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

Pfalz Experimental D Type
   Although not confirmed, this machine is thought to be the prototype for the D XII. It may be seen to be a combination of D III type fuselage and D XII wing cellule, with ear-type radiators mounted on the fuselage sides between the wings. Engine, 180 h.p. Mercedes D IIIa.


Pfalz D XII
  
   After a fairly long series of prototype single-seaters, both biplane and triplane, the next Pfalz fighter to see anything like quantity production was the D.XII, which appeared at the June 1918 fighter trials at Adlershof, in both Mercedes D.IIIa and B.M.W. III engined models. Its appearance had obviously been influenced by the Fokker D.VII, but in construction it could not have differed more radically. As was the case with all competing machines, the D.XII was flown by crack pilots from the Front Line Jastas. It is known that at least two expressed approval of the Pfalz machine, Ernst Udet and Hans Weiss, and it has been inferred they received some monetary gain from Otto Kahn, who was responsible for the Pfalz finances. This may or may not have been true, nevertheless a production order was placed to bolster Fokker D.VII supplies, which were not available in the required quantities due to the high rate of attrition of fighter aircraft at this late period of the war. Paradoxically, although it differed so drastically in appearance from its precursor, the D.III, in constructional methods it was greatly similar.
   Much of the propaganda which had extolled the Fokker product as a "world beater" had led all German fighter pilots into wanting a D.VII. When the practically unheralded Pfalz D.XII began to appear in the Jastas from August in 1918 pilots regarded it askance. Nevertheless it was an extremely good aeroplane, equal to the Fokker D.VII in many respects, and in diving capacity, at least, it was superior. Pilots soon adapted themselves to it, and even began to like it. Unfortunately its double-bay rigging, although ensuring an excellent strength factor, was understandably unpopular with ground crews, due to the additional work it made.
   The pleasingly contoured fuselage, like the D.III, was a semi-monocoque based on a framework of spruce longerons and plywood formers. It was spirally wrapped with two layers of three-ply strip about 31 in. wide and applied in opposite directions, being finally covered with fabric and doped. The Mercedes D.IIIa engine was installed with a frontal "car" type radiator and mounted on top of the front end of the engine bearers. The cylinder block was cowled in with metal side panels above engine bearer level, which had adjustable cooling slots punched in them. The collector manifold exhausted sideways to starboard. A small metal chin cowling faired off the underside of the radiator, otherwise the fuselage was all wood, and tapered gracefully to a vertical knife-edge aft.
   The fin surfaces of the tail were the opposite of those of the D.III, the vertical fin now being of welded steel tube and fabric covered, while the rounded tailplane was a wooden structure of symmetrical section and covered with a thin plywood skin. The spars went right through the fuselage, and the tailplane could not be adjusted for incidence, neither could it be removed! Control surfaces were all of welded steel tube and fabric covered. The balanced rudder continued the rounded profile of the fin, and the split elevators were generous in area and of approximate rectangular shape, with large overhung horn-balance portions.
   Both wings were of equal parallel chord and only slightly raked at the tips; the upper wing was of slightly greater span. Construction was almost identical in detail to that of D.III wings, although an additional solid spruce spar ran through between the rear main spar and the trailing-edge wire. To this the ailerons were hinged on the upper wing; these were of steel-tube framing and of extremely high aspect ratio; overhung balance portions made them light to control and imparted a very good rate of roll to the D.XII. Another addition to the top wing as compared with the earlier machine was the inclusion of additional false rib strips extending only to the front main spar and spaced between the main rib and the false rib strip that extended back to the rear spar. Again the upper wing was a one-piece structure without dihedral and the lower wings were attached to the carefully molded root fairings with 1 1/2 degrees of dihedral.
   Bracing of the wing cellule was of great robustness. All struts were of streamlined steel tube, those of the center-section being "M"-shaped and the four sets of slightly splayed interplane struts of "N" pattern. A conventional vee-type undercarriage chassis of streamlined steel tube was fitted, and the axle had spiral steel-spring shock absorbers. A stout, steel-shod, ash tailskid was mounted forward of the sternpost and internally sprung with steel springs.
   Rudolph Stark, who commanded the Bavarian Jagdstaffel 35, which together with Jastas 23, 32 and 34 formed the Bavarian Jagdgeschwader IV commanded by Edouard von Schleich, has reported that when Pfalz D.XIIs were received by his unit early in September 1918, to replace the war-weary Albatros D.Vas and Pfalz D.IIIs, they were initially looked upon by the pilots with dismay. He nevertheless goes on to say that when the pilots had thoroughly familiarized themselves with the type-those that survived those hectic days long enough to do so, that is-were able to give a good account of themselves and to cope with the Camels, S.E.s and Dolphins of the British without undue disadvantage.
   Undoubtedly the Pfalz D.XII's worst enemy was the eulogistic propaganda that had surrounded the earlier Fokker D VII, coupled with its own unannounced, almost mysterious, debut. While the Fokker product had been lauded to the skies, the Pfalz was a completely unknown quantity to pilots, and therefore at an immediate disadvantage. There is no doubt it was a good machine: well designed and carefully constructed. If the war had lasted longer it would most likely have emerged from the shadow of the Fokker D.VII to stand upon its own merits.
   The Pfalz D.XII was supplied to Jastas 23, 32, 34, 35, 64, 65, 66, 77, 78 and 81, as well as to home-defense fighter units. By October 1918. there were 180 Pfalz D.XIIs in service on the Western Front.
  
