Dash One Study Guide
Chapter One
What is the basic empty and max takeoff weigh of the T-6?
-Basic Empty Weight4900 lbs
-Maximum Takeoff Gross Weight6500 lbs
What type of engine does the T-6 have?
-Powered by a PT6A-68 free turbo-prop engine
-Engine includes two independent sections: the gas generator section and the power turbine section
-Engine is a reverse flow design
What shaft horsepower and torque does the engine put out?
-Engine is flat rated to produce 1100 shaft horsepower
-By flat rating, engine is able to produce 100% torque from sea level to approx 12000-16000 MSL on a standard day
-At 100% indicated torque, engine is producing approx 2900 ft-lbs of torque at the prop shaft
What are the three systems that comprise the oil system?
-Engine oil system includes a pressure system, scavenge system, and a cooling system with a capacity of 18 US quarts
-Oil system is designed to permit inverted flight operation
-Engine Data Manager (EDM) will activate the red OIL PX annunciator if oil pressure falls below 40 psi when the engine is above IDLE or when the oil pressure drops below 15 psi when the engine is at IDLE
-Power for the oil pressure transducer is on the battery bus
What illuminates when the igniters are turned on?
-When the igniters are turned on (either by the pilot or by the PMU), the green IGN SEL annunciator will illuminate
-Power for the starter and ignition systems is on the battery bus
What does the RGB do?
-The Reduction Gear Box (RGB) reduces the power turbine output shaft speed of over 30000 RPM to the propeller operating speed of 2000 RPM
Where is the chip detector located at?
-The chip detector is located in the RGB and senses ferrous material in the oil. If it senses this, the red CHIP annunciator is activated
What does the RGB do for the PIU, torque probe and PMA?
-RGB also provides drive pads for the propeller interface unit (PIU), torque probe, and the permanent magnet alternator (PMA)
What is located on the right side of the RGB?
-The A/C compressor and jackshaft assemblies are mounted off the right side of the RGB and are driven by pulleys from the propeller bulkhead pulley
What device controls engine power?
-Engine power is controlled by a power control lever (PCL) mounted in the left side of each cockpit
-PCLs are inter-connected with a push-pull rod so that movement of one also moves the other
-Front PCL is connected to the fuel management unit (FMU) both electrically and mechanically (with a flexible cable)
-Friction adjustment is provided in the front cockpit only.
NOTE
To prevent inadvertent engine shutdown, a PCL cut-off gate is provided at the IDLE position on each PCL. To shut the engine down, raise the finger-lift and pull the PCL aft to OFF.
-The PCL in each cockpit contains switches for activating the speed brake, rudder trim, UHF and VHF communications, and intercommunications systems (ICS)
What are the specs of the propeller?
-Propeller is an aluminum, 97-inch, four bladed, constant speed, variable pitch, non-reversing, feathering propeller
What drives the Propeller?
-Propeller is driven by the power turbine through the RGB
What controls blade angle and propeller speed?
-The engine PMU and the PIU automatically control the propeller blade angle (pitch) and propeller speed (NP)
How is Np measured?
-NP is measured by the torque probe
-Propeller system is designed to maintain a constant speed of 2000 RPM (100% NP) during most flight conditions
Where is the propeller pitch change mechanism located and what does it include?
-Propeller pitch change mechanism is mounted to the front propeller hub and includes a sliding hydraulic piston, counterweights, and a feathering spring
How is propeller pitch defined and what is it set by?
-Propeller pitch, which is automatically set by the PMU and PIU, may be defined by three basic conditions: feathered, low pitch (flat or fine), and high pitch (coarse)
How is the propeller pitch angle measured?
-Propeller blade pitch is a measure of the angle between the plane of rotation of the propeller and the chord line of the blade
-When feathered, the propeller blades are aligned nearly straight into the wind
-Feather may be selected by placing the PCL to OFF
In low pitch what is the approx degrees of the propeller to the reference plane?
-When in low pitch, the propeller blade angle is approx 15 from the reference plane
When will the propeller blades be at low pitch?
-Propeller blades will be at low pitch at low speeds and low throttle settings
What is high pitch?
-High pitch is variable between feather and low pitch in order to maintain NP at a constant 2000 RPM for given condition
What controls propeller RPM and how does it do so?
-PMU controls propeller RPM by varying the propeller blade angle with pressure supplied by the engine oil system through the PIU
If the PMU or PIU fails how is Np regulated?
-If PMU or PIU fails, NP is regulated by the mechanical overspeed governor
With the PMU functioning what does the mechanical overspeed governor regulate NP at, electric governor?
-With PMU functioning, the mechanical overspeed governor modulates oil pressure to the propeller pitch change piston to limit NP below 106% (approx 2120 RPM), while the electronic governor will maintain NP at 100%
-If PMU function is lost or deactivated, the mechanical overspeed governor resets to modulate oil pressure to the propeller pitch change piston to maintain NP at or below 100+/-2% (approx 2000 RPM)
With the PMU not functioning NP may peak above 100%, True or False.
