THE PILOT SAID THAT SHORTLY AFTER TAKEOFF HE ENCOUNTERED MODERATE TO HEAVY ICING CONDITIONS. HE ELECTED TO RETURN TO HIS DEPARTURE APT, AND WAS OBSERVED BY ATC PERSONNEL TO MAKE AN ERRATIC FINAL APPROACH, THEN DROPPING FROM ABOUT 20 FEET AGL TO THE RUNWAY. PILOT WAS ABLE TO TAXI THE ACFT TO THE RAMP WITHOUT FURTHER INCIDENT, BUT POST ACCIDENT INVESTIGATION REVEALED BOTH WING SPARS DAMAGED AND A DAMAGED RIGHT PROPELLER.