Designs

Much of this information is taken from the excellent reference ‘Rescue from the Skies’ by Stephen Brewster Daniels. The book includes much more detailed information including the design parameters and process, engines, gear carried, other designs produced but not built and so on. But even this book was not a single source and the information is augmented below where necessary.

UK Lifeboat design comparisons

The design of an airborne lifeboat was a complicated undertaking with many different, often contradictory, requirements. It required input from a great many – aeroplane engineers, naval architects, equipment manufacturers and more. And the first lifeboats were dependent on the vision, energy and drive that Uffa and the RAF leaders such as Group Captain Waring provided to overcome the many challenges.

The following lists lifeboat designs which were actually adopted. The Mark I, Mark II and RN-1 were designed by Uffa Fox and built during the war. The Mark III was designed and built by Saunders Roe after the war. The diagrams are broadly to the same scale, demonstrating the relative sizes governed by the aircraft to which they were fitted.

Number of Lifeboats Built

There is some variation in the number of lifeboats across the different references. ‘Rescue from the Skies’ by Stephen Brewster Daniels records 598 Mark I, IA, II, IA built for wartime operations. Neville Cole quotes an additional 116. And there were 24 RN-1 and 50+ Mk III which were never used operationally. Irrespective the diagram below gives an indication of the numbers by design.

A brief summary of lifeboat development

The Airborne Lifeboat was born through the combination of the vision Group Captain Waring and Uffa Fox’s enthusiasm, energy and commitment. Many others were involved, and there were multiple designs. Uffa Fox is credited with the design of the three that went into production in the UK during the war: The Mark 1; the Mark II; and the Navy’s RN-1. Saunders Roe designed and produced a Mark III lifeboat after the war. And Uffa’s Mark I formed the basis for a series of American designs, particularly the A-1 and A-3.

Each design had to meet not only the requirements of a lifeboat but also the limitations of the plane that would carry it. The important factors are summarised on this page. The carrier aircraft imposed many design constraints in terms of size, shape and construction: the lifeboat had to fit snugly and tightly to the aircraft without a gap between, to protect the lifeboat and flight characteristics. It also had to fit between the aircraft and the ground on land. The RAF had been able to release only the ageing Hudson aircraft for Airborne Lifeboat duties. The Hudson had very little ground clearance, particularly aft, and the Mark 1 lifeboat reflects this.

Even before the Hudson and Mark I went operational in 1943 the RAF were able to allocate some much larger Warwick aircraft for the lifeboats. Initially the gunwale of the Mark I was simply modified, as the Mark IA, so that it would seal to the Warwick but the larger plane meant that it could carry a larger lifeboat. The Mark II was therefore designed for the Warwick. And then as Lancasters became available the Mark II gunwale was modified into the Mark IIA.

Towards the end of the war, the Navy requested a lifeboat that could be used with their Barracuda aircraft. The RN1 was necessarily smaller. There are no records of it ever having been used operationally.

Read more about the aircraft used with Airborne Lifeboats on this page.

The Mark III was designed by Saunders Row after the war for build in aluminium to be fitted to the Shackleton aircraft. The design aimed partly to overcome issues which the wooden hulls of the earlier designs in the Mediterranean and tropical environments.

Of course, the RAF was supported extensively by the US Air Force. From the earliest days work was done to apply the Mark I and Mark II designs to the B-17 Flying Fortress. The US built on the UK lifeboats and designed the A-1 lifeboat and several other variants. These are superficially covered on this website.

UK Lifeboat Designs – Key Statistics

	Mark I	Mark II	Mark III	RN-1
Service	RAF	RAF	RAF	RN Fleet Air Arm
Aeroplane	I – Hudson IA – Warwick	II – Warwick IIA – Lancaster	Shackleton	Barracuda
Capacity (people)	7	10	10
Top Speed (knots)	6	7	6.6
Endurance (days)	7	7	14
Length overall	23′ 2″	30′ 2″	32′	17′ 9″
Length waterline	22′ 0″	30′ 0″	30′ 0″
Beam	5′ 5″	6′ 0″	7′ 1″	4′ 10″
Draft	9″	11″	13″
Displacement (tons)	0.5	0.75
Max All Up Weight (lbs)	1700	3942	4460
Constructions	Double skin mahogany	Treble skin mahogany.	Aluminium alloy
Engine	Two 4hp BPC ‘Middy’ 2-stroke. Protruding propellers.	One 4 cylinder Austin Marine 8hp, propeller in tunnel	One 2 cylinder Vincent HRD Marine T5/AM
Number Built	I – 71 IA – 402	II – 144 IIA – 97 (MkIIA were all rebuilt from MkII)	56	24
Operational	Feb 1943	1944	1948	1945
1st Rescue Drop	5th May 1943	1944	Never used	No record
Notes	Size was limited by the low ground clearance of the Hudson.		The MkII was built in aluminium partly to overcome issues experienced by wooden boats in warm climates.

The US Lifeboats