<s>
XV	O
,	O
known	O
as	O
the	O
Norden	O
M	O
series	O
in	O
U.S.	O
Army	O
service	O
,	O
is	O
a	O
bombsight	B-Application
that	O
was	O
used	O
by	O
the	O
United	O
States	O
Army	O
Air	O
Forces	O
(	O
USAAF	O
)	O
and	O
the	O
United	O
States	O
Navy	O
during	O
World	O
War	O
II	O
,	O
and	O
the	O
United	O
States	O
Air	O
Force	O
in	O
the	O
Korean	O
and	O
the	O
Vietnam	O
Wars	O
.	O
</s>
<s>
It	O
was	O
an	O
early	O
tachometric	O
design	O
that	O
directly	O
measured	O
the	O
aircraft	O
's	O
ground	O
speed	O
and	O
direction	O
,	O
which	O
older	O
bombsights	B-Application
could	O
only	O
estimate	O
with	O
lengthy	O
manual	O
procedures	O
.	O
</s>
<s>
The	O
Norden	O
was	O
not	O
as	O
secret	O
as	O
believed	O
;	O
both	O
the	O
British	O
SABS	B-Device
and	O
German	O
Lotfernrohr	B-Device
7	I-Device
worked	O
on	O
similar	O
principles	O
,	O
and	O
details	O
of	O
the	O
Norden	O
had	O
been	O
passed	O
to	O
Germany	O
even	O
before	O
the	O
war	O
started	O
.	O
</s>
<s>
The	O
Norden	O
saw	O
reduced	O
use	O
in	O
the	O
post	O
–	O
World	O
War	O
II	O
period	O
after	O
radar-based	O
targeting	O
was	O
introduced	O
,	O
but	O
the	O
need	O
for	O
accurate	O
daytime	O
attacks	O
kept	O
it	O
in	O
service	O
,	O
especially	O
during	O
the	O
Korean	O
War	O
.	O
</s>
<s>
The	O
Norden	O
remains	O
one	O
of	O
the	O
best-known	O
bombsights	B-Application
.	O
</s>
<s>
The	O
Norden	B-Device
sight	I-Device
was	O
designed	O
by	O
Carl	O
Norden	O
,	O
a	O
Dutch	O
engineer	O
educated	O
in	O
Switzerland	B-Protocol
who	O
emigrated	O
to	O
the	O
U.S.	O
in	O
1904	O
.	O
</s>
<s>
World	O
War	O
I	O
bomb	B-Application
sight	I-Application
designs	O
had	O
improved	O
rapidly	O
,	O
with	O
the	O
ultimate	O
development	O
being	O
the	O
Course	B-Device
Setting	I-Device
Bomb	I-Device
Sight	I-Device
,	O
or	O
CSBS	B-Device
.	O
</s>
<s>
The	O
hypotenuse	O
of	O
the	O
triangle	O
was	O
the	O
line	O
the	O
aircraft	O
needed	O
to	O
fly	O
along	O
in	O
order	O
to	O
arrive	O
over	O
the	O
target	O
in	O
the	O
presence	O
of	O
wind	O
,	O
which	O
,	O
before	O
the	O
CSBS	B-Device
,	O
was	O
an	O
intractable	O
problem	O
.	O
</s>
<s>
Almost	O
all	O
air	O
forces	O
adopted	O
some	O
variation	O
of	O
the	O
CSBS	B-Device
as	O
their	O
standard	O
inter-war	O
bomb	B-Application
sight	I-Application
,	O
including	O
the	O
U.S.	O
Navy	O
and	O
U.S.	O
Army	O
,	O
who	O
used	O
a	O
version	O
designed	O
by	O
Georges	O
Estoppey	O
,	O
the	O
D-series	O
.	O
</s>
<s>
It	O
was	O
already	O
realized	O
that	O
one	O
major	O
source	O
of	O
error	O
in	O
bombing	O
was	O
leveling	O
the	O
aircraft	O
enough	O
so	O
the	O
bombsight	B-Application
pointed	O
straight	O
down	O
.	O
</s>
<s>
Even	O
small	O
errors	O
in	O
leveling	O
could	O
produce	O
dramatic	O
errors	O
