Air Data Attitude Heading Reference System (ADAHRS)
Archangel Systems originally developed an Air Data Attitude Heading Reference System (ADAHRS) to support its EFIS, because there was no low-cost, solid state ADAHRS available on the market. With the development of Archangel’s IM³™ Inertial Measurement Unit (IMU), an advanced MEMS ADAHRS became possible. The current AHR150A is based on this revolutionary IMU and is composed of 2 boxes: an Inertial Sensing Unit (ISU) weighing 3.1 lbs (AHR150A-1) & a Magnetic Sensing Unit (MSU), weighing 0.5 lbs (AHR150A-2).
The ISU contains 4 processors, two of which are dissimilar and which calculate an inertial solution using dissimilar software. Two dissimilar processors calculate an air data solution. The fourth processor controls all communications with the ISU. A fifth processor is contained in the MSU, which provides three axes of magnetic field strength data on an RS422 buss to the ISU. All software in both boxes is DO178b Level A.
The ISU has 8 data ports for transmission and 2 for reception: 4 Hi speed and 4 Lo speed ARINC 429 transmission ports and 1 Hi speed and 1 Lo speed for data reception. ARINC 705-5 and 706-4 data are transmitted on the Hi speed ports and ARINC 706-4 is transmitted on the Lo speed ports. An RS232 maintenance port is also provided on the ISU for field calibration of the MSU, using a Windows™ based calibration routine which is provided with each unit. The maintenance port uses a protective cap with lanyard and contains lockout protect during flight. All connectors are Mil Spec 35899. An AN4 fitting is provided for pitot pressure and an AN6 for static pressure.
Strapping allows the unit to be oriented in 16 varying positions as well as to use 4 different static source error correction tables, all with parity strapping. Discrete inputs are provided for Outside Air Temperature, Angle of Attack as well as DG mode select and CW/CCW compass slewing (both of which can be done via the Lo speed ARINC buss). A master fault discrete output is also provided. For complete information, see the Interface Control Document and Specifications.
The AHR150A system has been chosen by Bell Helicopter Textron Industries for the Bell 609 Tilt Rotor Aircraft. Three AHR150A systems are used as an integral part of the Bell 609 fly by wire system and communicate with the 3 flight control computers as well as the flight displays. The three ISUs are mounted in the nose area while the three MSUs are mounted on the empennage bulkhead.
Jack Gallagher, Program Director for Bell/Agusta 609, expresses the importance of Archangel’s long-term agreement with Bell. He says: "Key to the success of the 609 is cost, performance, weight and schedule; Archangel Systems meets these critical elements and we welcome them to our Team."
Pricing & Delivery Information
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