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Mu-2 captain experiences very cold conditioned air at FL180. Initial attempts to warm the air are unsuccessful until manual is selected; then the air becomes too hot producing smoke. Attempts to cool the air using manual control are unsuccessful initially; so the bleeds are turned off and the aircraft is descended to 11;000 feet. Flight continues to destination at 11;000 feet.
| Attributes | |
| ACN | 1276084 |
| Time | |
| Date | 201507 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZAU.ARTCC |
| State Reference | IL |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | MU-2 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 91 |
| Flight Phase | Cruise |
| Route In Use | Direct |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Air Conditioning and Pressurization Pack |
| Person 1 | |
| Function | Pilot Flying Single Pilot |
| Qualification | Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Engineer |
| Experience | Flight Crew Last 90 Days 50 Flight Crew Total 14800 Flight Crew Type 254 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor |
Narrative:
In cruise at FL180; the temperature in the cabin became very cold suddenly. I increased the selected temperature with the auto temperature control rheostat; and the temperature did not change after several minutes. I then selected manual hot for about three seconds. The temperature coming out of my side duct began to warm. I left the temperature controller in auto after having moved the mix valve to a warmer selection in manual; and monitored the temperature. Several minutes later; the temperature coming out of the duct suddenly rose dramatically; and I could smell a burning smell. I immediately went to manual cold and tried to decrease the temperature; but concurrently the passengers in the back alerted me to smoke in the cabin. I called the center controller and told him I needed lower immediately; and he cleared me to 11;000 feet. The temperature continued to come out hot; so I took the bleed air switches to off; and the cabin began to rapidly climb as I was in a rapid descent from FL180 to 11;000 feet. Once the bleed valves were turned off; there was no more smoke; and no more heat coming from the air ducts. At 11;000 feet; I turned the bleed valves back on one at a time; and cold air came out of the ducts. I was able to control the cabin in this configuration; and we flew the rest of the way with cold air coming from the air ducts. After landing; I passed the information on to our mechanics; and they are investigating the auto temperature control box for the acm (air cycle machine) as the culprit. Center asked if we were declaring an emergency; and we told them we had it under control with the descent to 11;000 feet. They asked if we needed any further assistance; and we told them we did not.
Original NASA ASRS Text
Title: MU-2 Captain experiences very cold conditioned air at FL180. Initial attempts to warm the air are unsuccessful until manual is selected; then the air becomes too hot producing smoke. Attempts to cool the air using manual control are unsuccessful initially; so the bleeds are turned off and the aircraft is descended to 11;000 feet. Flight continues to destination at 11;000 feet.
Narrative: In cruise at FL180; the temperature in the cabin became very cold suddenly. I increased the selected temperature with the auto temperature control rheostat; and the temperature did not change after several minutes. I then selected manual hot for about three seconds. The temperature coming out of my side duct began to warm. I left the temperature controller in auto after having moved the mix valve to a warmer selection in manual; and monitored the temperature. Several minutes later; the temperature coming out of the duct suddenly rose dramatically; and I could smell a burning smell. I immediately went to manual cold and tried to decrease the temperature; but concurrently the passengers in the back alerted me to smoke in the cabin. I called the Center controller and told him I needed lower immediately; and he cleared me to 11;000 feet. The temperature continued to come out hot; so I took the bleed air switches to off; and the cabin began to rapidly climb as I was in a rapid descent from FL180 to 11;000 feet. Once the bleed valves were turned off; there was no more smoke; and no more heat coming from the air ducts. At 11;000 feet; I turned the bleed valves back on one at a time; and cold air came out of the ducts. I was able to control the cabin in this configuration; and we flew the rest of the way with cold air coming from the air ducts. After landing; I passed the information on to our mechanics; and they are investigating the auto temperature control box for the ACM (Air Cycle Machine) as the culprit. Center asked if we were declaring an emergency; and we told them we had it under control with the descent to 11;000 feet. They asked if we needed any further assistance; and we told them we did not.
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.