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A Programmatic Approach to Aircraft Health Monitoring

Amy Bubon1, Frank Eason2 and Ken Todd3

1 Aerospace Electronic Systems, Honeywell International, 4601 N. Arden Drive, El Monte, CA 91731, USA

2 US Naval Air Systems Command (NAVAIR), H46 Fleet Support Team, Bldg 4033, MCAS Cherry Point, NC 28533, USA

3 Diagnostic Solutions, 916 Firetower Road, Jacksonville, NC 28540, USA

Abstract The true success of Health Monitoring Systems is realized once the system is able to not only diagnose conditions but also derive process improvements. A challenge facing Health Monitoring System integrators is the ability to make sense of the mass amount of data provided by these systems. A successfully integrated solution will encompass all levels of the organization including management, engineering, maintenance, and logistics. The application of knowledge management becomes key in developing a complete program to improve safety, reliability and maintainability. The United States Marine Corp H46 helicopter has achieved the highest readiness rating of any aircraft in the USMC inventory. This accomplishment is rather significant as the H46 helicopter is over 40 years old. Successful implementation of the Health Monitoring System program has contributed to this outstanding rating. The information to be provided herein shall display the programmatic approach used by the USMC H46 Fleet Support Team to implement health monitoring equipment and software to realize a return. Processes, procedures and the interaction required between all organizations shall be discussed. Specific case examples detailing the root cause analysis and financial savings shall be shown. Introduction During the mid 1990’s The United States Marine Corp H46 program was experiencing support equipment problems with the rotor track and balance (RT&B) equipment and engine drive shaft vibration equipment. The program purchased the Honeywell 8500C to replace both pieces of older equipment. The aircraft had also developed RT&B problems due to several blade modifications over the years. This problem created an excessive vibration on the ground which was directly linked to cracking of engine front frames along with premature structural and hinge point failures. The cause of the problem was poor chord weight setup on the blades because the whirl tower was not configured to replicate the rotor head. The tower treated all blades as neutral chord when in reality the rotor heads are configured with both lead and lag blade folding linkages which require a chord correction. Funding was granted to fix the ground balance problem in order to solve the engine front frame cracking issue. The front frame cracking at the time was the #1 safety issue for the

Eleventh Australian International Aerospace Congress Sunday 13 – Thursday 17 March 2005

Melbourne, Victoria, Australia

AIAC-11 Eleventh Australian International Aerospace Congress

Fourth DTSO International Conference on Health and Usage Monitoring

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H46. Once the crack began to propagate engine lube oil would burn off in flight causing in-flight engine shut downs. The program, designated Dynamic Component Change 81 (DCC-81), was executed and required a procedure, hardware and software change. The Hardware Change was a redesign of the chord weight fixtures to incorporate moveable weights of equal amounts. The procedure change was to eliminate the whirl tower and match track the aircraft rotor blades as a set. The software change required a solution to be calculated to correct the balance deficiencies in 4 different regimes including the ground. The program was successful in eliminating the engine front frame cracking problem, which increased the safety by reducing the risk. However, the real cost savings came as a result of eliminating the need to whirl tower the rotor blades. The program management realized a savings of approximately 5 million US dollars a year in 1996 by not towering the blades. Once the RT&B equipment was fielded it was soon realized that benefit could be achieved through furthering vibration analysis and the use of the equipment. The next logical step was to implement periodic vibration checks using the ground support equipment to monitor drive train and engine vibration levels. Soon after implementing the periodic checks immediate benefits were realized justifying expansion into an on-board Health Monitoring System. Now the challenge began. What is the best way to define and implement a Health Monitoring System to realize benefit quickly with minimal impact to the fleet? The remainder of this paper will step you through the process implemented by the USMC H46 Program Management Authority and its success. Phase I: Getting Started and Setting the Foundation The following four guidelines were emphasized at the beginning of program implementation and proved to be very valuable in the success of the program. STEP 1: Initial Testing and Instrumentation: As it is virtually impossible to establish vibration limits without either endorsement from the Original Equipment Manufacture (OEM) or historical data, the first step identified was to collect data and learn the aircraft. Frequency models for the drive train and engines were built and studied. Data collection sequences were derived and evaluated on test aircraft to optimize sensor locations. Before implementing any new field procedure the engineering staff performed a validation test. The key guideline to success was generating maintenance actions for every limit established and validating them before fleet wide implementation. STEP 2: Data Analysis Software: It was soon identified that to accomplish vibration analysis successfully software was key. The system must be able to store the data, quickly review the data at the squadron, and easily allow for its transfer back to the Engineering Fleet Support Team (FST). Merely collecting data without having software tools to drive real world interpretation of the data will contribute to an unsuccessful program. The software must be flexible and allow the FST to easily and quickly modify the data collection sequence and limits when changes are necessary. The VibraLogTM software solution implemented by the H46 program was able to analyze large amounts of data based on statistics to derive limits. STEP 3: System Training: Training must be emphasized. No matter how turnkey and transparent the system design, it will never succeed unless maintenance personnel understand the theory and operation of the system. For any program to succeed it is vital to provide the

