February 2008
UH-60A Auxiliary
4742-3
PROPONENT FOR THIS STUDENT HANDOUT IS:
110TH AVIATION BRIGADE
ATTN: ATZQ-ATB-AD-C
Fort Rucker, Alabama 36362-5000
FD5: This product/publication has been reviewed by the product developers in coordination with the
USAAWC, Foreign Disclosure Officer, Fort Rucker, AL foreign disclosure authority. This product is releasable to students from all requesting foreign countries without restrictions.
D-3

Action: Describe the operational procedures of the UH-60 Auxiliary Equipment.
Condition: Without reference, given the aircraft systems examination and an answer sheet.
Standard: Be able to describe the operational characteristics that pertain to the UH-60 Auxiliary
Equipment. This includes the operational characteristics of the APU, the Heating/ Ventilation System, Fire
Warning/ Detection System, the Fire Fighting System, the Windshield Wiper System, the Windshield Anti-
Ice System, the Cargo Hook, and Pitot Static System.
Safety Requirements: Use care when operating training aids and/or devices.
Risk Assessment Level: Low
Environmental Considerations: It is the responsibility of all soldiers and DA civilians to protect the environment from damage.
Evaluation: You must answer (4) out of (6) questions correctly on in this scorable unit on the systems examination to receive a "GO".
Learning Step/Activity 1.
Describe the operational characteristics of the Auxiliary Power Unit (APU). a. The APU is located on the top of the transition section aft of the #1 engine. Latched fairings provide access to the APU compartment for pre/post-flight inspection and maintenance. The auxiliary power unit
(APU) consists of a gas turbine shaft power section, a reduction gear drive, and appropriate controls and accessories.
(1) The accessory gear drive provides 12,000 rpm output drive for the APU AC generator, and installed components.
(2) The APU consumes approximately 120 pounds of fuel per hour from the #1 main fuel cell. JP4,
JP5, JP8, and commercial jet fuels may be used.
(3) The APU oil system is self-contained and uses MIL-L-23699 or MIL-L-7808 oils. Capacity is 3 US quarts. The APU oil level is checked by using a dipstick.
(4) Check oil level and IPS, if installed, in accordance with the Operator’s Manual.
NOTE: Two versions of the APU are currently in use. One model manufactured by Turbomach has a short dipstick located on the side of the APU oil sump and safety chained to the APU. The Turbomach is currently being modified with a tall dipstick. Most, if not all, have been modified with the long dipstick. The second model, manufactured by Garrett has a top accessible APU dipstick with no safety chain. Another difference is that the Turbomach also has a start/bypass valve, which the Garrett does not. b. The APU provides four functions for the UH-60A; Two pneumatic and two electrical:
(1) Pneumatic power for:
(a) Engine starting
(b) Cabin\ cockpit heating
(c) Once the APU is started and online, it provides the air source for cabin\ cockpit heating and the pneumatic start system for the engines. The APU provides sufficient pneumatic air, enabling the pilot to perform engine starting.
D-4

(2) Electrical power for:
(a) Ground operations
(b) Emergency in-flight operations c. APU system accessories include:
(1) Hydraulic Start Motor. The hydraulic start motor is located on the APU accessory gearbox. The
APU start motor, controlled by the ESU, is hydraulically driven and drops out when the APU reaches 70% speed during the start sequence. After the APU reaches 70% speed, the start motor becomes a free wheeling unit. The hydraulic fluid used to drive the start motor, enters from the accumulator through the pressure line, and returns to the accumulator through the return line. The APU start motor is mounted to the accessory drive and motors the compressor assembly during the start sequence.
(2) APU Generator. Electrical power for ground operations and in-flight emergencies is provided by the APU generator. An AC generator, located on the APU, provides the helicopter with 115-volts alternating current (V ac), three phase, 400-hertz electrical power. The accessory gear drive provides
12,000 rpm output drive for the APU AC generator, and installed components.
D-5

(3) APU oil dipsticks. The APU oil system is self-contained and the capacity is 3 US quarts. The APU oil level is checked using a dipstick. When the APU is cool to the touch, the COLD side of the dipstick may be used. If the APU is hot to the touch, the HOT side of the dipstick may be used.
(4) APU intake. During preflight, ensure inlet screen is free of foreign objects and debris that would restrict air flow. Dispose of properly. d. APU controls.
(1) APU control switch. The APU CONTR is a two position switch. Placing the switch in the ON position initiates an automatic starting sequence without intervention from the pilot. If there is a malfunction of the automatic starting sequence, the ESU will stop APU operation and activate the APU
FAIL caution. If the APU fails, note and analyze BITE indications before cycling the BATT switch or before attempting another APU start.
Remark; Cycling the APU control switch, T-handle, or the battery switch will remove and reapply battery bus power to the ESU. Doing so may cause a start sequence to initiate with residue of combustible fuel and turbine rotation (14% Ng or more) are present. An over-temperature or over- speed condition may result.
(2) The FUEL PUMP switch is a three position (APU BOOST/OFF/FUEL PRIME) switch. The prime/boost pump provides 5 psi pressurized fuel to the APU from the No. 1 fuel cell. IAW the -10/CL, the
FUEL PUMP switch must be at APU BOOST for all APU operations. The APU prime/boost shutoff valve is a two-position, open-closed unit mounted on the APU compartment firewall where it also functions as a firewall shutoff valve. The valve is operated by the FUEL PUMP switch as well as the APU T-handle.
(3) The APU fire T-handle warns the pilot/copilot of a potential fire in the APU compartment. When the T-handle is pulled three things occur:
(a) Fuel to the APU is shut off.
(b) A stop signal is sent to the ESU.
(c) The fire extinguisher system arms, and the directional control valve is set to the APU position.
D-6

