Narrative:

The cause of engine power loss was, I believe improper use of carburetor heat. Although I followed the checklist for the C-150, application of carburetor heat at the start of my descent may have prevented sudden power loss. The checklist said to turn on carburetor heat prior to 'closing the throttle.' it should read, prior to 'reducing throttle' for descent. On nov/xx/94, I was on a VFR flight from birmingham, al, to enterprise, al, with a planned refueling stop at troy, al, at approximately XA00 hours and 10 mi north of troy airport, I contacted troy tower for landing instructions. Troy tower told me to establish a left base for runway 07. I began my descent by reducing power from 2500 RPM to 2200 RPM (RPM remained in the green arc) and increased my airspeed by reducing pitch to 115 mph (still in the green on airspeed). As I began to level off for traffic pattern altitude (1900 ft MSL), the engine suddenly 'coughed' and shook. I noticed a drop in RPM so I applied carburetor heat. The engine seemed to run rougher so I closed the carburetor heat and turned to the left and headed straight for the airport end lined up with runway 14. I called the tower and declared an emergency and told them that I was losing engine power. I said that I wanted to land on runway 14. The tower again told me to land on runway 7. I did not want to continue to runway 7 since it was several mi away. I expected the tower to tell all other aircraft, including the one landing on runway 07, to stay clear so that I could land on runway 14. At this point, I was faced with 2 major concerns: 1) if I continued to runway 14, would I cause an accident with aircraft landing and taking off of the active runway 07? 2) if the engine continued to lose power, would I crash into the dense forest between me and runway 14? The only suitable landing area between me and runway 14 was a large open field. I decided to land in the field while I had engine power and ensure that I would not cause an accident with landing or departing traffic. I informed tower that I was landing approximately 2 mi northwest of runway 14 in an open field. Once landing was assured, I closed the throttle, turned off the magnetos, made one last call, and turned off the master switch (magnetos and master switch were turned off as precaution against post crash fire). I made an excellent landing to level ground and stopped with no injury or damage to the plane. I turned power back on and informed tower that everything was ok. They dispatched police and fire units to the scene. I made a full police report and both police and fire units left as soon as they saw that there was no damage or injury. I called the owner and told him what happened. He arrived at dusk and determined that I had between 30-40 min of fuel remaining in the tanks. He suspected carburetor ice. He flew the plane out of the field the following morning and returned to home base without incident.

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Original NASA ASRS Text

Title: TOI TWR DISREGARDED A PLT'S REQUEST TO LAND IN AN EMER CONDITION CAUSING THE PLT TO THINK THAT HE HAD TO LAND OFF ARPT.

Narrative: THE CAUSE OF ENG PWR LOSS WAS, I BELIEVE IMPROPER USE OF CARB HEAT. ALTHOUGH I FOLLOWED THE CHKLIST FOR THE C-150, APPLICATION OF CARB HEAT AT THE START OF MY DSCNT MAY HAVE PREVENTED SUDDEN PWR LOSS. THE CHKLIST SAID TO TURN ON CARB HEAT PRIOR TO 'CLOSING THE THROTTLE.' IT SHOULD READ, PRIOR TO 'REDUCING THROTTLE' FOR DSCNT. ON NOV/XX/94, I WAS ON A VFR FLT FROM BIRMINGHAM, AL, TO ENTERPRISE, AL, WITH A PLANNED REFUELING STOP AT TROY, AL, AT APPROX XA00 HRS AND 10 MI N OF TROY ARPT, I CONTACTED TROY TWR FOR LNDG INSTRUCTIONS. TROY TWR TOLD ME TO ESTABLISH A L BASE FOR RWY 07. I BEGAN MY DSCNT BY REDUCING PWR FROM 2500 RPM TO 2200 RPM (RPM REMAINED IN THE GREEN ARC) AND INCREASED MY AIRSPD BY REDUCING PITCH TO 115 MPH (STILL IN THE GREEN ON AIRSPD). AS I BEGAN TO LEVEL OFF FOR TFC PATTERN ALT (1900 FT MSL), THE ENG SUDDENLY 'COUGHED' AND SHOOK. I NOTICED A DROP IN RPM SO I APPLIED CARB HEAT. THE ENG SEEMED TO RUN ROUGHER SO I CLOSED THE CARB HEAT AND TURNED TO THE L AND HEADED STRAIGHT FOR THE ARPT END LINED UP WITH RWY 14. I CALLED THE TWR AND DECLARED AN EMER AND TOLD THEM THAT I WAS LOSING ENG PWR. I SAID THAT I WANTED TO LAND ON RWY 14. THE TWR AGAIN TOLD ME TO LAND ON RWY 7. I DID NOT WANT TO CONTINUE TO RWY 7 SINCE IT WAS SEVERAL MI AWAY. I EXPECTED THE TWR TO TELL ALL OTHER ACFT, INCLUDING THE ONE LNDG ON RWY 07, TO STAY CLR SO THAT I COULD LAND ON RWY 14. AT THIS POINT, I WAS FACED WITH 2 MAJOR CONCERNS: 1) IF I CONTINUED TO RWY 14, WOULD I CAUSE AN ACCIDENT WITH ACFT LNDG AND TAKING OFF OF THE ACTIVE RWY 07? 2) IF THE ENG CONTINUED TO LOSE PWR, WOULD I CRASH INTO THE DENSE FOREST BTWN ME AND RWY 14? THE ONLY SUITABLE LNDG AREA BTWN ME AND RWY 14 WAS A LARGE OPEN FIELD. I DECIDED TO LAND IN THE FIELD WHILE I HAD ENG PWR AND ENSURE THAT I WOULD NOT CAUSE AN ACCIDENT WITH LNDG OR DEPARTING TFC. I INFORMED TWR THAT I WAS LNDG APPROX 2 MI NW OF RWY 14 IN AN OPEN FIELD. ONCE LNDG WAS ASSURED, I CLOSED THE THROTTLE, TURNED OFF THE MAGNETOS, MADE ONE LAST CALL, AND TURNED OFF THE MASTER SWITCH (MAGNETOS AND MASTER SWITCH WERE TURNED OFF AS PRECAUTION AGAINST POST CRASH FIRE). I MADE AN EXCELLENT LNDG TO LEVEL GND AND STOPPED WITH NO INJURY OR DAMAGE TO THE PLANE. I TURNED PWR BACK ON AND INFORMED TWR THAT EVERYTHING WAS OK. THEY DISPATCHED POLICE AND FIRE UNITS TO THE SCENE. I MADE A FULL POLICE RPT AND BOTH POLICE AND FIRE UNITS LEFT AS SOON AS THEY SAW THAT THERE WAS NO DAMAGE OR INJURY. I CALLED THE OWNER AND TOLD HIM WHAT HAPPENED. HE ARRIVED AT DUSK AND DETERMINED THAT I HAD BTWN 30-40 MIN OF FUEL REMAINING IN THE TANKS. HE SUSPECTED CARB ICE. HE FLEW THE PLANE OUT OF THE FIELD THE FOLLOWING MORNING AND RETURNED TO HOME BASE WITHOUT INCIDENT.

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.