<h4>The FLEX concept</h4>
<p>As the original donor vehicles are fitted with both 3rd rail and 25kV equipment, the FLEX units can become tri-mode trains with the ability to also incorporate hydrogen fuel cells.</p>
<p>Porterbrook’s pioneering FLEX concept involves converting the existing Class 319 units to Class 769 FLEX units. Two new powerpacks have been fitted – one under each driving vehicle. These low emission (Stage IIIB compliant) MAN engines are coupled to ABB alternators which in turn provide power to the existing DC bus, and the traction and auxiliary equipment.</p>