Not so much water has gone by in the rivers since the Aircotec Company managed to make a very small, handy and effective digital machine with the indicative name of Alibi. The Manufacturer intended this to mean the pilot's provable alibi. To this day these instruments are to be seen and mainly heard on Czech hills. Maybe the only fault in the beauty of this instrument of unusual shape was the deviation of zero, following two years of use, to somewhere from +0.2 to +0.3m/s and because the instrument didn't contain any correctional elements, all that remained was to move the acoustic threshold setting above this value and keep flying with this little error.

    Pilots who are used to keeping their eyes glued to the data, were somewhat bothered by the absence of the needle or at least column indicator of the variometer. Numbers, changing rapidly before their eyes drove them into a mild fury. On the other hand, pilots who fly by smell and sound were absolutely satisfied.

Charging and Power Consumption
    A classic 9-volt battery powers the instrument. The power use during operation is a mere 3.8mA, which means about 30 hours of operation when using a re-chargeable NiCd battery with a capacity of 110mAh. If, however, we use an alkaline battery, we can count on roughly 70 to 80 hours of operation. And a pleasant surprise for electronics fans - the instrument not only does not have a manual on/off switch but following switch off with the electronic switch, the instrument uses no more power whatsoever. And if so, it is of a value less than 0.00005mA, which for one this is pretty difficult to measure, but mainly there's no practical reason to measure it.

Variometer
    The variometer displays the ascendant or descendant value via a two decimal place number augmented by an arrow pointing up or down, with a precision of 0.1m/s. Positive ascendant values are accompanied by sound signals.

Acoustics
    The acoustics are resolved with a continuous or interrupted tone, whose pitch changes dependent upon the size of the value of ascent, with the interruption in proportion to speed. Change near zero is very progressively set, so that with Alibi you can turn "total shit" with a certain enjoyment, that is, at least audible. A slight quirk is the constant tone height within one beep. If we climb ever faster, the pitch of the tone of each successive beep is moved upwards, but during the actual peep, it does not change. Another reason to be infuriated for pilots with absolute musical hearing. Today's modern instruments change the pitch of the tone even during the beep itself, which creates the impression of a tonal slide. Of course, no slide can compare to the beautiful music of the Alibi.

Altimeter
    The altimeter in this instrument is double. One for measuring absolute altitudes, by rights above sea level, and the second for measuring relative altitudes, related to the elevation of landing or take off (compensation height). Both altimeters work with a precision of 1m. The maximum altitude displayed is 9,143m.

Time Measurement
    The instrument does not contain a Real-time clock, and therefore it is not possible to determine neither the correct date nor the exact time. The only time function is the stopwatch, which, with an accuracy of 1 second measures the time from its startup, that is generally the flight duration from the moment of start.


Instrument Memory
    The Alibi's memory is cleverly divided into three cache's. The first of these holds data about the most recent flight made - duration, maximum climb, maximum altitude reached. The second memory cache saves the same data, but selects the maximum values from among all flights made from the last reset of the instrument. This zero reset of values is useful to do at the start of the year, or season. So in this memory cache we can find, whenever, the duration of our longest flight, maximum climb we've met with from the beginning of the year, and the maximum altitude we reached that year. The third memory cache shows us the number of flights made and a sum of the durations - total flying hours. It is then possible to immediately calculate another piece of information - the average duration of each flight. So simple and useful ...


Shake Before Use ?
    If you've just found in your basement, in a pile of rusty junk the Aircotec instrument called, "Alibi", don't throw it out or sell it. If it is broken, have it repaired. Even an off balance zero can be repaired. With an alkaline battery it is possible to carry it around with you without worries about maintenance and at the right moment, pulled from the bottom of a backpack it will provide a priceless service. Its compact and impact resistant case will be valued, especially by beginners in their wild cartwheels.

    No, really, I don't sell these instruments for a living, as may seem from the above lines. Only with love and even a little nostalgia, I remember back to the times when I flew with this reliable successful instrument. Or perhaps it wasn't in the instrument ...?

    Because we found that a surprising percentage of pilots own the Alibi, and that most of them bought this instrument second hand, and as is usually the case, without documentation or an instruction manual, we've added instructions on how to use this successful instrument to take full advantage of its capabilities. For clarity, we will refer to the round control buttons with numbers 1-5 , exactly as shown on the drawing and as they are referred to in the original english instructions.

Turning The Instrument On and Off
    The instrument is switched on with a short pressing of button 1 and the serial number of the instrument will appear on the display, along with battery status in volts. If you don't want to see this information, push the 1 button again immediately after start up. To turn off the instrument hold down button 1 for about 3 seconds, or else the instrument automatically shuts off after 15 minutes of inactivity, and in Balloon Mode it shuts off after 120 min. The manufacturer recommends waiting at least 3 seconds following shut down of the instrument before turning it on again. If the battery charge shown is close to 6.5V, the accuracy of readings is no longer reliable.

