Douglas A-4M - Drag Count Index System

Section Xl
Par t
1
A bbreviation
p
pSi
R CR
RNI
RPM
SL
Sid
T
T
o
TAS
V ol
Wt
6 or p I p 0
p
11-4
NAVAIR 01- 4 0AVM - l
Definition
Static a tm o spheri c pres-
sure at any al titude
Static atmos pheric pres-
sure at se a level r CA D
stand . trd day = 29. 92 inches
of mercu r y
Pounds pe r square inch
Runway
co ndition reading
R eynolds number index
Revolutions
per minute
(Engine
speed )
Sea
level
Standar d
Static absol ute tempera-
tur e at any altitude
Static abso lute temper a-
ture at sea level ICAD
sta ndard day =
288.2 degrees K el vin
True a ir speed
V olume
Weight
Delta - change in (e. g.
gr
oss weight)
Delta -
ratio of sta tic a ir
pressure to ICAD stan dard
sea level st atic a ir
pr essu r e
Coeffi
cient of rolling
friction
Rho - density of a tmos-
phere in sLugs per foot at
any altitude
Rh o - d ensity of atmos-
pher e at sea leve l ICAO
standa rd day = 0.0 02378
slugs per foot
Abbr
eviati on Definition
Sigma - ratio of density at
any alti tude to density at
sea level. ICAO standard
day
Thet a - r atio of absolute
temper a ture or any a lti -
tude to a bs olute tempe r a-
ture at sea level; ICAO
standa rd day
DRAG COUNT INDEX SYSTEM
The la rge v;lr iety of extern al store loadings per-
mitted on the A- 4M aircraft requires a method of
dat a p re sentation that ca n refl ec t a var iable exter nal
configur at ion. This method is called the Dr ag Count
Index
Sy stem .
In the Dr
ag Count Index System. each ilem of the ex-
te r nal store configur ation. such as a bomb. ta rue or
pylon. Is ass igned a dr ag number value t hat depends
up on the size and shape of the item and its location
on the
air cr aft. The s um of the se individu al drag
numbe rs. f or a particul ar loading. reflect s the drag
index for t hat configuration. This index. when ap-
plied to the pe rf o rm ance charts. defines the perfor-
mance of that configuration.
Some of the individual drag numbers used for deter-
mining drag Indexes are shown In figure II-I. and a
comple
le listing is made in NAV AlR Ol -40AV-1T.
Note that the dr ag nu
mbers for a given sto re depend
on the
store station on which they a rc ca rr ied. The
weights of t ypical external stores. pylons, tanks. and
ada pters ar e included in figw' e II - I. The drag of the
clean aircraft includes the dr ag of the cen terline
pylon. upper av ionics pod. inflight fueling probe. a nd
drag chute. but no guns or wing pylons.
SAMPLE PROBLEM
Drag Indexes
(For
figure 11-1)
As sume the exter nal configuration consists of a 300-
gallon
Aero 1 -0 fuel tank on the cente rlin e pylon. a
6x300
-po und MK 81 Sn.'1.keye bomb c l uster on e;lch
inboar d wing
py lon, and a 530-pound MK 82 bomb on
each outboa rd wing pylon.