<s>
A	O
bombsight	B-Application
is	O
a	O
device	O
used	O
by	O
military	O
aircraft	O
to	O
drop	O
bombs	B-Device
accurately	O
.	O
</s>
<s>
Bombsights	B-Application
,	O
a	O
feature	O
of	O
combat	O
aircraft	O
since	O
World	O
War	O
I	O
,	O
were	O
first	O
found	O
on	O
purpose-designed	O
bomber	O
aircraft	O
and	O
then	O
moved	O
to	O
fighter-bombers	O
and	O
modern	O
tactical	O
aircraft	O
as	O
those	O
aircraft	O
took	O
up	O
the	O
brunt	O
of	O
the	O
bombing	O
role	O
.	O
</s>
<s>
A	O
bombsight	B-Application
has	O
to	O
estimate	O
the	O
path	O
the	O
bomb	B-Device
will	O
take	O
after	O
release	O
from	O
the	O
aircraft	O
.	O
</s>
<s>
The	O
two	O
primary	O
forces	O
during	O
its	O
fall	O
are	O
gravity	O
and	O
air	O
drag	O
,	O
which	O
make	O
the	O
path	O
of	O
the	O
bomb	B-Device
through	O
the	O
air	O
roughly	O
parabolic	O
.	O
</s>
<s>
There	O
are	O
additional	O
factors	O
such	O
as	O
changes	O
in	O
air	O
density	O
and	O
wind	O
that	O
may	O
be	O
considered	O
,	O
but	O
they	O
are	O
concerns	O
only	O
for	O
bombs	B-Device
that	O
spend	O
a	O
significant	O
portion	O
of	O
a	O
minute	O
falling	O
through	O
the	O
air	O
.	O
</s>
<s>
Those	O
effects	O
can	O
be	O
minimized	O
by	O
reducing	O
the	O
fall	O
time	O
by	O
low-level	O
bombing	O
or	O
by	O
increasing	O
the	O
speed	O
of	O
the	O
bombs	B-Device
.	O
</s>
<s>
Those	O
effects	O
are	O
combined	O
in	O
the	O
dive	B-Application
bomber	I-Application
.	O
</s>
<s>
That	O
has	O
led	O
to	O
a	O
series	O
of	O
increasingly	O
sophisticated	O
bombsight	B-Application
designs	O
dedicated	O
to	O
high-altitude	O
level	O
bombing	O
.	O
</s>
<s>
Bombsights	B-Application
were	O
first	O
used	O
before	O
World	O
War	O
I	O
and	O
have	O
since	O
gone	O
through	O
several	O
major	O
revisions	O
.	O
</s>
<s>
These	O
early	O
systems	O
were	O
replaced	O
by	O
the	O
vector	O
bombsights	B-Application
,	O
which	O
added	O
the	O
ability	O
to	O
measure	O
and	O
adjust	O
for	O
winds	O
.	O
</s>
<s>
Vector	O
bombsights	B-Application
were	O
useful	O
for	O
altitudes	O
up	O
to	O
about	O
3,000	O
m	O
and	O
speeds	O
up	O
to	O
about	O
300km/h	O
.	O
</s>
<s>
In	O
the	O
1930s	O
,	O
mechanical	B-Device
computers	I-Device
with	O
the	O
performance	O
needed	O
to	O
"	O
solve	O
"	O
the	O
equations	O
of	O
motion	O
started	O
to	O
be	O
incorporated	O
into	O
the	O
new	O
tachometric	B-Device
bombsights	I-Device
,	O
the	O
most	O
famous	O
of	O
which	O
is	O
the	O
Norden	B-Device
.	O
</s>
<s>
Then	O
,	O
in	O
World	O
War	O
II	O
,	O
tachometric	B-Device
bombsights	I-Device
were	O
often	O
combined	O
with	O
radar	B-Application
systems	I-Application
to	O
allow	O
accurate	O
bombing	O
through	O
clouds	O
or	O
at	O
night	O
.	O
</s>
<s>
When	O
postwar	O
studies	O
demonstrated	O
that	O
bomb	B-Device
accuracy	O
was	O
roughly	O
equal	O
either	O
optically	O
or	O
radar-guided	O
,	O
optical	O
bombsights	B-Application
were	O
generally	O
removed	O
and	O
the	O
role	O
passed	O
to	O
dedicated	O
radar	B-Application
bombsights	B-Application
.	O
</s>
<s>
Finally	O
,	O
especially	O
since	O
the	O
1960s	O
,	O
fully	O
computerized	O
bombsights	B-Application
were	O
introduced	O
,	O
which	O
combined	O
the	O
bombing	O
with	O
long-range	O
navigation	O
and	O
mapping	O
.	O
</s>
<s>
Modern	O
aircraft	O
do	O
not	O
have	O
a	O
bombsight	B-Application
but	O
use	O
highly	O
computerized	O
systems	O
that	O
combine	O
bombing	O
,	O
gunnery	O
,	O
missile	O
fire	O
and	O
navigation	O
into	O
a	O
single	O
head-up	B-Application
display	I-Application
.	O
</s>
<s>
The	O
systems	O
have	O
the	O
performance	O
to	O
calculate	O
the	O
bomb	B-Device
trajectory	O
in	O
real	B-General_Concept
time	I-General_Concept
,	O
as	O
the	O
aircraft	O
manoeuvres	O
,	O
and	O
add	O
the	O
ability	O
to	O
adjust	O
for	O
weather	O
,	O
relative	O
altitude	O
,	O
relative	O
speeds	O
for	O
moving	O
targets	O
and	O
climb	O
or	O
dive	O
angle	O
.	O
</s>
<s>
That	O
makes	O
them	O
useful	O
both	O
for	O
level	O
bombing	O
,	O
as	O
in	O
earlier	O
generations	O
,	O
and	O
tactical	O
missions	O
,	O
which	O
used	O
to	O
bomb	B-Device
by	O
eye	O
.	O
</s>
<s>
The	O
drag	O
on	O
a	O
bomb	B-Device
for	O
a	O
given	O
air	O
density	O
and	O
angle	O
of	O
attack	O
is	O
proportional	O
to	O
the	O
relative	O
air	O
speed	O
squared	O
.	O
</s>
<s>
To	O
start	O
with	O
,	O
consider	O
only	O
the	O
vertical	O
motion	O