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user with the necessary system training, both instructional (class room) and practical (hands on) type training. The system needs to be both “user friendly” to operate, as well as relevant in it’s functionality to the operator. Maintenance personnel need to know that the system will benefit them more and more as the program is allowed to grow. Share results with people and empower them to play an active role in the development. STEP 4: Active Involvement: Finally the entire organization must play an active role in the development and implementation of the program. Management, Logistics, Maintenance, Repair & Overhaul facilities, OEM’s, Vendors, Purchasing, Quality Assurance, Operators and Engineering must all be engaged. It is important that all organizations understand the role that each plays in the program success. Establish the correct infrastructure in your organization early and empower the people. Phase II: Periodic Vibration Monitoring Monitoring of the engine and drive train vibration levels was the birth of the program. At this time ground support equipment was being used to collect the data every 100 flight hours. As more personnel became trained the system gained support as a troubleshooting tool. Hit or miss maintenance practices began to diminish once health monitoring data was able to drive decisions that saved time. Good communication and data transfer between the squadron and the FST was critical to validate the system, provide answers and refine limits. One of the first findings uncovered by periodic vibration checks was the critical speed of the high speed shaft assembly. This problem went undetected for many years due to older support equipment which only checked vibration levels at operational speed. This G-meter narrowband vibration equipment was not capable of detecting shaft resonance. By implementing a 400 line FFT spectral collection to 48,000 CPM, the problem was easily identified with a vibration peak at critical speed of 283 Hz (17,000 CPM) while the shaft was operating at 325 Hz (19,500 RPM). Eventual catastrophic results could occur if the condition went undiagnosed. This example of high speed shaft resonance is shown below, Case Example #1. Continued implementation of periodic checks proved once again significant. The checks immediately discovered improperly manufactured and misbalanced high speed shaft adapters. Several months of data was collected and showed no significant vibration problem. After the acceptance of a new lot of adapters, vibration levels significantly increased triggering preset limits. The occurrence of the problem escalated quickly as more adapters were installed in aircraft elevating the need for engineering analysis. Case Example #2 details the findings. Main electrical generators were also a problem with numerous Hazard Material Reports from the fleet reporting catastrophic failures. These failures were very costly to the program office and required a complete overhaul. The use of periodic checks allowed for failing electrical generators to be identified before catastrophic failure. The vibration program realized an annual savings of USD 992,000.00 by significantly reducing the occurrence of failures but to achieve a 100% capture rate an on-board system must be installed. Case Example #3 details the findings. Due to the success of the periodic vibration checks, the vibration program was expanded authorizing high time component life extensions. The fleet is required to submit vibration

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data prior to any extension for the transmissions. FST engineering would evaluate the health of the component using the vibration data as the discriminator for extension approval or denial. Case Example #4 details the findings. Further discoveries of engine vibrations was revealed which showed a need for better engine test cell vibration diagnostic capabilities along with changes in process and procedures for component balance and ultimately drove to purchasing new state-of–the-art balancing machines and tooling. Case Example #5 details the findings. Case Example #1: High Speed Shaft Resonance Problem Statement: Torque sensors were found damaged on the aircraft, Figure 1.

