t-6b propulsion · • controls acceleration and deceleration allowing rapid pcl movement while...

T-6B Propulsion

Created: 12 Sep 2015Updated: 30 Oct 2018

T6BDriver.com

Objectives

• Identify the main sections of the engine and components located within

• Understand the purpose and operation of the Power Management Unit (PMU), Propeller Interface Unit (PIU), and Engine Data Manager (EDM)

• Identify the components and understand the operation of the propeller system

• Identify the components and understand the operation of the fire warning system

• Identify the components and understand the operation of the engine oil system

(Utilize Oil system schematic while reviewing this slideshow)

References

• T-6B NATOPS Manual• Section 1

• Engine• Oil System• Reduction Gearbox (RGB)• Propeller• Start and Ignition System• Power Control Lever (PCL)• Power Management Unit (PMU) Operation• Auto Start Operations• PMU Inoperative (Manual Mode)

• Integrated Avionics System• Engine Data Manager (EDM)

• Fire Warning System

• Firewall Shutoff Handle

• Section 5• Figure 5-1 Instrument Markings

• Figure 5-2 Engine Operating Limits

• Engine Instrumentation Unit Markings• Gauge Marking Logic and Definitions

• Engine Oil Quantity Limitations

• Battery/Starter Limitations• Starter Limitations

• Temperature Limitations

• Propeller Limitations• Propeller Ground Operation Limitations

• Propeller Rotational Overspeed Limitations

• Powered by a PT6A-68 free-turbine engine producing 1100 shaft horsepower (SHP)

• Air cooled oil system provides lubrication to engine bearings, reduction gears, and propeller

• Engine Data Manager (EDM) monitors engine operating parameters and illuminates appropriate EICAS display

• Power Management Unit (PMU) to control auto-starts, ensure ops limits compliance and provide near-linear power response

• Reduction Gearbox (RGB) reduces engine RPM to acceptable levels to drive propeller

• Four-bladed, constant-speed, variable-pitch propeller system

• Dual-sensor tube, fire warning system detects engine compartment overheats/fires

Propulsion System Overview

• Pratt & Whitney PT6A-68 free-turbine, reverse flow, turboprop engine• Free-turbine – Compressor and power turbines not physically connected• Reverse flow – Air starts at back of engine and moves forward• Flat rated to produce 1100 shaft horsepower (SHP)• Engine Data Manager (EDM) monitors engine operating parameters and illuminates appropriate EICAS display• Requires air, fuel, & heat for operation• Basic operation – Suck (intake) / Squeeze (compressor) / Bang (combustion) / Blow (turbines & exhaust)

Engine(General)

Prop Shaft & Flange

Prop Interface Unit (PIU)

Reduction Gear Box (RGB)

Exhaust Case Power TurbineCompressor

Turbine

Combustion Chamber

Centrifugal Compressor

Axial Compressor

Compressor Inlet & Screen

Starter/Generator

Fuel Management Unit (FMU)

Oil Tank

Ignitors

Chip Detector

Permanent Magnet Alternator (PMA)

Accessory Gearbox

• Three major sections of the engine • Accessory Compartment• Gas Generator Section• Power Turbine Section

• Have ability to access accessory compartment via left/right doors

• Gas generation & power turbine sections under cowlings

Engine(Major Sections)

Power Turbine Section

Gas Generation

Section

Accessory Compartment

• Located at rear of engine

• Left side door has 3 engine access latches to secure

• Right side door has 4 engine access latches to secure

• Contains numerous accessory systems for both engine operations and non-engine operations:

• Oil tank• Accessory gearbox (runs/powers accessories)• Starter/Generator• Battery• Hydraulic pump• Engine-driven low pressure fuel pump• External oil scavenge pump• Fuel Management Unit (FMU)• Bleed air heat exchanger

Engine(Accessory Compartment)

Accessory Compartment Door (left side)

Accessory Compartment Door (right side)

Door Latches (3 total)

Door Latches (4 total)

Engine(Accessory Compartment)

Heat Exchanger

Accessory Compartment (left side)

Accessory Compartment (right side)

FMU

Oil Tank

Accessory Gearbox

Ext Oil Scavenge Pump

Starter/ Generator

Battery

Eng Low Press Fuel Pump

Hydraulic PumpFire Warn Responder

Assembly & Sensor Tubes

Oil Sight Gauge

Oil Dip Stick

Engine(Gas Generation Section)

