Condor A339 at Frankfurt on Sep 20th 2023, unreliable airspeed

Last Update: January 5, 2024 / 18:10:27 GMT/Zulu time

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Incident Facts

Date of incident
Sep 20, 2023

Classification
Incident

Airline
Condor

Flight number
DE-2086

Departure
Frankfurt/Main, Germany

Destination
Los Angeles, United States

Aircraft Registration
D-ANRA

Aircraft Type
Airbus A330-900

ICAO Type Designator
A339

A Condor Airbus A330-900, registration D-ANRA performing flight DE-2086 from Frankfurt/Main (Germany) to Los Angeles,CA (USA), was climbing out of Frankfurt's runway 25C when the crew levelled off at FL080 reporting a defective speed sensor. The aircraft returned to Frankfurt for a safe landing on runway 25C about 40 minutes after departure.

On Oct 26th 2023 Germany's BFU reported the "unreliable air speed" occurrence was rated a serious incident and is being investigated.

On Jan 5th 2024 the BFU released their Interim Report summarizing the sequence of events:

At 1019:42UTC, take-off run started on runway 25C.

At 1019:52 UTC, the flight crew noticed different speed indications at the left Primary Flight Display (PFD). The pilot occupying the jumpseat said to the PM: “Speed, schau mal bei dir links (look at your left), speed, speed indication“. The PM decided to continue the take-off run and said: “Ja, continue“. According to the PM, the speed display on the PFD 1 was briefly blanked out.

At 1019:59 UTC, the PM said “100 kt” (100 kt IAS1
) and the PF said “Checked”. During the take-off run, the pilots agreed that the speed indications of the Integrated Standby Instrument System (ISIS) was correct. At this moment, the speed display reappeared on the PDF 1.

At 1020:14 UTC, the PM said “V1” and “Rotate”. The aircraft lifted off with a speed of 147 kt IAS (140 kt GS) and a take-off mass of about 232 t (maximum take-off mass was 245 t).

Shortly after take-off, at 1020:31 UTC, the windshear warning sounded. The flight crew realised it was a false message and decided to continue the climb. Under manual control, it was continued up to 8,000 ft AMSL (1029 UTC) (Fig. 1). The DFDR parameters showed that autopilot and auto thrust could not be activated. The PM supported the PF with information from the Pitch and Power tables.

According to the CVR recording, the flight crew identified the erroneous speed indications as Unreliable Airspeed. They decided to classify the speed indications on PFD 1 and PFD 2 as unreliable. The CVR recording showed that the integrated subsystem Air Data Reference (ADR) 1 and 3 of the Air Data Inertial Reference System (ADIRS) processed and displayed erroneous data. The flight crew compared the speed indications on the ISIS with the GPS speed on the two Multipurpose Control and Display Units (MCDU). They realised that the ISIS speed indicated reliable data.

The respective Inertial Reference System functioned properly and the indications on the PFD 1 and PFD 2 concurred with the Standby Attitude Indicator (ADI).

On instruction by the PF, the PM completed the ECAM2 checklist and then read the ECAM status (abridged reproduction): ADR 1 + 3 - uncertain; ADR 2 - reliable; Standby Speed - uncertain; Backup Speed - reliable.

The CVR recording showed that the flight crew performed a FORDEC (six phases for the decision-making process. 1) Facts: What’s the matter or what is going on here?, 2) Options: Possible ways to solve the problem or what are our choices?, 3) Risks and Benefits: What can be said for and against the different options?, 4) Decision: What are we going to?, 5) Execution: Who does what, when, and how?, 6) Check: Is everything still ok or did everything work to plan?) procedure and then decided to return to Frankfurt/Main Airport. They informed the radar controller accordingly. Due to the overweight landing, the PF requested the assistance of the airport fire brigade.

The PF informed the purser about the planned return and landing.

According to the CVR recording, a landing distance of 3,200 m was calculated based on the landing configuration Config 3 and an approach speed VAPP of 165 kt IAS. The landing distance available4 was 4,000 m. The Pilot in Command then took over the function as PF.

After a flight time of about 45 minutes, landing occurred at 1106:33UTC on runway 25C of Frankfurt/Main Airport (Fig. 2). Landing mass was about 226 t which was 35 t above the maximum landing mass, which could be exceeded in emergencies.

After the landing, the aircraft taxied to the parking position.