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

Albatros C V/16 and C V/17

   With the advent of a more powerful engine from the Mercedes stable in 1916 (the 220 h.p. D IV) Albatros Werke set about producing a successor to heir C III design. The engine itself was a somewhat revolutionary "straight eight", i.e. an eight-cylinder in-line engine with water-cooling arrangements. It was practically the earlier 160 h.p. D III but for the addition of two more cylinders and a reduction gearing to bring down the airscrew revolutions to 910 r.p.m. from a crankshaft speed of 1,400 r.p.m. To accommodate the added length and weight of this power plant a complete re-design of the airframe was necessary and not merely a few modifications as had been the case with the C I/C III variants.
   In the re-design, advantage was taken of the raised thrust-line (resulting from the gearbox on the forward end of the crankshaft) to improve the nose entry. The engine was almost entirely enclosed with easily-removed metal panels, only the water header tank remaining exposed. The cleaning up of the nose section was completed by the use of a large blunt spinner on the airscrew. The remainder of the fuselage was of the characteristic slab-sided, wood-and-ply construction and of roomier proportions than on the C I and C III. As before, it tapered to a horizontal knife-edge, but now a curved vertical fin was built integral with the fuselage and likewise plywood covered: the near semicircular tailplane was of wooden construction and also ply-covered. For the first time, a balanced rudder appeared on an operational Albatros two-seater, but followed previous practice in still being of steel tube framing with fabric covering. The elevator continued the same method, but was now a one-piece control and not divided as before; it was still not balanced.
   The wings, although of greater span, followed the same trend as those of the C III, retaining the unbalanced ailerons of inverse taper and angular rake at the tips: the chord of the lower wing was increased to the same dimension as that of the upper. The main ribs were interspaced with false ribs (literally little more than wooden (ash) strips) extending as far as the rear spar.
   Yet a third location was found for the radiators as compared with the CI and C III types. These were of the usually described "ear" type, located on the fuselage sides just above the leading edge of the lower wing. To a certain extent they detracted from the cleanliness that had been obtained in the nose section.
   An orthodox streamline steel tube undercarriage, with claw-type brake, was still used, as was the externally sprung tailskid mounted on an inverted pyramid of struts.
   Such, then, was the Albatros C V of 1916, or C V/16 as it was known to the makers. Due to the increase in weight and size, it proved a somewhat cumbersome machine to fly, and its unbalanced controls demanded no little man-power from its pilots. It was apparent to the Albatros design team that improvement of flight characteristics could be made, and a modified version was put in hand; this was known only by the factory designation of C V/17.
   The first concession to cleanliness was the fitting of a revised exhaust manifold exhausting sideways instead of vertically. Fitting an aerofoil-shaped radiator in the centre-section of the upper wing immediately obviated the considerable drag of the earlier "ear" radiators.' A further refinement was the fitting of a completely new lower wing with an elliptical tip profile, and substitution in the upper wing of ailerons of reverse taper which incorporated large inset (rectangular) balance portions. Finally, attention was directed to the tail assembly: the elevator was modified to include triangular balance portions at the tips, and the re-designed tailskid was internally sprung.
   With the balancing of all the flight controls, sensitivity was considerably increased, and the general cleaning-up resulted in a slight all-round increase in performance. In both C V/16 and C V/17 a forward-firing synchronized machine-gun was a standard fitment in addition to the observer's Parabellum gun on a rotatable mounting. Bombs and radio gear were also carried according to the particular duty. Here, then, was a good, solid, comfortable aeroplane; unfortunately its good qualities were marred by the vagaries of its eight-cylinder power plant. This, as so often happens in time of war, had been speeded into production before all the faults had been eliminated, and it lacked the reliability of its 160 h.p. DIII predecessor. The main fault was the extreme length of the crankshaft, necessitated by the eight "in-line" cylinder block, which rendered this component extremely prone to failure. Eventually, after production of no more than 424 examples, manufacture of this engine was discontinued, whereupon production of the Albatros C V terminated also.

TECHNICAL DATA
   Purpose: Two-seat general purpose (reconnaissance, artillery co-op, bombing).
   Manufacturer: Albatros Werke G.m.b.H.
   Power Plant: 220 h.p. Mercedes D IV 8 cylinder in-line water cooled.
   Dimensions: Span: C V/16, 12.780 m. (41 ft. 11 1/4 in.); C V/17, 12.620 m. (41 ft. 5 in.). Length, 8.950 m. (29 ft. 4 3/8 in.). Height, 4.500 m. (14 ft. 9 1/4 in.). Wing area, 43.4 sq. m. (468.72 sq.ft.).
   Weights: Empty, 1,024-1,069 kg. (2,253-2,352 lb.) difference representing cooling water for radiator. Loaded, 1,585 kg. (2,387 lb.).
   Performance:Maximum speed, 170 km.hr. ( 106.25 m.p.h.). Initial climb, 1,000 m. (3,280 ft.) in 8 min. Duration, 3 hr. 15 min.
   Armament: Parabellum gun for observer and fixed forward-firing Spandau for pilot.


Albatros C V Experimental
   This aircraft was a purely experimental variant of a standard C V/16 fitted with I struts to assess any advantage this type of interplane bracing might have to offer. The engine was the straight-eight-cylindered 220 h.p. Mercedes D IV of the standard machine. Span, 12.78 m. (41 ft. 11 1/4 in.). Length, 8.95 m. (29 ft. 4 3/8 in.).

J.Herris Albatros Aircraft of WWI. Vol 2: Late Two-Seaters (A Centennial Perspective on Great War Airplanes 25)

