The Norden Bomb Sight manual

REASONS• FOR VARIOUS STEPS OF CALIBRATION

A. Set pedestal reference index.

1.

Pedestal reference

index

is determined to

align the plane of rotation of the point of inter-

section of the cross hairs with compass heading of

the

grid lines.

zero drift

in order to remove any

cross trail tilt in the optics.

(1)

A tilt in

the

optics would change

the compass heading of the plane of

rotation of

the cross hairs.

2.

When "|" is accomplished,

set the pedestal

so that using

it as

a guide

to either side

stabilizer may be positioned accurately

or around a complete 1800

grid lines on true heading.

"A" above, the plane of rotation of the

point of intersection of the cross

is align-

ed with the compass heading of the

grid lines land

the sight and

stabilizer are fixed

to the

stand in

this position so as to maintain this relationship).

Maintaining this relationship, rotate the base of

grid lines

therefore the

plane of rotation of the point of intersection of

the hairs) are

aligned with one of the cardinal

headings).

Steps "A" and *B" are not necessary

Step "A": makes it possible to

switch quickly

from one cardinal heading to another.

(2)

Step "B": If

precession runs are

made on cardinal headings, either--but not both--

the gyro gudgeon bearings or the cardan gudgeon

bearings will

tilt as

a result of apparent easter-

ly precession.

By using only one set of bearings

at a time, it is possible to approximate standard

figures for easterly precession and north hook.

If the sight were not on a cardinal heading, both

sets of balancing weights would have to be used in

order

to make corrections, and it would be im-

possible to calculate how

much to rotate each

Check Alignment of Vertical Cross Hair.

This check determines whether the plane

pass head this must be di

pass heading as the fore and aft cross

This must be or it would be impossible

to set up

The optics must be driven

the

same heading as that of the fore and aft cross

Set

reference

sight

and

90°

Establish

hairs

the

stand

until

the

a.

except

for

(1)

weight.

C.

along

the

com-

hair.

a.

along