<s>
The	O
Course	B-Device
Setting	I-Device
Bomb	I-Device
Sight	I-Device
(	O
CSBS	B-Device
)	O
is	O
the	O
canonical	O
vector	O
bombsight	B-Application
,	O
the	O
first	O
practical	O
system	O
for	O
properly	O
accounting	O
for	O
the	O
effects	O
of	O
wind	O
when	O
dropping	O
bombs	O
.	O
</s>
<s>
The	O
CSBS	B-Device
was	O
developed	O
for	O
the	O
Royal	O
Naval	O
Air	O
Service	O
(	O
RNAS	O
)	O
in	O
order	O
to	O
attack	O
submarines	O
and	O
ships	O
.	O
</s>
<s>
It	O
has	O
been	O
called	O
"	O
the	O
most	O
important	O
bomb	B-Application
sight	I-Application
of	O
the	O
war	O
"	O
.	O
</s>
<s>
A	O
US	O
version	O
of	O
the	O
CSBS	B-Device
was	O
used	O
by	O
Billy	O
Mitchell	O
on	O
his	O
famous	O
attack	O
on	O
the	O
Ostfriesland	O
in	O
1921	O
.	O
</s>
<s>
It	O
was	O
eventually	O
replaced	O
in	O
British	O
service	O
by	O
more	O
advanced	O
designs	O
like	O
the	O
Mark	B-Device
XIV	I-Device
bomb	I-Device
sight	I-Device
and	O
the	O
Stabilized	B-Device
Automatic	I-Device
Bomb	I-Device
Sight	I-Device
.	O
</s>
<s>
Other	O
services	O
used	O
vector	O
bombsights	B-Application
throughout	O
the	O
war	O
.	O
</s>
<s>
Prior	O
to	O
the	O
introduction	O
of	O
the	O
CSBS	B-Device
,	O
bombsights	B-Application
were	O
generally	O
very	O
simple	O
systems	O
of	O
limited	O
accuracy	O
suitable	O
only	O
for	O
low-level	O
use	O
.	O
</s>
<s>
In	O
1916	O
,	O
Harry	O
Wimperis	O
started	O
the	O
design	O
of	O
a	O
new	O
bombsight	B-Application
,	O
working	O
in	O
collaboration	O
with	O
Scarff	O
.	O
</s>
<s>
This	O
new	O
Drift	B-Device
Sight	I-Device
included	O
a	O
simple	O
system	O
that	O
greatly	O
eased	O
the	O
measurement	O
of	O
the	O
wind	O
.	O
</s>
<s>
Observing	O
the	O
sideways	O
drift	O
of	O
the	O
aircraft	O
by	O
comparing	O
the	O
motion	O
of	O
objects	O
on	O
the	O
ground	O
to	O
a	O
metal	O
rod	O
along	O
the	O
side	O
of	O
the	O
bombsight	B-Application
,	O
the	O
drift	O
could	O
be	O
seen	O
.	O
</s>
<s>
However	O
,	O
the	O
Drift	B-Device
Sight	I-Device
was	O
still	O
useful	O
only	O
for	O
bomb	O
runs	O
along	O
the	O
wind	O
line	O
.	O
</s>
<s>
The	O
best-known	O
modern	O
example	O
is	O
the	O
E6B	B-Device
,	O
which	O
remains	O
a	O
basic	O
part	O
of	O
every	O
pilot	O
and	O
navigator	O
's	O
toolkit	O
.	O
</s>
<s>
Wimperis	O
decided	O
to	O
attack	O
the	O
calculation	O
problem	O
by	O
incorporating	O
a	O
similar	O
vector	O
calculator	O
directly	O
into	O
the	O
bombsight	B-Application
,	O
combining	O
it	O
with	O
a	O
drift	O
measure	O
similar	O
to	O
the	O
one	O
from	O
the	O
earlier	O
Drift	B-Device
Sight	I-Device
.	O
</s>
<s>
Like	O
