The Nighthawk Series (mvt. cal. B877) is a sophisticated timepiece designed for quick identification and reference, particularly for flight-related calculations. It features a complex dial with multiple scales and hands, allowing for a wide range of functions beyond simple timekeeping.
Function Description
The primary function of the Nighthawk is to display time, date, and facilitate navigation calculations using its integrated slide rule.
- Timekeeping: The watch displays hours, minutes, and seconds through its Hour Hand, Minute Hand, and Second Hand. It also incorporates a 24-Hour Hand, which is crucial for distinguishing between AM and PM times. This hand has two sides, a shorter side corresponding to the 24-Hour sub-dial AM scale and a longer side for the 24-Hour sub-dial PM scale. The color of the tips of the 24-Hour hand corresponds to the color of the AM or PM scales, ensuring clarity in time indication.
- Date Display: A dedicated Date window indicates the current date. This date function operates on a 31-day month cycle and requires manual adjustment for months shorter than 31 days, as it is not perpetual.
- Navigation Calculator (Pilots Slide Rule): A key feature of this watch is the Pilots Slide Rule, which consists of an Inner Scale and an Outer Scale (Dial Ring). This slide rule is designed for various flight-related calculations, as well as general mathematical operations. It can be used to determine:
- Time Required: Calculate the time needed to travel a certain distance at a given speed.
- Speed (Ground Speed): Determine the speed of an aircraft based on the distance traveled and the time taken.
- Flying Distance: Calculate the distance traveled given speed and time.
- Fuel Consumption Rate: Ascertain the rate at which fuel is consumed based on the amount of fuel used and flying time.
- Fuel Consumption: Calculate the total fuel consumed over a specific duration at a known consumption rate.
- Maximum Flying Hours: Determine the maximum flight duration based on fuel supply and consumption rate.
- Conversions: Convert between different units, such as miles to nautical miles and kilometers.
- General Calculations: Perform basic mathematical operations like multiplication, division, reading ratios, and determining square roots.
Usage Features
The Nighthawk watch is designed with user-friendly controls for setting time, date, and operating the slide rule.
- Crown 'A': This crown is used for setting time and date functions. For models featuring a screw-down crown, it must be unscrewed from the case before operation.
- Setting Base or '0' Position: To ensure accurate time and date setting, the watch can be brought to a base or '0' position. This involves pulling Crown 'A' out two 'clicks' when the second hand reaches 12:00, which stops the second hand at the '0-position'. The 24-hour indicator (specifically the PM side, often with a red tip) is then turned clockwise to point to 12:00 or '0-position', ensuring the minute hand also aligns.
- Setting Date: After setting the '0' position, Crown 'A' is pushed in one 'click'. Rotating it clockwise moves the hour hand until the date changes, indicating midnight. The current date is then set by rotating Crown 'A' counterclockwise until the desired date appears in the date window.
- Setting Time: With the date set to midnight, Crown 'A' is pulled out one 'click' to the time setting position. Rotating it clockwise sets the current time, keeping in mind the watch is currently set to midnight for the current date. Once set, Crown 'A' is pushed to the closed position. If it's a screw-down crown, it should be screwed back into the case.
- Crown 'B': This crown is specifically used for rotating the Pilots Slide Rule Dial Ring (Outer Scale). Turning Crown 'B' in either direction allows the user to align the Outer Scale with the Inner Scale for various calculations.
- 24 Hour Hand and 24 Hour Sub-dial: The 24 Hour hand is crucial for setting the correct AM or PM time. Its shorter side corresponds to the AM scale, and its longer side corresponds to the PM scale. The color coding of the hand tips and scales helps in quick identification. Proper reference to this hand is essential during time setting to ensure the date changes at the correct time (midnight).
- Pilots Slide Rule Dial Ring (Outer Scale): This ring is rotated by Crown 'B' and is used in conjunction with the Inner Scale for flight-related calculations. Instructions refer to it as the 'Outside scale', and readings are compared to the 'Inner scale' during calculations. The slide rule is a reference tool and is not designed for displaying decimal places, making it suitable for general estimations rather than precise measurements.
Maintenance Features
While the provided text does not explicitly detail maintenance features, the presence of a screw-down Crown 'A' on some models suggests a design consideration for water resistance and protection of the internal movement.
- Screw-down Crown 'A': For models equipped with a screw-down Crown 'A', it is important to unscrew it before making any adjustments to time or date and to screw it back into the case once adjustments are complete. This mechanism typically helps to prevent water and dust from entering the watch case, contributing to the longevity and reliability of the movement.
In summary, the Nighthawk Series (mvt. cal. B877) is a robust and versatile pilot's watch, combining precise timekeeping with an integrated navigation calculator, making it a valuable tool for aviation enthusiasts and professionals alike. Its intuitive controls and clear dial markings facilitate efficient use of its numerous functions.
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