D-class lifeboat (Avon S650)

The D-class lifeboat (Avon S650) was a sub-class of 4 inflatable boats operated as part of the D-class between 1971 and 1986 by the Royal National Lifeboat Institution of the United Kingdom and Ireland. It was superseded by the D-class lifeboat (Zodiac III).

Utilization
For more than 60 years the D-class has served as the workhorse of the RNLI Inshore Lifeboat (ILB) fleet. The D-class is one of the few RNLI types not to feature a rigid hull. The D-class was specifically designed as a light and highly manoeuvrable rapid response craft, especially suited to close shore work.

There were only 4 Avon S650 boats in service with the RNLI

Design and construction
The D-class lifeboat consists of two sponsons, together housing four inflatable segments intersected by baffles.

This was one of the smaller classes of lifeboat operated by the RNLI, and while there were only 4 Avon S650s in the fleet, the D-class were a common sight at lifeboat stations around the coast. Unlike other members of the ILB fleet, the D-class does not have a rigid hull; all others, with the exception of the Arancia, hovercraft and ALB Tenders, are Rigid Inflatable Boats (RIBs).