TM 55-1510-215-10
area of the material affected. Pages with emergency
1-12. Aircraft Designation System.
markings, which consist of black diagonal lines around
three edges, shall have the vertical bar or change
The designation system prescribed by AR 70-50 is
symbol placed along the outer margins between the text
used in aircraft designations as follows:
and the diagonal lines. Change symbols show current
changes only. A miniature pointing hand symbol is used
to denote a change to an illustration. However, a vertical
EXAMPLE U-21G
line in the outer margin, rather than miniature printing
hands, is utilized when there have been extensive
U
-
Basic mission and type symbol (utility)
changes made to an illustration. Change symbols are
not used to indicate changes in the following:
21 -
Design number
a. Introductory material.
G
-
Series symbol
b. Indexes and tabular data where the change
cannot be identified.
1-13. Use of Words Shall, Will, Should and May.
c. Blank space resulting from the deletion of text,
Within this technical manual the word "shall" is used
an illustration, or a table.
to indicate a mandatory requirement. The word "should"
is used to indicate a nonmandatory but preferred method
d. Correction of minor inaccuracies, such as
of accomplishment. The word "may" is used to indicate
spelling, punctuation, relocation of material, etc., unless
an acceptable method of accomplishment. The word
such correction changes the meaning of instructive
"will" is used to express a declaration of purpose and
information and procedures.
may also be used where simple futurity is required.
1-2
