All PilotAware equipment has been developed to detect the most types of Electronic conspicuity possible. In Europe, this includes the following types of transmission.
These are:
These are known as bearingless targets as their radial GPS derived position is not transmitted:
The operating frequencies and the modulation techniques used differ between the older and the newer systems. Therefore, different methods of detection are required. Mode-C and Mode-S transponders are older technologies that do not provide a GPS location and therefore the situational awareness information provided is limited to height separation and a horizontal distance proportional to the power received and the rate of signal change. Consequently, the voice and audio alerts will be different between the old and the new systems. This section describes the various transmission, technologies how they are received, what information is available and how it is presented in audio and visual formats.
1.PilotAware (869.525MHz). Target with a Bearing
PilotAware uses a modern transmission technique that is automatic in that it requires no pilot or external input and is dependent in that it depends on data from the aircraft's GPS. The advantage, of PilotAware, continuously broadcasting its GPS location, is that it is easily detected and its unique position can be plotted on a screen. Additionally, an accurate voice alert can be given similar to that given by an air traffic controller. That is Bearing, Height Separation and Distance. Importantly with PilotAware, this information is provided continuously and with greater accuracy when plotted on a screen. (An Air Traffic Controller can only describe its bearing about the hours on a clock face. This is the position at the time detected with an error of up to +/- 30 degrees and very high latency†).
PilotAware devices use the larger of the two antennas to transmit and receive the PilotAware signals.
2. FLARM (868.4 MHz). Target with a Bearing
FLARM uses a modern transmission technique that is automatic in that it requires no pilot or external input and is dependent in that it depends on data from the aircraft's GPS. The advantage of FLARM continuously broadcasting its GPS location is that it is easily detected and its unique position can be plotted on a screen. Additionally, an accurate voice alert can be given similar to that given by an air traffic controller. That is Bearing, Height Separation and Distance. Importantly with FLARM, this information is provided continuously and with greater accuracy when plotted on a screen. (An Air Traffic Controller can only describe its bearing about the hours on a clock face. This is the position with an error of up to +/- 30 degrees and very high latency†).
PilotAware devices use the larger of the two antennas provided to receive FLARM signals when the host aircraft is in range of an ATOM GRID Ground Station or a SkyGRID relay. All in range ATOM GRID Ground Stations are shown on the PilotAware RADAR page.
⚠️IF NO ATOM GROUND STATION NOR SkyGRID EQUIPPED AIRCRAFT IS IN RANGE FLARM SIGNALS WILL NOT BE RECEIVED.⚠️
3. ADSB-Out (1090MHz) Targets with a Bearing
ADSB-Out uses a modern transmission technique that is automatic in that it requires no pilot or external input and is dependent in that it depends on data from the aircraft's GPS. The advantage of ADSB-Out automatically (continuously) broadcasting its GPS location is that it is easily detected and its unique position can be plotted on a screen. Additionally, an accurate voice alert can be given similar to that given by an air traffic controller. That is Bearing, Height Separation and Distance. Importantly with ADSB-Out, this information is provided continuously and with greater accuracy when plotted on a screen. (An Air Traffic Controller can only describe its bearing about the hours on a clock face. This is the true position with an error of up to +/- 30 degrees and very high latency†).
PilotAware devices use the smaller of the two antennas provided to receive ADSB-Out signals.
4. CAP1391 Devices (1090MHz)
CAP1391 is a UK Specification currently only legal in the UK and Australia. It has not been ratified as a World standard and cannot be used in Europe except as an ADSB (1090MHz) receiver.
CAP1391 specified equipment uses a modern transmission technique which is automatic in that it requires no pilot or external input and is dependent in that it depends on data from the aircraft's GPS. The advantage of ADSB-Out automatically (continuously) broadcasting its GPS location is that it is easily detected and its unique position can be plotted on a screen. Additionally, an accurate voice alert can be given similar to that given by an air traffic controller. That is Bearing, Height Separation and Distance. Importantly with ADSB-Out, this information is provided continuously and with greater accuracy when plotted on a screen. (An Air Traffic Controller can only describe its bearing about the hours on a clock face. This is the true position with an error of up to +/- 30 degrees and very high latency†).
