T-6B Propulsion. Created: 12 Sep 2015 Updated: 07 Dec 2016 T6BDriver.com

T-6B Propulsion Created: 12 Sep 2015 Updated: 07 Dec 2016 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

Propulsion System Overview 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

(General) 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) Reduction Gear Box (RGB) Ignitors Prop Interface Unit (PIU) Combustion Chamber Centrifugal Compressor Axial Compressor Oil Tank Accessory Gearbox Prop Shaft & Flange Starter/Generator Permanent Magnet Alternator (PMA) Fuel Management Unit (FMU) Chip Detector Exhaust Case Power Turbine Compressor Turbine Compressor Inlet & Screen

(Major Sections) 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 Power Turbine Section Accessory Compartment Gas Generation Section

(Accessory Compartment) Accessory Compartment Door (left side) 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 Accessory Compartment Door (right side) Door Latches (3 total) Door Latches (4 total)

(Accessory Compartment) Accessory Compartment (left side) Accessory Compartment (right side) Oil Dip Stick Oil Sight Gauge Oil Tank Starter/ Generator Accessory Gearbox FMU Heat Exchanger Fire Warn Responder Assembly & Sensor Tubes Hydraulic Pump Ext Oil Scavenge Pump Battery Eng Low Press Fuel Pump

(Gas Generation Section) 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 Combustion Chamber Ignitors Centrifugal Compressor Axial Compressor Compressor Turbine Compressor Inlet & Screen

(Gas Generation Section) Engine Air Inlet 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 Compressor Inlet (covered) Inertial Separator Exit Ports Left side Right side

(Gas Generation Section) 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 Centrifugal Compressor Axial Compressor Compressor Turbines

(Gas Generation Section) 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 1 st cycle/2 min after 2 nd cycle/5 min after 3 rd cycle/30 min after 4 th cycle Starter/Generator Starter Switch ROD

(Gas Generation Section) 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 9 o clock Igniter Igniter Cable Exciter Box Ignition Switch Ignitors 4 o clock Igniter

(Power Turbine Section) 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 Reduction Gear Box (RGB) Power Turbine Shaft Prop Shaft Chip Detector Exhaust Case Power Turbines

(Power Turbine Section) 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 Stack Exhaust Case Power Turbines

(Power Turbine Section) 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 Torque Probe PIU PMA AC Compressor Chip Detector Propeller Shaft Driven by RGB at a reduced speed (2,000 RPM) Flange at end to mount propeller system Reduction Gear Box (RGB) Power Turbine Shaft Prop Shaft Chip Detector Power Turbines

(Engine Data Manager (EDM) ) 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 EDM Redundant power through CB on Battery Bus and Generator Bus CB panels

(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% N p or PMA fails PMU Permanent Magnet Alternator PMU CB

(Power Management Unit (PMU) ) 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) PMU Switch

(Power Management Unit (PMU) ) Starter Switch Normal Operations Interacts with other engine systems to maintain ITT/Torque/N 1 /N p 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 N 1 at IDLE is 67%) or ground mode (min N 1 at IDLE is 60-61%) as activated by WOW switch Above 10,000 feet PA, PMU raises N 1 to maintain N p 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 N 1 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 N 1 speed At approx. 50% N 1 starter & igniters de-energized and boost pump deactivates when fuel pressure above 10 PSI At 60% N 1 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) PCL Quadrant Approx. Start Ready Position (not marked)

(Power Control Lever) PCL in each cockpit connected by a push-pull rod FMU Starter/Gen Flexible Cable Front cockpit PCL connected to FMU by two different methods Electrically Via the PMU Mechanically Via a flexible cable Cable-FMU Connection Friction adjustment in front cockpit only Lift Cut-Off gate Prevents inadvertent shutdowns Must be actuated to move PCL aft of IDLE PCL Quadrant PCL switches Speed Brake Rudder trim UHF/VHF Transmit Intercomm system Friction PCL (inboard side) PCL (forward side) Lift Cut-Off Gate Speed Brake Interphone/Mute UHF (up) VHF (down) Rudder Trim

(Fire Warning System) 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 Responder Assembly Sensor Tubes

(Fire Warning System) 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 Test Switch 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 1 (upper half) Fire Warning Fire Loop 2 (lower half) Firewall Shutoff Handle

Propeller System 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% N P ) 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 PIU 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% N P Contains a backup mechanical overspeed governor Used in event PMU turned off or fails Keeps prop RPM to 100±2% N P 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% N P is prohibited due to ground resonance Prop overspeed limit is 110% N P Prop Sys CB

