Citizen Nighthawk Series User manual


Crown ‘A’
(used for setting
time/date functions)
24-Hour Hand (PM Side)
24-Hour Time ‘AM’ Scale
Pilots Slide Rule
Dial Ring (Outer Scale)
Hour Hand
Crown ‘B’
(used for rotating
Pilots Slide Rule
Dial Ring
Minute Hand
24 Hour Hand (AM Side)
Slide Rule
Inner Scale
Date
Second Hand
24-Hour Time ‘PM’ Scale

Nighthawk Series (mvt. cal. B877) Quick Reference




















24 Hour Hand and 24 Hour sub dial




Crown ‘A’
Crown ‘B’
Date

Pilots Slide Rule Dial Ring (‘Outside scale’)



24-Hour Hand (PM Side)
Red tip indicates PM time
(12:00 PM to 11:59 PM)
24-Hour Hand (AM Side)
White tip indicates PM time
(12:00 AM to 11:59 AM)
Minute Hand
Second Hand
Hour Hand
Date Indicator
To set Base or ‘0’ position and then the time/date:
1) If your model features a screw down crown, unscrew crown ‘A’ from case.
2) When the second hand reaches 12:00, pull crown ‘A’ out two ‘clicks’. This will stop the second hand at the 12:00
or ‘0-position’.
3) With the crown ‘A’ pulled out two ‘clicks’, turn the crown clockwise until the PM side of the 24-hour indicator
(red tip side in this example) is pointing to 12:00 or ‘0-position’ (minute hand should also be pointing at 12:00 or
‘0-position’). Note: The AM side of the 24-hour indicator hand (white tip side in this example) indicates AM hours
(12:00 am through 11:59:59 am), while the PM side of the 24 Hour hand (red tip side in this example) indicates PM
hours (12:00 pm to 11:59:59 pm)
4) Push crown ‘A’ in 1 ‘click’. Rotate crown ‘A’ clockwise to move the hour hand until you see the date change. If
the hour hand is not already at the 12:00 position, continue to rotate the crown clockwise to move the hour hand to
the 12:00 position. This sets the hour to ‘midnight’ ensuring the date will change at night, rather than during the day.
5) Set the current date by rotating crown ‘A’ counterclockwise until the current date is shown in the date window.
The watch is now set for ‘midnight’ on the current date.
6) Pull crown ‘A’ out one ‘click’ to the time setting position.
7) Rotate crown ‘A’ clockwise to set your current time. Keep in mind that your watch is currently set at ‘midnight’
on today’s date.
8) Push crown ‘A’ to the closed position. The time, date and 24-hour time are now set. If your model features a
screw down crown, be sure to screw crown ‘A’ into the case.
Movement Caliber B877 Quick Setting Instructions
Crown ‘A’
24-Hour Time ‘AM’ Scale
24-Hour Time ‘PM’ Scale
Crown ‘B’

Flying distance and other navication calculations as well as
general calculations can be performed using the slide rul
located around the dial. This slide rule is not capable of
displaying decimal places, and as such, should only be used
as a general reference and as an alternative to more accurate
calculations.
Turning the crown, located at the 8:00 position, in either
direction allows the Outside Scale surrounding the dial to be
rotated.
Use of the Navigation Calculator
Crown for
rotating the
Outside Scale
surrounding
Inside Scale on
the dial
Outside Scale
(surrounding the dial
next to the case edge)
Inner scale
(just inside the
Outside rotating
scale)
Navigation Calculator
1. Calculation of time required
Question :
Solution:
Speed Index on Inner Scale
(triangle mark at 12:00 position)
How long does it take an airplane
flying at 180 knots to fly a distance
of 450 nautical miles?
Rotate the lower left crown in either
direction to set the '18' mark on the
'outside' scale to the "Speed Index" at
12:00. At this time, the point on the
inside scale that is aligned with '45' on
the outside scale indicates (2:30). The
answer is 2 hours and 30 minutes
2. Speed (Ground Speed) calculation
Question:
Solution:
What is the speed (ground speed) of an
airplane when it takes 1 hour and 20
minutes to fly a distance of 240
nautical miles?
Rotate the lower left crown in either
direction to align the '24' on the outside
scale with '1:20' (80) in the inside scale.
At this time, '18' is aligned with the
"Speed Index" on the inside scale and
the answer is 180 knots.
10
mark on
Inner Scale
10
mark on
Outside Scale

