A.Jackson Blackburn Aircraft since 1909 (Putnam)
Although Robert Blackburn had made a valuable contribution to the war effort by building large numbers of B.E.2c biplanes and had been awarded sizeable contracts for Sopwith Baby seaplanes and Sopwith Cuckoo single-seat torpedo-bombers, it was well known that his real interest lay in the construction of naval aeroplanes of Blackburn design. Opportunity was not long delayed, for, despite the excellence of the Cuckoo as an aeroplane, its 1,086 lb Mk IX torpedo was not capable of sinking a large warship. Thus, in the autumn of 1917, the Admiralty formulated a requirement for a generally similar singleseater capable of carrying the large Mk VIII torpedo weighing 1,423 lb and mounting a warhead 50 per cent more powerful than that of the Mk IX. Details were set out in Specification N.1B (Torpedo-Carrying Ship Aeroplane), but when the RNAS lost its separate identity in April 1918 the N.1B aeroplanes were restyled Type XXII in the new RAF system of numbering by functional category.
Contracts were placed in February 1918 for six Rolls-Royce Eagle VIII powered prototype aircraft, three from Short Bros Ltd which were given the name Short Shirl and numbered N110-N112, and three others N113-N115 from the Blackburn Aeroplane and Motor Co Ltd for which Robert Blackburn created the name Blackburd simply by changing the last letter of his surname. As stated in a previous chapter on the little Blackburn single-seat flyingboat, N.1B aircraft were all single-seat bombers, but as this category also included torpedo aircraft, the Shirl and the Blackburd came within it.
Competitive trials were to decide which of the two types was to be built in quantity, but so determined were Blackburns to secure a production contract and to establish themselves as specialists in naval aircraft, that they supplied these prototypes at ?2,200 each, or approximately two-thirds of the actual cost.
Designed by Harris Booth and intended eventually for shipboard service on Britain's first aircraft carrier Argus, commissioned in September 1918, the Blackburd was a large, three-bay, unstaggered biplane with folding wings, conceived on the simplest possible lines for cheap and rapid production. For this reason the mainplanes were of constant chord and uniform section throughout so that if the Blackburd were ordered in quantity they could, like those of the D.H.6, be 'made by the mile and cut off by the yard'. They retained the wire trailing edges of the S.P. and Kangaroo machines and were built up from rectangular-section box spars and ribs of spruce three-ply, braced with steel tie rods. The same principle was applied to the design of the square-section fuselage which was built around four rectangular spruce box longerons. It maintained a constant depth from nose to tail and was thus little more than a flying box under which the torpedo was carried in steel crutches. Although the strength weight ratio was unusually good, it is doubtful whether the fuselage could, in fact, have been produced quickly as the work of building up the struts and box longerons was considerable, particularly as the latter tapered towards the rear.
Lateral control was by four interconnected long-span ailerons which could all be lowered to act as flaps for shortening the take-off run, but the pilot only had positive control over them in a downward direction, the upward movement being effected by the dashpot-controlled tension of bungee rubber cord anchored to the rear spar of the wing.
A single 350 hp Rolls-Royce Eagle VIII water-cooled engine on a tubular-steel mounting drove a two-bladed left-hand tractor wooden airscrew and was equipped with doper and hand starter which made it possible to despatch the Blackburd within 15 min of an alert. Fuel was pumped from a 74-gallon tank in the second bay of the fuselage, and a 9-gallon oil tank was fitted crosswise some 2 ft behind the engine.
Tubular-steel interplane and undercarriage struts were streamlined with an exceptionally light, if complicated, fairing built up of fabric doped over three-ply formers linked by wires and secured to metal clips soldered to the main tube. Weight saving over the usual spruce fairings was estimated as 120 lb. The enormous undercarriage was built in the form of a pin-jointed parallelogram with stout diagonal main legs incorporating solid rubber shock absorbers, the shock legs projecting vertically below the inboard interplane struts and carrying short steel skids of Warren truss construction at their lower ends. The 900 x 200 mm pneumatic wheels and their transverse axle weighing 70 lb had to be jettisoned before the torpedo could be dropped, and on its return to the carrier the Blackburd was expected to make a deck landing on the skids. This was not so hazardous a procedure as it would appear, much preparatory work having been done with skid-equipped Sopwith Pups and 1 1/2 Strutters at the Marine Experimental Aircraft Depot, Isle of Grain.
