O.Thetford, P.Gray German Aircraft of the First World War (Putnam)

Gotha G IV and G V

   The Gotha was without doubt the most legendary twin-engined bomber of the First World War. The name came to be applied generically (and inaccurately) to all large enemy aircraft, in much the same way that "Handley Page" was applied to all and sundry Allied twin-engine machines. It was largely through the use of the Gotha in daylight raids on Great Britain that these aircraft became so widely publicized and were mentioned only with apprehension. The Gotha G.IV and G.V became the main production variants, having been developed from the earlier G 11 series of 1916, which were produced only in small numbers. The G.IV and G.V were manufactured by both the parent firm and sundry sub-contractors.
   Together with the Friedrichshafen G.III, the Gothas shared the brunt of the long-range bombing attacks from 1917 onwards. An outstanding feature of the G.IV and G.V was the "sting in the tail" whereby the rear gunner was able to fire not only upwards and backwards but downwards too, through a specially designed "tunnel" in the fuselage bottom. This firing position had been tried in the earlier Gotha G.III, but the gun had to be operated by the gunner adopting a prone position and firing through a trapdoor in the fuselage bottom. In the G.IV and G.V the plywood-lined tunnel was aligned with a V-shaped opening in the top decking so that the gun, on a normal mounting, could be sighted and fired through the fuselage, backwards and downwards, through an arc of 25 deg. laterally and 60 deg. vertically, although a prone position could also be adopted. Considerable toll was taken of Allied machines until effective evasive tactics had been evolved.
   Apart from this novel firing arrangement, the Gotha G.IV and G.V were quite conventional airframes, and the fuselage, unlike the contemporary Friedrichshafen G.III, was a one-piece wooden structure of spruce longerons and spacers. Although completely plywood-skinned, the basic structure was still braced in all bays with stranded steel cables. A gunner's cockpit was situated in the extreme nose, immediately aft of which sat the pilot on the port side of the fuselage. Beside him was arranged a folding seat for another crew member. Between the pilot's cockpit aft of the wings were located the main fuel tanks, which occupied the full width of the fuselage, preventing any interchange of crew positions in flight. Bulkheads were cut away extensively, however, which points to the fact that initially the design had intended inter-communication.
   Of three-bay layout, the upper wings were composed of two panels joined at the center with steel wedges securing interlocking rectangular staples. The lower wings had a center-section portion to which were attached the engine bearers, struts and undercarriage chassis, each side being an independent and separate unit. These sections were plywood-covered on both surfaces. Based on two spruce main-spars of channelled I-section, additionally walled with 4 mm. birch ply and fabric wrapped, the fabric covered wings were swept throughout their length at an angle of 4 deg. Ribs of ply, extensively fretted for lightening purposes, were flanged with solid timber and tacked to the spars. All interplane struts were of steel tube with three-ply fairings attached. Inboard the trailing edges of the wings were all cut back to allow airscrew clearance for the pusher-arranged twin 260 h.p. Mercedes D.IVa engines. Ailerons of welded steel tube were fitted to all four wingtips, those on the upper wing having a large horn balance. They were linked with a strut and actuated by a crank lever attached to the top ailerons.
   The complete empennage was fabricated from light-gauge steel tube and fabric covered. Only the rudder was balanced, and its size, compared with the fin, was considerable. Streamlined steel-tube struts rigidly braced the components to the fuselage.
   Each separate undercarriage chassis was fitted with two wheels which were attached to the main axle and sprung with long tension springs, unusually mounted inside the main struts. In the Gotha G.Vb a front pair of wheels was added to each chassis, forming an auxiliary attachment to facilitate night landings and prevent nosing over. An extremely rugged tailskid with steel reinforcing spine and shoe completed the undercarriage gear.
   Bombs were stowed externally on removable racks, and were arranged and fitted according to their size and the requirements of the operation.
   The emergence of the Gotha G.IV in the autumn of 1916 coincided with a realization of the Zeppelin airship's limitations as a raiding weapon, and it made the aeroplane bombing raids on England, for which the "Ostend Carrier-Pigeon" Squadron had been formed as early as November 1914, a practical possibility. Thirty Gotha G.IVs were issued to Heavy Bomber Squadron No. 3, commanded by Hauptmann Brandenburg, in the spring of 1917. They were based at St. Denis Westrem (Flights 13 and 14) and Gontrode (Flights 15 and 16). Two more flights (Nos. 17 and 18) were added in July 1917.
   In the daylight raids on England (25th May to 22nd August 1917) the Gothas achieved a remarkable degree of success with, initially, a surprisingly low casualty rate. The reason for this was two-fold. The Gotha's excellent 260 h.p. Mercedes engines enabled it to operate in the region of 15,000 ft. and, as the English defenses lacked adequate early warning facilities, was able to approach and release its bombs before Home defense aircraft could attain the same altitude. By the time such fighters as were then available (modified B.E., Sopwith Pups, Martinsydes, etc.) had laboriously clambered to their ceilings, the raiding aircraft were well on their way back across the North Sea. No significant material damage was achieved, but the effect on the public was such that the Government was forced to withdraw operational fighter squadrons from France, including the famous No. 56 Squadron, to combat the daylight raids. With the subsequent improvement of the warning system and the advent of the Bristol Fighter and Sopwith Camel defense units, daylight raids became impossible without disproportionate losses and the Gothas reverted to night raids from 3rd September 1917 onwards. The night attacks ended in May 1918. Altogether, the Gothas of Bombengeschwader 3 dropped 84,745 kg. of bombs on England in twenty-two raids. Twenty-four Gothas were destroyed by Allied defenses and a further thirty-seven lost in accidents.
   Capt. J. B. McCudden, V.C., had a brush with the daylight raiders while serving as an instructor at Joyce Green: strangely enough, it was on 5th July 1917, the day after No. 56 Squadron had returned to France. McCudden had his unarmed instructional Sopwith Pup fitted with a Lewis gun to fire over the airscrew and the under-surfaces of his aircraft painted blue to render it less visible should he be able to get above the Gothas to put in an attack. The warning came about 10 a.m., and McCudden immediately took off and climbed towards the south of the Thames, ultimately arriving over Southend at some 16,000 ft. Flying west along the estuary, attracted by A.A. bursts, he saw some twenty bombers in good formation returning east. Having altitude to spare, he waited for the formation to pass before diving on the rearmost machine firing a complete drum of forty-seven rounds. Misjudging the dive, McCudden had to pull out to avoid the Gotha so suddenly as to break his seat bearers. Pulling up for another attack, he dived to within 300 ft. on the Gotha's starboard quarter, then suddenly changed over to his port rear, closing to 150 ft. and finishing another drum before the enemy gunner could swing his gun to the opposite side. However, neither attack produced any visible effect. Putting on his third and last drum, McCudden again repeated the maneuver of changing from side to side to disconcert the gunner, and this time saw his tracers striking about the fuselage and wings, but was disappointed to achieve no more effect than for the Gotha to shove down his nose a little. Now out of ammunition, he could do no more than fly alongside the bomber at a discreet distance, screened from enemy fire by the Gotha's own wings, in the hope of distracting the attention of the gunners so that some of the other defense machines that had now appeared on the scene might perhaps get in an attack. After 25 minutes his vigilance relaxed, and one of the enemy gunners put a good burst through McCudden's Pup, one bullet smashing the windscreen.
  
