TH-67 Aircraft Systems Part 2
TH-67 Power Train Systems
ELO #1
Q: State the purpose of the power train system
A: The power train system provides a means of transmitting engine power to the main and tail rotor systems.
Q: State the purpose of the freewheeling unit/sprang clutch assembly.
A: The sprag clutch in the freewheeling unit provides a disconnect from the engine enabling autorotational forces to drive the transmission, tail rotor, and all transmission mounted accessories in the event of an engine failure.
Q: What is the lubrication source for the freewheeling unit?
A: The freewheeling unit is lubrication by transmission oil.
Q: Does the freewheeling unit have a chip detection capability?
A: Yes, but the chip detector is not electrically wired for a “Caution Light” indication in the cockpit.
Q: What does the main drive shaft connect?
A: It is a flexible coupling that connects the freewheeling unit to the transmission input drive.
Q: Why is the main drive shaft a flexible coupling?
A: The movement between the transmission (a floating pylon mount) and the freewheeling unit mounted on the engine (a rigid mount) requires a flexible coupling.
Q: In the event of an engine failure, what drives the tail rotor in autorotation?
A: The main drive shaft transfers transmission RPM (inflow of air through the rotor system) to the freewheeling unit to drive the tail rotor.
ELO #2
Q: What mounting technique is use to secure the transmission to the airframe?
A: An isolation mounting technique (it is not rigidly mounted.)
Q: What is the purpose of the pylon support links?
A: To mount the transmission to the airframe and bear the aircraft’s weight.
Q: What effect does a focused pylon mount have on the transmission?
A: A focused pylon mount lowers the CG of the transmission. This reduces the transmission’s movement.
Q: Why is the transmission mounted with a 5 degree forward tilt?
A: To provide a more comfortable attitude in forward flight.
Q: Why is the transmission mounted with a 1.25 degree tilt to the left?
A: To help compensate for translating tendency.
Q: What does a rubber isolation mount provide?
A: A rubber isolation mount provides for lateral centering and shock absorption.
Q: What does the drag link’s round pin and the pylon stop’s square hole provide?
A: Positive travel limits for the pylon
ELO #3
Q: Where does the TRANS OIL TEMP caution light get its information?
A: From the switch located on the transmission oil filter’s housing.
Q: Where does the transmission oil temperature gauge get its information?
A: From a thermo bulb/transducer on the oil filter’s housing.
Q: Does the transmission oil cooler have a bypass capability?
A: The transmission oil cooler has a thermal bypass at temperatures below 71 degrees Celsius. Above 81 degrees the bypass valve closes and the oil must be cooled.
Q: How is the transmission oil cooled?
A: A flexible duct/hose assembly transports cooling air from the engine oil cooler housing to the transmission oil cooler where some air about to cool the transmission oil is scavenged to cool the hydraulic reservoir.
Q: How many chip detectors are there on the transmission oil system?
A: There are four transmission chip detectors (sump, pump, chip pan, and freewheeling unit) on the oil system.
Q: How many chip detectors are there on the transmission that can activate the TRANS CHIP caution light?
A: There are three chip detectors (sump, pump, chip pan) that can activate the TRANS CHIP caution light.
Q: Where is the transmission oil level sight glass located?
A: The sight glass is located on the right side of the transmission.
ELO #4
Q: What are the three splined areas on the mast?
A: The mast is splined to the planetary gear case, the collar set, and the trunnion.
Q: Why is the mast hollow?
A: A hollow mast is stronger, flexible, and a lighter weight.
ELO #5
Q: How many tail rotor drive shaft segments are there?
A: There are eight tail rotor drive shaft segments. Two are made of steel, and six are aluminum alloy.
Q: How many tail rotor drive shaft segments are on top of the tail boom section of the aircraft?
A: Five of the eight tail rotor drive shaft segments are on top of the tail boom.
Q: What are the hanger bearing assemblies used for?
A: Hanger-bearing assemblies are used to support the drive shaft and maintain drive train alignment in its position over the tail boom.
Q: What is used to connect a drive shaft segment to another component?
