The National Transportation Safety Board's hearings on the Jan. 13 crash of Air Florida's Flight 90 ended yesterday without producing "any surprises," according to the hearing panel's chairman.

With the close of the public part of the inquiry after nine days of testimony, the board will begin analyzing data and tesimony before issuing its findings and recommendations in about six months.

Francis H. McAdams, the panel chairman, said the board will concentrate on the questions he outlined at the hearing's start: the procedures used to de-ice Flight 90, the ratio between water and ethylene glycol, the properties ethylene glycol has for de-icing aircraft and the performance of the downed plane, a Boeing 737.

From the outset, speculation has focused on whether Flight 90's takeoff was hampered by the accumulation of ice on its wings and fuselage during the blinding snowstorm that hit Washington the day of the crash. Asked why he thought Flight 90 crashed into the Potomac, McAdams said, "I don't know the answers . . . I wouldn't draw any conclusions at this time."

According to testimony yesterday by Augustus A. Melton, Jr., National Airport's manager, some pilots landing before the crash had reported braking conditions on the main runway were "poor," but Melton said the actual performance of landing aircraft--despite these reports--remained normal.

Melton testified that the entire runway had been cleared and sanded prior to Air Florida 90's takeoff, but that 30 percent of the northern end of the runway--past the takeoff point of the plane--was "patchy," with accumulations of snow. "In our estimation, though, that didn't constitute a hazard," Melton testified. Asked how much snow would constitute a hazard, Melton declined to use a specific number or percentage, insisting that it was and would be "a judgment call."

Deputy D.C. Police Chief John Connor, who was in overall charge of rescue and salvage operations at the crash site, said that given the weather and traffic conditions at the time of the crash, rescue operations went as well as could have been expected. Even if inflatable boats had been available, Connor said, their use would have been difficult. "Ice on the water hampered efforts considerably," he said.

Although critics of National Airport seized on the crash as evidence of the airport's allegedly hazardous conditions, McAdams declined to allow the inquiry to be broadened into a general examination of National's safety. When David F. Thomas, an air safety investigator for the NTSB, attempted to question a Federal Aviation Administration official about the adequacy of landing approaches to National, McAdams interrupted to say that the panel was interested only in National's problems as they pertained to events the day of the crash.

Asked after the hearing if he thought National was safe, McAdams replied, "On the evidence that I've heard, if all the procedures are followed, National Airport can be operated out of safely." Asked if procedures were being followed, McAdams said, "Yes."