Avionics Systems Issues

BTeter

Tuesday, February 21, 2023 at 03:00 PM ET

Verified

Modern IMUs using MEMS are compact and far less expensive than their predecessors.

Key Takeaways:

Modern flight-critical data (attitude, heading, airspeed, altitude) are generated by integrated digital systems, with AHRS often relying on "aiding" from redundant GPS, Air Data Computers (ADC), and magnetometers to ensure accuracy and fault tolerance.
Lack of redundancy or signal disruptions in aiding sensors (e.g., single GPS input, GPS jamming) can lead to the loss of all primary flight information, making robust system design critical for reliability.
Blocked pitot or static lines represent a dangerous and often undetected failure mode, producing erroneous airspeed and altitude data that can mislead pilots, trigger unsafe automated responses, and cause illogical instrument indications.
In an instrument failure scenario, pilots must avoid fixation on a single instrument, diligently cross-reference information, know appropriate pitch/power settings, utilize alternate static sources if available, and be prepared to declare an emergency.

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Flight-critical information for IFR flying includes attitude, heading, airspeed, and altitude. Navigation information is high on the needs list but is not as critical as the previous items. The same is true for communications. The criticality generally follows the doctrine of aviate, navigate, and then communicate. Likewise, the FAA system safety analysis (required for equipment certifications) places the highest criticality requirements on attitude, heading, airspeed and altitude.

Here, I’ll first explain how the flight-critical data is generated in today’s digitally integrated cockpits, possible failure modes, and then I will dig into possible propagation of a failure across other functions in an integrated system. Last, I will discuss recommendations for handling the situation.