UK private aircraft avionic equipment requirements

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Regulations are coming into force which require UK private aircraft to have improved radios, transponders and other equipment over the coming years. This is a summary of the key dates and capabilities for UK registered aircraft weighing less than 2 tonnes.


Most (but not all) aircraft have a Mode C transponder that transmits a 4 digit squawk code and pressure altitude, allowing them to be seen and plotted by Air Traffic Control. Regions/areas marked as “Transponder Mandatory Zones” and Class D airspace normally require an operational and active Mode C transponder to fly there. In some cases, Air Traffic Control may allow you to enter without one, but this can’t be guaranteed.

Mode S Transponders transmit additional information such as the aircraft identity, direction, speed etc. which help both ATC to know who you are and allow other aircraft to view your position. More technical details can be found on the Eurocontrol Mode S project pages.

It is a legal requirement to operate your transponder if one is fitted, unless instructed by ATC not to do so. Avoid the trap of not switching to ALT mode by mistake, which results in not transmitting your altitude.

The CAA’s policy on adoption of Mode S can be found here and is well summarised on the  LAA webpage on the topic.

While, Mode S equipment must be fitted to any new aircraft, there is as yet no cut-off date requiring the GA fleet to upgrade from Mode A or C unless undertaking any one of the following activities:

  • Any public transport flight
  • Flying above FL100
  • Flying IFR or VFR in Class A, B or C
  • Flying IFR in Class D or E
  • crossing a TMZ (Transponder Mandatory Zone) unless with specific ATC clearance

A more advanced use of transponders is ADS-B, which broadcasts information at the same 1090MHz frequency about once a second independently of any radar signals detected. The broadcast includes position information (typically based on GPS), speed, direction and other parameters.

In the US only, an alternative frequency can be used for GA aircraft below 10,000 feet (known as UAT). There is a national footprint of ground transmitters which provide weather and other useful information including other traffic. A trial of this is planned in Southern England for 1H 2018. There are several commercial portable ADS-B receivers which work with popular tablet flight apps, including low cost Pilotaware and Stratux.

Otherwise, GA pilots see relatively little benefit from Mode S compared to Mode C. It does allow ATC to identify and talk directly to aircraft who may be on a listening squawk, or not yet have made contact with.

Mode S is now mandatory if you want to fly in certain parts of Holland.

ADS-B is only mandatory in very few specific zones in Europe, such as helicopters operating in the North Sea offshore Holland.

See also Eurocontrol’s statement on Mode S equipment

8.33kHz Radios

A technical change has been introduced throughout Europe to increase the number of radio channels available by reducing the channel spacing from 25 to 8.33 kHz.

All radio-equipped private aircraft flying within Europe today should be fitted with at least one 8.33kHz radio since 1 January 2018. This formal statement from EASA confirms that only one radio needs to be 8.33 compliant (assuming single engine less than 2700kg). Groundstations converted during 2018, with a few exemptions. 25kHz spacing has been retained for certain cases, such as 121.5 for emergencies.

While you may find that receiving ATIS and monitoring other channels operates adequately  using an older 25kHz radio, it is illegal to transmit using 25kHz on any 8.33kHz designated channel.

This has been coming for some time. In 1999, flights above FL245 and from March 2007, the CAA mandated that flights above FL195 had to be equipped with 8.33kHz. New aircraft had to have them from November 2013 and all IFR airways flights from January 2014. The underlying EU legislation can be found here.

This discussion on the LAA forum gives both sides of the case from several Permit aircraft owners about the change.

ELTs (Emergency Location Transmitters)

An ELT fitted to an aircraft will be activated in the event of a crash and send an alert to the rescue services which includes your GPS position. They can also continue to report your position and allow Search and Rescue helicopters to home in on your position. Alternatively, portable units that do exactly the same thing (for a lot less), called PLB (Personal Location Beacons) may be used. The tradeoff is whether you think an ELT will be useful at the bottom of the sea or lake, versus the chance of being unconscious and unable to active your PLB manually.

The frequency for ELTs and PLBs changed some years ago, and now combined 406MHz/121.5MHz are common. Those with built in GPS receivers are the best. From 25th August 2016, EASA Part-NCO harmonised the requirement throughout Europe. All EASA aircraft must have an ELT, but a PLB can be used instead for aircraft with six seats or less. This is true even for the shortest flights that only remain in the circuit.

The UK CAA has clarified that Permit aircraft (so-called Annex II) are exempted from this ELT/PLB requirement for private flights.


Various countries have regulations requiring oxygen to be available for use by flight crews. EASA regulations specify:

  • when above 10,000 feet for more than 30 minutes or
  • whenever above 13,000 feet.

It makes no difference whether flying VFR or IFR.

This can be provided using uncertified portable oxygen equipment, using cannulas up to 18,000 feet and full masks when above that. Peter (who runs the forum) provides much more detail and photos on his  website.

Hand Held Fire Extinguisher

EASA Part-NCO (specifically NCO.IDE.A.160) also removes the requirement to carry a hand-held Fire Extinguisher onboard private aircraft of 1200kg or less. You’ll still need to carry a medical kit though.

Have I got it wrong or incomplete?

This is a complex and changing area of regulation. Please do your own research and if you find or know of any errors/omissions in this article, feel free to comment below so I can put it right.


  1. There’s no requirement for a transponder in class D if VFR, certainly not in the UK at least, excepting that you must use one if fitted.

    1. You are quite correct. I’ve clarified the text slightly by stating that it is normally required and subject to ATC approval.

  2. If a transponder is, in fact, fitted, is there a “mandatory” inspection requirement for said transponder? And if so, where can details be found?

    1. Certified aircraft in the UK would typically have their own approved maintenance schedule (AMP), based on Part-ML. The UK CAA published an Airworthiness Code (CAP2400S) which tries to explain the minefield of maintenance regulations, but they are still quite complex to understand. It is common for transponders to be tested every two years, and this is usually done during Annual maintenance along with other avionics. The specific tests can be found in EASA SIB 2011-15. Hope this answers your question.

      1. Many thanks for your reply David! I did attempt a wade through CAP24005, googled a number of other CAA pubs and asked a couple of maintenance organisations before posting, but got different answers. Unlike US FAA regulation 14 CFR 91.413 (a) which is very clear, I couldn’t find a CAA equivalent and even EASA SIB 2011-15 is recommended only. A 24 month check may be good practice, but whether scheduled or not in the AMP appears to be up to the individual owner/operator or maintenance organisation and, unless I’ve missed something, is not mandatory in BREXIT UK!

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