Compressor Turbine

Combustion Chamber


Axial Compressor

Compressor Inlet & Screen

Ignitors

• Mid-section of engine

• Components:• Compressor inlet• Compressor• Combustion chamber• Compressor turbine

• Basic operation• Engine air inlet routes air from nose of aircraft to compressor inlet• Compressor squeezes air• Combustion chamber mixes fuel with air and ignites it• Combustion gases blow across compressor turbine• Compressor turbine extracts energy from gases to turn compressor

• Engine Air Inlet• Air travels aft through the engine air inlet• Passes an inertial separator

• Air makes a 90 degree bend into compressor inlet but heavy particles cannot• Particles drop to bottom of inlet duct• Particles ejected out inertial separator exit port on both sides of cowling

• Compressor Inlet• Inlet encircles entire engine• Screen to protect compressor from FOD

Engine(Gas Generation Section) Engine Air Inlet

Inertial Separator Exit Ports

Compressor Inlet (covered)

Left side Right side



Axial Compressor

• Compressor• Squeezes (compresses) air through 5 stages• 4-stage axial flow

• Axial flow is highly efficient and provides high mass flow rates• Requires multiple stages to achieve higher pressures

• Single stage centrifugal flow• Accelerates flow by slinging air outward (radial flow) which also increases pressure• Lower overall air flow by comparison

• Starter directly rotates compressor for initial air flow into engine

• Combustion Chamber• Mixes fuel with compressed air and ignites the mixture• Uses compressed air as cooling barrier between flame and chamber wall• Fuel nozzles provide fuel in a start pattern or steady-state pattern accordingly• 2 ignitors (4 & 9 o’clock position) in the ignition system used to light mixture

• Compressor Turbine• Extracts power from expanding gases• Drives compressor section of engine

Combustion Chamber

Compressor Turbines


• Starter System• Directly connected to compressor by rod• Provides initial turning of compressor for start (Starter)• When engine running, rod drives magnets around a coil to generate electricity (Generator)• Controls

• STARTER switch on Right Forward Switch Panel (both cockpits)• Powered through CB on Battery Bus CB Panel labeled START• AUTO/RESET

• Spring loaded position which returns switch to NORM• Automatically engages starter and energizes ignition system

• MANUAL• Hard detent switch position• Starter manually engaged and remains so until switch moved to NORM

• Indicators• No “starter” light to advise that starter is engaged• A GEN warning illuminates when starter being used (can only be a starter or generator at one time)

• Limits• Starter limited to four, 20-second cycles with cooling time after each cycle: 30 sec after 1st cycle/2 min after 2nd cycle/5 min after 3rd cycle/30 min after 4th cycle

Starter/Generator

Starter Switch

ROD


• Ignition System• Provides the initial heat source for engine operations• Components

• Exciter box – coverts low voltage to high voltage• Igniter cables – routes high voltage to each igniter• Igniters – located at 4 & 9 o’clock and provide spark for combustion

• Controls• Ignition switch on Right Forward Switch Panel (both cockpits)• ON – Hard selects ignition system to ON & igniters continuously fire• NORM – Allows control of ignition through PMU and auto-start cycle• Powered through CB on Battery Bus CB Panel labeled IGN

• Indicators• A IGN SEL advisory illuminates when ignition system is active

Ignitors

Ignition Switch

Exciter Box

9 o’clock Igniter

4 o’clock Igniter

Igniter Cable

• Front section of engine

• Components:• 2 power turbines• Exhaust case• Reduction gearbox (RGB)• Propeller shaft

• Power Turbines• Utilizes expanding gases generated by gas generation section to produce power• 2 counter-rotating turbines (rotate opposite of compressor turbine) to extract energy from gases• Energy transferred to shaft which connects turbines to RGB• Power turbine shaft rotates at 30,000 RPM

Engine(Power Turbine Section)


Exhaust Case Power TurbinesChip Detector

Prop Shaft

Power Turbine Shaft

• Exhaust System• Exhaust gases pass into exhaust case (or exhaust port)• Gases exit out in to atmosphere via exhaust stacks• Expelled gases provide a small amount of thrust