† Note unless an Air Traffic Controller has access to Primary and Secondary RADAR then the position that he/she is relaying to you will have probably been given by a Pilot’s reported visual position at a VRP or other visual landmark. This is a very inaccurate, first fix position compared with a GPS position, so this will also compound the inaccuracy inherent in the clock face positioning method used by ATC.
5. Mode-A (1090MHz) Bearingless Target
Mode A is the simplest and oldest transmission available and has its genesis in the 1940s, providing only a 4-digit squawk code. As this transmission, does not contain any useful information on height separation or position the data cannot be used in an effective in-cockpit situational awareness tool. Therefore, Mode-A transmissions are NOT reported by PilotAware, however, the squawk code is recorded in the traffic page when associated with Mode-C/S transmissions.
6. Mode-C (1090MHz) Bearing-less Target
It is important to understand that Mode-C devices only transmit when interrogated by a ground radar signal or a commercial aircraft TCAS System. Therefore, if an aircraft is NOT being interrogated it will NOT transmit a signal. A lack of interrogation can happen at low levels and/or in remote areas.
Mode-C transponders are similar to Mode-A but are equipped with an onboard altitude, (QNE Height relative to 1013.2mB) encoder that is used to calculate the vertical separation between the host and the target aircraft. Therefore, the horizontal distance of the target aircraft from the host aircraft can only be estimated from the signal strength and the rate of change of the signal strength received. This is explained further in the section on Mode-S transmissions below.
When a Mode-C transmission is detected by PilotAware and compared with a group of pre-set height filters and strengths (selectable by the user on the PilotAware CONFIGURATION page) it will trigger a voice alert, direct from the PilotAware audio output, and also send a message to your chosen navigation software package. The absence of a GPS coordinate means that a directly detected Mode-C target cannot be plotted on a screen, as it can with a target with a GPS location. However, its vertical separation from the host aircraft and its approximate distance will be shown.
⚠️IMPORTANT THE BEARING OF A MODE-C TARGET CAN NOT BE SHOWN ON A SCREEN⚠️
PilotAware uses the smaller of the two antennas provided to receive Mode-C signals.
7. Mode-S (1090 MHz) Bearingless Target
Similar to Mode-C, Mode-S transponders are devices that transmit (at 1090MHz) only when interrogated by a ground radar signal or a commercial aircraft TCAS System. Therefore, if an aircraft is not being interrogated it will not transmit a signal. This can happen at low levels and/or in remote areas.
Mode-S is an onward development of Mode-C which transmits more information. The most significant of which, for electronic conspicuity, is the unique airframe ICAO number.
PilotAware detects this 6 digit ICAO code which allows it to uniquely identify the target aircraft. The signal from an approaching Mode-S (or Mode-C) transponder will increase non-linearly as it gets closer to and diminish non-linearly as it retreats from your aircraft. The absolute signal strength, at any particular distance, is not consistent for all installations so detection can only work with relative changes in signal strength. This is shown in the following illustration.
When a Mode-S transmission, with a unique ICAO code, is detected its barometric height separation and received signal strength, are compared with a group of pre-set heights and signal strengths. These are pre-selected by the user via the PilotAware CONFIGURATION page. The detection will trigger a voice alert sent from the PilotAware audio output and also send a message to the chosen navigation software package. The absence of a GPS coordinate means that a directly detected Mode-S target cannot be plotted on a screen as is a target with a bearing, however, its vertical separation from the host aircraft and its approximate distance will be shown.
For example, on EasyVFR and the PilotAware RADAR screen, this will be shown as a colour coded banner in the top right-hand corner showing the aircraft registration and relative height. The colour of the banner will change from Green, Yellow to Red as the detected Mode-S signal increases through the pre-set range.
