Selected informative quotes from "Flying Empires Short 'C' class Empire flying boats", Brian Cassidy, Queens Parade Press, 1996-2004. ISBN 0-9529298-2-1 NOTE: Character encoding assumptions: '«' = '1/2' '¬' = '1/4' Dimensions: Maximum beam: 10ft S.23, S.30, S.33 (pp.26,27) Airscrew semi-diameter: 6ft 4.5in (pp.27) Inner engine center-water S.23@40500 lbm in fresh water: 11 ft. 8 in Maximum depth of hull at Frame 20: 16ft 6in Span: 114ft S.23, S.30, S.33 (pp.28) "The gross area of the mainplanes for all types was 1720 sq. ft. with a nett area including the flaps, ailerons and nacelles of 1510 sq. ft. - normally quoted as 1500 sq. ft. The aspect ratios were respectively 7.56 and 8.60. The datum chord measured 16 ft. 5.5 in., at a point 23 ft. 11.32 in. from the centre line of the aircraft at right angles to the plane of symmetry. The modified Gö 436 aerofoil used had a thickness to chord ratio of 18.78 % at the junction with the hull, diminishing to an hypothetical 9% thickness to chord ratio at the tip." (pp.28) "The mainplane had a medium taper in plan, with a ratio of 1:2.47. If drawn out, the leading and trailing edges and spar plan angles appear to originate from a common point on an extension of the spar centre line, distant some 92 ft. 4.7 ins. from the centre line of the hull. The leading edge was swept back at an angle of 4 deg. 16 min. and the trailing edge swept forward at 9 deg. 25min. 14 sec., joining with a double elliptical tip, 8.6 ins. to the rear of the spar centre line. The ellipses were tangential to the lines of the leading and trailing edges 10 ft. inboard from the tip. The common major axis of the ellipses stretched 26 ft. 8 ins. inboard from the tip." (pp.28) "The aerofoil datum line was set at a positive incidence of 3 deg. to hull datum. The spar centre line was at right angles to the centre line of the hull, at 31% of the mainplane chord, coinciding with the centre of pressure of the aerofoil, with the front and aft spar booms toed in towards each other at angles of 2 deg 14 min. 24 sec. The hull datum point was the leading edge of the datum chord. The centre of gravity was 4.56 ft. aft of datum and the range measured 11.3 in. for the standard S.23'boats, or 0.057% of the datum chord. The spar centre line was nearly in the centre of the range, 5.6 in. forward of the rear limit. The special category, Mark III S.23 'Atlantic' 'boats had a much reduced centre of gravity range of only 3.7 in. The spar axis was a straight line through the mid-camber points of the aerofoil at 31% chord, set at a 3 deg. dihedral. The upper surface of the aerofoil had a nominal dihedral of 1 deg. on the spar centre line." (pp.28) "With a 'clean' wing, approaching the stall at an angle of attack of 17 deg., the respective coefficients were 1.65 and 1.48. Flaps increased the lift coefficient. At the same angle of attack, the modified profile had a coefficient of 1.85 with 12 deg. flap and 2.08 with 25 deg. flap." (pp.29) "Arthur Gouge quoted a minimum 9 deg. positive angle from datum as the trim angle of an Empire 'boat as it was about to leave the water rather than the 12 deg. angle of the tank tests, putting the mainplanes at an angle of attack of 12 deg. with the engine thrust line aligned with the aerodynamic chord line, a further 1 deg. 8 min. up. At take-off, the modified aerofoil gave a coefficient of lift of 1.4 with the 8 deg. flap setting" (pp.20) "The wing loading chosen for the S.23 'boats was 27 lb. per sq. ft." (pp.29) "The wing loading ... gave them a cruising speed of 143 knots. The later S.30 and S.33 'boats, with all-up weights of 53 000 lb., had wing loadings of 35.33 lb. per sq. ft. As the power loading was constant, the theoretical cruising speed should have increased to 153 knots." (pp.29) "The ailerons, of Frise form, were carried on four set back hinges, mass balanced to prevent flutter, with a 21 lb. weight placed 47 ft. 41/2 ins. out from the aircraft's centre line. They spanned 24 ft. 1.33 ins with an inboard chord of 4 ft. 8.3 ins and had an area of 67 sq. ft. When correctly rigged, they drooped slightly by 21/64 in. and some had fixed trim tabs between ribs 13 and 15. The aileron volume was 0.0462." (pp.30) "The