Exhaust Case Power Turbines

Exhaust Stack

• Reduction Gearbox (RGB)• Two-stage planetary reduction drive• Reduces power turbine shaft speed from 30,000 RPM to 2,000 RPM• Other components mounted to RGB:

• Torque probe• Propeller Interface Unit (PIU) on top• Permanent Magnet Alternator (PMA) on left side• Air conditioning compressor on right side• Chip detector on bottom

• Chip Detector• Mounted on bottom of RGB• Detects ferrous material in oil• A CHIP warning illuminates on EICAS indicating oil contamination

• Engine power is measured by the torque produced by the RGB

• Propeller Shaft• Driven by RGB at a reduced speed (2,000 RPM)• Flange at end to mount propeller system


Power TurbinesChip Detector

Prop Shaft


Power Turbine Shaft

Chip Detector

Torque Probe

PIU

PMA

AC Compressor

• Located in right avionics bay

• Monitors engine operating parameters & illuminates appropriate EICAS displays

• Also performs non-engine related functions:• Fuel balancing• Fuel quantity indication• Determine & display DC Volts/DC Amps• Hydraulic pressure• Cockpit pressure altitude• Cockpit differential pressure

• Channels• Transfers engine data outputs on 2 channels (EDM A / EDM B)• If one output is bad EICAS displays a white advisory light EDM A INOP or EDM B INOP when on the ground• An EDM FAIL warning illuminates on EICAS if EDM fails

• Redundant power through CB on Battery Bus and Generator Bus CB panels

Engine(Engine Data Manager (EDM) )

EDM

Engine(Power Management Unit (PMU) )

• Purpose• Process power requests from PCL and transmits electronically to FMU• Keep engine & propeller within operating limitations• Provide a near-linear power response between the IDLE and MAX

• Located on lower left side of accessory compartment (below battery)

• Power Source• Permanent Magnet Alternator (PMA)

• Mounted on left side of RGB• Powers the PMU• PMA supplies 32 VAC to PMU which then converts it to DC

• PMU automatically converts to 28 VDC Battery Bus when prop RPM drops below 40-50% Np or PMA fails

Permanent Magnet

AlternatorPMU CB

PMU

Engine(Power Management Unit (PMU) )

PMU Switch

• Controls• PMU switch located on Right Forward Switch Panel (front cockpit only)• ON

• PMU selected for operations• PMU monitors ops limits and governs engine

• OFF• PMU selected off (manual mode)• Governing of engine directly controlled by pilot via PCL to FMU (no ops limit protection)• Cause a step change in engine power (normally to lower power condition)

• Indicators• A PMU FAIL warning

• Illuminates if PMU fails• PMU switch placed to OFF position

• A PMU STATUS caution• PMU switch placed to OFF• Illuminates in flight indicating a fault or mismatch between the WOW switches (PMU will not revert to ground idle upon landing)• Illuminates 1 minute after landing (WOW) if fault condition not serious enough to revert to manual are encountered in flight

• Illumination of both PMU FAIL warning & PMU STATUS caution indicates PMU is in manual mode (off line)

• Normal Operations• Interacts with other engine systems to maintain ITT/Torque/N1/Np

• Takes electrical signal from PCL and transmits requests via electrical signal to FMU• Controls acceleration and deceleration allowing rapid PCL movement while minimizing propeller affects and thrust surges• Operates in either flight mode (min N1 at IDLE is 67%) or ground mode (min N1 at IDLE is 60-61%) as activated by WOW switch• Above 10,000 feet PA, PMU raises N1 to maintain Np above 80% to avoid propeller stress during spins

• Auto Start Operations• Provides auto start capability during ground starts by monitoring engine parameters as start progresses• Auto start terminates if:

• No starts – No light-off in 10 seconds of selecting AUTO/RESET with STARTER switch • Hung start – N1 acceleration rate to idle is less than 50% of normal rate• Hot start – ITT appears likely to exceed 840°C for 19 sec / 870°C for 4 sec / 940°C for 2 sec • Only terminates during ground starts• Only terminates if ST READY advisory illuminated (PMU controlled start)

