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.