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ABSTRACT – T400 and T53 Engine Life Management
1. Overview
Mercer Engineering Research Center (MERC) currently provides structural fleet management
support for the United States Air Force (USAF) fleets of UH-1N and TH-1H helicopters. This
support could be extended and leveraged to include engine life management for the T400 and
T53 engines on those aircraft. Existing Loads / Environment Spectra Survey (L/ESS) systems
and/or planned Health and Usage Monitoring (HUMS) systems could be used to monitor engine
components and usage. The Aging Fleet Integrity and Reliability Management – Multi-Platform
(AFIRM-M) web-based fleet management tool could be extended to aggregate and display this
data to stakeholders.
2. L/ESS to Enable Engine Life Management
MERC operates and maintains the L/ESS systems on the USAF UH-1N and TH-1H fleet. Seven
TH-1H and fourteen UH-1N aircraft are currently instrumented with these systems, which
capture aircraft parameters for each flight. Data from these systems is used to track fleet usage.
MERC developed regime recognition algorithms for both aircraft data sets that were validated
with prescribed regime flight tests. Figure 1 shows selected parameters for a portion of a UH-1N
flight and the regimes that were recognized during that segment. Table 1 shows the calculated
UH-1N usage spectrum, which is being used by the USAF and the aircraft OEM to update
dynamic component replacement times. While the only directly-measured engine parameter on
the UH-1N L/ESS system is Engine Torque, it is possible that the calculated regimes could
enable life cycle management for the T400 engines on these aircraft. Monitoring of additional
parameters is discussed in Section 3.
Figure 1. UH-1N Regime Recognition Example
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Table 1. UH-1N Usage Spectrum as of 1 Jan 2017
Regime
Normal Start
Shutdown (w/Coll)
Flight Idle
FPG (Nr ~100%)
Takeoff
Hover
Hover Control Reversal
Landing/Approach
Level Flight
Climb
Pull-ups
Level Flight Left Turn
Level Flight Right Turn
Flight Control Reversal
Descent
Twin to Single
Single to Twin Descent, 1 sec
Fire Sup. Push-Over, Dive, PullUp
Fire Sup. Left Turn
Fire Sup. Right Turn
Autorotation
Other
Total
Time
(hours)
87.9
22.8
171.3
286.5
15.5
160.3
21.5
38.2
987.4
145.0
3.0
155.0
168.7
4.2
Time
(%)
3.63%
0.94%
7.08%
11.83%
0.64%
6.62%
0.89%
1.58%
40.79%
5.99%
0.12%
6.40%
6.97%
0.17%
118.5
4.89%
0.0
0.0
0.00%
0.00%
0.3
0.01%
11.0
0.46%
9.5
0.39%
12.3
0.51%
1.9
0.08%
2420.7 100.00%
The TH-1H L/ESS system captures a fairly complete suite of engine parameters, including
Engine Gas Generator Speed (NG1), Engine Power Turbine Speed (NG2), Engine Oil Pressure,
Engine Oil Temperature, Engine Torque, and Engine Gas temperature. L/ESS data has been
used in the past to calculate T53 engine rotating component service cycles per Honeywell
Service Bulletin T53-L-703-0020. Table 2 shows the results of these calculations for the 20162017 operating year. This data is clearly suited for life cycle management of the T53 engine and
can be used to compare TH-1H usage to the commercial usage that the engine was designed for.
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Table 2 Total turbine component cycles for 2016-2017 operating year
Tail Number
71-XXXXX
73- XXXXX
74- XXXXX
74- XXXXX
72- XXXXX
PilotReported
Flight
Time
(hrs)
248.6
141.5
68.3
352.3
213.8
GAG
Cycles
1392
94
259
2218
1347
Average
Compressor
GP
Centrifugal
Total N1
max
Component Component Compressor
increases
N1%
Cycles
Cycles
Cycles
95.4
95.4
95.1
94.6
95.2
795
568
98
1140
825
103.4
74.5
19
144.7
115
204.8
147.2
31.4
288.1
221.6
103.4
76
19
147.5
119.2
Although only seven TH-1H aircraft are instrumented with L/ESS, MERC believes that the data
from these aircraft can be used for engine health monitoring of the entire TH-1H fleet. All TH1H aircraft are used for training future pilots. The USAF keeps records of sortie types for all
TH-1H flights which are accessible by MERC via the Graduate Training Integration
Management System (GTIMS). Engine parameters for each GTIMS sortie type can be
characterized for the aircraft instrumented with L/ESS. This information can be generalized to
aircraft without L/ESS (based on the GTIMS data for each tail number) through statistical
methods which account for the variance within sortie type. MERC will leverage its past success
in using GTIMS data to characterize the regimes of the TH-1H training syllabus.
3. HUMS to Enable Engine Life Management
MERC designed, developed, and installed a prototype Health and Usage Monitoring System
(HUMS) on one USAF UH-1N aircraft, that system records Engine Gas Generator Speed (NG1),
Engine Power Turbine Speed (NG2), Engine Oil Pressure, Engine Oil Temperature, and Engine
Torque for both of the T400 engines on the aircraft. A block diagram of the system can be seen
in Figure 2 below; an overview of the installed tachometers and accelerometers can be seen in
Figure 3. This modification is expected to be installed across a majority of the USAF UH-1N
fleet in the coming years. Parametric data from this system could be leveraged for engine life
management purposes, using MERC’s regime recognition experience to characterize engine
usage across the fleet. The system has capacity for additional accelerometers / tachometers;
adding sensors to directly monitor engine vibration signatures is possible. This would allow a
much richer data set and enable CBM+ on the T400 engine.
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Figure 2. Block diagram of the HUMS/CVFDR modification
Figure 3. Installation location of accelerometers and tachometers
4. AFIRM-M to Enable Engine Life Management
AFIRM-M is a web-based fleet management tool that supports the structural and mechanical
integrity programs for the TH-1H and UH-1N, along with several other DOD weapons systems.
A screen shot of the UH-1N landing page can be seen in Figure 4. The site is located at
https://afirm.merc-mercer.org/AFIRM/Login.aspx. AFIRM-M houses and aggregates pilot4
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reported usage, L/ESS regime data, TH-1H training sortie data, maintenance data, and other
information that could be used toward engine life cycle management. It is also expected to be
the data transfer mechanism for UH-1N HUMS. The addition of engine data and analysis to the
suite of tools in AFIRM-M would allow stakeholders at the engine SPO, MAJCOMs, operators,
and others to track engine health in near real-time.
Figure 4. UH-1N AFIRM-M Landing Page
5. Summary
MERC has extensive experience with data collection and analysis on the UH-1N and TH-1H
helicopters. Systems that MERC designed, and developed can be leveraged for T400 and T53
engine data collection and analysis. Development of these engine analysis tools could be
accomplished in a cost-effective manner, allowing the USAF to develop an engine sustainment
strategy that ensures safety of the fleet.
6. Contact Information
Technical – Brian D. Harper, [email protected], 478-953-6800 x2431
Contracting – Andrea Mitchell, [email protected], 478-953-6800 x2410
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