upper surface of the flap used on an Empire 'boat was a nearly true segment of a cone, slightly flattened towards the trailing edge, where the retracted flap formed part of the upper surface of the aerofoil. Let into the upper surface of each flap were the tracks, which enabled the flap to move out and down, turning on the axis of the cone with a vertex angle of 10 deg. 30 min. The under surface was slightly curved, conforming to the modified Gö 436 aerofoil profile." (pp.30) "The flaps on standard S. 23 'boats were moved by a single small electric motor, which took a full minute to wind them out to the full flap position of 25 deg. and a minute and a half to retract the m." (pp.30) "Each flap had a span of 26 ft., a chord of 33% of the mainplane chord and an area of 149 sq. ft." (pp.30) "At a take-off flap setting of 8 deg. or 1/3 OUT, the mainplane area increased by 55 sq. ft. and as the angle of incidence was about 7 deg. at the start of the take-off run, the flap increased the coefficient of lift from 0.9 to 1.0. Just before leaving the water, the angle of incidence had increased to about 12 deg. and the coefficient of lift from 1.3 to 1.4. With the flaps in the fully extended position for alighting, the mainplane area was increased by 130 sq. ft. or 8.66%. and the coefficient of lift approached 2.1 as the 'boat rounded out with the points of both steps of the planing surface, touching simultaneously." (pp.30) "The tail plane aerofoils used at Rochester were normally of RAF 30 symmetrical section. For the Empire 'boats the thickness to chord ratio was increased from the standard 12.64% to 13.75%. The overall span of the tail plane was 32 ft. 1.3 in. and chord 9 ft. The combined area of each plane and elevator was 92.5 sq. ft. The area of each elevator was 39.75 sq. ft. with an inset trimming tab of 1.26 sq. ft. The tailplane volume was 0.387. The fin and rudder used the same profile and thickness to chord ratio as the tailplane, with a total area of 122 sq. ft. The chord was 12 ft. 6 ins. The rudder area was 52.46 sq. ft. with two inset tabs each of 0.86 sq. ft. area. The lower tab was a conventional trimming tab, while the upper tab acted as a servo to assist in turning the rudder - normal practice for Rochester 'boats with large rudders. The fin and rudder volume was 0.073." (pp.30-31) "The tare weights of the two 'boats are much the same - 12 630 kg. for the Empire and 12 333 kg. for the CL 215T." (pp.55) "The airframe of a standard S.23 'boat weighed about 15 100 lb." (pp.59) "There were fifty-one frame positions in the hull, starting with Frame 1 in the nose and numbering aft towards the tail. Key frame positions were at Frame 6 - the aft extent of the coup - Frames 15/16 - the forward mainplane spar frame and Frames 20/21 - the aft mainplane spar frame. Frame 42 was the construction joint between the hull and the tail section and Frames 44/45 and 47/48 were the fore and aft attachments of the tailplane and fin. The point of the main step was aft of Frames 20/21, sweeping forward to the chines at Frame 19. The rear step was on Frame 34." (pp.61) "A typical strengthening set consisted of 46 skin plates, 1 490 omega-shaped stiffeners, 15 frames and one half frame and 32 lb. of rivets, weighing in all 180 lb. The strengthened frames were inserted between Frames 6 to 24, with the half-frame at the main step. The thickened skin plating extended from Frame 6 to Frames 20/21 - the aft spar frame." (pp.64) "The Maximum Permissible and Tare weights - 40 500 lb. and 27 000 lb. respectively for a standard S. 23 - were painted on the hull in 3 ins. high lettering, below the starboard tail plane." (pp.??) Hull plating diagram. (pp.66) "The mainplanes were built in two halves, port and starboard, around a massive spar box. Each half plane was 52 ft. long, with a chord of 21ft. 0.327 in. at the junction with the hull." (pp.95) "The spar box was formed by a forward and rear spar truss connected by drag struts and braced with incidence bracing wires. The box was completed by covering the top and bottom surfaces with stiffened sheet, riveted in position. The spar box was 48 ft. long, 6 ft. 7.064 ins. wide between spar boom centre