The nation's airlines are taking steps to improve flight safety during winter.
Aviation safety experts say they feel certain that last January's fatal Air Florida crash in Washington, D.C., and an accident involving a World Airways DC- 10 at Boston's Logan Airport 11 days later, will spur considerably more research and possibly more regulations.
''I think in the meantime we're going to see a variety of interim measures (taken by airlines) on the conservative side in new procedures and additions to flight manuals,'' says Edward Wood, director of engineering and maintenance at the Flight Safety Foundation. ''It's just too bad that it seems to take something catastrophic to spur action.''
But problems haven't been limited to the two highly publicized incidents last winter. According to a recent survey of 20 airlines by the Air Line Pilots Association (ALPA), in at least 70 instances during the last few months, pilots were forced to abort or alter their takeoff procedure because of engine icing and false or erratic readings on their instruments.
Among the changes that have taken place to boost winter flying safety:
* Following the Jan. 13 crash into the Potomac River of one of its 737 jets, Air Florida instructed its crews to turn on the engine anti-icing system under a very wide variety of winter conditions. Air crews also have been instructed to increase their takeoff speed in snow, ice, or slush. And takeoffs should come only after a careful check of flight surfaces for snow and ice accumulation.
* American Airlines, which performed the de-icing chore for Air Florida at Washington's National Airport, has ordered its personnel to increase the amount of glycol in the airline's de-icing fluid from the usual 25 percent to 40 percent. The solution used to de-ice the Air Florida jet that crashed apparently contained only about 12 percent to 15 percent glycol.
Extensive hearings in Congress on aviation safety research and by the National Transportation Safety Board (NTSB) into the specific causes of the Air Florida crash have just ended in Washington. While they did not point to a clear course of action to solve many of the problems discussed, they did spotlight areas of disagreement among the experts and some serious information gaps.
Although public pressure for more regulation traditionally intensifies after any plane mishap, some aviation safety experts warn that more rules are not necessarily the ''magic'' answer.
''I think we need to clean up minimum requirements, but I also think there's a need for better safety management,'' says Charles Miller, a former NTSB official who now is an independent aviation consultant. ''The airlines have to take this on in a serious manner. They can't assume that they can just hide behind the fact that there is or is not a (federal) requirement.''
''You have to leave room for judgment and flexibility on the part of the pilot,'' suggests FAA spokesman Fred Farrar. ''Often when you're dealing with people, persuasion is better than 'You shall do something.' If we tried to tell the pilot what to do in every conceivable circumstance from start to finish, we'd be fools.''
But Rep. Dan Glickman (D) of Kansas, chairman of the House Subcommittee on Transportation, Aviation, and Materials, argues that deregulation and the tough economic conditions under which many airlines are operating make a stronger safety role for the FAA more imperative than ever.
''The fact that the economics of flying is not very good these days makes it all the more important that the FAA enforce the rules they now have on the books ,'' he says.
The FAA currently bars takeoff if snow, frost, or ice adhere to the wings or other airplane surfaces. And it has nine specific cold weather recommendations it reissues to airlines at the start of each winter. But the safety agency has no rules of its own governing when, how, and what kind of fluid should be applied to reduce ice and snow accumulation on aircraft during severe weather. The reason: Airlines use a variety of different de-icing products. As long as they abide by the varying directions, they are proceeding safely. The method and timing of de-icing vary from airport to airport.
''The only (FAA) rule is that you can't leave with ice on your wings,'' says Congressman Glickman. ''There is no basic standard as to when, how, or what kind of materials should be involved. I find that incredible.''
On Jan. 28, the NTSB suggested to the FAA that flight crews be required to check wing surfaces at least every 20 minutes after de-icing. The recommendation was one of several issued as a result of preliminary findings from the investigation into the Air Florida crash. The Air Florida jet took off 40 to 50 minutes after de-icing, and apparently the crew made no visual check of the wings or other flight surfaces.
But the FAA balks at setting any time limit on grounds that it could easily encourage a feeling of false security. Despite this disagreement, the FAA telegraphed all of the NTSB recommendations verbatim to the nation's airlines and manufacturers. The FAA also held a follow-up conference by phone the next day with its regional and flight standard employees.
''In a broad sense - by disseminating the information immediately--the FAA was very responsive,'' says David R. Kelley of the NTSB safety research bureau.
Another problem spotlighted in the investigation of the Air Florida crash was the apparent freezing of the probe that measures air pressure in the engine. This is believed to have caused cockpit instruments to give the crew a mistakenly high reading of engine thrust. It is one reason many airlines now specify that engine anti-icing (basically hot air) be undertaken whenever winter weather appears evenly mildly threatening. The FAA has said it plans to send the airlines a new advisory pinpointing methods by which pressure probe ''freezing'' can be recognized by cross-reading other cockpit instruments.
Still another common bad weather problem pinpointed in the recent hearings: the frequent lack of reliable, up-to-date information for pilots on runway conditions and on where the aircraft is on the runway based on runway length and aircraft speed. The NTSB, ALPA, and a number of safety experts have long urged the installation of distance markers along the runways as a firsthand pilot aid. The Air Force has successfully used them for about two decades. But FAA spokesman Farrar insists such markers would be expensive and, more important, a possible distraction.
Experts also are increasingly concerned about the current lack of a satisfactory system for measuring traction on runways under wet and icy conditions. They also would like to see more systematic procedures for giving pilots more timely information on runway conditions, including the latest reports from other pilots who have landed.
It was disclosed in the Logan Airport incident that the most recent pilot report relayed to the World Airways crew was 37 minutes old. But FAA spokesman Farrar stresses that the DC-10 cockpit crew assured controllers that they had heard about poor braking conditions from FAA and Massachusetts Port Authority field condition reports.