The Norden Bomb Sight manual

Synchron-

ous Sight

The type of bombsight used in high level pre-

cision bombing is a synchronous

sight.

The term

"synchronous"

means

that one thing will maintain

the same relationship to

another under constantly

changing conditions.

In a synchronous bombsight,

that means that the rate of angular drive of the

optics keeps pace with

the rate of angular change

of the

sighting

angle--provided the sight is syn-

chronized. This means that when the sighting

angle is

say 50° and

the transverse hair rests

synchronized

angle reaches 40°

upon the target, when the sighting

, the transverse hair will like-

wise be at 40° from the vertical and in that con-

dition

rest upon the target.

When sighting through the optics, there are

twu points; one

hair.

The

above and one below

transverse

first is the position of the eye which

sights to the transverse

hair; the

point of projection

second

is the

to the ground of this

line

of

sight.

As the plane approaches

the target, with

sight synchronized,

the point of projection

would

move

along the

surface of the earth

at a

speed

equal to velocity of closure.

The

fact is

that

the transverse

hair land therefore this point of

projection) remains on the target and doesn't move

relative to it.

This is because

the

"forward™

velocity of closure of the plane is equalled ex-

actly by the rearward" velocity of the point of

projection

relative to the target.

All this means

the rate of angular closure of the transverse hair

is exactly equal to the rate of change of the

sighting angle.

No sight synchronizes itself: It must be

properly adjusted and operated in order for syn-

chronization.

The manual act of synchronizing causes the

optics to drive at the correct speed for synchron-

ization

up the correct actual range angle

for the given

altitude, velocity of closure, and

trail characteristic of

the bomb.

with this cor-

rect actual

range angle

set up,

the or should

caused

to be released the correct actual ra033

distance away from

the target.

Norden

Bombsight,

synchronized,

causes a

to be positloned at the

correct actual

angle measured off from its

zero degrees

(tan value)

position.