See and be seen �– the technologies & challenges�����������

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Greg Dunstone – ATC automation & Surveillance Engineer (retired)

Safeskies 2026 Conference : May 2026

Be seen electronically

• Safety improvement
• Situational awareness
• Automated safety alerts (ATC & pilots)
• Repel UAS (if UAS sense & avoid)

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• Efficiency improvement
• Less voice / More capacity
• Better procedures

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>>20 miles independent of weather

- Independent of aircraft size

Identity ,Velocity , Altitude

Automated aural alerts possible

“Sees” in All directions

Does NOT see the unequipped

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Limited range / Restricted window space

Dependent on aircraft size

Uncertainty of what is seen

Unknown velocity

Unknown height

Sees % of aircraft (equipped and not)

Human only

Electronic

receiver

Eyesight only

Airborne Observer

Electronic support

1. ATC Transponder

• Transmission on 1090Mhz
• Internationally standardized
• Seen by TCAS/ACAS – and ATC
• Approved for ATC separation within limited coverage volume
• ModeS provides identity

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The Technologies

Required Performance of technology depends on the

The application

The potential speeds involved (Closing speed)

The aircraft size & construction (Shielding)

The integrity required

The reliability required

The availability required

The interoperability required

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ATC transponder

2. ADS-B out

• Internationally standardized (1090Mhz)
• Mandated for IFR (and hopefully soon for all controlled airspace)
• Used for ATC separation
• Used by ADS-B IN products and applications
• Integrity monitored by RAIM technology ***
• Could repel UAS if UAS sense & avoid
• Is received by Space based ADS-B services

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*** An important support to detection of GPS errors & spoofing

ATC

ADS-B out (1090)

ADS-B out (1090)

3. EC Devices

• Used for situational awareness and airborne traffic alerting, and repel UAS
• Lower cost / Portable
• Reduced power 20w– only suitable for air-air
• UK considering only for aircraft < 140 kts
• Typically includes ADS-B IN receiver
• Weakness
• Typically no external antenna - shielding
• Integrity monitoring limited (step change?)
• Unable to be detected by current TCAS systems

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An EC transmitter

Dual band ADS-B IN

Wifi to tablet

4. UAT (Universal Access transceiver)

• Transmission on 978 Mhz 16w (USA )
• Internationally standardized
• Integrity monitored by RAIM like technology
• Only currently used in USA < FL180
• For aircraft interoperability one would need:
• Re-transmitter ground stations or
• All ADS-B IN is dual band

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Some risks & mitigations of ADS-B IN Display

• Head down
• Enable aural alerts, training
• Desensitisation to unequipped aircraft
• Get them equipped, training
• Potential of excessive clutter in busy areas
• Level filtering
• Blind spots due antenna shielding
• Appropriate equipment for airframe
• Reaction to false alerts / desensitisation
• AVPLAN/ OZRUNWAYS do NOT test the provided integrity bits in ownship or other ship GPS data

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Tablet apps

Ozrunways + AvTraffic app = Aural alert

Avplan = Aural alert to blutooth

Devices like

- Sentry or

- Skyecho

5. ACAS-X��The future ����EUROCAE�RTCA��ICAO: �Xa only so far

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NO products certified yet

6. FLARM

• Success in glider ecosystem

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• A proprietary ADS-B like system

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• No RAIM like integrity, non aviation spectrum

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• Interoperability HOW?

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• Could repel UAS if UAS sense & avoid received FLARM

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7. Remote ID (for UAS)

• Designed for law enforcement not ATM
• No RAIM like integrity, non aviation spectrum
• Limited power/range WiFi-Bluetooth for closing rate
• (UAS stationary vs 250kts aircraft =14.4seconds alert for aircraft at 1 nautical mile)
• Network variant– issues of 4G/5G coverage

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UAS Surveillance in Australia and Internationally �

• Is UAV sense & avoid adequate?
• Based on ADS-B : They can stop or descend – no human comfort issue
• USA philosophy tending towards UAS yield to manned – only manned with ADS-B OUT
• Which UAV flights need to transmit ?
• FAA have already mandated “no ADS-B on UAV” (1090 & UAT) unless interacting with ATC / flight plan
• UK NATS considering UAT for UAVs - and dual band receivers
4. If 1090Mhz used -concern about 1090Mhz capacity & 24 bit codes
• Formal 1090Mhz warning from ICAO : but Australian density is low today
• Australia has 65,535 codes / VH regos 17,576 / plenty for DoD & Recreational & UAV initially – but long term?
• Who is measuring 1090 MHz congestion in Australia? - when will we have a problem?

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Questions or Discussion