Doughty Hanson, the fast-growing venture capital firm, is buying the division for cash.
BTR said it had decided to sell the business "in the face of major consolidation in the aerospace industry." It added that the price was attractive, representing a multiple of 2.1 times the division's 1997 sales and 9.8 times operating profits.
The deal takes the amount raised from disposals by Ian Strachan, BTR's chief executive, since his appointment two and a half years ago to pounds 4.2bn.
The aerospace businesses, which include parts of the former Dunlop rubber group which BTR bought in 1985, were not specifically earmarked for disposal. However, BTR decided to sell them because they were not large enough to compete in the global aerospace market.
"Although profitable, they are small both in terms of BTR and their sector, and are not able to achieve our stated goals effectively," he said.
The move was welcomed in the City, where BTR shares firmed 7.5p to 154p.
BTR is selling Standard Aero, which repairs aero engines ; Dunlop Aviation, which makes aircraft wheels and brakes; Aero Engine Equipment, which makes components for turbofan engines; and Dunlop Precision Rubber, which makes seals and mouldings for the aerospace market.