During a scheduled test an escape slide automatically initiated, the door opened and stopped at the half-open position. The door seemed to be held half-opened by the slide assembly for 30 seconds, and finally went fully open by itself after the slide released without assistance. The slide failed to inflate automatically after the slide released from it’s storage. The slide inflation was done manually. The door bottle and slide bottle pressure were checked in the green band before the slide deployment test.
This is a real event and highlights the importance of reliable escape slide deployment and how following correct maintenance procedures, and reporting slide deployment test results to Airbus, is essential for ensuring that escape slides will properly deploy when they are most needed.
"The door seemed to be held half-opened by the slide assembly for 30 seconds..."
Undisclosed Airbus Operator
The reader may have experienced similar cases of slide non-deployments, as the operator whose report the extract above was taken from.
Studies performed on incorrect maintenance reveal that, as far as the equipment and furnishings are concerned, the most frequent issue is related to escape slides.
Researchers at the National Aerospace Laboratory (NLR) – Netherlands analyzed data for Western-built commercial passenger aircraft equipped with evacuation slides; they compared categories of slide problems with those identified in earlier studies, and made the following safety1 recommendations:
The NLR report concluded that improper system packing/installation and improper maintenance of systems caused many of the slide inflation problems.
The Airbus Maintenance Event Analysis Panel (MEAP), which reviews maintenance-related in-service events, has received quite a number of reports on escape slides.
Each individual report has been reviewed, with corresponding root cause analyses, to confirm the circumstances as well as the maintenance and shop processes used. Overall findings confirm the study made by the NLR.
This Maintenance Briefing Note provides a summary of the findings, the reasons behind, and recommendations for correct slide operation.
Some examples of escape slide non-deployments are listed below without any order of priority, and this list is not exhaustive:
Many of the reasons which may lead to non-deployments can be traced back to an improper packing of the slides, the so-called “fat packing”. If the slide is not packed as per the vendors’ folding instructions, the external dimensions can be outside the normal final envelope, which could affect the dropping kinematics of the slide pack and possibly lead to a non-automatic deployment.
It is acknowledged that the slide folding procedure is a complex and time-consuming process. However, the investment in strictly following the procedures as required and described by the vendor manuals, will pay off in avoiding troubleshooting (time) further to slide non-deployment due to improper packing procedures (hidden problems).
Particular attention should be given to the heating process, aiming at softening the slide/ raft fabric, to achieve a higher pack density.
It is also important to verify the external dimensions after packing, using the three-dimensional check tool and/or the cover, to make sure that the packed slide agrees with the correct pack dimensions, depending on the build standard and the requirements of the relevant supplier’s instruction manuals.
The slide deployment test is requested in the Maintenance Review Board Report (MRBR), and the Maintenance Planning Document (MPD) accordingly, with the following intervals:
Every reported event is analyzed by the Airbus Customer Services Engineering experts and the MEAP, to determine if design modifications are necessary. Up to now, no major design change of the escape slides and the related systems was identified.
The AMM instructions were thoroughly reviewed, and improvements were implemented as explained below, incorporated in the April 2006 revision.
There are two different electrical harness routings according to the installation side. Previously, the AMM contained an illustration showing the installation only on one side, with a remark that, on the opposite side, the routing should be the mirror image. These illustrations were modified to display the installation of each electrical harness routing on the left and on the right sides, to avoid the mental acrobatics required to imagine the routing not depicted for the other side.
Similar modifications were asked to be included in the supplier documentation.
OIT/FOT SE 999.0023/05/SH, dated 24 Mar 2005
ATA 25-60 – A320 Fam slide and slide raft maintenance.
Recommendations regarding the A320 Family emergency slide/slide raft packing procedures and installations on aircraft as well as the slide/slide raft inadvertent deployment prevention.
OIT SE 999.0131/05/VHR, dated 17 Nov 2005
A318/A319/A320 – ATA 25-60 off wing slide wire control assembly maintenance operations.
Recommendations regarding the maintenance operations of the A318/A319/A320 Wire Control Assembly (WCA), sub-part of the off-wing slide reservoir and valve assembly 60592 series.
OIT SE 999.0015/07, dated 01 Feb 2007
A300/A300-600/A310 Slide/rafts maintenance recommendation.
Highlighting that units not packed as per the applicable Air Cruisers folding procedures could lead to pack jamming below the decorative cover.
OIT SE 999.0069/08/BB, dated 22 Aug 2008
ATA 25-60 – Slide maintenance recommendation.
Recommendation for a VSB to avoid a non-inflation of the slide because a missing coupling pin within the valve assembly did not allow the pressure to be released into the associated hoses.
OIT SE 999/0087/11, dated 14 Nov 2011
Information about SIL 25-061 and introduction of the Slide Deployment Report in the AMM tasks for operational check. This report is applicable to all slide deployments, scheduled or inadvertent, successful or unsuccessful.
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