ROYAL FAMILY/A supersonic celebration for Britain's `Queen Mum'

Queen Elizabeth, the Queen Mother, is marking her 85th birthday by breaking the sound barrier amid a whirl of activity typical of the busy life she leads. The supersonic segment of her celebrations has come as a gift from the state-owned British Airways: a trip aboard a Concorde airliner which will whisk her around the coast of Britain.

Other parts of a hectic birthday week: a ride in a helicopter, opening a geriatric unit at a hospital, attending a chamber concert, visiting an exhibition of 18th century French drawings, accepting cheers from 15,000 people at the Sandringham Flower Show.

The Queen Mother, widow of King George VI, is known affectionately to many Britons as ``the Queen Mum.'' Officials at Clarence House, her London home, report that she's in fine form and eager to make a proper party of her birthday.

The flight on the Concorde, they said, would delight her. She had always wanted to bust the sound barrier but was never able to find time to squeeze it in.

The Queen Mother was born Elizabeth Angela Marguerite Bowes Lyon on August 4, 1900. Twenty-three years later she married the future George VI. Since her husband's death in 1952, she has followed an almost ceaseless round of royal engagements worldwide.

Much of her popularity rests on a gracious smile and a relaxed manner with the people she meets. But it is her hard work that has made her possibly the most admired woman in Britain.

To open a village hall in Norfolk, for example, she decided to get to her destination by helicopter.

The program worked out for her birthday week included a visit to cottages on the Sandringham estate to meet pensioners and spend a lengthy period chatting with them.

She also made room for a call at the royal stables to feed sweets to her favorite horses. The cellist Mstislav Rostropovich agreed to fly to Sandringham from France and conduct a concert in her honor.

The chairman of British Airways, Lord King, said he had been surprised to hear that the Queen Mother had never flown on theConcorde.

``When we heard that a supersonic flight was a long-held wish, we were happy to oblige,'' Lord King said. ``To grant that wish is a present we are proud to give.''

Lord King's flight plan for the supersonic ``Queen Mum'' includes a jaunt around the British coastline as the royal passenger enjoys a light lunch aloft. Then the birthday ride will culminate in a brief burst of speed -- 1,450 m.p.h. -- probably over the Bay of Biscay.