Figure 1: Damaged Torque Sensors Background & Findings: Historically the health of the high speed shaft was checked by a G-meter tester that measured the 1P of the shaft. Now with the implementation of narrowband spectral analysis more characteristics of the shaft were able to be seen. In this case a large peak was detected at resonant frequency, which was not previously identified in the frequency model, Figure 2. Reports by the flight crew indicated a howling noise and significant vibration along with erratic torque readings. Further engineering study, modal testing and OEM input determined the shafts critical speed was 283 Hz.

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Figure 2: High Speed Shaft Resonance Root Cause: Engineering determined the cause of the resonance was spline wear between the shaft and the adapter assemblies. The shaft would enter into resonance during ground turns when the shaft and adapter were in an unloaded condition or if engines were intentionally throttled back to reduce rotor speed. The shaft design incorporated a resonance frequency that could become excited if spline wear became excessive. Although the problem could be intermittent, inspection of several aircraft indicated that spline wear was going undetected allowing for the shaft to operate in resonance. Resolution & Lessons Learned: In the short term, Depot level personnel are instructed to properly inspect for spline wear. The squadron personnel are to check for shaft resonance whenever erratic torque readings are experienced. Further, Pilots have been discouraged in the practice of throttling back engines to save fuel, which keeps the shafts from operating at critical speed and resonating. The longer term solution will be a new shaft design that will change the resonant frequency of the shaft. Case Example #2: High Speed Shaft Adapter Imbalance Problem Statement: Fleet experienced a sudden increase in unacceptable shaft vibration levels causing excessive replacement of high speed shafts and shaft adapters. Components supplied directly from stock were replaced multiple times. Because the shaft speed is identical to the engine power turbine and mixbox input speed misdiagnosis often occurred. Engines and transmissions were falsely removed after multiple adapter changes. Rather than purchase more components a decision was made to investigate and determine the root cause driving the continual rejection of parts.

Extremely High Vibe at Resonance frequency

G-meter would have missed this resonance as readings for the 1 Per/Rev were within limits

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Background & Findings: Ground vibration checks displayed the high speed shaft within limits at 4.3 g’s, Figure 3, but in flight results identified significantly increased above the limit to levels of 19.69 g’s in Hover and 26 g’s at 120 KIAS, Figure 4. Damage to engine and transmission shaft seals were also being experienced.

Figure 3: Ground Check Results Figure 4: 120 KIAS Check Results:

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Root Cause: Balancing procedures at the adapter vendor and depot repair facility were evaluated and found to be faulty. Good shaft adapters were being ground excessively making the adapters bad, yet they were presented as new and balanced. Figures 5 and 6 below display new adapters that were placed to stock as correctly balanced parts.

Figure 5 & 6: Improperly Balanced Adapters Resolution & Lessons Learned: The balance machines were updated and match set balancing was tested. The problem has improved as fleet knowledge of this issue has been addressed. Keep in mind that new parts can have problems and that “the way you have always done something” does not always make it right. Case Example #3: Main Electrical Generator failures: Problem Statement: Main Electrical Generators were failing at an alarming rate and numerous Hazard Material reports were generated from fleet activities. Once the generator failure occurred it would result in excessive smoke, sparks and flames causing emergency landings as the generator could not be shut down without shutting down the aircraft. Background & Findings: The electrical generators went for years without many failures as they were on a scheduled removal for overhaul. Since the failure rate was low the component was deemed reliable and a decision to discontinue the overhaul schedule and fly until reason to remove was implemented. After several years of not overhauling the generators they began to fail. The initial discussion was that the generators had reached their service life and purchasing of new generators was to be investigated. Root Cause: Not overhauling the generators on a scheduled basis meant the generators stayed in the field longer. This caused the main rotor support bearings to fail due to lack of lubrication and age. Once the bearings failed, the rotor would impact the stator at operating speed of 8040 RPM. This caused the catastrophic failures resulting in the smoke and fire, Figure 7.

