By Alan Sanderson
The inflator fan is potentially the most hazardous piece of ballooning equipment. By properly maintaining and using the inflator fan, you can minimize the hazards to yourself, your crew, and bystanders.
The inflator fan, while not included as part of the annual inspection, should be inspected for possible problems. Since a fan is transported, loaded into and unloaded from the chase vehicle, and handled on the ground, it is subjected to possible damage at every step. Proper use and handling can prevent most damage which could result in personal injury or require fan repair.
You should check the fan for several common problems
each time you are ready to use it. This is a brief list of items that you
can easily detect before starting the engine. If you find any of these problems
on the launch field, ask to borrow a fan from another pilot. Correct them,
or have them corrected by a competent repair shop.
Is the guard intact? Check for broken wires, broken welds, and loose or missing fasteners.
Is the frame intact? Check for broken frame members, broken welds, and loose or missing fasteners.
Is the propeller intact? Check for chips, cracks, and loose or missing fasteners.
Is the engine tightly mounted? Check for loose mounting bolts.
Is there enough oil in the engine? Check the oil level before each use.
Is the fan properly positioned? Check for loose
material that could be drawn through it, stable footing, and proper aiming.
A piece of carpeting under and a few feet behind the fan will reduce the
amount of debris picked up from the ground.
You can prevent problems with the fan using proper crew training and situational awareness. Make sure that no crew member operating or standing near the fan has loose long hair, jacket strings or scarves that could be pulled into the fan. If your balloon has handling lines near the throat, either shorten them so they cannot reach the fan, or make sure that the crew member near the fan keeps the loose end of the handling line away from it.
I have also observed a crew person moving a running fan to keep it aimed into the throat. The spinning propeller acts like a large gyroscope, and moving the fan can stress the crankshaft enough to break it. Turn the fan off to move it, then restart it.
The end of the flying season provides the opportunity
to perform required maintenance on your inflator fan before storing it away
for the winter. This requires a more thorough inspection and preventive
maintenance procedure than the pre-inflation inspection outlined above.
Guard and Propeller
Remove the spark plug from the engine and ground the plug wire so it will not accidentally start while you are working on it. Remove the guard and clean it. Carefully check it for cracked welds or broken wires. If it is repairable, weld or braze the broken joints. Otherwise replace the guard. If the guard is held together by clips, safety wire or wire tie the clips. Clamp the guard halves together with screw type stainless steel hose clamps. Clip off any excess length to prevent snagging clothes. White plastic wire ties become weak and brittle when they are exposed to sunlight, so they are not recommended.
The propeller can be damaged by the sand and debris that are sometimes pulled through the fan. Carefully inspect the propeller blades, especially the leading edges and the tips. If the propeller is metal or plastic, carefully smooth the jagged edges of any dings with fine sandpaper or a small file. If you find any large dents, bent blades, or cracks, replace the propeller or blade.
A wooden propeller will often have the finish worn off the leading edges and tips of the blades. Remove the propeller if it shows such wear. If there are splits in the blade, replace it with a new propeller. Carefully sand any small dings. Larger dents that do not split the laminations can be filled with a mixture of carpenter's wood glue and sawdust, and sanded smooth. Sand the entire propeller with fine (180 grit) sandpaper. To make the propeller more visible during operation, paint the blade tips bright red using a good enamel. Then apply several coats of an exterior polyurethane varnish, sanding lightly with 400 grit sandpaper between coats. Balance the propeller using a rod or dowel through the center hole. Support the rod between two parallel, level straight edges. Apply more varnish to the high end of the blade, until the blade stays level. Remember the varnish loses weight as it dries.
Check the hub, bolts, set screws, key, and engine shaft. If the hub is loose, remove the set screws, apply thread locking compound, and tighten them. If the hub is still loose, replace it. When replacing the propeller, torque the 1/4 inch bolts to 20 ft-lb. Use nylon insert locking nuts or removable thread locking compound. Aircraft bolts can be safety wired.
Rotate the propeller, measuring the clearance to the cage, and between each blade and the engine. Both blades must be the same distance from the engine. Use a pencil to check the propeller clearance. If the blade does not run true, align the hub, or check for a bent crankshaft. A bent crankshaft must be replaced. A split wedge hub can be aligned by carefully tightening the bolts in sequence until the propeller runs true.
Engine
Most small engines were designed to be hard mounted to the frame. If you have an older fan with rubber bushings under it, replace them with hard spacers.
Clean the engine, and tighten any loose fasteners. Change the oil. Empty the fuel tank, and fill it with fresh fuel treated with the proper amount of gasoline stabilizer. Replace or clean and gap the spark plug. Test run the engine, and turn off the fuel valve to stop the engine. Remove the spark plug, and pour one capful of motor oil into the cylinder. Crank the engine a few times, then replace the spark plug. Store the fan in a cool, dry place. When flying weather arrives, the inflator fan will be ready to go.