  
Description: Twin-engined long-range bomber. Crew of three.
Manufacturers: Gothaer Waggonfabrik A.G. Gotha (Go.).
Power Plant: Two 260 h.p. Mercedes D. IVa 6 cylinder in-line water-cooled engines.
Dimensions:
   Span 23.7 m. (77 ft. 9 1/4 in.)
   Length 11.86 m. (38 ft. 11 in.)
   Height 4.3 m. (14 ft 1 1/4 in.)
   Area 89.5 sq.m. (966.6 sq.ft.)
Weights:
   Empty 2,740 kg. (6,028 lb.)
   Loaded 3,975 kg. (8,745 lb.)
Performance:
   Max speed 140 km.h. (87.5 m.p.h.) at 12,000 ft.
   Climb to 3,000 m. 28 min.
   Ceiling 6,500 m. (21,320 ft.) in 52.5 min.
   Range 305 miles.
Armament: Two manually operated Parabellum machine-guns in nose and rear cockpits.
   Bomb load varied from 300 to 500 kg. (660 lb. to 1,100 lb.) to suit operational requirements.
   Six 50-kg. (110 lb.) bombs were usually carried in the daylight raids on England.
  

Gotha G Vb
   Towards the end of the G V production a modified version, the G Va with a compound tail assembly, was introduced, and this type was further modified, by the addition of extra landing wheels to the twin undercarriage chassis, into the G Vb. The type saw service during 1918 in limited numbers, and was the last of the Gotha "classic" twins. Engines, two 260 h.p. Mercedes D IVa. Span, 23.7 m. (77 ft. 9 1/4 in.). Length, 12.4 m. (40 ft. 8 1/4 in.) unconfirmed. Area, 89.5 sq.m. (967 sq.ft.). Weights: Empty, 2,950 kg. (6,490 lb.). Loaded,4,550kg.(10,010 lb.). Speed, 135km.hr.(84.35m.p.h.).