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Figure 7: Failed Electrical Generator Resolution & Lessons Learned: FST engineering established a not to exceed alarm level that required removal and replacement of the electrical generator, Figure 8. Further the Generator overhaul facility was outfitted with a vibration system and program for checking vibration levels on all incoming and outgoing generators. The search for a new generator has been called off and a solid rework procedure has now been established. Fly until limit exceeded which is the first on-condition maintenance success for the H46 program. Figure 8: Electrical Generator Limit

Bearing Housing Damage

Rotor Contacted

Stator

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Case Example #4: Service Life Extensions for aft transmissions Problem Statement: The Aft Transmission mix box has a high time of 900 hours do to clutch support bearing failures. The operators routinely were granted life extensions from engineering with no evidence of the health of the transmission. This resulted in untimely maintenance actions with chip indication as the primary source to remove. Background & Findings: As the fleet sent in the data for review by FST engineering requesting life extensions the vibration signatures revealed the condition of the transmission making the decision to extend or remove easy and effective. The condition of worn support bearings shows in the spectral graph as sidebands around the collector/spur gear mesh at spur gear speed, Figure 9. Further the 1 per rev vibration of the spur gear increases significantly along with multiple harmonics, Figure 10. This is a clear indication that the bearings have degraded to the point of allowing looseness in the spur gear assembly causing modulation of the gear.

Figure 9: Collector/Spur Gearmesh

Collector/spur gear mesh

Sideband spacing at spur Gear 1 per speed.

Multiple sidebands

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Figure 10: Spur Gear Speed and Harmonics Root Cause: The transmission having a resonance at approximately 3175 Hz causes the bearings to fail as the resonance occurs at the same speed as the collector/spur gearmesh frequency, Figure 11. The clutch and support bearings are part of the spur gear assembly and the clutch support bearings are the first to fail.

Figure 11: Collector/Spur Gear Resonance Resolution & Lessons Learned: The fleet is required to submit vibration data for life extensions. Further engineering investigations and studies have been and are underway to determine the source of resonance and eliminate it. If the resonance can be eliminated, it has been determined that the life of the transmission can be at least doubled from its current 900 hour force removal time. If successful, the cost savings would be significant. This example is the first step into on-board advanced gearbox analysis.

1X of Spur gear

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Multiple Harmonics of Spur Gear

Collector/spur gear in resonance Over 500g’s

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Case Example #5: Excessive engine vibrations: Problem Statement: The squadron received a newly overhauled engine from the Intermediate maintenance activity. The engine was installed and on initial testing a loud howl from the engine was heard. Background & Findings: The engine had just completed overhaul with a new compressor rotor installed. It was ran on a mobile test stand and determined ready for issue as all power and vibration readings were acceptable. The test cell vibration system in use was a Mils broadband system utilizing velocity pickups and a filter range between 70 and 2000 Hz. The aircraft vibration was determined to be a 1 per rev vibration of the Compressor rotor, Figure 12. Further testing at the depot level confirmed the engine was defective and revealed that the IMA test stand equipment had failed to identify this over limit condition, Figure 13.

Figure 12, 1P of Compressor

Compressor Rotor Speed at 81%

Fleet average for this Frequency is below .2

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Figure 13: Depot Test Cell Verification Root Cause: The cause of the vibration was a poorly balanced compressor rotor that once built into the engine and ran caused damage to the 8th, 9th, and 10th stages of the rotor. The rotor had impacted the stator casing. Investigation of the balancing techniques and equipment revealed that the current procedures and equipment were not capable of providing acceptable and repeatable balance of the compressor rotors. Resolution & Lessons Learned: To resolve the problems several issues were addressed and corrected. A new State-of-the-art vibration system was developed and fielded on all T58 test cells. New Balance Machines and tooling were purchased and new procedures, processes and controls were incorporated. Engine limits have also been incorporated for installed engines. Phase III: Hardwiring the Aircraft At this time it was known that a permanent on-board solution could increase the effectiveness of health monitoring. However, it was also realized that it would take significant time to define the complete HMS requirements, select a vendor, design, build, and test the system. An intermediate step was needed to keep the health monitoring program moving forward. As wiring the aircraft was part of the system it was determined beneficial to the PMA to make this the next step. This choice was justified, Case Example #6, when the program experienced an engine drive shaft catastrophic failure. Case Example #6: Engine Drive Shaft Catastrophic Failure Problem Statement: The squadron had installed the carry on vibration equipment to perform post maintenance vibration checks after an engine installation. The initial indication was the

Depot Test cell run using spectrum analysis instead of broadband. Limit was 1.5 Mils.

