Also, after any maintenance on the AEL Mk III,
calibration is REQUIRED.
DETECTOR AEL MK III (CFD)
The contaminated fuel detector is a portable self-
contained unit. This instrument is used to determine
the quantity of solid contamination present in aircraft
The detector consists of a fuel sample container,
a fuel filtration system employing millipore filters,
and a light transmission system for determining the
quantity of solid contaminants on the millipore
filters. All components necessary for filtration and
measuring transmitted light are incorporated into
one serviceable package. See figure 3-5.
The level of fuel contamination is measured by
using the principle of light transmission through a
millipore filter. A sample of fuel is filtered through
the millipore membrane.
The millipore filters have 0.65 micron pores.
Contaminating particles are retained on the surface
of the membrane. If a beam of light is directed
through the membrane, part of the light is absorbed
by particles of solid contaminants.
To increase accuracy, and to eliminate any fuel
color effect, two millipore filters are used in series.
The first filter traps the solid contaminants, plus fuel
color effect; the second filter is subjected to clean fuel
and retains only the fuel color effect. Thus, the differ-
ence between light transmission through the two
filters depends only on the amount of solid contami-
nation. By measuring the difference between the
contaminated membrane and the clear membrane, it
is possible to establish the level of contamination in
The steps for preparation and use of the AEL Mk
111 are as follows:
1. Remove the power cable from inside the
instrument cover and connect it to a suitable source
of 110-volt, 60-hertz power. The power cable contains
a ground wire to ground the instrument.
2. Turn the light switch on. The light system
should be allowed to warm up for 2 to 3 minutes
Figure 3-5.AEL Mk III (front view).