CHI83LU011

The plt reported that after taking off, he stayed low over farm fields. He reported that he traveled about 1 1/4 mi from the arpt & decided to return & land. However, during a left turn, the ultralight vehicle crashed. The plt was seriously injured & did not remember details of the accident after regaining consciousness. A ground witness reported the ultralight was flying slow when the nose pitched down & it entered a spiral & hit the ground. The plt stated that he began the turn while at aprx 75 to 100 ft AGL & was increasing power when the right wing came up & the nose dropped. An exam of the flt controls showed continuity thru-out the sys. An inspection of the eng revealed the urethane hose was pinched & melted at a location between the eng case & the pulsating fuel pump. A further investigation revealed that on a 50 deg day, the temp in that area would be aprx 175 to 200 deg & that the hose would collapse & become seated together at 200 deg. The temperature on the day of the accident was 98 deg.