flight test evaluation of c-130h aircraft performance … test evaluation of c-130h aircraft...
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Lance Bays Lockheed Martin - C-130 Flight Sciences
Telephone: (770) 494-8341 E-Mail: [email protected]
Flight Test Evaluation of C-130H Aircraft Performance with NP2000
Propellers
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Introduction
• Flight tested a C-130H to determine impact of new 8-bladed NP2000 propellers on aircraft performance
• Used modern instrumentation and test techniques • Assessed effects on all phases of flight:
– Takeoff, climb, cruise, descent, landing
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Background – NP2000
Projected benefits: • Increased thrust at equivalent engine torque • Reduced vibration • Less far-field noise • Improved reliability and maintainability
• Eight-blade propeller system by Hamilton Sundstrand • Composite blades with graphite epoxy spar and Kevlar cover • Modular hydraulic control system to control pitch angle • In service with U.S. Navy E-2 fleet
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Motivation
• New York Air Guard operates ski-equipped LC-130H aircraft from snow-covered surfaces
• During a ski-takeoff, skis “hang up” at approximately 60 knots
• Jet-Assisted Takeoff (JATO) bottles augment acceleration • Cost of JATO bottles expected to become prohibitive
Increased thrust from the NP2000 proposed as cost-effective means of providing the necessary increase in thrust required for ski operations
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Test Objective
• Quantify effect of new propeller on aircraft performance – The propeller changes:
• Minimum control speeds • Airfield performance (takeoff and landing) • Airborne performance (climb, acceleration,
cruise, deceleration, and descent) – Devised a suitable test plan to quantify the changes
for all affected phases of flight
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Approach: Performance Modeling
Modeling airplane performance requires models of thrust and drag Assumed a traditional flight test approach:
– Use in-flight thrust model with a predicted propeller map – Convert engine torque (measured) to net propeller thrust – Airplane drag derived from computed thrust and measured flight
conditions – The drag model is a byproduct of the in-flight thrust model
During flight test: •Drag can never be measured directly •Thrust can only be measured at static conditions
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Flight Test
• Test aircraft: C-130H from the Wyoming Air National Guard with T56-A-15 engines and NP2000 propellers
• Included an Electronic Propeller Control System (EPCS) that replaced the
existing mechanical propeller control unit • Remainder of the propulsion system (power section, reduction gearbox, propeller
brake, safety coupling, etc.) identical to baseline C-130H configuration • Tests conducted by 418th flight test squadron at Edwards Air Force Base from
June 2010 to February 2011
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Flight Test Plan
• Thrust stand • Measurements installed torque and net thrust statically • Calibrate engine and propeller measurements
• Airborne performance • Stabilized cruise test points (range performance) • Segmented climbs and descents • Level accelerations and decelerations
• Airfield performance testing • Takeoff • Rejected takeoff • Landing
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Thrust Stand Testing
• Only condition where thrust directly measurable • Collected data for ground idle, flight idle, maximum power, and
intermediate power settings • Quantified engine performance (torque versus turbine inlet temp) • Evaluated available propeller models (thrust at static condition)
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Cruise Testing
• A cruise test point consists of trimmed flight at stabilized speed and altitude, with engines thermodynamically stabilized
• Flown across envelope at a range of speeds/altitudes • Validated predicted vs. measured engine parameters • Determined drag • Characterized range performance
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Cruise Testing – Thrust Validation
• Used engine torque as input to engine deck to compute blade angle, net thrust, fuel flow for all four engines
• Compared computed to test measured values
• Excellent correlation
y = 0.9853x - 0.2520R² = 0.9995
20
25
30
35
40
45
50
20 25 30 35 40 45 50
Pred
icte
d Bl
ade
Ang
le -
deg
Test Measured Blade Angle - deg
• Blade angle provided an independent indication/verification of engine torque and propeller thrust (sample shown here - all cruise test points for engine #1)
Test Measured Blade Angle Pr
edic
ted
Bla
de A
ngle
Slope =~1 R2 = ~ 1
Typical Correlation - Engine #1 Blade Angle
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Cruise Range Performance
• Cruise range performance characterized by specific range (SR)
• SR = nautical miles per pound fuel
• Specific range test data indicated similar or slightly improved over baseline model
100 150 200 250 300 350
SR -
nm/1
,000
lb
KTAS
Test NP2000, Raw
Test NP2000, Standardized
H Baseline (54H60) Predicted, Std Conditions, +20 countsPoly. (Test NP2000, Standardized)
True Air Speed
Spec
ific
Ran
ge –
nm
/lb
Typical Range Performance, Fixed Altitude Cruise
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Climb and Descent Testing
• Climb and descent performance is characterized by excess power
• Excess power = margin of thrust minus drag available for the airplane to climb and/or accelerate at some give airspeed and weight
• Quantified via two types of tests: – (1) sawtooth climb (and sawtooth descent) – (2) level acceleration (and level deceleration)
• Data obtained from these tests quantify specific excess power characteristics of the aircraft at fixed power settings
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Sawtooth Climb
• Involve two climbs across a nominal test altitude on reciprocal headings perpendicular to the prevailing wind
• Minimize wind effects • Climb initiated well below target altitude to allow speed and
power to stabilize • A thermodynamically stable engine allows better in-flight
thrust calculation
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100 110 120 130 140 150 160 170 180
Rate
of C
limb
-fee
t/m
inut
e
KCAS
Test StandardizedBaseline H + 20 cts
- Standardized R/C corrected to std day, std weight, zero accel.- Baseline is model +20 counts drag, 4-blade N54H60, std day.
