Duties and Responsibilities of
THE NAVIGATOR
Excerpt from the Pilot Training
Manual of the B-17 Flying Fortress
The navigator's job is to direct your
flight from departure to destination and return. He must know the exact
position of the airplane at all times.
Navigation is the art of determining geographic positions by means of
(a) pilotage, (b) dead reckoning, (c) radio, or (d) celestial navigation,
or any combination of these 4 methods. By any one or combination of
methods the navigator determines the position of the airplane in relation
to the earth.
Pilotage
Pilotage is the method of determining the airplane's position by visual
reference to the ground. The importance of accurate pilotage cannot
over-emphasized. In combat navigation, all bombing targets are approached
by pilotage, and in many theaters the route is maintained by pilotage.
This requires not merely the vicinity type, but pin-point pilotage. The
exact position of the airplane must be known not within 5 miles but within
¼ of a mile.
The navigator does this by constant reference to groundspeeds and ETA's
(estimated times of arrival) established for points ahead, the ground, and
to his maps and charts. During the mission, so long as he can maintain
visual contact with the ground, the navigator can establish these
pin-point positions so that the exact track of the airplane will be known
when the mission is completed.
Dead Reckoning
Dead reckoning is the basis of all other types of navigation. For
instance, if the navigator is doing pilotage and computes ETA's for points
ahead, he is using dead reckoning.
Dead reckoning determines the position of the airplane at any given
time by keeping an account of the track and distance flown over the
earth's surface from the point of departure or last known position.
Dead reckoning can be subdivided into two classes:
- Dead reckoning as a result of a series of known positions
obtained by some other means of navigation.
For example, you, as pilot, start on a mission from London to
Berlin at 25,000 feet. For the first hour your navigator keeps track
by pilotage; at the same time recording the heading and airspeed which
you are holding. According to plan, at the end of the first hour the
airplane goes above the clouds, thus losing contact with the ground.
By means of dead reckoning from his last pilotage point, the navigator
is able to tell the position of the aircraft at any time. The first
hour's travel has given him the wind prevalent at altitude, and the
track and groundspeed being made. By computing track and distance from
the last pilotage point, he can always tell the position of the
airplane. When your airplane comes out of the clouds near Berlin, the
navigator will have a very close approximation of his exact position,
and will be able to pick up pilotage points quickly.
- Dead reckoning as a result of visual references other than
pilotage.
When flying over water, desert, or barren land, where no reliable
pilotage points are available, accurate DR navigation still can be
performed. By means of the drift meter the navigator is able to
determine drift, the angle between the heading of the airplane and its
track over the ground. The true heading of the airplane is obtained by
application of compass error to the compass reading. The true heading
plus or minus the drift (as read on the drift meter) gives the track
of the airplane. At a constant airspeed, drift on 2 or more headings
will give the navigator information necessary to obtain the wind by
use of his computer. Groundspeed is computed easily once the wind,
heading, and airspeed are known. So, by constant recording of true
heading, true airspeed, drift, and groundspeed, the navigator is able
to determine accurately the position of the airplane at any given
time. For greatest accuracy, the pilot must maintain constant courses
and airspeeds. If course or airspeed is changed, notify the navigator
so he can record these changes.
Radio
Radio navigation makes use of various radio aids to determine position.
The development of many new radio devices has increased the use of radio
in combat zones. However, the ease with which radio aids can be jammed, or
bent, limits the use of radio to that of a check on DR and pilotage. The
navigator, in conjunction with the radio man, is responsible for all radio
procedures, approaches, etc., that are in effect in the theater.
Celestial
Celestial navigation is the science of determining position by
reference to 2 or more celestial bodies. The navigator uses a sextant,
accurate time, and many tables to obtain what he calls a line of position.
