Snow and ice caused engine problems.

Attributes
ACN	290410
Time
Date	199412
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : otz
State Reference	AK
Altitude	msl bound lower : 900 msl bound upper : 900
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	cruise other other other
Flight Plan	VFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 270 flight time total : 2300 flight time type : 800
ASRS Report	290410
Person 2
Affiliation	Other
Function	other personnel
Qualification	other other : other
Events
Anomaly	inflight encounter : weather other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Weather

Narrative:

On a scheduled flight from otz to kiana the throttle became stuck at 21 inches hg. I elected to return to otz where the runway is much longer and in better shape. Upon reaching otz, the visibility had decreased to 3/4 of a mi. I declared an emergency and proceeded into the class east surface area. On downwind leg for runway 8, I managed to bring the power back to 19 inches, and then on base leg, the throttle became free. I landed without incident. Once on the runway, I attempted to taxi but was unable due to engine roughness. I shut the engine down and had the airplane towed back to the ramp. Upon inspection of the engine, the mechanic found an unusually high amount of snow in the air filter, which was the cause of the engine roughness. During the flight the WX en route was 1 to 3 mi in snow. Since the temperatures were in the 20's, I believe that the snow was blown through to the air intake. While going to the intake it melted to water and froze to the firewall, and in turn froze the throttle cable in place. Since the snow was very wet, it managed to clog the air intake.

Original NASA ASRS Text

Title: SNOW AND ICE CAUSED ENG PROBS.

Narrative: ON A SCHEDULED FLT FROM OTZ TO KIANA THE THROTTLE BECAME STUCK AT 21 INCHES HG. I ELECTED TO RETURN TO OTZ WHERE THE RWY IS MUCH LONGER AND IN BETTER SHAPE. UPON REACHING OTZ, THE VISIBILITY HAD DECREASED TO 3/4 OF A MI. I DECLARED AN EMER AND PROCEEDED INTO THE CLASS E SURFACE AREA. ON DOWNWIND LEG FOR RWY 8, I MANAGED TO BRING THE PWR BACK TO 19 INCHES, AND THEN ON BASE LEG, THE THROTTLE BECAME FREE. I LANDED WITHOUT INCIDENT. ONCE ON THE RWY, I ATTEMPTED TO TAXI BUT WAS UNABLE DUE TO ENG ROUGHNESS. I SHUT THE ENG DOWN AND HAD THE AIRPLANE TOWED BACK TO THE RAMP. UPON INSPECTION OF THE ENG, THE MECH FOUND AN UNUSUALLY HIGH AMOUNT OF SNOW IN THE AIR FILTER, WHICH WAS THE CAUSE OF THE ENG ROUGHNESS. DURING THE FLT THE WX ENRTE WAS 1 TO 3 MI IN SNOW. SINCE THE TEMPS WERE IN THE 20'S, I BELIEVE THAT THE SNOW WAS BLOWN THROUGH TO THE AIR INTAKE. WHILE GOING TO THE INTAKE IT MELTED TO WATER AND FROZE TO THE FIREWALL, AND IN TURN FROZE THE THROTTLE CABLE IN PLACE. SINCE THE SNOW WAS VERY WET, IT MANAGED TO CLOG THE AIR INTAKE.

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.