Albatros C.V

   Availability of new, more powerful engines resulted in the second generation of Albatros C-types. Albatros designers continued to use the same semi-monocoque fuselage construction and wood, wire, and fabric wings while emphasizing improved streamlining. Two new types were developed almost in parallel that used some of the same components, such as wings and tail surfaces.
   First to reach the front was the Albatros C.V using the 220 hp Mercedes D.IV eight-cylinder engine. It was closely followed by the Albatros C.VII using the 200 hp Benz Bz.IV engine. The different engines gave these similar aircraft different performance characteristics and consequently they were used for different combat roles.
   In January 1915 Idflieg gave development contracts for engines of 200 hp or more to Benz, Daimler (manufacturers of Mercedes engines), and Korting. Mercedes began work on two different engines to meet this requirement. The D.IV engine was an enlargement of the 160 hp, six-cylinder Mercedes D.III by the simple expedient of adding two more cylinders. The resulting engine, rated at 220 hp, was the first of the two to become available. The D.IVa engine was a totally new six-cylinder design that took longer to develop; when available it was rated at 260 hp.
   The Albatros C.V was designed around the first of these engines to become available, the 220 hp Mercedes D.IV. This straight-eight engine, the only such engine flown operationally during the war, was viewed as an interim engine and only a limited quantity were ordered pending availability of the more advanced Mercedes D.IVa.
   The D.IV had an integral propeller reduction gear that had two notable consequences. First, the thrust line of the propeller was raised above the crankshaft. This enabled the engine to be mounted lower in the airframe and allowed it to be fully cowled, improving streamlining. Second, the gear reduced 1400 RPM engine speed to 900 RPM for the propeller, allowing a larger, slower-turning and more efficient propeller to be used.
   The result was that the streamlined, more powerful C.V was significantly faster than preceding Albatros C-types. In fact, when it arrived at the front in July 1916 the C.V was faster than any Allied fighter at the front! This was a remarkable result for an essentially evolutionary design that was a product of a powerful new engine combined with careful development by Albatros. This happy result was also the only time an Albatros two-seater design provided such superior performance.
   The C.V's speed and climb made it a natural for long-range photo-reconnaissance missions and this was the role in which it excelled. Being larger and substantially heavier than earlier Albatros C-types, it lacked their maneuverability and was not at its best during general-purpose reconnaissance and artillery spotting, where good maneuverability to evade attacking fighters was important. Instead, the C.V was best at using its speed and altitude capability (missions could be flown at 5,200 meters, impressive for 1916) to avoid interception completely, and this it was able to do for many months in combat.
   The first production batches ordered in 1916 totaled 75 C.V aircraft. A final batch of 50 was ordered in January 1917 and these differed from the 1916 model in several respects. The aerodynamic improvements developed for the Albatros C.X and C.XII then in design and test were applied to this batch of C.V aircraft. The lower wingtips were rounded, the ailerons were aerodynamically balanced, and an aerodynamically balanced elevator was fitted. The ear radiators in the 1916 model were replaced by an airfoil-shaped radiator in the upper wing center section. Finally, the lighter control forces due to the aerodynamically-balanced controls enabled a control stick to replace the former control wheel. These changes enhanced maneuverability and performance, which helped the revised C.V/17 remain competitive as new Allied aircraft appeared.
   To differentiate between the two models, the earlier C.V model is denoted as the C.V/16 and the later model as C.V/17. Some C.V/16 models were given the later wings during factory repairs.
   The remaining C.V aircraft were withdrawn from the front in August 1917, and in December there were still 84 C.Vs of the 125 built in inventory, an impressive survival record. A few C.V aircraft were used as advanced trainers after withdrawal from combat, but the simpler, cheaper, easier to fly B.II, C.I, and C.III were much more popular as trainers.
   C.V 1420/17 was used as an airborne testbed for the 2 cm Becker cannon. Firing trials were performed in October and November 1917 with a downward-firing Becker fixed in the rear cockpit. The pilot must have been cramped because he shared the rear cockpit with the cannon, while the observer sat in front and apparently loaded the cannon.


Albatros C-Type Specifications
Albatros C.II Albatros C.III Albatros C.IV Albatros C.V
Engine 150 hp Benz Bz.III 150 hp Benz Bz.III 160 hp Mercedes D.III 160 hp Mercedes D.III 220 hp Mercedes D.IV
Span, Upper - 11.00 m (short span) 11.70 m (long span) - 12.78 m
Span, Lower - 11.04 m (short span) 11.14m (long span) - 12.44 m
Chord, Upper - 1.80 m - 1.80 m
Chord, Lower - 1.70 m - 1.80 m
Gap - 1.65 m - 1.83 m
Wing Area - 34.37 m2 (short span) 37.10 m2 (long span) - 43.4 m2
Wing Dihedral - 1.75° (upper & lower) - 2° (upper & lower)
Wing Sweepback - 1.70° (upper & lower) - -
Length - 7.95 m - 8.95 m
Height - 3.07 m - 4.5 m
Empty Weight - 771 kg - 1,069 kg
Loaded Weight - 1,271 kg - 1,585 kg
Maximum Speed - 135-150 km/h - 170 km/h
Climb to 1,000m - 5 min best, 8 min avg - 4.5 minutes
Climb to 2,000m - 12.5 min best, 22 min avg - 9.5 minutes
Climb to 3,000m - 25 min best, 45 min avg - 16 minutes
Climb to 4,000m - - - 25 minutes


Albatros C.V Production Orders
Order Date Qty Serials
Nov. 1915 3 C.3593-3595/15
March 1916 50 C.1175-1224/16
March 1916* 25 C.1250-1274/16
Jan. 1917 50 C.1371-1420/17
* Built by OAW (C.1251-1275/16?)

Журнал Flight

Flight, July 12, 1917.

SOME 1917 TYPE GERMAN AEROPLANES.

Albatros B.F.W. 225 h.p. (Type C. V).

   One of these machines, which was captured, had been built at the Bavarian Aircraft Works, Munich, and is almost identical with the Albatros C. III, which has been illustrated in "FLIGHT." Only minor alterations are to be found, as, for instance, in the rudder and tail, which are similar in shape to those of the D.I. The ailerons, it will be seen from the sketch, are balanced by a portion projecting forward in an opening in the wing. The engine is a 6-cyl. vertical Benz, developing 225 h.p. (1,415 r.p.m.). There are two machine guns and two bomb chambers.


Flight, February 28, 1918.

AN ALBATROS FIGHTING BIPLANE.

[Some time ago (in our issue of December 13th, 1917, to be exact) we published scale drawings and particulars of a captured German (Ago) biplane. Since then we have been, by the courtesy of the authorities, accorded every facility for obtaining full particulars of other captured German machines, and as a result we commence this week a detailed description of a very interesting enemy Albatros biplane, which has been captured practically intact. We are dealing with this machine rather more thoroughly than has usually been possible for us to do in the case of the majority of our descriptions of aeroplanes. This is partly because the machine is a very interesting one, and partly to aid those who, although the view-rooms in which these machines are exhibited are open to them at the request of their firms, live too far away, or for other reasons are unable to avail themselves of this opportunity of studying in detail modern German methods of aeroplane construction. The visitors' book at the view rooms in question reveals the fact that representatives and employees of numerous aircraft firms have taken the opportunity of paying a visit to this interesting exhibition, but it also shows that many firms, chiefly those situated far from London, are not yet to be found among the visitors. To those we therefore hope our descriptive articles will form an acceptable substitute for an examination of the actual machine. Further, among our American, French, and Italian Allies there will probably be many who would be interested in the details of a modern German aeroplane, and we therefore hope that aviation journals in these countries will consider themselves at liberty to reprint these articles. Our only stipulation is that when reprinting "FLIGHT" should be acknowledged. - ED.]