J.Herris Gotha Aircraft of WWI (A Centennial Perspective on Great War Airplanes 6)

Gotha G.V

   The Gotha G.V was a further refinement of the basic design. Experience had shown that housing the fuel tanks in the engine nacelles increased the chance of fire in the event of a crash. Therefore the fuel tanks of the G.V were moved to the fuselage away from the engines, which were enclosed in streamlined nacelles mounted between the wings. The engine remained the same 260 hp Mercedes D.IVa as used in the G.III and G.IV. Despite the nominal improvements incorporated into the G.V, the basic design had reached its peak. Furthermore, wartime shortages resulted in inferior materials being used to construct the G.V, making it heavier than the G.IV and reducing its performance. Additional equipment deemed necessary by operational experience aggravated the problem.
   Regardless, Idflieg ordered 100 G.V bombers on 19 October 1916. The G.V passed its type test in July 1917 and the first aircraft reached Bogohl 3 in August 1917. The G.V arrived too late to participate in the daylight raids over the UK but were used for night bombing, performing both strategic raids over the UK and tactical bombing on the Western Front.
   The Gotha G.Va was an attempt to improve flight safety. A re-designed 'box' tail with biplane horizontal stabilizers and elevators and twin fins and rudders improved engine-out controllability, even enabling turns into the running engine. A two-wheeled Stossfahrgestell mounted under the nose prevented nose-overs on landing to improve landing safety, the Gotha's Achilles Heel. The nose turret was also modified. Twenty-five of this transitional model were delivered.
   The G.Vb was derived from the G.Va in a further attempt to improve flight safety. The 'box' tail was retained and, to reduce the pilot's workload and improve maneuverability, most G.Vb bombers were equipped with Flettner servo controls on the upper ailerons. To further improve landing safety a four-wheeled undercarriage underneath each engine, similar to the original G.II prototype, was fitted. Unfortunately, the new undercarriage reduced the already compromised flight performance due to its greater weight and drag, and the Gotha G.Vb was inferior to the contemporary AEG G.V and
Friedrichshafen G.IV based on comparative tests by Idflieg. Confirming this assessment, Idflieg placed an order with Gotha to build 50 Friedrichshafen G.IVa(Go) bombers under license, although the war ended before any were built. Although 80 Gotha G.Vb bombers were completed, the final few were delivered postwar directly to the Allies as part of the Armistice conditions.

Gotha G.V Specifications
Engines: 2 x 260 hp Mercedes D.IVa
Wing: Span Upper 23.70 m
Span Lower 21.90 m
Area 89.5 m2
Chord Upper 2.30 m
Chord Lower 2.30 m
Gap 2.22 m
Sweepback 1.16°
General: Length 12.40 m
Height 4.30 m
Empty Weight 2413 kg
Loaded Weight 3648 kg
Maximum Speed: 140 km/h
Climb: 1000m 2.5 min
2000m 8.5 min
3000m 17 min
4000m 29 min
Range: 840 km


Gotha G-Type Bomber Production Summary
Order Date Type Qty Serials Notes
Oct. 19, 1916 G.V 20 664-683/16 Delivered Aug. 1917-April 1918
Oct. 19, 1916 G.V 80 900-979/16 Delivered Aug. 1917-March 1918
Oct. 15, 1917 G.Va 25 700-724/17 Delivered 3 Apr-22 May 1918
Oct. 15, 1917 G.Vb 25 725-749/17 Delivered 4 June-15 Aug. 1918
May 18, 1918 G.Vb 25 913-927/18 Delivered 30 June-6 Sep. 1918
July 26, 1918 G.Vb 15 1450-1464/18 Delivered 9 Sep.-2 Oct. 1918
Aug. 4, 1918 G.Vb 15 1778-1792/18 Delivered 18 Oct.-14 Dec. 1918

P.Grosz, G.Haddow, P.Shiemer Austro-Hungarian Army Aircraft of World War One (Flying Machines)

Gotha G.V and G.VII

  Idflieg offered the LFT five surplus Gotha G.V and 30 Gotha G.VII twin-engined bombers, less engines, as dual-control trainers in August 1918. Perhaps unknown to the LFT was the fact that, after much experimentation, the Gotha G.VII bomber proved a disappointing failure because it was unable to reach the specified operational altitude of 6000 meters (19,685 ft). This made it unsuitable for the day bomber and long-range reconnaissance role for which it had been designed. Uzelac declined the offer on grounds of "the poor service record experienced with the 40 Gotha G.IV(LVG) bombers in spite of having reinforced the airframe."