WARNING: In case of fire when ac electrical power is not applied to the helicopter, the reserve fire extinguisher must be discharged. Fire extinguisher agent cannot be discharged into No. 2 engine compartment if ac electrical power is not applied to helicopter.
NOTE: During APU starts using battery power, if the fire extinguisher is required, FIRE EXT RESERVE must be used. The T-handle micro-switch, directional control valve, and the reserve fire bottle discharge circuit are powered by the battery utility bus e. Caution/Advisory lights
(1) APU Fail- The APU fail caution light will be on any time the APU automatically shuts down. Check the BITE indications. When checking the fault code with the -10, the start sequence is prior to having the
APU ON advisory. The run sequence is after.
(2) The APU Electronic Sequence Unit (ESU) activates the APU ON advisory capsule, indicating the
APU is operating. The APU advisory light comes on in the cockpit at 90% speed + 1.5 seconds.
(3) An APU GEN ON advisory will appear when the APU generator is the sole source of AC power and the APU generator is operating with the APU GEN switch ON. The APU GEN ON advisory will not appear when either the No.1 Generator or the No. 2 Generator is supplying AC power. The APU generator must be the sole source of power.
(4) The PRIME BOOST PUMP ON advisory appears when the FUEL PUMP switch is in the APU
BOOST, FUEL PRIME position and when the ENG START switch is actuated. (auto prime)
(5) The APU ACCUM LOW advisory light appears when a pressure switch for the accumulator causes the advisory to appear at 2600 psi.
(6) The APU OIL TEMP HI caution appears when APU oil temperature is above the normal range.
During ground operation at high ambient temperatures the APU OIL TEMP HI caution may appear. If this occurs, the APU should be shut down immediately to prevent damage. After a 30-minute cooling period, the oil level should be checked. If okay, the APU may be restarted. This caution will not cause the ESU to automatically shut down the APU. f. The Electronic Sequence Unit (ESU)
(1) The APU system operation is completely automatic and controlled by the ESU. The ESU provides automatic starting and continuous operational monitoring. During start and operation, an Electronic
Sequence Unit (ESU), located in the main cabin ceiling, forward of the stabilator amplifiers, compares input signals from speed, time, and temperature sensors of the APU to specific values in the ESU memory, and performs functional steps as a result of the comparison. The system also provides for protective shutdown in case of turbine overspeed, underspeed, high exhaust temperature, low oil pressure, or loss of electrical power or sequence failure. The BITE indications of the ESU shall be used to troubleshoot APU malfunctions. If the APU fails, enter the BITE indication as a fault on the 2408-13-1 for maintenance action.
NOTE: If APU fails, note and analyze BITE indications before cycling BATT switch or before attempting another APU start
D-7

Note: The top yellow line is pointing to the BITE indications. g. Battery Bus
(1) Power to operate the APU and ESU is provided from the battery bus. h. APU Start/ Hydraulic System
(1) The APU start system, which is a part of the hydraulic system that was taught the hydraulic class, has an accumulator and start motor that are used to start the APU. The Backup hydraulic pump is used to charge the accumulator by forcing pressurized hydraulic fluid to the APU start motor.
(2) The accumulator is located above the fuel cells in the aft cabin ceiling, while the start motor is attached to the accessory drive assembly on the APU.
(3) The APU start system can be broken down into seven major components: APU hand pump, accumulator pressure gage, accumulator pressure switch, APU start valve, accumulator tape indicator, start motor, and APU accumulator.
(a) APU hydraulic hand pump. A bi-directional and allows manual recharging of the accumulator when the APU fails to start or the accumulator pressure is low and an AC power source is not available.
(b) APU accumulator pressure gage. It indicates the nitrogen pressure inside the accumulator.
The nitrogen precharge in the accumulator at 70 ºC is 1450 psi. Hydraulic fluid inside the accumulator compresses the nitrogen precharge. The pressure gage will indicate how much pressure the hydraulic charge has placed on the nitrogen precharge. The acceptable minimum pressure before starting the APU is 2800 psi. When the hydraulic charge has been released during the APU start sequence, the pressure gage will indicate the change in pressure to the nitrogen precharge. When the hydraulic fluid has been recharged, either by the Backup pump or Hand pump, the nitrogen gage should return to the indication prior to the beginning of the start sequence. The accumulator nitrogen precharge is serviced at the nitrogen servicing valve on the pressure gage.
D-8

(c) Accumulator Pressure Switch. The pressure switch for the accumulator causes the APU
ACCUM LOW advisory to appear when the nitrogen precharge is low and activates the backup hydraulic system pump to develop pressure.
(d) The APU start valve. Controlled by the ESU, releases the accumulator hydraulic charge to the
APU start motor during the APU start sequence. The manual release lever is located on the APU start valve. If the APU does not start and the APU ACCUM LOW advisory does not appear with the APU
CONTR switch ON, the manual override lever on the accumulator manifold should be pulled to attempt another start, and held until the APU has reached self-sustaining speed.(e) The accumulator tape indicator, on the APU accumulator, displays the percent of pressure charge in the accumulator. The tape will indicate zero (0) when the hydraulic charge has been released. This is a maintenance function to test the system.
(f) Accumulator Operation. In the APU accumulator there are multiple chambers. Chamber A contains the nitrogen precharge. Chamber B and C contain Hydraulic Fluid. Chamber D is vented to the atmosphere allowing piston travel space. With battery power applied, the FUEL PUMP SWITCH to APU
BOOST and the APU CONT switch in the ON position, the start valve opens to allow fluid to rotate the starter and high pressure fluid is transferred from chamber B to chamber C thus moving the piston. The pressure switch activates the APU ACCUM LOW advisory and arms the BACK-UP Hydraulic Pump.
When the APU reaches self sustaining speed the ESU activates the APU ON advisory. When the APU
GEN switch is moved to the ON position, the APU GENERATOR will supply AC power to the BACK-UP
Hydraulic pump and initiate the recharging of the APU Accumulator. The rate of accumulator recharge is limited to 1.5 gallons per minute (gpm) through a velocity fuse in the utility module. This process will take
90 seconds with a single accumulator and 180 seconds with the winterized (dual) accumulator. In the absence of AC power, the accumulator can be recharged with the hand pump.
D-9