  
Description: Single-seat fighter
Manufacturer: Pfalz Flugzeug-Werke G.m.b.H. Speyer am Rhein (Pfal.)
Power Plant: One 160 h.p. Mercedes D.IIIa 6 cylinder in-line water-cooled engine developing maximum 180 h.p.
Dimensions:
   Span 9.0 m. (29 ft. 6 3/8 in.)
   Length 6.35 m. (20 ft. 10 in.)
   Height 2.7 m. (8 ft. 10 1/4 in.)
   Area 21.7 sq.m. (236.3 sq.ft.)
Weights:
   Empty 716 kg. (1,571 lb.)
   Loaded 897 kg. (1,973.4 lb.)
Performance:
   Max speed 170 km.hr (106.25 m.p.h.)
   Climb
   1,000 m. (3,280 ft.) in 3.4 min, (2.7 min, with B.M.W. III)
   5,000 m. (16,400 ft.) in 29.9min. (21.0 min. with B.M.W. III)
   Ceiling 18,500ft
   Endurance 2 1/2 hr.
Armament: Two fixed Spandau machine-guns firing forward.

W.Green, G.Swanborough The Complete Book of Fighters

PFALZ D XII Germany

   Participating in the second D-type Competition alongside the D VIII, the D XII was adjudged one of the winning contenders and Pfalz was awarded a contract for 500 aircraft of this type. The four examples participating in the competition each had a different engine, one having a 180 hp Daimler D IIIau, one having a 185 hp BMW IIIa, one having a 195 hp Benz Bz IIIbou and another having a 170 hp Daimler D IIIa. The last mentioned six-cylinder water-cooled engine was adopted for the series D XII, Typen-Prufung taking place on 19 June 1918. Armed with twin LMG 08/15 machine guns, the D XII began to reach the Front in quantity in August 1918, but it was reputedly unpopular with its pilots owing to poor control response. By October 1918, 180 D XIIs were at the Front, but although sturdy aircraft, they did not compare favourably with the contemporary Fokker D VII.

Max speed, 106 mph (170 km/h).
Time to 3,280 ft (1 000 m), 3.4 min.
Endurance, 1.5 hrs.
Empty weight, 1,578 lb (716 kg).
Loaded weight, 1,977 lb (897 kg).
Span, 29 ft 6 1/3 in (9,00 m).
Length, 20 ft 10 in (6,35 m).
Height, 8 ft 10 1/4 in (2,70m).
Wing area, 233.58 sq ft (21,70 m2).

J.Herris Pfalz Aircraft of WWI (A Centennial Perspective on Great War Airplanes 5)