Operational Modes
    It is possible to switch the instrument into one of the three following modes by holding down, simultaneously, buttons 2 & 4 for five seconds - gliding, parachuting, balloon flying - a short simultaneous holding down of the buttons and the current mode set is displayed, by means of symbols, with the exception of Glide Mode, which is without a symbol. The acoustic signals are then, in the various modes, based on various states, for example the ascent of the balloon or the correct altitude for tossing the parachute.

Selecting Units For Measured Quantities
    By simultaneously pushing buttons 2 & 3 it is possible to choose between feet and meters. A short push on button 3 gives you a choice of displaying absolute altitude, relative altitude (gain or loss/compensation height) , over height or atmospheric pressure.

Altitude Displaying
    By a short press of button 3 it is possible to call up absolutely altitude, relative altitude or atmospheric pressure.

Altitude Setting
    Following the selection of type of altitude display by a short, repeated push of button 3, it is possible, following a short repeated push of button 2 to change the value of the blinking number with the aid of button 4. A record of the change is then made by a short push of button 3. But beware, all three numbers are tied together, so for example, a change in atmospheric pressure brings about a change information on over height.

Immediate Zero
    By a short press of button 4 it is possible to call up a very useful finction, whose most accurate name is apparently "immediate zero". This function temporarily, immediately, changes all figures to zero, without affecting other data, such as altitude, absolute or over altitude. A repeated pressing of button 4 returns everything to the normal display functions. Immediate Zero is useful when flying around without a goal, or cirlcling in a turbulent area, in which the pilot has doubts as to whether he's losing or gaining altitude. Following the Immedate Zero selection, all that's needed is to cirlce for a moment and then check the data about altitude. If it is negative, there's no sense in remaining in the area any longer.

Acoustics of the Instrument
    The instrument is capable of emmitting two types of acoustic signal - interrupted and continuous. It is possible to set the volume of both, while the increase in battery power consumption at higher volumes is negligible. With a short press of button 5, just once, it is possible, by listening, to discern what type of acoustic signal is currently set on the instrument. If you hear only one short tone, this means the acoustics are turned off at the moment. A double pressing of button 5 in quick succession, within an interval of 1s, enables swithching of the volume level, or if desired, turn the acoustic signal off altogether. A series of four presses of button 5 a continuous or interrupted tone can be set. For thermic flying, the interrupted tone is ideal as it allows for unusually sensitive discernment of slight changes during even very minute ascent - especially if we set the threshold just above zero, for example at a value of +0.1m/s.

The Threshold of Acoustic Setting and Descent Warning Alarm
    The point of acoustic setting can be moved anywhere in a range from -2m/s to 0.5m/s, while the threshold for the descent warning signal, or Sink Alarm, is possible to place between -1m/s to -6m/s. Setting is achieved by a longer pressing of button 2 - three seconds - and at the moment of flashing data on the variometer it is possible with the aid of button 4 to change the set value threshold acoustic settings. With another short push of button 2 the threshold of the descent alarm can be changed. A record of the set values can be made with button 3.

Temperature Display
    Pushing button 3 for about three seconds calls up the temperature display, which dissappears after a few seconds.

Stopwatch
    The first short push on button 1 is the zero reset of the stopwatch, set to ready and the digital display blinks. Another push on the same button starts the stopwatch. When a time of one hour is reached, the time displayed turns to hours & minutes. A third push on the same button stops the stopwatch and it is possible to read the time. If the stopwatch runs for more than 2 minutes, data is saved to memory, as if it were a flight made.

Memory
    Immediately following the simultaneous pressing of buttons 3 & 4 the instrument switches to Recall Mode, and the display shows the contents of memory cache #1, that is the data of the most recent flight, which is the maximum height attained, maximum climb, and duration of the flight. Following a short push on button 3 the number of flights and total duration is displayed, that is, flying hours.

Clearing the Memory
    After going into the Recall Mode, a simultaneous poush of buttons 3 & 4 and a push on button 3 for 30 seconds, the data in memory is erased. This operation is good to perform at the start of the season.

Eventual, Inexplicable Problems
    The manufacturer recommends, in a case of "strange behavior" of the instrument to take out the batteries for a short time, like 1 minute, put them back into place, and after swithching the instrument on, check their status. From my personal experience I can say that I've never had this kind of experience over two years of using the instrument.

Closing Remark
    Don't believe the pompus talkers that the Alibi is a child's toy and that a good pilot flies several machines with a total cost of over 40,000. My first 100km I flew with this handy instrument.


    The SkyFly server editorial staff wish you many happy flights and top sport achievements while flying with the Alibi.