Narrative:

During a special VFR departure, my airplane developed power troubles. I declared an emergency and started a slow right 360 (my plane had enough power to maintain altitude during a turn). During the turn it was difficult to find the airport (due to the one mi visibility at the airport). I managed to land the plane west/O any problems. Callback conversation with reporter revealed the following information. CFI and student departed vny on an aircraft chkout flight. When it became apparent that aircraft wan't climbing as it should, CFI decided to return to land. Takeoff was made on runway 16R and when flight reached 200' AGL, they executed a 180 degree turn, declared an emergency and landed on runway 34L (opp direction, same runway). Mechanic discovered a collapsed carburetor air inlet hose that was choking off the air flow. Reporter said that he is in the habit of performing full power runups prior to departure, and did so on this flight, but failed to recognize that the aircraft wasn't developing normal power because he saw the static RPM go to approximately 2200. This aircraft, however, has a constant speed propeller, and reporter was mindset on a similar model that had a fixed-pitch propeller. Therefore, he didn't realize that in this aircraft, the RPM during runup should have been higher. Reporter said that FSDO queried FBO about incident, but that there was no further action. Once power problem was evident, CFI took control of the aircraft from the student. Reporter stated that he opted to make a 180 degree turn and landing on the same runway in the opp direction because he was unsure of whether the power situation might continue to worsen, and visibility was so poor that he was concerned about losing sight of the airport.

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Original NASA ASRS Text

Title: CFI AND STUDENT DEP VNY IN SVFR CONDITIONS EXPERIENCE POWER LOSS ON INITIAL CLIMB, DECLARE AN EMERGENCY AND MAKE A 180 DEGREE TURN BACK TO A LNDG. POWER LOSS RESULTED FROM COLLAPSED CARBURATOR INLET TUBE.

Narrative: DURING A SPECIAL VFR DEP, MY AIRPLANE DEVELOPED PWR TROUBLES. I DECLARED AN EMER AND STARTED A SLOW R 360 (MY PLANE HAD ENOUGH PWR TO MAINTAIN ALT DURING A TURN). DURING THE TURN IT WAS DIFFICULT TO FIND THE ARPT (DUE TO THE ONE MI VISIBILITY AT THE ARPT). I MANAGED TO LAND THE PLANE W/O ANY PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. CFI AND STUDENT DEPARTED VNY ON AN ACFT CHKOUT FLT. WHEN IT BECAME APPARENT THAT ACFT WAN'T CLBING AS IT SHOULD, CFI DECIDED TO RETURN TO LAND. TKOF WAS MADE ON RWY 16R AND WHEN FLT REACHED 200' AGL, THEY EXECUTED A 180 DEG TURN, DECLARED AN EMER AND LANDED ON RWY 34L (OPP DIRECTION, SAME RWY). MECH DISCOVERED A COLLAPSED CARBURETOR AIR INLET HOSE THAT WAS CHOKING OFF THE AIR FLOW. RPTR SAID THAT HE IS IN THE HABIT OF PERFORMING FULL PWR RUNUPS PRIOR TO DEP, AND DID SO ON THIS FLT, BUT FAILED TO RECOGNIZE THAT THE ACFT WASN'T DEVELOPING NORMAL PWR BECAUSE HE SAW THE STATIC RPM GO TO APPROX 2200. THIS ACFT, HOWEVER, HAS A CONSTANT SPD PROP, AND RPTR WAS MINDSET ON A SIMILAR MODEL THAT HAD A FIXED-PITCH PROP. THEREFORE, HE DIDN'T REALIZE THAT IN THIS ACFT, THE RPM DURING RUNUP SHOULD HAVE BEEN HIGHER. RPTR SAID THAT FSDO QUERIED FBO ABOUT INCIDENT, BUT THAT THERE WAS NO FURTHER ACTION. ONCE PWR PROB WAS EVIDENT, CFI TOOK CTL OF THE ACFT FROM THE STUDENT. RPTR STATED THAT HE OPTED TO MAKE A 180 DEG TURN AND LNDG ON THE SAME RWY IN THE OPP DIRECTION BECAUSE HE WAS UNSURE OF WHETHER THE PWR SITUATION MIGHT CONTINUE TO WORSEN, AND VISIBILITY WAS SO POOR THAT HE WAS CONCERNED ABOUT LOSING SIGHT OF THE ARPT.

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.