lines at the root, and 3 ft. 10.8 ins wide at the outboard end. The spar booms were toed in towards each other about the centre line, at an angle of 2 deg. 14 min. 24 sec." (pp.95) "The flap position indicator and the BLUE indicator light were both on the underside of the coup, roof of the control deck. ... potentiometer for the Smith flap-angle indicator and the 1/3 rd. extension indicator. ... When the flap reached the 1/3 rd. OUT position, the ramp switched the RED indicator light ON and kept it in circuit until the flap reached the same point as it retracted." (pp.99) "The total weight of a half mainplane, complete with engines and ready for lifting, was in the neighbourhood of 5 417 lb. for a short-range wing and somewhat heavier for the long-range version, due to the extra fuel tanks." (pp.109) "The Type Record gives the weight of a complete set of equipment items for a typical standard S.23 Empire 'boat on Empire Air Mail Programme (including the wireless equipment) to be about 2 995 lb. ... The specific gravity of the aviation spirit was variously given as 0.745 or 0.76 - depending on the origin of the refinery feed stock. The latter figure is used here. The specific gravity of the lubricating oil is given as 0.9." (pp.120) "The Type Record gives the following break-down: Airframe 16 718 lb. Engines 7 496 lb. Fuel tanks 249 lb. Fuel and oil 4 960 lb. Equipment 2 995 lb. Paying load 8 082 lb. Total 40 500 lb. " (pp.120) "Typical figures are given below for a standard weight Mark I S.23 'boat - 'HL CANOPUS, a medium weight strengthened S.30 'boat - 'KZ CATHAY - and a heavy weight long-range Mark III S.30 'boat 'CV CARIBOU. S.23 G-ADHL CANOPUS Weight empty 23 055 lb. Weight of fuel 600 gals. 4 560 lb. Weight of oil 44 gals. 396 lb. Weight of aircraft ready to receive paying load plus crew 28 011 lb. Paying load plus crew 12 489 lb. Maximum weight authorised 40 500 lb. S.30 G-AFKZ CATHAY Weight empty 30 070 lb. Weight of fuel 1 000 gals. 7 600 lb. Weight of oil 792 lb. Weight of aircraft ready to receive paying load plus crew 38 462 lb. Paying load plus crew 4 038 lb. Maximum weight authorised 42 500 lb. S.30 G-AFCV CARIBOU Weight empty 28 668 lb. Weight of fuel 2 474 gals 18 804 lb. Weight of oil 174 gals. 1 566 lb. Weight of aircraft ready to receive paying load plus crew 49 470 lb. Paying load plus crew 3 530 lb. Maximum weight authorised 53 000 lb. " (pp.121) Hydrodynamics: Hump at 20kt and 26kt (pp.27) Resistance S.23@40500 lbm, take-off flap: ~8250 lbf@22kt (pp.27) "The line of the keel from Frame 10 aft to Frames 20/21 formed the hull datum line. The normal trim angle for a standard displacement Empire 'boat hull at rest in the water, was 4 deg. 15min.- nose-up. Flying-boat hulls change their attitude as speed builds up during take-off. The tank tests at Rochester showed that as a standard displacement Empire 'boat began to move, the angle increased to 7 deg. at 15 knots, to 10 deg. at 25 knots, with a peak of 13 deg. at 30 knots, and then decreased to about 12 deg. until the 'boat left the water at about 78 knots (144 km. per hr.)." (pp.28) "If a take-off was attempted with FULL flap, especially if the water was dead calm, porpoising could set in at about 50 knots" (pp.28) "The transverse stability of the 'boats was achieved by fitting wing floats of three types. Type 1, with a buoyancy of 6 000 lb., was fitted to the first generation S.23 'Atlantic' 'boats. Type 2, with a buoyancy of 5 000 lb., was fitted to the thirty-one S.23s and probably to the early marks of Sunderland. An untyped float, with a buoyancy of 6 000 lb., was fitted to the later S.30 and S.33 'boats." (pp.31) "All the floats had a single step and pointed aft ends. The revised Type 1 was somewhat finer in the nose than original Type 1 and generally the more 'aerodynamic' in appearance with a very small step - more a discontinuity in the planing surface than a definite step. The block coefficients were almost the same, 0.49 for Type 1 and 0.47 for Type 2." (pp.31) Diagram wing floats. (pp.110) "A typical float and chassis, with the patented sprung bracing, weighted about 260 lb. ... The rigging angles for the forward chassis strut for the Type 2 