect aircraft data from whatever HUMS system the Army chooses for the new CH-47E The Army is defining the requirements for a Chinook HUMS that will lead to a competitive procurement. A proposed demonstration with the 160th Special Operations Aviation Regiment will evaluate a Smiths Industries' maintenance analysis, safety and training package on the Chinook. The same equipment may be used on the CH-47F at Fort Rucker, Ala.

Dutch and British Chinooks already have Smiths and Teledyne HUMS that monitor vibration and other operating parameters and log the actual operating hours accumulated by transmissions and other parts. Accurate time records can pay off. Pilots typically round off flying hours by 10 percent to 15 percent in paper logbooks, and a 2,000-hour part retired 200 hours early denies about a year of service.

Commercial helicopter operators already have more sophisticated HUMS to monitor vibration, temperature exceedance and other signs of component wear. The Goodrich integrated mechanical diagnostics-health and usage management system (IMD-HUMS) on the commercial Sikorsky S-92, for example, monitors around 250 parameters.

Digitized military aircraft, such as the Army CH-47F, UH-60M and Block III AH-64D, make it possible to annotate health data with flight regime data, including speeds and loads. Heavier loads and hard maneuvering shorten the lives of dynamic components, and HUMS data can help determine part lives based on how aggressively the aircraft is used.

The Bell OH-58D Kiowa Warrior received an exceedance monitoring system in the mid-1980s, but the light armed reconnaissance helicopter had no vibration monitoring/diagnostic capability. In the mid-1990s, the Army Aircraft and Missile Research and Development Engineering Center started a "vibration management" program to develop a diagnostic system with rotor track and balance functions.

Bell Helicopter received a contract in 1997 to develop a vibration management system for the Apache and the Black Hawk. The technology is installed on AH-64A-model Apaches in the South Carolina National Guard and UH-60A Black Hawks in Korea. It also is being installed on eight AH-64Ds at Fort Bragg, N.C.

The earlier version of the vibration management system logs engine start and stop times, flight times, and G-loads but provides no warning of component wear. The Block III AH-64D now in development has an advanced computer tied to vibration sensors, gearbox accelerometers, and drive shafts to detect and help diagnose abnormal vibrations below the main rotor.

Initially, the system on the Block III AH-64D will display alerts and diagnose drive-train vibration. With time, the growing database on part wear will help warn of impending failures. The data may ultimately determine component lives based on actual usage. "Rather than tear down gearboxes every 200 hours, we'd tear boxes down when the diagnostics say it's time," explains Plaster. "That could extend the time between overhauls."

The system in the Block III AH-64D also will feed data automatically to the Longbow integrated maintenance manual. The current system has an electronic card to download collected data. Boeing foresees an airborne download capability by the end of AH-64D Block III production. Similar downlinks enable airlines to have replacement parts waiting when their aircraft land.

Despite initial successes on Black Hawks, Sikorsky evaluated different health-monitoring systems for the new M-model and selected Goodrich to provide the UH-60M HUMS.

Congressional add-ons funded a demonstration of the Goodrich second-generation IMD/HUMS on 30 UH-60Ls of the 101st Air Assault Division at Fort Campbell, and one UH-60A at Fort Rucker. An interim report is due in June 2005.

The IMD-HUMS works with a separate Honeywell flight data recorder and voice data recorder. A maintenance management system running on a notebook computer downloads trend data on electronic cards. "With this information, you can see things you would normally not pick up," says Goodrich program manager Steve Peckham. In one case, the IMD-HUMS data revealed tail rotor vibration too subtle for a pilot to detect. Subsequent examination found a potentially dangerous flaw in a composite tail rotor boot.

The third-generation integrated vehicle health management system (IVHMS) will be on the third UH-60M prototype and all future production Black Hawks. The IVHMS records operational flight data. Instead of removing parts at fixed intervals set by the helicopter manufacturer, maintainers can quantify longer or shorter lives based on how hard parts are used.

Helicopter manufacturers and depot managers may use the information to stock parts based on actual use.

The IVHMS on the UH-60M also introduces more advanced ground data management capabilities to resolve ambiguous diagnostics messages. The notebook computer assigned to the aircraft contains an electronic logbook and maintenance system with part numbers and a history of maintenance actions that generates work orders for the specific aircraft. It remembers the configuration of the aircraft and what maintenance tasks have been done. Sikorsky is working with the Army on how much IVt-IMS data should be available to the UH60M crew in flight through cockpit multi-function displays. The Army expects results by 2006.

Like the Block III AH-64D and UH-60M, the CH-47F program is moving toward condition-based maintenance. The cargo Chinook and utility Black Hawk programs currently are exchanging data on health and usage monitoring systems.

Earlier this year, the Army tested a Goodrich HUMS system aboard 20 Black Hawk helicopters of the 101st Airborne Division when the unit was deployed in Iraq. The experience in the field proved that this technology is needed throughout the entire fleet, said Army Chief Warrant Officer, Sam Kunselman, from the 159th aviation brigade.

The Army's program executive office for aviation is funding a two-year demonstration of HUMS technology that was scheduled to start in September 2004. The plan is to collect data and prove to the Army decision makers that it's worth the investment, Kunselman told National Defense. The upfront cost to install this system on existing helicopters is $150,000 per airframe, he said. "The program manager believes the cost can be recouped through maintenance savings and safety."