in	O
bombing	O
,	O
so	O
the	O
Navy	O
began	O
a	O
series	O
of	O
developments	O
to	O
add	O
a	O
gyroscopic	O
stabilizer	O
to	O
various	O
bomb	B-Application
sight	I-Application
designs	O
.	O
</s>
<s>
Although	O
the	O
CSBS	B-Device
and	O
similar	O
designs	O
allowed	O
the	O
calculation	O
of	O
the	O
proper	O
flight	O
angle	O
needed	O
to	O
correct	O
for	O
windage	O
,	O
they	O
did	O
so	O
by	O
looking	O
downward	O
out	O
of	O
the	O
aircraft	O
,	O
so	O
the	O
correct	O
angle	O
was	O
not	O
easily	O
visible	O
to	O
the	O
pilot	O
.	O
</s>
<s>
Norden	O
's	O
first	O
attempt	O
at	O
an	O
improved	O
bombsight	B-Application
was	O
actually	O
an	O
advance	O
in	O
PDI	O
design	O
.	O
</s>
<s>
His	O
idea	O
was	O
to	O
remove	O
the	O
manual	O
electrical	O
switches	O
used	O
to	O
move	O
the	O
pointer	O
and	O
use	O
the	O
entire	O
bombsight	B-Application
itself	O
as	O
the	O
indicator	O
.	O
</s>
<s>
To	O
time	O
the	O
drop	O
,	O
Norden	O
used	O
an	O
idea	O
already	O
in	O
use	O
on	O
other	O
bombsights	B-Application
,	O
the	O
"	O
equal	O
distance	O
"	O
concept	O
.	O
</s>
<s>
He	O
went	O
on	O
to	O
request	O
information	O
on	O
every	O
bombsight	B-Application
then	O
used	O
at	O
Wright	O
,	O
as	O
well	O
as	O
"	O
the	O
Navy	O
's	O
newest	O
design	O
"	O
.	O
</s>
<s>
The	O
Army	O
turned	O
its	O
attention	O
to	O
further	O
upgraded	O
versions	O
of	O
their	O
existing	O
prototypes	O
,	O
replacing	O
the	O
older	O
vector	O
bombsight	B-Application
mechanisms	O
with	O
the	O
new	O
synchronous	O
method	O
of	O
measuring	O
the	O
proper	O
dropping	O
angle	O
.	O
</s>
<s>
XI	O
was	O
reaching	O
its	O
final	O
design	O
,	O
the	O
Navy	O
learned	O
of	O
the	O
Army	O
's	O
efforts	O
to	O
develop	O
a	O
synchronous	O
bombsight	B-Application
,	O
and	O
asked	O
Norden	O
to	O
design	O
one	O
for	O
them	O
.	O
</s>
<s>
Lieutenant	O
Frederick	O
Entwistle	O
,	O
the	O
Navy	O
's	O
chief	O
of	O
bombsight	B-Application
development	O
,	O
judged	O
it	O
revolutionary	O
.	O
</s>
<s>
There	O
was	O
no	O
need	O
for	O
external	O
calculation	O
,	O
lookup	O
tables	O
or	O
pre-run	O
measurementseverything	O
was	O
carried	O
out	O
automatically	O
through	O
an	O
internal	O
wheel-and-disc	B-Device
calculator	I-Device
.	O
</s>
<s>
In	O
practice	O
,	O
it	O
was	O
found	O
that	O
the	O
pilots	O
had	O
a	O
very	O
difficult	O
time	O
keeping	O
the	O
aircraft	O
stable	O
enough	O
to	O
match	O
the	O
accuracy	O
of	O
the	O
bombsight	B-Application
.	O
</s>
<s>
Starting	O
in	O
1932	O
and	O
proceeding	O
in	O
fits	O
and	O
starts	O
for	O
the	O
next	O
six	O
years	O
,	O
Norden	O
developed	O
the	O
Stabilized	O
Bombing	O
Approach	O
Equipment	O
(	O
SBAE	O
)	O
,	O
a	O
mechanical	O
autopilot	O
that	O
attached	O
to	O
the	O
bombsight	B-Application