A: Thomas couplings are used at every drive shaft connection to provide a strong yet flexible connection requiring no lubrication.
Q: Why are the indexing flats in Thomas couplings alternated?
A: Alternating indexing flats increases the tensile strength on these flexible couplings.
Q: What is used to prevent slipping when the last tail rotor drive shaft segment is attached to the tail rotor gearbox?
A: A splined adapter is used to prevent slipping.
Q: Why are breather type filler caps used on the tail rotor gearbox?
A: Breather type filler caps are used to prevent “pooling and cavitation”.
Q: What caution light illuminates when ferrous metal particles complete the circuit on the tail rotor gearbox chip detector?
A: The T/R CHIP caution light illuminates when ferrous metal particles complete the circuit on the tail rotor gearbox chip detector.
TH-67 Electrical Systems
ELO #1
Q: What is the rating of the SLAB battery?
A: The SLAB battery voltage is 24 VDC 17 amps
Q: Where is the battery switch (BATT/OFF) located?
A: The battery switch is located on the overhead console.
Q: What recharges the battery?
A: The generator recharges the battery in flight.
Q: Can the batteries level of charge be checked during flight?
A: Yes, the generator must be on as the battery switch is turned off. The drop observed on the load meter indicates how much of the generator’s load was devoted to recharging the battery.
Q: What indicates a fully charged battery?
A: A drop of less than 1 percent indicates a fully charged battery.
Q: What measuring gauge is used to measure 1 percent?
A: The thickness of a secondary line is the measuring gauge for 1 percent.
ELO #2
Q: What does the starter component of the starter/generator do during the starting sequence?
A: The starter component turns the N1 gear train to drive the accessories necessary for basic engine operation.
Q: What does the generator component of the starter generator do after the engine is running?
A: The generator provides 18 VDC to the aircraft’s electrical circuits, plus it maintains charge of the main battery that is in the nose of the helicopter.
Q: How many buss bars are there in the VFR and A+ configuration?
A: There is one main muss bar in the VFR and A+ configuration.
Q: What is the purpose of a buss bar?
A; A buss bar distributes electrical power?
Q: What is the starter/generator rated at?
A: The starter/generator is rated at 28 VDC and 105 amperes
Q: What are the power sources for starting the VFR and A+ configured aircraft?
A: The battery in the nose of the aircraft and the auxiliary power unit.
Q: During normal operations, what are the power sources for the VFR and A+ configuration?
A: The generator is the primary source with the battery as a backup power source.
Q: How long will the battery power the electrical systems after the generator has failed?
A: There are too many variables to predict battery life in terms of time after generator failure.
ELO #3
Q: How many direct current power sources are available for normal operations in the IFR configuration?
A: There are three DC power sources (main gen, stand-by gen, and main battery) available for normal operations in the IFR configuration.
Q: What is the rating of the main generator?
A: The main generator is rated at 28 VDC direct current and 105 amperes.
Q: What is the rating of the stand-by generator?
A: The stand-by generator is rated at 28 VDC and 15 amperes.
Q: What is the rating of the main battery in the nose of the helicopter?
A: The main battery is rated at 24 VDC and 17 amperes.
Q: What does the Voltage Monitoring System allow the pilot to monitor?
A: The Voltage Monitoring System allows the pilot to monitor generators, batteries, and buss bars voltage.
Q: What does an inverter do?
A: An inverter converts DC voltage to 115 volts alternating current (AC) to run two elements of the avionics package.
Q: What is the rating of the stand-by battery?
A: The stand-by battery is rated at 24 VDC.
Q: How many buss bars are there in the IFR configuration?
A: There are three buss bars (ESS 1, ESS 2, and NON-ESS) in the IFR configuration.
Q: Which buss bar is the most protected?
A: The pilot’s buss bar (ESS 1) is the most protected buss bar.
Q: Following the main generator’s failure (MAIN GEN FAIL) what powers the ESS 2 buss bar?
A: The main battery powers the ESS 2 buss bar in the event of the main generator’s failure.
