Pilot of an small aircraft sel descended below assigned altitude due to partial loss of power. Suspe...

Attributes
ACN	304106
Time
Date	199505
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mol
State Reference	VA
Altitude	msl bound lower : 6000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute airway : v143
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 75 flight time total : 1100 flight time type : 1050
ASRS Report	304106
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

While flying south on V143 on an IFR flight from W54 in maryland to bna, nashville, tn, cruising at 8000 ft in a C172 with a 0360a4m engine a small loss of power was noticed and I was unable to hold altitude dropping 300 ft in a min. ATC was informed and carburetor heat was applied. I was cleared to 6000 ft which I descended to with the carburetor heat on and full power. The engine cleared and I ascended back to 8000 ft with no further problems. The engine never ran rough with just a small loss of power of about 350 RPM noticed from an indicated 2500 RPM to about 2250 RPM. I have never experienced this problem in this aircraft which I have owned for several yrs. The engine has been in the aircraft since new for 500 hours and 4 yrs. I was not sure what was occurring with the engine and just went through a normal engine out checklist, 'fuel both, mixture full, carburetor heat on, mags both, primer in' and problem cleared. Well rested at time of incident. Left engine at full power because a speaker advised at a seminar several months ago that carburetor ice clears quicker at full throttle. Temperature 31 degrees F cruising just 500 ft above a broken cloud layer.

Original NASA ASRS Text

Title: PLT OF AN SMA SEL DSNDED BELOW ASSIGNED ALT DUE TO PARTIAL LOSS OF PWR. SUSPECT CARB ICE.

Narrative: WHILE FLYING S ON V143 ON AN IFR FLT FROM W54 IN MARYLAND TO BNA, NASHVILLE, TN, CRUISING AT 8000 FT IN A C172 WITH A 0360A4M ENG A SMALL LOSS OF PWR WAS NOTICED AND I WAS UNABLE TO HOLD ALT DROPPING 300 FT IN A MIN. ATC WAS INFORMED AND CARB HEAT WAS APPLIED. I WAS CLRED TO 6000 FT WHICH I DSNDED TO WITH THE CARB HEAT ON AND FULL PWR. THE ENG CLRED AND I ASCENDED BACK TO 8000 FT WITH NO FURTHER PROBS. THE ENG NEVER RAN ROUGH WITH JUST A SMALL LOSS OF PWR OF ABOUT 350 RPM NOTICED FROM AN INDICATED 2500 RPM TO ABOUT 2250 RPM. I HAVE NEVER EXPERIENCED THIS PROB IN THIS ACFT WHICH I HAVE OWNED FOR SEVERAL YRS. THE ENG HAS BEEN IN THE ACFT SINCE NEW FOR 500 HRS AND 4 YRS. I WAS NOT SURE WHAT WAS OCCURRING WITH THE ENG AND JUST WENT THROUGH A NORMAL ENG OUT CHKLIST, 'FUEL BOTH, MIXTURE FULL, CARB HEAT ON, MAGS BOTH, PRIMER IN' AND PROB CLRED. WELL RESTED AT TIME OF INCIDENT. L ENG AT FULL PWR BECAUSE A SPEAKER ADVISED AT A SEMINAR SEVERAL MONTHS AGO THAT CARB ICE CLRS QUICKER AT FULL THROTTLE. TEMP 31 DEGS F CRUISING JUST 500 FT ABOVE A BROKEN CLOUD LAYER.

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.

Pilot of an small aircraft sel descended below assigned altitude due to partial loss of power. Suspect carburetor ice.