the	O
Drift	B-Device
sight	I-Device
,	O
simply	O
taking	O
a	O
measure	O
of	O
the	O
wind	O
using	O
the	O
sight	O
itself	O
provided	O
all	O
of	O
the	O
unknown	O
variables	O
needed	O
to	O
completely	O
calculate	O
the	O
bombing	O
approach	O
.	O
</s>
<s>
Unlike	O
the	O
Drift	B-Device
Sight	I-Device
,	O
the	O
new	O
design	O
not	O
only	O
calculated	O
the	O
effect	O
on	O
the	O
distance	O
the	O
bombs	O
travelled	O
,	O
but	O
also	O
indicated	O
the	O
proper	O
direction	O
to	O
fly	O
to	O
approach	O
the	O
target	O
so	O
the	O
aircraft	O
reached	O
it	O
with	O
no	O
residual	O
sideways	O
motion	O
–	O
thereby	O
cancelling	O
any	O
drift	O
no	O
matter	O
the	O
approach	O
direction	O
.	O
</s>
<s>
His	O
new	O
Course	B-Device
Setting	I-Device
Bomb	I-Device
Sight	I-Device
featured	O
a	O
large	O
compass	B-Language
at	O
the	O
rear	O
that	O
could	O
be	O
used	O
for	O
making	O
general	O
calculations	O
of	O
wind	O
speed	O
or	O
solving	O
navigational	O
problems	O
.	O
</s>
<s>
In	O
most	O
cases	O
these	O
could	O
be	O
ignored	O
;	O
the	O
bomb	O
aimer	O
dialled	O
in	O
the	O
wind	O
direction	O
on	O
the	O
compass	B-Language
,	O
then	O
wind	O
speed	O
,	O
airspeed	O
and	O
altitude	O
on	O
different	O
knobs	O
.	O
</s>
<s>
Through	O
these	O
calculations	O
the	O
CSBS	B-Device
allowed	O
bombing	O
from	O
any	O
direction	O
,	O
freeing	O
the	O
aircraft	O
from	O
the	O
wind	O
line	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
In	O
testing	O
in	O
December	O
1917	O
at	O
the	O
Scilly	O
Isles	O
air	O
station	O
,	O
in	O
eight	O
bomb	O
runs	O
the	O
CSBS	B-Device
scored	O
two	O
direct	O
hits	O
,	O
and	O
near-misses	O
on	O
all	O
six	O
other	O
runs	O
.	O
</s>
<s>
In	O
the	O
post-war	O
era	O
,	O
work	O
on	O
new	O
bombsights	B-Application
was	O
seriously	O
curtailed	O
,	O
and	O
little	O
new	O
development	O
had	O
taken	O
place	O
by	O
1930	O
.	O
</s>
<s>
Several	O
minor	O
variations	O
of	O
the	O
CSBS	B-Device
had	O
been	O
introduced	O
during	O
this	O
period	O
to	O
adapt	O
to	O
higher	O
speeds	O
,	O
higher	O
or	O
lower	O
altitudes	O
,	O
and	O
new	O
types	O
of	O
bombs	O
.	O
</s>
<s>
At	O
low	O
speeds	O
and	O
altitudes	O
the	O
time	O
between	O
drop	O
and	O
impact	O
was	O
too	O
short	O
for	O
the	O
bombs	O
to	O
reach	O
terminal	B-Application
velocity	I-Application
so	O
the	O
trajectory	O
of	O
the	O
bombs	O
was	O
roughly	O
parabolic	O
.	O
</s>
<s>
The	O
trail	O
adjustment	O
,	O
set	O
by	O
dialling	O
in	O
the	O
measured	O
terminal	B-Application
velocity	I-Application
for	O
the	O
bombs	O
being	O
dropped	O
,	O
used	O
a	O
cam	B-Data_Structure