(g) Winterization Kit. Aircraft equipped with the winterization kit have a second APU accumulator installed in parallel to the original. Both accumulators are charged or discharged simultaneously. If the accumulators do not fully charge during the first 180 seconds of the backup pump operating cycle, the pump will continue to operate in 180-second segments, or until the BACKUP PUMP PWR circuit breaker is pulled, or 115 V ac power is removed.
Note: Review the APU start procedures from the operator’s manual and/or checklist. Review the emergency procedure from the operator’s manual and/or checklist
D-10

E S U
3 2
A P U
Three switch sequence to start APU
Battery only source of DC power
1 Battery switch ON. Battery connected.
2 APU T-handle IN.
3 APU Control switch ON.
Cycling the APU control switch, T-handle, or the battery switch will remove & reapply battery bus power to the ESU. Doing so may cause a start sequence to initiate while residual combustable fuel and turbine rotation
(44% Ng) are present. An over-temperature or over-speed condition may result.
BATTERY
BUS K7
1 on
1
BATTERY
UTILITY
BUS
#1 ENG. FIRE EXT. ARM
APU FIRE EXT. ARM
MAP LIGHTS
MAINT. LIGHT batt. sw.
28V DC for batt. chrg. & BUB energize
(from #1 A/C or D/C PRI. as determined by charger analyzer logic)
28V DC (from batt.) for C/A logic circuits sense info: temp. & state of charge
C/A to batt. & BUB or batt. to BB & DC ESS
(i/a/w K-7 position)
CHARGER
ANALYZER
28V
D/C BATTERY
SENCE INFO.
(ANALYZER LOGIC CIRCUITS CONSUME BATT. PWR. THROUGH SENSE CONNECTION,
DISCONNECT CANNON PLUG AT END OF MISSION DAY TO AVOID BATTERY DRAIN)
D-11 ver 1.1
10/97

Learning Step/Activity 2 . Describe the operational characteristics of the Heating/Ventilating System. a.The heating subsystem components.
(1) Heated air source (bleed-air).
(a) On the ground, the operating APU, main engines or an external source may be used.
(b) The heating system uses bleed-air as its heat source. Bleed-air is supplied in flight by the main engines and on the ground by either the main engines or the APU. An external connector allows connection of an external ground source into the pneumatic system that can provide heat when connected. The ventilation system consists of the VENT BLOWER and uses the same ducting and registers.
(2) Heating Controls
NOTE: Operation of the heater will reduce the maximum torque available by 4% or 5.5%, depending on the heater, with the ENG selected as the pneumatic source. The AIR SOURCE HEAT/START switch must be set to the pneumatic source ENG to use bleed air from the engines. When turning the vent blower or heater systems on protect your eyes. Sand and dust particles may accumulate in the ducts and will be forced out into the cockpit.
(a) The HEATER manual control knob is interconnected through the upper console panel through a right angle drive to the HEATER CONTROL SHAFT, which connects to the MIXTURE TEMPERATURE
SENSOR. The control knob allows the pilot and copilot to adjust the MIXER TEMPERATURE SENSOR downstream of the mixing valve to control cabin temperature. Turning the knob from OFF to MED or HI regulates the temperature of heated air entering the cabin by allowing more bleed-air to pass through the mixing valve into the cabin heat ducting. A TWO POSITION TOGGLE SWITCH labeled ON and OFF, controls dc power through a thermal protection switch, to the bleed-air on/off solenoid on the mixing valve assembly. The thermal protection switch de-energizes the bleed-air on/off solenoid if mixed air
D-12

temperature is over 90° to 96°C (194° to 205°F). Should the HEATER control switch be turned OFF or dc power fail, bleed-air will shut off.
(3) Heating and Ventilation System Components
(a) Vent Blower Motor. The VENT BLOWER switch marked OFF and ON is located on the upper console. Placing the switch to the ON position, 28 V dc from the No. 2 dc primary bus is routed through the circuit breaker marked HEAT VENT, and the VENT BLOWER switch, and through a thermal protection switch which prevents the vent blower from overheating. 115 V ac is supplied by the No. 2 ac primary bus, through the HEAT & VENT circuit breaker to the vent blower motor and the blower motor pulls in outside air through the external air intake and circulates it through the cabin heat ducting.
(b) Mixing Valve Assembly. The MIXING VALVE ASSEMBLY working with the MIXTURE
TEMPERATURE SENSOR, mixes hot bleed air from the HOT AIR SOURCE with ambient air to achieve the desired temperature selected at the cockpit heating control.
(c) Regulation Valve. Is part of the MIXING VALVE ASSEMBLY, and reduces bleed-air pressure as it comes from the engine/APU to be mixed in the MIXING VALVE ASSEMBLY.
(d) Mixture Temperature Sensor. The MIXTURE TEMPERATURE SENSOR, connected through a heater control shaft, to the heater control knob on the upper console controls, and is located underneath the muffler inside the ducting. The MIXTURE TEMPERATURE SENSOR works along with the MIXING
VALVE ASSEMBLY, regulating the bleed-air flow to match the mixture temperature selected at the cockpit heating control.
(d) Hot Air Source. Is bleed-air supplied by the main engines compressor section (fifth stage axial compressor P-2.5) or the APU during ground operations. On the ground an external source may also be used.
(e) Muffler. Connected between the VENT BLOWER MOTOR, the MIXING VALVE ASSEMBLY and the aircraft heating and ventilation ducting, the MUFFLER guides the air flow from the VENT
BLOWER MOTOR and/or the MIXING VALVE ASSEMBLY to the heating and ventilation ducting.
D-13

(f) Thermal Protection Switch. Activates the shut off valve when the temperature reaches 90 to 96 degrees Celsius and re-opens the valve when temperature decreases.
(4) Heating and Ventilation Ducting
(a) Ducts are located across the top of the aircraft from the APU compartment and engines to forward of the main rotor pylon. Ducting brings the downstream airflow into the cockpit in three (3) locations for each pilot and one (1) location for each crew chief/gunner station (defog vents are also on the leading edge of the gunner windows.)
D-14

