Narrative:

On the day of the incident; I was teaching a soft field takeoff with my student pilot. As aircraft (C152) lifted off the ground; I noticed the RPM decreasing slightly. After a quick troubleshoot I realized no engine improvement. I continued with the takeoff and lift-off after realizing there was no more runway. At that point my decision was to declare an emergency and maneuver to circle back and return to the runway. I started the maneuver at approximately 400 ft AGL and commenced a hard right turn to avoid the ramp to the north of the runway. My first thought was to bring the aircraft on the grass to the south of the runway. After declaring an emergency; I heard tower deviate a cessna on final to turn to the south to clear the runway. Upon completing the turn; I realized I could make the runway and continued to do so. I made the runway with no injuries or damage. Upon returning to the office; I realized my student and myself failed to inspect the maintenance logbook (squawk book) and the aircraft was written up for quitting during starting the engine. Failure to complete a proper preflight and inspection of documents resulted in the occurrence.

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Original NASA ASRS Text

Title: C152 ENG RPM DECREASED AFTER TKOF. WHEN ENG PERFORMANCE DID NOT IMPROVE; PLT DECLARED AN EMER AND CIRCLED FOR AN EMER LNDG.

Narrative: ON THE DAY OF THE INCIDENT; I WAS TEACHING A SOFT FIELD TKOF WITH MY STUDENT PLT. AS ACFT (C152) LIFTED OFF THE GND; I NOTICED THE RPM DECREASING SLIGHTLY. AFTER A QUICK TROUBLESHOOT I REALIZED NO ENG IMPROVEMENT. I CONTINUED WITH THE TKOF AND LIFT-OFF AFTER REALIZING THERE WAS NO MORE RWY. AT THAT POINT MY DECISION WAS TO DECLARE AN EMER AND MANEUVER TO CIRCLE BACK AND RETURN TO THE RWY. I STARTED THE MANEUVER AT APPROX 400 FT AGL AND COMMENCED A HARD R TURN TO AVOID THE RAMP TO THE N OF THE RWY. MY FIRST THOUGHT WAS TO BRING THE ACFT ON THE GRASS TO THE S OF THE RWY. AFTER DECLARING AN EMER; I HEARD TWR DEVIATE A CESSNA ON FINAL TO TURN TO THE S TO CLR THE RWY. UPON COMPLETING THE TURN; I REALIZED I COULD MAKE THE RWY AND CONTINUED TO DO SO. I MADE THE RWY WITH NO INJURIES OR DAMAGE. UPON RETURNING TO THE OFFICE; I REALIZED MY STUDENT AND MYSELF FAILED TO INSPECT THE MAINT LOGBOOK (SQUAWK BOOK) AND THE ACFT WAS WRITTEN UP FOR QUITTING DURING STARTING THE ENG. FAILURE TO COMPLETE A PROPER PREFLT AND INSPECTION OF DOCUMENTS RESULTED IN THE OCCURRENCE.

Data retrieved from NASA's ASRS site as of January 2009 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.