   THE Albatros biplane on view at the enemy aircraft view-rooms belongs to what is now commonly referred to as the C class, that is to say, a general utility machine used for artillery observation, reconnaissance work, photography, and fighting. Incidentally the machine appears to be also used for bombing - in a small way only - as it is equipped with a bomb rack holding four bombs.
   Aerodynamically the Albatros to be dealt with in what follows is, perhaps, chiefly interesting on account of the evident attempt on the part of the designer to provide as good a stream-line body as is possible having regard to such external fitments as machine guns, &c, which naturally detract to a certain extent from the efficiency of the lines of a body of a modern two-seater, where the gunner frequently has to stand up, with the upper portion of his body projecting above the fuselage covering. This effort at stream-lining is particularly noticeable in the nose of the machine, where the aluminium cowling over the engine is carried right across, leaving only the exhaust collector exposed. In front of the covering of the body proper is a cowl shaped as a truncated cone, which serves to enclose the nose and reduction gear of the engine, and to carry the lines of the body into those of the "spinner" around the boss of the air screw. The sides of the body, from a short distance behind this cowl to the tail, are flat, as is also the bottom, but the top of the fuselage is covered with a curved covering of three-ply.
   At the rear the fuselage terminates in a horizontal knife's edge, an easy flow being provided for the air by running the top covering of the fuselage into the three-ply covering of the fin in a smooth curve. Similarly, the fixed tail plane, which is of a symmetrical section and very deep, has its top surface practically in continuation of the top covering of the body, presenting no great and abrupt changes in curvature. The total effect is one of extremely smooth and easy flowing curves, and the body resistance cannot be very great in proportion to the cross sectional area of the body. We have no figures of the actual resistance coefficient in the formula R = k AV^2, but are inclined to imagine that the coefficient k has quite a low value.
   As regards the rest of the machine, the Albatros designer does not appear to have been so careful in cutting down resistance. For instance, the wings have the usual circular section stranded cables for taking lift and landing stresses, and no attempt appears to have been made at stream-lining these.
   Constructionally the Albatros shows much that is of interest, chiefly in the construction of the body, but also in other respects, as we hope to show in later instalments of this descriptive article. Fundamentally, the Albatros body construction is that employed in building light boats and hydroplanes. There is a light framework, consisting of four main rails at the corners of the rectangular section body, two auxiliary rails somewhere about half-way up on the sides, and bulkheads or transverse partitions of varying shape and thickness along the body at intervals. The whole is then, as in boat building, covered with a skin of ply-wood, in this case three-ply. Regarded as a compromise this form of body construction would appear to be quite good. Without entailing the time and expense of the true monocoque body, it provides a reasonably good stream-line form. As a manufacturing proposition it is probably about equal to the girder type of fuselage, while it has the advantage of not requiring any trueing up in the erecting process, this following automatically when making the parts over jigs and formers. One advantage this form of body does appear to possess, although to a somewhat lesser extent than the true monocoque - shell splinters and rifle and machine gun bullets are less likely to damage it seriously than is the case with the girder type. In the latter, should a longeron be shot through nearly all the strength of the structure is gone, whereas this semi-monocoque structure would retain its strength even after damaging some of the longitudinal members.
   Finally, there is the question of strength for weight. We have no data relating to tests of such a structure carried out by our own authorities, although possibly such tests may have been, and certainly should be, made. But in our issue of April 4th, 1914, we published particulars of an Albatros biplane which was brought over to this country and flown here by Thelen, which had a body fundamentally similar to the one at present under discussion, although differing from it in minor details. At the time we were furnished with some particulars of tests carried out on an Albatros fuselage of this type by the Deutsche Versuchsanstalt fur Luftfahrt, according to which the factor of safety of the Albatros body was about 60, and the resistance to bending 2.5 times greater than that of a diagonally wired fuselage of the same outside dimensions, and having members of the size usually employed in structures of this type. The Versuchsanstalt also stated that the Albatros firm were justified in concluding that the bending resistance of the veneer type of body is greater than that of a cross wired fuselage of the same weight, although no actual figures were given showing how much greater.
   When looking into the detail construction of the Albatros body, the first thing that impresses one, apart from the absence of internal cross bracing, is the extensive use that has been made of ply-wood in the construction of the transverse bulkheads or formers, which take the place of the struts and cross members of the girder type of body. In Fig. 1 are shown the different bulkheads of the body, with dimensions, &c. The rail half-way up the sides of the body is placed parallel with the propeller shaft, thus serving as a datum line from which to make measurements of distances and angles.
   In order to enable our readers to better form a conception of the Albatros construction we have shown, in Fig. 1, half-sections of the more important and representative bulkheads. In the front portion of the body the bulkheads, which here have to take the weight of the engine, are about 1 1/4 in. thick, and are made up of a number of laminations of wood, which are, of course, so placed in relation to one another that the grains of adjacent layers run at angles to one another. It was further noticed that in making up these bulkheads whole sheets of the different woods were not always employed. On the contrary, many of the layers appear to have been shouldered or spliced, being made up of comparatively small pieces. It is possible that this has been done with a view to utilising pieces of wood that would otherwise have had to be scrapped. On the other hand it may have been done to increase the amount of crossing of the different grains. In any case, it would appear to serve both purposes, although one would expect the time taken in manufacture to be somewhat increased by such careful fitting together of small pieces of wood.
   Fig. 2 shows the nose of the Albatros, and clearly indicates the method of supporting the engine. The first bulkhead, it will be seen, is solid, and is at right angles to the propeller shaft. The second bulkhead - 2, Fig. 1 - is lightened by piercing as shown, and is also vertical, while the third engine support is formed by a solid bulkhead - 3, Fig. 1 - which slopes back so as to support the front chassis struts and front cabane struts at its lower and upper ends respectively. As the front engine support is clearly shown in the sketch, Fig. 2, it has not been included in Fig. 1. The bulkhead numbered 1 in Fig. 1 is merely a former, and does not help to support the engine bearers. These are of I section spruce, and have plywood flanges top and bottom as shown in Fig. 3. The upper flange is continued outwards to the middle longeron so as to form a shelf or bracket at the sides of the engine.
   A construction somewhat different to that of the engine supports is employed in the panel between the pilot's and gunner's cockpits. This consists (4. Fig. 1) of a spruce framework faced each side with 3 mm. three-ply, the whole having a thickness of 26 mm. (about 1 in.). Behind the gunner's cockpit is a light partition built up as shown in 5, Fig. 1. Two light spruce struts run diagonally across from corner to corner of the body, crossing in the centre of the fuselage at which point they are reinforced by three-ply facings and triangular blocks glued into the corners.
   Their attachment to the upper and lower body longerons is of a similar construction, and will be clear from the diagram. On their front faces these diagonal struts are provided with a 2 mm. flange to stiffen them against buckling. A canvas curtain is secured to the front of this partition, having in it pockets for maps, &c.
   From this point back to the point where the tail plane and vertical fin are attached, the formers of the body are in the nature of a very light framework of thin struts, a typical one being shown in 6, Fig. 1. The general construction and some of the dimensions of the various members will be clear from the illustration.
   One of the features in which the present Albatros differs from previous types is the construction and attachment of the tail plane and vertical fin. The latter is covered with three-ply, and is made integral with the body, out of which it grows, so to speak. The construction is shown in 7 and 8, Fig. 1, and in the perspective sketch, Fig. 4. The tail skid is supported on one and sprung from the other of these two bulkheads, as illustrated in Fig. 5, the general and detail construction of it being evident from the sketches. The tail plane is provided with hollow spars which fit over cantilever beams integral with bulkheads, 7 and 8, Fig. 1, the details of which arrangement will be dealt with later.