Ability to jettison the wheels was, of course, a distinct advantage if the pilot were faced with the necessity of making a forced landing at sea, the risk of nosing over being greatly reduced. Ditching characteristics on the third Blackburd prototype, N115, were further improved by increasing the chord of the front undercarriage struts so that they acted as mountings for multiple hydrofoils, an additional pair being fixed to the skids. Flotation gear in the form of inflatable air bags was carried in the fuselage.
The pilot's cockpit was situated 9 ft behind the centre section and approximately half-way between the trailing edge of the mainplane and the leading edge of the tailplane, a remote position from which forward view must have been negligible, and the fuselage was so wide that he had difficulty in looking over the side. Control was by a wooden rudder-bar and a stick-mounted aileron wheel which projected out of the cockpit in true pre-1914 manner. The pilot sat in a large wicker seat protected from the slipstream by a fairing of doped fabric surmounted by a small Triplex wind screen. No guns were carried and the aircraft was armed solely with the torpedo.
Delivery of the first Blackburd, N113, was scheduled for 6 May 1918 but, after the engine had been installed, the men were taken off it to rush out the first few Cuckoos but even so it was finished by the end of the month. R. W. Kenworthy, Blackburn's chief test pilot, then flew it on a series of trials in which the wheels and a dummy torpedo were dropped repeatedly into the River Humber to be picked up by motor boat. The aircraft then returned to Brough to make its fearsome skid landing. The skids were modified a number of times but according to Kenworthy the landings went off fairly satisfactorily, the 'feel' to the pilot being similar to landing a seaplane. He flew it south to the Aeroplane Experimental Station at Martlesham Heath on 4 June 1918 for official performance trials, beating the first Short Shirl, N110 (delivered by John Lankester Parker), by several days.
In Report M.208 dated 21 June 1918, the Blackburd's combined aileron and flap system was criticized on the grounds that if the flaps were down for take-off the machine was without ailerons and therefore uncontrollable laterally. Their effectiveness was proven, however, when the fully-loaded Blackburd unstuck in less than one-third of the distance required without flaps.
Flight testing showed that the Blackburd was only stable laterally, and the Report went on to say that it was excessively nose heavy in climbing, gliding and level flight, both with and without torpedo, and that it was '...only possible to fly for any length of time by relieving the pilot of the continuous elevator load by means of "sandow" (bungee rubber) on the control stick'. In gusts and bumps, rudder area was inadequate; and while landing, the rudder became ineffective as flying speed was lost, making it difficult to keep the aircraft into wind during slow landings, and impossible to taxy in winds of more than 8 mph. When the trials were almost complete, Blackburd N113 crashed, and some of the tests, including flapped take-off distance measurements with varying loads, were never completed. Comment was made, however, on the excellent way in which the tubular engine mounting, the fuel tank and all the joints in the wooden structure stood up to the impact.
The second Blackburd, N114, was doped silver overall, and although first flown without them, was delivered with small wing tip floats bolted to the underside of the lower mainplane below the outboard interplane struts. It also had a large rectangular tropical radiator of the type fitted later to the special long-distance Blackburn Kangaroos. As a result of recommendations made after the Martlesham trials with N113 , the tail unit was redesigned, strengthened internally, fitted with improved rudder and elevator hinges and a larger rudder, having the trailing edge in the form of a smooth curve instead of in vertical scalloping. To prevent deflection of the tailplane under load (which by altering the incidence had probably affected fore and aft control on N113), twin bracing cables were anchored to both front and rear spars. Take-off flaps were retained but were controlled separately from the ailerons.
On completion in mid-August 1918, N114 was flown straight to the RAF station at East Fortune, Scotland, for torpedo trials, but it later returned to Brough for servicing before being flown to Martlesham Heath on 16 October for full performance testing. Performance measurements with and without torpedo were completed by 9 November, but a week later manoeuvrability trials were temporarily suspended to permit a detailed examination of the fuselage structure. The third Blackburd, N115, completed in November 1918, was sent from Brough to the Development Squadron at Gosport. N114 was also posted to the strength of this squadron but was dismantled and sent to Devonport to be held as spares for N115. The latter was certainly serviceable at Gosport on 10 May 1919, and it later operated experimentally from Argus in the Mediterranean.
