Event Details

Title:Autopilot malfunction, Serious incident occurring on December 3, 2002 near Munich, involving an Airbus A300-600 (Recommended)
Micro summary:This A300-600 experienced serious autopilot trim malfunctions.
Event Time:2002-12-03 at 1040 local
File Name:2002-12-03-DE.pdf
Publishing Agency:Federal Bureau of Aircraft Accidents Investigation (BFU)
Publishing Country:Germany
Report number:5x011-0/02
Site of event:Climb from Munich
Departure:Munich International Airport, Munich, Germany
Destination:Dresden Klotzsche Airport, Dresden, Germany
Airplane Type(s):Airbus A300-600
Flight Phase:Climb
Type of flight:Revenue
Serious Injuries:1
Other Injuries:0
Executive Summary:The airplane had 189 passengers and 8 crew members on board and took off at 10:40 hrs in Munich for a scheduled flight to Frankfurt.

While climbing to cruise level with autopilot (AP2) engaged the crew noticed during a routine check of the instruments that the allowed airspeed (VMO) would be exceeded. As a countermeasure the preset speed was reduced and a higher climb rate selected on the AP panel. The AP was disengaged after it was noted that the airspeed increased further and the nose started to drop.

Once the pilot took control of the airplane it was trimmed nose down. It was no longer in climb and the maximum allowed airspeed was exceeded by 16 kt. A great amount of control forces had to be applied until the wrong trim could be correct by means of the electrical trim device. Vertical acceleration was so
great during the re-establishment of the original flight attitude that one crew member fell and injured herself slightly. The flight was continued with disengaged AP and no further incidents.

Causes for the serious incident

As a result of the deferred elimination of a fault on PTS 1 the AP could be operated with PTS 2 only.

There was a fault on PTS 2 for which there was no confirmation or elimination

At a certain airspeed the signal interruption between engaged AP 2 and PTS 2 caused a continuous change of the THS in direction of pitch down.

Because of a system deficiency caused by the software error in FAC 2 the continuous change of the THS did not result in a warning and the self-deactivation of the system.

The prescribed procedure for abnormal functions (AOM) of the trimable horizontal stabilizer was not executed in time. Systemic causes contributing to the serious incident:

Approval of the MMEL did not take into consideration that during AP operations there is no redundancy once one PTS in inoperable.

The MMEL of the aircraft manufacturer and the resulting MEL of the operator did not contain clear criteria for resource scheduling; especially whether an aircraft with inoperable systems and equipment can be released for flight by the maintenance base.

The MMEL did not take into consideration that by surrendering PTS 1 normally both APs use this system and an unhindered function of PTS 2 with both APs was not ensured.

The maintenance instructions and operation procedures contained no or insufficient regulations how to deal with such a situation where a PTS 2 complaint could not be reproduced on ground.

Design and certification procedures of EUROCAE dated 1982 regarding software for aircraft in the scope of the certification process of changes did not included a function check for the whole system or module.

Neither schooling nor periodic training educated pilots sufficiently on how difficult it is to recognise abnormal system functions during auto flight operations (pitch up/down).
Learning Keywords:Operations - Trim Misset
Systems - Automation Design
Systems - Automation Errors
Consequence - Flight Attendant Fatality - Injury


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