AIR SOURCES (4)
APU
#1 Engine
#2 Engine
External (GPU or other UH-60)
USE OF BLEED AIR
#1/#2 Engine start (single or dual engine start)
Cockpit heat
Pressurization of external fuel tanks
Engine & Engine inlet anti-ice
Export to other helicopter (via buddy hose)
Extended
Range
Fuel
System
VENT BLOWER
AMBIENT
AIR
HEATER
SHUTOFF
VALVE
(solinoid)
START RELAY
(disables heat during start)
P-2.5 or APU or EXTERNAL
HEATER MIXING VALVE
COCKPIT
CONTROL
INPUT
DC PRI BUS
O
F
F
HEATER
MED
ON
OFF
4% loss of MTA when heater is active. (If only one engine is operating, a 4% loss of
MTA will be realized on that engine. With two engines operating the loss is shared between the two engines.)
HI
Extended
Range
Fuel
System
Use of bleed air to pressurize external tanks is not significant enough to consider loss of MTA.
1 AISBV can be opened/closed by pilot for A/I function.
ver 1.0
9/97
2 AISBV can be opened/closed by HMU for compressor bleed function.
#2 ENG INLET
ANTI-ICE ON
AMBIENT
AIR SENSOR
PORT
3 When switch is in ENG. position, crossbleed valves are armed
& will open if P-2.5 is present. With switch off, both valves close.
#2 A/I valve is passing
P-2.5 to inlet assy.
TS CONTROL
INLET A/I
VALVE
AGB
#2 ENGINE
STARTER
4 When switch is in APU position, apu start/bypass valve (turbomach apu only) closes when either start button is pressed (a start relay function). With switch OFF, valve remains open and vents a large portion of apu air overboard. To remove 100% of apu bleed air from the pneumatic manifold system the apu must be shut down.
(Garrett type APU's don't have a start/bypass valve) gill slits fuel
P-3
PTO burn cool
Ng Np
P-2.5
Np
P-3
1 2
AISBV #2 ENG
ANTI-ICE ON
#2 AISBV is open
Nr
AIR SOURCE
HEAT / START
ENG
O
F
F
APU
3 solinoid
#2 START
RELAY
(K-26)
#1 START
RELAY
(K-45)
#2 ENGINE
STARTER
#2 start valve open, all #2 start relay functions are active.
During crossbleed start, an 18% loss of MTA will be realized on the air source engine. Not cumalative with heater & A/I because they're deactivated during engine start (a start relay function).
solinoid
4
AGB
PTO
P-3 fuel burn cool
Ng
#1 ENGINE
STARTER
APU START/BYPASS VALVE
(Turbomach APU only)
(see note #4)
Np P-2.5
Np
P-3 gill slits
TS
#1 ENG INLET
ANTI-ICE ON
Temp. Switch (thermistor) illuminates light when inlet is receiving P-2.5 (hot air).
AMBIENT
AIR SENSOR
PORT
1 2
AISBV
INLET A/I
VALVE
CONTROL
START RELAY
(disables inlet
A/Iduring start) allows inlet A/I valve to open (removes ele. pwr.)
ENGINE ANTI-ICE
#1
O
F
F
ON opens AISBV
(removes ele. pwr.)
A 16% loss of MTA is realized when engine
& engine inlet A/I is activated (loss is realized only on the engine being anti-iced, there is no exchange of bleed air between engines for anti-ice purposes)
#1 ENG
ANTI-ICE ON
#1 AISBV is open
INLET A/I VALVE CONTROL
When A/I switch is on, valve opens/closes IAW ambient temp:
4 deg. C or colder valve should open, 13 deg C or warmer valve should close, between 4-13 deg. C valve may be open or closed.
(protects fiberglass inlet from heat damage)
CHECK
VALVE
EXTERNAL
PNEUMATIC
PORT
Allows import of air from an external air source (GPU or other helicopter).
Allows export of air to another helicopter (buddy hose opens check valve when inserted)
D-15

Learning Step/Activity 3.
Describe the operational characteristics of the Fire Warning/Detection System. a. Fire Detection System Components
(1) The detection system provides fire warning to the cockpit, in case of fire in either main engine compartment or in the Auxiliary Power Unit (APU) compartment. The system consists of five radiationsensing, solid-state photoconductive fire detectors, control amplifiers, and a test panel. Two detectors are installed in each main engine compartment and one detector is in the APU compartment, providing continuous volume optical surveillance of the monitored areas.
(a) Fire Detectors. The system consists of five radiation-sensing flame detectors. Two detectors are installed in each main engine compartment and one detector is in the APU compartment. The flame detectors are solid-state photoconductive cells providing continuous volume optical surveillance of the monitored areas. In case of fire, the detectors react to the infrared radiation and send a signal to the fire warning assembly lighting the proper T-handle. Also, the master FIRE warnings will appear if a fire is detected. The detector system automatically resets itself, with warnings disappearing, when the infrared radiation source ceases to emit.
(b) Battery Bus. The battery and battery utility bus is located on the center lower console, left side and aft. The BATT BUS provides power to the APU CONTR INST and APU FIRE DET circuit breakers and the BATT UTIL BUS provide power to the FIRE EXTGH and APU CONTR INST circuit breakers.
(c) Fire Warning Capsule. The Master Warning Panel is attached to the bottom side of the glare shield, directly in front of the copilot seat. The master FIRE warning capsule will illuminate if a fire is detected. The detector system automatically resets itself, with warning lights off, when the infrared radiation source ceases to emit.
D-16

(d) Engine Control Quadrant/T-Handles. The engine control quadrant contains two T-handles, one for the No. 1 engine and one for the No. 2 engine. Each containing two lamps for illumination and labeled #1 ENG EMER OFF and #2 ENG EMER OFF. When a handle is pulled, dc power actuates the fire extinguisher logic module to select the compartment to which the fire extinguisher agent is to be directed, and also energizes the circuit to the fire extinguisher switch.
(e) Fire Detection Test Switch and DC Essential Bus. The FIRE DETR TEST switch is a three position system test switch, located in the upper console, and used to test the fire warning indicating system circuits. Two circuit breakers supplying power to the test switch, labeled OPER, 1 and 2, are located on the DC ESNTL BUS.
(f) APU T-Handle. The APU T-handle is on the upper console, labeled APU. When the handle is pulled, dc power is routed to the fire extinguisher logic module, which selects the compartment to which the fire extinguisher agent is to be directed, and also energizes the circuit to the fire extinguisher switch.
The handle also houses two lamps, used as fire detector warning lights.
D-17

