Think of Florida on a warm afternoon in July and youve got a good grasp of what your engine crankcase is like after you shut down after a flight. Throw in a little acid rain to season the heat and humidity to complete the picture. In short, the inside of an engine can be the perfect Petri dish for corrosion. Engine dehydrators or preservers are designed to address this by either pumping dry air into the engine, or sucking the humid miasma out of the crankcase and replacing it with moisture-free air. The idea has enough credence for three companies to have introduced dehydrator products. The latest comes from Tempest/Aero group, which adds a dehydrator to its well-regarded line of dry vacuum pumps and oil filters. The AA1000 Engine Preservation Systems retails for $235.
What It Is
Like the other engine preservers, the Tempest dehydrator pumps dry air into the engine after first passing it through a silica gel desiccant. The device consists of a small plastic enclosure about the size of small fishing tackle box-it may actually be a tackle box, by the looks of it-divided into two compartments.
One compartment serves as a cell to contain the desiccant, which consists of about a pound of tiny blue beads. You just pour them in the box, making sure that the filtered pickup tube is near the bottom of the desiccant. The other two thirds of the box houses a small, continuous duty low-volume air pump powered by line voltage. A clear plastic tube exits the pump to be inserted into the crankcase oil filler.
To make that easy, Tempest provides a lab-type rubber stopper for Lycomings with a fitting for the hose and a magnetic cap for Continentals. The cap has a hole for the plastic tube, so its easy to install it. The construction of this gadget is up to the task, but it has two flaws, in our view. Both the plastic tube and the line cord are too short. For our test in a Bonanza, we had to place the box on top of the engine, then snake the tube down into the filler. The power cord was so short that we needed an extension cord and this produces a snag hazard.
Because Murphy is a current resident in every hangar, what will eventually happen is that someone will trip on the extension cord, knock the box off the airplane and spill billions upon billions of little blue desiccant balls all over the floor. You will be sweeping them up for 100 years. The thing should sit on the floor, as the other two products of this type do, so it needs a longer hose.
Performance
To test the AA1000, we first gathered some control data by installing digital data loggers at the oil filler neck and in the hangar, as explained in the chart at right.