Журнал Flight

Flight, November 14, 1918.

THE GOTHA BOMBER
WITH NOTES ON GIANT AEROPLANES

[Issued by Technical Department (Aircraft Production), Ministry of Munitions.]

   THIS machine is now on view at the Enemy Aircraft View Room, Agricultural Hall, Islington. Passes can be obtained upon application to Ap. D. (L.), Pen Corner House, Kingsway, W.C.2.
   The standard type of two-engine Gotha is a pusher, the appearance of which is characterised by the backward sweep of the main planes, which are also set at a lateral dihedral angle.
   The set back of the planes is 4 deg., and the dihedral approximately 2 deg.
   The following are the principal dimensions of the aeroplane, of which general arrangement drawings are given herewith :-

Maximum span 77 ft.
Span of lower plane 71 ft. 9 in.
Gap 7 ft.
Maximum chord 7 ft. 6 in.
Minimum chord 7 ft. 2 1/2 in.
Over-all length 41 ft.
Area of top plane 521.6 sq. ft.
Area of bottom plane 464 sq. ft.
Total area 985 sq. ft.
Area of upper aileron 32 sq. ft.
Area of balance of aileron 3.2 sq. ft.
Area of bottom aileron 22.4 sq. ft.
Span of tail planes 13 ft. 6 in.
Area of tail planes 45 sq. ft.
Area of rudder 16 sq. ft.
Area of rudder balance 3.2 sq. ft.
Area of elevators 19.2 sq. ft.
Area of fin 11.2 sq.ft.
Area of body
   in horizontal plane 96 sq. ft.
Area of body
   in vertical plane 107 sq. ft.
Weight empty 2,740 kg. = 6,039 lbs.
Useful load 1,235 kg. = 2,722 lbs.
Total weight fully loaded 3,975 kg. = 8,763 lbs.
Loading per sq. ft. 8.9 lbs.

Engines. Two 260 h.p. Mercedes.
Engine centres 14 ft.
Propeller diameter 10 ft. 2 in.
Track of main landing wheels 3 ft. 2 1/2 in.
Track of auxiliary landing wheels 2 ft. 7 1/2 in.

The speed of this machine at 12,000 ft. is estimated miles per hour.

Construction.

Wings. - The wings of this aeroplane are of wooden construction throughout, and have a section as shown in Fig. 1. This drawing also illustrates the construction of the rib (the web of which is of three-ply wood, extensively perforated, and the flange of solid wood grooved to fit upon the web, to which it is tacked).
   For the purposes of comparison, the section of the R.A.F. 14 wing is super-imposed and drawn to the same scale. This is shown in broken lines.
   The disposal of the spars is as follows :-
   Leading edge to centre of leading spar, 9 in.
   Centre of leading spar to centre of trailing spar, 4 ft. 4 in.
   Centre of trailing spar to trailing edge, 2 ft. 5 in.
   The space between the leading edge and the leading spar is covered as to the upper surface with three-ply, the rest of the wing being covered with fabric in the usual way.
   The spars possess several points of interest, and their dimensions and method of construction are presented in Figs. 2 and 3, from which it will be seen that they differ from the practice adopted in other German designs.
   The I Section main members are of spruce. The three-ply walls, applied to them by glueing and tacking, are principally birch, and are 4 mm. thick.
   The spars are wrapped with fabric throughout.
   In the earlier Gotha designs the sweep back of the wings was 10 deg. In the present design it is 4 deg., due probably to the fact that other means have been successfully adopted to get the centre of gravity sufficiently forward.
   It will be seen from the scale drawings that whereas the upper wing surface consists of two portions which unite at the centre line of the machine, the lower plane on each side consists of the centre section attached to the base of the fuselage, and an outward extension, between which is interposed a short span of plane forming, with the engine bearers and their struts, and the landing carriages on each side, a completely independent and separate unit. These small sections of planes are covered in with three-ply, both top and bottom, and the same material is used for the upper surface of the centre section of the lower plane.
   At the junction of the two upper wings, a rather unusual joint is employed; this is illustrated in Fig. 4, and consists of a series of rectangular staples which are held together by a steel wedge. The joints used in the lower plane are of a different character, and embody the usual pin principle, giving the spars, when not braced by the wiring, a hingeing action in the vertical plane. This joint is shown in Fig. 5, which also illustrates the manner in which the wings are braced against drag stresses by means of very light steel compression tubes and cables.
   Another view of the box joint on the spar end is given in Fig. 5a, which shows its internal construction. Joints of the above design are used on either side of the engine bearer section.

