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NORDEN OPERATIONS MANUAL
Acknowledgement: Information from Dickweed Heavy Bomber
Group,
http://www.bombergroup.com/
Operation of the Norden Mark 15/M-Series Bombsight
I. PREPARATION FOR BOMBING RUN - to be performed 30 to 45 minutes
before the airplane is expected to reach the target area.
A. Check stabilizer gyro to insure that gyro is operating and has
attained normal running speed before proceeding further.
B. Check torque motor to insure torque motor is operating.
C. Check PDI to insure PDI system is operating properly.
D. Turn on the bombsight gyro by moving the bombsight toggle switch
to the "ON" position.
E. Align bombsight clutch by aligning the course centering marks on
the bombsight clutch connecting rod with the course centering
pointer.
F. Make train bombing adjustment. If train bombing is to be used the
sight should be adjusted to place the mean point of the impact on
the target. Loosen the knurled nut on the trail sporting arm, moving
the trail arm to the correct mil value, and tightening the knurled
nut on the trail sporting arm.
G. Compute true air speed and bombing altitude using the E-6B
computer, or equivalent.
H. Set disc speed and trail from the bombing tables and set this
data into the sight.
1. Set the disc speed into the sight by turning the altitude knob in
a clockwise direction. Make sure the "change speed" lever is in the
correct position.
a. Move the telescope motor toggle switch to the "ON" position and
check disc speed with a type 43D-3 bombsight disc speed tachometer.
b. Adjust the altitude knob until the correct disc speed reading is
obtained on the tachometer.
c. Continue checking and adjusting until the correct speed, within
1/2 rpm, is obtained on at least three checks.
d. Move the telescope motor toggle switch to the "OFF" position.
2. Set trail into the sight by loosening the knurled nut, moving the
trail arm to the correct mil value as indicated by the scale on the
trail plate and tightening the knurled knob to lock the trail arm at
this setting.
I. Check the reflex optics - on bombsights equipped with the type
X-1 reflex sight, check this unit to make certain that its indicator
is coincident with the telescopic indicator.
1. If these indicators are not coincident, align them by moving the
reflex optics clutch to its inoperative position, manually rotating
the reflex optic head until its indicator is at the same angle as
the bombsight telescopic indicator, and re-engaging the clutch.
2. Turn the rheostat which controls the light that illuminates the
reticule of the reflex sight to provide the desired intensity of
illumination of the cross on the reflector plate.
J. Move the telescopic motor drive clutch into engaged position and
make sure the telescopic sector indicator is positioned at, or near,
the maximum sighting angle for convenience in picking up the target
when it is first sighted.
K. Preset dropping angle from the automatic bombing computer, or
from the E-6B, and use the rate knob to move the rate sector
indicator to the proper setting on the tangent scale.
L. Adjust the B-7 bombsight mount to level the stabilizer. Use the
leveling bubbles mounted on the top of the bombsight gyro housing to
judge the vertical. Make sure that the bombsight gyro is caged and
that the airplane is flying straight and level before performing
this operation. Care exercised in obtaining a good level will
eliminate the necessity for making large corrections to level the
bombsight gyro during the bombing run.
II. BOMBING RUN - the synchronous bombing run is started when the
airplane reaches the initial point specified at the preliminary
briefing. The bombardier should contact the pilot on the interphone
at this point and coordinate the remainder of the run. The actual
technique that will be employed will vary with the nature of the
mission. In general, however, each of the following steps must be
performed in much the same sequence as they are presented.
A. Switch on the bomb rack by moving the toggle switch or switches
to "ON" position to select the desired bomb bay or rack.
B. Open bomb bay doors by moving the bomb bay door toggle switch to
the "ON" position.
C. Un-cage the bombsight gyro as soon as the airplane is flying
straight and level.
D. Swing the sight onto the target, or if equipped with the type X-1
reflex optics, align the vertical cross hair with the target.
