On June 23, 2006, about 1420 eastern daylight time, a Piper PA-25-235, N7788Z, registered to and operated by Aerial Banners, Inc., crashed shortly after takeoff from Opa-Locka Airport, Opa-Locka, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 local, banner tow flight from Opa-Locka Airport. The airplane was substantially damaged by impact and a post crash fire, and the commercial-rated pilot, the sole occupant, was seriously injured. The flight was originating at the time of the accident. The pilot stated that the preflight was normal with no anomalies noted. The accident flight was his second flight of the day in the accident airplane. The first flight consisted of a banner flight and after returning, the banner was dropped, the airplane was landed then fueled. The pilot started the engine and taxied to the "Gulf" intersection of runway 12, and was cleared for takeoff. After takeoff he initiated a steep right turn to line up with runway 9R, which was normal for the banner operations. About halfway into the right turn, the right wing dropped. He recognized that the airspeed was low, and the airplane had stalled and entered a spin. He attempted to recover from the spin and when the flight was approximately 60 feet above ground level, he had stopped the spin and had recovered to a wings level attitude but the airspeed was low. Before ground contact he applied aft elevator input and the airplane impacted the ground hard while in a slight nose-up attitude. Flames engulfed the cockpit immediately after impact and after the airplane came to rest, he exited the airplane and rolled on the ground to extinguish himself. The pilot further stated there was no preimpact failure or malfunction of the airplane or its systems. A witness located on the airport stated to an FAA inspector that after takeoff the airplane started to make a right turn and stalled at about 100 feet, then impacted the ground. Before impact, he said that the airplane's propeller seemed to be at a coasting rpm speed. Post accident examination of the airplane at the accident site by NTSB revealed no evidence of preimpact failure or malfunction of the primary flight control cables, or pitch trim cable. The manual pitch trim position could not be determined; the flaps were retracted. The airplane was recovered for further examination. The engine was examined at the operator's facility with NTSB and FAA oversight. Extensive heat damage to the engine, magnetos, ignition harness, carburetor, and engine-driven fuel pump precluded an engine run or operational testing of the controls. The crankshaft flange was fractured in several locations and the propeller was separated from the engine. The remaining section of the crankshaft flange had forward and aft bending. Rotation of the crankshaft by hand revealed crankshaft, camshaft, and valve train continuity; suction and compression was noted in each cylinder during crankshaft rotation. Examination of the heat damaged engine-driven fuel pump revealed the bottom cover was partially consumed by the postcrash fire. Following removal of the bottom cover, one of the internal valves was noted to be out of position, and the other valve was loose. The housing where the valves were installed exhibited evidence of 4 "stake" marks for each valve. Further disassembly of the engine-driven fuel pump revealed that the diaphragm was destroyed by the post crash fire. Visual examination of the spark plugs revealed the No. 2 top and bottom plugs exhibited white discoloration of the center electrode. Bench testing of all spark plugs at 80 psi revealed all except the No. 2 bottom plug tested satisfactorily. Examination of the propeller revealed five of the six steel flange bushings were fractured; no evidence of preimpact failure or malfunction was noted. Both propeller blades were bent aft and the leading edges of both were twisted towards low pitch. One blade was bent aft approximately 20 degrees and exhibited heavy chordwise scratches and gouges on the leading edge, while the other blade was bent aft approximately 45 degrees with the tip of the blade separated and not located. Review of the airplane maintenance records revealed the airplane was last inspected in accordance with an annual inspection on April 3, 2006. At the time of the accident the airplane had accumulated approximately 1094 total time hours and about 40 hours since the last annual inspection.