to	O
move	O
the	O
height	O
bar	O
forward	O
away	O
from	O
the	O
vertical	O
,	O
reducing	O
the	O
range	O
angle	O
and	O
thereby	O
reducing	O
the	O
range	O
to	O
account	O
for	O
this	O
effect	O
.	O
</s>
<s>
In	O
the	O
mid-1930s	O
,	O
the	O
basic	O
CSBS	B-Device
concept	O
was	O
largely	O
universal	O
for	O
production	O
bombsights	B-Application
.	O
</s>
<s>
During	O
its	O
development	O
prior	O
to	O
the	O
opening	O
of	O
World	O
War	O
II	O
,	O
the	O
CSBS	B-Device
added	O
several	O
new	O
features	O
.	O
</s>
<s>
Prior	O
to	O
the	O
war	O
a	O
major	O
redesign	O
of	O
the	O
CSBS	B-Device
was	O
underway	O
.	O
</s>
<s>
The	O
calculator	O
and	O
wind	O
drift	O
settings	O
,	O
formerly	O
mounted	O
on	O
top	O
and	O
in	O
front	O
of	O
the	O
large	O
compass	B-Language
at	O
the	O
rear	O
of	O
the	O
earlier	O
models	O
,	O
was	O
moved	O
to	O
the	O
left	O
side	O
of	O
the	O
device	O
and	O
changed	O
in	O
form	O
to	O
make	O
it	O
smaller	O
as	O
well	O
.	O
</s>
<s>
The	O
compass	B-Language
,	O
no	O
longer	O
containing	O
pointers	O
and	O
dials	O
,	O
was	O
replaced	O
with	O
a	O
smaller	O
unit	O
.	O
</s>
<s>
The	O
result	O
was	O
a	O
version	O
of	O
the	O
CSBS	B-Device
that	O
was	O
much	O
smaller	O
than	O
earlier	O
versions	O
.	O
</s>
<s>
Thus	O
the	O
older	O
versions	O
of	O
the	O
CSBS	B-Device
soldiered	O
on	O
long	O
after	O
they	O
were	O
due	O
to	O
be	O
replaced	O
,	O
and	O
remained	O
the	O
primary	O
British	O
bombsights	B-Application
into	O
1942	O
.	O
</s>
<s>
Another	O
problem	O
with	O
all	O
of	O
the	O
existing	O
CSBS	B-Device
designs	O
was	O
that	O
it	O
could	O
only	O
be	O
read	O
correctly	O
with	O
the	O
aircraft	O
absolutely	O
level	O
.	O
</s>
<s>
The	O
biplane	O
bombers	O
the	O
CSBS	B-Device
had	O
been	O
developed	O
for	O
had	O
the	O
ability	O
to	O
slip-turn	O
using	O
the	O
rudder	O
only	O
,	O
which	O
made	O
it	O
simple	O
for	O
the	O
pilot	O
to	O
adjust	O
their	O
heading	O
without	O
affecting	O
the	O
aim	O
too	O
much	O
.	O
</s>
<s>
In	O
the	O
aftermath	O
of	O
the	O
Wilhelmshaven	O
raid	O
on	O
3	O
September	O
1939	O
,	O
it	O
was	O
found	O
that	O
the	O
lengthy	O
setup	O
and	O
bomb	O
run	O
demanded	O
by	O
the	O
CSBS	B-Device
made	O
its	O
aircraft	O
extremely	O
vulnerable	O
to	O
fighters	O
and	O
anti-aircraft	O
artillery	O
.	O
</s>
<s>
At	O
a	O
pre-arranged	O
meeting	O
on	O
22	O
December	O
1939	O
,	O
Air	O
Chief	O
Marshal	O
Sir	O
Edgar	O
Ludlow-Hewitt	O
made	O
a	O
request	O
for	O
a	O
new	O
bombsight	B-Application
that	O
did	O
not	O
require	O
such	O
a	O
long	O
run	O
into	O
the	O
target	O
,	O
and	O
which	O
