Narrative:

Upon initial climb out; the crew detected a rushing of air sound in the cockpit and noticed an abnormal pressurization bump. After continuing the climb for several minutes; the temperature of the rushing air was getting very hot and we could visibly see a smoke starting to develop and smelled like a burning odor. At this point; the pilot flying elected to level off and instructed the pilot monitoring to declare an emergency with the tracon.an emergency was declared and we requested to return to the airport for landing. Due to our fuel load; we had to make an overweight landing; 727 pounds acgw. After touchdown; crash/fire/rescue followed our aircraft in to the ramp as a precaution. After parking; we informed the fire and rescue crew that we were all clear and did not require any further assistance from them.as a precautionary measure; the fire crew did a visual inspection of the aircraft to verify that there was indeed no fire aboard the aircraft. The flight crew elected to not drop oxygen masks for passengers or use crew oxygen masks as the smoke never accumulated enough to require the use of emergency oxygen. There is nothing that could have prevented this maintenance related emergency.

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Original NASA ASRS Text

Title: A BAE-125 air crew declared an emergency and returned to their departure airport after experiencing abnormal pressurization bump. Additional symptoms included a rushing air sound which was increasing in temperature and beginning to give off a burning odor.

Narrative: Upon initial climb out; the crew detected a rushing of air sound in the cockpit and noticed an abnormal pressurization bump. After continuing the climb for several minutes; the temperature of the rushing air was getting very hot and we could visibly see a smoke starting to develop and smelled like a burning odor. At this point; the pilot flying elected to level off and instructed the pilot monitoring to declare an emergency with the Tracon.An emergency was declared and we requested to return to the airport for landing. Due to our fuel load; we had to make an overweight landing; 727 pounds ACGW. After touchdown; Crash/Fire/Rescue followed our aircraft in to the ramp as a precaution. After parking; we informed the fire and rescue crew that we were all clear and did not require any further assistance from them.As a precautionary measure; the fire crew did a visual inspection of the aircraft to verify that there was indeed no fire aboard the aircraft. The flight crew elected to not drop oxygen masks for passengers or use crew oxygen masks as the smoke never accumulated enough to require the use of emergency oxygen. There is nothing that could have prevented this maintenance related emergency.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.