An MU2 freighter on final approach at 2100 ft declared an emergency due to the cockpit filling with ...

Attributes
ACN	420404
Time
Date	199811
Day	Thu
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : cae
State Reference	SC
Altitude	msl bound lower : 2100 msl bound upper : 2100
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : cae tower : atl
Operator	common carrier : air carrier
Make Model Name	Small Transport
Flight Phase	descent : approach other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 2500 flight time type : 120
ASRS Report	420404
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While being vectored for the ILS 11 at cae the cockpit filled with smoke due to a heater system overtemp. As a result of the smoke in the cabin, my altitude was exceeded by approximately 500 ft. No conflict resulted. Environmental system was turned off, cabin pressure released and cabin vented to clear smoke. ATC was advised and rescue trucks were dispatched. The aircraft landed without incident. I feel that an airworthiness directive should be issued on the mitsubishi MU2 heater system, as this malfunction has occurred 3 times in 3 different airplanes that I have flown in (all MU2's). Callback conversation with reporter revealed the following information: the reporter stated the aircraft was an MU2 and this was the reporter's third experience of smoke in the cockpit caused by the air conditioning system. The reporter said the system has a 3 position switch, manual heat, manual cold, and automatic position with a rheostat to control the temperature. The reporter stated with any mode selected the cockpit heat valve moves too slowly to keep up with the aircraft. The reporter said in this incident the valve failed completely and allowed hot bleed air to overheat the ducting causing smoke and fumes to enter the cockpit. The reporter said with a 1-PERSON crew it's a real problem operating the aircraft and continuously monitoring the air conditioning system. The reporter said that after getting the aircraft on the ground and exiting the aircraft through a cockpit window it was necessary to stand by for 15 mins for the smoke and fumes to clear so maintenance could check the aircraft. The reporter said the only warning system is on the master caution system and illuminates the defog/overtemp light which came on long after the cockpit filled with smoke and fumes. The reporter said it's possible to make a setting for taxi out at low engine power with the valve open and then go to high engine power for takeoff and climb and overheat the ducting because of the high bleed air temperature now coming from the engine and the slow movement of the cockpit heat valve to modulate toward close.

Original NASA ASRS Text

Title: AN MU2 FREIGHTER ON FINAL APCH AT 2100 FT DECLARED AN EMER DUE TO THE COCKPIT FILLING WITH SMOKE AND FUMES CAUSED BY A FAILED COCKPIT HEAT VALVE.

Narrative: WHILE BEING VECTORED FOR THE ILS 11 AT CAE THE COCKPIT FILLED WITH SMOKE DUE TO A HEATER SYS OVERTEMP. AS A RESULT OF THE SMOKE IN THE CABIN, MY ALT WAS EXCEEDED BY APPROX 500 FT. NO CONFLICT RESULTED. ENVIRONMENTAL SYS WAS TURNED OFF, CABIN PRESSURE RELEASED AND CABIN VENTED TO CLR SMOKE. ATC WAS ADVISED AND RESCUE TRUCKS WERE DISPATCHED. THE ACFT LANDED WITHOUT INCIDENT. I FEEL THAT AN AIRWORTHINESS DIRECTIVE SHOULD BE ISSUED ON THE MITSUBISHI MU2 HEATER SYS, AS THIS MALFUNCTION HAS OCCURRED 3 TIMES IN 3 DIFFERENT AIRPLANES THAT I HAVE FLOWN IN (ALL MU2'S). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS AN MU2 AND THIS WAS THE RPTR'S THIRD EXPERIENCE OF SMOKE IN THE COCKPIT CAUSED BY THE AIR CONDITIONING SYS. THE RPTR SAID THE SYS HAS A 3 POS SWITCH, MANUAL HEAT, MANUAL COLD, AND AUTO POS WITH A RHEOSTAT TO CTL THE TEMP. THE RPTR STATED WITH ANY MODE SELECTED THE COCKPIT HEAT VALVE MOVES TOO SLOWLY TO KEEP UP WITH THE ACFT. THE RPTR SAID IN THIS INCIDENT THE VALVE FAILED COMPLETELY AND ALLOWED HOT BLEED AIR TO OVERHEAT THE DUCTING CAUSING SMOKE AND FUMES TO ENTER THE COCKPIT. THE RPTR SAID WITH A 1-PERSON CREW IT'S A REAL PROB OPERATING THE ACFT AND CONTINUOUSLY MONITORING THE AIR CONDITIONING SYS. THE RPTR SAID THAT AFTER GETTING THE ACFT ON THE GND AND EXITING THE ACFT THROUGH A COCKPIT WINDOW IT WAS NECESSARY TO STAND BY FOR 15 MINS FOR THE SMOKE AND FUMES TO CLR SO MAINT COULD CHK THE ACFT. THE RPTR SAID THE ONLY WARNING SYS IS ON THE MASTER CAUTION SYS AND ILLUMINATES THE DEFOG/OVERTEMP LIGHT WHICH CAME ON LONG AFTER THE COCKPIT FILLED WITH SMOKE AND FUMES. THE RPTR SAID IT'S POSSIBLE TO MAKE A SETTING FOR TAXI OUT AT LOW ENG PWR WITH THE VALVE OPEN AND THEN GO TO HIGH ENG PWR FOR TKOF AND CLB AND OVERHEAT THE DUCTING BECAUSE OF THE HIGH BLEED AIR TEMP NOW COMING FROM THE ENG AND THE SLOW MOVEMENT OF THE COCKPIT HEAT VALVE TO MODULATE TOWARD CLOSE.

Data retrieved from NASA's ASRS site as of July 2007 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.

An MU2 freighter on final approach at 2100 ft declared an emergency due to the cockpit filling with smoke and fumes caused by a failed cockpit heat valve.