would	O
allow	O
the	O
aircraft	O
to	O
manoeuvre	O
throughout	O
the	O
bomb	O
run	O
.	O
</s>
<s>
The	O
solution	O
to	O
this	O
problem	O
was	O
well	O
understood	O
within	O
the	O
industry	O
:	O
use	O
gyroscopes	O
to	O
provide	O
a	O
level	O
platform	O
to	O
mount	O
the	O
bombsight	B-Application
so	O
it	O
did	O
not	O
move	O
relative	O
to	O
the	O
ground	O
even	O
if	O
the	O
aircraft	O
moved	O
.	O
</s>
<s>
However	O
,	O
the	O
large	O
physical	O
size	O
of	O
the	O
CSBS	B-Device
series	O
,	O
especially	O
the	O
long	O
drift	O
bar	O
,	O
made	O
it	O
difficult	O
to	O
mount	O
successfully	O
on	O
a	O
platform	O
.	O
</s>
<s>
Instead	O
,	O
the	O
bomb	O
aimer	O
had	O
to	O
use	O
manual	O
slide	O
rule	O
calculators	O
to	O
find	O
the	O
drift	O
and	O
bombing	O
angles	O
,	O
and	O
then	O
set	O
the	O
bombsight	B-Application
to	O
these	O
values	O
.	O
</s>
<s>
The	O
bombsight	B-Application
was	O
unable	O
to	O
quickly	O
adapt	O
to	O
changes	O
in	O
direction	O
or	O
altitude	O
,	O
and	O
in	O
this	O
case	O
was	O
even	O
slower	O
to	O
calculate	O
such	O
changes	O
.	O
</s>
<s>
It	O
was	O
planned	O
that	O
many	O
of	O
these	O
problems	O
would	O
be	O
solved	O
on	O
the	O
Automatic	O
Bomb	B-Application
Sight	I-Application
(	O
ABS	O
)	O
,	O
which	O
had	O
been	O
under	O
development	O
from	O
before	O
the	O
war	O
,	O
and	O
used	O
very	O
simple	O
inputs	O
from	O
the	O
bomb	O
aimer	O
to	O
carry	O
out	O
all	O
the	O
needed	O
calculations	O
.	O
</s>
<s>
Unfortunately	O
,	O
the	O
ABS	O
was	O
even	O
larger	O
than	O
the	O
CSBS	B-Device
,	O
and	O
the	O
demands	O
for	O
new	O
bombsights	B-Application
to	O
be	O
stabilized	O
would	O
make	O
it	O
even	O
larger	O
and	O
meant	O
it	O
would	O
take	O
some	O
time	O
before	O
it	O
could	O
be	O
brought	O
into	O
service	O
.	O
</s>
<s>
Turning	O
the	O
dials	O
drove	O
the	O
machine	O
to	O
calculate	O
the	O
correct	O
angles	O
,	O
as	O
on	O
the	O
earlier	O
CSBS	B-Device
models	O
,	O
but	O
then	O
fed	O
them	O
directly	O
into	O
a	O
remote	O
sighting	O
unit	O
,	O
the	O
sighting	O
head	O
.	O
</s>
<s>
Together	O
,	O
these	O
changes	O
dramatically	O
simplified	O
the	O
task	O
of	O
maintaining	O
an	O
accurate	O
bombsight	B-Application
setting	O
.	O
</s>
<s>
It	O
did	O
not	O
offer	O
the	O
level	O
of	O
accuracy	O
of	O
tachometric	B-Device
bombsights	I-Device
like	O
the	O
Norden	B-Device
or	O
ABS	O
,	O
but	O
for	O
night	O
area	O
bombing	O
from	O
medium	O
altitude	O
as	O
practiced	O
by	O
RAF	O
Bomber	O
Command	O
this	O
was	O
not	O
an	O
issue	O
.	O
</s>
<s>
For	O
this	O
role	O
,	O
the	O
Automatic	O
Bomb	B-Application