Learning Step/Activity 4.
Describe the operational characteristics of the Fire Fighting System. a. The fire extinguishing system is a high-rate discharge extinguishing system that provides a two-shot, main and reserve capability to either main engine compartment or APU compartment.
(1) Fire Extinguisher Bottles. Each bottle is filled with 2.5 pounds of fire extinguishing agent, pressurized with gaseous nitrogen, and has a pressure gage for verification of charge. Both bottles have dual outlets, each outlet with its own firing mechanism and one thermal discharge valve per bottle. Each bottle serves as a backup for the other, thereby providing a two shot capability to extinguish fires in either main engine compartment or APU compartment.
(2) APU. The APU compartment has one discharge nozzle to extinguish an APU fire.
(3) APU Fuel Shutoff Valve. The APU fuel shutoff valve controls the flow of fuel to the APU and is located in the transition deck above No. 1 fuel cell.
(4) Directional Control Valve. Activated by the APU T-handle and directs the agent to the APU compartment. The valve is spring loaded to the No. 1 engine compartment position. "T" style check valves are used to prevent the extinguishing agent from flowing into the other bottle once the agent is fired.
Pulling the T-handle tells the logic module which path to use for routing the voltage to the bottle. Select
MAIN on the FIRE EXTGH switch to activate main fire bottles. If the fire is not extinguished, putting the switch into the RESERVE position fires the remaining bottle.
(5) Inertia Impact Switch. Upon impact or a crash of 10 Gs or more, an omni directional inertia impact switch (S1), mounted in the left hand relay panel, automatically fires both explosive cartridges (squibs) attached to the containers, releasing fire extinguishing agent into both main engine compartments.
D-18

(6) T-Handles. When a handle is pulled, V dc power is routed to the fire extinguisher logic module to select the compartment to which the fire extinguisher agent is to be directed, and also energizes the circuit to the fire extinguisher switch. The handles house fire detector warning lights.
(7) Fire Extinguisher Switch. Located on the upper console, has marked positions of
RESERVE/OFF/MAIN. The switch is operative only after one of the two ENG EMER OFF or the APU Thandle has been pulled. When the switch is placed to MAIN, after a T-handle has been pulled, the contents of the main fire extinguisher bottle are discharged into the corresponding compartment. When the FIRE EXTGH switch is placed to RESERVE, after a T-handle has been pulled, the contents of the reserve fire extinguisher bottle are discharged into the selected compartment. The contents of the fire extinguisher bottle discharge into the compartment of the last lever pulled.
WARNING: In case of fire, when ac electrical power is not applied to the helicopter, the reserve fire extinguisher must be discharged. Fire extinguisher agent cannot be discharged into No. 2 engine compartment if ac electrical power is not applied to helicopter.
(8) Tubing/Discharge Nozzles. Each Engine compartment possesses two discharge nozzles for fire fighting. One is located inboard on the firewall directed just forward of the combustion section. The other is positioned outboard of the engine at the 10 and 2 O'clock position, respectively, to direct agent in the vicinity of the engine Inlet.
(9) Fire Extinguisher Discharge Indicator. A single, overboard discharge line is connected to both pressurized fire extinguisher agent containers. A red indicator disc is at the end of the line, on the right side of the helicopter fuselage, at station 464. A broken out or missing red disc indicates that one or both container's thermal relief valve has discharged. b. Fire. If an engine or APU compartment fire occurred, the appropriate T-handle would illuminate. Pulling the T-handle tells the logic module which path to use for routing the voltage to the appropriate bottle.
Select MAIN on the FIRE EXTGH switch to activate main fire bottles.
D-19

