An accident that could mean the end of Frenchman Didier Pironi's racing career cast a shadow over today's final practice for the West German Grand Prix motor race.

Pironi, who leads the world championship standings and would have had the pole position on the starting grid, was flown to a Heidelberg hospital with compound fractures of both legs and a broken left arm, race organizers said. Doctors were still not sure they could save his shattered lower right leg.

His Ferrari ran into the rear wheel of Alain Prost's Renault in pelting rain, went into the air and flipped over three times to finish with its front completely crushed.

Trackside marshals estimated Pironi was going 150 mph when he hit Prost's slowly driven auto, which had just been passed by Derek Daly.

Rescue workers took 30 minutes to cut Pironi free from the wreck and a helicopter immediately flew him to Heidelberg's university clinic, where he underwent surgery for five hours. Doctors said later they were waiting to see whether blood was reaching his lower right leg before deciding whether to amputate.

The accident gave Prost the pole position for Sunday's race.

Two other Grand Prix drivers, Gilles Villeneuve and Riccardo Palletti, have died in racing accidents earlier this year. And two weeks ago at the French Grand Prix, Jochen Mass' March spun into the crowd and injured 12 people; Mass suffered injuries that prevented him from driving in Hockenheim.