The British Army is studying the lessons it learned from the deployment of Challenger-2 tanks to Oman for an exercise, and is considering plans to make the tanks more reliable in desert conditions. The problem is that the British version of the Challenger-2 is designed for Europe while the Omani version of Challenger-2 is designed for the desert. The main difference is that the Omani version has a larger radiator and engine cooling system. This pulls in air at the rear, while the British version has its intake on top. The rear position makes it harder to ford rivers, but the upper position is more likely to ingest dust in desert conditions. During the exercise, the British found that the air filters on their tanks had to be changed every 4-6 hours. As these filters cost $1853 each and will last a year in Europe, this is something of a problem. During tests in Canada, the British Challenger 2s replaced their air filters every 4-6 days due to the "prairie dust". Various fixes are being considered, including improved air intakes, track skirts that would reduce the amount of dust thrown up by the tracks, and a stronger cooling system. There are also reported plans to refit the tanks to operate in arctic conditions.--Stephen V Cole