of	O
a	O
bomb	B-Device
.	O
</s>
<s>
In	O
this	O
direction	O
,	O
the	O
bomb	B-Device
will	O
be	O
subject	O
to	O
two	O
primary	O
forces	O
,	O
gravity	O
and	O
drag	O
,	O
the	O
first	O
constant	O
,	O
and	O
the	O
second	O
varying	O
with	O
the	O
square	O
of	O
velocity	O
.	O
</s>
<s>
For	O
an	O
aircraft	O
flying	O
straight	O
and	O
level	O
,	O
the	O
initial	O
vertical	O
velocity	O
of	O
the	O
bomb	B-Device
will	O
be	O
zero	O
,	O
which	O
means	O
it	O
will	O
also	O
have	O
zero	O
vertical	O
drag	O
.	O
</s>
<s>
Gravity	O
will	O
accelerate	O
the	O
bomb	B-Device
downwards	O
,	O
and	O
as	O
its	O
velocity	O
increases	O
so	O
does	O
the	O
drag	O
force	O
.	O
</s>
<s>
At	O
some	O
point	O
(	O
as	O
speed	O
and	O
air	O
density	O
increase	O
)	O
,	O
the	O
force	O
of	O
drag	O
will	O
become	O
equal	O
to	O
the	O
force	O
of	O
gravity	O
,	O
and	O
the	O
bomb	B-Device
will	O
reach	O
terminal	B-Application
velocity	I-Application
.	O
</s>
<s>
As	O
the	O
air	O
drag	O
varies	O
with	O
air	O
density	O
,	O
and	O
thus	O
altitude	O
,	O
the	O
terminal	B-Application
velocity	I-Application
will	O
decrease	O
as	O
the	O
bomb	B-Device
falls	O
.	O
</s>
<s>
Generally	O
,	O
the	O
bomb	B-Device
will	O
slow	O
as	O
it	O
reaches	O
lower	O
altitudes	O
where	O
the	O
air	O
is	O
denser	O
,	O
but	O
the	O
relationship	O
is	O
complex	O
.	O
</s>
<s>
At	O
the	O
instant	O
it	O
leaves	O
the	O
shackles	O
,	O
the	O
bomb	B-Device
carries	O
the	O
forward	O
speed	O
of	O
the	O
aircraft	O
with	O
it	O
.	O
</s>
<s>
This	O
momentum	B-Algorithm
is	O
countered	O
solely	O
by	O
drag	O
,	O
which	O
starts	O
to	O
slow	O
the	O
forward	O
motion	O
.	O
</s>
<s>
If	O
the	O
bomb	B-Device
were	O
not	O
subject	O
to	O
drag	O
,	O
its	O
path	O
would	O
be	O
purely	O
ballistic	O
and	O
it	O
would	O
impact	O
at	O
an	O
easily	O
calculable	O
point	O
,	O
the	O
vacuum	O
range	O
.	O
</s>
<s>
The	O
difference	O
between	O
the	O
vacuum	O
range	O
and	O
actual	O
range	O
is	O
known	O
as	O
the	O
trail	O
because	O
the	O
bomb	B-Device
appears	O
to	O
trail	O
behind	O
the	O
aircraft	O
as	O
it	O
falls	O
.	O
</s>
<s>
The	O
trail	O
and	O
range	O
differ	O
for	O
different	O
bombs	B-Device
due	O
to	O
their	O
individual	O
aerodynamics	O
and	O
typically	O
have	O
to	O
be	O
measured	O
on	O
a	O
bombing	O
range	O
.	O
</s>
<s>
The	O
main	O
problem	O
in	O
completely	O
separating	O
the	O
motion	O
into	O
vertical	O
and	O
horizontal	O
components	O
is	O
the	O
terminal	B-Application
velocity	I-Application
.	O
</s>
<s>
Bombs	B-Device
are	O
designed	O
to	O
fly	O
with	O
the	O
nose	O
pointed	O
forward	O
into	O
the	O
relative	O
wind	O
,	O
normally	O
through	O
the	O
use	O
of	O
fins	O
at	O
the	O
back	O
of	O
the	O
bomb	B-Device
.	O
</s>
<s>
The	O
drag	O
depends	O
on	O
the	O
angle	O
of	O
attack	O
of	O
the	O
bomb	B-Device
at	O
any	O
given	O
instant	O
.	O
</s>
<s>
If	O
the	O
bomb	B-Device
is	O
released	O
at	O
low	O
altitudes	O
and	O
speeds	O
the	O
bomb	B-Device
will	O
not	O
reach	O
terminal	B-Application
velocity	I-Application
and	O
its	O
speed	O
will	O
be	O
defined	O
largely	O
by	O
how	O
long	O
the	O
bomb	B-Device
has	O
been	O
falling	O
.	O
</s>
<s>
The	O
wind	O
acts	O
on	O
the	O
bomb	B-Device
through	O
drag	O
and	O
is	O
thus	O
a	O
function	O
of	O
the	O
wind	O
speed	O
.	O
</s>
<s>
This	O
is	O
typically	O
only	O
a	O
fraction	O
of	O
the	O
speed	O
of	O
the	O
bomber	O
or	O
the	O
terminal	B-Application
velocity	I-Application
,	O
so	O
it	O
only	O
becomes	O
a	O
factor	O
if	O
the	O
bomb	B-Device
is	O
dropped	O
from	O
altitudes	O
high	O
enough	O
for	O
this	O
small	O
influence	O
to	O
noticeably	O
affect	O
the	O
bomb	B-Device
's	O
path	O
.	O
</s>
<s>
The	O
bombsight	B-Application
problem	O
is	O
the	O
calculation	O
of	O
the	O
location	O
in	O
space	O
where	O
the	O
bombs	B-Device
should	O
be	O
dropped	O
in	O
order	O
to	O
hit	O
the	O
target	O
when	O
all	O
of	O
the	O
effects	O
noted	O
above	O
are	O
taken	O
into	O
account	O
.	O
</s>
<s>
In	O
the	O
absence	O
of	O
wind	O
,	O
the	O
bombsight	B-Application
problem	O
is	O
fairly	O
simple	O
.	O
</s>
<s>
The	O
impact	O
point	O
is	O
a	O
function	O
of	O
three	O
factors	O
,	O
the	O
aircraft	O
's	O
altitude	O
,	O
its	O
forward	O
speed	O
,	O
and	O
the	O
terminal	B-Application
velocity	I-Application
of	O
the	O
bomb	B-Device
.	O
</s>
<s>
In	O
many	O
early	O
bombsights	B-Application