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#1 engine drive shaft displayed an unacceptable 2 per rev vibration indicating misalignment, Figure 14. Maintenance was performed on the #1 engine per the manual and released for flight. Several flight hours later while the aircraft was in a hover a loud howl was heard and then a bang as the #2 engine drive shaft was severed.

Figure 14: Misaligned Shaft Detected Background & Findings: An investigation was launched and interviews with the participants were conducted. The outcome of the investigation revealed that the carry on equipment was installed backwards, i.e., the #1 accelerometer was wired to the #2 channel and #2 was wired to #1 channel during the initial test. After the initial vibration check, the equipment was removed and used on other aircraft. After the maintenance was performed, which was a misalignment check, only the #1 engine shaft was rechecked to see if the problem was solved. Since the #2 shaft was the problem it went undetected allowing it to fly until failure, Figure 15.

Figure 15: Catastrophic Failure of Shaft

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Root Cause: The cause was directly linked to human error on improper installation of equipment along with a severe misalignment of the #2 engine drive shaft that quickly degraded with time. Resolution & Lessons Learned: To resolve the problem a study and cost analysis was performed and it was determined that hardwiring the aircraft would prevent the human error and a full time monitoring system would have alerted the crew prior to the catastrophic failure. Phase IV: Expanding to Test Cells Engine vibration problems were found on wing yet engines had passed the test cell antiquated MILS broadband vibration system. Investigations into the test cell broadband system found many problems including: use of faulty sensors, incorrect filter cards, faulty sensor leads, and general lack of user troubleshooting resources. In other words the operator had no real way to verify the broadband system was functioning accurately. All this lead to many false rejects and some engines being sold which should have failed the test! It was determined that test cells should be incorporated into the program approach. The FST found it critical to have better test cell data and to correlate the data with aircraft data. This emphasis on test cell vibration data proved very successful. Implementing narrowband vibration checks onto the test cell increased the average engine mean time since removal, decreased the engine turn around time and increased the average net spares available, Figures 16, 17, & 18.

Figure 16: Average Engine Mean Time Since Repair

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Figure 17: Average Engine Turn Around Time

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Implemented VXP System

Began implementation

Operation Iraqi Freedom

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The use of common equipment and the ability to transfer data between the test cell and the aircraft significantly decreased the time to troubleshoot and repair engines. Case Example #7 below shows the effort expended by the test cell operators and how quickly it was diagnosed once the vibration equipment was installed on the test cell. Case Example #7: Engine Bearing #3 Failure Problem Statement: An engine on the test cell had 3 Power Turbine (PT) replacements as the test cell broadband equipment was indicating high vibration on the PT. Continual PT replacements were not successful in completing the engine acceptance test. Background & Findings: The spectral analysis equipment was installed on the test cell indicating high vibration levels at specific frequency ranges which could not be determined by the test cell broadband equipment. The vibrations seen in the spectral plot also indicated that the source was coming from the Gas Generator (GG) section of the engine and not the PT section. Speed settings were varied and multiple readings were collected and overlaid on the plot. The vibration signature changed non-proportionally with speed indicating a spinning bearing race, Figure 19.

Figure 19: Spinning Bearing Race Upon disassembly it was found that the engine had been making large curls of metal that went undetected as the fragments were too large to reach the mag plugs. The T58 had suffered catastrophic failure in the past due to #3 bearing failures, Figure 20.

Vibration pattern changed. But not in synch with The engine speed.

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Figure 20: Engine Bearing #3 Failure Root Cause: A worn component was the root cause of this failure. Inadequate test cell equipment did not indicate a problem with the Gas Generator section of the engine Resolution & Lessons Learned: Incorporate Narrowband Vibration Analysis into the test cells. Phase V: On-Board Systems Increase Safety As several incidents occurred between periodic vibration checks that were nearly fatal disasters it became more and more important to proceed with the development of an on-board solution capable of monitoring at a faster rate, Case Example #8. Case Example #8: Head Bearing Failure: Problem Statement: An aircraft experienced an increase in the rotor 1P vibration amplitude after successfully passing the 150 phased maintenance vibration test. Flight crews reported the perceivable increase in the rotor vibrations. Vibration SE was installed and a spectrum collected. Background & Findings: The spectral analysis indicated that the rotor 1P levels had indeed risen above the established alarm level, Figure 21. The senior squadron official flew the aircraft and reported no problem. Quality personnel were told to ignore the vibration level and continue to fly the aircraft. 7 flight hours later the aircraft vibration levels worsened to the point that the Air Boss on the ship ordered the aircraft to shut down. The Crew discovered a failed head seal and bearing, Figure 22.

