Navigation
The navigation systems provide flight and navigation information for the pilot. It includes the systems that follow:
The Air Data/Attitude and Heading Reference System (ADAHRS) combines the flight environment date and Attitude and direction into a single unit. The Standby Attitude Module (SAM) is a single unit that provides backup flight environment data and attitude information to the pilot. It has backup power for continued operation in case of electrical power failure.
Air Data/Attitude and Heading Reference System (ADAHRS)
The ADAHRS provides its data to the Primary Flight Display (PFD), Multi-Function Display (MFD), and integrated avionics unit (GIA) via ARINC 429 data busses. It also has two-way communications with the integrated avionics unit (GIA) via two RS-232 data busses.
The ADAHRS is located under the floor outboard of the pilot seat in a dedicated mounting rack that makes it easy to replace the Line Replaceable Unit (LRU) when necessary. It has a config module in the backshell of its connector that is used to store configuration information.
Flight environment data
The ADAHRS measures the static and impact pressure with its air transducers, and raw air temperature with the Outside Air Temperature (OAT) probe. It processes the signals to produce the flight environment data that follow:
Air temperature (total, outside/static)
Corrected static pressure
Density altitude
Uncorrected impact pressure
Indicated airspeed
Mach number
Pressure altitude
Total pressure
True airspeed
Vertical speed
Attitude and direction
The ADAHRS uses solid state devices to combine three-axis angular rate, linear acceleration, and magnetic field measurements from the magnetometer (GMU) to create an electronically stabilized Attitude and Heading Reference System (AHRS). It provides the attitude and direction data that follow:
Helicopter heading, pitch, and roll
Helicopter yaw, pitch, and roll rates
Helicopter body-axis accelerations
Rates of change of heading, pitch, and roll
Helicopter accelerations expressed in a local frame of reference
Air Data/Attitude and Heading Reference System (ADAHRS) - Operation
The ADAHRS is energized with 28 VDC from the main bus and can be isolated with the ADAHRS circuit breaker.
The ADAHRS is connected to the flight environment data as follows:
It provides electrical power through its OAT POWER connection to the POWER connection of the OAT probe. The SENSE connection of the OAT probe provides the outside air temperature to the OAT HI connection of the ADAHRS. The LOW connection of the OAT probe to the OAT LO connection of the ADAHRS provides signal and electrical power return.
The impact air pressure from the pitot system is measured by the pressure transducer of the PITOT AIR PORT. The static air pressure is measured by the pressure transducer of the STATIC AIR PORT.
The ADAHRS is connected to the attitude and direction as follows:
The MAGNETOMETER POWER connection of the ADAHRS provides electrical power to the +12 VDC POWER connection of the magnetometer (GMU).
The RS-232 OUT connection of the ADAHRS to the RS-232 IN connection is used to load the software into the magnetometer (GMU).
The POWER GROUND connection of the magnetometer (GMU) to the GROUND connection of the ADAHRS provides a return path for electrical power and signal.
The RS-485 OUT A and RS-485 OUT B connections of the magnetometer (GMU) provide heading data to the RS-485 IN A and RS-485 IN B connections of the ADAHRS.
The shields of the RS-485 line, and of the RS-232 and 12 VDC power line, are connected to the SHIELD GROUND connections of the magnetometer (GMU).
The ADAHRS config module is used to store configuration data.
The ADAHRS provides electrical power through the CONFIG MODULE POWER OUT connection to the VCC connection of the ADAHRS config module.
The CONFIG MODULE DATA connection of the ADAHRS to the DATA connection of the ADAHRS config module writes the data to and reads the data from the ADAHRS config module.
The CONFIG MODULE CLOCK connection of the ADAHRS to the CLK connection of the ADAHRS config module controls the reading and writing of data.
The CONFIG MODULE GROUND connection of the ADAHRS to the GND connection of the ADAHRS config module provides electrical power and signal return.
The ADAHRS processes the flight environment data and the attitude and heading data. It then provides the data to the MFD , PFD , and integrated avionics unit (GIA) via ARINC-429 data busses.
Two bidirectional RS-232 data busses are used to load software and configuration files, read status, and provide Global Positioning System (GPS) data to the ADAHRS.
Standby instruments
The Standby Attitude Module (SAM) is a self-contained unit with two 2.4 inch (60.7 mm) LCD displays with a wide viewing angle, a single control knob, and an integrated, rechargeable, lithium-ion battery that gives it 2 hours of autonomy without helicopter power. Attitude and slip indications are shown on one display, the other display shows speed and altitude. It has four modes of operation:
Pre-flight: Gives system information when first energized.
Flight: Shows normal flight information.
Emergency: Shows flight information when on battery power; helicopter electrical power has failed.
Configuration: Lets you change system settings and update software.
The SAM config module is installed in the connector backshell and stores configuration data. The SAM is located at the top and in the center of the instrument panel.
Standby Attitude Module (SAM) - Operation
The SAM is energized with 28 VDC from the main bus, and can be isolated with the STBY INSTR circuit breaker.
The SAM operates normally until power is removed from the +10-32VDC INPUT connection.
The SAM is grounded through its POWER RETURN/GND connection to a grounding point on the helicopter structure.
The SAM provides power from its CONFIG MODULE POWER connection to the CONFIG POWER connection of the SAM config module.