float, was 90 deg. 4 min. to underside of the mainplane. The angles were 89 deg. 10 min. for the forward chassis strut of the revised Type 1 floats and 89 deg. 2 min. for the rear strut." (pp.111) Propulsion: 4xFINE pitch for take-off thrust of 13280 lbf@20 knots (pp.28) "Seven 'boats were fitted with 1B and M1 fuel systems, which had fuel tanks in the hull. Both systems had two 280 gal. tanks between Frames 15/16 and 20/21, installed on bearers over the centre cabin." (pp.65) "The five S.30 aircraft with M1 fuel systems - ... had the additional smaller top-up tank installed forward of the spar on the port side of the control deck. The feed pump for the top-up tank was a 24 volt Rotax C 1401, switched with a Rotax N5 HU switch through a 20 amp. Rotax N5 EB fuse." (pp.65) "The Pegasus engine data plates were fixed on the port side panel below the fore and aft level. The information on the plates read: Take off 2475 rpm. maximum +4 1/4 lb. sq. in. Maximum rpm Boost. Cylinder temp. Oil temp.deg.C. Take off 2475 +4 1/4 235 for 15 min. ?? Climbing 2250 +2 1/2 235 80 Cruising 2250 +2 190 70 All out 2600 +2 235 90 Oil pressure maximum 80 lb./sq. in. 5 minutes minimum 5 lb./sq. in. " (pp.71) "The Pegasus XC was a 28.7 litre, civil-rated, medium supercharged, poppet-valved engine and equipped the S.23, S.33 'boats and one of the S.30 aircraft - 'KZ CATHAY. The Bristol Perseus XIIC was 24.9 litre, civil rated, medium supercharged, sleeve-valve engine and was fitted to the eight S.30 'boats. Both types of engine were geared down to turn the airscrew at half crankshaft speed, through Farman type reduction gearing." (pp.91) "Some of the S.23s and 'KZ CATHAY had their Pegasus XC engines exchanged for Pegasus XXII during their service on the Horseshoe route, during World War II. The XXII was rated at 753 kW. at 2 600 rev. per min. with +6 lb. sq. in. for take off." (pp.91) "The nett dry weight of a Pegasus XC engine on the sling, was 1081 lb. A Perseus XX engine was slightly heavier." (pp.94) "The Bristol Pegasus XC engines of the standard S.23 aircraft were fitted with Robertson Type RH529 oil coolers and single 13 gals oil tanks. An alternative type of oil cooler with a greater throughput, the Robertson Type RH5-43, was fitted to some of the later boats and it is probable that all the S.30 'boats with the Perseus sleeve valve engines were fitted with these coolers'." (pp.101) "The following oil systems were used: System Oil tank capacity No. of Total capacity Standard S.23 13 1/2 gals. 4 54gals. 'UT CENTAURUS & 22 gals. 4 88 gals. 'UU CAVALIER Medium range 13 1/2 gals. 8 108 gals. Long range 18 gals. 8 144 gals. Long range 22 gals. 4 88 gals. Perseus 21 1/2 gals. 4 86 gals. " (pp.102) "The weight of the pair of mid-position tanks and associated pipework for a 1D system was 249 lb." (pp.103) Diagram over fuel system configurations. (pp.104) "The airscrews fitted initially to all the 'boats were de Havilland 5000 series 2 position variable pitch units of 12 ft. 9 ins. diameter with a pitch of approximately 14ft. The prepared and balanced airscrews, each weighing 365 lb. ..." (pp.112) "The Pegasus engined 'boats had two position airscrews. The Perseus engined 'boats were fitted with constant speed units. By 1943, the two TEAL 'A' 'boats had been fitted with fully-feathering de Havilland Hydromatic constant speed airscrews - the only Empire 'boats to be so equipped." (pp.112) Handling: "There was no change of trim to the aircraft as the flaps were moving OUT or IN, nor at the three most commonly used flap settings of 8 deg., 12 deg. and 25 deg. The extended flap at any setting did not interfere with the efficiency of the elevators and the drag was low." (pp.30) "The rudder bars had a movement of 22 1/2 deg. each way and were adjustable 2 1/2 ins. forward and 2 3/8 ins. aft, by turning a star wheel between the pedals. The rudder bars were linked together with a tubular connecting rod under the floor.J= Internal layout "The Captain occupied the port side pilot's seat with the First Officer beside him to starboard. The wireless station was immediately behind the Captain. The control deck stretched from Frame 3 - the forward point of windscreen of the