Concave contour of journal surface (OD was .052 in undersized as a result of spinning inner race)

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Figure 21: Rotor 1P vibration trend plot

Figure 22: Failed Rotor Head Seal/Bearing. Root Cause: Investigation found that a report of a previous oil leakage problem was ignored as having “fixed itself”, implying that the head was flown for a period of time without lubrication. Lack of lubrication led to the bearing failure. Material analysis indicated that the rotor head hub lug was very close to total failure which would have resulted in complete loss of aircraft and likely the crew.

Previous Phase

Alarm 50 hours post

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Conclusion: Vibration analysis did detect this before it failed however the quality department was silenced by a skeptical senior officer. This could easily have been a mishap but thanks to an alert Air Boss it was prevented. The AIMS would have warned the crew continuously for at least 7 flight hours prior to when the photo in Figure 22 was taken. Phase VI: Aircraft Integrated Maintenance System To develop an on-board acquisition system it became important to evaluate existing features of Health Usage Monitoring Systems (HUMS) and determine what additional features beyond vibration would be valuable to the H46 program. Features selected must show the ability to improve processes driving maintenance savings and safety. As requirements generation proceeded a primary goal identified was to eliminate ground support equipment (SE). The care and feeding of SE had become expensive and time consuming and funding for the upkeep of SE was not as robust as that of aircraft avionics systems. The chosen system design should have the capability to derive solutions on the aircraft to achieve go/no-go decisions quickly without download to a ground station. Emphasis was placed on software as well as the ability to collect and store data. If the data collected by the system is unable to be diagnosed by the squadron or the feature is too sophisticated for an entry level technician, the feature will be useless. A good system will provide answers not just a lot of data for an engineer to interpret. The following features were selected for the H46 Aircraft Integrated Maintenance System (AIMS)

• Rotor, Track and Balance • Periodic Vibration Checks • Continual Vibration Monitoring • Engine Performance Checks with automatic nomograph and margin

calculations on the aircraft • Continual Engine Parameter Monitoring • 1553 Databus interface • Interface to the Cockpit Display Navigational Unit (CDNU) via the 1553

databus. Equipment that is eliminated by the AIMS include

• Honeywell Rotor, Track and Balance equipment – Model 8500C+ • Howell Instruments Engine Check system – NP600 • Vibration Signature Carry-on Accessory Kit

After a competitive solicitation process, the Honeywell VXP system was chosen as the best value to the Government. Currently six prototype systems are delivered and production deliveries start in 2005. Initial field testing and operation by the squadron are very positive.

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Through out the development of this system the FST, Honeywell, and the operators have been actively engaged in the design. Integrated Product Teams were formed to define and review the system requirements so as to meet expectations. Simulation systems were developed so that the aircraft environment could be brought into the office. The use of the simulator facilitates the development of technical data and procedures by the FST. Further, the simulator allows data collection sequences to be tested as well as alarm levels and alarm severity annunciations validated. An additional key use of the simulator is to facilitate classroom training. Key Features of the AIMS are shown below:

AIMS RT&B Function: The AIMS system allows for the collection of RT&B data at any time the crew desires. The system also will calculate a RT&B solution and present it to the crew in three ways,

1. In the cockpit via the existing CDNU displays, Figure 23. 2. In the cabin via the display unit (DU) provided as part of the AIMS system, Figure

24. 3. In the squadron maintenance shops on any computer running the AIMS display

program (DP), Figure 25.

Figure 23: AIMS RT&B CDNU Solution Screen.

