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1
GENERAL DESCRIPTION
1.1
Introduction
This manual presents mechanical and electrical installation requirements for installing the Garmin
GRS 77 AHRS and GMU 44 Magnetometer as part of a Garmin Integrated Flight Deck. The
GRS 77/GMU 44 can be incorporated into a variety of airframes under appropriate TC or STC. Each
airframe installation may vary. Interconnect drawings and procedures that are aircraft-manufacturer
approved must be used during actual installation.
1.2
Equipment Description
The Garmin GRS 77 AHRS (Attitude and Heading Reference System) and GMU 44 Magnetometer are
remote mounted devices that provide flight attitude and heading data for flight instrumentation. With
information available and valid from all sensors, or without the GPS, the GRS 77 AHRS provides valid
attitude, angular rate and acceleration information to the GIA 63(W) Integrated Avionics and the
GDU 104X Primary Flight Display. Approved installations must include a compatible GPS (which is
included in the GIA 63(W)).
An Attitude and Heading Reference System combines the functions of a Vertical Gyro and a Directional
Gyro to provide measurement of Roll, Pitch and Heading angles. The Garmin AHRS and magnetometer
replace traditional rotating mass instruments.
Using long-life solid-state sensing technology, the GRS 77 AHRS and GMU 44 Magnetometer combine
3-axis angular rate, linear acceleration and magnetic field measurements to create an electronically
stabilized AHRS.
The GRS 77 provides the following information in ARINC 429 format:
•
Aircraft heading, pitch and roll
•
Aircraft yaw, pitch and roll rates
•
Aircraft body-axis accelerations
•
Rates of change of heading, pitch and roll
•
Aircraft accelerations expressed in a local level frame of reference
The GRS 77H has the same functions/capabilities of the GRS 77, but has higher vibration capabilities and
compatibility with rotorcraft flight.
The GMU 44 magnetometer provides magnetic information to support the function of the GRS 77.
Operating voltage range of the GRS 77 AHRS is from 10 to 33 volts DC. The GRS 77 provides operating
voltage to the GMU 44 Magnetometer.
The GRS 77/GMU 44 is capable of maneuvers through a range of 360° in bank and pitch. The rotation
rate capability is ±200° per second. However, ARINC 429 angular rate output messages are limited to
±128° per second.
Bank error and pitch error are within ±1.25° over the range of 30° bank, left and right, and 15° pitch nose
up and nose down. Heading is accurate to within 2° in straight and level flight.
GRS 77/GMU 44 Installation Manual
190-00303-10
Page 1-1
Revision L
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