Yesterday's air crash at the 14th Street bridges seems certain to revive a years-old controversy over how safe National Airport is.

Facts remain sketchy about why the Air Florida Boeing 737 plunged into the Potomac after taking off in heavy snow. But initial reports suggest that two long-criticized aspects of the busy terminal will draw suspicion as contributing factors--its curved approach and takeoff corridors and its short runways.

Speculation on cause of the crash includes engine failure, icing-over of control surfaces and pilot error. But questions will be asked about whether National's layout and flight rules played a role.

The airport's preparation for water rescue is likely to come under close scrutiny as well. Critics have argued for years that the authorities at National are ill-equipped to fish survivors out of the river, even though everyone agreed that crash-landing on water was likely in an accident at the airport.

Planes taking off to the north, as was the Air Florida jet yesterday, bear hard to the left above the 14th Street bridge to follow the course of the Potomac, a required maneuver that steers them clear of the Washington Monument and a restricted zone around the White House and minimizes jet noise on Washington residents.

Generally speaking, pilots prefer direct courses after takeoff. "The best thing to do is full power, straight out," one pilot said yesterday. This does not mean that curves are inherently dangerous, but if a plane runs into trouble while making a low-level turn, pressure on the pilot grows accordingly.

The other factor is runway length. The longest of National's three runways--the one used by the Air Florida plane yesterday--is just under 7,000 feet and has virtually no overrun space after the concrete ends. Dulles International's runways are in the 10,000-foot range with plenty of open space beyond them.

Pilots have aborted takeoffs safely at National. But after reaching a certain speed and position on takeoff runs, planes must leave the ground or brake quickly and still go into the water. At airports such as Dulles, pilots have more leeway to abort their take-offs.

One passenger aboard yesterday's flight, a pilot, told a Washington Post reporter that the plane did not gain enough speed for a proper takeoff and never gained proper altitude during its takeoff.

The last fatal airliner crash at National was in 1949, when an Eastern Airlines DC-4 collided with a war surplus fighter. All 51 of the airliner's passengers and its crew of four died in that crash, making it the nation's worst air disaster at the time.

Some safety specialists explained National's 32 years without a major crash by saying that the airport was so dangerous that it was safe. That is, the tricky corridors to and from National and the short runways require pilots to give it their full attention, making it unlikely that loss of concentration would cause an accident.

The Federal Aviation Administration allows only medium-range jet aircraft to operate out of National.

"Everybody knows it's a rough airport and you can bust your a-- going in there," one pilot said yesterday. That makes them pay extra attention.

Three pilots interviewed last year by The Washington Post all said they prefer to use Dulles or Baltimore-Washington International. All three said that on occasion they had declined to land at National due to weather that would have been no threat at an airport with better instrument facilities and longer runways.

Because the airport is on the river, pilots also have criticized preparations for water rescue.

National Airport spokesman Dave Hess said the airport has three rescue boats on call at all times and they were dispatched to the stricken plane yesterday. At the same time, emergency calls went out to area police and fire departments equipped with helicopters and to the military.

However, before yesterday's crash critics had charged that the airport would be ill-prepared for such an emergency. In testimony prepared for hearings on the new National Airport policy last summer, civic activist Sherwin Landfield said: "An engine failure on takeoff to the north would most likely mean going into the Potomac to try to avoid hitting a bridge." And in such a case, he said, it would be impossible to get rescue units to the scene in time to avoid further tragedy.