Q: Following a main gen failure (MAIN GEN FAIL) what powers the NON ESS buss bar?
A: The main battery powers the NON ESS buss bar provided the NON ESS switch is placed in the MANUAL position; otherwise the NON ESS circuits are shed from the battery’s load.
Q: In the IFR configuration, how many power sources are there for starting?
A: There are two power sources (main battery and auxiliary power unit) for starting.
Q: In the event of a dual generator failure (MAIN GEN FAIL and STBY GEN FAIL) and main battery power becomes depleted, what powers the stand-by attitude indicator?
A: The stand-by battery powers the stand-by attitude indicator for at least 30 minutes.
Q: What airspeed should be avoided when the stand-by generator is powering the ESS 1 buss bar?
A: Airspeed below 50 KIAS should be avoided to prolonged operation when the stand-by generator is providing power to the ESS 1 buss bar.
TH-67 FUEL SYSTEM
ELO #1
Q: How many layers are there in the TH-67 fuel cell?
A: The TH-67 fuel cell is a single layer, crashworthy, bladder based on civilian aviation standards.
Q: What is the fuel cell capacity and how much of that capacity is consumable?
A: The fuel cell capacity is 84.1 U.S. gallons of which 82.6 gallons are consumable.
Q: What is the burn rate of the Allison C20J turbine engine?
A: The burn rate is 20-29 gallons per hour.
ELO #2
Q: How many boost pumps are there in the TH-67?
A: There are two electric fuel boost pumps located in the bottom of the fuel cell.
Q: How many fuel quantity-sending units are there in the fuel cell?
A: There are two fuel quantity-sending units that transmit fuel quantity to an 80-gallon fuel gauge.
Q: What caution light illuminates with approximately 12 gallons of fuel remaining?
A: FUEL LOW is the caution light that illuminates with approximately 12 gallons remaining.
Q: What is the purpose of the fuel sump drain valve?
A: The drain valve provides for taking of a fuel sample or de-fueling the fuel cell.
ELO #3
Q: Where is the fuel pressure transducer located and what does it do?
A: It is located on the right side of the aircraft above the fuel filler cap. It converts a pressure head signal of the two-boost pumps pressure and sends it to the fuel pressure gauge.
Q: Where is the fuel shut-off valve located and what does it do?
A: It is located at the extreme top-right portion of the fuel cell and above the fuel filler cap. It stops the flow of fuel when the FUEL VALVE ON/OFF switch is turned off.
Q: Where is the airframe fuel filter located and what does it advise the pilot of?
A: It is located on the right side of the engine compartment on the forward firewall. It advises the pilot of an “impending” airframe fuel filter bypass and that the fuel will continue to be delivered to the engine driven fuel pump.
ELO #4
Q: How is the fuel sump drain valve operated?
A: It is electrically operated.
Q: Where is the fuel sump drain valve located?
A: It is located forward of the aft cross tube and centered laterally.
Q: The fuel valve switch must be in which position for the fuel drain valve to operate?
A: The fuel switch must be in the OFF position for the fuel drain switch to operate.
Q: When taking a fuel sample from the fuel cell, the fuel boost pump circuit breakers should be in which position?
A: The fuel boost pump circuit breakers should be OUT to prevent sediment and water from circulating through the fuel system.
Q: Where will sediment and water be found in the fuel sample jar?
A: Should there be any water or contaminates in the fuel sample they will be located in the bottom of the fuel sample jar.
ELO #5
Q: Where is the fuel flow transducer located on the aircraft?
A: The fuel flow transducer is located on the right side of the engine compartment near the aft firewall.
Q: When is the fuel low warning indicating system activated?
A: The fuel low warning system is activated when 45 minutes of fuel remains at the present consumption rate.
Q: The A/F/ FUEL FILTER caution light illuminates at ______PSID and bypasses the filter at ______PSID.
A: 1, 4.5
Q: How many times is the fuel filtered before it is ignited?
A: Fuel is filtered four times (A/F fuel filter, engine driven fuel pump, gas producer fuel control, and fuel nozzle) before it is ignited.