The American TFR on the Vulcan had a habit of every now and again of indicating a "fly down" instead of "fly up". It was very unreliable and the pod was changed so often even engine fitters were experienced with the task. It also had the silliest cooling system. The air from outside was passed over the electronics straight from the cooling vents. This was OK when the air was dry but if the aircraft flew through cloud or rain we used to remove the pod and tip it up to let the water run out.