Heraklion-Bound Discover Airlines Flight Returns to Frankfurt

A Discover Airlines flight bound for Heraklion, Greece made a return to Frankfurt due to a technical issue on 5 June 2024.

Discover airlines flight 4Y1204, an Airbus A320-200 operating out of Frankfurt Main Airport reported a technical fault whilst en route over Austrian airspace.

Discover Airlines 4Y1204 Frankfurt-Heraklion

According to the online source Aviation Herald, the aircraft experienced a failure of its Integrated Standby Instrument System (ISIS).

Flight crew elected to make a precautionary return to the origin airport at Frankfurt following the system’s failure.

The aircraft subsequently landed without further issue approximately one hour after the diversion was made.

Flight Details

Flight data shows that flight 4Y1204 made an on-time departure out of Frankfurt (FRA), at 0506 local time on 5 June.

The flight then set course normally for Heraklion International Airport (HER) Crete, climbing to flight level FL370 (37,000 feet) for the south easterly route.

The flight had passed into Austrian airspace when the decision was made to initiate a return to Munich. The diversion was made at approximately 0345 UTC, and a descent and direct return track was then initiated.

The aircraft conducting the flight 4Y1204 rotation to Heraklion was an Airbus A320-200, registered D-AIUQ. This is an 8.4 year old narrowbody aircraft belonging to the Lufthansa Group subsidiary carrier Discover Airlines.

The aircraft is operated with the carrier since July 2022. Prior to that it is operated with the main airline Lufthansa since its initial delivery in February 2016.

ISIS System

The Integrated Standby Instrument System (ISIS) on an Airbus aircraft is an electronic instrument that acts as a backup in case the main glass cockpit instruments fail.

This allows pilots to still see critical flight information even if the primary system malfunctions.

Traditionally, these backups were separate mechanical instruments for attitude, airspeed, altitude and heading.

The ISIS combines all this information into a single electronic display. This saves space on the instrument panel and can potentially improve information integration for the pilot.

Here are some of the things typically displayed on an ISIS:

  • Attitude (artificial horizon)
  • Airspeed and Mach number
  • Altitude
  • Barometric pressure
  • Landing gear status (landing gear selection and landing gear down indication)
  • Course deviation indicator for the Instrument Landing System (ILS)

The ISIS is essential for maintaining situational awareness during a situation where the primary instruments are unavailable. This allows the pilots to safely control the aircraft and navigate until the primary systems can be restored.


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