Pfalz D.XII

   The Pfalz D.XII, contemporary of the Fokker D.VII and superficially resembling it, was the final Pfalz fighter to achieve large scale production. The D.XII evolved from a modified D.IIIa with a 'twin-bay SPAD-type wing assembly'. By 1918 the Nieuport sesquiplane configuration was outmoded; a stronger design was needed to enable higher speed with greater reliability. Idflieg had distributed a detailed engineering report on the SPAD 7 fighter to German airplane design departments and Pfalz chose the SPAD wing concept for their D.VIII and D.XII fighters. However, Pfalz did not blindly copy the SPAD wing; unlike the SPAD, Pfalz aircraft used true twin-bay wings, and the D.XII used N-struts not used by SPAD designs.
   It is not known exactly when the D.XII first flew; it missed the First Fighter Competition in January 1918 but was ordered into production in March 1918. Like the contemporary Fokker D.VII, the Pfalz D.XII was designed with a nose radiator. Pfalz had used a nose radiator successfully in its earlier E.V and D 4 fighters. However, the radiator chosen for the D.XII was designed with vertical tubes instead of a more common honeycomb configuration, and when warm weather arrived during flight testing, problems arose and the radiator had to be redesigned. This delayed acceptance of the first production D.XII fighters until June 1918. Again Pfalz was behind its rival Fokker; the first Fokker D.VII fighters reached the front at the end of March, three months earlier than the D.XII, and it was the docile yet highly maneuverable Fokker D.VII that established a fearsome reputation.
   Leutnant Rudolf Stark, CO of Jasta 35b, claimed 16 victories, 11 of which were confirmed, while flying the Pfalz D.III, Fokker Dr.I, and Fokker D.VII. His Pfalz D.III is illustrated here in photos and the replica Fokker D.VII in the USAF Museum is in Stark's colors as Staffelfuhrer of Jasta 35b. In his book Wings of War, Stark said:
   "On September 1, 1918, we [Jasta 35b] were scheduled to receive new aircraft; they were to be the Pfalz D.XII. We hesitated to accept these machines and only after much discussion and long telephone conversation did we finally agree to take the D.XII. Every pilot climbed into the new machine with pre-conceived notions and immediately voiced all manner of complaints. No one wanted to fly the Pfalz on his own accord, and those who were assigned the D.XII were reluctant to fly the machine. Later on pilots did all right in the D.XII. In fact, it climbed well and could fly along with the Fokker D.VII in all respects, and in a dive it was a bit faster. But in turns and combat it was slow and could not compare with the Fokkers. The Pfalz was a sluggish work-horse which fought the bridle and had to be controlled with a strong halter."
   Furthermore, the Pfalz D.XII, with its twin-bay wing and wire bracing, was not as popular with the ground crews as the single-bay, essentially wireless Fokker D.VII.
   The Pfalz D.XII was designed for the Mercedes D.III/IIIa engines of 160/180 hp, the same engines used in most Fokker D.VII fighters. However, the superior BMW D.IIIa was provided in small numbers to both manufacturers; Fokker received 223 BMW engines from April through October 1918 while Pfalz received 84 BMW engines from July through October. Interestingly, no photos of operational D.XII fighters show the BMW engine, giving rise to the suspicion that the BMW engines were removed from the D.XII fighters and installed in Fokker D.VII fighters.
   Other engines tested in the Pfalz D.XII included the 195 hp Benz Bz.IIIbou V-8 and the 195 hp Mana.IIIv. The Benz did not develop full power and delivered disappointing climb, whereas the Mana.IIIv provided an excellent climb rate. However, the war ended before the Mana.IIIv could be mass produced.
   In summary, the Pfalz D.XII was a good aircraft with which to replace the obsolescent Albatros D.III and D.V/Va and Pfalz D.III/IIIa fighters that were still at the front in mid-1918. However, the D.XII needed the superior BMW D.IIIa engine to reach its full potential, and it had the misfortune to reach the front after the exceptional Fokker D.VII, to which it was inferior in maneuverability.


Pfalz D.XII Pilot Comments

   Comments on the Pfalz D.XII from the Jasta 71 war diary maintained by Joachim von Hippel:
   6.9.18: I was appointed Technical Officer of the Squadron and all aircraft came under my jurisdiction (he had received Fokker D.VII 4483/18 on 18.8.18).
   12.9.18: This is my birthday, and the squadron was assigned new Pfalz D.XII. These aircraft were extremely difficult to fly and the under-carriage easily breaks when landing. To put it short and sweet, my flight had absolutely no use for these boxes.
   16.9.18: Flying Pfalz D.XII 2675/18, I crashed and heavily damaged the aircraft on landing. Soon after this, Vzfw. Sieg crashed from a low altitude over the field and was immediately killed. As Squadron Technical Officer, I made and forwarded the following report at once to the proper authorities:

   Habsheim Airfield
   17 September 1918
   The scouting single seater, Pfalz D.XII, was assigned to Jasta 71 for testing in combat and is herewith rejected for the following reasons:
   1. Despite the use of a high compression motor, the aircraft climbs very poorly beyond 3,000 meters.
   2. When banking the aircraft into a turn, normal altitude cannot be maintained since the sluggishness of the controls in the turn forces the aircraft to lose 150 meters. In combat against two French Breguets, the Pfalz D.XII lost excessive altitude, and when attempting to regain combat position in a climbing turn, the aircraft then slides off. If the pilot is successful in correcting his flight line position from a climbing turn, the aircraft then shudders excessively, which can only be corrected by falling off into a slight dive. [Author's note: The shudder referred to is most likely a stall buffet; going into a dive would increase speed above the stall, eliminating the buffet.]
   3. Takeoff roll is extremely long, and landings with the Pfalz D.XII are very difficult and almost always end with the destruction of the machine.
/s/ H.J.von Hippel Leutnant and Technical Officer

   Bavarian Staffels occupying the Habsheim airfield and flying the same aircraft have been observed, on a number of occasions, to crash the Pfalz D.XII on landing through no fault of their own.
   23.9.18: We have nicknames for our machines: Ede for Oppenhorst's and Lude for my equipment. The names were originally inscribed on our Pfalz D.XIIs and they are now carried on the fuselage of the Fokker D.VIIs.
   The war diary of Jasta 36 reports that this unit, being very desperate for aircraft, on October 4, 1918 went to pick up some eight Pfalz D.XIIs from a nearby Flag Park. The engine plugs had been fouled by "used oil" and had worn rings,- the engines needed to be cleaned, taking precious time. On 8 November the Jasta retreated to Lierme, and because of bad weather the eight Pfalz machines could not be flown and were burned! Thus did they value their Pfalz D.XII aircraft.
   From Jasta 43 pilot Josef Raesch's diary (Vol.8, No.4 of Cross & Cockade} about his Pfalz D.XII:
   13 August 1918: I have been issued a new plane, but instead of being a Fokker D.VII, the machine is a Pfalz D.XII. It is alleged to be a fine airplane.
   14 August: A flight with the Pfalz did not satisfy me at all. The machine is clumsy in turns and does not climb well.
   15 August: After two more flights with the Pfalz D.XII, I am very unhappy that I must fly it. The machine will not keep with the others in formations flying . (Note: the rest of the Jasta had D.VIIs.)
   16 August: At 10:00 in the morning, we started for a sortie.

   Contrary to my first opinions, I get along well with my Pfalz when flying in formation. The squadron had a short combat with two E.A. working machines, but they beat it in time.
   Around noon time, we really had an experience. More than 80 E.A. arrived above our airdrome and, in spite of heavy A.A. fire, they dive-bombed us and fired incendiary ammunition into our hangars and airplanes... Flames were everywhere... Three of four machines, Schobinger's, Ruggeberg's, and my Pfalz D.XII were burning... The Kofl., Hptm. Sorg, arrived in the evening to look at the mess. He told us we could not count on new airplanes for quite a while. This was very depressing news for all of us."
   Later, apparently, Raesch got a Fokker to replace the Pfalz.
   Allied pilots who flew the Pfalz D.XII post-war were generally not impressed. The question is, what condition were these aircraft in at this time?

----
From: No 1 (Fighter) Squadron
Lt.R W Ryan Canadian Air Force Shoreham by Sea, Sussex
30th May 1918
To: Adjutant
No 1 Fighter Squadron
Canadian Air Force
Sir,
   I have the honour to make the following report on the Phalz (sic) D.XII which I flew from Chandos to Chingford.
   The plane is heavy on the controls, and is very clumsy in manoeuvering in the air. It has a speed of only about ninety miles per hour and is, in my opinion, dud as a scout airplane.

I have the honour to be Sir, your obedient servant.
(signed) R W Ryan
Lieut.

----
From: Capt. C.P. Falkenberg, DFC
No 1 Squadron CAF
To: Officer Commanding, No. 1 Squadron, CAF
Sir,
   Having flown the Phalz (sic) yesterday I beg to submit the following report on its performance.
   1. Although this machine has the same engine as the Fokker D.VII (180 Mercedes) its performance cannot compare with the Fokker in speed, climb, or manoeuver ability (sic), it takes a long run to get off the ground and climbs slowly, it is decidedly heavy on the control compared with a Fokker and turns badly to the right, a fairly quick turn can be made to the left.
   I cannot give any figures as to its performance as the machines I flew had practically no instruments. This machine cannot compare with any of our present day scouts or even the scouts we were using at the end of hostilities.
   I am of the opinion that this machine would do better with a more powerful engine.

