Off field landing due to smoke of unknown origin in cockpit.

Attributes
ACN	108968
Time
Date	198904
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mce
State Reference	CA
Altitude	msl bound lower : 1500 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mer
Operator	other
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other cruise other
Flight Plan	VFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : commercial pilot : military
Experience	flight time last 90 days : 45 flight time total : 1500 flight time type : 50
ASRS Report	108968
Person 2
Affiliation	government : military
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While inbound to merced airport and in communication with castle approach I noticed smoke coming out from under instrument panel. Immediately notified castle and squawked XXXX. I reduced power and the smoke disappeared. When I increased the smoke reappeared. I suspected that the smoke was coming from the engine compartment so I made the decision to land immediately at the best possible place--highway 140, west of cunningham rd. I should have turned off all electrical switches, but did not. After a safe landing we investigated the engine compartment and determined the problem to be a malfunctioning voltage regulator. The wires were disconnected and secured and the aircraft was flown to merced airport. The following day, 4/sun/89, the aircraft was ferried to lgb to be repaired.

Original NASA ASRS Text

Title: OFF FIELD LNDG DUE TO SMOKE OF UNKNOWN ORIGIN IN COCKPIT.

Narrative: WHILE INBND TO MERCED ARPT AND IN COM WITH CASTLE APCH I NOTICED SMOKE COMING OUT FROM UNDER INSTRUMENT PANEL. IMMEDIATELY NOTIFIED CASTLE AND SQUAWKED XXXX. I REDUCED PWR AND THE SMOKE DISAPPEARED. WHEN I INCREASED THE SMOKE REAPPEARED. I SUSPECTED THAT THE SMOKE WAS COMING FROM THE ENG COMPARTMENT SO I MADE THE DECISION TO LAND IMMEDIATELY AT THE BEST POSSIBLE PLACE--HWY 140, W OF CUNNINGHAM RD. I SHOULD HAVE TURNED OFF ALL ELECTRICAL SWITCHES, BUT DID NOT. AFTER A SAFE LNDG WE INVESTIGATED THE ENG COMPARTMENT AND DETERMINED THE PROB TO BE A MALFUNCTIONING VOLTAGE REGULATOR. THE WIRES WERE DISCONNECTED AND SECURED AND THE ACFT WAS FLOWN TO MERCED ARPT. THE FOLLOWING DAY, 4/SUN/89, THE ACFT WAS FERRIED TO LGB TO BE REPAIRED.

Data retrieved from NASA's ASRS site as of August 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.