3. Flying Distance Calculation
Question :
Solution:
What is the flying distance traveled
in 40 minutes at a speed of 210
knots?
Rotate the lower left crown in either
direction to align the '21' on the
Outside Scale with the 'Speed Index' on
the Inside scale. The '40' of the Inside
scale is now pointing to '14'. The
answer is 140 nautical miles.
4. Fuel consumption rate calculation
Question:
Solution:
If 120 gallons of fuel are consumed in
30 minutes of flying time, what is the
fuel consumption rate?
Rotate the lower left crown in either
direction to align the '12' on the Outside
scale with '30' on the Inside scale. The
'Speed Index' on the Inside scale now
points to '24' on the Outside Scale. The
answer is 240 gallons per hour.
5. Fuel consumption calculation
Question:
Solution:
How much fuel is consumed in 6
hours at a fuel consumption rate of
250 gallons per hour?
Rotate the lower left crown in either
direction to align the '25' on the Outside
scale with the 'Speed Index' on the
Inside scale. The 6:00 is aligned with
'15'. The answer is 1,500 gallons.

6. Maximum flying hours
Question :
Solution:
With a fuel consumption rate of 220
gallons per hour and a fuel supply of
550 gallons, what is the maximum
flying hours?
Rotate the lower left crown in either
direction to align the '22' on the
Outside scale with the 'Speed Index' of
the inside scale. The '55' of the Outside
scale is now aligned with '2:30' on the
Inside scale. The answer is 2 hours and
30 minutes.
7. Conversion
Question:
Solution:
How do you convert 30 miles into
nautical miles and kilometeres?
Rotate the lower left crown in either
direction to align the '30' with the
'STAT' mark on the Inside scale. You
will notice that '26' is aligned with the
'NAUT' mark on the Inside scale and
'48.2' is indicated at the
'KILOMETERS' on the Inside scale.
General Calculation Functions
1. Multiplication
Question:
Solution:
What is 20 times 15 (20 x 15)?
Rotate the lower left crown in either
direction to align the '20' on the Outside
scale with the ' ' mark on the Inside
scale. Read the Outside scale at the '30'
mark which is aligned with '15' on the
Inside scale. Figure the number of
decimal places. The answer is 300.
Remember: decimal places cannot be
read on this scale.
10

2. Division
Question:
Solution:
What is 250 divided by 20 (250 / 20)?
Rotate the lower left crown in either
direction to align the '25' on the
Outside Scale with '20' on the inside
scale. Read the '12.5' mark that is
aligned with the ' ' mark on the Inside
Scale. Figure the number of decimal
places. The answer is 12.5.
3. Reading Ratios
Question:
Solution:
What is 'x' in the calculation thirty
divided by 20 equals 60x
(30/20 = 60x)
Rotate the lower left crown in either
direction to align the '30' on the Outside
Scale with the '20' on the inside scale.
At this time, the asnwer of '40' can be
read from the Inside scale
corresponding to '60' on the Outside
scale. In addition, the ratio of the value
on the Outside scale to the value of the
Inside scale is '30:20' at all positions on
the scale.
4. Determining the square root of a number
Question:
Solution:
What is the square root of 225?
Rotate the lower left crown in either
direction so that the value on the Inside
scale corresponding to '22.5' on the
Outside scale is equal to the value on
the Outside scale corresponding to ' '
on the Inside scale. Read off the answer
of 15 at that location.
10
10