|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1201 To 1800|
|Locale Reference||atc facility : tnv|
|Altitude||msl bound lower : 11000|
msl bound upper : 11000
|Controlling Facilities||tower : sna|
|Operator||general aviation : personal|
|Make Model Name||Cessna 340/340A|
|Operating Under FAR Part||Part 91|
|Flight Phase||cruise other|
|Route In Use||enroute airway : v306|
|Function||flight crew : single pilot|
|Qualification||other other : other|
pilot : instrument
pilot : private
|Experience||flight time last 90 days : 15|
flight time total : 1600
flight time type : 700
|Affiliation||government : faa|
|Function||controller : radar|
|Qualification||controller : radar|
|Anomaly||aircraft equipment problem : critical|
other anomaly other
|Independent Detector||aircraft equipment other aircraft equipment : unspecified|
other flight crewa
|Resolutory Action||flight crew : declared emergency|
In level cruise at 11000 ft MSL, strong vibration started after checking out operation of left and right pressure dump levers (noticed cabin pressure differential low, 3 versus 4.2 psig, aircraft just out of annual inspection). Immediately turned aircraft toward destination iws and began troubleshooting problem. Located problem in left engine which when reduced to idle/near idle caused vibration to go away. During troubleshooting, I advised ATC of problem and that I was changing course directly for destination. They asked if I was declaring an emergency and I said 'yes' in order to get ATC to agree to heading change and descent to VMC (9000 ft MSL). Once established at 9000 ft with left engine of idle/near idle, problem was manageable. Landed at iws without incident. Troubleshooting of pressurization problems is probably best left to mechanic on ground. ATC could also be more helpful in first few mins versus asking numerous questions at an extremely busy time and basically 'forcing' pilot to declare an emergency before problem has been assessed. On the ground, the engine problem was determined to be a cylinder not firing on the left side resulting in vibration. The problem was unrelated to pressurization problem which was determined to be the left side pressurization dump valve which was stuck open. Both problems were repaired by authority/authorized repair station, aircraft test flown and placed back in service.
Original NASA ASRS Text
Title: PVT PLT OF A C340 DECLARED AN EMER, AFTER EXPERIENCING A 'ROUGH' RUNNING ENG AND LOW CABIN PRESSURE, DURING IFR CRUISE TO RECEIVE EXPEDITED ATC HANDLING TO DEST IN VFR CONDITIONS.
Narrative: IN LEVEL CRUISE AT 11000 FT MSL, STRONG VIBRATION STARTED AFTER CHKING OUT OP OF L AND R PRESSURE DUMP LEVERS (NOTICED CABIN PRESSURE DIFFERENTIAL LOW, 3 VERSUS 4.2 PSIG, ACFT JUST OUT OF ANNUAL INSPECTION). IMMEDIATELY TURNED ACFT TOWARD DEST IWS AND BEGAN TROUBLESHOOTING PROB. LOCATED PROB IN L ENG WHICH WHEN REDUCED TO IDLE/NEAR IDLE CAUSED VIBRATION TO GO AWAY. DURING TROUBLESHOOTING, I ADVISED ATC OF PROB AND THAT I WAS CHANGING COURSE DIRECTLY FOR DEST. THEY ASKED IF I WAS DECLARING AN EMER AND I SAID 'YES' IN ORDER TO GET ATC TO AGREE TO HEADING CHANGE AND DSCNT TO VMC (9000 FT MSL). ONCE ESTABLISHED AT 9000 FT WITH L ENG OF IDLE/NEAR IDLE, PROB WAS MANAGEABLE. LANDED AT IWS WITHOUT INCIDENT. TROUBLESHOOTING OF PRESSURIZATION PROBS IS PROBABLY BEST LEFT TO MECH ON GND. ATC COULD ALSO BE MORE HELPFUL IN FIRST FEW MINS VERSUS ASKING NUMEROUS QUESTIONS AT AN EXTREMELY BUSY TIME AND BASICALLY 'FORCING' PLT TO DECLARE AN EMER BEFORE PROB HAS BEEN ASSESSED. ON THE GND, THE ENG PROB WAS DETERMINED TO BE A CYLINDER NOT FIRING ON THE L SIDE RESULTING IN VIBRATION. THE PROB WAS UNRELATED TO PRESSURIZATION PROB WHICH WAS DETERMINED TO BE THE L SIDE PRESSURIZATION DUMP VALVE WHICH WAS STUCK OPEN. BOTH PROBS WERE REPAIRED BY AUTH REPAIR STATION, ACFT TEST FLOWN AND PLACED BACK IN SVC.
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.