• To begin auto start:• Slowly advance PCL to auto start position until a ST READY advisory illuminates (half way between OFF & IDLE)• Wait 3 seconds to ensure ST READY advisory remains illuminated & PCL was not moved through the position• Select AUTO/RESET with STARTER switch to initiate sequence• PMU activates starter, boost pump, ignitors, and adds fuel at proper N1 speed• At approx. 50% N1 – starter & igniters de-energized and boost pump deactivates when fuel pressure above 10 PSI• At 60% N1 move PCL to IDLE position by advancing until 2 clicks are heard

• Provides auto start capability during air starts but limits protection is unavailable (pilot must monitor)

Engine(Power Management Unit (PMU) ) Starter Switch

PCL Quadrant

Approx. Start Ready Position (not marked)

• PCL in each cockpit connected by a push-pull rod

• Front cockpit PCL connected to FMU by two different methods• Electrically – Via the PMU• Mechanically – Via a flexible cable

• Friction adjustment in front cockpit only

• Lift Cut-Off gate• Prevents inadvertent shutdowns• Must be actuated to move PCL aft of IDLE

• PCL switches• Speed Brake• Rudder trim• UHF/VHF Transmit• Intercomm system

Engine(Power Control Lever)

PCL Quadrant

Friction

PCL (inboard side)

Rudder Trim

Interphone/Mute

UHF (up)VHF (down)

Speed Brake

PCL (forward side)Lift Cut-Off Gate

Cable-FMU Connection

Flexible Cable

FMU

Starter/Gen

Engine(Fire Warning System)

Responder Assembly

Sensor Tubes

• System designed to monitor average & discrete temperatures and warn of fire in engine compartments

• Components• Sensor Tubes

• 2 tubes (fire loop 1 / fire loop 2) for redundancy• Filled with helium gas• Core element inside tube• Responds to average temps for overheat sensing• Not affected by kinks, twist, or dents

• Core Element• Filled with hydrogen gas• Inside sensor tubes• Responds to localized (discrete) temps for overheat sensing

• Responder Assembly• Respond to increased gas pressure in sensor tubes (from heat)• Activates overheat (fire) warning

Engine(Fire Warning System)

Test Switch

Fire Loop 1 (upper half)

• Controls• Fire Test Switch

• Front cockpit only• Tests fire warning system for integrity and lamp operation• Hold to selected loop and get: Master Warning, Fire Light (top or bottom), and aural warning tone

• Firewall Shutoff Handle• Front cockpit only• Shuts off fuel, hydraulic, and bleed air flow from engine• Valves may be reset by pushing handle back in

• Indicators• On left side of glare shield (left of UFCP)• Master Warning

• In each cockpit• Illuminates and flashes when FIRE light illuminates• Aural tone sounds along with light

• Fire annunciator• Illuminated by responder assembly in response to sensing an overheat• 4 total bulbs in light (2 upper/2 lower)• Upper half of light is fire loop 1• Lower half of light is fire loop 2

Fire Loop 2 (lower half)

Fire Warning

Firewall Shutoff Handle

• Converts engine power into thrust

• Uses 97-inch, four-bladed, constant-speed, variable-pitch, non-reversing, feathering propeller

• Maintains constant speed of 2,000 RPM (100% NP) during most flight regimes

• Produces 2,750 pounds of thrust at SL and zero airspeed

• Propeller Pitch (blade angle)• Feathered

• Blades oriented nearly straight into on-coming wind• Blades approx. 86° from perpendicular plane• Produces little drag

• Low Pitch (flat or fine)• Blades approx. 15° from perpendicular plane• Normally at low speeds or low throttle settings

• High Pitch (coarse)• Variable between feather & low pitch• Large “bite” by prop

• Pitch Change Mechanism• Fixed cylinder with sliding piston under nose cone• Oil travels through a tube & stationary transfer sleeve into the hollow rotating prop shaft then to cylinder• Pressurized oil forces piston forward which decreases blade pitch toward fine• Decrease in oil pressure allows piston to move aft which increases blade pitch toward coarse• Loss of oil pressure uses the counterweights and feathering spring to force the prop into feather

Propeller System

• Propeller Interface Unit (PIU)• Located on top of RGB• Responds to power requests from PMU by regulating oil to pitch change mechanism• Electronically governed by PMU (normally) to 100% NP

• Contains a backup mechanical overspeed governor• Used in event PMU turned off or fails• Keeps prop RPM to 100±2% NP

