The folks at NASA would like to clarify that their $250,000 Personal Air Vehicle (PAV) Centennial Challenge is seeking out practical ideas for improving personal, on-demand air transportation, and the common concept of a vehicle that transforms from airplane to car is not necessarily the answer to that challenge. "The goal of the PAV Centennial Challenge is to develop affordable, efficient and safe PAVs that are able to quietly land at very small airports that are close-in to small communities, saving time spent on ground transportation and making flying more accessible to people across America," the Comparative Aircraft Flight Efficiency (CAFE) Foundation says at its Web site, which has many more details about the challenge. The CAFE Foundation is working with NASA to administer and execute the competition. "NASA and CAFE engineers have designed the contest rules to fairly reward PAVs that are affordable, safe, quiet, fast, easy to use and efficient in near all-weather, door-to-door travel. To win, a team vehicle must demonstrate its performance in all these areas -- by flying a 'decathlon-like' array of tasks," the CAFE Foundation said.