Copy of post by Zeke over on D & G.
TO: A318/A319/A320/A321/A330/A340/A340-500/A340-600 Operators
SUBJECT: A330 in-flight incident
OUR REF: SE 999.0083/08/LB dated 14 Oct 08
CLASSIFICATION: INFORMATION-FLIGHTS OPS
AFFECTED AIRCRAFT: All A330/A340/A340-500/A340-600 in service aircraft
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Notice:
This OIT/FOT covers an operational issue.
It is the Operators' responsibility to distribute this OIT/FOT, or the information contained in this OIT/FOT, to all A330/A340/A340-500/A340- 600
flight crews without delay.
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1. PURPOSE
The aim of this OIT is to:
- Update operators on the in-flight incident, which occurred on an A330
aircraft on Oct 07th.
- Advise A330/A340 operators about OEBs issuance and associated MMEL
operational procedure impact.
2. EVENT DESCRIPTION
As the incident is subject to a formal ICAO Annex 13 investigation led by the Australian Transport Safety Bureau (ATSB), the updated data about the
incident included in this OIT have been approved for release by the ATSB.
The A330 aircraft was flying from Singapore to Perth. The aircraft has then been diverted to Learmonth (Australia).
The preliminary analysis of the DFDR, Post Flight Report (PFR) and BITE
(Built-In Test Equipment) data allows to establish the following preliminary sequence of events:
The A/C was flying at FL 370 with Autopilot and Auto thrust system engaged
without any reported or recorded anomaly, when the IRS 1 Fault has been
triggered and the Autopilot automatically disconnected.
From this moment, the crew flew manually the aircraft to the end of the flight except for a short duration of few seconds.
From the time the IRS 1 Fault has been triggered, the recorded parameters of the ADR part of ADIRU 1 include erroneous and temporary wrong values in a random manner. These values are spike values and not sustained values. ADIRUs 2 and 3 seemed to have operated normally.
This abnormal behaviour of the ADIRU 1 led to several consequences as
follows:
- unjustified stall & overspeed warning
- loss of attitude information on Captain Primary Flight Display
(PFD).
- several ECAM system warnings.
About 2 minutes after the initial IRS Fault, the ADIRU spikes generated very high, random and temporary values of the angle of attack leading to:
1/ the flight control laws commanding nose-down aircraft movements (A/C
pitch attitude decreased from 2° nose-up to 8° nose-down and vertical load
factor changed from 1g to -0,8g.
2/ the Flight Control Primary Computer (FCPC) "F/CTL PRIM 1 PITCH
FAULT" ECAM WARNING was triggered
The crew timely response led to recover the A/C trajectory within seconds. During the recovery, the vertical load factor did not exceed 1,6g and the maximum altitude loss was 650 ft.
The DFDR data show that the ADR 1 continued to generate random spikes.
A second nose-down aircraft movement was encountered later on, but with
less important effects in terms of aircraft trajectory. It also led to generate the "F/CTL PRIM 2 PITCH FAULT" ECAM WARNING. This, combined with the previous "F/CTL PRIM 1 PITCH FAULT" ECAM WARNING led to switch from
NORMAL to ALTERNATE law.
The BITE message of the ADIRU 1 does not include failure or maintenance
message. However the PFR also includes other system failure messages which
have been demonstrated as spurious but generated by the ADIRU 1.
Tests performed on the A/C following the incident did not reveal any abnormal results that would allow explaining the reason for the event.
At this stage of the investigation, the analysis of available data indicates ADIRU 1 abnormal behaviour is likely at the origin of the event.
The type of ADIRU, which is involved, is NORTHROP GRUMMANN (previously
LITTON), PN 465020-0303-0316.
3. OPERATIONAL RECOMMENDATIONS for A330/A340 fitted with NORTHROP
GRUMMANN - LITTON ADIRU
Pending final resolution, Airbus will issue an OEB 74-1 that will instruct the crew to select OFF the whole ADIRU in case of IR failure, instead of switching OFF only the IR part.
The aim of the following procedure is to isolate both the IR and ADR when
an IR is detected faulty in order to prevent the ADR from providing erroneous data to the other aircraft systems.
PROCEDURE:
- If one IR is self detected faulty or if the ATT red flag is displayed on the Captain or First Officer PFD the supplying IR and ADR must be disconnected.
NAV IR 1(2)(3) FAULT or ATT flag displayed on CAPT (F/O) PFD
-IR 1(2)(3) pb ______________OFF
-ADR 1(2)(3) pb _____________OFF
IF IR 3 NOT AFFFECTED
-ATT HDG SWTG _______________CAPT (F/O) ON 3
-AIR DATA HDG SWTG __________CAPT (F/O) ON 3
- In case of dispatch under MMEL and an IR failure in flight, either detected by an IR 1+2 (1+3)(2+3) FAULT or with ATT red flag displayed on CAPT or F/O PFD, the supplying IR and ADR must be disconnected.
ATT flag displayed on CAPT (F/O) PFD or,
NAV IR 1+2(1+3)(2+3) FAULT
-IR 1(2)(3) pb ____________OFF
-ADR 1(2)(3) pb ___________OFF
SPD BRK____________________DO NOT USE
IF CG AFT 32%:
- T TANK MODE _______FWD
Note: In case of failure of IR 1 and IR 2 failure, the Inertial and Air Data from ADIRU 3 should be provided on Captain side.
Note: To isolate an ADIRU, IR mode rotary selector (OFF; NAV; ATT) remains
in the NAV position so that Inertial and Air Data be disconnected from other systems without de-energizing the ADIRU (NAV mode may be recovered if IR or ADR unduly selected OFF).
4. MMEL IMPACTS for A330/A340 fitted with NORTHROP GRUMMANN - LITTON ADIRU
In case of dispatch under MMEL 01-34-10-01-A), the associated MMEL
operational procedure is amended as follows:
IR (affected) pb sw____________________ OFF
ADR (associated) pb sw _________________OFF
IR (affected) mode rotary sel___________OFF
- If IR 1 (2) is affected:
ATT HDG sel ____________________ CAPT ON 3 (F/O ON 3)
AIR DATA sel ____________________CAPT ON 3 (F/O ON 3)
This will be reflected in MMEL Temporary Revisions:
TR N°02-34/01Z ISSUE 01 for A330
TR N°02-34/01Z ISSUE 01 for A340
5. FOLLOW-UP PLAN
Airbus is working together with the ATSB and the supplier to identify the
ADIRU failure mode.
Additionally, as the same ADIRU PN standard is fitted on single aisle family aircraft, Airbus is currently checking if temporary measures are also required on these aircraft types.
However initial investigation result seems to indicate that single aisle family aircraft flight control system is more robust against this ADIRU failure mode.
OEB 74-1 (A330 family) and 88-1 (A340 family) will be issued in the coming
days.
Specific follow-up of this OIT will be provided through OIT revision when
pertinent information related to investigation results is available