R. W. Kenworthy recalled how a second cockpit was made over the C.G. of a Blackburd - it could only have been N115 - and how he flew with Lady Mary Savile as passenger from Gosport to Hounslow en route for Brough but forced landed on the golf course at Hurst Park. This aeroplane was also to have been used by Miss Florence Parbery, the singer, for airborne Marconi wireless tests at the Hague, but she eventually made them at Croydon Airport in a Westland Limousine piloted by A. F. Muir on 12 January 1922.
As the Shirl's performance was marginally better than that of the Blackburd, an order was placed with Blackburns for 100 Shirls, but this was cancelled soon afterwards in favour of additional Sopwith Cuckoos which were better able to take evasive action after launching their torpedoes. Nevertheless, despite the brevity of their careers, the three Blackburd prototypes served to renew and strengthen the Blackburn company's link with the Royal Navy, first forged with the Type L four years previously.
SPECIFICATION AND DATA
Manufacturers: The Blackburn Aeroplane and Motor Co Ltd, Olympia Works, Roundhay Road, Leeds, and Brough Aerodrome, East Yorks.
Power Plant: One 350 hp Rolls-Royce Eagle VIII
Span (extended) 52 ft 5 in (folded) 17 ft 1 in
Length 34 ft 10 in Height 12 ft 41 in
Wing area 684 sq ft
Pilot 180 lb Tare weight 3,228 lb
Mk VIII torpedo 1,400 lb Military load 1,8511b
Torpedo gear 50 lb Fuel 74 gallons 534 lb
Equipment 221 lb Oil 9 gallons 87 lb
Military load 1,851 lb All-up weight 5,700 lb
Without torpedo With torpedo
Speed at 6,500 ft 95 mph 90.5 mph
Speed at 10,000 ft 94.5 mph 84.5 mph
Speed at 16,500 ft 87 mph -
Initial climb 845 ft min 505 ft min
Climb at 5,000 ft 685 ft min 345 ft min
Climb at 10,000 ft 480 ft min 140 ft min
Maximum height reached 17,000 ft 11,000 ft
Time to max. height 37 min 15 sec 41 min 45 sec
Climb at max. height 195 ft min 100 ft min
Absolute ceiling 21,500 ft 13,000 ft
Endurance 3 hr 3 hr
Three prototype aircraft only as follows:
N113 Completed May 1918, flown to Martlesham 4 June 1918, crashed at Martlesham on or about 2 July 1918.
N114 Completed August 1918, to East Fortune, September 1918, flown to Martlesham 16 October 1918, dismantled and sent to Devonport as spares on or about 7 December 1918.
N115 Completed November 1918, to the Development Squadron, Gosport; temporary two-seater later.
F.Manson British Bomber Since 1914 (Putnam)
The incorrigible Harris Booth was nothing if not unorthodox in his approach to aircraft design, and in long retrospect it must be wondered at Robert Blackburn's wisdom in entrusting the design of his N.1B tender to someone whose previous essays could only be described as quaint, bordering on the grotesque. (The Blackburn G.P. seaplane had been designed by Bob Copley) After all, Blackburn had for several years been anxious to perpetuate a favoured working relationship with the Admiralty and, with orders for the Sopwith Cuckoo already in hand, it must have seemed encouraging that Blackburn should be asked to tender the design of a possible Cuckoo replacement.
If the Short Shirl appeared as a straightforward, conventional approach to the N.1B requirement, Booth's creation was little more than a vehicle in which he let his fertile imagination run riot. The Blackburd was a three-bay biplane whose wings, of almost equal span and of parallel chord without sweepback, were rigged without stagger. The fuselage consisted of a rectangular-section box of uniform depth from nose to tail, but built-up on four tapering spruce box longerons. Four long-span ailerons could be partially lowered to reduce take-off run and landing speed; however, not being double-acting when lowered, they thus deprived the pilot of all lateral control. The pilot's cockpit was situated only seven feet forward of the fin, with seventeen feet of fuselage forward of the windscreen; vision from the cockpit must have been minimal.
Perhaps the most extraordinary feature of the Blackburd was the manner in which the interplane, centresection and undercarriage steel tubular struts were faired to aerofoil section, using doped fabric on ply formers, linked together by wire and secured by metal clips to the steel tubes.
The hefty undercarriage comprised twin parallelogram structures of steel struts, pin-jointed together, each structure carrying a single wheel and a short steel skid built as a Warren truss. The wheels, with their cross-axle, had to be jettisoned prior to dropping the Mark VIII torpedo, so the pilot was obliged to make a deck landing on the skids when operating from a carrier.