.	O
</s>
<s>
By	O
rotating	O
the	O
bombsight	B-Application
in	O
relationship	O
to	O
the	O
SBAE	O
,	O
the	O
SBAE	O
could	O
account	O
for	O
wind	O
and	O
turbulence	O
and	O
calculate	O
the	O
appropriate	O
directional	O
changes	O
needed	O
to	O
bring	O
the	O
aircraft	O
onto	O
the	O
bomb	O
run	O
far	O
more	O
precisely	O
than	O
a	O
human	O
pilot	O
.	O
</s>
<s>
The	O
minor	O
adaptations	O
needed	O
on	O
the	O
bombsight	B-Application
itself	O
produced	O
what	O
the	O
Army	O
referred	O
to	O
as	O
the	O
M-4	O
model	O
.	O
</s>
<s>
By	O
connecting	O
the	O
outputs	O
of	O
the	O
S-1	O
bombsight	B-Application
to	O
the	O
A-5	O
autopilot	O
,	O
Sperry	O
produced	O
a	O
system	O
similar	O
to	O
the	O
M-4/SBAE	O
,	O
but	O
it	O
reacted	O
far	O
more	O
quickly	O
.	O
</s>
<s>
The	O
combination	O
of	O
the	O
S-1	O
and	O
A-5	O
so	O
impressed	O
the	O
Army	O
that	O
on	O
17	O
June	O
1941	O
they	O
authorized	O
the	O
construction	O
of	O
a	O
factory	O
and	O
noted	O
that	O
"	O
in	O
the	O
future	O
all	O
production	O
models	O
of	O
bombardment	O
airplanes	O
be	O
equipped	O
with	O
the	O
A-5	O
Automatic	O
Pilot	O
and	O
have	O
provisions	O
permitting	O
the	O
installation	O
of	O
either	O
the	O
M-Series	O
 [ Norden ] 	O
Bombsight	B-Application
or	O
the	O
S-1	O
Bombsight	B-Application
"	O
.	O
</s>
<s>
The	O
British	O
had	O
been	O
developing	O
a	O
similar	O
bombsight	B-Application
known	O
as	O
the	O
Automatic	O
Bomb	B-Application
Sight	I-Application
,	O
but	O
combat	O
experience	O
in	O
1939	O
demonstrated	O
the	O
need	O
for	O
it	O
to	O
be	O
stabilized	O
.	O
</s>
<s>
Work	O
was	O
under	O
way	O
as	O
the	O
Stabilized	B-Device
Automatic	I-Device
Bomb	I-Device
Sight	I-Device
(	O
SABS	B-Device
)	O
,	O
but	O
it	O
would	O
not	O
be	O
available	O
until	O
1940	O
at	O
the	O
earliest	O
,	O
and	O
likely	O
later	O
.	O
</s>
<s>
They	O
wrote	O
to	O
George	O
Pirie	O
,	O
the	O
British	O
air	O
attaché	O
in	O
Washington	O
,	O
suggesting	O
he	O
approach	O
the	O
U.S.	O
Army	O
with	O
an	O
offer	O
of	O
an	O
information	O
exchange	O
with	O
their	O
own	O
SABS	B-Device
.	O
</s>
<s>
When	O
a	O
report	O
stated	O
that	O
the	O
Norden	O
's	O
results	O
were	O
three	O
to	O
four	O
times	O
as	O
good	O
as	O
their	O
own	O
bombsights	B-Application
,	O
the	O
Air	O
Ministry	O
decided	O
to	O
sweeten	O
the	O
pot	O
and	O
suggested	O
they	O
offer	O
information	O
on	O
radar	B-Application
in	O
exchange	O
.	O
</s>
<s>
Between	O
1932	O
and	O
1938	O
,	O
the	O
company	O
produced	O
only	O
121	O
bombsights	B-Application
per	O
year	O
.	O
</s>
<s>
During	O
the	O
first	O
year	O
after	O
the	O
Attack	B-Application
on	I-Application
Pearl	I-Application
Harbor	I-Application
,	O
Norden	O
produced	O
6,900	O
bombsights	B-Application