• Propeller Feathering• Prop Servo Valve

• Used if engine is shut down with PCL & PMU in NORM (doesn’t work if PMU is OFF)• PMU sends signal to valve• Quickly drains oil out of pitch change mechanism causing springs & weights to feather prop

• Feather Dump Solenoid Valve• PCL to cutoff activates micro-switches to open valve• Receives power from PROS SYS circuit breaker• Does not require any signal from PMU

• Both valves activate when PCL to cutoff position• Prop Servo Valve works when PMU is NORM vs Feather Dump Solenoid does not depend on PMU

• Propeller Limits• Sustained prop operations on ground between 62 – 80% NP is prohibited due to ground resonance• Prop overspeed limit is 110% NP

Propeller SystemPIU

Prop Sys CB

Oil SystemOil Tank

PumpFwd / Aft

Accessory Gearbox Section

Starter / GeneratorHyd PumpOil PumpOil FilterPMUFuel PumpFMU

-18.5 Qts-Check 15-20 min / Service within 30 min-RGB 30k to 2k RPM-2900 ft-lbs Torque / 2750 lbs Thrust-Pitch

--Feather – 86 deg--Course – Varies--Low – 15 deg

Accessory Compartment (left side)

Oil Tank

Sight Gauge

Dip Stick

Oil Filter

Oil Tank

Accessory Compartment (right side)

Filter

Oil Tank

• Oil system capacity of 18.5 quarts

• Accessible in accessory compartment (left side)

• Oil pump• Internal to oil tank• Ran by accessory gearbox• Two oil pickups:

• One element submerged in oil picks up oil near center of tank

• Second element picks up oil near top of tank (inverted flight)• Limited to 15 seconds inverted/5 seconds intentional zero-G

• Oil Level• Use dipstick to check oil level (sight glass is not to be used)• Service oil level within 30 min of engine shutdown• Check oil level 15 – 20 min after shutdown for most accurate results• Normal oil level is between ADD and MAX HOT• If level is at/below ADD, service level to MAX HOT

• Oil filter• Located in tank (right side)• Filters oil prior to being used• Has bypass option incase filter is clogged

• Oil pressure & temperature sensed by transducers downstream of main pump

• Engine Data Manager (EDM)• Receives pressure & temperature data• Temperature data sent to EICAS gauge• Pressure data sent to Signal Conditioning Unit (SCU) computer

• Signal Conditioning Unit (SCU)• Prevents nuisance caution lights on start• Illuminates the OIL PX warning or OIL PX caution on EICAS• Momentary illumination of the OIL PX caution is possible while maneuvering but may not

indicate a malfunction• Illumination of the OIL PX warning & OIL PX caution with normal oil pressure indicated on the

gauge indicates an SCU failure

• Oil Temperature Gauge

• Oil Temperature Limits• Flight – 10 to 105° C (106 – 110° C transient)• Ground – -40 to 105° C (106 – 110° C ground ops <20% torque)

Oil SystemIndicating System

PumpFwd / Aft

Filter





Oil Press Transducer

Oil Temp Transducer

EICAS

OIL PX

EDM

SCU

OIL PX

Oil Tank

EDM

-40 10 105 106 110

Oil Temp

Start

10 min TransientGrnd Ops < 20% TorqueGround

Flight

0 – 10° C White Arc Scale

10 – 105° C Green Arc Normal

106 – 110° C Amber Arc Caution

110° C Red Radial Maximum

110° C Red Arc Exceedance

• Oil Pressure Gauge• Gauge marked for operations with PCL > idle

• Oil Pressure Limits• PCL @ idle

• 15 – 40 PSI get OIL PX caution• 15 – 40 PSI (after 5 seconds) get OIL PX warning & OIL PX caution• < 15 PSI get OIL PX warning

• PCL > idle• 40 – 90 PSI (after 10 seconds) get OIL PX caution• < 40 PSI get OIL PX warning


PumpFwd / Aft

Filter






Oil Temp Transducer

EICAS

OIL PX

EDM

SCU

OIL PX

Oil Tank

OIL PX

-40 10 105 106 110

Oil Temp

Oil Press (@ Idle)

Oil Press (> Idle)