-With PMU not functioning, NP may peak above 100% during power changes and then return to the governed range
What does placing the PCL in the off position activate?
-Placing the PCL in the OFF position triggers a micro switch, which activates the feather dump solenoid valve. This dumps propeller oil pressure, allowing the feathering spring and counterweights to feather the propeller
-Power for the feather dump solenoid is located on the battery bus (PROP SYS CIRCUIT BREAKER-two rows from leg, three back from front)
What does the EDM do?
-Engine Data Manager (EDM) is a computer unit which monitors engine operating parameters and illuminates the appropriate advisory, caution or warning annunciator as necessary
-EDM also drives the Primary and Alternate Engine Systems Displays (PEDD and AEDD) as well as the Engine/Systems/NACWS Display
What are some non engine related functions performed by the EDM?
-Non-engine related functions performed by the EDM include fuel balancing and fuel quantity indication, and determination and display of DC volts, DC amps, hydraulic pressure, NACWS, cockpit pressure altitude and cockpit differential pressure
-EDM transmits engine data outputs over the data bus, using EDM A and EDM B channels
What is displayed if the EDM fails?
-If the EDM fails, the affected electronic instrument displays (EIDs) will display EDM FAIL in red text
What does the PEDD show and what measures each thing?
-Primary Engine Data Display (PEDD) presents torque from a signal generated by the phase shift torque probe located in the RGB; propeller RPM (NP), also from a signal generated by the torque probe; indicated outside air temperature (IOAT) from a signal generated by the engine T1 probe, located in the inlet plenum; gas generator speed (N1) from a signal generated by a speed sensor on the aft end of the gas generator section above the starter/generator; and internal turbine temperature (ITT) from the engine ITT sensing system around the combustion chamber
-All of these signals are processed by the PMU and transmitted over a high speed data bus for display in each cockpit
What does the AEDD present?
-Alternate Engine Data Display (AEDD) present alternate torque; alternate N1; cockpit pressure altitude from a signal generated by a sensor in the EDM; cockpit differential pressure (delta p) from a signal generated in the EDM; fuel flow from a signal generated by the fuel flow transducer; left and right fuel quantity from signals generated by the fuel probes in the respective wing and the collector tank; and raw ITT (RITT). Except for torque, none of the above signals are processed by the PMU, but feed directly to the EDM for display on the AEDD. Torque is first determined by the PMU, then sent to the EDM for display. RITT may be used without corrections
-Engine/Systems/NACWS display present oil temperature and oil pressure from signals generated by transducers located on the engine oil pressure line; DC volts and DC amps from a signal generated by the starter/generator voltage regulator; hydraulic pressure from a signal generated by a pressure sensor on the power pack reservoir; and NACWS traffic alerts generated by the NACWS computer
NOTE
When faults are accommodated, EDM FAIL is displayed in the lower portion of the screen on the affected display only. The EDM FAIL message indicates that the EID with the message is not receiving all of the required data in the proper format. With EDM FAIL displayed in the bottom of the display, only those parameters replaced by amber dashes and/or missing pointers are invalid
Parameters on the affected EID which appear normal are functional and may be used normally. All EIDs not displaying the EDM FAIL message are functional and can be used normally. This display logic also applies to ADC FAIL messages on the air data EIDs.
