The Short SA.4 Sperrin; Britain’s Back-Up, Back-up Nuclear Bomber

July 9, 2024

The V-Bombers; Britain’s cool and quirky answer on how to drop atom bombs on the Soviet Union.

This trio of aircraft not just represented Britain’s entry into the nuclear power’s club, they also demonstrate the evolving ideas and technologies that were developing in aviation in the ten years after the end of the Second World War. The fact that the British actually went to the expense and trouble of developing three entirely different aircraft for the role of atomic bomber may seem to be a little excessive, especially as Britain was at the time basically completely broke, but it does illustrate just how important the British thought getting a modern nuclear capable bomber into service was.

The fact was, the British establishment couldn’t run the risk of developing a complete lemon as their aircraft deterrent, which was at the time their only atomic weapon delivery system, and so they went with the trouble and expense of building three just to be sure that one of them would work. Indeed, the RAF was adamant that they needed to develop and field at least three different aircraft. The leaders of the service remembered well the lesson from the 1930’s, where had the RAF been forced to choose between the heavy bombers under development then – the Avro Manchester, Short Stirling, and Handley Page Halifax – they might well have ended up with the Manchester as their sole bomber, which could have been disastrous for the subsequent bomber campaign.

As it was, all of the V-bomber designs – the Vickers Valiant, the Avro Vulcan and the Handley-Page Victor – proved solid performers, with the Vulcan and Victor enjoying long service lives and the Valiant, though not having the longevity of its fellow-V’s, still seeing the most actual combat usage.

But what isn’t so well known is that the British didn’t just build three nuclear bombers to make sure that they had an effective deterrent. They actually built four!

Meet the Short Sperrin.

When the specification for what became the V-bombers was laid out in 1946, it was realized that the requested performance was a quantum leap over the existing aircraft in use by the RAF and so it may be prudent to request a less capable aircraft in case the original spec proved impossible to achieve. The V-bomber’s requirement wanted an aircraft capable of carrying a 20,000lb (9,072kg)bombload – or a 10,000lb (c.4.500kg) atomic bomb – and hit a target 1,700 miles away (2,800 km) from an altitude of 50,000 ft (15,240m) at a speed of 580 mph (930 km/h).

For the “insurance” aircraft, the requirement was cut so it would make its attack at between 35,000 and 45,000 feet (10,668m to 13,716m) at a speed of 500mph (805km/h).

And that’s it; payload and range were to be the same.

For contrast, the Avro Lincoln, the RAF’s primary heavy bomber at the time, could manage a maximum bombload of 14,000lb (6,350kg) out to 2,240 mi (3,600 km), but only at a mere 260 mph (420 km/h) and at an altitude of 20,000 ft (6,100 m).

Oh, and it couldn’t carry a nuke.

So, insurance design it might have been, but the specification was still a vast improvement over the RAF’s existing abilities. Indeed, the thinking was that the aircraft that was chosen would probably be ordered to act as an interim type until the more advanced designs got into service a few years after.

Four companies tendered for this back-up bomber, and Short’s of Belfast was selected in 1947 to build two prototypes and a single unpowered model for static testing. Because of the perceived need for speed (in development, that is), the Sperrin was expected to be ready for operational deployment by 1953.

Short’s, using the initial company designation of SA.4, got to work and produced an aircraft that is a clear intermediate type between aircraft of the Second World War and the upcoming jet age, and one, let’s be honest, that looks basic.

Ironically, the initial groundwork was laid for what became the Sperrin in Short’s initial bid to build one of the actual V-bombers. This would have had an advanced experimental wing design, but which was considered too radical even in comparison to the other cutting-edge designs that ended up being chosen.

So, with the Sperrin, Short’s went conservative, logical considering the requirement, and fitted the aircraft with a wing with only a slight sweep on its leading edge and even a tail derived from the Sunderland flying boat!

The conservatism of the Sperrin design actually led to friction between the RAF and Ministry of Supply, who pretty much put the order in straight off the bat. For the RAF, the Short design looked to be lining up to be completely obsolete even before it could get into service – which is both true and, weirdly, a little unfair. After all, the Sperrin was intended to be a backstop to the more advanced designs in development intended to be the actual bomber force and an interim type to get aircrew familiar with higher performance jets, so expecting it to be some sort of super-duper performer seems disingenuous.