Struts.
   Apart from the struts which separate the engine eggs and brace them to the fuselage, there are three pairs of interplane struts on each wing. These struts are composed of steel tubing to which is attached a three-ply fairing. The design of the strut joint is shown in Fig. 6.
   The wire bracing throughout is by multi-strand steel cable, the fitting of which, however, presents no features of interest.

Ailerons.
   Only the upper ailerons are balanced, the upper and lower ailerons being connected by a single strut on each side. The operating lever is fitted on the top aileron, and works in a slot cut in, the upper main plane. From this lever wires are taken over pulleys on the leading spar of the lower plane, and thence to the fuselage through the space between the leading edge and the forward spar.
   Where the wires pass through the small sections of lower plane under the engines, they are provided with detachable connections which can be inspected through hinged flaps.
   The framework of the ailerons is of steel tube throughout, involving a welded-up one-piece construction.

Propeller Accommodation.
   In order to permit the engine eggs to be placed sufficiently far forward to allow of the centre of gravity being correct, considerable inroads have had to be made in the trailing edge of both upper and lower planes in order to give scope for the propellers. In front of the screws, the chord of the planes is reduced to 5 ft. 9 in., and at this point the trailing edge is very blunt.

Empennage.
   The whole of the empennage construction is of steel tubing, and the various components are rigidly braced together by inclined streamline struts, which, as in the case of the main struts, are of circular section steel tubing, to which a three-ply fairing has been added.
   These external struts give the Gotha tail a somewhat clumsy appearance, and would seem furthermore to exercise a notable masking effect upon the rear gun. Only the rudder is balanced, and it will be noticed that the area of this organ, compared with that of the fin, is very large.

Fuselage.
   The fuselage is in one piece from nose to rudder post, and is an entirely wooden construction, consisting of the usual longerons and wooden transverse members. It is covered in with three-ply throughout its length on the top, bottom and sides, but whereas in most German aeroplanes the three-ply lining is relied upon for solidifying the structure, in this machine it is extensively reinforced by diagonal wire bracings, especially in the forward portion of the fuselage at the point at which the main planes are attached.
   In the extreme front is placed the front gunner's cockpit. Immediately behind him, and on the left-hand side of the machine, sits the pilot; beside him is a folding seat for another passenger.
   Between the pilot's seat and the rear gunner's cockpit are placed the two main petrol tanks, which occupy the full width of the fuselage.
   The original intention of the designer was evidently to fit tanks of smaller capacity, shaped in such a way as to provide a communication tunnel between the pilot's seat and the rear gunner's cockpit. For this purpose the wooden bulkheads on each end of the tank space are deeply cut away on the left-hand side. With the existing arrangement of tanks, however, no interchange of personnel is possible.
   Another small point of interest is the inclination of the back of the pilot's seat; for this purpose careful consideration of space has resulted in a wedge-shaped piece being let into the forward tank, indicating again that all possible means have been adopted to get the C.G. sufficiently forward.
   The rear tank is of identical construction, and also possesses this wedge-shaped arrangement. In this case, however, the wedge-shaped piece represents waste of space.
   The rear gunner's cockpit is roomy and provided with a folding seat. Abaft of it, the fuselage is furnished with an elaborate gun tunnel, which, however, differs very markedly from that which was incorporated in the earlier Gotha designs, in which tine fuselage was completely covered in as to its top surface, and the tunnel was only used for a gun mounted on the floor of the cockpit. In the present design, the tunnel is furnished with a V-shaped opening in the upper surface, so that the gun mounted on the top of the fuselage can fire backwards and downwards through an arc of about 25 deg. laterally and about 60 deg. vertically. This is shown in Fig. 7.
   The inside of this tunnel is lined with three-ply wood, and its arrangement is clearly shown in Fig. 8. On the floor of the fuselage, in the rear gunner's cockpit, a mount is provided for a second gun, but in none of the Gotha machines brought down was a gun fitted at this point.
   It is noted that to give the rear gunner a greater feeling of security, and to prevent any loose articles from falling out, wooden cross pieces are fitted up immediately in front of the tunnel opening. At the forward end of the tunnel the fuselage is evidently weak, as it was at this point that breakage occurred in most of the machines brought down.
   Fig. 9 illustrates one of the brackets by means of which the fuselage is secured to the upper main plane; it carries a short stream-lined strut. It will be noticed that the characteristic German dome-shaped clip is used, but that in this case the usual welded joint is replaced by rivets. This bracket occurs at the after bulkhead immediately behind the rear petrol tank; the dotted lines proceeding from the small clip indicate how this bulkhead is cut away so as to provide, in the original scheme, an opening through which the personnel could squeeze in order to change places if necessary.

