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Retro Review: ASA CX-1 Flight Computer
02-06-2018, 03:40 AM
Post: #1
Retro Review: ASA CX-1 Flight Computer
Link to blog post:

[Image: IMG_20180204_063939307_HDR.jpg]


Quick Facts

Company: ASA (Aviation Supplies & Academics, Inc., )
Type: Aviation, Flight Calculator
Original Cost: unknown, but ASA’s current version, the CX-3 sells for $99.95, my guess would the CX-1 originally sold for that amount
Year that the CX-1 was produced: The late 1980s
Batters for the CX-1: 2 CR 2032 batteries (the CX-3 has 4 AAA batteries)

How I Acquired the CX-1

I picked up the CX-1 at a yard sale for $1. It needed new batteries, thankfully the battery compartment was still good. Replacing the batteries on the CX-1 required me to remove two plates on the back. Thank goodness for the small screwdriver sets.


The CX-1 (and subsequently the CX-2 and CX-3) is a unique type of calculator, which focuses on solving problems in aviation, as well as a timer, stopwatch, work with time (hours-minutes-seconds), and conversions. The keys are soft, so presses have to be deliberate.

Solvers: Aviation

The CX-1 had a vertical screen separated into two parts: the above portion has the calculator and the solver and its prompts. The CX-1 is an LCD calculator, hence the prompts for the solver were locked in place. When using one of the flight applications, whatever prompt you are working with flashes.

The bottom part of the screen contained all the solvers available. I wasn’t able to find a manual for the CX-1 online but was able to find one for the CX-2 and together with the help card that came with the calculator to determine which solvers were included.

Units used:

Temperature: Celsius (°C)
Speed: Knots
Distance: Nautical Miles (usually)
Volume: Gallons

Row 1 (from top to bottom):
Plan CAS Calculate true air speed (TAS) given outside temperature and calibrated speed (CAS)
Act CAS Calculate TAS given total temperature and CAS
Plan M# Calculate TAS given outside temperature and mach #
Act M# Calculate TAS given total temperature and mach #
Req CAS Calculate TAS and heading (direction) given wind and course speed conditions

Row 2:
Hdg/GS Calculate true heading given TAS, course, wind conditions
X/H-Wind Calculates head wind (head wind is negative (in your face), tail wind is positive (wind at your back)), and X-Wind (left wind is negative, right wind is positive)
Wind Unknown wind: calculates wind speed and direction given course direction and speed, TAS, and flight direction
G S Calculate GS given wind conditions and TAS
Req TAS Calculate heading TAS given wind conditions and GS

Row 3:
Leg Time Calculate time duration of a leg given distance and GS
Fuel Burn Calculate the amount of fuel consumed give fuel burn rate and time
FPH Calculate fuel rate (burned per hour)
Endur Calculate how long a flight can endure given fuel capacity and burn rate
Dst Fln Calculate distance flown given time and fuel burn rate

Row 4:
WT/Arm Weight – arms of an airplane (?)
%MAC Mean Aerodynamic Chord calculation
WT/Mom Weight - Momentum

Note CAS does not mean computer algebra system for the CX series.

In regards to direction, direction is measured in degree angles 0° to 360°, with respect to due north (I think), meaning at 90° wind goes west, 180° wind goes south, and 270° goes east.

Navigating the solvers takes a little bit getting used to, which is controlled by the arrow keys ( [ ← ], [ → ]). The left key also acts as down when you are at the first item in a row, while the right key also acts as up when you at the last time in a row. The solver that is being selected will have its prompt flashing.

Entering Hours-Minutes-Seconds

Use the [ T ] key after each component. For example to enter 23 minutes 28 seconds, press 0 [ T ], 23 [ T ], 28 [ T ].

Timer and Stopwatch

To activate the stopwatch, press the [TIMER] key. To stop the stop, press the [TIMER] again. Clear the stopwatch by pressing the [ C ] key.

For the timer, enter a time and press [CONV] [TIMER]. The CX-1 does not have a beep.


The CX-1 features a handful of conversions, all accessed by pressing the [CONV] key first.

Conversions available:

* Hours/Hours-Minutes-Seconds (HMS)
* Gallons/Liters
* Feet/Meters
* °F/°C
* Kilograms/Pounds
* Statue (regular) Miles (SM)/Nautical Miles (NM)
* Kilometers/Nautical Miles (NM)

The Updated CX-3

The current version, the CX-3 has a backlit, color screen, and can be flash updated. Added in the second version are density altitude and rhumb-line navigation calculations. Also the weight calculations have been streamlined. I think the square root function is also added.

Web page for the current CX-3:

Final Verdict

For a specialized calculator in aviation, the CX calculators (seemingly) fits the bill. The keys on the CX-1 are soft, but are easy to use. To the key is to pay attention to the prompts. The CX series either enhances or replace the flight computer slide rules. If you are into aviation or a profession, the CX is worth checking out.
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02-06-2018, 11:30 AM (This post was last modified: 02-06-2018 11:36 AM by Maximilian Hohmann.)
Post: #2
RE: Retro Review: ASA CX-1 Flight Computer

(02-06-2018 03:40 AM)Eddie W. Shore Wrote:  Original Cost: unknown

I bought mine in 1988 upon completion of my private pilot's license for something like 120DM (german mark) if I remember correctly. That would have been around 75$ using historic conversion factors.
Interestingly mine looks quite different. The plastic housing is black and the red stripes around the display are black as well. I have 3 or 4 of them in my collection now but never saw one like yours!

(02-06-2018 03:40 AM)Eddie W. Shore Wrote:  If you are into aviation or a profession, the CX is worth checking out.

Well.... maybe 30 years ago. I bought it back then because I had more exams to come (instrument rating, commercial license, transport category license) and thought it would be more useful than the circular slide rule we had to use for the private license. Only to find out that electronic calculators were forbidden in those exams (they still are in many countries to this day!). And for practical usage when I started flying commercialy in 1992 we already had PC software to do the flight planning and a spreadsheet, most probably Lotus 1-2-3, on a laptop computer for the mass and balance calculation "in the field". I have maybe two dozen navigation calculators in my collection but I never used one in or around an aeroplane for the real work. Sad but true. And today there are free mobile phone applications which can do all that and much more, including navigating you home.

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