-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 Gearbox Section Filter Starter / Generator Hyd Pump Oil Pump Oil Filter PMU Fuel Pump FMU Pump Fwd / Aft Oil Tank Oil System 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 Dip Stick Accessory Compartment (left side) Oil filter Located in tank (right side) Filters oil prior to being used Has bypass option incase filter is clogged Accessory Compartment (right side) Sight Gauge Oil Tank Oil Tank Oil Filter

-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 Gearbox Section Starter / Generator Hyd Pump Oil Pump Oil Filter PMU Fuel Pump FMU Oil Press Transducer Oil Temp Transducer EDM SCU EDM EICAS Oil System Indicating System 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 Filter Pump Fwd / Aft Oil Temp -40 10 105 106 110 Start Flight Ground 10 min Transient Grnd Ops < 20% Torque Oil Tank Signal Conditioning Unit (SCU) Prevents nuisance caution lights on start Illuminates the warning or caution on EICAS Momentary illumination of the caution is possible while maneuvering but may not indicate a malfunction Illumination of the warning & caution with normal oil pressure indicated on the gauge indicates an SCU failure Oil Temperature Gauge 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 Temperature Limits Flight 10 to 105 C (106 110 C transient) Ground -40 to 105 C (106 110 C ground ops <20% torque)

-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 Gearbox Section Starter / Generator Hyd Pump Oil Pump Oil Filter PMU Fuel Pump FMU Oil Press Transducer Oil Temp Transducer EDM SCU EDM EICAS Oil System Indicating System Oil Pressure Gauge Gauge marked for operations with PCL > idle 0 40 PSI Red Arc Exceedance 40 PSI Red Radial Minimum 40 90 PSI Amber Arc Caution Oil Tank Filter 90 120 PSI Green Arc Normal Pump Fwd / Aft 120 200 PSI White Arc Scale 200 PSI Red Radial Maximum 200 220 PSI Red Arc Exceedance Oil Temp -40 10 105 106 110 Start Oil Press (@ Idle) 0 15 Flight Ground 40 10 min Transient Grnd Ops < 20% Torque 90 120 200 Oil Pressure Limits PCL @ idle 15 40 PSI get caution 15 40 PSI (after 5 seconds) get warning & caution < 15 PSI get warning PCL > idle 40 90 PSI (after 10 seconds) get caution < 40 PSI get warning Start Oil Press (> Idle) 0 15 5 sec or > 40 **Transient 40-130 psi for Aero & Spins 90 120 200 10 sec Start

Dump Sol PMU PIU Reduction Gear Box RGB Bearings -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 Power Turbine Section TurbineB earings Gas Generation Section Compressor Bearings Accessory Gearbox Section Filter Starter / Generator Hyd Pump Oil Pump Oil Filter PMU Fuel Pump FMU Oil Press Transducer Oil Temp Transducer Pump Fwd / Aft EDM SCU EDM Oil Tank EICAS Accessory Gear Box AGB Bearings Oil System Pressurized Delivery 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 15 seconds inverted flight 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 Temp -40 10 105 106 110 Start Flight Ground 10 min Transient Grnd Ops < 20% Torque Oil Press (@ Idle) 0 15 40 90 120 200 Start Oil Press (> Idle) 0 15 5 sec or > 40 **Transient 40-130 psi for Aero & Spins 90 120 200 10 sec Start

-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 Gearbox Section Starter / Generator Hyd Pump Oil Pump Oil Filter PMU Fuel Pump FMU SCU EICAS Oil System Scavenge System Oil scavenged in system via internal scavenge pump (in oil tank) and external scavenge pump (outside of oil tank) Dump Sol Chip Detector CHIP PMU PIU Reduction Gear Box RGB Bearings Power Turbine Section TurbineB earings Gas Generation Section Compressor Bearings Oil Press Transducer Oil Temp Transducer Filter Pump Fwd / Aft Int Scavenge Pump Fwd / Aft Ext Scavenge Pump Fwd / Aft EDM EDM Oil Tank Oil Cooler Accessory Gear Box AGB Bearings 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 Oil Temp -40 10 105 106 110 Chip Detector Start Flight Ground 10 min Transient Grnd Ops < 20% Torque Oil Press (@ Idle) 0 15 40 90 120 200 Start Oil Press (> Idle) 5 sec or > **Transient 40-130 psi for Aero & Spins Oil Cooler Intake External Scavenge Lines 0 15 40 90 120 200 Start External Scavenge Pump 10 sec

Conclusion 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 Abnormal Engine/Oil Scenarios located in Procedures Section/EPs