Event Details

Title:A serious incident which occurred on 30 January 1998, in the airspace 10 NM east of Stockholm/Arlanda airport between the aircraft with registry YL-BAN and SE-DUR
Micro summary:A failure of electronic flight instrumentation on this BAe-146 results in an altitude bust.
Event Time:1998-01-30 at 1021 UTC
File Name:1998-01-30-SE.pdf
Publishing Agency:Swedish Accident Investigation Board (AIB)
Publishing Country:Sweden
Report number:C 1998:18e
Site of event:Airspace 10 nm east of Stockholm/Arlanda airport
Latitude/Longitude:5941N 1820E
First AirplaneSecond Airplane
Departure:Stockholm-Arlanda Airport, Marsta, SwedenUnknown
Destination:Tallinn Airport, Tallinn, EstoniaStockholm-Arlanda Airport, Marsta, Sweden
Airplane Type(s):BAe 146/RJFokker F28 Mk0100
Flight Phase:ClimbDescent
Operator(s):Air BalticTranswede Airways AB
Type of flight:RevenueRevenue
Serious Injuries:00
Other Injuries:00
Executive Summary:Aircraft A, a Bae 146/RJ with registry YL-BAN, initiated a scheduled IFR passenger flight on the 30th of January, 1998 at time 10:18 from runway 08 at Stockholm/Arlanda airport with destination Tallinn in Estonia via VOR-station NTL. Initially the flight received clearance to climb to flight-level (FL) 70 (2 150 m). After takeoff A was followed on radar by an air-traffic controller at the ARR-E sector of Stockholm control (ACC). Simultaneously during A’s easterly climb, aircraft B, a Fokker F28 MK0100 with registry SE-DUR was descending; arriving from the north for landing on runway 01 at Stockholm-/Arlanda.

As the two aircraft flight paths would intersect each other, the ATC controller limited B’s descent to FL 80 (2 450 m) in order to maintain requisite separation to A. When the two aircraft flight paths crossed one another the ATC controller observed that the radar echoes “merged” and the altitude information of same disappeared, which indicated that the separation had diminished below the minimal. When the echoes once again became visible the controller discovered that A’s altitude readout was FL 75 (2 300 m) climbing.

The crew of aircraft A has stated to SHK that during takeoff, just prior to liftoff from Stockholm/Arlanda, they experienced a technical mishap with the aircraft that resulted in the failure of most of the automated functions and the blinking of a number of warning lights (i.e. Flight Guidance Computer, Yaw Damper, Autopilot, Thrust Rating Panel, Flight Director, Altitude Preselect Alert). Aircraft type Bae 146/RJ is fitted with the latest technical equipment with a high degree of automatization and electronic instrument presentation. The crew’s impression was that the aircraft was therefore more difficult to fly on the reserve instruments than older aircraft with conventional instrumentation.

While the copilot flew the aircraft on the reserve instruments the commander attempted to restart the failed systems. According to the crew’s recollection, it was during this period that their cleared altitude of FL 70 was exceeded up to FL 75 – 77. Simultaneously as measures were taken to return to FL 70 aircraft A received clearance to climb further to FL 140. When separation minimum was violated A received an automatic collision warning (TCAS) in the Traffic Advisory format (yellow solid circle).
Learning Keywords:Operations - Airspace - Air Proximity
Operations - Airspace - TCAS
Operations - Altitude Excursion
Systems - Flight Instruments


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