Duties and Responsibilities of
THE BOMBARDIER
Excerpt from the Pilot Training Manual of the B-17
Flying Fortress
Accurate and effective bombing is the ultimate purpose of your
entire airplane and crew. Every other function is preparatory to
hitting and destroying the target.
That's your bombardier's job. The success or failure of the
mission depends upon what he accomplishes in that short interval
of the bombing run.
When the bombardier takes over the airplane for the run on the
target, he is in absolute command. He will tell you what he wants
done, and until he tells you "Bombs away," his word is
law.
A great deal, therefore, depends on the understanding between
bombardier and pilot. You expect your bombardier to know his job
when he takes over. He expects you to understand the problems
involved in his job, and to give him full cooperation. Teamwork
between pilot and bombardier is essential.
Under any given set of conditions -- groundspeed, altitude,
direction, etc. -- there is only one point in space where a bomb
may be released from the airplane to hit a predetermined object on
the ground.
There are many things with which a bombardier must be
thoroughly familiar in order to release his bombs at the right
point to hit this predetermined target.
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He must know and understand his bombsight, what it does, and
how it does it. |
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He must thoroughly understand the operation and upkeep of
his bombing instruments and equipment.
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He must know that his racks, switches, controls, releases,
doors, linkage, etc., are in first class operating condition.
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He must understand the automatic pilot as it pertains to
bombing. |
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He must know how to set it up, make any adjustments and
minor repairs while in flight.
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He must know how to operate all gun positions in the
airplane. |
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He must know how to load and clear simple stoppages and jams
of machine guns while in flight.
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He must be able to load and fuse his own bombs.
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He must understand the destructive power of bombs and must
know the vulnerable spots on various types of targets.
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He must understand the bombing problem, bombing
probabilities, bombing errors, etc.
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He must be thoroughly versed in target identification and in
aircraft identification. |
The bombardier should be familiar with the duties of all
members of the crew and should be able to assist the navigator in
case the navigator becomes incapacitated.
For the bombardier to be able to do his job, the pilot of the
aircraft must place the aircraft in the proper position to arrive
at a point on a circle about the target from which the bombs can
be released to hit the target.
Consider the following conditions which affect the bomb dropped
from an airplane:
- ALTITUDE: Controlled
by the pilot. Determines the length of time the bomb is
sustained in flight and affected by atmospheric conditions,
thus affecting the range (forward travel of the bomb) and
deflection (distance the bomb drifts in a crosswind with
respect to airplane's ground track).
- TRUE AIRSPEED: Controlled
by the pilot. The measure of the speed of the airplane through
the air. It is this speed which is imparted to the bomb and
which gives the bomb its initial forward velocity and,
therefore, affects the trail of the bomb, or the distance the bomb lags behind the
airplane at the instant of impact.
- BOMB BALLISTICS:
Size, shape and density of the bomb, which determines its air
resistance. Bombardier uses bomb ballistics tables to account
for type of bomb.
- TRAIL: Horizontal
distance the bomb is behind the airplane at the instant of
impact. This value, obtained from bombing tables, is set in
the sight by the bombardier. Trail is affected by altitude,
airspeed, bomb ballistics and air density, the first three
factors being controlled by the pilot.
- ACTUAL TIME OF FALL:
Length of time the bomb is sustained in air from instant of
release to instant of impact. Affected by altitude, type of
bomb and air density. Pilot controls altitude to obtain a
definite actual time of fall.
- GROUNDSPEED:
The speed of the airplane in relation to the earth's surface.
Groundspeed affects the range of the bomb and varies with the
airspeed, controlled by the pilot. Bombardier enters
groundspeed in the bombsight through synchronization on the
target. During this process the pilot must maintain the
correct altitude and constant airspeed.
- DRIFT:
Determined by the direction and velocity of the wind, which
determines the distance the bomb will travel downwind from the
airplane from the instant the bomb is released to its instant
of impact. Drift is set on the bombsight by the bombardier during the
process of synchronization and setting up course.
The above conditions indicate that the pilot plays an important
part in determining the proper point of release of the bomb.
Moreover, throughout the course of the run, as explained below,
there are certain preliminaries and techniques which the pilot
must understand to insure accuracy and minimum loss of time.
Prior to takeoff the pilot must ascertain that the airplane's
flight instruments have been checked and found accurate. These are
the altimeter, airspeed indicator, free air temperature gauge and
all gyro instruments. These instruments must be used to determine
accurately the airplane's attitude.
The Pilot's Preliminaries
The autopilot
and PDI should
be checked for proper operation. It is very important that PDI and
autopilot function perfectly in the air; otherwise it will be
impossible for the bombardier to set up an accurate course on the
bombing run. The pilot should thoroughly familiarize himself with
the function of both the C-1 autopilot and PDI.
If the run is to be made on the autopilot, the pilot must
carefully adjust the autopilot before reaching the target area.
The autopilot must be adjusted under the same conditions that will
exist on the bombing run over the target. For this reason the
following factors should be taken into consideration and
duplicated for initial adjustment.
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Speed, altitude and power settings at which run is to be
made.
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Airplane trimmed at this speed to fly hands off with bomb
bay doors opened. |
The same condition will exist during the actual run, except
that changes in load will occur before reaching the target area
because of gas consumption. The pilot will continue making
adjustments to correct for this by disengaging the autopilot
elevator control and re-trimming the airplane, then re-engaging
and adjusting the autopilot trim of the elevator.
Setting Up the Autopilot
One of the most important items in setting up the autopilot for
bomb approach is to adjust the turn compensation knobs so that a
turn made by the bombardier will be coordinated and at constant
altitude. Failure to make this adjustment will involve difficulty
and delay for the bombardier in establishing an accurate course
during the run with the possibility that the bombardier may not be
able to establish a proper course in time, the result being
considerably large deflection errors in point of impact.
