Tableview,
Your understanding is not quite correct. Seat cartridges are qualification tested to ensure they meet the specified Installed and Total lives (Total life being the Shelf life plus Installed life). Provided the cartridges are used within these time limits there is a very high probability that they will operate correctly (but nothing is absolutely certain). If these lives are exceeded there is an increasing risk that the cartridges will not operate correctly and fail to give the required gas pressure to operate the seat mechanism concerned. In the worst case they may not ignite at all.
The cleared lives are usually conservative to account for all the possible variations in environmental conditions, explosive mix and other tolerances. For the escape system to operate correctly a number of cartridges have to operate in sequence and the older they are, the greater the risk that one will fail and interrupt the sequence. However they don't stop working completely as soon as the cleared life has expired.
Another interesting point in the report is that the cartridges were not supplied by Martin Baker so were the units fitted properly qualification tested by an approved supplier, or was this another example of irresponsible corner cutting by the operator.
Last edited by walbut; 5th Sep 2012 at 17:04.