,	O
three-quarters	O
of	O
which	O
went	O
to	O
the	O
U.S.	O
Navy	O
.	O
</s>
<s>
Norden	O
actively	O
attempted	O
to	O
make	O
the	O
bombsight	B-Application
incompatible	O
with	O
the	O
A-5	O
,	O
and	O
it	O
was	O
not	O
until	O
1942	O
that	O
the	O
impasse	O
was	O
finally	O
solved	O
by	O
farming	O
out	O
autopilot	O
production	O
to	O
Honeywell	O
Regulator	O
,	O
who	O
combined	O
features	O
of	O
the	O
Norden-mounted	O
SBAE	O
with	O
the	O
aircraft-mounted	O
A-5	O
to	O
produce	O
what	O
the	O
U.S.	O
Army	O
referred	O
to	O
as	O
"	O
Automatic	O
Flight	O
Control	O
Equipment	O
"	O
(	O
AFCE	O
)	O
the	O
unit	O
would	O
later	O
be	O
redesigned	O
as	O
the	O
C-1	O
.	O
</s>
<s>
After	O
investing	O
more	O
than	O
$100	O
million	O
in	O
Sperry	O
bombsight	B-Application
manufacturing	O
plants	O
,	O
the	O
USAAF	O
concluded	O
that	O
the	O
Norden	O
M-series	O
was	O
far	O
superior	O
in	O
accuracy	O
,	O
dependability	O
,	O
and	O
design	O
.	O
</s>
<s>
When	O
production	O
ended	O
a	O
few	O
months	O
later	O
,	O
5,563	O
Sperry	O
bombsight-autopilot	O
combinations	O
had	O
been	O
built	O
,	O
most	O
of	O
which	O
were	O
installed	O
in	O
Consolidated	O
B-24	O
Liberator	O
bombers	O
.	O
</s>
<s>
Expansion	O
of	O
Norden	B-Device
bombsight	I-Device
production	O
to	O
a	O
final	O
total	O
of	O
six	O
factories	O
took	O
several	O
years	O
.	O
</s>
<s>
By	O
the	O
end	O
of	O
the	O
war	O
,	O
Norden	O
and	O
its	O
subcontractors	O
had	O
produced	O
72,000	O
M-9	O
bombsights	B-Application
for	O
the	O
U.S.	O
Army	O
Air	O
Force	O
alone	O
,	O
costing	O
$	O
8,800	O
each	O
.	O
</s>
<s>
Typical	O
bombsights	B-Application
of	O
the	O
pre-war	O
era	O
worked	O
on	O
the	O
"	O
vector	O
bombsight	B-Application
"	O
principle	O
introduced	O
with	O
the	O
World	O
War	O
I	O
Course	B-Device
Setting	I-Device
Bomb	I-Device
Sight	I-Device
.	O
</s>
<s>
The	O
mathematical	O
principles	O
are	O
identical	O
to	O
those	O
on	O
the	O
E6B	B-Device
calculator	O
used	O
to	O
this	O
day	O
.	O
</s>
<s>
In	O
operation	O
,	O
the	O
bombardier	O
would	O
first	O
take	O
a	O
measurement	O
of	O
the	O
wind	O
speed	O
using	O
one	O
of	O
a	O
variety	O
of	O
methods	O
,	O
and	O
then	O
dial	O
that	O
speed	O
and	O
direction	O
into	O
the	O
bombsight	B-Application
.	O
</s>
<s>
The	O
first	O
was	O
that	O
there	O
were	O
several	O
steps	O
that	O
had	O
to	O
be	O
carried	O
out	O
in	O
sequence	O
in	O
order	O
to	O
set	O
up	O
the	O
bombsight	B-Application
correctly	O
,	O
and	O
there	O
was	O
limited	O
time	O
to	O
do	O
all	O
of	O
this	O
during	O
the	O
bomb	O
run	O
.	O
</s>
<s>
The	O
second	O
problem	O
was	O
that	O
the	O
sight	O
was	O
attached	O
to	O
the	O
aircraft	O
,	O
and	O
thus	O
moved	O
about	O
during	O
maneuvers	O
,	O
during	O
which	O
