Federal experts investigating the Air Florida crash urged last night that airlines adhere strictly to safety procedures for cold-weather flying and pay special attention to de-icing of both engines and wings.

The National Transportation Safety Board listed nine areas of concern in a letter to the Federal Aviation Administration, which regulates safety matters for all U.S. airlines. The FAA responded immediately, stating it has "acted to disseminate the information" to all airlines and promising to "expedite its further detailed technical review of the recommendations . . . "

Board member Francis McAdams, who read a prepared statement but declined to answer questions, said, "I want it clearly understood that while these recommendations generally arise out of the Air Florida accident, they are not to be taken as defining the cause of that particular accident."

But the clear implication of the safety board's action was that the pilot and copilot of Air Florida Flight 90 in some respects had acted imprudently when they elected to take off from Washington National Airport in a blinding snowstorm Jan. 13 and crashed into the 14th Street bridge, killing themselves and 76 other people.

The recommendations come after a rash of aircraft incidents in which the common denominators have been cold temperatures, snow and ice. The Air Florida crash is the worst, but two people have also apparently died in a World Airways crash in Boston and other incidents have occurred at New York's LaGuardia and at Baltimore-Washington International airports.

Early speculation on the Air Florida crash has centered on the possibility that ice and snow on the wings destroyed the Boeing 737's normal ability to remain in flight after it lifted from the ground. Flight 90 was sprayed with a mixture of ethylene glycol and water to remove ice and snow, but the treatment came 43 minutes before takeoff.

Thus, the board recommended last night that crews visually inspect wing surfaces before taking off if it is snowing or sleeting and more than 20 minutes has elapsed since the plane received a de-icing treatment.

The board also said the FAA should immediately require that crews be alerted that spraying their aircraft with de-icing fluid will not protect against re-icing if it is still snowing or sleeting. Investigators have determined that between .7 and 1 inch of new snow fell between Air Florida's last de-icing treatment and its takeoff.

The board has found that frozen sensors in the engine could have given the pilots an indication that they were developing more thrust than they actually were. "The preliminary investigation . . . indicates that the engine anti-ice system was off at the time of impact," McAdams said in his statement. "We have not determined whether it had been used during the pre-takeoff ground operation."

The board's letter praised the FAA for a recent bulletin requesting airlines to review their de-icing and anti-icing procedures, but said it "does not believe this approach has obtained the needed results. Rather, the FAA must actually review prescribed procedures."

The FAA, like other regulatory agencies, has been subjected to heavy budget cuts and FAA Chief Lynn Helms is known to prefer a cooperative approach to aviation safety, with airlines doing as much of their own policing as possible, rather than the strong regulatory-enforcement approach advocated by some of his predecessors.

The board also said it is concerned that the exhaust of aircraft standing in a long line on a wet or slushy runway in cold weather will create and throw moisture that freezes on the engines and wing edges of trailing planes. It suggested that air traffic controllers be alerted to that possibility and keep planes at the terminal until they can proceed immediately to takeoff.

The board also said it is continuing to study the role that snow and slush on the runway might have played in slowing the speed with which the Air Florida flight accelerated. It asked the FAA to ensure that all airlines are made aware of the fact that water and slush retards acceleration speed.

The FAA, in its statement, said "it appears" the safety board "recommendations emphasize the importance of strict adherence to existing FAA regulations and recommmended practices."

McAdams stressed that the board's investigation of the Flight 90 crash is continuing, and said much work remains to be done in analyzing information on the cockpit voice and flight data recorders. The two engines are also being torn apart to see what can be learned from them.