-In ground mode, engine idle N1 is 60% and in the flight mode, idle is normally 67%
-The PMU raises N1 as necessary to maintain NP above 80%, to avoid the propeller restricted speed range during spins
-The PMU provides and autostart capability during ground starts, monitoring engine parameters as the start progresses
-The autostart feature will automatically terminate the ground start sequence upon detection of a malfunction such as a hot, hung, or no start
-The automatic shutdown feature is disabled whenever the PMU is in the flight mode (i.e., airstarts)
-Power setting is linear with PCL position throughout the operating envelope of the aircraft
-Controlled acceleration/deceleration schedules allow PCL movement as rapidly as desired at any altitude
-The PMU also provides transient thrust smoothing, which minimizes propeller effects and avoids large thrust surge on engine acceleration as the propeller stabilizes at operating RPM
-Illumination of both the PMU FAIL and PMU STATUS annunciators indicates the system is in the manual mode
-In the manual mode, engine limits must be maintained by the pilot and care must be exercised to ensure N1, temperature, and torque limits are not exceeded
-If PMU STATUS annunciator comes on one minute after landing, the PMU accommodated a fault in flight and maintenance must be notified
-If PMU STATUS annunciator comes on in flight, it indicates a fault in the weight-on-wheels switch and the PMU will not revert to ground mode upon landing
-If either the PMU FAIL or PMU STATUS annunciators comes on, a PMU reset may be attempted by cycling the PMU switch to OFF and then back to NORM. If the system successfully resets, the PMU FAIL and/or the PMU STATUS annunciators will extinguish and normal operation may be resumed. If the system fails to reset, attempt another reset. If this fails, turn the PMU off and continue the flight in manual mode
-Should IOAT and ITT indications be invalid during high temperature operations (amber dashes and missing ITT pointer with EDM FAIL message in bottom of screen), the PMU should be reset. If successful, amber dashes and the EDM FAIL message will be removed
NOTE
The PMU FAIL and PMU STATUS annunciators will not normally illuminate in this condition
If the PMU fails to reset, attempt a second reset. If this fails, continue the flight in manual mode (if airborne) or abort the mission (if on the ground). Notify maintenance upon landing or following the ground abort
-If the EDM FAIL message was present, but does not appear after the PMU is successfully reset, EDM servicing and/or replacement is not required
-When the PMU shifts from auto to OFF, either by pilot selection or due to an accommodated fault, both the PMU STATUS and PMU FAIL annunciators will illuminate
-A step change in engine power may occur as the fuel flow reverts to a nominal value, but the transition is smooth and is easily controllable
-No step change in NP will occur, since the overspeed governor is automatically reset to 100% when the system switches to the manual mode
-The PMU is normally powered by a dedicated permanent magnet alternator (PMA) mounted on the RGB
-The PMA supplies 32 VAC, which the PMU converts to DC
-If the PMA fails, the PMU automatically switches to the 28 VDC battery bus
-For a normal, PMU monitored start, place the PCL in the START READY position ( green ST READY annunciator illuminates), and place the STARTER switch to the AUTO/RESET position
-The PMU activates the starter, boost pump and igniters, and adds fuel at the proper gas generator speed N1
-Fuel is ignited by the electrical igniters and, with starter assistance, the engine accelerates
-At approx 50% N1 the starter and igniters are de-energized and the boost pump is deactivated if fuel pressure is above 10 psi
-The engine continues to accelerate to idle speed, 60% N1
-The propeller automatically unfeathers during the start as engine oil pressure rises
-The PCL may be advanced to IDLE any time N1 is at or above 60% (two-clicks)
-During a normal (auto) start, the PMU continuously monitors N1, ITT, and fuel flow
-The PMU can automatically stop fuel flow and deactivate the igniters and starter at any time to abort the start if necessary to avoid a hung or hot start or if any engine start parameter is exceeded
-After the PCL has been advanced past the start ready position, the PMU will not cut off fuel to terminate a start
-The start must manually be aborted either by moving the PCL back to OFF, or, if the PCL has not been moved past the IDLE gate, by reselecting the STARTER switch to AUTO/RESET. Either action resets the PMU and aborts the auto-start. If the PCL has been moved past the IDLE gate, the PCL must be moved to OFF to abort the start
-If a start attempt is automatically or manually aborted after fuel has been introduced, the engine must be manually motored for 20 seconds to clear any residual fuel from the engine
CAUTION
When shutting the engine down, verify the PCL is fully in the OFF position to preclude engine damage. If the PCL is left in an intermediate position, fuel flow may continue and cause serious engine damage due to over temperature.
-During a “pilot-monitored” start (also an airstart), the pilot controls fuel scheduling through the PCL. Once N1 reaches 13%, move the PCL to IDLE. During a pilot-monitored start, automatic N1, ITT and torque limit protection is unavailable and the start must be aborted manually
-Fire detection sensor tubes contain helium gas and a hydrogen charged core material
-The helium gas responds to the sensor’s overall threshold temperature (average temperature) for overheat sensing
-The hydrogen charged core responds to localized heat (discrete temperatures) caused by impinging flames or hot gases
-Discrete temperatures result in the release of hydrogen gas from the core, which increases the helium gas pressure
-Heating of the sensor (by average or discrete temperatures) expands the helium gas, which in turn pressurizes a diaphragm inside the responder
-If the diaphragm pressure reaches or exceeds the preset fire detection point, an electrical circuit triggers the overheat/fire alarm
-Triggering the fire alarm illuminates a red FIRE annunciator on each cockpit instrument panel and sounds the master warning horn
-To discriminate between fire or overheat, retard the PCL. If the fire warning ceases, suspect an overheat
-Flattening, twisting, kinking or denting of the fire detection loop will not affect test or flight operation
-In addition to the fire detectors, fire protection is provided by the firewall fluid and cockpit air shutoff valves
-The shutoff valves are mechanically operated by the emergency firewall shutoff handle, placarded EMERGENCY FIREWALL SHUTOFF 1. RLSE GUARD 2. PULL HANDLE, located on the left console panel in the front cockpit
-Cables attached to the handle will close the valves at the firewall, cutting off fuel flow and hydraulic fluid flow to the engine as well as cutting off bleed air flow and hydraulic fluid flow from the engine
-The valves may be reset by pushing the handle down