time	O
the	O
bombsight	B-Application
would	O
not	O
point	O
at	O
the	O
target	O
.	O
</s>
<s>
Experiments	O
had	O
shown	O
that	O
adding	O
a	O
stabilizer	O
system	O
to	O
a	O
vector	O
bombsight	B-Application
would	O
roughly	O
double	O
the	O
accuracy	O
of	O
the	O
system	O
.	O
</s>
<s>
This	O
would	O
allow	O
the	O
bombsight	B-Application
to	O
remain	O
level	O
while	O
the	O
aircraft	O
maneuvered	O
,	O
giving	O
the	O
bombardier	O
more	O
time	O
to	O
make	O
his	O
adjustments	O
,	O
as	O
well	O
as	O
reducing	O
or	O
eliminating	O
mis-measurements	O
when	O
sighting	O
off	O
of	O
non-level	O
sights	O
.	O
</s>
<s>
To	O
improve	O
the	O
calculation	O
time	O
,	O
the	O
Norden	O
used	O
a	O
mechanical	B-Device
computer	I-Device
inside	O
the	O
bombsight	B-Application
to	O
calculate	O
the	O
range	O
angle	O
of	O
the	O
bombs	O
.	O
</s>
<s>
This	O
not	O
only	O
reduced	O
the	O
time	O
needed	O
for	O
the	O
bombsight	B-Application
setup	O
but	O
also	O
dramatically	O
reduced	O
the	O
chance	O
for	O
errors	O
.	O
</s>
<s>
This	O
attack	O
on	O
the	O
accuracy	O
problem	O
was	O
by	O
no	O
means	O
unique	O
;	O
several	O
other	O
bombsights	B-Application
of	O
the	O
era	O
used	O
similar	O
calculators	O
.	O
</s>
<s>
Conventional	O
bombsights	B-Application
are	O
set	O
up	O
pointing	O
at	O
a	O
fixed	O
angle	O
,	O
the	O
range	O
angle	O
,	O
which	O
accounts	O
for	O
the	O
various	O
effects	O
on	O
the	O
trajectory	B-Application
of	O
the	O
bomb	O
.	O
</s>
<s>
One	O
example	O
of	O
a	O
highly	O
automated	O
system	O
of	O
this	O
type	O
was	O
the	O
RAF	O
's	O
Mark	B-Device
XIV	I-Device
bomb	I-Device
sight	I-Device
.	O
</s>
<s>
Over	O
a	O
short	O
period	O
of	O
time	O
of	O
continual	O
adjustments	O
,	O
the	O
drift	O
would	O
stop	O
,	O
and	O
the	O
bombsight	B-Application
would	O
now	O
hold	O
an	O
extremely	O
accurate	O
measurement	O
of	O
the	O
exact	O
ground	O
speed	O
and	O
heading	O
.	O
</s>
<s>
In	O
order	O
to	O
properly	O
account	O
for	O
this	O
non-linear	O
effect	O
,	O
the	O
Norden	O
used	O
a	O
system	O
of	O
slip-disks	O
similar	O
to	O
those	O
used	O
in	O
differential	B-Device
analysers	I-Device
.	O
</s>
<s>
The	O
Norden	B-Device
bombsight	I-Device
consisted	O
of	O
two	O
primary	O
parts	O
,	O
the	O
gyroscopic	O
stabilization	O
platform	O
on	O
the	O
left	O
side	O
,	O
and	O
the	O
mechanical	O
calculator	O
and	O
sighting	O
head	O
on	O
the	O
right	O
side	O
.	O
</s>
<s>
The	O
bombsight	B-Application
calculated	O
the	O
current	O
aim	O
point	O
internally	O
and	O
displayed	O
this	O
as	O
a	O
sliding	O
pointer	O
on	O
the	O
index	O
.	O
</s>
<s>
In	O
U.S.	O
Army	O
Air	O
Forces	O
use	O
,	O
the	O
Norden	B-Device
bombsight	I-Device
was	O
attached	O
to	O
its	O
autopilot	O
base	O
,	O
which	O