(To be continued.)


Flight, March 7, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Continued from page 227.)

   HAVING dealt with the bulkheads or transverse partitions of the Albatros fuselage in our issue of last week, the longitudinal rails will be considered next. These are of a somewhat complicated nature, varying as they do along their entire length, not only as regards being tapered from front to rear, but also in the different form of spindling out employed at the various points, and in the method of reinforcing with other strips of wood, partly in order to increase their strength where required and partly to make their overall section conform to the various angles and curvatures of the outside three-ply covering of the fuselage.
   From Fig. 6 a fairly good idea may be formed of the shape and dimensions of the longerons at various points. The lower one (left hand) is originally of rectangular section, but is lightened from point to point by various forms of spindling and stop-chamfering. Thus at the point B (see key, diagram Fig. 6), the inner face of the bottom longeron is spindled out on its inner face with a curved cutter. At other points of this longeron farther towards the stern various sections are met with, as channel, solid rectangle, and L sections of various proportions. Between the horizontal stern post and the point at which the middle longeron meets the lower one, the latter is reinforced with a triangular section strip, so as to carry the three-ply covering into the sloping side. Similarly at the section A, Fig. 6. the longeron, which is here of solid rectangular section, is reinforced on the outer side with a curved trip, spindled out externally, and with a smaller strip on the lower face of the longeron. This is done partly to strengthen the longeron, which at this point is subject to an increased compressive load, owing to the overhung engine, and also to afford attachment for the three-ply covering, which at this point changes from flat sided to rounded section where the sides gradually merge into the truncated cone of aluminium which forms the extreme nose of the body proper, i.e., at the point just behind the "spinner" on the air screw boss.
   The upper longeron, which is originally of rectangular section, is spindled out to channel and L sections at various points, as shown in X, Y, Z, Fig. 6. So as to form an attachment for the curved top of the body, the top longerons have glued to their upper face additional strips of triangular section while at the point Y, Fig. 6., the section is left rectangular so as to form a support for the gun ring. In addition to their function as strengthening members these strips serve the further purpose of preventing the bulkheads from sliding along the longerons, as they are cut off where a bulkhead occurs, against the front and rear sides of which they abut. In some places, as for instance in the front of the body where the covering is in the form of an aluminium cowl over the engine, the strips are omitted and the cowl attached to turnbuttons as shown in the sketch Fig. 7. At such points the bulkheads are prevented from sliding along the longerons by a long wood screw passing horizontally through the longeron into the bulkhead.
   The middle longerons, which, as already pointed out in a previous article, are horizontal, i.e., parallel to the propeller shaft, are of smaller overall dimensions than are the four main longerons. They are rectangular section, lightened in places by stop-chamfering, as shown in a and b Fig. 6.
   Fig. 8 shows, in side elevation and plan, the general arrangement of the fuselage, and should, in conjunction with the various sections and key diagrams, explain fairly clearly the general lay-out of the body. It will be noticed that in plan the sides of the body are straight from the tail post forward to the pilot's cockpit. For ease in manufacture it is an advantage that the ribs of the tail plane should be at right angles to the spars, and in order to effect this it is necessary that the sides of the body should be parallel for the length of the tail plane. Since, however, to provide for this the longerons would have to be changed from a converging direction to a parallel one which would necessitate a somewhat sharp bend in them at the point where the tail plane commences, and as, moreover, the depth of the tail plane is not the same as that of the body except at the extreme rear, a different course has been followed. From the point where the tail begins two extra longerons on each side have been built into the bulkheads of the body. These two short longerons have, in plan, a direction parallel to the line of flight, while the main longerons continue on their converging course. This arrangement is indicated in the plan view Fig. 8. In side elevation the short longerons, against which lie the inner ribs of the tail plane, have the same curvature as the tail plane. In this manner the lines of the rear part of the body are not spoiled, while an easy flowing curve is provided for running the tail plane into the body. The arrangement will be further made clear by reference to Fig. 1, page 224.
   Reference has already been made to the peculiar attachment of the tail plane to the body. The sketch at the top of Fig. 9 shows in perspective this attachment, which is also illustrated in the diagram in the bottom left-hand corner of Fig. 9. The bulkheads of the body are extended outwards to form cantilever beams which support the tail plane. There are three of these cantilever beams, while further support is provided for the tail plane leading and trailing edges as indicated in the sketches. The spars of the tail plane are of the box type, built up of ash flanges with thin three-ply sides, cut out for lightness. These spars are so proportioned that they lit over the cantilever beams, which do not, it will be seen, run right out to the edge of the tail plane, but are finished off just outside the second tail plane rib. No external bracing of the tail plane is provided, the depth of it and the method of mounting being relied on for the necessary strength.
   To provide against the tail plane sliding off its cantilever supports it is secured at the leading and trailing edge. The former attachment is indicated in the bottom right-hand corner of Fig. 9. A sheet steel shoe fits over the corner of the leading edge and inner rib, and through this shoe a long bolt passes, which runs across the body to a similar shoe on the other side. In Fig. 10 is shown the rear attachment of the tail plane. A sheet steel box surrounds the corner of the fuselage. Welded to this box is a short tube which fits into a circular recess in the end of the trailing edge of the tail plane. As the elevator tube runs right across and is fitted with collars bearing against the sides of the clips that form the bearing for the elevator tube, the trailing edge of the tail plane is prevented from slipping outwards.
   The manner employed of forming bearings for the elevator is indicated in the diagrams of Fig. 10. A steel strip is bent over the tube, and its two free ends are bent over and fit into slots in the trailing edge of the tail plane. Each clip is then secured to the tail plane by a vertical bolt as shown in the diagram. The trailing edge of the tail plane is spindled out to a semi-circular section as shown, and a curved metal distance piece is screwed to this trailing edge or spar, so as to form the second half of the bearing of which the bent steel strip forms the other half. To remove the elevator the bolts securing the clips are undone; the clips are then bent outwards until their free ends clear the slots, when the elevator can be removed bodily.
   As the elevator is built of steel tubing throughout, wood blocks of the shape shown in detail 1, Fig. 10, are employed for attaching the fabric covering. These blocks span over the steel strip bearings, and are secured to the tubular leading edge of the elevator by screws as shown in section B-B. A hole in the opposite wall of the tube serves for the insertion of the screwdriver.
   Under the horizontal stern post of the body are two short tube stumps, closed at their lower ends. The object of these is not at first apparent, since they appear too short to protect the elevator, but when it is remembered that the Germans favour transportation by road, trailing the aeroplane behind a lorry, it becomes at once evident that these stumps serve to support the stern of the body on the floor of a lorry while the machine is trailed behind on its own wheels.
   As regards the remaining details of the tail of the Albatros little need be said, as they are fairly evident from the plan and sections of Fig. 11. It will suffice to point out a rather ingenious construction of the leading edge of the tail plane. In plan the tail plane, it will be seen, is roughly semi-circular, and its leading edge therefore has to be shaped to this curvature. As an ordinary strip of solid spruce spindled out to a semi-circular section would scarcely be strong enough for this work a different method has been employed. It appears that originally the leading edge of the tail is made up of four laminations of ash, having, of course their grains running in slightly different directions. The rectangular section spar thus formed is then spindled out to a semi-circular section, as shown in the diagram, leaving the impression that the leading edge is made up of seven thin strips of wood glued together. The resulting leading edge appears to be one of great strength, while at the same time being quite light.