(To be continued.)


Flight, November 21, 1918.

THE GOTHA BOMBER
WITH NOTES ON GIANT AEROPLANES

[Issued by Technical Department (Aircraft Production), Ministry of Munitions.)
(Continued from page 1282.)

Undercarriage
   THE undercarriages on each side form, with the engine mountings and a small section of the lower main plane, completely independent units. There is no landing wheel under the nose of the machine as is the case in the Friedrichshafen design. Each -undercarriage has four wheels. The larger pair are attached to an axle placed immediately under the centre of the chord of the main planes, which point may be assumed to approach very closely the centre of gravity. This axle, as shown in the detail sketches reproduced herewith, moves up and down in guides against the action of two long compression springs concealed within the main undercarriage struts. A stout steel cable is passed over the axle and under two pulleys enclosed in the horn plate; thence it goes up inside the long springs to the heads of adjustable bolts, against which the upper ends of the springs abut. The axle is fitted with a large three-ply fairing attached by means of light straps, and at its outer end terminates in a tee piece, which slides up and down in a slot in the horn plate, and prevents the axle from turning round.
   Only the front undercarriage strut is streamlined. It is stayed with a tube to the middle of the rear strut, and a t this point the mudguard brackets are fitted.
   The front pair of landing wheels, the fitting of which is to facilitate landing in the dark, are supported on an axle attached to the frame extension by bands of steel coil springs of the type usually found in the smaller German designs.
   The front wheels are smaller in diameter and narrower in track than the main landing wheels.
   In every case the forward extension of the undercarriage was very badly crumpled up, and it is noticeably light in construction compared with the massive main landing gear.
   As might be expected, a very stout tail skid is fitted. This is shown in detail in Fig. 11.
   The hinged skid is very strongly stayed in all directions. At its upper end it is attached with loops of steel coil springs to two tubular steel rings clipped to either side of the fuselage. A steel cable limits the distance through which the tail skid can move.
   The body of the tail skid is of wood, but it is heavily rein forced with a steel shoe and with a steel front edge. Fig. 11 also shows the attachment of the lower tail struts to the bottom of the fuselage, and it will be seen that these are provided with sharp bars to discourage mechanics from lifting the tail by their means.

Engine Mounting
   The 260 h.p. six-cylinder Mercedes engines are carried on bearers arranged as shown in the drawing of the undercarriage, and illustrated with more detail in Fig. 13.
   The bearers themselves are of wood, and between the main vertical supports on which they rest are of the section shown in Fig. 14. They are attached to these main supports by ball joints of large diameter, and the struts are stream-lined with casings of thin metal. These are shown in Fig. 15.
   At their rear ends the engine bearers are united by a curved cross piece of hollow section, built up of sheet steel riveted together. (Fig. 16.)
   The engine bearers are triangulated to the plane section below them by cross wires as shown in Fig. 13, and also by diagonal steel tubes, the latter being attached by feet of the type shown in Fig. 17.
   The bracket supporting the bearers in front entirely surrounds them, and at is upper end is provided with an attachment for the strut which unites the engine mounting to the top plane spar, and also with a ball and socket attachment for the undercarriage bracing cables.
   At the bottom of the forward engine bearer support is attached one of the diagonal strengthening members of the forward undercarriage framework.