Sight	I-Application
was	O
dusted	O
off	O
and	O
mounted	O
to	O
new	O
stabilization	O
platform	O
,	O
producing	O
the	O
Stabilized	B-Device
Automatic	I-Device
Bomb	I-Device
Sight	I-Device
.	O
</s>
<s>
The	O
bombsight	B-Application
problem	O
is	O
the	O
need	O
to	O
determine	O
the	O
exact	O
spot	O
in	O
the	O
air	O
where	O
the	O
bombs	O
should	O
be	O
dropped	O
to	O
hit	O
a	O
target	O
on	O
the	O
ground	O
.	O
</s>
<s>
The	O
bombsight	B-Application
is	O
then	O
set	O
to	O
that	O
angle	O
,	O
and	O
the	O
bomb	O
aimer	O
drops	O
the	O
bombs	O
when	O
the	O
target	O
passes	O
through	O
the	O
sights	O
.	O
</s>
<s>
Calculating	O
the	O
proper	O
drift	O
angle	O
is	O
a	O
simple	O
task	O
of	O
basic	O
vector	O
addition	O
,	O
and	O
is	O
commonly	O
carried	O
out	O
on	O
a	O
circular	O
slide	O
rule	O
like	O
the	O
E6B	B-Device
.	O
</s>
<s>
The	O
CSBS	B-Device
solved	O
this	O
problem	O
by	O
reproducing	O
the	O
basic	O
vector	O
math	O
in	O
a	O
mechanical	O
system	O
.	O
</s>
<s>
At	O
the	O
rear	O
of	O
the	O
CSBS	B-Device
is	O
a	O
large	O
compass	B-Language
with	O
a	O
slip	O
ring	O
carrying	O
a	O
rotating	O
compass	B-Language
rose	O
known	O
as	O
the	O
bearing	O
plate	O
.	O
</s>
<s>
On	O
early	O
models	O
,	O
rotating	O
the	O
compass	B-Language
face	O
also	O
rotated	O
a	O
shaft	O
that	O
ran	O
forward	O
under	O
the	O
main	O
body	O
of	O
the	O
bombsight	B-Application
and	O
through	O
a	O
metal	O
tube	O
running	O
out	O
the	O
lower	O
front	O
of	O
the	O
main	O
housing	O
.	O
</s>
<s>
On	O
later	O
models	O
,	O
a	O
large	O
knob	O
known	O
as	O
the	O
milled	O
head	O
was	O
placed	O
directly	O
behind	O
the	O
compass	B-Language
and	O
drove	O
this	O
shaft	O
independently	O
of	O
the	O
compass	B-Language
face	O
,	O
allowing	O
calculations	O
to	O
be	O
carried	O
out	O
without	O
changing	O
the	O
bombsight	B-Application
settings	O
.	O
</s>
<s>
Connected	O
to	O
and	O
extending	O
from	O
the	O
front	O
of	O
the	O
main	O
bombsight	B-Application
housing	O
is	O
the	O
drift	O
bar	O
,	O
normally	O
forming	O
over	O
half	O
the	O
overall	O
length	O
of	O
the	O
device	O
.	O
</s>
<s>
The	O
drift	O
bar	O
is	O
pivoted	O
at	O
its	O
base	O
,	O
just	O
in	O
front	O
of	O
the	O
compass	B-Language
area	O
,	O
allowing	O
it	O
to	O
rotate	O
to	O
the	O
left	O
or	O
right	O
.	O
</s>
<s>
The	O
last	O
is	O
the	O
airspeed	O
of	O
the	O
bomber	O
–	O
its	O
absolute	O
direction	O
can	O
be	O
ignored	O
if	O
everything	O
is	O
measured	O
in	O
terms	O
of	O
the	O
direction	O
to	O
the	O
target	O
,	O
as	O
in	O
the	O
case	O
of	O
the	O
CSBS	B-Device
.	O
</s>
<s>
The	O
