Hydraulic system failures affected landings by two American Airlines jets, a DC-10 carrying 297 people to Dallas and a Boeing 727 carrying 34 passengers and crew members to Rochester, N.Y. Backup systems took over in both cases and no injuries were reported, officials said. Airport emergency personnel and the Rochester Fire Department lined the runway as the 727 touched down at Greater Rochester International Airport. American Airlines spokesman James Brown said one of three hydraulic systems of the plane failed en route from the Raleigh-Durham, N.C., airport and the crew was forced to use a backup hydraulic system to lower the landing gear. The plane had to be towed from the end of the runway to the terminal. Flight 154 en route from San Francisco with 284 passengers and a crew of 13 experienced a failure in the primary hydraulic system controlling the landing gear after landing at Dallas-Ft. Worth International Airport. The pilot reported trouble steering the craft while taxiing and the DC-10 was also towed to the gate.