Flight Level 410 and down!
CHIPPIE CHAPPIE / G-SPOTs Lost and others if interested.
Part 2 cont.
At Ratmalana, engineers ( who had flown in from Singapore) took the pressurization system to pieces, changed the door seal (at this stage the main culprit), made tests and then put it all back together. A test flight was carried out, it was satisfactory, so we then went to Colombo airport, cleared the formalities and departed for Singapore. The flight was uneventful.
We thought that was the end of the problem, however 11 days later on a trip to Kota Kinabalu, the second and same problem returned. Just after the top of climb the door seal collapsed again, so down we went. We had new oxygen masks that worked, so no real drama. Upon landing at KK, the Regulatory Authority Airworthiness people had a good extensive look at what a cabin looks like on this type of aircraft after an emergency descent. Engineers went through the whole process again and so the saga continued.
The elasped time of the flight when the seal collapsed was about the same as the first incident, so that was a clue.
The aircraft behaved itself for another 42 days and then came the third incident. In the middle of the night over the middle of the South China Sea , we had the whole issue again.
The Engineers, The Authority and myself said enough is enough and so the aircraft was grounded until the reason for the problem was found.
It took some days for the Engineers and The Authority to find the problem. The whole of the interior near the door and the incoming pressurization line was taken out. It was found that the heating and cooling ducting was not putting any warm or hot air to the non-return valve at the lowest point of the pressurization plumbing. The valve was non - return in name only, so we suspected that freezing had something to do with the problem. We also found that the incoming pressurization line had some moisture and water in it. The Manufacturer of the aircraft said this was not possible, however they were wrong. We put the valve in a deep freeze ( of course it was not cold enough) , so the decision was taken for a test flight with a camera on board. Sure enough the whole valve became frozen with hoar frost which would also include the water and moisture inside, so the problem was found.
The fix was to fit a duct that supplied hot air to the valve all the time. This coupled with a purge of the pressurization line upon right hand engine start to get rid of any moisture fixed the problem and there were no more door seal issues. The Manufacturer issued a modification for all existing and future models to be incorporated.
That is the end of this story, hope it has been of interest to you.
We all live and learn ,I certainly did!
Tmb