(To be continued.)


Flight, March 14, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Continued from page 255.)

   THE cockpits of the Albatros are arranged in the fashion now universally adopted for two seaters, by Allies as well as by the enemy, i.e., the pilot in front and the gunner in the rear cockpit. The pilot's seat is mounted, in the Albatros, on the main petrol tank, which has two annexes on top, one on each side of the seat. This arrangement is clearly indicated in Fig 12, in which the small clips preventing the seat from sliding about on the tank will be noticed. The filler cap is mounted on a tubular projection extending through the fuselage covering, thus enabling the tank to be refilled from the outside. A smaller auxiliary tank is mounted above and to the rear of the main tank, in the gunner's cockpit, as a matter of fact. Both tanks are connected up to a by-pass or distributor, so that both or either tank can be connected up to the engine, two pumps being provided for maintaining the necessary pressure, one driven by the engine and the other hand operated. Thus, whatever tank is being used, petrol is fed to the carburetor under pressure. This has probably been a necessary provision, as the tanks are placed relatively low and gravity feed would, therefore, be apt to be unreliable when the machine is climbing at a fairly steep angle.
   Constructionally the petrol tanks are of interest in that they have been internally braced by rods running across from side to side, the attachment of the rods being visible on the outside of the tank as shown in Fig. 12 (p. 285). To prevent the petrol from slushing about inside when the tank is nearly empty baffle plates are fitted dividing the man tank longitudinally into five compartments, communicating with each other through the circular open rigs shown in the section of the tank. Fig. 12. As the supply pipe leaves the tank fairly high up - it can be seen on the front right-hand side of the tank in Fig. 12 - it is carried down inside to the bottom of the tank so as to enable the last drop of petrol to be forced out and into the carburettor. The main tank is mounted on brackets as shown in one of our sketches, and is secured by metal straps having an arrangement for adjustment.
   In Fig. 13 (p. 285) is shown the general arrangement of the controls. There is a transverse rocking shaft on which are mounted at each end crank levers for operating the elevators, while in the centre, pivoted so as to be free to rock laterally, is mounted the main control lever. Mounted on the transverse shaft, but not moving with it, is another lever, which operates the claw brake mounted on the wheel axle. The arrangement of this brake is shown in Fig. 14. By pulling the lever the free end of the claw brake is pulled upwards, thus causing the claw to dig into the ground. On releasing the lever, the brake is returned to its normal position by the action of the spring shown in the sketch.
   The transverse rocking shaft is carried, as indicated in Fig. 14, in two bearings mounted on the lower longerons. A forward and backward movement of the control lever causes the shaft to oscillate, and with it the two crank levers to which are attached the elevator control cables. These cables run from the crank lever, around a pulley slightly forward of the transverse shaft as shown in the sketch, and hence to the top crank lever on the elevator. The return cable runs from the crank on the under side of the elevator to the crank on the transverse shaft. En route these cables pass over pulleys mounted in the rear position of the fuselage, these pulleys being shown in detail in some of the accompanying sketches (Fig. 15).

(To be continued.)


Flight, March 21, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Continued from page 287.)