,	O
the	O
first	O
two	O
inputs	O
were	O
adjusted	O
by	O
separately	O
setting	O
the	O
front	O
and	O
back	O
sights	O
of	O
an	O
iron	O
sight	O
,	O
one	O
for	O
the	O
altitude	O
and	O
the	O
other	O
for	O
the	O
speed	O
.	O
</s>
<s>
Terminal	B-Application
velocity	I-Application
,	O
which	O
extends	O
the	O
fall	O
time	O
,	O
can	O
be	O
accounted	O
for	O
by	O
raising	O
the	O
effective	O
altitude	O
by	O
an	O
amount	O
that	O
is	O
based	O
on	O
the	O
bomb	B-Device
's	O
measured	O
ballistics	O
.	O
</s>
<s>
As	O
the	O
wind	O
can	O
operate	O
in	O
any	O
direction	O
,	O
bombsights	B-Application
generally	O
break	O
the	O
windage	O
into	O
the	O
portions	O
that	O
act	O
along	O
the	O
flight	O
path	O
and	O
across	O
it	O
.	O
</s>
<s>
Bombsights	B-Application
are	O
sighting	O
devices	O
that	O
are	O
pointed	O
in	O
a	O
particular	O
direction	O
,	O
or	O
aimed	O
.	O
</s>
<s>
The	O
bombsight	B-Application
is	O
then	O
set	O
to	O
indicate	O
that	O
angle	O
.	O
</s>
<s>
The	O
bombs	B-Device
are	O
dropped	O
when	O
the	O
target	O
passes	O
through	O
the	O
sights	O
.	O
</s>
<s>
The	O
accuracy	O
of	O
the	O
drop	O
is	O
affected	O
both	O
by	O
inherent	O
problems	O
like	O
the	O
randomness	O
of	O
the	O
atmosphere	O
or	O
bomb	B-Device
manufacture	O
as	O
well	O
as	O
more	O
practical	O
problems	O
like	O
how	O
close	O
to	O
flat	O
and	O
level	O
the	O
aircraft	O
is	O
flying	O
or	O
the	O
accuracy	O
of	O
its	O
instruments	O
.	O
</s>
<s>
These	O
inaccuracies	O
compound	O
over	O
time	O
,	O
so	O
increasing	O
the	O
altitude	O
of	O
the	O
bomb	B-Device
run	O
,	O
thereby	O
increasing	O
the	O
fall	O
time	O
,	O
has	O
a	O
significant	O
impact	O
on	O
the	O
final	O
accuracy	O
of	O
the	O
drop	O
.	O
</s>
<s>
It	O
is	O
useful	O
to	O
consider	O
a	O
single	O
example	O
of	O
a	O
bomb	B-Device
being	O
dropped	O
on	O
a	O
typical	O
mission	O
.	O
</s>
<s>
In	O
this	O
case	O
we	O
will	O
consider	O
the	O
AN-M64	O
500lbs	O
General-Purpose	O
Bomb	B-Device
,	O
widely	O
used	O
by	O
the	O
USAAF	O
and	O
RAF	O
during	O
World	O
War	O
II	O
,	O
with	O
direct	O
counterparts	O
in	O
the	O
armouries	O
of	O
most	O
forces	O
involved	O
.	O
</s>
<s>
Ballistic	O
data	O
on	O
this	O
bomb	B-Device
can	O
be	O
found	O
in	O
"	O
Terminal	O
Ballistic	O
Data	O
,	O
Volume	O
1	O
:	O
Bombing	O
"	O
.	O
</s>
<s>
A	O
wind	O
would	O
be	O
expected	O
to	O
move	O
the	O
bomb	B-Device
about	O
during	O
that	O
time	O
.	O
</s>
<s>
All	O
of	O
these	O
are	O
well	O
within	O
the	O
lethal	O
radius	O
of	O
the	O
bomb	B-Device
.	O
</s>
<s>
The	O
wind	O
affects	O
the	O
accuracy	O
of	O
the	O
bomb	B-Device
in	O
two	O
ways	O
,	O
pushing	O
directly	O
on	O
the	O
bomb	B-Device
while	O
it	O
falls	O
,	O
as	O
well	O
as	O
changing	O
the	O
ground	O
speed	O
of	O
the	O
aircraft	O
before	O
the	O
drop	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
the	O
direct	O
effects	O
on	O
the	O
bomb	B-Device
,	O
a	O
measurement	O
that	O
has	O
a	O
5%	O
error	O
,	O
1.25mph	O
,	O
that	O
would	O
cause	O
a	O
5%	O
error	O
in	O
the	O
drift	O
,	O
which	O
would	O
be	O
17.5feet	O
.	O
</s>
<s>
Over	O
the	O
time	O
of	O
the	O
fall	O
,	O
37	O
seconds	O
,	O
that	O
would	O
result	O
in	O
an	O
error	O
of	O
68feet	O
,	O
which	O
is	O
at	O
the	O
outside	O
limit	O
of	O
the	O
bomb	B-Device
's	O
performance	O
.	O
</s>
<s>
Eliminating	O
this	O
error	O
through	O
the	O
direct	O
measurement	O
of	O
ground	O
speed	O
(	O
instead	O
of	O
calculating	O
it	O
)	O
was	O
a	O
major	O
advance	O
in	O
the	O
tachometric	B-Device
bombsights	I-Device
of	O
the	O
1930s	O
and	O
40s	O
.	O
</s>
<s>
Finally	O
,	O
consider	O
errors	O
of	O
the	O
same	O
5%	O
in	O
the	O
equipment	O
itself	O
,	O
that	O
is	O
,	O
an	O
error	O
of	O
5%	O
in	O
the	O
setting	O
of	O
the	O
range	O
angle	O
,	O
or	O
a	O
similar	O
5%	O
error	O
in	O
the	O
levelling	O
of	O
the	O
aircraft	O
or	O
bombsight	B-Application
.	O
</s>
<s>
Using	O
simple	O
trigonometry	O
,	O
5degrees	O
at	O
20,000	O
feet	O
is	O
approximately	O
1,750	O
feet	O
,	O
an	O
error	O
that	O
would	O
place	O
the	O
bombs	B-Device
far	O
outside	O
their	O
lethal	O
radius	O
.	O
</s>
<s>
Given	O
the	O
seriousness	O
of	O
the	O
problem	O
,	O
systems	O
for	O
automatic	O
levelling	O
of	O
bombsights	B-Application
was	O
a	O
major	O
area	O
of	O
study	O
before	O
World	O
War	O
II	O
,	O
especially	O
in	O
the	O
US	O
.	O
</s>
<s>
All	O