Signal and power return is from the CONFIG RTN connection of the SAM config module to the CONFIG MODULE RETURN connection of the SAM.
Read and write operations use the CONFIG MODULE DATA connection of the SAM to the CONFIG DATA connection of the SAM config module.
The control of read and write operations uses the CONFIG MODULE CLOCK connection of the SAM to the CONFIG CLOCK connection of the SAM config module.
The flight environment data provides the air pressure to the PITOT AIR PORT and the STATIC AIR PORT of the SAM.
The internal battery is recharged when the SAM operates normally with helicopter power.
When power is removed in flight, the SAM operates in emergency mode with the internal battery power.
When power is removed on the ground and the helicopter is not moving, the SAM shows the POWERING DOWN message, telling the pilot that it will shut off in 60 seconds.
Flight Environment Data
The flight environment data provides pitot air pressure and static air pressure to the Air Data/Attitude and Heading Reference System (ADAHRS) and the Standby Attitude Module (SAM). It also provides air temperature to the ADAHRS. It consists of the Outside Air Temperature (OAT) probe, pitot tube, pitot lines, left and right static ports, and static lines.
The flight environment data is sensed and processed by the ADAHRS and the SAM.
Outside Air Temperature (OAT) probe
The OAT probe provides outside air temperature to the ADAHRS. It is located on the left side of the belly.
Pitot tube
The pitot tube collects ram air from outside of the helicopter. It is also electrically heated to prevent ice from blocking the air passage. It is located on the right side of the forward belly panel.
Static ports
The left and right static ports are located on either side of the cabin, under the left and right windshield. They sense the atmospheric pressure around the helicopter.
Pitot line
The pitot line supplies the air impact pressure sensed by the pitot tube to the transducers in the ADAHRS and the SAM.
Static lines
The static lines provide the atmospheric pressure sensed by the static ports to the transducers in the ADAHRS and the SAM.
Flight Environment Data - Operation
The OAT probe is connected to the ADAHRS.
The impact air pressure from the pitot tube is directed by the pitot lines to the transducers in the ADAHRS and the SAM.
The static air pressure from the static ports is directed by the static lines to the transducers in the ADAHRS and the SAM.
Pitot heater
The pitot heater prevents the formation of ice on the pitot tube for authorized flight regimes. It consists of the pitot heater switch, pitot heater relay, and pitot tube heating element.
Pitot heater switch
The pitot heater switch is located on the miscellaneous control panel. It activates the pitot heater element.
Pitot heater relay
The pitot heater relay is located under the cabin floor on the left side. It controls the application of electrical power to the pitot heater element depending on the setting of the pitot heater switch.
Pitot tube
The pitot tube is located on the right side of the forward belly panel. It is also electrically heated. When it is powered, the heating element inside the pitot tube prevents the formation of ice on the pitot tube.
Pitot heater - Operation
The pitot heater circuit is energized with 28 VDC from the main bus and can be isolated with the PITOT HTR circuit breaker.
The 28 VDC is applied to the COM1 connection of the pitot heater relay and to the coil of the pitot heater relay.
Setting the pitot heater switch to the PITOT HTR position applies a ground to the other side of the coil of the pitot heater relay and energizes the relay. It also makes the PITOT ON Crew Alerting System (CAS) message to display.
The 28 VDC is applied to the pitot heater element through the NO1 connection of the pitot heater relay.
Attitude and Direction
The attitude and direction system provides the magnetic data to be processed by the Air Data/Attitude and Heading Reference System (ADAHRS). It also provides standby magnetic information to the pilot.
The attitude information is provided by the ADAHRS. The standby attitude information is provided by the Standby Attitude Module (SAM).
The attitude and direction system consists of the GMU 44 magnetometer and the standby compass.
GMU 44 magnetometer
The magnetometer uses solid state devices to provide magnetic field data to the ADAHRS. It is located in the tailboom on a dedicated mounting rack.
Standby compass
The standby compass provides backup heading information to the pilot. It is a fluid dampened magnetic type compass that is correctable for magnetic heading errors induced by the installation location. The standby compass is located on the windshield centerpost. A deviation card, located above the right windshield, is also provided to indicate remaining uncorrected magnetic heading errors.
Attitude and Direction - Operation
The +12 VDC POWER connection of the magnetometer (GMU) is energized by the MAGNETOMETER POWER connection of the ADAHRS. The return path is provided by the POWER GROUND to GROUND connections.
The ADAHRS provides configuration data by its RS-232 OUT connection to the RS-232 IN connection of the magnetometer (GMU).
The magnetic heading data is provided to the RS-485 IN A and RS-485 IN B connections of the ADAHRS by the RS-485 OUT A and RS-485 OUT B connections of the magnetometer (GMU).
Protection from interferences is provided by the SHIELD GROUND connections of the magnetometer (GMU).
The standby compass provides backup magnetic heading information to the pilot and copilot. Lighting for the standby compass is provided by the cockpit lighting.
Dependent Position Determining
The dependent position determining system includes the Global Positioning System (GPS), the VHF Omnidirectional Range (VOR) and Glide/Slope (G/S) receivers, and the mode S transponder. It provides navigational data to the indicating/recording system and replies to interrogations from Air Traffic Control (ATC) ground radars. For a system discussion and/or description, refer to Dependent Position Determining.
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