was	O
in	O
turn	O
connected	O
with	O
the	O
aircraft	O
's	O
autopilot	O
.	O
</s>
<s>
From	O
that	O
point	O
on	O
,	O
the	O
autopilot	O
would	O
attempt	O
to	O
guide	O
the	O
bomber	O
so	O
it	O
followed	O
the	O
course	O
of	O
the	O
bombsight	B-Application
,	O
and	O
pointed	O
the	O
heading	O
to	O
zero	O
out	O
the	O
drift	O
rate	O
,	O
fed	O
to	O
it	O
through	O
a	O
coupling	O
.	O
</s>
<s>
Notable	O
among	O
these	O
was	O
the	O
radar	B-Application
system	I-Application
called	O
the	O
H2X	O
(	O
Mickey	O
)	O
,	O
which	O
were	O
used	O
directly	O
with	O
the	O
Norden	B-Device
bombsight	I-Device
.	O
</s>
<s>
The	O
radar	B-Application
proved	O
most	O
accurate	O
in	O
coastal	O
regions	O
,	O
as	O
the	O
water	O
surface	O
and	O
the	O
coastline	O
produced	O
a	O
distinctive	O
radar	B-Application
echo	O
.	O
</s>
<s>
The	O
Norden	B-Device
bombsight	I-Device
was	O
developed	O
during	O
a	O
period	O
of	O
United	O
States	O
non-interventionism	O
when	O
the	O
dominant	O
U.S.	O
military	O
strategy	O
was	O
the	O
defense	O
of	O
the	O
U.S.	O
and	O
its	O
possessions	O
.	O
</s>
<s>
Most	O
air	O
forces	O
of	O
the	O
era	O
invested	O
heavily	O
in	O
dive	B-Application
bombers	I-Application
or	O
torpedo	O
bombers	O
for	O
these	O
roles	O
,	O
but	O
these	O
aircraft	O
generally	O
had	O
limited	O
range	O
;	O
long-range	O
strategic	O
reach	O
would	O
require	O
the	O
use	O
of	O
an	O
aircraft	O
carrier	O
.	O
</s>
<s>
The	O
Army	O
felt	O
the	O
combination	O
of	O
the	O
Norden	O
and	O
B-17	B-Application
Flying	I-Application
Fortress	I-Application
presented	O
an	O
alternate	O
solution	O
,	O
believing	O
that	O
small	O
formations	O
of	O
B-17s	O
could	O
successfully	O
attack	O
shipping	O
at	O
long	O
distances	O
from	O
the	O
USAAC	O
's	O
widespread	O
bases	O
.	O
</s>
<s>
At	O
some	O
point	O
the	O
company	O
started	O
using	O
the	O
pickle	O
barrel	O
imagery	O
,	O
to	O
reinforce	O
the	O
bombsight	B-Application
's	O
reputation	O
.	O
</s>
<s>
The	O
Grumman	O
TBF	O
Avenger	O
could	O
mount	O
the	O
Norden	O
,	O
like	O
the	O
preceding	O
Douglas	O
TBD	O
Devastator	O
,	O
but	O
combat	O
use	O
was	O
disappointing	O
and	O
eventually	O
described	O
as	O
"	O
hopeless	O
"	O
during	O
the	O
Guadalcanal	B-Application
Campaign	I-Application
.	O
</s>
<s>
After	O
earlier	O
combat	O
trials	O
proved	O
troublesome	O
,	O
the	O
Norden	B-Device
bombsight	I-Device
and	O
its	O
associated	O
AFCE	O
were	O
used	O
on	O
a	O
wide	O
scale	O
for	O
the	O
first	O
time	O
on	O
the	O
18	O
March	O
1943	O
mission	O
to	O
Bremen-Vegesack	O
,	O
Germany	O
.	O
</s>
<s>
As	O
these	O
missions	O
broke	O
the	O
Luftwaffe	O
,	O
missions	O
were	O
able	O
to	O
be	O
carried	O
out	O
at	O
lower	O
altitudes	O
or	O
especially	O
in	O
bad	O
