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Aviation history
Flying Empires
 

Short 'C' class Empire flying boat book & drawings

Book description Flying Empires Flying Empires  is written & published by Brian Cassidy and  available direct from the publisher, 200 pages, with index and illustrations, A4 format and Perfect bound with laminated card covers.  £25.00 + p&p. Isbn 0 9529298 0 5 Flying Empires is a contribution to aviation history. It is a companion volume to Phil Sims' book Adventurous Empires, published by Airlife. Phil Sims and I worked on our respective books for many  years, swapping relevant information.  He was more interested in the 'human interest' side of the Empire 'boat story and his book Adventurous Empires covers this corner of aviation history brilliantly.  I am more interested in the technical aspects of the Empire 'boat saga so Flying Empires concentrates on the construction and operation of the 'boats.

Flying Empires traces the pedigree of the S. 23, S.30 and S.33 Empire flying- boats from the early Felixtowe F
flying-boats, through Short's biplane boats of the 1930s,  to the first of the Empires as it emerged from the Seaplane Works at Rochester on 1 July 1936. The names of the boats are listed. The construction is described in considerable detail. The functions of the crew are outlined and the operation of the boats on the water, taking off, in the air and alighting described. Refuelling, flight refuelling and maintenance are covered.

Short Bros. built forty-two, nearly forty-three, Empire flying-boats at Rochester, Kent.
The forty-third  'boat was nearly three quarters complete before it was scrapped.

The Empire boats were designed in 1934 to implement the Empire Air Mail Scheme, carrying unsurcharged letter mail throughout the British Empire and Dominions between the terminals at Southampton, Durban and Sydney - later continuing to Auckland, New Zealand. Some of the payload was available for small numbers of passengers and freight.

The boats were operated by Imperial Airways Limited (IAL), QANTAS Empire Airways (QEA) and Tasman Empire Airways Limited (TEAL)  and later, British Overseas Airways Corporation (BOAC).

Brief histories of the Empire Air Mail Scheme and the Horseshoe Route are included.

The IAL and QEA Empire flying boats ran the Empire air Mail Scheme for two years and ten months, ending with the outbreak of World War II in 1939. With Pan American Airways, the IAL 'boats pioneered the Atlantic crossing and one was employed on the Bermuda-New York service. Two 'boats were armed and impressed into the Royal Air Force to become casualties of the Norwegian campaign.  IAL changed to British Overseas Airways Corporation (BOAC).

The second chapter of their service history started in 1940 when the Horseshoe Route came into operation. The Horseshoe 'boats pounded the route from Durban, through the Middle East and across India, to Sydney and return.  Diversions took two of the boats to Crete to evacuate British military personnel. The Horseshoe was broken at Singapore and the QEA 'boats on the Australian side of the break became involved in the hostilities. Some QEA 'boats were armed as were the two TEAL boats that maintained the link between Sydney and Auckland throughout the war, doubling as reconnaissance bombers as required. Two BOAC 'boats were converted to military status for service with the Royal Air Force. The Horseshoe lasted for six years and nine months.

Sixteen of the original forty-two survived the war, to be broken up for produce. The very last Empire 'boat remained as a landlocked exhibit in Auckland until it too was hauled off for scrapping some time after 1954, so ending a significant era of aviation history of the 1930s & 40s.

Empire flying boat drawings

Sheer plan or side elevation of standard MarkI S.23 . Original is drawn to a scale of 1:20.

Flying Empires  does not include a General Arrangement drawing of a 'C' Class 'boat and for this I have been critised by aviation historians.  However, I could not find any authentic Short Bros GA drawings to include, despite searching for more than fifteen years.  Various versions of small scale diagrams of the Empire 'boats exist.  If these diagrams are blown up to a common scale for comparison inevitable, but surprising, anomalies appear.  For the hull, these are most marked in the length of the hull aft of the main step and in the height of the rudder.  The most accurate detailed small scale drawing that I have found is the painting by Keith Bloomfield that forms the centre spread to Profile Publications No. 84. The most surprising is the line diagram in Chris Barnes' Putnam publication, Shorts Aircraft since 1900. The hull  in this diagram appears to be some 7 feet (2.13 metre) short, 2 feet (610 mm.) too low and 2 feet (610 mm.) too narrow.

So, to fill the void I have been assembling a set of  1:20 scale General Arrangement drawings.  A side elevation  or port side sheer plan heads this section and a scrap of the plan is at the foot of the page.

