Forgotten Lancaster; The B.VI

July 20, 2023

See, I can already hear what you are saying out there: “Really Ed? You’re doing the Lancaster? One of the most famous combat aircraft to ever fly? You’re really doing the Lancaster? Sell out!”

But actually, this particular model of Lancaster, the B.VI, is so obscure that I had never even heard of it until it was bought to my attention by John Dell of the Dinger Aviation website – long term readers will know that I get most of my best leads from him. And I’d would have say this is one of them.

The Lancaster is, quite rightly, legendary, essentially the mainstay of RAF Bomber Command from 1942 until 1945. And it was constructed in understandably large numbers, with more than 7,300 built. But of those just ten were B.VI’s.

This model originated from an Air Ministry specification B14/43 that wanted a bomber aircraft that could operate at 35,000 feet and had superior range to the Lancaster and other heavy bombers in service, principally with an eye to future deployment to the Asian theatres and the war against Japan.

Avro entered two options, the Lancaster’s B.IV and -V. These would eventually be adopted, though renamed as the Lincoln I and -II. But as the proposed aircraft were a fairly extensive redesign of the Lancaster, a fact that led to it ultimately been classed as a new aircraft entirely, it was thought that a more straight forward improvement of the existing Lancaster by putting more powerful engines on it would be worth exploring.

Thus, we come to the Avro Lancaster B.VI. The first two aircraft allocated were DV170 and DV199, which were newly built Lancaster B.IIIs and were supplied to Rolls Royce for conversion. This principally entailed switching out the two aircraft’s Packard built Merlin 28s for Rolls Royce’s Merlin 85s.

The new engines were installed in a concept that Rolls Royce was working on; the Universal Power Plant (UPP). The idea – which is similar to the so-called “Power Egg” – was that on multi-engine aircraft instead of the powerplants being integral to the design they instead could be essentially modular that could be added or removed as a complete unit.

In terms of the different engines, on paper the differences might seem minor, as the -28s generated just over 1,500hp in combat operation, while the -85s produced around 1,700hp. Admittedly, the increase in power would no doubt be welcomed, but was a marginal increase in an aircraft as big as a Lanc. But here we get the trap that is easy to fall into if we just judge things by numbers in books.

Because the Merlin 85 had a two-speed, two-stage supercharger.

This in essence was very similar to the engine that the Spitfire MK.IX or P-51D Mustang were fitted with…and it meant that it produced much more power at much greater altitudes.

This soon was demonstrated in testing of the new aircraft. The standard Lancaster B.I being built in 1944 and equipped with four Merlin 24s was found in testing to have a top speed of 280mph (450 km/h) at 10,000 feet (3048m), a cruising speed of 200mph (322km/h) and a service ceiling of 21,400 feet (6523m).

The B.VI, in comparison, had a top speed of 313 mph (504km/h) at 18,300 feet (5578m), while it could cruise at 279mph (449km/h) at 23,900 feet (7285m).

Essentially the B.VI could cruise at basically the then-current Lancaster’s top speed at an altitude that the earlier aircraft couldn’t reach. That’s quite an impressive jump.

Indeed, though combat operations were generally conducted by the B.VI at around 23,000 feet, there are stories of some crews flying missions at 30,000 feet (9,144m). The limitation seems to have not been the engines or aircraft, but rather whether the tail gunner would freeze.

Certainly, the B.VI engendered some interest, though as said only ten were ultimately converted. And of these only four would be used operationally when in 1944 a few of these were supplied to the Pathfinder Force. This was an elite series of squadrons whose job it was to guide the main bomber streams to their targets and mark them to help ensure bombing accuracy.

To go with their specialist role the service aircraft had their front and dorsal turrets fared over and were fitted with cutting edge electronics for the time, including radar jammers and loads of chaff – codenamed window by the British – so as to confuse German defences.

With this they conducted operations generally over the heavily defended Ruhr area of Germany throughout 1944, often in daylight.

But despite their much improved performance, which saw them generally employed for diversionary roles or as command aircraft for raids, the B.VIs proved to be problematic. On the ground the powerful engines had a nasty tendency to suddenly surge or hunt, and the pilots had to keep the revs high while taxing to prevent oil build up on the sparkplugs, which didn’t do the aircraft’s brakes a lot of good. Additionally the improved performance meant that the B.VI’s had problems staying slow enough to stay with the main formations which were made up of the slower early model Lancasters.

They also were reputedly a pig on the amount of servicing they required, which didn’t endear them to their ground crews.

All said the B.VI’s were a bit awkward, especially in the very limited numbers that they were used in and so they only saw a few months active service before being withdrawn in November 1944 with one of their number lost in action.

So, it might seem the aircraft was a failure. But in fact, they provided one service quite handsomely because the issues the Lancaster B.VI would experience both in testing and in combat all paid off when the Avro Lincoln entered service in August 1945.

This used the same Merlin 85 in a UPP configuration as the Lancaster B.VI and as a result many of the issues had been ironed out by the time the Lincoln reached squadrons because of the experience and experimentation done with the B.VI’s.

Plus withdrawal from combat also didn’t mark the end of the B.VIs service. Several carried on being used as engine test beds, including ND 784, who got to become one of the most peculiar-looking of all the Lancs when she was modified with different experimental turboprops in her nose for testing.

Sources/Related:

Avro Lincoln; The Super Lanc That Was Outdated When it Arrived

The Single Tail Liberators – Consolidated XB-24K-and-N

The Vickers Windsor; Wimpey’s Big Brother

The Avro Manchester; Mighty Oaks from Little Acorns Grow

 

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