   As regards lateral control, the general arrangement of this is indicated in diagrammatic form in Fig. 16. From the control lever the direct cable passes over a pulley on the transverse shaft, along through the bottom wing, around another pulley in the wing, and hence to the rear half of the aileron crank lever. The return cable runs from the front half of the aileron crank lever, around another pulley in the lower wing, through the wing and through the transverse shaft to a pulley on the other side of the control lever, and hence to the screw on the control fever. The details will be clear from Fig. 13.
   The foot bar operating the rudder is mounted on a pyramid of steel tubes, and the rudder cables are taken, not, it will be seen, from the foot bar itself as is generally done, but from a short lever projecting forward at right angles to the foot bar. From this lever the cables pass over pulleys and to the cranks on the rudder. It will be seen that provision has been made for making adjustments of the foot bar to suit pilots of different height by fitting an extra foot bar. If the machine is to be flown by a taller pilot, this is removed and the main foot bar used. Wire clips are provided, it will be noticed, for accommodating the pilot's heels so as to prevent his feet from slipping off the foot bar.
   As in the majority of German machines provision has been made for locking the control lever in any position, either flying level, climbing, or descending. This is accomplished by means of a collar free to slide along the control column, but being split and provided with a bolt for tightening up, when the collar is locked in position on the control column. Anchored to this collar by two screws is a fork end, from which a tube runs down and forward to terminate in a ball and socket joint secured to the bottom of the fuselage. This ball and socket joint, it will be seen, enables the control column to be moved freely in any direction, and to allow it to be moved from side to side, even when the forward movement of the column is prevented, by locking the collar. In this manner, the pilot can lock the elevator, while operating the control column from side to side for lateral control with his knees.
   As far as can be ascertained, although the machine gun was not in place on the machine as exhibited, one synchronised machine gun was fitted, resting on top of the fuselage on the right-hand side. The pilot operated this gun by means of the trigger on the hand grip of his control lever, which is shown inset in Fig. 13.
   While on the subject of controls, reference might be made to the crank levers on the elevator and rudder. These are shown in Fig. 17, from which their construction will be evident. The crank lever of the elevator has projecting from it a tapering tube running to the trailing edge of the elevator. The tubular rudder post is working in bearings similar to those described in our last issue when dealing with the hinges for the elevator. At the bottom the rudder tube fits into and is supported by a socket carried on a clip bolted to one of the transverse bulkheads of the fuselage. A peculiarity characteristic of the Albatros is the method of attaching the control cables to the crank levers. A socket is formed in the end of the crank lever, and into this fits a cup-shaped piece of steel machined on one of the bolts of the wire strainers, much in the same manner as the terminal attachment of the main lift cables. Thus any vibration in the control cable is not transmitted to the crank lever, the cup-shaped head of the turnbuckle bolt being free to move in its socket in the crank lever.
   Reference has already been made to one part of the armament of the Albatros, namely, the synchronized machine gun operated by the pilot from the trigger on the main control column. In addition there is a movable machine gun mounted on the usual gun ring in the rear cockpit. The general arrangement of this gun mounting is shown in the sketch, Fig. 18. The gun ring itself is built up of thin three-ply wood, and runs on small rollers on its support so as to reduce friction. It is prevented from tilting up by wooden angle pieces screwed to its underside and overlapping the fixed support. The whole arrangement looks somewhat clumsy, but is apparently quite light, and the strength is probably reasonably good, as the three-ply of which the gun ring is made up of different curvatures, each of which tends to strengthen the others.
   The machine gun is supported on the gun ring by a swivelling fork, which can be raised and lowered as required, and which, can be locked in any desired position by the locking arrangement indicated in the sketch of the general arrangement. In addition to .its circular movement integrally with the gun ring, the machine gun may be swung laterally on its pivot in the gun ring. Here also a locking device is provided in the shape of a split collar locked by an L bolt, as shown in one of the insets. The other inset in Fig. 18 shows the lever by means of which the gun ring is locked in any desired position. A rocker arm composed of two steel strips is pivoted in its centre on a pillar projecting downwards from the gun ring. At one end this rocker arm carries a plate welded to the two steel strips of the rocker, and at the other it carries the hand lever which is so formed and pivoted as to give an eccentric movement when the lever is swung through an arc. The modus operandi will be clear from the sketch. When the gun ring has been swung around to the desired position, the hand lever is pushed down; in so doing the eccentric forces the inner end of the rocker down, thus causing its outer end carrying the flat plate to move up against the fixed support for the gun ring and thereby locking it. A pull on the lever instantly releases the gun ring if it is desired to swing the gun around to another quarter.
   As presumably it frequently happens that the gunner wishes to fire from a standing position his seat has been so arranged as to swing into a vertical position as soon as it is relieved of his weight. This is accomplished by means of a spring under the seat, as shown in Fig. 19, which is, we think, self-explanatory. A strip of wood runs transversely under the seat and projects a short distance on either side. These projections rest, when the seat is in a horizontal position, in brackets secured to the sides of the fuselage.

(To be continued.)


Flight, March 28, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Continued from page 310.)