of	O
the	O
calculations	O
needed	O
to	O
predict	O
the	O
path	O
of	O
a	O
bomb	B-Device
can	O
be	O
carried	O
out	O
by	O
hand	O
,	O
with	O
the	O
aid	O
of	O
calculated	O
tables	O
of	O
the	O
bomb	B-Device
ballistics	O
.	O
</s>
<s>
During	O
the	O
early	O
stages	O
of	O
bombsight	B-Application
development	O
,	O
the	O
problem	O
was	O
addressed	O
by	O
reducing	O
the	O
allowable	O
engagement	O
envelope	O
,	O
thereby	O
reducing	O
the	O
need	O
to	O
calculate	O
marginal	O
effects	O
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
recorded	O
examples	O
of	O
such	O
a	O
bombsight	B-Application
was	O
built	O
in	O
1911	O
by	O
Lieutenant	O
Riley	O
E	O
.	O
Scott	O
,	O
of	O
the	O
U.S.	O
Army	O
Coast	O
Artillery	O
Corps	O
.	O
</s>
<s>
In	O
testing	O
at	O
College	O
Park	O
,	O
Maryland	O
,	O
Scott	O
was	O
able	O
to	O
place	O
two	O
18pound	O
bombs	B-Device
within	O
10feet	O
of	O
a	O
4-by-5foot	O
target	O
from	O
a	O
height	O
of	O
400feet	O
.	O
</s>
<s>
In	O
January	O
1912	O
,	O
Scott	O
won	O
$	O
5,000	O
for	O
first	O
place	O
in	O
the	O
Michelin	O
bombing	O
competition	O
at	O
Villacoublay	O
Airfield	O
in	O
France	O
,	O
scoring	O
12	O
hits	O
on	O
a	O
125-by-375foot	O
target	O
with	O
15	O
bombs	B-Device
dropped	O
from	O
800meters	O
.	O
</s>
<s>
In	O
spite	O
of	O
early	O
examples	O
like	O
Scott	O
's	O
prior	O
to	O
the	O
war	O
,	O
during	O
the	O
opening	O
stages	O
of	O
the	O
First	O
World	O
War	O
bombing	O
was	O
almost	O
always	O
carried	O
out	O
by	O
eye	O
,	O
dropping	O
the	O
small	O
bombs	B-Device
by	O
hand	O
when	O
the	O
conditions	O
looked	O
right	O
.	O
</s>
<s>
For	O
higher	O
altitude	O
drops	O
,	O
the	O
effect	O
of	O
wind	O
and	O
bomb	B-Device
trajectory	O
could	O
no	O
longer	O
be	O
ignored	O
.	O
</s>
<s>
One	O
important	O
simplification	O
was	O
to	O
ignore	O
the	O
terminal	B-Application
velocity	I-Application
of	O
the	O
bomb	B-Device
,	O
and	O
calculate	O
its	O
average	O
speed	O
as	O
the	O
square	O
root	O
of	O
the	O
altitude	O
measured	O
in	O
feet	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
bomb	B-Device
dropped	O
from	O
10,000	O
feet	O
would	O
fall	O
at	O
an	O
average	O
rate	O
of	O
400fps	O
,	O
allowing	O
easy	O
calculation	O
of	O
the	O
time	O
to	O
fall	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
fully	O
developed	O
examples	O
of	O
such	O
a	O
sight	O
to	O
see	O
combat	O
was	O
the	O
German	O
Görtz	O
bombsight	B-Application
,	O
developed	O
for	O
the	O
Gotha	O
heavy	O
bombers	O
.	O
</s>
<s>
The	O
bomb	B-Device
aimer	O
then	O
watched	O
the	O
target	O
in	O
the	O
sight	O
until	O
it	O
crossed	O
the	O
pointer	O
,	O
and	O
dropped	O
the	O
bombs	B-Device
.	O
</s>
<s>
Similar	O
bombsights	B-Application
were	O
developed	O
in	O
France	O
and	O
England	O
,	O
notably	O
the	O
Michelin	O
and	O
Central	O
Flying	O
School	O
Number	O
Seven	O
bombsight	B-Application
.	O
</s>
<s>
A	O
great	O
upgrade	O
to	O
the	O
basic	O
concept	O
was	O
introduced	O
by	O
Harry	O
Wimperis	O
,	O
better	O
known	O
for	O
his	O
later	O
role	O
in	O
the	O
development	O
of	O
radar	B-Application
in	O
England	O
.	O
</s>
<s>
In	O
1916	O
he	O
introduced	O
the	O
Drift	B-Device
Sight	I-Device
,	O
which	O
added	O
a	O
simple	O
system	O
for	O
directly	O
measuring	O
the	O
wind	O
speed	O
.	O
</s>
<s>
The	O
bomb	B-Device
aimer	O
would	O
first	O
dial	O
in	O
the	O
altitude	O
and	O
airspeed	O
of	O
the	O
aircraft	O
.	O
</s>
<s>
Doing	O
so	O
rotated	O
a	O
metal	O
bar	O
on	O
the	O
right	O
side	O
of	O
the	O
bombsight	B-Application
so	O
it	O
pointed	O
out	O
from	O
the	O
fuselage	O
.	O
</s>
<s>
Prior	O
to	O
the	O
bomb	B-Device
run	O
,	O
the	O
bomber	O
would	O
fly	O
at	O
right	O
angles	O
to	O
the	O
bomb	B-Device
line	O
,	O
and	O
the	O
bomb	B-Device
aimer	O
would	O
look	O
past	O
the	O
rod	O
to	O
watch	O
the	O
motion	O
of	O
objects	O
on	O
the	O
ground	O
.	O
</s>
<s>
This	O
version	O
was	O
the	O
Drift	B-Device
Sight	I-Device
Mk	O
.	O
</s>
<s>
Variations	O
on	O
the	O
design	O
were	O
common	O
,	O
like	O
the	O
US	O
Estoppey	O
bombsight	B-Application
.	O
</s>
<s>
All	O
of	O
these	O
bombsights	B-Application
shared	O
the	O
problem	O
that	O
they	O
were	O
unable	O
to	O
deal	O
with	O
wind	O
in	O
any	O
direction	O
other	O
than	O
along	O
the	O
path	O
of	O
travel	O
.	O
</s>
<s>
The	O
same	O
calculations	O
would	O
work	O
just	O
as	O
well	O