• Exception at 100% flaps • Greatest turning of slipstream • Possible slipstream effects
100 110 120 130 140
Rate
of C
limb
-fee
t/m
inut
e
KCAS
Test Standardized Baseline H + 20 ctsPoly. (Test Standardized)
- Standardized R/C corrected to std day, std weight, zero accel.- Baseline is model +20 counts drag, 4-blade N54H60, std day.
Sawtooth Climb Results
• Test data generally indicate excess power improved for flaps up and flaps 50%
Typical Flaps Up and Flaps 50%
True Air Speed
True Air Speed
Typical Flaps 100%
Rat
e of
Clim
b –
ft/m
in
Rat
e of
Clim
b –
ft/m
in
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Level Accelerations
• Alternate method for determining the excess power • More efficient than sawtooth climbs • For a level acceleration, aircraft climbs at target power setting
at initial speed until the target altitude is reached and aircraft transitions to a horizontal acceleration
• Initial climb at the target power setting stabilizes engine for in-flight thrust calculation
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Level Acceleration Results
• Data agree with sawtooth climb results and indicate improved excess power
• Level accelerations provided more data (larger speed band) over much fewer test points than sawtooth climbs
• Unfortunately, no accelerations with 100% flaps data available to corroborate sawtooth climb results
100 110 120 130 140 150 160 170 180 190 200Ra
te o
f Clim
b -f
eet/
min
ute
KCAS
Test StandardizedBaseline H + 20 cts
- Standardized R/C corrected to std day, std weight.- Baseline is model +20 cts drag, 4-blade N54H60, std day.
True Air Speed R
ate
of C
limb
– ft
/min
Typical Flaps Up and Flaps 50%
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Airfield Performance
• Takeoff and landing quantified by physical models that include: – Thrust (takeoff power, ground idle and flight idle) – Aerodynamics – Flight test constants and correlation factors, including transitions (engine
failure recognition, brake application, etc.) • Include effects of minimum control speeds
– Tested as prerequisite to takeoff testing – Minimum control speeds increased as a consequence of increased thrust – Determines minimum lift-off speed (VMCA - min control speed in the air ) – Determines minimum go-speed (VMCG - minimum control speed on the
ground) – Critical field length for takeoff accounts for engine failure
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4-Engine Takeoff
• Increase in net thrust resulted in increased low-speed acceleration (~20% at sea level/ISA and high/hot)
• Reduced 4-engine takeoff distances (both ground roll and distance to 50 feet)
4-Engine Distance to 50 feet: Sea level, standard day, and 4,000’ PA, ISA+30ºC
80 100 120 140 160 180
Take
-off
Dist
ance
to 5
0 fe
et
Gross Weight - 1,000 pounds
54H60 Props (Solid Lines)NP2000 Props (Dashed Lines)
Gross Weight
Take
off D
ista
nce
to 5
0 Fe
et
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Normal Takeoff – Critical Field Length
• Mixed impact on CFL due to increase in VMCG and VMCA
• Used MIL-STD-3013A rules • Better at some conditions, worse at
others • CFL slightly increased at
conditions of weight, altitude, temperature where minimum control speeds govern takeoff
• Mitigation of increased minimum control speeds would help
80 100 120 140 160 180
Criti
cal F
ield
Len
gth
(CFL
)
Gross Weight - 1,000 pounds
54H60 Props (Solid Lines)NP2000 Props (Dashed Lines)
Critical Field Length: Sea Level, Standard Day, and 4,000’ PA, ISA+30ºC
Gross Weight
Cri
tical
Fie
ld L
engt
h
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Landing
• Increase in net thrust at flight idle increased touchdown speed and increased air distance
• Decreased reverse thrust at low speed increased ground roll
80 100 120 140 160 180
Land
ing
Dis
tanc
e
Gross Weight - 1,000 pounds
54H60 Props (Solid Lines)NP2000 Props (Dashed Lines)
Flaps 100%4 Engines in Max Reverse3,000 PSI Brakes
Landing Distance: Sea level, standard day
Gross Weight
Lan
ding
Dis
tanc
e
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Conclusions
• Airborne performance: • Greater climb and acceleration capability compared to the baseline model
of the aircraft (exception at the 100%-flap) • Similar or slightly improved range performance compared to baseline
• Airfield performance • Reduced max-effort and 4-engine takeoff distances • Mixed picture for normal takeoff (critical field length)
• Slightly increased at conditions of weight, altitude, temperature where minimum control speeds set takeoff speeds
• Decreased at all other conditions • Mitigation of increased minimum control speeds would help
• Increased landing distances due to changes to flight idle, ground idle and reverse thrust
• Potential for improvement via adjustments to blade angle schedule
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Questions?
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Back-Up
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Handling Qualities
• Limited sideslip testing performed – Indicated rudder force lightening
• benefit to adding a sideslip indication system
• No stall testing performed – Tested in previous phase – Lockheed Martin reviewed data -
• stall characteristics degraded • strong benefit to adding artificial stall warning
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26
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