The 1991 United States Grand Prix (formally the XXVIII Iceberg United States Grand Prix) motor was a Formula One race held on March 10, 1991, in Phoenix, Arizona. It was the first round of the 1991 Formula One season. The 81-lap race was won by McLaren driver Ayrton Senna after he started from pole position. Alain Prost finished in second for the Ferrari team with Benetton driver Nelson Piquet third. It was also the first Formula One race for the future double World Champion, Mika Häkkinen.
The race was the first of the 1991 Formula One season. In the two previous years, the championship had been decided when Senna and Prost tangled at Suzuka. In 1989, their collision as team-mates secured Prost's third World Championship; in 1990, with Prost driving for Ferrari and still in title contention, it handed Senna his second crown. Controversy regarding the nature of the 1990 incident had created great anticipation for the rematch.
Prior to arriving in Phoenix, the 1991 McLaren chassis had had only had one brief test session, and the two race cars were completed about 4 am Friday, six hours before the first practice session. Working to prepare the new car, Ayrton Senna claimed he had never gotten totally comfortable with the increasing complexity of the sport since helping Lotus introduce the first active suspension car in 1987, and he still found it hard to embrace the huge role of computers in achieving a proper setup. "Friday, to understand and interpret things properly, I worked with the engineers into the evening," Senna said. "It has been a long time since I did that. The engineers and I talked our way around the circuit, then we compared this with what the computer predicted. It was great because the computer confirmed almost everything, and it also showed where there was room for improvement."
The Ferraris of Alain Prost and Jean Alesi were expected to be the strongest team, but their V-12s and 7-speed semi-automatic gearboxes were not well suited to the tight turns and short straights of the street circuit. As it turned out, they were not the only ones plagued by gearbox problems throughout the race.
On Sunday, Prost began his second season at Ferrari alongside Senna on the front row. At the start, he fell in behind the Brazilian, with Nigel Mansell slipping ahead of Riccardo Patrese. Alesi and Gerhard Berger followed, then Nelson Piquet, Roberto Moreno, Stefano Modena and Emanuele Pirro. A lap later, Alesi, in his first race for Ferrari, swept past Patrese, but by then Senna was pulling away. After ten laps, he had a lead of ten seconds over Prost.
Behind Senna, Patrese was involved in two successive three-way battles. First, after getting back by Alesi for fourth on lap 16, Patrese closed on Mansell who was immediately behind Prost. By lap 22, Patrese was close enough to attack his Williams team-mate but overshot onto the escape road, as Mansell swerved to avoid him. Upon rejoining, Patrese quickly latched onto Alesi and Berger, as the new three-car train now covered fourth through sixth places. Patrese had gotten past Berger when, suddenly, two of the top six runners retired on consecutive laps. On lap 35, Mansell pulled over when the Williams's new semi-automatic gearbox failed, and on the next time around, Berger's race ended as well.
Patrese passed Alesi for the second time, and Alesi pitted for new Goodyear tires on lap 43. He rejoined in seventh. Three laps later, Prost was being hounded by Patrese, and he also pitted, ceding second spot to the Williams. When the Ferrari crew had problems changing his right rear tire, the Frenchman dropped to seventh behind Modena's Tyrrell-Honda.
On lap 48, Senna pitted without giving up the lead. Like Mansell, Patrese was having problems with the gearbox in his Williams, and when it selected neutral midway through Turn Seven, it caused him to spin out of second place. The car stopped on the outside of the track, perpendicular to the racing line. Piquet and Mika Häkkinen (making his F1 debut) barely managed to avoid him as they passed, but before Patrese could get out of the car, Moreno, in the second Benetton, went straight across the bow of the Williams, removing the nose of Patrese's car and the right front wheel of the Benetton. Neither driver was injured. Patrese and Moreno's cars remained on the course throughout the race, and Bertrand Gachot, driving the first race for the new Jordan team and challenging Satoru Nakajima, spun later after swerving to avoid them.
With Patrese out, Senna led Piquet, who was having to hold off Alesi, by over a minute. Alesi squeezed up to second on lap 53, while four laps later Prost disposed of Modena. Then on lap 70, Prost went from fourth to second in one move at turn five. With Alesi and Piquet running second and third, Piquet's Benetton pulled alongside Alesi– who had set the race's fastest lap while Prost was in the pits– in Turn Four, but could not get by. Down the straight, however, Piquet passed Alesi for second place. Prost also went by his new teammate on the left, and then sliced back to the right, between Alesi and Piquet, beating Piquet to the apex of Turn Five and regaining second place. By now Senna led by 40 seconds.
Gearbox troubles dropped Alesi to fifth before he retired less than 10 laps from the finish, leaving third place to Piquet who, like the two Tyrrells following, had never pitted for tires. Martini was pressing Satoru Nakajima for fifth, only to have his engine let go after 75 laps. A similar problem removed Gachot from eighth on the same lap, promoting Aguri Suzuki to sixth. The race ended a lap short of the planned 82 as the two-hour limit was reached, Senna taking the win having led every lap.
After the race, Senna assessed his new car's performance: "I had small problems with the gearbox, and the car balance was not optimum, so it was very difficult to drive. I'm looking forward to running a proper circuit with proper conditions and see what the car can do."Note: Only the top five positions are included for both sets of standings.