Actually this line is part of a circle on which the altitude of the
particular body is constant for that instant of time. An intersection of 2
or more of these lines gives the navigator a fix. These fixes can be
relied on as being accurate within approximately 10 miles. One reason for
inaccuracy is the instability of the airplane as it moves through space,
causing acceleration of the sextant bubble (a level denoting the
horizontal). Because of this acceleration, the navigator takes
observations over a period of time so that the acceleration error will
cancel out to some extent. If the navigator tells the pilot when he wishes
to take an observation, extremely careful flying on the part of the pilot
during the few minutes it takes to make the observation will result in
much greater accuracy. Generally speaking, the only celestial navigation
used by a combat crew is during the delivering flight to the theater. But
in all cases celestial navigation is used as a check on dead reckoning and
pilotage except where celestial is the only method available, such as on
long over-water flights, etc.
Instrument Calibration
Instrument calibration is an important duty of the navigator. All
navigation depends directly on the accuracy of his instruments. Correct
calibration requires close cooperation and extremely careful flying by the
pilot. Instruments to be calibrated include the altimeter, all compasses,
airspeed indicators, alignment of the astrocompass, astrograph, and drift
meter, and check on the navigator's sextant and watch.
Pilot-Navigator Preflight Planning
- Pilot and navigator must study flight plan of the route to be flown
and select alternate air fields.
- Study the weather with the navigator. Know what weather you are
likely to encounter. Decide what action is to be taken. Know the
weather conditions at the alternate airfields.
- Inform your navigator at what airspeed and altitude you wish to fly
so that he can prepare his flight plan.
- Learn what type of navigation the navigator intends to use: pilotage,
dead reckoning, radio, celestial, or a combination of all methods.
- Determine check points; plan to make radio fixes.
- Work out an effective communication method with your navigator to be
used in flight.
- Synchronize your watch with your navigator's.
Pilot-Navigator in Flight
- Constant course - For accurate navigation, the
pilot -- you -- must fly a constant course. The navigator has many
computations and entries to make in his log. Constantly changing
course makes his job more difficult. A good navigator is supposed to
be able to follow the pilot, but he cannot be taking compass readings
all the time.
- Constant airspeed must be held as nearly as
possible. This is as important to the navigator as is a constant
course in determining position.
- Precision flying by the pilot greatly affects the
accuracy of the navigator's instrument readings, particularly
celestial readings. A slight error in celestial reading can cause
considerable error in determining positions. You can help the
navigator by providing as steady a platform as possible from which he
can take readings. The navigator should notify you when he intends to
take readings so that the airplane can be leveled off and flown as
smoothly as possible, preferably by using the
automatic pilot. Do not allow your navigator to be disturbed while
he is taking celestial readings.
- Notify the navigator of any change in flight, such
as change in altitude, course, or airspeed. If change in flight plan
is to be made, consult the navigator. Talk over the proposed change so
that he can plan the flight and advise you about it.
- If there is doubt about the position of the airplane, pilot and
navigator should get together, refer to the navigator's flight log,
talk the problem over and decide together the best course of action to
take.
- Check your compasses at intervals with those of the navigator,
noting any deviation.
- Require your navigator to give position reports at intervals.
- You are ultimately responsible for getting the airplane to its
destination. Therefore, it is your duty to know your position at all
times.
- Encourage your navigator to use as many navigation methods as
possible as a means of double-checking.
Post-flight Critique
After every flight get together with the navigator and discuss the
flight and compare notes. Go over the navigator's log. If there have been
serious navigational errors, discuss them with the navigator and determine
their cause. If the navigator has been at fault, caution him that it is
his job to see that the same mistake does not occur again. If the error
has been caused by faulty instruments, see that they are corrected before
another navigation mission is attempted. If your flying has contributed to
inaccuracy in navigation, try to fly a better course next time.
Miscellaneous Duties
The navigator's primary duty is navigating your airplane with a high
degree of accuracy. But as a member of the team, he must also have a
general knowledge of the entire operation of the airplane.
He has a .50-cal. machine gun at his station, and he must be able to
use it skillfully and to service it in emergencies.
He must be familiar with the oxygen system, know how to operate the
turrets, radio equipment, and fuel transfer system.
He must know the location of all fuses and spare fuses, lights and
spare lights, affecting navigation.
He must be familiar with emergency procedures, such as the manual
operation of landing gear, bomb bay doors, and flaps, and the proper
procedures for crash landings, ditching, bailout, etc.
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