coup, - aft to the forward spar frame at Frames 15/16 - a distance of about 23 ft." (pp.32) Diagram (pp.35-36) "The S.30 - except 'CT CHAMPION - and S.33 'boats ... were fitted with an observation (astro) dome. The dome was offset from the centreline to starboard, just aft of Frame 10. The dome was 21 inches in diameter and was alleged to be several inches too small for taking sights with a Mk. 12 sextant. The dome could also be used as an escape hatch." (pp.68) "Opposite the direction finding loop on the starboard side was a folding chart table with port hole over. A 6 watt light was provided over the table." (pp.68) Cockpit photos. (pp.??,70) "The hand wheel, which was devoid of switches, had a turn of 87 deg. each way and the column a fore-and-aft movement of 15 deg. 40 min. each way, the neutral position being vertical." (pp.70) "The centre panel of the dashboard, immediately over the throttle box, contained the controls for the automatic pilots. The pilot's main instrument panel, the dashboard, was just forward of Frame 4. The port side panel of the dashboard on the Captain's side, contained the following instruments: - 3 1/4 in. (82.5 mm.) K.B.B. Kollsman sensitive altimeter. - 2 1/2 in. (63.5 mm.) Sperry gyro compass. - 3.5 in. (89 mm.) Sperry artificial horizon. - Smiths AV 875 fore and aft level. - 3? in. (95.25 mm.) Smiths AV 549 air speed indicator (miles per hour). - Turn and bank indicator. - Rate of climb indicator. - Trip clock. The Type PL 4 compass was immediately aft of the panel, on the extreme left hand side. Compasses were Smith PL 4s, Hughes P/4/11s, or Kelvin Bottomly and Laird KBB 4s." (pp.70-71) "The starboard side panel of the dashboard on the First Officer's side, for 'boats with Sperry automatic pilot, contained the following instruments: - Four 2.12 in. (54 mm.) oil pressure gauges (one for each engine). - Two Record Cirscale engine speed indicators (one for each pair of engines, port and starboard). - Smiths turn and bank indicator. - 3? in. (95.25 mm.) Smiths AV 549 air speed indicator (miles per hour). - 3? in. (95.25 mm.) Smiths AV 567 static altimeter. - Two boost gauges (port and starboard engine pairs) and two engine selector cocks. Later aircraft were fitted with a boost gauge for each individual engine." (pp.71) "The First Officer's compass was of a similar type and in a similar position to the Captain's compass." (pp.72) "The centre panel of the dashboard, immediately over the throttle box, contained the control panel for which ever type of automatic pilot was fitted to the 'boat - Sperry Gyropilots all the 'boats with the exception of the three S.30 'A' 'boats, which were equipped with Smith Mark 1A automatic pilots. The Sperry control unit comprised the directional gyro unit, the bank and climb gyro unit and the vacuum gauge. The engaging lever was a Bowden double pull lever, located above the airscrew pitch control levers on the rear of the throttle box. With the lever to port the system was OFF. Moved over to starboard, the system was ON. The Sperry speed valves and oil pressure gauge - graduated from 0 to 300 lb. per sq. in. - were mounted on the port side of the control deck, immediately forward of the bow searchlight controls. The three speed valves were graduated from 0 to 6. ... The differential pressure gauge, the course change cock Type II, the azimuth control cock, the 5C/543 ON/OFF cut-out switch and the 5C/540 push switch re-setting button of the Smith Mark 1A automatic pilot equipment, were mounted on the centre panel of the dashboard. The pitch control lever was fitted to the port side of the throttle box. The dial plate was marked in degrees - UP 0 to 5 DOWN 0 5 10 - and operated in the normal sense of the controls. The lateral trim lever was on the Captain's panel of the dashboard. The dial plate was marked _ RIGHT WING UP LATERAL TRIM LEFT WING UP _ - the lever operating in the normal sense of the controls. The safety catch lever, which was fitted to the throttle box on the starboard side, operated the safety catches on all three units, to provide a complete and instantaneous mechanical disconnection of the automatic pilot in cases of emergency. The lever had two positions, IN