LONDON—The U.K. defense ministry has signed a £150 million ($224 million) deal to further upgrade the Royal Air Force’s (RAF) fleet of Chinook helicopters, this time with a Digital Automatic Flight Control System (DAFCS).

The unannounced contract, signed back in December, builds on the defense ministry’s ongoing Project Julius that aims to bring the U.K.’s Chinook transport helicopter fleet to the same standard with new engines, and a new cockpit avionics suite based on Thales TopDeck system, eliminating the issues of having fleets within fleets, and allowing aircrews to fly any model of Chinook in service.

The introduction of DAFCS on 46 Mk. 4 and Mk. 5 Chinook models will replace the analogue system currently fitted and will help to standardize the fleet even further, particularly as the U.K. is currently taking delivery of 14 new-build CH-47 Chinook Mk. 6 helicopters from Boeing. The Mk. 6 aircraft is a sub-variant of the U.S. Army’s CH-47F and is fitted with the DAFCS system as standard.

The introduction of DAFCS greatly improves handling qualities and aircraft stability and increases the safety of the helicopters, particularly when flying in conditions when visual references were limited, such as over water, in dust or snow operations, defense officials have said previously.

In a statement to Aviation Week, the U.K. defense ministry said the work would be carried out in the U.K. at Vector Aerospace in Gosport and that installation on the first aircraft began "on time" earlier in January.

It is understood this will be the first program to retrofit DAFCS into the Chinook and that the process is quite "invasive" and also involves the installation of a second GPS/INS navigation system to provide redundancy. Installation of the system will take place as aircraft enter in-depth maintenance or conversion to the Project Julius standard.

Completion of the DAFCS installation program will be complete in the fourth quarter of 2018.

Meanwhile six of the new-build Mk. 6 helicopters have now been delivered to the U.K. and are being regularly flown by RAF crews as they prepare for the initial operational capability with the variant, expected before Easter. The remaining eight are due to arrive before Christmas 2015.