weather	O
when	O
the	O
H2X	O
radar	B-Application
could	O
be	O
used	O
.	O
</s>
<s>
C	O
.	O
Ross	O
Greening	O
,	O
the	O
sight	O
was	O
mounted	O
to	O
the	O
existing	O
pilot	O
direction	O
indicator	O
,	O
allowing	O
the	O
bombardier	O
to	O
make	O
corrections	O
remotely	O
,	O
like	O
the	O
bombsights	B-Application
of	O
an	O
earlier	O
era	O
.	O
</s>
<s>
This	O
secure	O
facility	O
(	O
"	O
the	O
AFCE	O
and	O
Bombsight	B-Application
Shop	O
"	O
)	O
was	O
typically	O
in	O
one	O
of	O
the	O
base	O
's	O
Nissen	O
hut	O
(	O
Quonset	O
hut	O
)	O
support	O
buildings	O
.	O
</s>
<s>
The	O
Bombsight	B-Application
Shop	O
was	O
manned	O
by	O
enlisted	O
men	O
who	O
were	O
members	O
of	O
a	O
Supply	O
Depot	O
Service	O
Group	O
(	O
"	O
Sub	O
Depot	O
"	O
)	O
attached	O
to	O
each	O
USAAF	O
bombardment	O
group	O
.	O
</s>
<s>
These	O
shops	O
not	O
only	O
guarded	O
the	O
bombsights	B-Application
but	O
performed	O
critical	O
maintenance	O
on	O
the	O
Norden	O
and	O
related	O
control	O
equipment	O
.	O
</s>
<s>
As	O
the	O
end	O
of	O
World	O
War	O
II	O
neared	O
,	O
the	O
bombsight	B-Application
was	O
gradually	O
downgraded	O
in	O
its	O
secrecy	O
;	O
however	O
,	O
it	O
was	O
not	O
until	O
1944	O
that	O
the	O
first	O
public	O
display	O
of	O
the	O
instrument	O
occurred	O
.	O
</s>
<s>
A	O
similar	O
set	O
of	O
gyroscopes	O
provided	O
a	O
stabilized	O
platform	O
for	O
the	O
bombardier	O
to	O
sight	O
through	O
,	O
although	O
the	O
complex	O
interaction	O
between	O
the	O
bombsight	B-Application
and	O
autopilot	O
was	O
not	O
used	O
.	O
</s>
<s>
The	O
Carl	O
Zeiss	O
Lotfernrohr	B-Device
7	I-Device
,	O
or	O
Lotfe	O
7	O
,	O
was	O
an	O
advanced	O
mechanical	O
system	O
similar	O
to	O
the	O
Norden	B-Device
bombsight	I-Device
,	O
although	O
in	O
form	O
it	O
was	O
more	O
similar	O
to	O
the	O
Sperry	O
S-1	O
.	O
</s>
<s>
It	O
started	O
replacing	O
the	O
simpler	O
Lotfernrohr	O
3	O
and	O
BZG	O
2	O
in	O
1942	O
,	O
and	O
emerged	O
as	O
the	O
primary	O
late-war	O
bombsight	B-Application
used	O
in	O
most	O
Luftwaffe	O
level	O
bombers	O
.	O
</s>
<s>
Postwar	O
analysis	O
placed	O
the	O
overall	O
accuracy	O
of	O
daylight	O
precision	O
attacks	O
with	O
the	O
Norden	O
at	O
about	O
the	O
same	O
level	O
as	O
radar	B-Application
bombing	O
efforts	O
.	O
</s>
<s>
Over	O
Japan	O
,	O
bomber	O
crews	O
soon	O
discovered	O
strong	O
winds	O
at	O
high	O
altitudes	O
,	O
the	O
so-called	O
jet	O
streams	O
,	O
but	O
the	O
Norden	B-Device
bombsight	I-Device
worked	O
only	O
for	O
wind	O
speeds	O
with	O
minimal	O
wind	O
shear	O
.	O
</s>
<s>
This	O
extra	O
altitude	O
compounded	O
factors	O
that	O
could	O
previously	O
be	O
ignored	O
;	O
the	O
shape	O
of	O
and	O
even	O
the	O
paint	O
on	O
the	O
bomb	O
changed	O
