until you read zero, you have made the refractometer
ready to compare the FSII in the fuel to the scale inside
the refractometer (fig. 3-13),
9. Open the plastic cover and wipe off the water
from the window and cover.
10. Carefully turn the drain cock so several drops of
liquid can trickle into a clean, dry aluminum dish.
11. Open the hinged plastic cover and place two or
three drops of liquid from the funnel on the window.
Close the cover. Look through the eyepiece and read the
point where the shadow line is on the scale. This gives
you the percentage of FSII by volume. Make a log entry
of your finding. Your readings should read two digits to
the right of the decimal point: for example, .08, .04, .06,
etc. See figure 3-13.
12. Empty the funnel and properly dispose of the
fuel. Clean the equipment with soap and water, and
ensure the equipment is thoroughly clean by rinsing
The minimum use level for USN and USMC air-
craft that require FSII to prevent water-ice formation is
0.03 percent. Currently these aircraft are the S-3, US-3,
and SH-60. All other USN and USMC aircraft do not
require FSII and may use JP-5 or other ap-proved fuel
even if it does not contain FSII.
If the FSII level falls below the 0.03 percent limit,
the appropriate Navy or Marine Corps squadron
commanding officer of a squadron containing the above
aircraft. or his/her designated representative shall be
Transient (USAF, USA, and visiting foreign
military aircraft) crewmembers and pilots will be
notified of FSII levels of 0.07 percent or less.
Care and Maintenance
of the Refractometer
You must use very special care in handling the
refractometer when it is in use and when it is stored. A
very strong possibility of damage exists if the prism is
bumped or the whole unit is dropped. When you clean
the equipment, use a mild soap. NO abrasive POWDER
is to be used, since it scratches the plastic. Do not
submerge the unit when it is being cleaned. If you do
submerge it, fluid may get inside and may affect future
readings. As of now, no repair parts are available but
you can contact the Naval Air Propulsion Center if an
When you use a hydrometer, handle it with care. It
is glass and breaks easily. The hydrometer (fig. 3-14) is
used to measure the specific gravity of petroleum
For standardization, all of your readings will be
converted to 60°F. The American Petroleum Institute
has developed a conversion scale from one temperature
Using standard sample procedures, draw a sample.
Pour enough fuel into a beaker to float the hydrometer.
Take your reading on the scale inside the hydrometer at
the surface of the fuel. Use the conversion chart to note
the temperature of the fuel to correct the reading from
the ambient fuel temperature to the specific gravity at
In a days operation of the fuel lab on some ships
and shore stations, it is common to handle over one
hundred samples a day. To be able to keep track of the
sample results and to maintain good records, a log book
is required for all samples.
When you begin the log book, you should enter the
starting date on the front cover. When the log is full,
enter the ending date. This procedure will help you
locate sample results from the collection of completed
logs. Make your log entries in ink and use only one side
of each page. If you write on both sides of the page, it