for	O
bomb	B-Device
trajectories	O
,	O
with	O
some	O
minor	O
adjustments	O
to	O
account	O
for	O
the	O
changing	O
velocities	O
as	O
the	O
bombs	B-Device
fell	O
.	O
</s>
<s>
Even	O
as	O
the	O
Drift	B-Device
Sight	I-Device
was	O
being	O
introduced	O
,	O
Wimperis	O
was	O
working	O
on	O
a	O
new	O
bombsight	B-Application
that	O
helped	O
solve	O
these	O
calculations	O
and	O
allow	O
the	O
effects	O
of	O
wind	O
to	O
be	O
considered	O
no	O
matter	O
the	O
direction	O
of	O
the	O
wind	O
or	O
the	O
bomb	B-Device
run	O
.	O
</s>
<s>
The	O
result	O
was	O
the	O
Course	B-Device
Setting	I-Device
Bomb	I-Device
Sight	I-Device
(	O
CSBS	B-Device
)	O
,	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>
Once	O
set	O
up	O
,	O
the	O
bomb	B-Device
aimer	O
would	O
watch	O
objects	O
on	O
the	O
ground	O
and	O
compare	O
their	O
path	O
to	O
thin	O
wires	O
on	O
either	O
side	O
of	O
the	O
sight	O
.	O
</s>
<s>
The	O
bomb	B-Device
aimer	O
(	O
or	O
pilot	O
in	O
some	O
aircraft	O
)	O
then	O
sighted	O
through	O
the	O
attached	O
iron	O
sights	O
to	O
time	O
the	O
drop	O
.	O
</s>
<s>
The	O
CSBS	B-Device
was	O
introduced	O
into	O
service	O
in	O
1917	O
and	O
quickly	O
replaced	O
earlier	O
sights	O
on	O
aircraft	O
that	O
had	O
enough	O
room	O
–	O
the	O
CSBS	B-Device
was	O
fairly	O
large	O
.	O
</s>
<s>
Versions	O
for	O
different	O
speeds	O
,	O
altitudes	O
and	O
bomb	B-Device
types	O
were	O
introduced	O
as	O
the	O
war	O
progressed	O
.	O
</s>
<s>
After	O
the	O
war	O
,	O
the	O
CSBS	B-Device
continued	O
to	O
be	O
the	O
main	O
bombsight	B-Application
in	O
British	O
use	O
.	O
</s>
<s>
A	O
number	O
of	O
experimental	O
devices	O
based	O
on	O
a	O
variation	O
of	O
the	O
CSBS	B-Device
were	O
also	O
developed	O
,	O
notably	O
the	O
US	O
's	O
Estoppey	O
D-1	O
sight	O
,	O
developed	O
shortly	O
after	O
the	O
war	O
,	O
and	O
similar	O
versions	O
from	O
many	O
other	O
nations	O
.	O
</s>
<s>
These	O
"	O
vector	O
bombsights	B-Application
"	O
all	O
shared	O
the	O
basic	O
vector	O
calculator	O
system	O
and	O
drift	O
wires	O
,	O
differing	O
primarily	O
in	O
form	O
and	O
optics	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
introduction	O
of	O
the	O
pilot	O
direction	O
indicator	O
,	O
an	O
electrically	O
driven	O
pointer	O
which	O
the	O
bomb	B-Device
aimer	O
used	O
to	O
indicate	O
corrections	O
from	O
a	O
remote	O
location	O
in	O
the	O
aircraft	O
.	O
</s>
<s>
Vector	O
bombsights	B-Application
remained	O
the	O
standard	O
by	O
most	O
forces	O
well	O
into	O
the	O
Second	O
World	O
War	O
,	O
and	O
was	O
the	O
main	O
sight	O
in	O
British	O
service	O
until	O
1942	O
.	O
</s>
<s>
This	O
was	O
in	O
spite	O
of	O
the	O
introduction	O
of	O
newer	O
sighting	O
systems	O
with	O
great	O
advantages	O
over	O
the	O
CSBS	B-Device
,	O
and	O
even	O
newer	O
versions	O
of	O
the	O
CSBS	B-Device
that	O
failed	O
to	O
be	O
used	O
for	O
a	O
variety	O
of	O
reasons	O
.	O
</s>
<s>
The	O
later	O
versions	O
of	O
the	O
CSBS	B-Device
,	O
eventually	O
reaching	O
the	O
Mark	O
X	O
,	O
included	O
adjustments	O
for	O
different	O
bombs	B-Device
,	O
ways	O
to	O
attack	O
moving	O
targets	O
,	O
systems	O
for	O
more	O
easily	O
measuring	O
winds	O
,	O
and	O
a	O
host	O
of	O
other	O
options	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
problems	O
using	O
vector	O
bombsights	B-Application
was	O
the	O
long	O
straight	O
run	O
needed	O
before	O
dropping	O
the	O
bombs	B-Device
.	O
</s>
<s>
If	O
anything	O
changed	O
during	O
the	O
bomb	B-Device
run	O
,	O
especially	O
if	O
the	O
aircraft	O
had	O
to	O
maneuver	O
in	O
order	O
to	O
avoid	O
defences	O
,	O
everything	O
had	O
to	O
be	O
set	O
up	O
again	O
.	O
</s>
<s>
This	O
further	O
reduced	O
the	O
time	O
the	O
bomb	B-Device
aimer	O
had	O
to	O
adjust	O
the	O
path	O
.	O
</s>
<s>
One	O
solution	O
to	O
this	O
later	O
problem	O
had	O
already	O
been	O
used	O
for	O
some	O
time	O
,	O
the	O
use	O
of	O
some	O
sort	O
of	O
gimbal	O
system	O
to	O
keep	O
the	O
bombsight	B-Application
pointed	O
roughly	O
downward	O
during	O
maneuvering	O
or	O
being	O
blown	O
around	O
by	O
wind	O
gusts	O
.	O
</s>
<s>
The	O
US	O
carried	O
out	O
an	O
active	O
program	O
in	O
this	O
area	O
,	O
including	O
Estoppey	O
sights	O
mounted	O
to	O
weighted	O
gimbals	O
and	O
Sperry	O
Gyroscope	O
's	O
experiments	O
with	O
US	O
versions	O
of	O
the	O
CSBS	B-Device