bombsight	B-Application
solution	O
is	O
now	O
almost	O
complete	O
,	O
having	O
calculated	O
the	O
ground	O
speed	O
and	O
zeroed	O
out	O
any	O
sideways	O
drift	O
.	O
</s>
<s>
The	O
CSBS	B-Device
solves	O
this	O
through	O
the	O
height	O
bar	O
,	O
which	O
extends	O
vertically	O
from	O
the	O
center	O
of	O
the	O
device	O
where	O
the	O
compass	B-Language
section	O
meets	O
the	O
drift	O
bar	O
.	O
</s>
<s>
Although	O
a	O
bomb	O
's	O
trajectory	O
is	O
roughly	O
parabolic	O
,	O
when	O
the	O
bomb	O
is	O
dropped	O
from	O
high	O
altitudes	O
it	O
may	O
reach	O
terminal	B-Application
velocity	I-Application
before	O
hitting	O
the	O
ground	O
.	O
</s>
<s>
II	O
version	O
of	O
the	O
CSBS	B-Device
,	O
which	O
rotated	O
the	O
height	O
bar	O
forward	O
.	O
</s>
<s>
Later	O
models	O
of	O
the	O
CSBS	B-Device
,	O
starting	O
with	O
the	O
Mk	O
.	O
</s>
<s>
VII	O
,	O
used	O
a	O
cam	B-Data_Structure
that	O
was	O
driven	O
by	O
both	O
the	O
altitude	O
setting	O
and	O
the	O
trail	O
screw	O
in	O
order	O
to	O
automate	O
the	O
calculation	O
of	O
this	O
effect	O
.	O
</s>
<s>
Additionally	O
,	O
each	O
aircraft	O
has	O
a	O
slightly	O
different	O
way	O
of	O
measuring	O
altitude	O
that	O
needs	O
adjustment	O
,	O
the	O
CSBS	B-Device
accounted	O
for	O
this	O
effect	O
by	O
including	O
two	O
altitude	O
scales	O
,	O
a	O
linear	O
scale	O
of	O
altitude	O
in	O
orange	O
on	O
the	O
right	O
side	O
of	O
the	O
bar	O
,	O
and	O
any	O
number	O
of	O
white	O
scales	O
on	O
the	O
back	O
that	O
could	O
be	O
clipped	O
onto	O
the	O
sight	O
.	O
</s>
<s>
The	O
operation	O
of	O
the	O
CSBS	B-Device
is	O
best	O
understood	O
using	O
a	O
simple	O
example	O
.	O
</s>
<s>
On	O
the	O
CSBS	B-Device
each	O
of	O
these	O
arrows	O
has	O
a	O
mechanical	O
equivalent	O
in	O
the	O
bombsight	B-Application
.	O
</s>
<s>
The	O
direction	O
of	O
the	O
yellow	O
arrow	O
is	O
that	O
of	O
the	O
aircraft	O
itself	O
,	O
represented	O
in	O
the	O
bombsight	B-Application
by	O
its	O
mounting	O
to	O
the	O
aircraft	O
fuselage	O
.	O
</s>
<s>
When	O
all	O
of	O
the	O
adjustments	O
are	O
complete	O
,	O
the	O
bombsight	B-Application
and	O
airspeed	O
shaft	O
mechanically	O
represent	O
the	O
yellow	O
arrow	O
,	O
the	O
wind	O
bar	O
represents	O
the	O
blue	O
arrow	O
,	O
and	O
the	O
green	O
arrow	O
is	O
formed	O
by	O
the	O
drift	O
wires	O
providing	O
direction	O
,	O
and	O
the	O
foresight	O
is	O
positioned	O
at	O
the	O
tip	O
of	O
the	O
green	O
arrow	O
.	O
</s>
<s>
Once	O
set	O
,	O
the	O
bomb	O
aimer	O
uses	O
the	O
rear	O
sights	O
,	O
or	O
any	O
other	O
convenient	O
part	O
of	O
the	O
