That is the official time-scale we are given;
"For several projects that have been recently launched by Turkey and are still underway including Original Light Utility Helicopter, ATAK Helicopter and Turkish Utility Helicopter, thrust systems are procured from foreign sources. The Turboshaft Engine Development Project (TEDP) aims to decrease this dependence on foreign sources while enabling domestic production of the engine systems, which constitute one of the most important components of these projects, and increasing the percentage of indigenous production in these projects. In this context,Turboshaft Engine Development Project has officially iniated on 07 February 2017.
The project will be carried out under the leadership of Undersecretariat for Defense Industries (UDI) Sub-Systems Department, under which design, development and testing infrastructure for as turbine engines will be generated in our country on one hand, and the 1400 shp original and national engine with the applicable type certificate will be developed by TEI in order to be integrated into the Original Helicopter, on the other hand.
Turboshaft Engine Development Project will be carried out for 8 years by a team of approximately 250 engineers all of whom are TEI employees serving at TEI's Engineering Offices in Eskisehir, Ankara and Istanbul.
Any future derivatives of the engine may be utilized to power the national platforms such as ATAK and HURKUS. Moreover; core technology of the engine will form the basis for the engine needed for "National Training/Fighter Aircraft - T/FX", and it will be possible to develop the national aircraft engine when needed, upon any necessary technological additions to the capabilities gained under Turboshaft Engine Development Project . "
https://www.tei.com.tr/detay/projects/turboshaft-engine-development-project
It took TEI 6 years to develop 'PD170' 170hp Aero Diesel Engine to production ready