CAA issues its proposed way forward following the Mode S consultation


The CAA has issued a summary of responses to its consultation on Mode S carried out earlier in 2008.  In the light of these, the document also sets out how the Director Airspace Policy proposes to take mode S policy forward.  A copy of the document is available from the CAA website here.


There were a large number of responses to this consultation, many from the gliding community which would have been badly hit by the original proposals, both because of the practical problems on an aircraft with no electrical power and the operational problems that would arise for cross-country flying.  This was also a matter of particular concern to small and light aircraft owners because of the problem of fitting additional equipment and providing adequate power supplies.  The matter of costs was of concern to all.  The LAA argued against all the proposals on the basis of proportionality and practicality.  We wrote to the Department for Transport to argue that the consultation did not comply with regulatory requirements and we proposed alternative ways to achieve the CAA’s policy aims with much less impact on the VFR flyer.  Many LAA members also responded, an achievement with such a large and complex consultation. Their views gave considerable weight to our collective opposition.


The CAA has taken a broad and sensible view of the situation and proposed a way forward on each of its 4 policy proposals.  Whilst there is yet work to do to ensure there are no hidden problems in this, we propose to support Director Airspace Policy’s proposals.

In summary these are:

Mandate transponder carriage in all controlled airspace

This will now be limited to Class A to C airspace.  Any requirements for mode S carriage by VFR aircraft in Class D will be limited to specific problem areas and these would be the subject of individual consultation.  This is the alternative proposal put forward by the LAA.

Establish Transponder Mandatory Zones: 

Applications will now be dealt with through the existing Airspace Change Process. That is to say, there will be individual consultations.  Incidentally, we will shortly be meeting with NATS to discuss the consequences of TMZs to recreational aviation.  The LAA supported that proposal.

Extend transponder requirements to gliders: 

Specific arrangements will be made for gliders to operate above FL100.  Below FL100 the requirements will be as for powered aircraft.  This is a workable proposal subject to discussions between the CAA and BGA.

Mandate Mode S for all international flights: 

This will not be implemented and the CAA will discuss with other EU nations the way ahead on the difference to the ICAO recommendation.  This is in line with the LAA alternative proposal.


The CAA now proposes that Mode S will be required by 31 March 2012, but only for flight in airspace where Mode S is mandatory.  This will be in Class A to C airspace (which does not affect us) and possibly in TMZs, depending on the rules applied (which we will work on).  Otherwise, Mode A/C will continue until at least 2012 with a 2 year notice period of its demise in UK airspace. 


Overall, this is an excellent and balanced decision by the CAA and once again demonstrates the value of engaging with authorities on these matters, but at the same time, making a stand when appropriate.  The contributions made by LAA members were important to this success and our thanks go to everyone who responded.  We will now work to ensure that the implementation of these conclusions is done in a measured way, particularly in relation to international flight and transponder mandatory zones.  It remains our hope that Mode A/C transponders will continue in service until the ground interrogators are eventually switched off.