The first Blackburd, N113, was flown by R W Kenworthy in May 1918, and was delivered to Martlesham on 4 June for preliminary performance and handling trials. Here it was unfavourably received on account of longitudinal and directional instability, with excessive nose-heaviness in almost every flight regime, whether carrying the torpedo or not. Indeed, the rudder was virtually useless during landing - a fatal flaw in a deck-landing aeroplane. The aircraft crashed before the trials were completed.
N114, with an enlarged rudder and a deepened frontal radiator, was not flown until mid-August, and went immediately to East Fortune for torpedo trials. These were completed in November, but the subsequent handling trials were curtailed when the aeroplane was grounded pending an examination of the fuselage structure. It was never flown again, and was disposed of for spares.
The third Blackburd, N115, was probably flown in November but, as with the Shirl, interest in the aircraft had waned. It was, however, delivered to the Gosport Development Squadron, and later flew trials aboard HMS Argus in the Mediterranean.
By inference, the Blackburd was rated as inferior to the Shirl, but there was irony in the fact that Blackburn was awarded a production contract to build 100 Shirls, only for this to be cancelled almost immediately - and replaced by an order for a further 100 Sopwith Cuckoos!
Type: Single-engine, single-seat, three-bay biplane shipborne torpedo-bomber.
Air Ministry Specification: N.1B (later Type XXII)
Manufacturer: The Blackburn Aeroplane and Motor Co Ltd, Olympia Works, Leeds.
Powerplant: One 350hp Rolls-Royce Eagle VIII 12-cylinder water-cooled in-line engine.
Structure: Composite wood and steel construction, comprising spruce-ply box longerons and wing spars, distanced and braced with steel tie rods.
Dimensions: Span, 52ft 5in (wings folded, 17ft 1in); length, 34ft 10in; height, 12ft 4 1/2in; wing area, 684 sq ft.
Weights: Tare, 3,228 lb; all-up (with torpedo), 5,700 lb.
Performance (with torpedo): Max speed, 90.5 mph at 6,500ft; climb to 6,500ft, 16 min 15 sec; service ceiling, 11,000ft; endurance, 3 hr.
Armament: No gun armament. Provision for one 1,423 lb Admiralty Type VIII torpedo, capable of being dropped only after jettisoning landing wheels and cross-axle.
Prototypes: Three, N113-N115. N113 first flown by R W Kenworthy at Brough at the end of May 1918. No production.
H.King Armament of British Aircraft (Putnam)
Blackburd. Like its counterpart the Short Shirl, the Blackburd was a single-seat deck-landing torpedo-carrier (not 'torpedo-bomber', for that requirement came later), designed for the 18-in Mk.VIII torpedo weighing 1.423 lb. (The 18-in Mk.IX, as carried by the Blackburn-built Sopwith Cuckoo, weighed about 1.000 lb.) A makers' description mentioned controls in the cockpit to adjust the mechanism of the torpedo in the air and the weight of the 'torpedo gear' was listed as 50 lb. The torpedo was carried parallel to the fuselage centre line; and the centre line was parallel to the top and bottom lines. 'It was like a flying box,' recalled G. E. Petty, who was responsible for several Blackburn torpedo aircraft, but he saw fit to add: 'The only excuse was that by then production was of primary importance, and Harris Booth eliminated all trimming.'
That the Blackburd was a more remarkable aeroplane than has hitherto been apparent, and not respecting armament alone, is evident from the following contemporary account, which affords a classic example of how a new form of armament and a new technique of operation could influence aircraft design:
'As the run on a ship is necessarily very limited, the machine must be capable of getting off at a comparatively low speed, or, in other words, the lift component of the reaction on the wing section must be a maximum. In the "Blackburd" aeroplane this is obtained by the use of wing flaps, which are pulled down before flight, and consequently alter the wing section to one of deep camber and high maximum lifting capacity. When once off the deck the flaps are released and automatically resume their normal position. To prevent any instability, which might be caused by a too sudden change of section, a specially-constructed oil dashpot is used, which allows the flaps to assume the neutral position gradually. In practice the time taken for this operation is about 43 seconds.