   THE Albatros biplane belongs to the C class, that is to say is a general utility machine variously used for fighting, reconnaissance, artillery spotting and photography, and is therefore not to be considered a bombing machine. It is, however, provided with racks for a small number of bombs - four, to be exact - presumably by way of cases of emergency when a suitable target might present itself. Fig. 20 is a diagrammatic perspective view of the bomb racks and bomb release gear. The bombs are secured underneath the main tank in the pilot's cockpit, but they are released by the gunner in the rear cockpit by means of a small lever and quadrant shown in the upper right-hand corner of Fig. 20.
   The bomb racks are in the form of sheet steel supports, against the bottom of which rest the nose and the tail of the bombs respectively. These brackets are secured to transverse members in the bottom of the fuselage, which have been omitted in the drawing for the sake of clearness. The bombs themselves are supported by a steel strap or band, passing underneath and approximately under the middle of the bombs. At one end the straps are hinged, while at the other they are provided with an eye, which is secured in the hook under the release trigger. The sketch in the upper left-hand corner of Fig. 20 shows in more detail the hook in which the eye of the strap rests, and the trigger by means of which the strap is released. The trigger is pivoted near its centre, and has an upward projection to which is attached a small coil spring resting in a groove in the base supporting the hook. When the cam on the transverse shaft presses down the rear end of the trigger, the front end moves upward against the tension of the coil spring mentioned above, thus releasing the strap and with it the bomb.
   As regards the cams which operate the bombs, these are mounted on a transverse shaft running across the bottom of the fuselage. There are four cams, each operating its trigger, but the gearing of the camshaft is such that it requires five pulls on the lever in the gunner's cockpit to rotate the shaft through a complete revolution. One of these pulls of the lever has no corresponding cam on the shaft, and has, it appears, been incorporated in order to provide an equivalent of a safety catch. When all the bombs are in place the first pull on the lever does not release a bomb, but merely brings the cam for bomb No. 1 into position, ready to press, on the next pull of the lever, the trigger for the first bomb. This has evidently been done as a precaution against accidentally releasing a bomb until the machine is approaching an objective.
   We now come to consider the method of operating the transverse camshaft. Near the right-hand side of the fuselage there is mounted on the camshaft a small ratchet having five teeth as shown in the bottom right-hand corner of Fig. 20. On this ratchet is a small cam, roughly of cone shape. This cam engages with grooves in the pulley around which passes the operating cable. A small leaf spring engages at the proper moment with the notches in the ratchet and prevents the shaft from rotating in the reverse direction. One end of the operating cable is attached to a coil spring secured to the side of the fuselage, and passes from there around the pulley to the lever in the gunner's cockpit. Assuming that the first cam is in position ready to release its bomb, a backward pull of the lever rotates the pulley and with it the ratchet and camshaft, thus pressing down the trigger of cue of the bomb racks and releasing a bomb. When the gunner releases the lever this is pulled forward to its normal position by the spring on the side of the fuselage. The little leaf spring engaging with the ratchet prevents this and the shaft from following the pulley round in the opposite direction, and the cam on the ratchet sliding up the sloping bottom of one of the five grooves in the face of the pulley forces the pulley away from the ratchet against the compression of a small coil spring shown in the sketch. By the time the lever has reached its forward position, the pulley has revolved to such an extent as to bring the cam on the ratchet into the next groove in the pulley, and when the lever is again pulled the whole action is repeated. The sketch will probably help to make the action clear.
   In addition to a bomb release lever, there is in the gunner's cockpit another lever, the function of which appears to have been to engage and disengage a clutch near the engine, by means of which a drum is operated carrying the aerial of the wireless. In the bottom of the gunner's cockpit, near the left-hand side, is an octagonal opening in the floor, in which, so far as we can make out, the camera was mounted. The compass, so as to be visible from both cockpits, has apparently been mounted in a circular opening in the right-hand lower main plane.
   We now come to deal with the wings of the Albatros. These are, generally speaking, of the construction favoured by the Albatros designer, that is to say, the front spar is well forward close to the leading edge, and the rear spar is approximately half-way along the chord. In addition there is a third false spar, which is not, however, connected up to the body nor supported by any struts, and which cannot therefore be considered as taking any particularly important part of the load. It will, therefore, be realised that the rear main spar may at small angles of incidence, when the centre of pressure moves backwards, be called upon to support all or nearly all of the load. This has evidently been guarded against in the Albatros by making the rear spar of generous proportions. Both main spars are made of spruce, and are of the box type, consisting of two halves spindled out and glued together with a hardwood tongue running through both flanges. The ribs are of I-section, with spruce webs and ash flanges. Between the main spars false ribs are employed half-way between the adjoining main ribs, so as to better preserve the curvature of the wing for this distance.
   The general arrangement of the upper left-hand wing is shown with dimensions in Fig. 21, from which the general lay-out of the wing will be clear. The internal drift wiring is in the form of five bays, the compression struts for this wiring being in the form of circular section steel tubes. In the two inner bays both drift and anti-drift wires are in duplicate and are approximately 12 S.W.G. The next two bays have single wiring, also of 12 S.W.G., while the outer bay has single wiring of 14 S.W.G.
   The attachment for the compression tubes and the drift and anti-drift wires is shown in Fig. 22. A box of thin sheet steel surrounds the spar at this point and is bent over and bolted as shown in the small section in Fig. 22. On the inner face of the spar this sheet steel box has two wiring plates stamped out, which receive the drift and anti-drift wires. A short cylindrical distance piece is welded on to the box, and around this fits a short tubular sleeve, held in position by a split pin. This sleeve forms a socket for the tubular compression strut.
   Vertically the spar is pierced at this point by three holes, for the bolts securing the interplane strut and the two interplane cables. The attachment for the latter is shown at the bottom of Fig. 22. The base plate has machined in it two recessed circular openings which receive the two terminals for the cables, These terminals are prevented from rotating by a small rivet as shown in the sectional view. In order to further strengthen the spar at the point where it is pierced by these three bolts, the spar is left solid for a short distance on each side of the box, and packing pieces are interposed between the box and the spar, so as to bring it up to an approximately rectangular section in order to get the bolts coming through the spar and base plate at right angles.
   In Fig. 23 are shown sections, to scale, of the two main spars, the false spar, and the leading edge. The trailing edge is, as in the majority of German machines, in the form of a wire.
   Fig. 24 shows the shape and dimensions of the wing section. As in nearly all German machines, the camber is, it will be seen, extremely great both as regards the upper and lower surface.
   The precise object of employing such a wing section is not at once apparent, but it should be remembered that generally speaking the German machines carry a comparatively great load per square foot of wing surface, and the probabilities are that the section has been designed with a view to enable the wing to support this high load at comparatively great altitudes, and has therefore probably an excess resistance at lower levels.
   This is not quite clear, however, and it would be extremely interesting to have the results of wind tunnel tests on some of these German sections, and we sincerely hope that the National Physical Laboratory may be able to find the time to carry out such experiments.
   Superficially the section does not impress one as being particularly efficient, but wind tunnel tests might reveal the fact that it is a good section for carrying high loading at considerable altitudes.

(To be continued.)


Flight, April 4, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Continued from page 336.)

   IN our last issue the general construction of the wings of the Albatros was dealt with, and we intend to supplement the information then given in our present issue with some of the more interesting constructional details of the wings. Fig. 26 shows some details of the upper left-hand wing near the tip, and also the general arrangement of one of the ailerons. As will be gathered from the sketch at the top of Fig. 26, the wing flaps are built up of steel tubing throughout, and each aileron is balanced by a forward projection, not, as in the Gothas, outside the tip of the main wing, but working in an opening in the main plane. As in nearly all German machines, the aileron is not hinged to the rear main spar, but to a third false spar situated between the rear main spar and the trailing edge. The method of hinging the aileron will be clear from the detail section and elevation at A. A steel clip is bent over the tube of the aileron and has its forward ends bent into grooves in wood blocks on the front face of the spar, much in the same manner as was employed in the case of the elevator hinge and described when dealing with that member. As in the case of the elevator the fabric covering of the wing flaps is attached to wood blocks screwed to the tube.
   The crank lever for operating the wing flap is in the form of an elliptical section tube tapering towards its ends. Each half of this crank lever carries three wiring clips, as shown at B. It will be seen that by providing three clips on each end instead of one, a means for varying the gearing of the wing flap control is furnished. If a pilot wishes the machine to be fairly sensitive on the lateral control he will naturally attach his wing flap cables to the inner clips, since thereby a movement of the control lever will result in a larger movement of the wing flap. On the other hand, if he prefers to have a large movement on his control lever without too great corresponding angularity of his wing flaps or ailerons, he will attach his cables to the outer clips, as this will result in a "gearing down" of the wing flap.
   The forward end of the wing flap crank lever works in a slot between two closely spaced ribs, as shown in the sketches. At this point the ribs are strengthened by making them of the box type for their rear portion, and the ash flanges of the ribs are left wider over this portion, while being reduced to their normal width from the rear spar forwards, as indicated in the sketch. At this point also occurs the strut and lift cable attachment. This strut being the last, there is only one cable instead of the two occurring where the inner struts are attached, otherwise the attachment is similar in principle to that illustrated last week. The spar box and strut and cable attachment is indicated in the detail sketch at C. The tubular compression strut is secured in the same manner as that of the fitting previously referred to.
   As previously pointed out, the trailing edge of the Albatros wings is in the form of a wire, and the method whereby the outer main rib is prevented from bending sideways is illustrated in the detail sketches at D and E. In addition to the wire forming the trailing edge, there is another wire running parallel to it and carried right through the wings, the object of which appears to be to provide a counterpoise capacity. The wiring in the Albatros is not extensive, and in the case of the fuselage it is absent altogether, and it therefore appears probable that the thin cables running along the wings and the longerons of the fuselage serve the purpose of providing the necessary amount of wiring, otherwise one is at a loss to account for their function.
   It has always been customary for German aeroplane designers to provide some easy means for quickly detaching the wings from the body, and the present Albatros is no exception from the rule in this respect. The cables themselves are not, it is true, fitted with the quick release devices one finds on the L.V.G., for instance, but the spar attachment has been designed to facilitate the removal of the wing, even if that of the cables has not. In Fig. 25 is shown the spar box and its attachment of the lower wing. A sheet steel box surrounds the root of the spar, and has in its end a slot into which fits the lug secured to the side of the body. This spar box is ribbed internally as shown in the sketches, and the spar itself has in its end saw cuts accommodating these ribs.
   Welded to the side of the spar box is a socket forming a bayonet joint, into which fits a pin fitted with a small spiral spring. The spar is held against the side of the body with the lug projecting into the spar box, and the pin is inserted and given a twist so as to bring the projections on the pin into the notches in the bayonet joint, and the spar is secured. For removing the wing all that has to be done is to press the pin slightly against the action of the spiral spring, give it a twist and pull it out of its socket, and the spar can be withdrawn. The spar is secured to the spar box by screws, and the box is further secured against tensional loads by a steel strip about a foot long running along the face of the spar and anchored at its other end by a bolt passing horizontally through the spar.
   As the lower wing spars are subject, in addition to the bending moment owing to the lateral load on them, to tension, the attachment to the body has to be such that it will resist a tensional load as well. The method of doing this is shown in the right-hand sketches in Fig. 25. The lug to which the spar is attached fits into a recess in the base plate formed by stamping. The axial pull is transmitted across the bottom of the fuselage via the brackets and strips shown, which are bolted to the base plate holding the lug. In order to prevent the lug from turning it is riveted by four rivets as indicated.
   The upper planes are attached, as in nearly all German machines, to a four-legged cabane. In addition to supporting the wings the cabane of the Albatros carries the radiator, which is of the same shape as the wing section and which fits into an opening in the wing. The cabane is shown in Fig. 27. It will be seen that one of the cabane legs carries for a short distance the water tube from the radiator to the engine.