1. Grasp the directional arm jaws with the left hand, if flying on
the autopilot, and hold the autopilot clutch to avoid turning the
airplane while lining the sight up with the target.
2. Grasp the turn and drift knobs with the right hand and swing the
bombsight head into alignment with the target.
E. Use the search knob or displacement knob to swing the horizontal
cross hair onto the target.
F. Move the telescope motor toggle switch to the "ON" position.
G. If evasive action is to be taken, disengage autopilot clutch to
permit turning the airplane with the bombardier's turn knob.
H. Start evasive action, if these tactics are to be employed during
the approach to the target. These maneuvers, when employed, will be
limited to turns of from 5 degrees to 15 degrees and the time on
each leg will be from 10 to 20 seconds. The bombardier will turn the
airplane in these maneuvers by moving the bombardier's turn knob in
the appropriate direction and amount. These turns should be planned
to as to gradually work the airplane upwind so that the final turn
onto the target can be made in a downwind direction.
1. Level the bombsight gyro, if necessary, by using the leveling
knobs to center the bubbles in the spirit-type levels mounted on the
gyro housing.
2. Hold the bombsight manually to keep the line of sight on the
target until the bombsight clutch is engaged to stabilize the
bombsight in azimuth.
3. Move the horizontal cross hair back on the target with the
displacement knob.
4. Make a note of the sighting angle which will indicate the time to
turn onto the target to complete a bombing run of the desired
duration. This value can be obtained from the automatic bombing
computer, or the bombing tables, for 30-second runs. For runs of
longer or shorter duration the proper sighting angle will have been
computed on the ground before takeoff.
5. Watch the telescope sector indicator for the time to turn on the
target for the bombing run and plan the evasive action accordingly.
6. Stop evasive action and turn the airplane on the target for the
bombing run when the telescope sector indicator reaches the sighting
that signals the start of a bombing run of the desired duration.
I. Obtain drift angle from the automatic bombing computer, or from
the E-6B computer, and turn the airplane, while holding the line of
sight on the target, until the correct drift angle is indicated on
the drift scale. Engage the bombsight clutch as soon as the drift
has been preset.
J. Place the vertical cross hair on the target with the turn knob.
Double grip the turn and drift knobs to stop relative motion between
the cross hair and the target. Only very fine adjustments should be
required, inasmuch as the operation will consist simply of refining
the course that was established when the drift angle was preset.
K. Check level of bombsight gyro to make sure the airplane is flying
straight and level.
L. Place the horizontal cross hair on the target with the
displacement knob. Use the rate knob to stop relative motion between
the cross hair and the target. Care should be exercised not to over
control at this point. Only very fine adjustments of the rate knob
should be required, inasmuch as this operation will consist simply
of refining the rate that was established when the dropping angle
was preset.
M. Move the release lever up to firing position and lock in firing
position by moving the lever upward to the limit of its travel and
pressing the small locking pin into the operative position.
N. Extreme caution must be taken not to over control at this point.
If the preceding operations have been carefully performed, a good
course and a good rate have been established. Any adjustment made at
this point should only be for the purpose of removing any very small
errors still present. The gear ratios are such that any major
adjustments at this time in course and/or rate may well result in
much larger bombing errors than if the small remaining errors are
accepted and the cross hairs moved back on the target by means of
the turn and displacement knobs.
O. When the telescope sector indicator drives into coincidence with
the rate sector indicator bombs are released automatically.
P. Notify the pilot that the bombs have been released.
Q. Prepare the equipment for possible violent evasive maneuvers.
1. Close bomb bay doors.
2. Cage bombsight gyro.
3. Engage autopilot clutch and disengage bombsight clutch.
4. Turn off telescope motor.
5. Turn off bombsight gyro.
6. Latch release lever.
7. Turn off switches to bomb rack or racks.
8. Return altitude knob to minimum speed stop.
9. Return telescope sector indicator to maximum setting.
10. Return trail arm, and trail spotting arm if sight is so
equipped, to zero.
11. Cover bombsight.
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