to recognize the first signs of the toxic effect of
system plumbing connections. Leaks are caused
breathing these vapors. The symptoms of inhala-
by undertorquing or overtorquing lines, hoses, or
fittings. Never assume that the leaks can usually
tion include nausea, dizziness, and headaches. If
be detected by operating the fuel transfer
a person should experience these symptoms during
fuel system maintenance, immediately stop and
pump/boost pump to pressurize the fuel system.
move the individual to a source of fresh air. If
Intermittent leaks are most often caused by loose
the individual appears to be completely overcome
cell fittings or connections. Fuel quantity probes
that are mounted on the high side of the tank/cell
by the vapors, get prompt medical attention.
When working with any type of aviation fuel,
usually leak when the aircraft is in a climb or
descent. In some cases, servicing the fuel tank/cell
personnel should always avoid prolonged contact
with the fuel. If a person's clothing becomes
to capacity may aid in locating these types of
leaks.
saturated, they should remove them as soon as
possible and wash off the affected areas with soap
Fuel Dye to Locate Leaks
and water. It is essential to know the location of
approved eyewash stations and how they are used.
The use of colored dye to detect hidden fuel
leaks is a practical means you can use in fuel
FUEL LEAK ANALYSIS
system leak source analysis. The dyed fuel will
leave a stain that can be traced back to the
In modern aircraft, the fuel systems are
source of the fuel leak. (The use of dyed fuel is
designed to operate satisfactorily under all
particularly useful in checking for leakage. This
conditions, such as acceleration and deceleration,
temperature, pressure and flight attitudes.
is especially true near the engine's hot section
However, no matter how good the design, the fuel
where high temperatures prevent the fuel from
leaving a wet spot.) When using a dye to aid in
system will not function as designed if it is not
the troubleshooting of fuel leaks, a logbook entry
maintained properly. A significant number of fuel
in the miscellaneous history section of the aircraft
leaks can be attributed to incorrect maintenance
logbook should be made. The fuel color, resulting
procedures used in installing fuel tanks/cells,
from the use of dye, can be disregarded in fuel
components, lines, and fittings. By referring to
sample analysis. Additionally, a similar entry
the applicable aircraft maintenance manual and
should be made for aircraft serviced with dyed
learning the general procedures discussed in this
fuel. You should always select a dye color that
section, you will have little difficulty in locating
will provide the highest visibility in the area where
the source of an aircraft fuel leak.
the leaking fuel is suspected. The use of 2 ounces
of dye for each 100 gallons of fuel in the cell or
LOCATION OF LEAKS
tank is required. The appropriate information for
Leak source analysis is the process of using
ordering the dye can be found in Appendix A of
the aircraft maintenance manual, fuel system
NA 01-1A-35. The addition of unmixed dye to
schematic diagrams, installation diagrams, and
empty fuel systems should always be avoided
troubleshooting charts. The most common
because it can cause deterioration of the cell
method of analysis is the methodical process of
lining. The dye should always be added to the fuel,
elimination to isolate the source of a fuel leak.
rather than fuel added to the dye. For informa-
In addition, you should first screen the aircraft
tion and correct procedures for the use of dyes
discrepancy book (ADB) to possibly save many
in fuel system leak detection, refer to the proper
man-hours looking for a leak. The review of a
maintenance manual.
prior fuel system discrepancy may reveal that
A liquid red or yellow dye that can be added
spilled fuel was not properly cleaned or com-
directly to the aircraft fuel tank is available.
ponents were improperly installed. Never assume
Before the dye is used to determine the source of
that the first leak you find is the only leak in the
fuel leaks, any visible fuel leaks in the tanks and
system. Completely check and test the entire fuel
plumbing must be eliminated. If you must use dye
system as directed by the applicable maintenance
to locate a hidden leak, test only one questionable
manual.
tank at a time. Add the liquid dye to the suspected
Severe leaks in the tank/cell drain system are
tank when it is one-third full, using a full 2-ounce
caused by a rupture, loose interconnecting fittings,
can of dye for each 100 gallons of tank capacity.
or cut or distorted O-rings. These leaks can usually
NOTE: Never use more than one 2-ounce
be detected immediately after refueling the
can of dye to each 100 gallons of fuel.
tank/cell. Dripping leaks are usually found at fuel
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