Making the best of a messy situation
By Joe Escobar
Fuel cell maintenance is definitely not on the top of the list of a mechanic's most favorite tasks. Fuel leaks and subsequent fuel cell work often mean you go home at the end of your shift with that unmistakable smell of fuel permeating your clothing and skin. But there are some tips you can use to help make this messy job a little easier.
The first indication that there is a leak is usually fuel dripping on the bottom of the aircraft. When you start investigating for the source of the leak, be sure to keep in mind that fuel often times travels a long way before finding an exit point. This can sometimes make it difficult to locate the source of the leak. Don't assume that the leaking fuel cell is near the visible leak. Be sure to follow the leak path before pulling a suspected leaker.
Hartwig Aircraft Fuel Cell Repair offers the following when inspecting for leaks. "Before removing the cell, check carefully to determine possible areas where the leak or leaks may be originating. Inspect the wing or fuselage cavity and trace any stains or fuel back to their original source. Because of the effect gravity exerts on fluid movement, leaks often do not originate close to where the leak is most visible externally."
Also remember that other components of the fuel system can leak. Connections, hoses, and vent areas should be checked for leaks. Also, just because a fuel cell is leaking doesn't necessarily mean it needs to be replaced. There are some leaks on a fuel cell that can be corrected. These include:
Loose hose clamps
Loose transmitter screws
Loose plate or filler neck bolts
Cracks on the filler neck or tubing
Taking the time to investigate these items can sometimes prevent unnecessarily changing a fuel cell.
If you have inspected the fuel cell and determine that it needs to be removed, here are a few tips from Eagle Fuel Cells on making the removal task a little easier.
- Have a positive attitude. Having a good attitude will make this task go easier.
- Read the technical data. Not following procedures can cause damage to the cell and/or the aircraft.
- Tape the edges of openings. This will prevent damage to the cell as well as protect your flesh from the rough metal edges.
- Loosen clamps and let the rubber relax. Remember that the fuel cell may have been installed on the aircraft for many years, and the rubber takes a set underneath the clamps. If you loosen the clamps and let the cell sit for a while, it will allow the rubber to relax, making removal easier.
- Warmth is your friend. Cold fuel cells are stiff, and make the process that much more difficult. If possible, try to work with warm fuel cells. Even letting the aircraft sit in the sun for a short period can warm the cell up enough to make the process easier. Be careful using heaters and blow dryers as they can be an ignition source. Vapors in a defueled aircraft are more combustible than a fully fueled aircraft.
- Roll the fuel cell into a tube lengthwise before removing. This will make removal easier than just grabbing parts of the cell and trying to pull it out the access panel.
Inspect the fuel cell
After removal, inspect the fuel cell for any obvious damage. An inspection can reveal damage to the fuel cell that can be avoided in the future such as FOD damage or damage from a fueling nozzle.
Avoid the pressure
Eagle Fuel Cells strongly recommends not pressurizing a fuel cell to find a leak. Technicians at Eagle Fuel Cells pressurize the bladder to very low limits when checking for leaks. Pressurizing a cell to just over 1/4 pound pressure can stress seams and damage the tank. In addition, soap solutions that a mechanic would typically use to find a leak can actually mask small leaks that can be present in the cell.
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