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Military

System helps determine 'health' of Air Force aircraft

by Holly Jordan
Air Vehicles Directorate

7/11/2008 - WRIGHT-PATTERSON AIR FORCE BASE, Ohio (AFPN) -- Military aircraft must be safe, reliable, and ready at a moment's notice to complete their mission. Unexpected maintenance, and even scheduled maintenance checks, can keep an aircraft out of service when needed most.

That's where Integrated Systems Health Management, or ISHM, comes in.

ISHM is a system that collects data from various areas of an aircraft and transmits real-time information about the condition of the vehicle back to the maintenance depot.

Mark Dessiro Air Force Research Laboratory's ISHM lead, compares the typical aircraft to people with congenital insensitivity to pain. People suffering from this condition cannot feel pain and, therefore, cannot inform doctors of their symptoms.

"What we are doing with ISHM is trying to determine the condition of the entire vehicle," Mr. Derriso said. "We want the vehicle to tell us how it feels. Then we can decide whether it is safe to perform the next mission or send it to be repaired."

The potential safety benefits of ISHM came into focus during the Missouri Air National Guard mishap in November 2007. In the training exercise a forward fuselage of an F-15 broke apart from the rest of the vehicle, forcing the pilot to eject. The aircraft was lost. The pilot survived, but the entire fleet of Air Force F-15 A-D aircraft was subsequently grounded until officials completed emergency inspections.

The cause of the F-15 incident was deemed to be fatigue cracks in the upper cockpit region. According to Mr. Derriso, this is the type of structural damage AFRL engineers believe can be detected through ISHM.

While mission safety is the most critical element of ISHM, it also provides benefits in terms of cost and aircraft availability. Continuous real-time monitoring of the aircraft prevents the vehicle from having to undergo unnecessary pre-scheduled maintenance, which can be costly and cause the aircraft to be out of service for long periods of time.

Mr. Derriso said ISHM also helps maintenance crews continuously monitor the status of aircraft components, allowing them to have parts in stock beforehand, ready for installation when the aircraft is scheduled for maintenance.

Officials say ISHM can be a benefit to both current and future military aircraft. ISHM can also help by eliminating routine pre-flight inspections.

ISHM is also benefiting commercial aircraft as well. According to Mr. Derriso, commercial airframe manufacturers are already employing elements of ISHM to aircraft such as the Boeing 777 and the new 787 Dreamliner. Recent groundings of commercial aircraft such as American Airlines' MD-80 fleet and Southwest Airlines' Boeing 737s to inspect for possible wiring and structural problems emphasizes the need for ISHM on commercial applications.

AFRL researchers are currently examining ISHM systems at the subsystems level to try to examine and improve ways the components can work together to more effectively gather data. Researchers are currently monitoring data from piezoelectric sensors installed on an F-16 test vehicle at Luke Air Force Base, Ariz. Mr. Derriso says that by monitoring this data, researchers are not only able to determine the quality of the damage detection techniques, but also the durability of the sensors themselves.

According to Mr. Derriso, the next ISHM test will be on a Global Hawk wing. The wing will be equipped with a sensor array and subjected to two lifetimes worth of structural fatigue. Researchers will then assess how well the health monitoring system detects fatigue damage and how well the sensors themselves withstand the test.

After the structural testing is complete, AFRL researchers plan to move toward an integrated ISHM test. The test will use a recently-designed ISHM architecture -- combining components from aircraft structure, flight control, and propulsion -- that performs real-time diagnosis and prognosis at the platform level. The testing will serve as another step toward eventually maturing a system that can be incorporated onto military vehicles. Derriso says his hope is that the ISHM architecture used in this test will become the standard for the ISHM community.

Current and future ISHM developments from AFRL and other organizations will be the focus of the upcoming 2008 Integrated Systems Health Management Conference (www.usasymposium.com/ishm), to be held August 11-14 at the Northern Kentucky Convention Center in Covington, Ky.

ISHM is a combined effort of the AFRL Air Vehicles, Propulsion, Sensors, and Materials and Manufacturing Directorates, as well as numerous airframe designers and contractors.



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