Uncoordinated turns by the autopilot on the run cause erratic
lateral motion of the cross hair of the bombsight when sighting on
target. The bombardier in setting up course must eliminate any
lateral motion of the fore-and-aft hair in relation to the target
before he has the proper course set up. Therefore, any erratic
motion of the cross hair requires an additional correction by the
bombardier. which would not be necessary if autopilot was adjusted
to make coordinated turns.
USE OF THE PDI:
The same is true if PDI is used on the bomb run. Again,
coordinated smooth turns by the pilot become an essential part of
the bomb run. In addition to added course corrections necessitated
by uncoordinated turns, skidding and slipping introduce small
changes in airspeed affecting synchronization of the bombsight on
the target. To help the pilot flying the run on PDI, the airplane
should be trimmed to fly practically hands off.
Assume that you are approaching the target area with autopilot
properly adjusted. Before reaching the initial point (beginning of
bomb run) there is evasive action to be considered. Many different
types of evasive tactics are employed, but from experience it has
been recommended that the method of evasive action be left up to
the bombardier, since the entire anti- aircraft pattern is fully
visible to the bombardier in the nose.
EVASIVE ACTION:
Changes in altitude necessary for evasive action can be
coordinated with the bombardier's changes in direction at specific
intervals. This procedure is helpful to the bombardier since he
must select the initial point at which he will direct the airplane
onto the briefed heading for the beginning of the bomb run.
Should the pilot be flying the evasive action on PDI (at the
direction of the bombardier) he must know the exact position of
the initial point for beginning the run, so that he can fly the
airplane to that point and be on the briefed heading. Otherwise,
there is a possibility of beginning to run too soon, which
increases the airplane's vulnerability, or beginning the run too
late, which will affect the accuracy of the bombing. For best
results the approach should be planned so the airplane arrives at
the initial point on the briefed heading, and at the assigned
bombing altitude and airspeed.
At this point the bombardier and pilot as a team should exert
an extra effort to solve the problem at hand. It is now the
bombardier's responsibility to take over the direction of flight,
and give directions to the pilot for the operations to follow. The
pilot must be able to follow the bombardier's directions with
accuracy and minimum loss of time, since the longest possible bomb
run seldom exceeds 3 minutes. Wavering and indecision at this
moment are disastrous to the success of any mission, and during
the crucial portion of the run, flak and fighter opposition must
be ignored if bombs are to hit the target. The pilot and
bombardier should keep each other informed of anything which may
affect the successful completion of the run.
HOLDING A LEVEL: Either
before or during the run, the bombardier will ask the pilot for a
level. This means that the pilot must accurately level his
airplane with his instruments (ignoring the PDI). There should be
no acceleration of the airplane in any direction, such as an
increase or decrease in airspeed, skidding or slipping, gaining or
losing altitude.
For the level the pilot should keep a close check on his
instruments, not by feel or watching the horizon. Any acceleration
of the airplane during this moment will affect the bubbles
(through centrifugal force) on the bombsight gyro, and the
bombardier will not be able to establish an accurate level.
For example, assume that an acceleration occurred during the
moment the bombardier was accomplishing a level on the gyro. A
small increase in airspeed or a small skid, hardly perceptible, is
sufficient to shift the gyro bubble liquid 1 degree or more. An
erroneous tilt of 1 degree on the gyro will cause an error of
approximately 440 feet in the point of impact of a bomb dropped
from 20,000 feet, the direction of error depending on direction of
tilt of gyro caused by the erroneous bubble reading,
HOLDING ALTITUDE AND AIRSPEED:
As the bombardier proceeds to set up his course (synchronize) , it
is absolutely essential that the pilot maintain the selected
altitude and air- speed within the closest possible limits. For
every additional 100 feet above the assumed 20,000-foot bombing
altitude, the bombing error will increase approximately 30 feet,
the direction of error being over. For erroneous airspeed, which
creates difficulty in synchronization on the target, the bombing
error will be approximately 170 feet for a 10 mph change in
airspeed. Assuming the airspeed was 10 mph in excess, from 20,000
feet, the bomb impact would be short 170 feet.
The pilot's responsibility to provide a level and to maintain a
selected altitude and airspeed within the closest limits cannot be
over-emphasized.
If the pilot is using PDI (at the direction of the bombardier)
instead of autopilot, he must be thoroughly familiar with the
corrections demanded by the bombardier. Too large a correction or
too small a correction, too soon or too late, is as bad as no
correction at all. Only through prodigious practice flying with
the PDI can the pilot become proficient to a point where he can
actually perform a coordinated turn, the amount and speed
necessary to balance the bombardier's signal from the bombsight.
Erratic airspeeds, varying altitudes, and poorly coordinated
turns make the job of establishing course and synchronizing doubly
difficult for both pilot and bombardier, because of the necessary
added corrections required. The resulting bomb impact will be far
from satisfactory.
After releasing the bombs, the pilot or bombardier may continue
evasive action -- usually the pilot, so that the bombardier may
man his guns.
The pilot using the turn control may continue to fly the
airplane on autopilot, or fly it manually, with the autopilot in a
position to he engaged by merely flipping the lock switches. This
would provide potential control of the airplane in case of
emergency.
REDUCING CIRCULAR ERROR:
One of the greatest assets towards reducing the circular error of
a bombing squadron lies in the pilot's ability to adjust the
autopilot properly, fly the PDI, and maintain the designated
altitude and airspeeds during the bombing run. Reducing the
circular error of a bombing squadron reduces the total number of
aircraft required to destroy a particular target. For this reason
both pilot and bombardier should work together until they have
developed a complete understanding and confidence in each other.
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