Citizen Promaster Sky Watch Review

This time we’re going to review in details Citizen Promaster Sky watch, model AS4020-28E, which belongs to the category of pilot watches.


Case, dials and design

The case of this watch is made of stainless steel with a brushed surface. With diameter of 45mm (without crown) and thickness of 14mm this watch falls into the category of massive watches. Despite the size, the watch stands pretty well even on a narrow wrist. Declared water resistance is 200m which is quite impressive considering that this is a pilot’s watch. The build quality and finishing are really great, and it is important to note that the watches in this series can be purchased in versions made of Titanium + IP material, also known as the Super Titanium. This material has surface hardness as 5 times harder as stainless steel and it’s also 40% lighter. It is made with a special technology which is property of Citizen company.

Citizen Promaster Sky AS4020-28E 02

Crowns are not screw-down and are very pleasant to handle thanks to its embossed surface. The crown on the right side has embossed  Citizen logo. Corona is fixed, polished with embossed surface, and a sapphire glass with anti-reflective coating, it is straight and slightly elevated above the corona.

This model comes with a leather strap, width 23mm and stitched with white stitching. It has folding clasps with embossed Citizen logo, which is very easy and pleasant to use.

The backcover is also made of steel and has standard “Citizen Promaster Eco-Drive” mark with additional information about the watch.

The dial is certainly part of the watch that will not leave you indifferent. It is black, has a lot of print on it, and it is one of the feature-rich you can find in wristwatches. Despite many information it shows, it is incredibly readable, thanks to noticeable white hands, which is very important because this is a pilot’s watch. Despite the first impression you will soon realize that the dial is not so complex to understand how it could seem at first glance.

The inner pilot’s slide rule is located at the edge of the dial and it contains various markings and it very useful tool for various calculations and conversions. The inner ring rotates by turning the crown at 8 o’clock position. Using this scale, it is possible to operate a variety of navigational calculations such as the calculation of the plane’s speed, the average fuel consumption during the flight, and many others which are explained in detail in the manual of this watch.

Citizen Promaster Sky AS4020-28E 01

The inner part of the dial has three sub-dials, where the sub-dial at position ten o’clock is 24-hour indicator, at position “2h” is a subdial containing day of the week and 60-minute chronograph scale with additional views of the 20th part of a second. Hour markers are rectangular and polished with luminescent coating adding a luxurious look. Date indicator is at position “4h” with big window providing excellent readability. The hands are completely white, and hands for hours and minutes are coated with white luminescent coating which allows great readability.

Citizen Promaster Sky AS4020-28E Citizen has E670 mechanism from famous Eco-Drive series of mechanisms with solar power. Eco-Drive is a technology developed by Citizen and works as follows – under the dial there is a solar cell that converts incoming light into electrical energy and stores it in a secondary battery that powers the watch. Once fully loaded the watch can operate without recharging in the dark 6 months or a year if Power Save function is activated in order to save energy. The lifespan of a solar cell and secondary battery is at least 10 years, but it is estimated that it may last more than 20 years. Declared deviation of mechanism is +/-15 seconds per month, if it’s out of the reach of synchronization signals.

Citizen Promaster Sky Features

As you can see on subdial located at 6 o’clock position, this watch has the following features: chronograph, local time, alarm and perpetual calendar. A function that is not explicitly stated is radio control feature, which is also one of the most interesting, and which is activated in the standard mode marked as TME.

Radio Control function synchronize the clock with an atomic clock via radio waves that are emitted from the transmitter Majnflingen in Germany. The signals are broadcast 24 hours a day and the maximum range of the transmitter can be up to 2000km. According to the specification of this Citizen watch, it should have a smooth reception of signals within a radius of 900 km from the transmitter. Clock synchronization starts automatically every day at 3h and 4h in the morning, and you can also activate them as needed by pressing the lower button longer than two seconds, after which you will put the watch with 6 hours turned toward the northwest in order to ensure the best possible reception . To check the success of previous synchronization attempts, press the bottom button, after which the second hand will show whether the synchronization was successful and what the signal strength was in that time (L, M, H).

Functions changing is performed by pulling the crown to the first level and its turning. TME is the mark for standard time mode and manually time setting. Turning the crown to the right activates the chronograph function which values ​​are read in this subdial. It is started and stopped by pressing the top button, while pressing the lower button displays the time with accuracy of the 20-th of a second. Pressing the upper button longer than two seconds the chronograph is reset to zero position.

The function of L-TE, i.e. the local time, is very useful for those who travel a lot, and it is very easy to use. Pulling out the crown to the second level, the central second hand will indicate whether daylight saving time is turned on, which can be turned on or off by pressing the upper button. Turning the crown to the right the local time is moved for one hour forward and it moved backwards when the crown is turn to the left.

Citizen Promaster Sky AS4020-28E 03

The zero function represents checking the watch’s calibration, because if the clock has been exposed to strong magnetic field it is possible to have deviations from the reference position, which may cause the malfunction in displaying time, date and alarm. This way, the reference position is checked and possibly corrected if it’s need to be.

When you activate the alarm, the hands are automatically placed in the position of the currently set alarm time. Pressing the upper button activates or deactivates the alarm and by turning the crown a new alarm time is configured. Rotating the crown clockwise for one click hands are moved for one minute, and if we continually move the crown hands will start to slide while the crown is not turned in the opposite direction when they will stop again.

The Perpetual Calendar feature takes care of auto date correction without the need for manual adjustments. The owners of automatic watches will certainly appreciate this feature.


In conclusion, we can say that this is certainly one of the watches that offers a lot for spent money, and certainly represents a good purchase in its price range. Extremely quality case WR to 200m, excellent leather strap, solar mechanism with a plenty of useful functions, sapphire glass and a beautiful dial are enough reasons to take into serious consideration for purchasing this watch.

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