On SkyDemon, with 'Show Bearingless Targets' selected, this will be shown as a series of rings around the host aircraft. The colour of the rings will change from Green, Yellow to Red as the detected Mode-S signal strength increases through the pre-set range. Please note the size of the ring does NOT indicate distance but that the signal threshold has been reached.
⚠️(IMPORTANT THE BEARING OF A STANDARD MODE-S TARGET CAN NOT BE SHOWN ON A SCREEN)⚠️
PilotAware uses the smaller of the two antennas provided to receive Mode-S signals.
In addition to the voice command from the PilotAware unit, a visual alert of Mode C/S including the relative height will appear on your Tablet as defined by your navigation software supplier. On SkyDemon this will be by a series of rings around your aircraft whose colour changes through Green, Amber and Red as the signal strength increases. On EasyVFR this is done by the appearance of a banner alerting the user to the danger and its status. The display of Mode-C/S alerts in other navigation systems will vary. How this is shown on the navigational tablet is not determined by PilotAware but by the navigational software manufacturer.
You must be clear in your mind that a Mode-C/S signal will not give you an accurate horizontal separation only a vertical one. You will be informed of the relative height compared to your aircraft but not the distance or bearing. Therefore, effective action can only be taken as a result of your visual observation, supported by prompts from PilotAware. The relative vertical separation will help in this regard as it dictates whether you need to look for the target above, below or at a similar altitude to your own.
⚠️It is important that you continue to undertake a 360-degree scan as a bearing of the target is not given. ⚠️
PilotAware allows you to set vertical separation triggers, relative to your aircraft, for the Mode-C/S alerts. This is done by logging onto your PilotAware WiFi hotspot and typing in 192.168.1.1 and selecting from the Options Menu. Select Mode-C/S Separation.
This will give you the following options +/- 500 ft. +/-1000ft +/- 2000ft +/- 4000ft +/- 50000ft.
Choosing a +/-50,000-ft separation will include a large amount of target data and should only be used for testing purposes as you will get an overlay of voice alerts from high flying aircraft. Similarly, selecting +/-500ft will minimize the number of alerts but will only warn you of Mode C/ S transmitting aircraft within +/-500ft separation from your aircraft. The other settings will give an increasing number of alerts from a greater separation range. It is for you to decide the separation range with which you are comfortable when flying. It is suggested that one starts with +/- 2000ft.
Choose which is best for you by experimentation or better still discuss this with more experienced pilots or your club CFI. So that you don't get inundated with less useful information, it may be best to choose a closer separation and a lower sensitivity as described below until you are familiar with the information given by PilotAware.
All vertical data, whether derived from GPS (GNSS) altitude data or barograph data, is converted to GNE Altitude (reference 1013.3Mb). The originating barograph data will be quantised to 100ft increments for older transponders and 25ft only for the latest transponders. This should be taken into consideration as there may be a combined 200ft reporting error in the separation of Mode C/S derived targets.
In addition to vertical separation, PilotAware allows you to set your preferred Mode-S horizontal detection range which varies the sensitivity of the Mode S Alerts to match the environment in which you will be flying. This is done by logging onto your PilotAware WIFI hotspot and typing in 192.168.1.1 and selecting Configure from the Options Menu. Select Mode-C/S Detect. The following options are available
Ultra-Short Range
This will give you the lowest sensitivity and is intended to minimize alerts when operating in high Mode S strength environments such as being adjacent to or when transiting through the overhead of major airports.
Short Range
This is also a low alert setting for GA use in busier environments.
Medium Range
This is the default. This sets a higher alert for initial General Aviation use.
Long Range
This is an extremely high sensitivity range intended to allow maximum alerts for test purposes only. It is recommended that this is not used in normal use as you will receive too many voice alerts from high flying Jets with high power transponders.
If you are receiving too many bearingless target voice alerts it is suggested that you reduce the horizontal detection range accordingly.