Why pilots are planning a ban on flights to USSR

As they prepare to ban flights to Moscow, the pilots who fly the world's passenger jets ask these questions about the Soviet shooting down of the Korean Air Lines 747:

* Why hasn't Moscow recovered and released not only the ''black box'' flight recorder from the Korean jumbo jet, but also the cockpit voice recorder?

''The recorder,'' says Capt. Mike Clark, vice-chairman of the British Air Line Pilots Association, ''would prove whether or not the Soviets took internationally agreed interception measures, such as firing tracer bullets as a final warning to the Korean pilot. The cockpit recorder runs all the time during a flight, even when pilots ask for a drink or a meal.

''The Soviets won't let other countries come into their space to look for the two recorders. In the West we have the ability to recover such equipment even from 10,000 feet of water. I imagine the Soviets do, too - and they must know where they shot the Korean plane down. . . .''

(UPI reports from Tokyo that the Soviet Union told Japan Thursday that its naval search teams had retrieved ''documents'' and fragments from the downed airliner.)

* Why hasn't the Kremlin signaled, privately or publicly, that it is taking precautions to see that such an incident can never happen again?

''The reason we're calling for a ban on flights to the USSR, and talking to ground controllers to stop Aeroflot coming here, is to bring home to the Soviets that vital air safety is at stake,'' says Terry Middleton, general affairs secretary of the International Federation of Air Line Pilots Associations, which is based in Britain.

Pilots contacted by this newspaper agree that the Soviet Sukhoi fighter that shot down the jet may well have been unable to talk to the Korean plane. Civilian airliners use VHF (very high frequency) radios, while military aircraft usually are equipped with UHF (ultrahigh frequency), the pilots say. US sources suggest the Soviet military deliberately prevents its pilots from contacting Western planes to stop attempts to defect.

''Something has to change here,'' says Captain Clark. ''The Soviets have got to do something before there's a tragic loss of even more lives. By the end of the century we could have 1,000 people at a time in civilian aircraft. We have to work out some way of ensuring their safety on routes such as the New York-Seoul one.''

* Why can't Moscow produce a definite, consistent account of what its planes did instead of day after day of partial fact mixed with large doses of propaganda, including such euphemisms as ''stopping'' the Korean plane?

''It helps no one for the Soviets to say that the jumbo jet was showing no lights, then to hear on the tape released by the Americans the Soviet pilot saying he could see air navigation lights burning,'' says Captain Clark.

Pilots find it difficult to believe the Soviet fighter pilots could not recognize the unique shape of the jumbo jet. If, as reported, four Soviet fighters tracked the Korean jet at different points, it means that four separate pilots, presumably highly trained and reliable, either reported a plane that was much bigger than the US reconnaissance plane, the RC-135 (a modified Boeing 707) , or failed to do so.

The Soviet pilots could also have seen the jumbo's passengers along the length of the 747 fuselage, Western pilots say. Overhead cabin lights may well have been dimmed after the meal and movie to allow passengers to sleep, but at least some passengers usually prefer to read or talk.

* Finally, will the Soviets eventually offer compensation for the loss of the jet and to the families of those killed?