Flight instrumentation is critical to the safety of commercial, transport, and business flights alike. When instruments aren’t displaying or calculating accurate information, the next steps of the flight can’t be determined with accuracy. Pilots and flight systems rely on the accuracy of sensors and displays to make adjustments to flight, especially in emergency situations. While it may not be possible to repair or replace malfunctioning instruments in-flight, issues should be recorded and addressed immediately by the flight crew. Recorded issues must be specific and detailed.
For each piece of digital equipment, there a multitude of problems that can occur. For aircraft sensors, the main issues are:
Each issue requires a different repair process. Detection problems can indicate a manufacturing defect, calculation errors, or broken equipment. If there is a known manufacturing error, the equipment may be replaced or repaired at no cost.
Whether the person repairing the equipment is in-house or 3rd party, it is easier and less time-consuming to fix known problems. When an equipment problem is discovered, it should be recorded and communicated with specificity and detail. In some instances, the descriptions are very vague. Maintenance may get a report that merely describes equipment as “not working” or “messed up”. The crew must be trained to use detailed descriptions.
On 8 January 2016, malfunctioning equipment led to a fatal crash near Akkajaure reservoir in Sweden. West Air Sweden Flight 294 was carrying mail and packages to Tromso, Norway. The aircraft was flown by two pilots. The pilot in command reacted to incorrect data provided by the pilot flight display, which led to the crash.
The pilots were relying on pilot flight displays due to low visibility conditions. The display detected an increase in pitch in the left attitude indicator, which was caused by a malfunction of the inertial reference unit (IRU). The autopilot disconnected. Two altitude indicators were displaying conflicting information. The aircraft lost altitude and crashed.