Start

10 min TransientGrnd Ops < 20% Torque

90 120 200400 15

90 120 200400 15

OIL PX

OIL PX OIL PX 5 sec or >

OIL PX

10 sec

OIL PX

Start

Start

**Transient 40-130 psi for Aero & Spins

EDM

GroundFlight

0 – 40 PSI Red Arc Exceedance

40 PSI Red Radial Minimum

40 – 90 PSI Amber Arc Caution

90 – 120 PSI Green Arc Normal

120 – 200 PSI White Arc Scale

200 PSI Red Radial Maximum

200 – 220 PSI Red Arc Exceedance


PumpFwd / Aft

Filter






Oil Temp Transducer

EICAS

OIL PX

EDM

SCU

OIL PX

Oil Tank

OIL PX

-40 10 105 106 110

Oil Temp

Oil Press (@ Idle)

Oil Press (> Idle)

Start


90 120 200400 15

90 120 200400 15

OIL PX


OIL PX

10 sec

OIL PX

Start

Start


EDM

GroundFlight

Oil Pressure Warning/Caution Indications (> Idle)

Oil Pressure Warning/Caution Indications (@ Idle)

Click on video to play

• Oil system delivers pressurized oil to:• Accessory gear box• Gas generation section bearings• Power turbine section bearings• Reduction gear box gearing• PIU (to be sent to prop)

• Oil System Limits• Oil system viable for normal and aerobatic flight• Limited to 60 seconds negative G operations (with limitations)

• Negative G maneuvers within 60 seconds followed by 60 seconds upright before conductingadditional negative G maneuvers

• Do Not exceed -2.5 G for negative operation longer than 30 seconds

• Limited to 5 seconds intentional zero-G• Holding a zero-G load for over 5 seconds may cause engine damage and failure regardless of oil

pressure indications

Oil SystemPressurized Delivery

PumpFwd / Aft

Filter






Oil Temp Transducer

EICAS

OIL PX

EDM

SCU

OIL PX

Oil Tank

OIL PX

-40 10 105 106 110

Oil Temp

Oil Press (@ Idle)

Oil Press (> Idle)

Start


90 120 200400 15

90 120 200400 15

OIL PX


OIL PX

10 sec

OIL PX

Start

Start


EDM

GroundFlight

Reduction Gear Box

Gas Generation

Section


Compressor Bearings

TurbineBearings

PIU

PMU

AGB Bearings

Accessory Gear Box

RGB BearingsDump

Sol

• Oil scavenged in system via internal scavenge pump (in oil tank) and external scavenge pump (outside of oil tank)

• Both pumps are dual-element gear-type pumps

• Internal Oil Scavenge Pump• Inside oil tank• Scavenges oil from accessory gearbox bearings and front compressor bearing (housed inside oil tank)• Sends oil through oil cooler prior to returning to tank

• External Oil Scavenge Pump• External to oil tank• Shares same AGB drive shaft as engine driven low pressure fuel pump• Scavenges oil from rear compressor bearing, turbine bearings, RGB bearings, and prop system• Sends oil through oil cooler prior to returning to tank

PumpFwd / Aft

CHIP

FilterReduction Gear Box

Gas Generation

Section


Oil Tank


Compressor Bearings

TurbineBearingsRGB

Bearings


Oil Temp Transducer

EICAS

PIU

PMU

Chip Detector

OIL PX

Dump Sol

Ext Scavenge PumpFwd / Aft

Oil Cooler

Int Scavenge PumpFwd / Aft




OIL PXEDM

SCU

EDM

Oil SystemScavenge System

OIL PX

-40 10 105 106 110

Oil Temp

Oil Press (@ Idle)

Oil Press (> Idle)

Start


90 120 200400 15

90 120 200400 15

OIL PX


OIL PX

10 sec

OIL PX

Start

Start


GroundFlight

Oil Cooler Intake External Scavenge Lines

Chip Detector

AGB Bearings

Accessory Gear Box

External Scavenge Pump

Conclusion

Abnormal Engine/Oil Scenarios located in Procedures Section/EPs

• Identified the main sections of the engine and components located within

• Discussed the purpose and operation of the Power Management Unit (PMU), Propeller Interface Unit (PIU), and Engine Data Manager (EDM)

• Identified the components and discussed the operation of the propeller system

• Identified the components and discussed the operation of the fire warning system

• Identified the components and discussed the operation of the engine oil system

t-6b propulsion · • controls acceleration and deceleration allowing rapid pcl movement while...

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