Help streamline your 8.33 radio mod application
CAA publishes criteria for 8.33 radio funding


Below are a few notes from LAA Deputy Chief Engineer Jon Viner which are aimed at helping to streamline the process covering the change to 8.33 kHz-spaced radio fitment in LAA aircraft.  A MOD7 modification form MUST be accompany any radio change but the associated procedure is very simple, and there continues to be no fee payable to LAA for this activity. 


The deadline for 8.33 kHz radio fit is 31st December 2017.  While there is no difficulty in renewing Permits to Fly for aircraft currently with non-8.33 kHz radios, after that date the use of non-8.33 kHz radios is set to be illegal. However all ‘new builds’ must already be furnished with 8.33 kHz compliant radios as the deadline for the ‘Permit issue’ case passed some time ago.  Just for clarification, there is no problem with ‘non-radio’, if that’s an owner’s choice. 


Jon Viner says:

“With the end-of-the-year deadline for swapping out 25 kHz-spaced radios for 8.33 kHz-spaced radios looming, avionics applications on form MOD7 are flooding into the office.  Although they’re fairly straightforward for the engineers to review, unfortunately about half of these applications are having to be returned or queried for various reasons.  As the inspectors signing off the applications, you have the best opportunity to head-off most of these queries and to advise owners on the check flight aspect.  If you haven’t read LAA Technical Leaflet TL 3.03 recently, it might be a good idea to re-familiarise yourself with what’s involved: issue 13 was published in February. The latest version of the MOD7 form is issue 16.

Below are some areas where we’ve found problems with applications:

  • Check that all parts of the form are filled in correctly and you’ve signed in the right places (right-hand column and at the end).
  • Include all currently installed bits of kit including items that have previously been approved by the LAA on this aircraft, and not just the new bit of kit.
  • Include all the fuse/circuit breaker ratings for each of these items, and check they’re still appropriate.  We’ve had quite a few people swap out old radios with 10A circuit breakers with new Trig radios which only need a 5A circuit breaker, for instance.  In this case the circuit breaker should also be changed.
  • State the type and location of each antenna, including those previously fitted.  Stating ‘as previously fitted’ isn’t acceptable, as we can’t check that it matches our records.


On the check flights, please:

  • Test all the currently installed bits of kit and not just the new item (where the radio is being swapped, the transponder also needs to be checked as there might be interference issues, for example).
  • When testing a transponder, don’t forget to include the check on the altitude encoder, which may be integral to the transponder unit.
  • When testing the radio, ensure that it’s tested from a minimum distance of 20nm from the ground station and no more than 2000’ above it.  If testing from further away, the height can be greater: e.g. at 30nm not higher than 3000’, at 40nm not higher than 4000’, etc.

With your help we can smoothly transition the fleet to the new radios with minimal impact on the Engineering office.”



Steve Slater

CEO - 11th May 2017