HAWKER SIDDELEY CANADA TO SELL UNIT <Hawker Siddeley Canada Inc> said that, due to poor market conditions for railway freight car manufacturing, it plans to sell its Trenton Works division in Trenton, Nova Scotia. Hawker Siddeley said it set aside a provision of 7.7 mln dlrs for the proposed sale. It also said lower 1986 earnings were due to much lower earnings in transportation equipment and losses in steel castings and forgings, which offset gains in the mining sector and improvements in forestry equipment. Hawker Siddeley also said demand for new railway equipment was limited with export sales frequently restrained by customers' financing difficulties. Demand for steel castings and wheels for Canadian railways continued to be very depressed with maintenance requirements at the lowest level in the past decade. However, there was demand for industrial casting due to increased hydro-electric power generation, the company said. The company said manufacturing of mining machinery and tunnelling equipment showed greatly improved results in the U.S. and export markets, mainly China and India. The Orenda division maintained a high level of activity in aircraft engine repair and overhaul and in the manufacture of engine components. Sawmill equipment and skidder operations were affected by a strike in British Columbia and the extended debate on U.S. imports of Canadian lumber, but there were encouraging signs at yearend, the company said.