Variable Message Format


The Variable Message Format (VMF) capability is the most widely fitted Tactical Data Link (TDL) in the world, providing effective exchange of tactical data in both the ground and air military environments.


We are the market leaders for technical support to the development and implementation of VMF in the UK and the emerging VMF programmes in other nations.



Many of our ex-military operations personnel are highly experienced in VMF support.  For example, we developed and delivered concept papers for the use of VMF in support of UK and coalition operations to the MOD.
We are also participating in a number of other nations' programmes where we have delivered concept papers in accordance with their requirements.
Our VMF team authored the VMF documentation for the UK MOD, including:
  • Message implementation requirements specifications.
  • Header implementation requirements specifications.
  • Bearer definition documents.
As VMF is not yet a TDL subject to NATO configuration management, there is no related allied data publication that provides the interface operating procedures.  Therefore, we also authored the UK VMF System Management and Operating Procedures (SMOPs).  The SMOPs provide users with all the necessary information to enable correct operation of the VMF digital interface between Forward Air Controllers (FAC) on the ground and co-operating ground attack aircraft.  In addition, they include information to aid operation of the VMF interface with units / platforms of other coalition nations.

Message Standards

As it is not yet a TDL capability subject to NATO configuration management, the VMF message standard (MIL-STD-6017) is wholly maintained in the USA.  We have supported this on a formal basis, both through UK/US bilateral meetings and through the US configuration management forums - the VMF Sub-Group (VMFSG) and the Combat Net Radio (CNR) Working Group (CNRWG).  The UK, through the MOD Engineering Group, has observer status at these meetings and we have provided technical support to the working group at both meetings and represented them in their absence.
We take a pro-active approach to continued improvement of the VMF military standards and the ongoing development of VMF capability.  Essential to this role is the close working relationships that we have developed and continue to maintain with the large number of US platforms and system offices associated with the VMFSG and CNRWG.
Our SPIRIT process fully encompasses VMF capability.

Testing Support

Having developed the UK MOD VMF test strategy, together with the User Requirements Documents (URDs) and Systems Requirements Documents (SRDs) for test tools, we are able to assist Customers in all aspects of VMF testing.
Our capability includes the conduct of actual platform tests and we develop and apply VMF test cases.  We offer a full VMF test support service.


VMF operates with conventional UHF/HF/SATCOM radio communications where it is only necessary for integration of a CNR-compatible modem with the required radio equipment.  We can advise and support Customers as required.