(To be continued.)


Flight, April 11, 1918.

AN ALBATROS FIGHTING BIPLANE.
(Concluded from page 370.)

   THE attachment of the upper wing spars to the cabane is somewhat similar to that of the lower spars, inasmuch as a pin fitted with a spiral spring secures the spar to the cabane. Here, however, the similarity ceases. Instead of the spar box into which fits the lug on the side of the body, the upper spars are provided with a forked lug, probably a forging machined to shape, of the form shown in Fig. 28. The lug of the opposite spar is of the same shape, but is, of course, reversed, so that when the two spars meet against the top of the cabane, their respective lugs are staggered in relation to one another. From the shape and attachment of the lugs it will be seen that as they are staggered on the spar and in relation to one another, the spars will, when in place, come in line with one another. On one of the outer faces of the forked lug a piece is left solid, and is shaped to receive the rounded end of the opposite lug. This has probably been done in order to reduce the shearing stress on the pin securing the lugs to the cabane.
   In a previous issue reference was made to the lateral control of the Albatros, the chief feature of which was, it may be remembered, that the wing-flap crank-lever was horizontal, as in so many other German machines. The control cables for the wing-flaps are, therefore, arranged in a somewhat unusual way. The details of this arrangement are shown clearly in Fig. 30. From the front and rear half of the wing-flap crank-lever cables pass down to pulleys enclosed in a casing mounted on the rear face of the back spar of the lower plane. After passing over these pulleys the control cables pass through the rear spar to another pair of pulleys mounted on the tubular compression strut, and hence to the controls in the body. A light framework surrounds the pulleys as shown in the sketch, and forms the support for the hinged inspection doors by means of which the condition of the pulleys and control cables may be examined. The tension of the wing-flap control cables is regulated by means of turnbuckles inside the lower wing. These turnbuckles are situated close to the side of the body, and are rendered accessible by hinged aluminium inspection doors on the lower surface of the bottom wing. In order to prevent the turnbuckles from catching against the edges of the wing ribs, cables and turnbuckles are surrounded by a tube of aluminium, having on its under side an opening with edges flanged outwards to reduce the danger of a slack control cable allowing the turnbuckle to touch the edges of the opening in the tube.
   As in the majority of modern tractor aeroplanes, the undercarriage of the Albatros is of the Vee type, and is built of stream-line steel tubing throughout. The general arrangement of the undercarriage is shown in 1, Fig. 29, from which it will be seen that only the front pair of undercarriage struts are diagonally braced by cables. Reference has already been made to the claw brake, and to the manner in which it is operated from the pilot's cockpit. In the sketch its general arrangement will be evident. The front and rear struts of the undercarriage fit into split sockets at the top and bottom respectively, from which they may be withdrawn by undoing the bolts of the socket, thus facilitating replacement in case of damage due to a rough landing.
   Front and rear strut sockets are attached to the body in a slightly different manner, as will be seen from the sketches of Fig. 29. In the case of the front strut sockets these are welded to a wide steel strip passing underneath the bottom of the body, thus tending to distribute the load over a greater area of the body. The details are shown in the general arrangement sketch, and in 4, Fig 29. Just inside the strut socket the cup-shaped terminal for the diagonal bracing cables of the undercarriage is secured, while a short distance above the socket is situated the attachment for one of the main lift cables. This ball and socket joint, which is used with slight variations on nearly all German machines, appears to be almost the only fitting that may be truly said to have been standardised by the Germans. It is made in a range of sizes, no doubt all made to some uniform standard, so as to render it applicable to a number of different types of machines. The details of the fitting are indicated in 2 and 3, Fig. 29. The base plate securing the hemispherical socket to the body or whichever part of the aeroplane the terminal happens to be attached to, is recessed, probably by stamping, and into this recess fits the flange of the socket. The socket itself is free to turn in the circular recess of the base plate, thus allowing the cable to accommodate itself to any angle desired. The end of the turnbuckle has two flats on its shank which prevent the strainer from turning. For purposes of adjustment the slot in the socket is enlarged at its inner end so as to allow the strainer to turn when in a position at right-angles to the base plate.
   The attachment of the rear chassis strut to the body is shown in 5, Fig. 29. The base plate to which the strut socket is welded is of angle section, and is secured, via brackets as shown, to steel strips running across the body, and which take the tension of the lift-cables. This arrangement is somewhat similar to that of the lower wing spar attachment, which we described in a recent issue.
   The lower ends of the two Vees are formed by short lengths of bent tube of slightly larger dimensions than the struts themselves, for which they form sockets. The details will be evident from the sketches and hardly need any explanation. Running across the undercarriage parallel with the axle are: in front a compression tube, and behind a stranded cable.
   A steel strip protects the rubber shock absorbers from contact with the ground, and a padding of leather is interposed between the axle and the bottom of the Vee. The upward travel of the wheel axle is limited by a short loop of cable, against which the axle comes to rest after travelling the permissible amount.