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Hawarden Airport Frequency Monitoring Code Proposal.

Hawarden Airport is situated in Class G airspace and provides Air Traffic Services (ATS) to a variety aircraft both inside and outside of Controlled Airspace.

The surrounding Controlled Airspace, terrain and gliding sites create a ‘funnelling effect’ whereby aircraft are forced to fly across Hawarden’s approach and climb-out lanes conflicting with arriving and departing aircraft.  To mitigate this risk, Hawarden Airport has applied for a Radio Mandatory Zone (RMZ).  A recommendation from the consultation process for the RMZ was for the use of a SSR code as a ‘listening out squawk’.  Hawarden ATC are of the opinion that SSR code ‘4607’ should be the dedicated squawk for this procedure and would be published with associated procedures.  If this procedure was to be adopted, any aircraft wishing to transit the Hawarden RMZ would be able to operate in the airspace without the need for unnecessary two-way radio communication. 

The selection of ‘4607’ by a pilot would inform ATC that the pilot is monitoring the frequency and when required, co-ordination can be requested to deconflict against IFR traffic.  This should reduce the impact of the RMZ on the local GA community.


The Air Traffic Services Unit (ATSU) at Hawarden Airport currently provides services to aircraft in both Controlled and Uncontrolled airspace. ATS are provided to all aircraft, both operating at Hawarden Airport and aircraft transiting the area, in accordance with UK FIS.  The ‘funnelling effect’ as described above, together with the diversity and nature of aircraft operations in uncontrolled airspace, has led to conflicts between aircraft.  This is likely to occur more frequently with known traffic levels and projected increase in levels forecast.

As Hawarden Airport is situated in Class G, the current requirement for a pilot transiting the area is to avoid the ATZ and use the ‘see and avoid principle’.  This can have a major impact on aircraft inbound to Hawarden Airport receiving an ATS, resulting in significant delays for their approach requiring the aircraft to be given an extended routing until the conflicting aircraft is clear of the approach. If the confliction occurs when the inbound aircraft to Hawarden Airport is on final approach, ATC could instruct the aircraft to break off the approach against the unknown traffic.  Departures are held on the ground until the conflicting aircraft has vacated the climb out lane resulting in delays.

In order to comply with its responsibilities for Safety Management of the ATS and to enhance flight safety in the vicinity of Hawarden Airport, Serco (on behalf of Airbus Operations Ltd) are currently in the process of an Airspace Change Proposal to establish an RMZ.

During the RMZ consultation process various issues were raised, amongst which was, a reluctance from the GA community to contact an RTF frequency, as this would increase their workload and also potentially increasing controller workload due to the extra loading of RTF calls.  The introduction of a ‘listening out squawk’ would both appease the GA community and alleviate the potential issue of controller workload.

Another issue raised was the increased workload of pilots leaving the Liverpool Control Zone southbound, who would be required to immediately contact Hawarden ATC due to the RMZ.  The ‘listening out squawk’ would alleviate this problem and will form part of the ‘Letter of Agreement’ between Hawarden and Liverpool Airports.

Local pilots should already be familiar with the ‘listening out squawk’ procedure, as nearby airports Manchester and Warton have adopted this procedure.

Airspace & Services

The airspace around Hawarden is complicated and contains, amongst other features, the following:

  • Hawarden ATZ;
  • Liverpool Control Area and Liverpool Control Zone;
  • Manchester Control Area and Manchester Control Zone;
  • Manchester Low Level Route;
  • Restricted Area R311;
  • N864 Airway - Base at various levels;
  • High terrain situated beneath Controlled Airspace;
  • Various gliding sites;
  • Minor airfield strips.

Anticipated Use

Historically, Frequency Monitoring Codes have played a critical role in reducing infringements of controlled airspace by enabling ATCOs to alert pilots if they look likely to infringe.  Any aircraft fitted with a Mode A/C or Mode S transponder can use these codes.  By entering the relevant 4 digit code into the transponder a pilot signifies to ATC that they are actively monitoring the radio transmissions on that frequency.

The proposal of Hawarden is somewhat different.  Rather than acting as a tool to provide early notice of potential controlled airspace infringements, Hawarden intend to use the code for aircraft transiting in the vicinity of Hawarden to identify to the ATCO that they are on frequency, do not require a service, but are contactable by R/T should coordination or information about their flight be required.

The proposed RMZ is situated outside of Controlled Airspace and is illustrated with waypoints below.

Hawarden has reviewed the use of its own SSR code allocation, which is as follows:

4601                   Hawarden Conspicuity
4602 – 4607        Hawarden Radar

Having considered how best to manage its allocation in the future, Hawarden is proposing that code 4607 would be used as a Frequency Monitoring Code.  If approved by the CAA, this would be designated in the UK code allocation plan as both unverified and unvalidated.

In the selection of code 4607, pilots would indicate they are monitoring Hawarden Radar on 123.350MHz but do not require a service.  Importantly, there is no obligation on Hawarden ATC to provide any form of monitoring or information of any kind.  Pilots requiring a service should call Hawarden Radar in the normal manner.


The Frequency Monitoring SSR Code was suggested by a number of stakeholders during the Hawarden RMZ consultation process and, in analysing this further, was seen as an enhancement to safety for the following reasons:

  • SSR with Mode C provides enhanced information to ATC;
  • More readily detectable to radar;
  • Pilots able to be contacted by ATC, which improves coordination;
  • Early warning of controlled airspace infringement (N864 and Liverpool CTA/CTR);
  • Adjacent units able to monitor traffic;
  • Reduces R/T loading, particularly when pilots do not require a service.


It is proposed that Hawarden Airport utilises of a Frequency Monitoring SSR Code, subject to the approval of the Airspace Change Proposal for the Hawarden RMZ being successful.

We would appreciate any comments you have both positive and negative on the proposal by the 31st October 2016.

Yours faithfully
Mark Spedding
Senior Air Traffic Control Officer

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