Before completing the drawings, I am appealing for the sight or loan of any authentic Short Bros.' prints with the drawing number prefixes of  S.23, S.30 or S.33,  to check their accuracy.  It seems certain that all the original tracing masters and stress calculations have been destroyed and all the prints seemed to have completely disappeared.  Luckily, some fragments of the Type Record drawings have been found  recently in a cupboard in Northern Ireland.  They provide dimensions for some of the details - ailerons, fin and rudder, engine nacelles and details of the mainplane and tail plane spars.  But there was  no general arrangement drawing giving the significant controlling  dimensions.  It was lucky too, that  Major Mayo's copy of the Maintenance Manual for the S. 23s was with  his papers when they were given by his daughter to the Science Museum  in London.  I have a photocopied copy of the Maintenane Manual in the  original  Short Bros.' screw bound covers.

All the 42 Empire 'boats were built in the main assembly shop - No. 3 Shop - of the Seaplane Works at Rochester in Kent, beside the River Medway. The first, S 795 G-ADHL CANOPUS, went down the famous, and still existing, slipway outside the Shop in July 1936 and the last S.1026 G-AFRA CLEOPATRA, in May 1940.

If you have any Short Bros.'drawings or prints or have ever seen any Short Bros.' S. 23 drawings or prints, I would like to hear from you.

The heading drawing of the sheer plan, or port side elevation , of a typical  S.23 'boat is my  working base drawing.  The outline is taken  from (the tiny) Diagram 35 of the S.23 Maintenance Manual. which also shows the hull plating.  The other Diagrams mentioned here are also from the Maintenance Manual.  The dimensions of the positions of the steps are shown on the diagrams on pages i and ii of the Manual.  The outline of the plan of the hull is traced from a considerably blown-up part of Drawing  S.23C.013 - one of the parts of the Type Record discovered recently.   The hull profiles at Frames 15/16 and 20/21 are shown on Drawing   S.23.C.300.12 - a tooling drawing and the only  near-complete Short Bros.' drawing that I have found.  It shows not the aircraft but the shop truck inserted under a hull in the gantry in No. 3  Shop, to enable the hull to be withdrawn when completed.  Some versions of the hull plating diagram show four  sections - (A) between Frames 8 & 9, (B) between Frames 25 & 26, (C) between Frames 38 & 39 and  (D) between 45 & 46 - starting points to develop a full set of lines when enlarged.

The plan of the mainplanes is drawn round the spars.  The dimensions are shown on page i of the Maintenance Manual.  This enables the sweep back of the leading edge to be calculated.  The position and length of the datum chord is known and so the sweep forward of the trailing edge can be established.  Diagram 22 of the Maintenance Manual  shows the spars and the Type Record gives the lengths of the members.  The dimension for the elliptical tip is in the Type Record and checked with a tracing taken by an apprentice during his days in No 3 Shop, when the 'boats were being built.   The plating of the mainplanes is filled in from Diagram 29 of the Manual and details of the ailerons and flaps come from the Type Record.  The co-ordinates of the modified Göttingen  Gö436 aerofoil are available and, with the thickness to chord ratio of 19.1% on the centreline of the aircraft, 18.78% at the root and 9% at the tip -  all from the Type Record -  the profiles can be calculated  and  drawn by computer.

The details of the horizontal alignment of the engine backplates came from  Alf Cowling's notebook.  A drawing of a Bristol Pegasus engine on an Empire nacelle was discovered in the library of  at RNAS Yeovilton . The key dimensions of the engine were taken from the magnificently preserved,  and beautifully sectioned,  Pegasus at the Industrial Museum  in Bristol.  A mint condition Pegasus is also part of the Science Museum's collection in London.  The Bristol Museum also displays a rather depressed looking,  and incomplete, Perseus sleeve-valve engine similar to those used on most of the S 30 'boats.

The tail plane span is in the Manual and the plan shown on Diagram 39.  Details of the elevators, fin and rudder are in the Type Record .  The aerofoil profile  for both is RAF 30, blown up to 13.75%.

The floats are shown as Diagram 48 of the Maintenance Manual, the patented springing device is in the patent documents  in the Patent Office in London and the rigging angles supplied by Alf''s notebook.  The float centres are in the Manual  and added detail comes from the floats of  Sandringham  VH- BRC in the Hall of Aviation at Southampton.

Sets of drawings will be  available later  when  completed.  They will be then available  at cost of duplication and postage, to anyone interested in the Empire 'boats.  The drawings  show  'HL CANOPUS , S.23  Pegasus engined 'boat, as originally launched with sprung floats and the dipole radio antenna.