Rolls Royce MTU engines selected for the Type 31 frigate

Babcock announced this week that MTU has been selected to supply the main engines and generator sets for the Type 31 frigate.

MTU is a German company headquartered in Friedrichshafen, employing more than 10,000 people but is a subsidiary of British-owned Rolls Royce Holdings Plc. They are a world leader in marine diesel manufacture and the RN’s engine supplier of choice. The decision to select MTU engines for Type 31 is no great surprise. The Danish Navy’s Iver-Huitfield class frigates that form the basis of the frigate’s design have near-identical 20V 8000 M70 engines.

MTU 20V 8000 M71 engine are the most powerful high-speed diesel engines available and can deliver up to 12,200 bhp (9,100 kW) of continuous power.

Four replacement 12-cylinder 4000 M53B diesel generator sets are being installed on each of the Type 23 frigates during the Power Generation Machinery Upgrade (PGMU) programme.  The Type 26 frigate will be fitted with four 20-cylinder MTU 4000 M53B diesel generator sets. Three MTU Series 4000 DG sets will be installed on each of the Type 45 destroyers undergoing the Power Improvement Project. The Astute class submarines have two DGs which provide back up power to the nuclear reactor. They have been upgraded from the old MTU 8-cylinder 396 engines to 12-cylinder MTU 4000s. Such commonality across the fleet reduces costs by simplifying training and logistic support.


In total, Babcock’s Type 31 order comprises 20 engines and 20 generator sets, the MTU Callosum propulsion control and monitoring system, and Integrated Logistics Support (ILS). Each frigate will be propelled by four MTU 20-cylinder 8000 M71 engines. Electrical power will be provided on each vessel by four MTU generator sets based on 16-cylinder 2000 M41B units, each delivering in excess of 900 kW. The first shipset from MTU is scheduled for delivery to new frigate factory in Rosyth for insertion into hull 1 during September 2021.

The 8000 M700 diesels side-by-side in one of the two engine rooms of the Danish frigate, Iver Huitfeldt.

The Iver Huitfeldt parent design has simple, robust CODAD propulsion. The four diesels can be clutched in to drive the ship in different configurations. A single-engine can propel the ship at 18 knots with an exceptional range of about 9,300nm. Two diesels can make about 25 knots and using all four engines the ship can reach 29.3 knots in less than 120 seconds.

The placing of this contract will doubtless spark further debate about British taxpayers’ money being spent overseas. The Type 31 project is partly inspired by its economic benefits and the amount of UK content will be closely scrutinised. Despite recently heightened concern about reliance on overseas suppliers, any complex UK defence project will include an international supply chain. In this case, MTU offers the best quality solution, is inherent in the existing parent design and maintains commonality with existing platforms.