On December 31, 2006, about 1100 Pacific standard time, a Cessna 150J, N50814, collided with terrain at Gillespie Field, San Diego, California. Banner Joe was operating the airplane under the provisions of 14 CFR Part 91. The commercial pilot was killed. The airplane was substantially damaged. The local banner tow flight departed Gillespie about 5 minutes prior to the accident. Visual meteorological conditions prevailed, and no flight plan had been filed. A Federal Aviation Administration (FAA) inspector interviewed the owner of the company who described a normal banner pickup procedure. Company personnel lay out the banner for pickup on the north side of runway 27R between the runway and the north ramp. The towline is strung between two 10-foot-tall poles, and the banner is laid out to the west of the poles. The towing airplane takes off with 40 feet of towline and a grapple hook. The line is secured to the left horizontal stabilizer and the left wing strut by tape. The remaining line and the hook is secured in the cabin. After takeoff, the pilot throws out the hook and towline. The tape breaks away and the line and hook trail behind the airplane. The pilot flies over the banner pickup location, and an assistant on the ground verifies the proper deployment of the towline and hook. The towing airplane makes another circuit of the traffic pattern, and approaches the banner by flying parallel to runway 27R at 20 feet above ground level (agl). The pilot makes the approach to the banner with partial engine power at 55 to 60 mph, with 10-20 degrees of flap extension, and the grapple hook trailing behind on approximately 40 feet of towline. Just before the airplane reaches the pickup poles, the pilot is supposed to apply full power, and pitch the nose of the airplane up approximately 45 degrees. This maneuver will swing the hook into the towline strung between the pickup poles. The airplane will continue to climb at approximately 45 degrees, "peeling" the banner off the ground. The pilot is to then level out at approximately 200 feet agl. The flaps stay at 10-20 degrees, and the banner is towed between 55 and 60 mph the entire flight. At the time of the accident, the owner was at the banner pickup poles. He stated that the airplane approached the poles at the correct altitude, but it appeared to be flying at a slower than normal pickup speed. The flaps were extended as prescribed. The owner reported that as the airplane reached the pickup poles, he did not hear an increase to the engine noise and the airplane did not pitch up enough initially to capture the towline, but it did pitch to the correct 45-degree angle seconds after the miss. The engine power did not increase, and the airplane continued to climb until it rolled over to the left and into the ground. Another witness, a certified flight instructor who had observed many banner pickups, stated that the airplane approached the towline at the usual low cruise power setting. It did not hook up with the banner, but the nose of the airplane pitched up steeply as usual. He did not hear the usual engine roar; the power setting appeared to remain the same as the approach. The airplane continued climbing in a steep nose up pitch attitude to approximately 400 feet agl, and the airspeed appeared to bleed off. The wings remained level as the nose pitched forward. The airplane's pitch attitude leveled off momentarily, and the airspeed was very low. The engine sounds remained the same throughout the maneuver. He thought that the airplane stalled, and then it went extremely nose down and turned left. He said that it entered a spin, and made 1 3/4 turns before the airplane collided with the runway surface. He did not see anything fall off the airplane, and thought that the airplane operated normally throughout the maneuver. The FAA indicated that the 30-year-old commercial pilot had about 1,200 hours total time. Banner towing training and actual banner towing accounted for 21.8 hours, with eight banner towing flights, solo and dual. During the airframe examination, it was noted that the airplane had been modified with a Cessna tow release mechanism, the installation of a Lycoming O-360 engine, and an 18-gallon auxiliary fuel tank. It also had a wing leading edge cuff, long range fuel tanks, and Madras Air Service "Super Tips." Control continuity was established throughout the airplane. The flap actuator was measured at 4 inches, equating to a 20-degree flap extension position. The elevator trim tab actuator's extension measured 1.125 inches, which equated to a 5-degree down trim tab position. The engine examination revealed no evidence of preimpact catastrophic mechanical malfunction or fire. The crankshaft was manually rotated and gear and valve train continuity was established. Each cylinder displayed "thumb compression." The spark plug electrodes displayed coloration consistent with normal operation. A borescope examination of the cylinders was unremarkable. The engine driven fuel pump was disassembled and no discrepancies or contaminates were noted. All engine fuel lines were in place and secure. Engine control cables were compromised in the impact. The magnetos produced a spark on all leads. The crankshaft separated aft of the propeller flange. The spinner exhibited aft crush and rotational scoring. One propeller blade displayed deep and extensive chordwise scratches, leading edge damage, and twisted. The second propeller blade was bent aft approximately 5 degrees in a large radius bend starting about 15 inches from the hub. The separation surfaces on the crankshaft displayed signatures consistent with ductile overload (45-degree sheer lips and no beach marking).