THE Provisional IRA may be preparing a major atrocity within the next few weeks following the success of an ambush on Sunday when it lured Scots troops to within yards of the Eire border and machine-gunned an unarmed helicopter, forcing it to crash-land in County Tyrone.
Intelligence sources in Ulster are still refusing to say whether the helicopter, a Gazelle light reconnaissance model, was hit by any of the 300 rounds the IRA claims to have fired at it. None of the three men aboard was wounded by gunfire, although one has serious back injuries caused by impact damage.
It is believed that the East Tyrone PIRA, one of the toughest in Northern Ireland, staged a diversionary ''come-on'' operation by driving a number of vehicles in a sensitive border area to draw Army attention.
The Army responded with a foot patrol of the King's Own Scottish Borderers backed up by a Gazelle helicopter flying top-cover for the men on the ground. It is not yet clear whether the terrorists planned initially to shoot down the helicopter or ambush the infantry.
But they used at least two heavy-calibre machine-guns -- either American M60s or Soviet-made and Libyan-supplied 12.7mm weapons -- and a number of automatic rifles to carry out the attack. The helicopter plunged into a field near the border. Two Army Air Corps pilots were slightly hurt, and a sergeant-major from the KOSB suffered spinal injuries in the crash.
The damaged aircraft, which normally carries one or two of a crew and a maximum of two passengers, is now under armed guard while it is examined by forensic and aviation experts.
Helicopters are prestige propaganda targets. Only one previous aircraft, a Lynx, was brought down by gunfire in 1988 in South Armagh. It was the first casualty of its kind in the 20 years of conflict in the province.
In December last year, the South Monaghan PIRA, aided by local activists, mounted a mass attack involving more than a dozen gunmen on a KOSB vehicle checkpoint at Derryard in County Fermanagh only a few yards from the border. Two soldiers died and a third is still in hospital.
The terrorists are believed to have intended to wipe out the nine-man garrison of the outpost as a pre-Christmas coup. The assault was carried out using rocket launchers, machine-guns, automatic rifles, grenades and a flame-thrower. It was foiled by the intervention of a four-man Army patrol which appeared unexpectedly and drove off the attackers with more than 100 rounds of small arms fire.
The authorities now believe that a further strike against the KOSB has been planned to mar the end of the unit's tour in Ulster. The battalion has found considerable quantities of Semtex, the IRA's favourite explosive, and uncovered a number of weapons' hides in the Tyrone-Fermanagh area during its four months' stay in the province.