18 May 2021
18. May 2021 Commercial Aircraft

Good Practices for Escape Slide Maintenance to Ensure Successful Deployment

Ensuring safe and efficient maintenance across the entire aircraft lifecycle

28   Slide Maintenance2 01
28   Slide Maintenance2 01    
 
Fig3  No Wrapper    
 
Fig4   Incorrect Restraint    
 

Did you know that the most significant escape slide problems involved inflation, aircraft attitude, wind, fire, incorrect rigging and tears?

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

Fig4   Incorrect Restraint
IS THIS AN ISOLATED CASE?

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:

  • Examination of NLR’s study sample of 150 survivable aircraft accidents in which slides were used during 1970-2003 showed that in 81 cases (54%), one or more slides did not operate properly.
  • Examination of NLR’s study sample of 155 aircraft incidents in which slides were used showed that in 10 cases (6.5%) one or more slides did not operate properly.

Safety Precautions

If the slide does not deploy during a test, the deployment area must remain clear of any personnel as there is the risk that the slide can suddenly inflate until the slide is correctly secured. Sudden slide raft inflation may cause injuries or damage to equipment. It is recommended to carefully take photos from the inside and from the outside of the aircraft in addition to recording details of the position of the slide during a failed test. When it is confirmed that the slide is not obstructed by the door frame or its compartment the operator can then pull the manual inflation handle. This will ensure that the slide inflation gas cylinder is empty and that the slide is in a safe condition to handle.

SHOP MAINTENANCE 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:

  • Incorrect routing of the activation cables and harnesses within the door
  • Retaining strap (lacing) used for pack transportation and stowing not removed before installation
  • Incorrect packing of the slides during shop maintenance
  • Missing coupling pin in the reservoir and valve assembly

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. 

SCHEDULED MAINTENANCE

The slide deployment test is requested in the Maintenance Review Board Report (MRBR), and the Maintenance Planning Document (MPD) accordingly, with the following intervals:

  • A300: National Requirements (NR) or 18 Months (MPD task 256111-0503-2)
  • A310, A300-600: NR or 36 Months (MPD task 256120-06-1)
  • A320 Family: Not to exceed 36 Months (MPD task 256242-03-1 and 256241-04-1)
  • A330/A340: 36 Months (MPD task 256241-03-1)
  • A350XWB: 60 Months (MPD 256200-00M06-01)
  • A380: Not to exceed 36 Months (MPD task 256200-00005-01) 
DESIGN AND THE AIRCRAFT MAINTENANCE MANUAL

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. 

SUMMARY OF RELEASED OPERATOR INFORMATION

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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Summary

Escape slides can save lives in emergency situations. Slide overhaul should only be done by certified maintenance organizations. Particular care should be taken to pack the slide using the latest folding instructions provided in the CMM or in the folding document. AMM procedures and recommendations must be carefully followed during installation and servicing of the slides to ensure the correct deployment of the slide. Periodical slide deployment tests should be done on aircraft in an operational configuration and with approved fuselage protection in accordance with the AMM/MP recommendations. This will mean that the test is representative of the slide deployment in operational conditions. A thorough reporting of both unsuccessful and successful slide deployments during scheduled tests, an inadvertent deployment or in any emergency situation is essential for Airbus and its suppliers to assess slide reliability. In case of an unsuccessful slide deployment, providing videos and photos of the event in addition to a detailed report facilitates identification of root causes and enables the continuous improvement of slide deployment reliability.

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Good Practices for Escape Slide Maintenance

Good Practices for Escape Slide Maintenance

Supporting airlines to safely return to service

Article by

Jean-Philippe Jacq

Senior Director Safety Maintenance & Engineering for Airbus Customer Services

Cyril Montoya

Product Safety Enhancement Manager

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