1-2 Change 3
for aircraft equipped with the Improved Constant Area
Exhaust Stacks. The designator symbol IR identifies
text, illustrations, and performance data for aircraft
equipped with the Infra Red Reducing Exhaust Stacks.
Data which has no icons applies to both.
1-11. AIRCRAFT DESIGNATION SYSTEM.
The designation system prescribed by AR 70-50 is
used in aircraft designations as follows:
R - Modified mission symbol (Reconnaissance)
C - Basic mission and type symbol (Cargo)
12 - Design number
N - Series symbol
1-12. USE OF WORDS SHALL, SHOULD, AND MAY.
Within this technical manual the word shall is used to in-
dicate a mandatory requirement. The word should is
used to indicate a nonmandatory but preferred method
of accomplishment. The word may is used to indicate
an acceptable method of accomplishment.
1-13. PLACARD ITEMS.
Where applicable, placarded items (switches, control,
etc.) are shown throughout this manual in capital letters.