INSTRUCTOR WITH PVT PLT RECEIVING TAILWHEEL ENDORSEMENT PRACTICING TOUCH AND GOES; GARS AND SLIPS HAVE ENG PROB AFTER TKOF. PWR IS INTERMITTENT; THEN DECREASES ALTOGETHER. EMER LNDG MADE.

Narrative

ON 13TH APCH TO LNDG; PRACTICING SLIPS AND XWIND LNDGS AND GARS FOR PVT PLT EARNING TAIL DRAGGER ENDORSEMENT. AFTER TOUCHDOWN SIMULATED GAR. AT 300 FT; A SMOOTH DECREASE IN PWR OCCURRED; THEN PWR RETURNED. BASED ON PAST EXPERIENCE; I AT FIRST THOUGHT THIS WAS DUE TO UNPORTING THE FUEL LINE IN THE WING TANK DURING THE SLIP AND EXPECTED THE PWR TO RETURN TO NORMAL. THE PWR DID COME BACK FOR A FEW SECONDS; BUT THEN DECREASED AND BEGAN FLUCTUATING UP AND DOWN. WE WERE ABLE TO CLB OR LEVELOFF DURING THE PWR INCREASES; BUT WERE IN A SLOW DSCNT TREND. I CHKED MIXTURE RICH; CARB HEAT ON; AND ADJUSTED THE THROTTLE TO NO AVAIL. I OPTED NOT TO CHANGE TANKS DUE TO THE LOW ALT AND AIRSPD (BEST GLIDE); AND OBSTACLES (PWR LINES; TREES; DITCHES AND HOUSES ON ALL SIDES). REACHED A POS WHERE WE COULD MAKE A SMALL WHEAT FIELD; MADE A STEEP BANK TO R TO SET UP FOR A SHORT BASE TO BURN UP EXCESS ALT; THEN IMMEDIATELY BANKED L AND APPLIED FULL RUDDER TO FORWARD SLIP TO A LNDG. TOUCHED DOWN TAILWHEEL FIRST WITH MAINS FOLLOWING LIGHTLY (3 POINT ATTITUDE). HELD YOKE ALL THE WAY BACK TO KEEP FROM FLIPPING. ACFT; INSTRUCTOR AND STUDENT ALL UNHARMED. ACFT GONE TO SHOP TO DETERMINE CAUSE OF PWR LOSS.