Piper colt has RPM drop, makes emergency landing at closed airport.

Attributes
ACN	322342
Time
Date	199512
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mcc
State Reference	CA
Altitude	agl bound lower : 0 agl bound upper : 5000
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Piper Single Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 15 flight time total : 500 flight time type : 100
ASRS Report	322342
Events
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 other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Was en route above broken cloud deck, began experiencing RPM drop, seemed progressive and gradual. Full application of carburetor heat did not remedy. Located airport 3 mi behind me per GPS and was able to get down through hole and make successful landing even though the airport is under repair. At pattern altitude I could maintain only 1500 RPM. Aircraft now grounded pending inspection of all engine controls, particularly position of carburetor heat butterfly. Recommend: when checking out in aircraft require 1 hour preflight instruction on specific aircraft with qualified a&P in addition to current practice. Since carburetor heat cable feels secure and tach indicates RPM drop I felt ok to go but actually I have no knowledge of butterfly position in relation to knob position. Maybe put reference mark under arm? Visible during preflight? Callback conversation with reporter revealed the following information: reporter states the aircraft was a PA22 converted to a PA20, a tri pacer to a colt, tail dragger. The problem was the cable for the carburetor heat had slipped and would not open all the way. Only partial carburetor heat was available. There was enough drag on the cable to give a proper indication on the run- up. Problem was attributed to a very sloppy annual in which this loose cable was missed. Reporter suggestion for a marking would have made no difference in detecting this problem.

Original NASA ASRS Text

Title: PIPER COLT HAS RPM DROP, MAKES EMER LNDG AT CLOSED ARPT.

Narrative: WAS ENRTE ABOVE BROKEN CLOUD DECK, BEGAN EXPERIENCING RPM DROP, SEEMED PROGRESSIVE AND GRADUAL. FULL APPLICATION OF CARBURETOR HEAT DID NOT REMEDY. LOCATED ARPT 3 MI BEHIND ME PER GPS AND WAS ABLE TO GET DOWN THROUGH HOLE AND MAKE SUCCESSFUL LNDG EVEN THOUGH THE ARPT IS UNDER REPAIR. AT PATTERN ALT I COULD MAINTAIN ONLY 1500 RPM. ACFT NOW GNDED PENDING INSPECTION OF ALL ENG CTLS, PARTICULARLY POS OF CARB HEAT BUTTERFLY. RECOMMEND: WHEN CHKING OUT IN ACFT REQUIRE 1 HR PREFLT INSTRUCTION ON SPECIFIC ACFT WITH QUALIFIED A&P IN ADDITION TO CURRENT PRACTICE. SINCE CARB HEAT CABLE FEELS SECURE AND TACH INDICATES RPM DROP I FELT OK TO GO BUT ACTUALLY I HAVE NO KNOWLEDGE OF BUTTERFLY POS IN RELATION TO KNOB POS. MAYBE PUT REFERENCE MARK UNDER ARM? VISIBLE DURING PREFLT? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ACFT WAS A PA22 CONVERTED TO A PA20, A TRI PACER TO A COLT, TAIL DRAGGER. THE PROB WAS THE CABLE FOR THE CARB HEAT HAD SLIPPED AND WOULD NOT OPEN ALL THE WAY. ONLY PARTIAL CARB HEAT WAS AVAILABLE. THERE WAS ENOUGH DRAG ON THE CABLE TO GIVE A PROPER INDICATION ON THE RUN- UP. PROB WAS ATTRIBUTED TO A VERY SLOPPY ANNUAL IN WHICH THIS LOOSE CABLE WAS MISSED. RPTR SUGGESTION FOR A MARKING WOULD HAVE MADE NO DIFFERENCE IN DETECTING THIS PROB.

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.