In a Cirrus SR20, glass cockpit display failures most commonly manifest as a blank screen (PFD hardware failure), a “Red X” over a display tape (AHRS/ADC failure), or intermittent power interruptions. These issues are typically not user-serviceable and require a certified avionics technician for proper diagnosis and repair.
Common Glass Cockpit Failures
1. PFD Hardware Failure (Blank Screen)
This is a total hardware failure of the Primary Flight Display (PFD) unit or an interruption of its power supply. The screen goes completely blank. In the SR20, which has a dual-screen setup, this triggers reversionary mode, where the PFD information automatically transfers to the Multi-Function Display (MFD) in the center of the panel. This allows the pilot to continue flying with all critical flight information available on one screen, supplemented by the backup analog instruments.
2. Attitude Heading Reference System (AHRS) or Air Data Computer (ADC) Failure (“Red X”)
The most famous glass cockpit failure is the “Red X” that appears over a display. This indicates that the PFD is no longer receiving reliable data from a key sensor. For a Cirrus SR20, this typically points to a failure of the AHRS (which provides attitude and heading information) or the ADC (which provides airspeed, altitude, and vertical speed data).
A “Red X” over the airspeed tape, for example, could be caused by a blockage in the pitot tube.
3. Total Electrical Failure
While less common due to redundant systems, a total electrical failure will cause both the PFD and MFD screens to go blank. In this scenario, the pilot must rely on the standby instruments, which are typically a separate, battery-powered electronic attitude indicator, airspeed indicator, and altimeter.
How to Fix the Failures
Fixes for these failures are largely not in-flight pilot actions, but rather maintenance tasks performed by a certified technician.
- PFD Hardware Failure: If the PFD remains blank after a flight, the avionics technician will first check the power supply and wiring. If the issue is with the display unit itself, the unit is not user-serviceable. It must be removed from the aircraft and sent to an authorized Garmin service center for repair or replacement.
- AHRS/ADC Failure: The technician will perform a detailed diagnostic check. They will analyze the system’s log files to pinpoint the exact time and nature of the sensor failure. The repair could involve:
- External Issues: Cleaning a blocked pitot tube or static port.
- Wiring Problems: Checking for loose, chafed, or corroded wiring.
- Component Replacement: If the sensor itself is faulty, the AHRS or ADC unit must be replaced. These are also sealed, non-field-serviceable units.
- Total Electrical Failure: The repair focuses on the aircraft’s electrical system, including the main alternator, standby alternator, voltage regulators, and battery. The technician will perform a comprehensive check to identify the faulty component and replace it