'For getting off the deck wheels arc fitted, but when once off, these, together with their axle, are dropped by means of a lever which also actuates the dashpot. By releasing the wheels, two long skeleton steel skids are left clear for use in case of landing again on the deck, and if it is inevitable that the machine should alight on the water, these skids have not the "tripping" effect that wheels possess. Once in the water, the machine is kept afloat by means of air bags fitted inside the fuselage and in the bottom of the engine cowl. Another interesting feature of this skid chassis is the arrangement of the springing gear. This consists of two vertical telescopic compression struts, which, when compressed, cause the skid to move slightly forward, with the result that when landing, the machine appears to creep forward, first on one skid and then on the other. Attached to the front tubes of the chassis arc timber hydrovanes, one above the other, and the reaction of the water on these when alighting keeps the nose of the machine up and counteracts any tripping effect.
'The torpedo is held in position by means of two sets of crutches and one adjustable tension strap round the torpedo itself. In order to prevent the torpedo from moving fore and aft, a raised stop on the top of the torpedo fits into a fixed steel block on the under side of the fuselage. The control for dropping the torpedo is very ingenious, and at the same time fool proof. A long-handled wooden lever is pulled into the rear position before flight and fixed there by means of spring plungers. Immediately after rising, the pilot pushes the lever forward and releases, by this one operation, both the wheels and axle, and the wing flaps previously mentioned. Now suppose the pilot wishes to drop the torpedo, he pulls back the lever into its original position and, by doing so, releases the two ends of the torpedo strap simultaneously, and starts the motor in the torpedo itself. When one considers that each control usually means a separate lever, and that the average torpedo-plane pilot has at least 15 different controls to operate, it is evidently a great boon to have four worked by one lever. Another advantage of this gear is that the torpedo cannot be released until the wheels and axle have been dropped clear.'
The Blackburd carried no guns.
Jane's All The World Aircraft 1919
This machine, designed as a torpedo carrier for use from aeroplane carriers working with the fleet at sea, was designed primarily with a view to ease of production.
The machine is generally on conventional tractor lines, with a chassis designed to allow of the dropping of a torpedo slung beneath the body.
The most noticeable feature, as far as appearance is concerned, is the side elevation of the fuselage, which is of the same depth from the leading edge of the lower wing to the sternpost.
Type of machine Tractor Biplane.
Name or type No. of machine "Blackburd."
Purpose for which intended Torpedo carrier, for use from ship or land.
Span 52 ft. 6 in.
Overall length 36 ft. 3 in.
Maximum height 12ft. 4 1/2 in.
Chord 7 ft.
Total surface of wings 709 sq. ft.
Span of tail 17 ft.
Total area of Tail 82 sq. ft.
Area of elevators 34 sq. ft.
Area of rudder 9 sq. ft.
Area of fin 18 sq. ft.
Area of ailerons 85 sq. ft.
Maximum cross section of body 11 sq. ft.
Horizontal area of body 80 sq. ft.
Vertical area of body 126 sq ft.
Engine type and h.p. "Eagle" Rolls-Royce; 350 h.p.
Weight of machine empty 3,080 lbs.
Load per sq. ft. 7.53 lbs.
Weight per h.p. 15.8 lbs.
Tank capacity in hours 3 hours.
Tank capacity in gallons 69 petrol; 9 oil.
Speed low down 92 m.p.h.
Speed at 10.000 feet 84 1/2 m.p.h. Climb.
To 5,000 feet in minutes 11 1/2 minutes.
To 10,000 feet in minutes 33 1/2 minutes.
Disposable load apart from fuel 1,680 lbs.
Total weight of machine loaded 5,340 lbs.
Flight, December 11, 1919.
THE BLACKBURN MACHINES.
The "Blackburd" Torpedo 'Plane.
This machine, it will be seen, is of rather unusual appearance, resulting from the special requirements for which she was designed. As the title indicates, the chief function of the "Blackburd" is that of dropping torpedoes, and, consequently, the lifting capacity of the machine has to be considerable, as the torpedo weighs over half a ton. Also, she is designed for use from a "mother" ship, and hence is of small dimensions when folded. The use from a ship entails starting from the deck and alighting, on the deck or on the sea as circumstances dictate. To this end the "Blackburd" has a special undercarriage, the wheels of which can be dropped after rising, leaving clear two long skids which can be used for landing on the deck after the torpedo has been discharged. If, on the other hand, it becomes necessary to alight on the sea, the skids do not, we understand, have the same "tripping effect" as do wheels, and there is therefore less danger of the machine turning over on her nose. When in the water the machine is kept afloat by inflating air bags in the fuselage, which gives the necessary flotation to support the machine until she is "collected" by her mother ship.