ARM #2 Engine:
Pin 10 to 5
Pin 12 to 7
ARM #1 Engine:
Pin 9 to 4
Pin 11 to 6
ARM APU:
Pin 3 to 8
Pin 9 to 4
Pin 11to 6
1
3
2
10 G Impact Switch
5
(closes if impact force exceeds 10 G's)
4
Fire Ext. Logic Module
(last command recieved is only one armed, fight multiple fires one at a time)
7
6
8 attery tility us
FIRE
5
EXTGH
Pressure Gage
(1 per bottle)
(see chart)
13
Thermal Discharge
Port (LRD)
11 10 12 9 ver 1.1
5/02
O F
TEMP - PRESSURE RANGE
O - 40 -20 0 +20 +40
292 320
O O O
355 396 449
O
PSIG
O F
PSIG
370 400 437 486 540
O
+60 +70 +80 +100 +120
O
518 555 593 670 775
618 660 702 748 885
R M
FIRE
B attery
U tility
B us
5
EXTGH
MAIN RESERVE
OFF
Fire Extinguisher Switch
FIRE
#2 DC
Primary
BUS
5
EXTGH
BUB
#2 DCP
(BUB for 10G)
Thermal Relief
#2 Engine
Explosive Cartrage
(SQUIB)
(2 per bottle)
#2 ENGINE "T-handle"
When pulled aft:
Rakes off fuel selector (engine flames out) & arms fire fighting system (using #2 DC Primary power)
B attery
U tility
B us
FIRE
5
BUB
APU
EXTGH APU "T-handle"
When pulled:
Shuts down APU, repositions DCV to APU,
& arms fire fighting system (using BUB power).
BUB
#1 Engine Directional Control Valve (DCV):
Powered by BUB. Default to #1 engine.
ELECTRICAL SYSTEM CONDITIONS:
When APU T-handle is pulled, directs
CF3BR to APU.
1.
#2 DC Primary & BUB "hot": Unlimited fire fighting capability (any bottle to any engine).
2.
#2 DC Primary "cold", BUB "hot": Reserve bottle to #1 engine or APU. (#2 engine fire fighting lost ).
3.
#2 DC Primary "hot", BUB "cold": Reserve bottle to #2 engine (#1 & APU fire fighting capability lost ).
ABOVE CONDITIONS MAY BE CAUSED BY THE FOLLOWING:
When only APU is operating, pulling APU T-handle will shut down APU, APU generator then drops off line, all AC busses, & #1/#2 DC primary busses are now cold, battery keeps BUB hot (condition #2).
FIRE
#2 DC
Primary
BUS
5
EXTGH
FIRE
B attery
U tility 5
#1 ENGINE "T-handle"
When pulled aft:
B us
EXTGH
Rakes off fuel selector (engine flames out) & arms fire fighting system (using BUB power).
#2 DCP
(BUB for 10G)
When in normal flight mode, drooping Main Rotor to 85-89% will cause both main generators to drop off line, until RPMR is recovered, all AC busses, & #1/#2 DC primary busses are now cold, battery keeps BUB hot (condition #2).
If APU (or APU generator) is inoperative during shutdown, moving the PCL's to idle will cause the loss of all ac power
(@95% rpmr) all AC busses, & #1/#2 DC primary busses are now cold, battery keeps BUB hot (condition #2).
If #2 DC Primary buss is shorted out (#2 converter inop with current limiter blown), or during a dual converter failure, the #2 DC primary buss will be cold, battery keeps BUB hot (condition #2).
If battery is disconected while helicopter is running (rpmr above 95%) BUB will be "HOT" by Charger Analyzer,
If battery switch is cycled during this condition the Charger Analyzer will drop off line and "BUB" will be cold (condition #3).
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Learning Step/Activity 5 . Describe the operational characteristics of the Windshield Wiper System. a. Windshield Wiper System. The electrically-operated windshield wiper system consists of a two-speed
AC motor, two converters, two wipers, and a control switch. Power for the wiper system is supplied by the
No. 1 primary AC bus through the WSHLD WIPER circuit breaker on the copilot circuit breaker panel.
CAUTION: At airspeeds greater than 120 KIAS or during periods of reduced rain intensity the windshield wipers may slow noticeably. If this occurs, wipers must be parked immediately to avoid wiper motor failure.
(1) Wiper Blade Assembly. The Wiper Blade assembly consists of a rubber blade, a link, and an arm.
The link is adjustable in order to facilitate alignment of the blade parallel to the center windshield.
(2) Mechanical Drive Mechanism.
(a) Wiper Motor A 115 V ac motor powered through a 5 amp circuit breaker on the No. 1 AC primary bus circuit breaker panel, drives the wiper blades at the selectable speeds; LOW and HIGH.
Flexible Shaft.
(b) The Flexible Shaft connects the motor to the mechanical converter and routes the drive force.
It is connected by a small coupling at the motor and the converter.
(c) Converter. A mechanical component, which drives the wiper blade assemblies and encloses a slip clutch mechanism that allows for the "Clap hand" motion.
(3) Windshield Wiper Control Switch. Two electrically operated windshield wipers are installed, one on the pilot's windshield and one on the copilot's windshield. Both wiper arms are driven by a common motor through flexible drives and converters. Power to operate the windshield wiper system is from No. 1 ac primary bus through a circuit breaker marked WSHLD WIPER. Control of the windshield wipers is through a spring loaded rotary switch on the upper console. The switch is labeled WINDSHIELD WIPER with marked positions PARK-OFF-LOW-HI.
(a) When the switch is turned from OFF to LOW or HI, the wipers will operate at the corresponding speed. The pilot should select the HI position when starting windshield wiping operations to prevent excessive load on the electrical motor.
(b)If a slower speed is desired for continued operation then the pilot should select LOW. When the switch is turned from OFF to LOW or HI, the wipers will operate at the corresponding speed. If the wipers appear to vary in rate the pilot should cease operation or adjust to the HI position dependant on rain conditions.
(c) The wipers will stop at any position when the switch is turned OFF. When the switch is turned to PARK, the wipers will return to the inboard windshield frame and stop. When the switch is released, it will return to OFF.
CAUTION: To prevent possible damage to windshield surface, do not operate windshield wipers on a dry windshield.
D-21