mounted	O
to	O
what	O
would	O
today	O
be	O
called	O
an	O
inertial	O
platform	O
.	O
</s>
<s>
During	O
the	O
same	O
period	O
,	O
a	O
separate	O
line	O
of	O
development	O
was	O
leading	O
to	O
the	O
first	O
reliable	O
mechanical	B-Device
computers	I-Device
.	O
</s>
<s>
These	O
could	O
be	O
used	O
to	O
replace	O
a	O
complex	O
table	O
of	O
numbers	O
with	O
a	O
carefully	O
shaped	O
cam-like	O
device	O
,	O
and	O
the	O
manual	O
calculation	O
though	O
a	O
series	O
of	O
gears	O
or	O
slip	O
wheels	O
.	O
</s>
<s>
For	O
bombsight	B-Application
use	O
,	O
such	O
a	O
calculator	O
would	O
allow	O
the	O
bomb	B-Device
aimer	O
to	O
dial	O
in	O
the	O
basic	O
aircraft	O
parameters	O
–	O
speed	O
,	O
altitude	O
,	O
direction	O
,	O
and	O
known	O
atmospheric	O
conditions	O
–	O
and	O
the	O
bomb	B-Application
sight	I-Application
would	O
automatically	O
calculate	O
the	O
proper	O
aim	O
point	O
in	O
a	O
few	O
moments	O
.	O
</s>
<s>
During	O
the	O
1920s	O
,	O
the	O
Navy	O
funded	O
development	O
of	O
the	O
Norden	B-Device
bombsight	I-Device
while	O
the	O
Army	O
funded	O
development	O
of	O
the	O
Sperry	O
O-1	O
.	O
</s>
<s>
Both	O
systems	O
were	O
generally	O
similar	O
;	O
a	O
bomb	B-Application
sight	I-Application
consisting	O
of	O
a	O
small	O
telescope	O
was	O
mounted	O
on	O
a	O
stabilizing	O
platform	O
to	O
keep	O
the	O
sighting	O
head	O
stable	O
.	O
</s>
<s>
A	O
separate	O
mechanical	B-Device
computer	I-Device
was	O
used	O
to	O
calculate	O
the	O
aim	O
point	O
.	O
</s>
<s>
When	O
the	O
bomb	B-Device
aimer	O
sighted	O
through	O
the	O
telescope	O
,	O
he	O
could	O
see	O
any	O
residual	O
drift	O
and	O
relay	O
this	O
to	O
the	O
pilot	O
,	O
or	O
later	O
,	O
feed	O
that	O
information	O
directly	O
into	O
the	O
autopilot	O
.	O
</s>
<s>
For	O
a	O
variety	O
of	O
reasons	O
,	O
the	O
Army	O
dropped	O
their	O
interest	O
in	O
the	O
Sperry	O
,	O
and	O
features	O
from	O
the	O
Sperry	O
and	O
Norden	B-Device
bombsights	I-Device
were	O
folded	O
into	O
new	O
models	O
of	O
the	O
Norden	B-Device
.	O
</s>
<s>
The	O
Norden	B-Device
then	O
equipped	O
almost	O
all	O
US	O
high-level	O
bombers	O
,	O
most	O
notably	O
the	O
B-17	B-Application
Flying	I-Application
Fortress	I-Application
.	O
</s>
<s>
In	O
tests	O
,	O
these	O
bombsights	B-Application
were	O
able	O
to	O
generate	O
fantastic	O
accuracy	O
.	O
</s>
<s>
In	O
practice	O
,	O
however	O
,	O
operational	O
factors	O
seriously	O
upset	O
them	O
,	O
to	O
the	O
point	O
that	O
pinpoint	O
bombing	O
using	O
the	O
Norden	B-Device
was	O
eventually	O
abandoned	O
.	O
</s>
<s>
In	O
the	O
UK	O
,	O
work	O
on	O
the	O
Automatic	O
Bomb	B-Application
Sight	I-Application
(	O
ABS	O
)	O
had	O
been	O
carried	O
on	O
since	O
the	O
mid-1930s	O
in	O
an	O
effort	O
to	O
replace	O
the	O
CSBS	B-Device
.	O
</s>
<s>
However	O
,	O
the	O
ABS	O
did	O
not	O
include	O
stabilization	O
of	O
the	O
sighting	O
system	O
,	O
nor	O
the	O
Norden	B-Device
's	O
autopilot	O
system	O
.	O
</s>
<s>
In	O
testing	O
the	O
ABS	O
proved	O
to	O
be	O
too	O
difficult	O
to	O
use	O
,	O
requiring	O
long	O
bomb	B-Device
runs	O
to	O
allow	O
the	O
computer	O
time	O
to	O
solve	O
the	O
aim	O
point	O
.	O
</s>
<s>
When	O
RAF	O
Bomber	O
Command	O
complained	O
that	O
even	O
the	O
CSBS	B-Device
had	O
too	O
long	O
a	O
run-in	O
to	O
the	O
target	O
,	O
efforts	O
to	O
deploy	O
the	O
ABS	O
ended	O
.	O
</s>
<s>
For	O
their	O
needs	O
they	O
developed	O
a	O
new	O
vector	O
bombsight	B-Application
,	O
the	O
Mk	O
.	O
</s>
<s>
XIV	O
featured	O
a	O
stabilizing	O
platform	O
and	O
aiming	O
computer	O
,	O
but	O
worked	O
more	O
like	O
the	O
CSBS	B-Device
in	O
overall	O
functionality	O
–	O
the	O
bomb	B-Device
aimer	O
would	O
set	O
the	O
computer	O
to	O
move	O
the	O
sighting	O
system	O
to	O
the	O
proper	O
angle	O
,	O
but	O
the	O
bombsight	B-Application
did	O
not	O
track	O
the	O
target	O
or	O
attempt	O
to	O
correct	O
the	O
aircraft	O
path	O
.	O
</s>
<s>
Both	O
the	O
British	O
and	O
Germans	O
would	O
later	O
introduce	O
Norden-like	O
sights	O
of	O
their	O
own	O
.	O
</s>
<s>
Based	O
at	O
least	O
partially	O
on	O
information	O
about	O
the	O
Norden	B-Device
passed	O
to	O
them	O
through	O
the	O
Duquesne	O
Spy	O
Ring	O
,	O
the	O
Luftwaffe	O
developed	O
the	O
Lotfernrohr	B-Device
7	I-Device
.	O
</s>
<s>
The	O
basic	O
mechanism	O
was	O
almost	O
identical	O
to	O