Engines
   In general the engines show no departures from the usual Mercedes practice, but there are a few points which are worth of note.
   Two different kinds of radiators were employed on machines otherwise exactly similar, the principal difference between these radiators being the arrangement of the shutters; in one case a series of vertical panels is used, and in the other a simple sliding door is adapted to be raised or lowered so as to shield the radiator surface to the required degree.
   Electrical thermometers of the usual pattern are fitted.
   The radiator controls are placed one on each side of the pilot's cockpit, and are illustrated in Fig. 20.
   Five different positions of the lever are provided for, and it works the shutters through return cables passing over a large aluminium pulley.
   Two different kinds of silencer were found; the type illustrated in Fig. 21 is similar to that used on previous Gothas, and also on the Friedrichshafen machines. It consists of a sheet steel manifold of very light construction, containing no baffles or other means of restricting the outflow of gas.
   The other type of exhaust box is shown in Fig. 22, and in this case it would appear that some attempt has been made not only to silence the exhaust, but also to prevent the aeroplane showing its whereabouts through the exhaust flames.
   This new type of silencer has been reported upon as follows :-
   The exhaust manifold has been altered in the spacing of the communications in order to fit a B.H.P. engine in a D.H. 9. The manifold consists of a cylinder 3 ft. 9 ins. long and 6 ins. in diameter; pointed nose and tail pieces are welded on, and 14 cooling fins running lengthwise are fitted. Between the fins a number of 1/4-in. diameter holes are drilled, forming a means of outlet for the exhaust gases, no baffle plates being fitted; the whole is made up of 20-gauge sheet steel, and is very flimsy in appearance.
   For testing this exhaust as a flame damper, a machine fitted with the manifold was flown at night with no navigation lights, and another machine was sent up to find it. As a silencer the manifold reduces the distance at which the machine is audible by a mean of about 4 per cent. No difficulty was experienced by the observing pilot in picking up the machine: although the flame usually seen at night was broken up, there was a stream of small sparks which made the aeroplane just as visible. In addition, it was noticed that the manifold became red hot when the machine was flown at full throttle.

Controls
   All the Gotha machines brought down were fitted with the same type of control, though certain detail differences are noticed.
   The ailerons are worked by a large diameter wheel by means of a chain and sprocket as shown in Fig. 23.
   Limiting cables are fitted and attached to an adjustable clip on the column.
   The wires are passed over pulleys, and issue through the ends of the transverse rocking shaft, whence they pass through the planes between the leading edge and the leading spar of the lower wings.
   At the extreme outer interplane strut they are taken over pulleys to the levers of the upper ailerons, which are connected to those of the lower ailerons by a light streamline strut. The horizontal rocking shaft extends through the side of the fuselage, and is there fitted in some cases with the simple form of double - ended crank shown in Fig. 23, but in others with the quadrant type of lever built up of steel tube, and illustrated in Fig. 24.
   The elevator and rudder wires are led along the outside of the fuselage through guides.
   The control wires for the elevator are duplicated, and in the case of the rudder a double crank is fitted on the rudder post. This is shown in Fig. 25.
   The rudder control bar is of the usual welded-up steel type, and is fitted with spring controlled heel rests. It is fitted with a grooved quadrant carrying the wires which pass over pulleys mounted in brackets on the inside of the fuselage walls. The rudder bar is shown incidentally in Fig. 27. No form of dual control is fitted. It is, however, of interest to note that whereas in the Friedrichshafen design means are provided both for adjusting the trim of the tail and for locking the controls in any desired position, the Gotha machine possesses neither of these refinements.

Engine Controls
   The throttle levers are fitted on the left-hand side of the pilot's seat, which is also on the left-hand side of the fuselage. This control consists of two mallet-headed levers, which are shaped so as to be conveniently worked either together or separately; the cranks and rods which they operate are placed outside the main section of the fuselage, and are covered in with a streamline metal casing.
   The engines are fitted, as is the usual Mercedes practice, with combination ignition and throttle controls; the function of the ball-headed third lever is not precisely known.
   In front of the pilot is a dashboard arranged as shown in Fig. 27, containing the usual switches, gauges, instruments and control taps. One of the latter is shown in more detail in Fig. 28.

Petrol System
   The two main petrol tanks carried in the forward position of the fuselage are equal in size, and have a joint capacity of 175 gallons. They are made of sheet brass, and appear to be well provided with internal baffle plates.
   On the left-hand upper wing, slightly to one side of the centre line of the machine, is a streamline gravity tank, strapped on to the upper surface, above which it projects; this gravity tank, which is used solely for starting purposes, has a capacity of about 10 gallons. It is filled from one or other of the main tanks by means of a hand-operated suction pump mounted on the right-hand side of the pilot's dash board, as shown in Fig. 27.
   The two main tanks work under pressure; an air pump of the usual type is mounted within reach of the pilot.

Armament
   Two Parabellum guns are carried - one in the forward cockpit, and one in the rear. The former is carried on a large ring mounting, which is shown in Figs. 29 and 30. In order to allow access between this cockpit and that of the pilot, part of the ring is made to hinge out of the way like the flap of a counter. The ring is extensively perforated with countersunk holes, apparently for lightening purposes. The holes of the hinged portion, together with the latch which secures them, are shown in Fig. 31. The gun is carried on a universally jointed bracket of the accepted design, which is furnished with an inclined extension, supported from the floor of the fuselage by a foot step bearing.
   The gun carrier is fitted with two steel rollers, which rest on the ring mounting, outside of which is mounted a gallery of light metal fitted with numerous holes for the reception of Very pistol ammunition.
   The rear gun is carried on a forked bracket, which slides over two rails made of bent steel tube, and mounted on the top surface of the fuselage as illustrated in Fig. 7. This gun carriage has a very limited arc of motion, and the usual expanded metal shields are fitted to prevent the gunner firing at the propeller, and possibly to prevent him leaning out far enough to be in danger of being struck by one of the blades.
   On the floor of the gunner's cockpit and close to the edge of the tunnel is a bracket designed for the reception of a second gun which would fire in a similar manner to that which was fitted on the earlier Gotha types. No guns fixed in this position have been found, and it is evident, therefore that the upper gun is relied upon to answer all defensive requirements.

