Integrated Mechanical Diagnostic System (IMDS)
Contribution to Helicopter Safety Improvement
AHS International Helicopter Safety Symposium
Montreal, Quebec
28 September 2005
Colonel Paul Croisetiere
Program Manager, H-53 Heavy Lift Helicopters
U.S. Naval Air Systems Command
Outline
• Navy/USMC Legacy Helicopter Fleet
• IMDS Description
– Functional Capabilities
– Safety-Enhancing Capabilities
• IMDS Growth and Future Applications
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Navy/Marine Corps
Legacy Helicopters
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Navy HUMS Program Mandate
• Result of a 1993 VH-60N mishap during a maintenance
flight
– H-53 designated lead-the-fleet platform for common helicopter
IMDS
• CNO mandate to incorporate avionics safety systems
– Ground Proximity Warning System (GPWS)
– Global Positioning System (GPS) navigation
– Crash-Survivable Flight Incident Recorders (CSFIR)
– Integrated Mechanical Diagnostic Systems (IMDS)
• Production program for H-53 and SH-60 began in 1997,
with H-1 added in 1999.
– Built by Goodrich Corporation, Fuel & Utility Systems Div.
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IMDS Description
• Full-time onboard usage and diagnostic monitoring
– Engines
Main Gearbox
and Swash Plate
Oil Cooler
– Drive train
TGB
#3 Engine
IGB
– Rotor system
Tail Drive Shaft
• Also tracks:
– Operational limit exceedances
#2 Engine
KEY
Blade Tracker
– Operational and structural usage parameters
#1 Engine
RTB Accelerometer
Tachometer
Drive Train Accelerometer
Optical Tracker
1/Rev index
• Flight data is downloaded post-flight for further diagnosis
and reporting to NALCOMIS
• System also on UH-1Y, AH-1Z, MH-60R/S, Army UH-60L/M
and Sikorsky S-92
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IMDS Enhances Flight Safety
• IMDS provides valuable safety enhancement
– Diagnostic drive train monitoring
– In-flight alerting
– Flight data recorder options
– Supports systemic improvements, such as Military Flight
Operations Quality Assurance
(MFOQA)
– IMDS reduces maintenance
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Diagnostic Monitoring
• IMDS monitors the complete
mechanical drive train
– 27 gears
– 28 shafts
CH-53E example
– 71 bearings
• Automatic health calls are currently
not fully enabled
– Requires adequate experience sample
to set appropriate triggers
– Health calls being made by engineering, pending more data
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Diagnostic Monitoring
Example: SH-60B #1 High-Speed Shaft Coupling, BuNo 161563
#1 HSS Inspected and re-balanced.
No visible defect found
Replaced coupling at request of the
IMDS team
Normal flight data after maintenance
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Diagnostic Monitoring
Example: CH-53E #1 Nose Gearbox, BuNo 162494
Gear tooth fragment found by chip detector
Gearbox removed
First chip detector
fuzz burn-off noted
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IMDS Success Stories
General
Finds aircraft
problems that may
go undetected
Specifics
HSL-41 noted high IMD vibe signature from #3 hangar bearing; subsequent ATABS data collection
showed vibes within limits. Removal and inspection of bearing and shaft showed both worn beyond
limits.
HSL-41 noted multiple engine chip lights recorded by IMDS but cockpit chip caution light did not
illuminate. Inspection revealed faulty chip detector filled with chips.
Finds aircraft
problems before
scheduled
maintenance
HMT-302 automatically acquired ROTABS data showed vibration out of limits. Inspection revealed
three of seven PCR bearings worn beyond limits.
Significantly
reduces
troubleshooting
time
HSL-41 during initial FCF ground turn, IMDS indicated high vibration from drive shaft bearing.
Inspection revealed bearing had disintegrated. ATABS would not have pinpointed problem for at
least three more ground turns.
Enables squadron
to do required
jobs faster
HMT-302 and HSL-41 have noted that main RTB FCFs can be done within one flight.
HMT-302 identified impending failure of #3 engine by strip chart. Engine was approaching high
time. Subsequent inspection indicated excessive wear to power turbine rotor section.
HMT-302 utilized strip chart function to correct engine sympathetic start problems. Able to correctly
identify which hydraulic start valve caused “bleed over”.
HMT-302 has noted reduction in number of required engine performance tests. Able to identify when
an invalid check was performed (i.e., T5 not allowed to stabilize, incorrect OAT readings, etc.).
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In-flight Alerting
• All IMDS data is available to the crew
• Not every IMDS find is brought to the crew’s
attention in flight
– System currently annunciates NATOPS
exceedances
– Alerting for imminent failures requires:
• Larger statistical sample of data
• Rigorous safety hazard analysis
• Expectation is that continuous,
long-term trending will reveal failures early
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Flight Data Recorder Interface
• IMDS enables options for Cockpit Voice/Flight Data Recorder
(CVFDR)
– Current IMDS provides CVFDR interfaces
– P3I version will combine the Main Processor Unit (MPU) with a crashprotected CVFDR
• IMDS can provide any parameter it captures to a CVFDR
– Limited only by available memory
• IMDS data already provides:
– Complete data for every flight
– Flight-to-flight trending
– A powerful tool for mishap investigation
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Military Flight Operations Quality
Assurance (MFOQA)
• A knowledge management process
– using flight data downloaded after every flight
– to provide quantitative performance information regarding
aircrew and aircraft performance
– to improve training, operational readiness and safety.
• IMDS data files support MFOQA applications
– Sufficient parameters and data rates to be useable
– No redundant data collection system required
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IMDS Road Ahead
• Vision for system maturation
– Requires data from more installed systems
• Target areas for improving the system
–
–
–
–
Reliable health calls throughout the mechanical drive train
Begin the move to condition based maintenance
Changes to maintenance concepts
More information in the hands of users
• Application of HUMS as a mature tool
in the next generation of rotorcraft
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Cost Savings Through
Diagnostics
• Fault-based maintenance is an expensive practice
– Reduces availability
– Drives unscheduled maintenance
– May involve collateral damage or flight mishap
• Condition-based maintenance (CBM) is possible –
IF you can first assess “condition”
–
–
–
–
Reduced O&S costs
Increased safety
Increased reliability and availability
More efficient use of personnel through
application of technology
Diagnostic systems, such as IMDS, are key enablers of CBM
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Diagnostic Systems for the
Future Helicopter Fleet
NAVAIR is firmly committed to HUMS
• Enhances current/future readiness
• Reduces cost of doing our business
• Improves agility of our forces
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Questions
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