its	O
aerodynamic	O
properties	O
and	O
,	O
at	O
that	O
time	O
,	O
nobody	O
knew	O
how	O
to	O
calculate	O
the	O
trajectory	B-Application
of	O
bombs	O
that	O
reached	O
supersonic	O
speeds	O
during	O
their	O
fall	O
.	O
</s>
<s>
Having	O
moved	O
to	O
night	O
bombing	O
,	O
where	O
visual	O
accuracy	O
was	O
difficult	O
under	O
even	O
the	O
best	O
conditions	O
,	O
they	O
introduced	O
the	O
much	O
simpler	O
Mark	B-Device
XIV	I-Device
bomb	I-Device
sight	I-Device
.	O
</s>
<s>
This	O
led	O
to	O
a	O
debate	O
within	O
the	O
RAF	O
whether	O
to	O
use	O
their	O
own	O
tachometric	O
design	O
,	O
the	O
Stabilized	B-Device
Automatic	I-Device
Bomb	I-Device
Sight	I-Device
,	O
or	O
use	O
the	O
Mk	O
.	O
</s>
<s>
XIV	O
ultimately	O
served	O
into	O
the	O
1960s	O
while	O
the	O
SABS	B-Device
faded	O
from	O
service	O
as	O
the	O
Lancaster	O
and	O
Lincoln	O
bombers	O
fitted	O
with	O
it	O
were	O
retired	O
.	O
</s>
<s>
In	O
the	O
postwar	O
era	O
,	O
the	O
United	O
States	O
mostly	O
stopped	O
developing	O
new	O
precision	O
bombsights	B-Application
.	O
</s>
<s>
Initially	O
this	O
was	O
because	O
of	O
the	O
war	O
's	O
end	O
but	O
,	O
as	O
budgets	O
increased	O
during	O
the	O
Cold	B-Application
War	I-Application
,	O
the	O
deployment	O
of	O
nuclear	O
weapons	O
meant	O
accuracies	O
of	O
around	O
were	O
sufficient	O
,	O
well	O
within	O
the	O
capabilities	O
of	O
existing	O
radar	B-Application
bombing	O
systems	O
.	O
</s>
<s>
Only	O
one	O
major	O
bombsight	B-Application
of	O
note	O
was	O
developed	O
,	O
the	O
Y-4	O
developed	O
on	O
the	O
Boeing	O
B-47	O
Stratojet	O
.	O
</s>
<s>
This	O
sight	O
combined	O
the	O
images	O
of	O
the	O
radar	B-Application
and	O
a	O
lens	O
system	O
in	O
front	O
of	O
the	O
aircraft	O
,	O
allowing	O
them	O
to	O
be	O
directly	O
compared	O
at	O
once	O
through	O
a	O
binocular	O
eyepiece	O
.	O
</s>
<s>
Bombsights	B-Application
on	O
older	O
aircraft	O
,	O
like	O
the	O
Boeing	O
B-29	O
Superfortress	O
and	O
the	O
later	O
B-50	O
,	O
were	O
left	O
in	O
their	O
wartime	O
state	O
.	O
</s>
<s>
When	O
the	O
Korean	O
War	O
began	O
,	O
these	O
aircraft	O
were	O
pressed	O
into	O
service	O
and	O
the	O
Norden	O
once	O
again	O
became	O
the	O
USAF	O
's	O
primary	O
bombsight	B-Application
.	O
</s>
<s>
This	O
occurred	O
again	O
when	O
the	O
Vietnam	O
War	O
started	O
;	O
in	O
this	O
case	O
retired	O
World	O
War	O
II	O
technicians	O
had	O
to	O
be	O
called	O
up	O
in	O
order	O
to	O
make	O
the	O
bombsights	B-Application
operational	O
again	O
.	O
</s>
<s>
The	O
bombsights	B-Application
were	O
used	O
in	O
Operation	O
Igloo	O
White	O
for	O
implanting	O
Air-Delivered	O
Seismic	O
Intrusion	O
Detectors	O
(	O
ADSID	O
)	O
along	O
the	O
Ho	O
Chi	O
Minh	O
Trail	O
.	O
</s>