the	O
Norden	B-Device
,	O
but	O
much	O
smaller	O
.	O
</s>
<s>
In	O
certain	O
applications	O
the	O
Lotfernrohr	B-Device
7	I-Device
could	O
be	O
used	O
by	O
a	O
single-crew	O
aircraft	O
,	O
as	O
was	O
the	O
case	O
for	O
the	O
Arado	O
Ar	O
234	O
,	O
the	O
world	O
's	O
first	O
operational	O
jet	O
bomber	O
.	O
</s>
<s>
During	O
the	O
war	O
the	O
RAF	O
had	O
the	O
need	O
for	O
accurate	O
high-altitude	O
bombing	O
and	O
in	O
1943	O
introduced	O
a	O
stabilized	O
version	O
of	O
the	O
earlier	O
ABS	O
,	O
the	O
hand-built	O
Stabilized	B-Device
Automatic	I-Device
Bomb	I-Device
Sight	I-Device
(	O
SABS	O
)	O
.	O
</s>
<s>
At	O
night	O
the	O
bomber	O
is	O
virtually	O
invulnerable	O
(	O
until	O
the	O
introduction	O
of	O
radar	B-Application
)	O
but	O
finding	O
its	O
target	O
was	O
a	O
major	O
problem	O
.	O
</s>
<s>
During	O
the	O
day	O
the	O
bomber	O
could	O
use	O
its	O
bombsights	B-Application
to	O
attack	O
point	O
targets	O
,	O
but	O
only	O
at	O
the	O
risk	O
of	O
being	O
attacked	O
by	O
enemy	O
fighters	O
and	O
anti-aircraft	O
artillery	O
.	O
</s>
<s>
The	O
Oboe	O
system	O
,	O
first	O
used	O
operationally	O
in	O
early	O
1943	O
,	O
offered	O
real-world	O
accuracies	O
on	O
the	O
order	O
of	O
35yards	O
,	O
much	O
better	O
than	O
any	O
optical	O
bombsight	B-Application
.	O
</s>
<s>
The	O
introduction	O
of	O
the	O
British	O
H2S	O
radar	B-Application
further	O
improved	O
the	O
bomber	O
's	O
abilities	O
,	O
allowing	O
direct	O
attack	O
of	O
targets	O
without	O
the	O
need	O
of	O
remote	O
radio	O
transmitters	O
,	O
which	O
had	O
range	O
limited	O
to	O
the	O
line-of-sight	O
.	O
</s>
<s>
By	O
1943	O
these	O
techniques	O
were	O
in	O
widespread	O
use	O
by	O
both	O
the	O
RAF	O
and	O
USAAF	O
,	O
leading	O
to	O
the	O
H2X	O
and	O
then	O
a	O
series	O
of	O
improved	O
versions	O
like	O
the	O
AN/APQ	B-Device
-13	I-Device
and	O
AN/APQ	O
-7	O
used	O
on	O
the	O
Boeing	O
B-29	O
Superfortress	O
.	O
</s>
<s>
These	O
early	O
systems	O
operated	O
independently	O
of	O
any	O
existing	O
optical	O
bombsight	B-Application
,	O
but	O
this	O
presented	O
the	O
problem	O
of	O
having	O
to	O
separately	O
calculate	O
the	O
trajectory	O
of	O
the	O
bomb	B-Device
.	O
</s>
<s>
But	O
as	O
daylight	O
visual	O
bombing	O
was	O
still	O
widely	O
used	O
,	O
conversions	O
and	O
adaptations	O
were	O
quickly	O
made	O
to	O
repeat	O
the	O
radar	B-Application
signal	O
in	O
the	O
existing	O
bombsights	B-Application
,	O
allowing	O
the	O
bombsight	B-Application
calculator	O
to	O
solve	O
the	O
radar	B-Application
bombing	O
problem	O
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
AN/APA	O
-47	O
was	O
used	O
to	O
combine	O
the	O
output	O
from	O
the	O
AN/APQ	O
-7	O
with	O
the	O
Norden	B-Device
,	O
allowing	O
the	O
bomb	B-Device
aimer	O
to	O
easily	O
check	O
both	O
images	O
to	O
compare	O
the	O
aim	O
point	O
.	O
</s>
<s>
Analysis	O
of	O
the	O
results	O
of	O
bombing	O
attacks	O
carried	O
out	O
using	O
radio	O
navigation	O
or	O
radar	B-Application
techniques	O
demonstrated	O
accuracy	O
was	O
essentially	O
equal	O
for	O
the	O
two	O
systems	O
–	O
night	O
time	O
attacks	O
with	O
Oboe	O
were	O
able	O
to	O
hit	O
targets	O
that	O
the	O
Norden	B-Device
could	O
not	O
during	O
the	O
day	O
.	O
</s>
<s>
With	O
the	O
exception	O
of	O
operational	O
considerations	O
–	O
limited	O
resolution	O
of	O
the	O
radar	B-Application
and	O
limited	O
range	O
of	O
the	O
navigation	O
systems	O
–	O
the	O
need	O
for	O
visual	O
bombsights	B-Application
quickly	O
disappeared	O
.	O
</s>
<s>
Designs	O
of	O
the	O
late-war	O
era	O
,	O
like	O
the	O
Boeing	O
B-47	O
Stratojet	O
and	O
English	O
Electric	O
Canberra	O
retained	O
their	O
optical	O
systems	O
,	O
but	O
these	O
were	O
often	O
considered	O
secondary	O
to	O
the	O
radar	B-Application
and	O
radio	O
systems	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
the	O
Canberra	O
,	O
the	O
optical	O
system	O
only	O
existed	O
due	O
to	O
delays	O
in	O
the	O
radar	B-Application
system	I-Application
becoming	O
available	O
.	O
</s>
<s>
Although	O
the	O
tachometric	B-Device
bombsights	I-Device
provided	O
most	O
of	O
the	O
features	O
needed	O
for	O
accurate	O
bombing	O
,	O
they	O
were	O
complex	O
,	O
slow	O
,	O
and	O
limited	O
to	O
straight-line	O
and	O
level	O
attacks	O
.	O
</s>
<s>
They	O
concluded	O
that	O
at	O
speeds	O
over	O