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Figure 24: Display Program/DU RT&B Solution Screen AIMS Vibration Analysis Function: AIMS allows the periodic collection of vibration spectrums from any/all of the 25 vibration sensors installed. The collection parameters and component specific limitations are programmed by the FST using the software toolset provided with AIMS. The AIMS system also provides continuous vibration monitoring during the flight. All data is stored in text based files which are then viewable either by the squadron personnel or the FST. AIMS provides an alarm report anytime one of the established periodic or monitor alarm levels are exceeded. Figure 24 shows an example of the vibration alarm page seen on the CDNU by the crew in the cockpit. The alarm report text file is also viewable by the crew in the cabin using the DU or by maintenance personnel using the DP. The AIMS vibration monitoring feature is invaluable as it will prevent failures by detecting the short term increases of vibration levels between periodic vibration inspections.

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Figure 25: CDNU Vibration Alarm Page AIMS Engine Check features: The AIMS system provides all engine setup functions on-board thus greatly improving the speed and accuracy of engine setups. AIMS also provides real time display of engine performance parameters from both engines simultaneously in the cockpit via the CDNU or the DU in the cabin, Figure 26. Figure 27 shows the various engine setup functions performed by the AIMS system. The AIMS system will also perform the engine 4 point performance plot function, Figure 28.

Figure 26: AIMS Engine Live Parameter Display

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Figure 27: AIMS Engine Functions.

Figure 28: AIMS Engine 4 point performance plot. AIMS Engine Parameter Monitoring: The AIMS system also monitors engine and drive train parameters during every flight. This information will be valuable when evaluating over torques, over temps, duration of pressure drops, over speeds, and any other violations encountered during a flight. Alarms can be incorporated and modified via the ground software by the FST when necessary.

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AIMS Data: All vibration and engine performance data gathered by AIMS is stored in text file format. These files are stored internal to the AIMS box and can be downloaded onto a PCMCIA flashcard for transport to ground stations. The data is invaluable and should revolutionize the way the H46 community handles maintenance. Prior to AIMS, crews would have to install support equipment to troubleshoot problems reported during a flight or when a problem was found on post/pre-flight inspections. This meant that the aircraft would have to be flown again on a functional check flight to gather the data needed to help resolve the problem. AIMS saves that extra step and instead alerts the crews before a major problem arises and tells them during the flight. AIMS allows instant analysis of problems as they are detected. In the long run the AIMS data will also be valuable in planning aircraft maintenance to prepare for remote site deployments and other exercises away from home base. AIMS will allow squadrons to predict when an aircraft might need a major maintenance action before they deploy so that better planning and preparation can be performed. Conclusion Many benefits are realized by users of Health Monitoring Systems. The implementation of HMS provides not only improvement of maintenance practices and procedures but also enhancement in safety of flight (preventing catastrophic events for potential aircraft mechanical failures). Case histories have demonstrated the return on investment for the system. In short, start small and grow your Health Monitoring Program. If you wait for a system that does it all you will always be waiting. Choose problem areas and work towards solutions that will realize an immediate payback. Do not just collect data and remove components. Investigate the failure and determine the root cause. Follow the leads presented by the data collected and investigate any back shop procedures which may be aggravating the problems encountered. Make sure you fix the right problem with your solution. Health monitoring is an evolution. It depends not only on the technologies that collect and process the aircraft information but also on the knowledge management over time to increase effectiveness of diagnostics and prognostics process. It should be a close-loop process (sense, decide, and respond). With the H46 beginning a new chapter in the health monitoring area with AIMS, new challenges are now being presented. It will be important to develop smart solutions and incorporate them into the aircraft acquisition unit so the operator has immediate feedback on the aircraft. Additional features and technologies will be implemented into the AIMS once more success is realized. Growth technologies considered for the AIMS program include:

1. Advanced Gearbox Diagnostics applying epicyclic gear diagnostics technology licensed from Australia DSTO for both planetary and sun gear

2. Monitoring of flight control positions 3. Usage computation including automation of engine cycle count 4. Automation of flight regimes trigger and recording applying Honeywell VADARTM

patented technology 5. Automation of data management, diagnostics and prognostic processes

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References

1. Tuller, R., “T58 Lessons Learned”, Integrated Logistics Supply Maintenance Training Conference, 2002.

2. Wogoman C., “VXP Narrowband versus CEC Mils Broadband”, General Electric Vibration Summit, 2004.