In-flight engine problem, loss of RPM. Vectors to landing.

Attributes
ACN	89339
Time
Date	198806
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : leb
State Reference	NH
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Route In Use	enroute airway : zbw
Flight Plan	IFR
Person 1
Affiliation	Other
Function	instruction : instructor
Qualification	pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 150 flight time total : 1300 flight time type : 300
ASRS Report	89339
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While en route from ash-rut a power loss of 100-200 RPM occurred. Carburetor heat was applied but did not indicate ice build up. Engine surged +100-200 RPM then dropped again. After 2-3 occurrences within 2 mins, power dropped approximately 400 RPM. At my direction student asked for and received vectors for leb. Altitude was plentiful and we stayed high in the pattern. We brought the aircraft to the local FBO where the mechanic checked the plugs for fouling and gap, checked compression, fuel contamination, etc. Mechanic found sufficient fouling of the plugs to precipitate the power loss. We departed and had no further problems. Temperature and humidity were high and full power (and full rich mixture) was held for an extended period before reaching altitude. Perhaps if mixture were leaned somewhat during the climb, the fouling would not have been as bad. Student and CFI were collected throughout the ordeal.

Original NASA ASRS Text

Title: INFLT ENGINE PROBLEM, LOSS OF RPM. VECTORS TO LNDG.

Narrative: WHILE ENRTE FROM ASH-RUT A PWR LOSS OF 100-200 RPM OCCURRED. CARB HEAT WAS APPLIED BUT DID NOT INDICATE ICE BUILD UP. ENG SURGED +100-200 RPM THEN DROPPED AGAIN. AFTER 2-3 OCCURRENCES WITHIN 2 MINS, PWR DROPPED APPROX 400 RPM. AT MY DIRECTION STUDENT ASKED FOR AND RECEIVED VECTORS FOR LEB. ALT WAS PLENTIFUL AND WE STAYED HIGH IN THE PATTERN. WE BROUGHT THE ACFT TO THE LCL FBO WHERE THE MECH CHKED THE PLUGS FOR FOULING AND GAP, CHKED COMPRESSION, FUEL CONTAMINATION, ETC. MECH FOUND SUFFICIENT FOULING OF THE PLUGS TO PRECIPITATE THE PWR LOSS. WE DEPARTED AND HAD NO FURTHER PROBS. TEMP AND HUMIDITY WERE HIGH AND FULL PWR (AND FULL RICH MIXTURE) WAS HELD FOR AN EXTENDED PERIOD BEFORE REACHING ALT. PERHAPS IF MIXTURE WERE LEANED SOMEWHAT DURING THE CLB, THE FOULING WOULD NOT HAVE BEEN AS BAD. STUDENT AND CFI WERE COLLECTED THROUGHOUT THE ORDEAL.

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.