Bombs
   The number and type of bombs carried on Gotha aeroplanes varies considerably, and the carriers are in consequence adapted to be easily removed and replaced by others of larger or smaller size, as the case may be.
   The carriers used on the Gotha are exactly similar to those which have been found on A.E.G. and Friedrichshafen machines and present no new features, with this exception that on the Gotha each carrier is furnished with an electrical detector device which informs the bomber that the projectile has actually left the carrier. This detector consists of a small switch, details of which are shown in Figs. 32 and 33, so that when the bomb leaves the carrier an electric lamp is illuminated inside the forward cockpit; this is carried out by means of a small spring-operated plunger switch.
   As a rule, eight bombs, each of 100 kg. weight, are carried - two being supported directly under the fuselage, and three on either side of the bottom plane centre section. Their release is effected by six small levers working the release gear through wires; each of these levers is painted a characteristic colour, and they are furthermore of different lengths, so that the bomber has no difficulty in pulling the right one. It would appear that each bomb carried on the centre section of the lower plane is released separately and that probably the two bombs underneath the fuselage are discharged simultaneously. The levers are shown at the back of Fig. 34, which also illustrates the folding seat and the communication flap between the bomber's cockpit and that of the pilot. Both the forward cockpits are furnished with large celluloid windows, which have been blacked over in all cases so as to be opaque.

Wireless
   The machine is internally wired throughout for giving greater wireless capacity, and the dynamo for the system is driven direct by one of the engines. It also furnishes current for the heating of passengers' clothing, for which plugs are arranged at convenient points.
   It will be noted in Fig. 34 that the floor in the corner of the cockpit is dished for the reception of the apparatus which carries the bobbin and the aerial wire.

Instruments
   The usual array of engine revolution counters, thermometers, pressure gauges, &c, is fitted on the Gotha, but no new types were found.

Fabric and Dope
   Both the fabric and dope on the Gotha aeroplanes conform to the usual German standard. The camouflage is similar to that of the Friedrichshafen, and consists of irregular polygons of various dark colours, which are printed on the fabric.

Gotha brought down by French A.A. Fire near Crochte, on July 4th-5th, 1918.
   The general construction of this machine appears to be similar to that described above in most respects, except for three modifications, which are worthy of note :-
   1. A biplane tail unit. This is illustrated in the photographs, Figs. 38, 39 and 40. It is similar in design to that of the Handley-Page, and embodies two fins on either side of the fuselage between the planes of the tail. The rudders are hinged to the trailing edges of these fins. The measurements of the tail unit are as follows :-

Top elevator span 5 ft. 7 in.
Top elevator chord 2 ft. 7 in.
Bottom elevator span 5 ft. 3 in.
Bottom elevator chord 1 ft. 6 1/2 in.
Balance piece 11 1/2 in. by 10 3/4 in.
Gap 2 ft. 9 1/2 in.
Bottom tail planes each average fore and aft measurement 2 ft. 5 in.
Span along trailing edge, each 4 ft. 2 in.
Top tail plane, average fore and aft measurement 2 ft. 5 in.
Span along trailing edge 8 ft. 10 in.

   This tail unit would appear to have been adapted in order to give the after gunner a better chance of attacking chasing aeroplanes, as the span is considerably smaller than that of the monoplane tail. It is constructed throughout of steel tubing.
   2. Extensions are fitted to the top ailerons as shown in the attached diagram (Fig. 35); it would appear from these that the lateral control of the Gotha has been found insufficient.
   3. The undercarriages are arranged in a similar manner to those of the Friedrichshafen, that is to say, there is a two-wheeled undercarriage underneath each engine, and a third two-wheeled axle mounted on to the fore part of the fuselage; the wheels throughout are of equal size, carrying 810 by 125 mm. tyres.
   Some details of the tail control are given in Figs. 36 and 37, from which it will be seen that double-ended levers with tubular tie rods are adopted for the rudders.

(To be continued.)