London — Steadily, and with only limited publicity, Britain is equipping itself with an air defense system intended to be more efficient than that of any other country.
A combination of high-performance jet aircraft, supersensitive long-distance radar, and ultramodern communications centers, many of them underground, is being developed to counter possible Soviet air attacks.
The complete system, planned to cost L3 billion ($6.75 billion), will be operational within five years and will greatly enhance the ability of america's allies in Europe to deal with either limited probes or large-scale air assaults from the Warsaw Pact.
The rationale for this massive defense effort is that for some years it has been apparent that the Soviet Union has been building up its air strike capacity in order to use it against Britain and over North Sea and Atlantic waters vital to the Western allies' ability to fight a major war.
Until the late 1970s Britain's air defenses were languishing, with aging bombers and fighter aircraft dependent on inadequate early warning systems. Working closely with NATO, the British government has decided to upgrade the nation's air defense to maximum possible effectiveness.
The responsibilities of the Royal Air Force in time of war would include helping to safeguard important sea lanes and protecting Royal Navy flotillas, as well as providing air defense for British ground targets.
To help it face up to the Soviet Union's growing squadrons of supersonic Backfire and Fencer strike aircraft, the RAF -- like the air forces of West Germany and Italy -- is equipping itself with Tornado fighter bombers fitted with a form of radar that can detect and zero in on enemy aircraft more than 100 miles away across the horizon.
As back up for the Tornado jets, the RAF is converting a fleet of jet airliners to the role of tankers so that the fighter bombers may be refueled in the air.
In addition, about a dozen Nimrod aircraft, formerly assigned to antisubmarine operations, are being converted to carry multidirectional radar equipment with a range of about 300 miles.
By the mid-1980s a series of ground radar stations will also be operating, some in the far-flung islands of northern Scotland, others further south in England.
All the information coming in from airborne and ground radar will be fed by computer to central control stations. When the entire network is complete, there will be upward of 40 such centers, many of them buried deep underground and linked to NATO command posts throughout Western Europe.
The aim will be not merely to detect possible Soviet thrusts, but to work out swiftly where attacks might be concentrated and to decide how best NATO airpower could be mobilized to mount an effective defense.
An air defense system as modern as that now being created would be far beyond Britain's ability to pay for it. NATO has thus undertaken an elaborate cost-sharing scheme to avoid penny-pinching.
The Tornado jets that will provide the air defense system with most of its retaliatory capacity are being built by Panavia, a consortium of European aircraft manufacturers.
Efforts are going ahead to develop other areas of cooperation among the European allies so that their industries will benefit from this crucial refashi oning of Britain's air defenses.