Learning Step/Activity 6.
Describe the operational characteristics of the Windshield Anti-ice System. a. Windshield Anti-Ice System
(1) Pilot's, co-pilot’s, and center windshields are electrically anti-iced and defogged. Transparent conductors imbedded between the laminations provide heat when electrical power is applied.
CAUTION: Ice removal shall never be done by scraping or chipping. Remove ice by applying heat or deicing fluid. b. Windshield Anti-Ice Switches
CAUTION: Continued use of a faulty windshield anti-ice system may result in structural damage
(delamination and/or cracking) to the windshield. Do not allow ice to accumulate on the windshield, as ice shedding can cause engine foreign object damage (FOD).
(1) Three switches, one for the pilot, one for the copilot, and one for the center windshield (when equipped) are on the upper console with markings of WINDSHIELD ANTI-ICE PILOT-OFF-ON,
COPILOT-OFF-ON and ANTI-ICE CTR -OFF- ON. c. Terminal Blocks
(1) Power to operate the anti-icing system is provided by the No. 1 and No. 2 ac primary buses through circuit breakers marked PILOT WSHLD ANTI-ICE and CTR and CPLT WSHLD ANTI-ICE. If the
APU generator is the sole source of AC generated power, the backup pump and the windshield anti-ice cannot be used simultaneously. The backup pump has priority.
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d. Temperature Sensors
(1) The temperature of each panel is controlled to a heat level of about 43°C (109°F). The windshield anti-ice system fault monitoring circuit prevents windshield burnout when the windshield surface heat is above 43°C (109°F). If heat increases, the monitor circuit will turn off the system. e. Windshield
(1) The windshield is made of laminated glass with attached heating elements. UH-60 aircraft designated 85-24441 and subsequent, and all aircraft modified with MWO 1-1520-237-50-70 include a center windshield heating element. The windshield has electrical terminals for the power input from the controller and two parallel wired temperature sensors.
Learning Step/Activity 7 . Describe the operational characteristics of the Cargo Hook System.
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a. Cargo Hook System
(1) The UH60A cargo hook system consists of an 8000 pound capacity hook and the electrical circuits that control it. The hook is located in the cargo hook well beneath the cabin floor. b. Cargo Hook
CAUTION: Cargo suspended from the cargo hook should not be over a 30° cone angle. To prevent damage to the cargo hook keeper, the pilot shall use extreme care to prevent placing load pressure on the keeper.
(1) The cargo hook is located between stations 343 and 363 on centerline. c. Release Solenoid and Switch Housing
(1) The RELEASE SOLENOID AND SWITCH HOUSING, houses and protects the release solenoid, switches, and associated wiring from the elements. d. Load Beam
(1) The LOAD BEAM supports the weight of the load and pivots open when the load is released. It takes approximately 20 pounds of downward force to release the load arm from the locked position.
When downward pressure is released, load beam will close and latch. e. Release Solenoid and Switch Housing
(1) Manual release of external cargo can be done by the crew chief, or by ground personnel, with the cargo hook system power on or off. Activating the release control on the right side of the hook, causes the latching mechanism to release the load beam. The load beam will not move unless a downward pressure is exerted to cause opening.
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f. Keeper
(1) The spring loaded KEEPER guards against accidental load loss, due to the load slipping off the front of the LOAD BEAM. g. Cargo Hook Stowage
(1) The cargo hook can be placed in a stowed position by opening the cargo hook access door in the cabin floor, and pulling the hook to the right and up. The cargo hook shall be maintained in the stowed position while not in use. When the hook is in the stowed position, the load beam rests on a spring-loaded latch assembly and is prevented from vibrating by a Teflon bumper applying downward pressure on the load beam. To release the hook from its stowed position, downward pressure is placed on the latch assembly lever, retracting the latch from beneath the load beam, allowing the cargo hook to swing into the operating position. h. Electrical
(1) For the normal release, the cargo hook system gets 28 V dc electrical power from the No. 2 dc primary bus through the CARGO HOOK PWR circuit breaker and through the CARGO HOOK CONTR circuit breaker. For the EMER REL, 28 vdc from the DC ESS bus goes through the CARGO Hook EMER circuit breaker.
(2) The No. 1 primary dc bus through LIGHTS ADVSY circuit breaker supplies 28 V dc for the
EMERG REL TEST light circuit. i. Control Stick Switches
NOTE: When the emergency hook release has been used and a replacement squib (explosive cartridge) is not available, the hook cannot be used until the explosive device is replaced, since the hook load beam will not close and lock.
(1) Emergency Release Switch
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(a) Each collective stick grip contains one cargo hook emergency release switch labeled HOOK
EMER REL, which activates an electrically activated explosive charge, producing a high gas pressure to drive a piston in the lock assembly, releasing the load beam lock.
(b)The weight of the load will cause the load arm to open.
(c) Once the emergency release is used, the hook will remain open and the CARGO HOOK
OPEN advisory will appear until the explosive cartridge device is replaced.
(d) The emergency release is used when the electrical and manual releases are inoperative, and the load must be jettisoned.
(2) Normal Release Switch
(a) Both of the cyclic stick grips contain a normal release switch labeled CARGO REL, with guards to prevent accidental cargo release.
(b) Normal release of external cargo is done by pressing the CARGO REL switch on either cyclic stick grip or the NORMAL RLSE on the crew member's pendant.
(c) With the CARGO HOOK ARMING switch to the ARMED position, the HOOK ARMED advisory will appear, and informs the pilot that actuation of any of the release switches will release the load.
(d) When the CARGO REL switch is pressed and the release solenoid begins to move, a switch activates the CARGO HOOK OPEN advisory.
(e) The load beam will swing open, releasing the cargo.
(f) When the sling is detached from the load beam, spring tension on the arm will cause it to close and relatch, and the CARGO HOOK OPEN advisory disappears.
(g) The normal release system cycles; once the solenoid travel begins and the load arm relatches, the release cycle can again be initiated.
D-26

j. Crew Chief Pendant
(1) The CREW CHIEF cargo hook pendant consists of two normally open push-button switches marked NORMAL RLSE and EMER RLSE. The switches control the release of the cargo hook under normal and emergency conditions.
(2) Guards are mounted over each switch to prevent accidental cargo release. The pendant electrically interfaces with the helicopter system through a six foot cable assembly. The pendant can be attached to the crewman by way of a strap assembly. k. Normal Release Mode Check
(1) Refer to the -10 for current operational checks. l. Cargo Hook Emergency Release Circuit Check
NOTE: To prevent unintentional discharge of the cargo hook explosive cartridge, the pilot shall call off each procedural step of the emergency release circuit test before that step is done. Station being checked shall reply to the pilot’s command.
(1) Refer to the -10 for current operation checks. m. Emergency Release Operation
(1) When any of the 3 cargo hook EMER REL switches is actuated, 28 V dc is applied to the explosive cartridge, producing a high gas pressure to drive the piston in the lock assembly, releasing the load arm lock.
(2) The weight of the load will cause the load beam to open.
(3) Once the emergency release is used, the hook will remain open and the CARGO HOOK OPEN advisory capsule will appear until the explosive cartridge is replaced.
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D-28

NOTE: When the emergency hook release has been used and a replacement squib (explosive cartridge) is not available, the hook cannot be used until the explosive device is replace since the hook load beam will not close and lock.
Learning Step/Activity 8.
Describe the operational characteristics of the Pitot-Static System. a. Pitot Heating
(1) Pitot Tube Heater. Power to operate the pitot tube heaters is provided from the No. 2 ac primary bus for the right pitot tube through a circuit breaker marked RT PITOT HEAT, and from the No. 1 ac primary bus for the left pitot tube through a circuit breaker marked LEFT PITOT HEAT.
(2) Pitot Electrical Components. Pitot tube heat is provided by heating elements within each pitot tube head. Power to operate both heating elements is controlled by a single switch on the upper console.
Power to operate both heating elements is controlled by a single switch on the upper console marked
PITOT HEAT OFF and ON. When the switch is placed to the ON position, current flows to the heating elements. Current sensors in the circuits sense the current flow and prevent the LFT PITOT HEAT and
RT PITOT HEAT cautions from appearing. If a heating element fails, the current sensor will detect no current flow, and activate the caution for that pitot tube.
WARNING: Pitot heat and anti-ice shall be on during operations in visible moisture with ambient temperature of 4º C (39º F) and below. Failure to turn pitot heat on in icing conditions can cause the stabilator to program trailing edge down during flight. If this occurs at greater than 40 KIAS, manually slew the stabilator to 0º. b. Pitot-Static System
(1) The Pitot-static system provides pressure for operation of the differential pressure instruments.
Differential pressure used to actuate these instruments is created either by impact (Pitot) and static, or by static and trapped air pressures. The Pitot-static system supplies both Pitot and static pressures to the instruments.
D-29

