Blackburn - pre-WW2 monoplane commercial land transport projects


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In the 1920s and 1930s Blackburn Aircraft made little impact in their endeavours to sell commercial transport landplanes. Little impact, as in none whatsoever. Yet between 1925 and 1934 they did design and offer a number of commercial transports. The biplane C.A.3, C.A.4 and 5 all tentative layouts for up to 14 passengers for possible use on Blackburn’s North Sea and Aerial Transport Company routes in East Africa and C.A.6 to 9 all smaller biplane designs.

After 1927 the company began to focus on monoplane designs, many closely related, but all failed to generate any interest with the airlines. Their final offering was radically different, built but never flown, a victim of the higher priority given to military projects…. and continuing customer disinterest. All but the last project were designed under the leadership of Frank Bumpus, chief designer and company director since 1919, and George Petty, the last was the brainchild of Frank Duncanson, a highly experienced engineer recruited from Gloster in 1933.

Prior to 1928 Blackburn had concentrated most of their efforts on military aircraft, mostly single-engine types for the Navy, and large flying boats. The flying boats were developed under the design leadership of John Rennie, former deputy to John Porte, father of the Felixstowe flying boats during WW1. The R.B.1 Iris, ordered to Specification 14/24 was a successful design, used for a variety of experimental purposes, but failed to attract significant orders. Civil derivatives were offered too but failed to sell.

In 1927 the Air Ministry issued specifications for three-engined military flying boats of various types. Saunders produced the Severn, Supermarine the Southampton Mk X and Blackburn the R.B.2 Sydney. At that time Short Bros were in the process of building the three-engined Calcutta for Imperial Airways so it was somewhat inevitable that civil derivatives of the other three would soon be on the drawing boards. In 1928 Blackburn were in negotiation with Alan Cobham to launch a new airline to operate on routes into Africa, for which Blackburn designed the 16-seat Sydney-based C.B.2 Nile. At this point it was decided that the Nile should also be used as the starting point for a commercial transport landplane.
C.A.10 (C.B.2.E)

The 12-seat airliner was designed utilising Nile flying surfaces and three engines and was probably designated C.A.10 but included first under the same Blackburn specification C.B.2.E. in mid-1927. It was to be powered by three Bristol Jupiter IX radials. After the finance and commercial departments in the company questioned the necessity of the additional costs associated with the design incorporating engine mounts and parts of the wing that differed from those on the Nile it was modified later that year.
1 CA10.jpg

In 1930 the Cobham-Blackburn airline foundered when they failed to secure the support, and more crucially subsidies, from the Air Ministry, and the partially complete Nile prototype was abandoned. However in February 1929 the landplane derivative had been further modified as the C.A.13 and C.A.14 before being scaled down slightly to reappear as the 10-12 seat C.A.13A. This aircraft was offered in two forms, either with three Armstrong-Siddeley Lynx or a single Bristol Jupiter IX.

2 CA13A.jpg

3 CA13A_2.jpg
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In mid-1929 the C.A.13A was taken as the basis for the next offering, the C.A.15A, which was developed in both monoplane and biplane form. By November the project became the C.A.15B and a slightly smaller 2-engine version the C.A.15C. A single example of both the monoplane and biplane C.A.15C were ordered by the Air Ministry to assess the relative merits of each form, but the project was not pursued with great urgency and the aircraft did not fly until mid-1932, by which time the debate over biplane versus monoplane was becoming somewhat academic as structural and aerodynamic advances rendered the strut-braced monoplane pretty much obsolete.

The C.A.15D, of late 1932, was the last-ditch attempt to in generate interest in the aircraft. It was a twin-engine 10-seat monoplane with the wing designed utilising Helmut Stieger of Monospar’s patent single wire-braced spar system. It also introduced a retractable undercarriage.
4 CA15d.jpg

The Aircraft Investment Corporation Ltd, with major share holdings in Saunders Roe and a short-lived company (1929-1931) named Blackburn Consolidated Ltd, employed Sir Henry Seagrave as an advisor to aid in the design of a twin-engine light aircraft. The wood prototype was designed in detail and built by Saunders-Roe but production of a metal structured version was to be undertaken by Blackburn as the C.A.18 Seagrave I. Construction of a third example was abandoned when the order was cancelled but was resurrected as the C.A.20 Seagrave II in order to provide a test vehicle for Frank Duncanson’s tubular mono-spar wing design. Duncanson had been a designer with Fairey, responsible for the Flycatcher, and subsequently a senior member of the design department with Gloster until he joined Blackburn in 1933. The Duncanson-winged Seagrave II flew in February 1934, by which time Blackburn were well advanced with the design of a larger version.

The C.A.19 was a design for an 8-seat commercial transport, initially an enlarged Seagrave with Armstrong-Siddeley Serval engines before being thoroughly revised. The C.A.21 was the first step, now fitted with four de Havilland Gipsy Majors, Napier Javelins or Servals.

5 CA21 early.jpg

The final aircraft, now a 12-seat airliner powered by two Napier Rapier VI, was completed in July 1936 as the H.S.T.10 but was never flown as the factory was fully committed to military production under the RAF Expansion Schemes and no potential customers had shown any interest.
Great work my dear Schneideman,

an what about Blackburn; mailplane 21/28 ?.
Great work my dear Schneideman,

an what about Blackburn; mailplane 21/28 ?.
Well, not really a commercial transport but please go ahead an add a GA if you have one.
Since you mention Jackson's Putnam it is worth saying that for unbuilt projects it has a lot of omissions and quite a few errors. One reason is that Blackburn rarely put project numbers on their GA drawings and also many lack dates. The Specification documents that include the drawings are also inconsistent, some have Specification numbers and some do not, and again they did not always date them. How they managed their catalogues and records is anyone's guess.

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