Combined diesel-and-diesel, or CODAD, propulsion helps make Type 31 affordable to operate and gives it impressive range. The objection to the arrangement concerns its limits on power generation and speed, together with noise at higher output. Turbines are preferred on that last point in this comparison. Type 31 is nevertheless intended for a different job from the highest-end ASW frigates. Its machinery is not rafted to the same level, so the propulsion criticism has to be read against those more modest acoustic requirements.
Notable Point · 37:47-38:38
The Type 31's CODAD propulsion tradeoff
Combined diesel-and-diesel machinery supports range and affordability but limits power, speed, and quiet high-end ASW performance.