c. Pitot-Static Head
(1) Left and right pitot-static heads are not interchangeable. Electrically heated pitot-static tubes are located on the cockpit roof above and aft of the pilot and copilot door. The pitot-static heater prevents ice from forming on the tubes. Each pitot tube has two heating elements one in the mast and one in the tube.
WARNING: Injury to personnel will result if pitot-static head is hot. Make sure pitot-static head is cool before attempting to remove.
(2) The pitot-static head assembly consists of a base plate with a strut and probe tube. The base plate contains the pitot tube fitting, two static tube fittings (S1 and S2) and an electrical connector wired to two deicing heaters in the tube. The probe tube contains these pressure sensing ports; pitot, static 1, and static 2. Pitot pressure is sensed at the opening of the front end of the tube. Static 1 and static 2 pressures are sensed at the contoured midsection of the tube. d. Pitot-Static Tube Alignment
(1) Two pitot static heads, located aft and above the pilot and copilot doors, supply the PITOT and
STATIC information to the cockpit instruments. For accurate aerodynamic readings, the pitot tubes are aligned 20 º outboard from a vertical position and with a 3 º nose down attitude.
D-30

e. Pitot-Static Head Assembly
(1) The Pitot-static head assembly consists of a base plate with a strut and probe tube. On UH60A
82-23748 - SUBQ, UH60L-EH60A MWO 50-42 UH-60Q the Pitot-static head assembly is attached to a tapered mounting block assembly surrounded by an aerodynamic fairing that alleviates potential ice buildup at the head assembly/airframe interface.
(2) In addition to standard instrumentation, airspeed data is sensed for operation of stabilator, FPS, and command instrument system. The base plate contains connections for the Pitot pressure tube and, two static tube connections (S1 and S2) and an electrical connector wired to two deicing heaters in the tube. The probe tube contains pressure sensing ports for Pitot, static 1, and static 2. Pitot pressure
(dynamic) is sensed at the opening of the front end of the tube.
(3)The tubing routes ram air pressure to the airspeed indicators and to the Airspeed and Air Data
Transducers, which converts the pressure to an electrical signal for operation of the stabilator, flight path stabilization, and command instrument system. The STATIC 1, or ambient air pressure is sensed at the contoured midsection of the tube.
(4) Static pressure is used by the pilot's barometric pressure altimeter and airspeed indicator along with supplying the Air Data Transducer with STATIC (AMBIENT) air inputs. The STATIC 2, or ambient air pressure is also sensed at the contoured midsection of the tube. Static pressure is used by the copilot's barometric pressure altimeter and airspeed indicator along with supplying the Air speed Transducer with
STATIC (AMBIENT) air inputs. f. Pitot-Static System Installation
(1) Pitot pressure is supplied from the two PITOT-STATIC HEAD ASSEMBLIES through pitot lines to the airspeed indicators, airspeed and air data transducers.
(2) Static air pressure from the atmosphere is supplied from the two PITOT-STATIC HEAD
ASSEMBLIES, through static lines to the altimeters, airspeed indicators, airspeed and air data transducers.
(3) The lines from the PITOT-STATIC HEAD ASSEMBLIES are routed down the sides of the cockpit and are connected to the applicable instruments mounted on the instrument panel. g. Airspeed Indicators
D-31

(1) Two airspeed indicators, one on each side of the instrument panel, indicate helicopter speed in knots. The range is between 0 to 250 knots, marked in 5 knot units.
(2) The indicators are differential pressure instruments, measuring the difference between impact pressure and static pressure. The two pressures are equal when the helicopter is stationary.
(3) As ram air pressure in the pitot tube becomes greater than pressure in the static line, the diaphragm connected to the pressure line will expand, moving the airspeed needle upscale and indicating airspeed in knots.
(4) System installation error is noted on two placards (one each for the pilot and copilot) located on the sides of the lower console. e. Barometric Altimeters
(1) The two Barometric Altimeters indicate altitude above or below sea level. The range is between -
1000 to 50,000 feet as indicated by three drum indicators and a pointer.
(2) The barometric pressure zero set knob in the lower left corner is adjusted to compensate for varying barometric pressures. A small barometric scale, indicates the adjusted barometric pressure setting. Each altimeter has an internal vibrator that decreases the friction in the mechanism.
(3) The pilot's altimeter encoder provides a digital output of pressure altitude to the transponder set
(AN/APX-100). The copilot's altimeter provides a digital output of altitude to the control display unit.
(4) In the event of power failure, a CODE OFF warning flag will appear from a recess behind the dial of the pilot’s indicator. The altimeter encoder functions as a barometric altimeter for the pilot and a barometric altitude sensor for the AN/APX-100 transponder in mode C. The copilot’s functions only as a barometric altimeter.
D-32

f. Airspeed/ Air Data Transducer
(1) The AIRSPEED TRANSDUCER and the AIR DATA TRANSDUCER, sense both pitot and static airspeed data for operation of the stabilator, FPS, and command instrument system. g. Dynamic characteristics of the pitot static system include:
(1) During takeoffs in the speed range of 40 to 80 KIAS the pilot and copilot may see a 5 to 10 KIAS fluctuation between airspeed indicators.
(2) Large power changes in low airspeed climbs may cause up to a 30 KIAS change.
(3) During high power climbs at less than 50 KIAS the copilot system may indicate 30 KIAS less than the pilots.
(4) Opening and closing of doors and windows in aircraft equipped with wedge mounted pitot static probes may cause a momentary fluctuation of up to 300 feet per minute on the vertical velocity indicators.
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D-34