bombsight	B-Application
,	O
as	O
a	O
reference	O
location	O
and	O
spots	O
past	O
them	O
through	O
the	O
drift	O
wires	O
.	O
</s>
<s>
Although	O
the	O
CSBS	B-Device
automated	O
the	O
calculation	O
of	O
the	O
effects	O
of	O
the	O
wind	O
,	O
it	O
did	O
not	O
automate	O
the	O
measurement	O
of	O
the	O
wind	O
itself	O
.	O
</s>
<s>
The	O
bombsight	B-Application
manual	O
describes	O
several	O
ways	O
to	O
do	O
this	O
.	O
</s>
<s>
One	O
is	O
an	O
adaptation	O
of	O
the	O
method	O
used	O
with	O
the	O
Drift	B-Device
Sight	I-Device
.	O
</s>
<s>
The	O
bearing	O
plate	O
is	O
rotated	O
to	O
the	O
compass	B-Language
heading	O
and	O
locked	O
,	O
thereby	O
recording	O
the	O
wind	O
direction	O
for	O
future	O
reference	O
.	O
</s>
<s>
A	O
later	O
modification	O
to	O
the	O
CSBS	B-Device
,	O
and	O
supplied	O
with	O
most	O
of	O
the	O
Mk	O
.	O
</s>
<s>
This	O
was	O
normally	O
stowed	O
folded	O
against	O
the	O
back	O
of	O
the	O
height	O
bar	O
,	O
but	O
could	O
be	O
rotated	O
down	O
and	O
to	O
the	O
rear	O
to	O
lie	O
over	O
the	O
compass	B-Language
.	O
</s>
<s>
A	O
small	O
ring	O
on	O
the	O
right	O
side	O
of	O
the	O
cursor	O
was	O
used	O
to	O
accurately	O
place	O
markings	O
on	O
the	O
compass	B-Language
using	O
the	O
grease	O
pencil	O
.	O
</s>
<s>
The	O
face	O
of	O
the	O
compass	B-Language
was	O
then	O
rotated	O
to	O
the	O
aircraft	O
heading	O
,	O
which	O
caused	O
the	O
dot	O
to	O
move	O
.	O
</s>
<s>
The	O
bearing	O
plate	O
was	O
rotated	O
to	O
match	O
the	O
compass	B-Language
heading	O
of	O
each	O
leg	O
,	O
and	O
the	O
cursor	O
was	O
moved	O
along	O
the	O
bar	O
to	O
draw	O
a	O
line	O
on	O
the	O
bearing	O
plate	O
along	O
that	O
direction	O
.	O
</s>
<s>
Using	O
the	O
drift	O
angle	O
measured	O
from	O
the	O
auxiliary	O
drift	O
bar	O
,	O
the	O
compass	B-Language
was	O
rotated	O
to	O
that	O
drift	O
angle	O
,	O
and	O
the	O
cursor	O
moved	O
so	O
it	O
lay	O
above	O
the	O
center	O
of	O
the	O
triangle	O
.	O
</s>
<s>
Levelling	O
the	O
bombsight	B-Application
was	O
required	O
before	O
any	O
use	O
.	O
</s>
<s>
The	O
bombsight	B-Application
included	O
two	O
spirit	O
levels	O
for	O
this	O
,	O
and	O
was	O
mounted	O
to	O
a	O
friction-set	O
ball	O
so	O
it	O
could	O
be	O
rotated	O
in	O
any	O
direction	O
.	O
</s>
<s>
The	O
CSBS	B-Device
accounted	O
for	O
this	O
through	O
the	O
use	O
of	O
the	O
enemy	O
vector	O
mechanism	O
or	O
fourth	O
vector	O
,	O
which	O
was	O
similar	O
to	O
the	O
wind	O
mechanism	O
but	O
operated	O
at	O
the	O
origin	O
of	O
the	O
drift	O
bar	O
instead	O
of	O
a	O
point	O
located	O
along	O
it	O
.	O
</s>
