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Shortly after take off from Gawler SA, the crew of the Cessna 441 Conquest heard a loud air noise. The pilot in command recognised this as the emergency pressurisation system operating. The pressurisation selector switch was checked and found to be in the BOTH position. Selection was made between LEFT and RIGHT, however the air noise continued and there was no activation of the emergency pressurisation warning light. At this point the crew elected not to proceed to Essendon but to divert to Adelaide, where engineering staff were available.

Subsequently, a passenger noticed that the air by his feet was getting hot and advised the crew. Light grey smoke was noticed by the co-pilot in the mid cabin area. The crew conducted the emergency checklist for smoke removal and donned their oxygen masks as a precaution. The storm window was opened to assist with removal of smoke from the aircraft as it was stinging the co-pilot's eyes.

The pilot declared a PAN and, at this point, the aircraft was 2 km abeam Parafield. The crew elected to divert to Parafield, the nearest airfield where emergency services were available. An uneventful landing was carried out and no injuries were reported.

An engineering examination of the aircraft found that the activation of the emergency pressurisation system was initiated by a faulty emergency pressurisation valve. It was also found that, in the process of fitting new side wall trim carpet to the aircraft, the edge of the carpet had not been trimmed around the rear conditioned air duct. This duct supplies air for the emergency pressurisation system and the faulty emergency pressurisation valve allowed hot air to flow unmetered into the cabin. The carpet covering the duct had been exposed to excessive heat, which led to the fumes and smoke in the cabin.

The faulty emergency pressurisation valve was replaced, the carpet trimmed and the aircraft was returned to service.

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