and OUT, with a ratchet to allow the catches to be left disengaged. The main control cock was a three position cock - OUT, SPIN GYRO and IN controlled by a handle and mounted on the throttle box, probably in a similar position to the Sperry control lever. The remainder of the equipment, the test cock, the air filter and non-return valve, the air throttle Mk. 1, the oil reservoir and automatic valve Mk. IV were mounted on the starboard side of the control deck, possibly aft of the temperature gauge panel." (pp.72) "First Officer's Panel: - Sperry directional gyro. - Sperry artificial horizon. - Turn indicator. " (pp.72) "The switches and pilot lights for the instrument heaters and pressure head heaters on the instrument lighting panel or sub-board on the Captain's side of the dashboard." (pp.72) "The airscrew pitch controls were at the aft end of the throttle box, below the Sperry automatic pilot lever, near the floor. For the 'boats with Pegasus engines, the airscrews were controlled by a two position lever - RED knobs for port engines and GREEN knobs for starboard engines - operating a cable and pulley arrangement. The lever position for COARSE was UP, FINE pitch was DOWN. For the S.30 'boats with Perseus engines, Exactor units were used for the pitch controls. The control operating positions were in a similar position as those on the Pegasus engined 'boats. The position to increase revolutions was UP and decrease was DOWN. The two engine cut-out control levers were mounted either side of the throttle box. The two inner engines were controlled by the port side lever, while the starboard lever controlled the two outer engines." (pp.72) "The controls for the retractable bow 'landing (sic) searchlight' were mounted just below the windscreen coaming on the Captain's side at Frame 5. The dual Teleflex remote control levers moved the light IN/OUT and UP/DOWN." (pp.73) "The temperature gauge panel was situated behind the First Officer's right shoulder, on the starboard side of the aircraft, between Frames 6 and 7. This panel carried the following instruments for Pegasus engined aircraft with Sperry automatic pilots: - Weston Pyrometer Model 602 HJ 509 engine cylinder-head temperature indicator 0 to 350 deg. C - with a Weston four-way rotary switch. ... - Four 2.12 in. (54 mm.) oil temperature gauges - one for each engine. - Four 2.12 in. (54 mm.) carburettor air intake thermometers - one for each engine. - Vacuum distributor, gauge, adjuster and control cocks for the Sperry automatic pilot connected to the Romec vacuum pumps on the two starboard engines. The arrangement of this panel for the Perseus engined S.30 aircraft with the Smith's automatic pilots - the 'A' 'boats - is assumed to have been similar." (pp.73) "Fitted above the automatic pilot panel were the engine ignition switches and the starter buttons. The four Rotax N5 CD engine starter buttons were on the top of the panel, protected by a flip-up cover. ... The ignition switches were flush-mounted Lundberg twin knob switch units. Each of the two magnetos on an engine was controlled by a switch knob, yoked together in pairs for port and starboard." (pp.73) "The throttle box, between the pilots, was a light alloy casting slotted for the levers of the throttle, mixture and airscrew pitch controls. Port control levers were topped with RED knobs and those for the starboard levers GREEN knobs. The lettering, indicating the settings for the levers, was cast directly into the top surface of the box. For the throttle, OPEN was forward and SHUT to the rear. For the mixture control, FULL WEAK was forward, NORMAL to the rear, then through the gate to RICH, in the full aft position. The mixture controls were fitted with a yoke, with adjusting screws for individual levers, enabling the levers to be moved together." (pp.74) "The lateral trim control was on the instrument panel on the Captain's side below the rate of climb indicator." (pp.74) "The bulkhead forming the aft end of the control deck was the forward main spar frame - Frames 15/16." (pp.74) "The fuel tank cocks were attached to the roof of the control deck at the aft end, just forward of the main spar frame bulkhead." (pp.74)