,	O
optical	O
systems	O
would	O
be	O
useless	O
–	O
the	O
visual	O
range	O
to	O
the	O
target	O
would	O
be	O
less	O
than	O
the	O
range	O
of	O
a	O
bomb	B-Device
being	O
dropped	O
at	O
high	O
altitudes	O
and	O
speeds	O
.	O
</s>
<s>
This	O
demanded	O
radar	B-Application
bombing	O
systems	O
,	O
but	O
existing	O
examples	O
did	O
not	O
offer	O
anywhere	O
near	O
the	O
required	O
performance	O
.	O
</s>
<s>
At	O
the	O
stratospheric	O
altitudes	O
and	O
long	O
"	O
sighting	O
"	O
ranges	O
being	O
considered	O
,	O
the	O
radar	B-Application
antenna	O
would	O
need	O
to	O
be	O
very	O
large	O
to	O
offer	O
the	O
required	O
resolution	O
,	O
yet	O
this	O
ran	O
counter	O
for	O
the	O
need	O
to	O
develop	O
an	O
antenna	O
that	O
was	O
as	O
small	O
as	O
possible	O
in	O
order	O
to	O
reduce	O
drag	O
.	O
</s>
<s>
They	O
also	O
pointed	O
out	O
that	O
many	O
targets	O
would	O
not	O
show	O
up	O
directly	O
on	O
the	O
radar	B-Application
,	O
so	O
the	O
bombsight	B-Application
would	O
need	O
the	O
ability	O
to	O
drop	O
at	O
points	O
relative	O
to	O
some	O
landmark	O
that	O
did	O
appear	O
,	O
the	O
so-called	O
"	O
offset	O
aiming	O
points	O
"	O
.	O
</s>
<s>
They	O
proposed	O
a	O
single	O
system	O
that	O
would	O
offer	O
mapping	O
,	O
navigation	O
,	O
autopilot	O
and	O
bomb	B-Device
aiming	O
,	O
thereby	O
reducing	O
complexity	O
,	O
and	O
especially	O
the	O
needed	O
space	O
.	O
</s>
<s>
Through	O
the	O
1950s	O
and	O
1960s	O
,	O
radar	B-Application
bombing	O
of	O
this	O
sort	O
was	O
common	O
and	O
the	O
accuracy	O
of	O
the	O
systems	O
were	O
limited	O
to	O
what	O
was	O
needed	O
to	O
support	O
attacks	O
by	O
nuclear	O
weapons	O
–	O
a	O
circular	O
error	O
probable	O
(	O
CEP	O
)	O
of	O
about	O
was	O
considered	O
adequate	O
.	O
</s>
<s>
These	O
systems	O
quickly	O
improved	O
in	O
accuracy	O
,	O
and	O
eventually	O
became	O
accurate	O
enough	O
to	O
handle	O
the	O
bomb	B-Device
dropping	O
without	O
the	O
need	O
for	O
a	O
separate	O
bombsight	B-Application
.	O
</s>
<s>
This	O
was	O
the	O
case	O
for	O
the	O
accuracy	O
demanded	O
of	O
the	O
B-70	O
Valkyrie	O
,	O
which	O
lacked	O
any	O
sort	O
of	O
conventional	O
bombsight	B-Application
.	O
</s>
<s>
During	O
the	O
Cold	B-Application
War	I-Application
the	O
weapon	O
of	O
choice	O
was	O
a	O
nuclear	O
one	O
,	O
and	O
accuracy	O
needs	O
were	O
limited	O
.	O
</s>
<s>
Development	O
of	O
tactical	O
bombing	O
systems	O
,	O
notably	O
the	O
ability	O
to	O
attack	O
point	O
targets	O
with	O
conventional	O
weapons	O
that	O
had	O
been	O
the	O
original	O
goal	O
of	O
the	O
Norden	B-Device
,	O
was	O
not	O
considered	O
seriously	O
.	O
</s>
<s>
Thus	O
when	O
the	O
US	O
entered	O
the	O
Vietnam	O
War	O
,	O
their	O
weapon	O
of	O
choice	O
was	O
the	O
Douglas	O
A-26	O
Invader	O
equipped	O
with	O
the	O
Norden	B-Device
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
the	O
ever-increasing	O
power	O
levels	O
of	O
new	O
jet	O
engines	O
led	O
to	O
fighter	O
aircraft	O
with	O
bomb	B-Device
loads	O
similar	O
to	O
heavy	O
bombers	O
of	O
a	O
generation	O
earlier	O
.	O
</s>
<s>
This	O
generated	O
demand	O
for	O
a	O
new	O
generation	O
of	O
greatly	O
improved	O
bombsights	B-Application
that	O
could	O
be	O
used	O
by	O
a	O
single-crew	O
aircraft	O
and	O
employed	O
in	O
fighter-like	O
tactics	O
,	O
whether	O
high-level	O
,	O
low-level	O
,	O
in	O
a	O
dive	O
towards	O
the	O
target	O
,	O
or	O
during	O
hard	O
maneuvering	O
.	O
</s>
<s>
A	O
specialist	O
capability	O
for	O
toss	O
bombing	O
also	O
developed	O
in	O
order	O
to	O
allow	O
aircraft	O
to	O
escape	O
the	O
blast	O
radius	O
of	O
their	O
own	O
nuclear	O
weapons	O
,	O
something	O
that	O
required	O
only	O
middling	O
accuracy	O
but	O
a	O
very	O
different	O
trajectory	O
that	O
initially	O
required	O
a	O
dedicated	O
bombsight	B-Application
.	O
</s>
<s>
They	O
may	O
be	O
controlled	O
by	O
the	O
pilot	O
directly	O
and	O
provide	O
information	O
through	O
the	O
head-up	B-Application
display	I-Application
or	O
a	O
video	O
display	O
on	O
the	O
instrument	O
panel	O
.	O
</s>
<s>
The	O
definition	O
of	O
bombsight	B-Application
is	O
becoming	O
blurred	O
as	O
"	O
smart	O
"	O
bombs	B-Device
with	O
in-flight	O
guidance	O
,	O
such	O
as	O
laser-guided	O
bombs	B-Device
or	O
those	O
using	O
GPS	O
,	O
replace	O
"	O
dumb	O
"	O
gravity	O
bombs	B-Device
.	O
</s>
