Does Your Aircraft Have Heated Windscreens?

If you have a heated windscreen that has an electric element across or around the screen, this may interfere with either or both of the GPS and the Iridium signals.

This problem causes position reports coming from the Spider to the Iridium satellite to be delayed, therefore not being sent in real-time. Heating by air is not a problem.

Why?

The higher an aircraft flies, the colder the temperature is. Aircraft operating in cold environments require specialised equipment to prevent ice from developing on critical components like the windshield. There are essentially two ways to prevent a frozen windshield in an aircraft. The older and less common method called bleed air involves blowing hot air onto the windshield. This method was extremely popular in the early days of jet aviation but has been overtaken by the more reliable and constant method of an electrically heated filament laid into the windshield.

While the electrically heated filament was a huge advance over bleed air for safety, it unfortunately brought with it another issue. The physical characteristics of an electrically heated windshield give rise to the Faraday cage effect which impedes any Radio Frequency (RF) device from transmitting or receiving through it. This is a function of grounded metallic circuitry and doesn’t necessarily require the heated windshields to be active to create problems. Since our Spider transmits RF to the Iridium satellites between 1616 and 1626.5 MHz, it also gets caught up in this effect. It’s important to note that this limitation is not specific to Spidertracks devices, you would experience the same difficulty with any similar device trying to transmit through a heated windshield.

The tracking works OK at times though!

The Spider X can store up 16 hours of data and will offload this when it is able to get a GPS lock where as older Spiders (models 1-8) can store up to 10 position reports. If it can not send out position reports due to the heating elements in the aircraft it will store them until the satellite signal strength is good enough to transmit. At this time it may be able to send all stored position reports.

On the website it will look like there are no delays if you are viewing the tracking after the flight, however, if you are viewing the flight in real time you will see no position reports come in for a short period, and then a large number come in at once.

I am already using a Spider with electrical heating elements.

You may already have the problems described above without noticing, or you may see gaps in your flights. What we would recommend is to contact [e-mail] and have us do some analysis of the transmission delays. We can tell you how well the Spider is performing in your aircraft and provide possible solutions going forward.

If you would like further information, you can contact us at [e-mail].

We will need the following information to be able to help you in a timely manner;

• Spider Serial number
• Aircraft it is assigned to
• Photo of installation
• Type of aircraft

Without this information supplied your support ticket will take longer to reply to.