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 It was superseded by the D-class lifeboat (Zodiac III).^[1]

Quick Facts Class overview, General characteristics ...

Class overview
Name	D-class (Avon S650)
Builders	Avon Inflatables
Operators	Royal National Lifeboat Institution
Preceded by	D-class (RFD PB16)
Succeeded by	D-class (Zodiac III)
Built	1971
In service	1971–1978
Completed	4
Retired	4
General characteristics
Class and type	Avon S650
Length	5 m (16 ft)
Beam	2 m (6.6 ft)
Propulsion	1 × 40 hp Evinrude outboard engine
Speed	20 knots (23 mph; 37 km/h)
Endurance	3 hours at full speed
Capacity	10

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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

The D-class lifeboat consists of two sponsons, together housing four inflatable segments intersected by baffles.^[2]

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).