An air brake or, more formally, a compressed air brake system, is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply. This air brake system, when fully charged, is fail safe: Trailer Service Brakes Brakes Utility Trailer Air Brake Air brakes can be either drum brakes or disc brakes, or a combination of both. How do air brakes work on a trailer . Control or service lines are commonly associated with the blue air line function of the air system. If playback doesn't begin shortly, try restarting your device. The hayes air utility brake control # ha100400c, which you reference, is designed for towing vehicles that have air brakes and trailers that have electric brakes.if you want to convert your trailer's air brakes to electric brakes you will want to remove the air brakes and then install the electric brakes from scratch. But the amount of braking force always relies on the amount of charge present in the system. How t...