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Advanced Avionics and GPS


The term "Glass Cockpits" refers to instrument displays that are generated digitally on multiple-option computer screens. The Garmin G1000 is the most widely used glass cockpit system in general aviation. These types of systems were developed to improve situational awareness for pilots. Glass cockpit systems are generally broken up into two or more physical displays. The main display that shows the typical flight and navigation instruments is closest to the pilot's centerline of view and is called the Primary Flight Display (PFD). A secondary display(s) provides a more customizable presentation and is called the Multi-function Display (MFD). The MFD may also be used as a backup to the PFD in the event of PFD failure.

Aircraft that use glass cockpit systems are frequently referred to as Technologically Advanced Aircraft (TAA).

Although glass cockpits may ultimately result in better situational awareness and decreased workload, there is a lot of initial and recurrent training required. It is important that pilots flying glass cockpit aircraft remain proficient in all aspects of the systems. Risk may actually be increased when a pilot trusts the automated systems but is deficient in the understanding of their operations. Pilots must guard against complacency when using glass cockpit systems.

Glass cockpit instruments are not operated by conventional gyroscopic systems. A system unit called the Attitude Heading Reference System (AHRS - pronounced A-HARS) uses digital technology to determine the aircraft's status in three-dimensional space and transmits this information to the displayed instruments.

CDI Sensitivity

When an approach has been loaded in the navigation system, GPS receivers will give an “arm” annunciation 30 NM straight line distance from the airport reference point. Pilots should arm the approach mode at this time if not already armed (some receivers arm automatically). Without arming, the receiver will not change from en route CDI and RAIM sensitivity of ±5 NM either side of centerline to ±1 NM terminal sensitivity. Where the IAWP is inside this 30 mile point, a CDI sensitivity change will occur once the approach mode is armed and the aircraft is inside 30 NM.

CDI sensitivity refers to the scaling of the CDI deflection scale. There are three basic modes based on distance from the airport. In terminal mode, for example, a full scale deflection represents 1 nautical mile of cross-track error.



In approach mode, the sensitivity on the CDI changes from 1 NM to 0.3 NM.

TSO - Technical Standard Order

TSO-C129 and TSO-C196 refer to non-WAAS GPS systems.
TSO-C146 refers to WAAS-enabled GPS systems.

When using non-WAAS GPS for navigation and instrument approaches, any required alternate airports must have an approved and operational instrument approach procedure other than GPS.

Handheld GPS units may not be used for IFR operations. VFR waypoints may not appear in an IFR flight plan.

RAIM - Receiver Autonomous Integrity Monitoring

RAIM is the capability of a GPS receiver to perform integrity monitoring on itself by ensuring available satellite signals meet the integrity requirements for a given phase of flight. Without RAIM, the pilot has no assurance of the GPS position integrity.

If TSO-C129 equipment is used to solely satisfy the RNAV requirement, GPS RAIM ability must be confirmed for the route of the flight. If a RAIM failure occurs prior to the FAF (final approach fix) the approach should not be completed using GPS.

Download Advanced Avionics Handbook - Electronic Flight Instruments (FAA-H-8083-3)
Chapter 2 - PDF (47.9 mb)
Download Advanced Avionics Handbook - Automated Flight Control (FAA-H-8083-3)
Chapter 4 - PDF (4.7 mb)