Mind you, I can sympathize with the RAF High Command’s concerns about wasting precious resources and potentially getting saddled with a lemon, avoiding which was the whole point of developing several separate nuclear bombers in the first place after all.

And with the Sperrin Short’s did exactly what was asked of them; they turned out a conservative design allied with new cutting-edge technology – practically a British equivalent to the Martin XB-48.

In fact, I’d go as far as it being a bit of a brute of an aircraft, with its slab sided looks and apparent indifference to streamlining. But, as I keep pointing out, comparative simplicity was the point.

For all that, the design did deliver what was required of it. Constructed of aluminium, the Sperrin really was what many commentators have described it as; a Second World War aircraft design with jet engines stuck on it.

Those engines, initially Rolls Royce Avon’s but later switched to de Havilland Gyron’s, were podded one-atop the other in a rather ungainly design. Again, not elegant, but simple to design and speedy to produce.

The Sperrin ‘s performance also wasn’t bad. It was never going to be an acrobatic aircraft, but the initial prototype clocked a respectable top speed of 564 mph (908 km/h), service ceiling was the required 45,000 feet and it could carry the specified payloads.

The principle problem for Short’s was that they got gazumped.

Firstly, the British decided that, with the Lincoln being so obviously obsolete they needed to get something into service immediately if they were to retain even a modicum of an independent strategic bombing force. In 1950 they began to take delivery of B-29’s, named “Washington’s” in RAF service that, though also on old design was much better than the Lincoln’s and gave the service some long-range teeth in the face of deteriorating relations with the Soviet Union.

The Washington’s thus provided a sort of intermediate steppingstone to the V-Bombers, removing one factor in the need for the Sperrin.

The second was that an unexpected rival had arisen.

As said, the V-bombers was a triumvirate of aircraft. But that wasn’t the original intention. The plan had been that Avro and Handley-Page would build their advanced designs to be the future V-bombers.

Vickers weren’t selected.

However, nothing daunted, Vickers got on with designing their proposal, the Type 660, and they did a brilliant job of it. In 1949, recognizing the excellence of the design from the development work and the solemn promises of the Vickers design team that they would bring in the aircraft on time and on budget (which they did!) the Ministry gave an order to proceed to Vickers with their new aircraft.

This would become the Valiant and would both provide the intermediate type for RAF’s bomber command to familiarize with while being a much better aircraft than the Sperrin.

And worse for Short’s, the prototype Valiant flew before their supposedly simpler design, getting airborne in May 1951 while the SA.4 prototype didn’t fly until August the same year.

To be honest, Vickers wanted the order more, and the flat-out effort to get the Valiant prototype flying, as well as the clever design work poured into the aircraft, meant that it was a considerably better aircraft than the simple Sperrin.

So, between the addition of B-29’s to the RAF and the creation of the Valiant, there was no need for the Sperrin any longer. Of course, the British government had purchased two of the aircraft and the static mockup, and though the Sperrin was never going to get ordered it didn’t do to waste them, so they were switched to experimental work.

The first prototype was altered to run trials of the afore-mentioned De Havilland Gyron engine, which was projected to produce between 15,000 and 20,000 lbf – considerably more than the 6-6,500 lbf produced by the original Avon engine fit.

Here the Sperrin’s more primitive design was useful, and it was comparatively easy to alter the wing engine pods to take the considerable bigger Gyron for its flight tests.

This aircraft flew until 1959, used for various experiments, but once they were concluded it was considered surplus and scrapped.

The second aircraft, which first flew in 1952, actually did play a useful part in Britain’s nuclear bomb development program. Between 1953 and ’56 it was used by the RAF to carry and drop the inert carcasses of proposed atomic bomb casings, testing which led to the development of the Blue Danube bomb, Britain’s first deployable nuclear weapon.

It was then used as a source of spare parts for its sister Sperrin as that aircraft continued its experimental work, gradually being broken up and eventually also heading to the scrapyard.

And that is the Short Sperrin. An unusual aircraft that essentially delivered what was required of it, even if that requirement was subject to disagreement, but which was literally outclassed by developing technology (and more ambitious rivals) even as it took shape at the factory.

Sources/Related:

Britain’s Cold War Bombers

https://www.jstor.org/stable/26279483

https://planehistoria.com/short-sperrin/

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