I have the honour to be Sir, Your obedient servant.
(signed) C.F. Falkenberg Capt.

----
Shoreham
27-5-19
Ref FL/CAR/28/
No 1 (Fighter) Squadron Canadian Air Force Shoreham by Sea, Sussex 31st May 1919
Officer Commanding
No 1 Canadian Wing, RAF
Shoreham
PHALZ (sic) SCOUT
Reference the attached letters.

   These two officers flew the Phalz (sic) scout, which was this week delivered to Chingford and their reports speak very unfavourably of this machine from a practical standpoint.
   Capt. Johnson MC and myself have also flown this type of machine and both have formed a very bad impression of it as an aeroplane.
   In view of the above I should not recommend taking more of this type of machine back to Canada than is now being packed.

(signed) A.E. McKeever
Major
Commanding No 1 (Fighter) Squadron Canadian Air Force

----
   A strongly contrasting evaluation of the D.XII comes from Flying the Old Planes by Frank Tallman, Doubleday and Company, 1973. Tailman was a noted movie stunt pilot and had extensive flight experience in a large number of aircraft. Tailman purchased a badly deteriorated Pfalz D.XII from the Jarrett collection, which was then rebuilt by Robert Rust. Tallman found his rebuilt Pfalz D.XII to be fast. "The flight was fast, and I ran away from a PT-19 as if it were moored... Without an airspeed indicator, my speed was arrived at by pacing other aircraft. Control response in the air was precise, and fast on elevators and rudders, but as in some of the spade-grip British aircraft, the aileron movement was restricted, and the rams' horn [on top of the control stick] kept hitting my thigh. Visibility was excellent and wide-open airspeed appeared to be better than 120mph. The climb, as with many World War I planes, appeared flat, but was actually better than a thousand feet a minute, and I easily climbed away from most of the civilian aircraft... Coming, as it did, late in the war, the Pfalz stacks up pretty well when measured against other types I have flown. Its speed above 120 mph will run away from the SPAD, Fokker D.VII, or SE5. Acrobatically it is clumsier and larger than any of these airplanes and with a slow roll rate, only loops seem pleasant. Diving speed must also have been great enough to run away from nearly anything... In play dogfighting with our other World War I aircraft, the speed of the Pfalz seemed to be its one redeeming grace."
   Tallman's comments seem to confirm the importance of the aircraft's condition. Wooden aircraft deteriorated quickly in the European damp, absorbing water which weakened the airframe, made it heavier, and distorted its structure, further reducing performance and handling.


Pfalz D.XII Specifications
Engine: 180 hp Mercedes D.IIIa
Wing: Span Upper 9.00 m
Span Lower 7.90 m
Chord Upper 1.40 m
Chord Lower 1.40 m
Dihedral Lower 1 deg
Gap 1.46 m
Stagger 0.42 m
Area 21.7 sq m
General: Length 6.35 m
Height 2.70 m
Empty Weight 712 kg
Loaded Weight 892 kg
Maximum Speed: 180 kmh
Climb: 1000m 3.5 min
2000m 8 min
3000m 14.5 min
4000m 25.1 min


Pfalz D.XII Production Orders
Order Date Quantity Serial Numbers
February 1918 200 1370-1569/18
April 1918 400 2400-2799/18
April 1918 150 2850-2999/18
(October 1918) (100) (9600-9699/18)

Журнал Flight

Flight, April 24, 1919.

THE PFALZ (D XII) SINGLE-SEATER FIGHTER
[Issued by Technical Department (Aircraft Production), Ministry of Munitions]

   THIS aeroplane, which is allotted G/H.Q./6, was brought down near Dury, on 15/9/18, by Lieut. Cameron (No. 1 Squadron) and Capt. Staton (No. 62 Squadron).
   Although in construction it is strongly reminiscent of the Nieuport-like type of Pfalz, the design of this machine is entirely new, and is of considerable interest.

General Design
   As will be seen from the general arrangement drawings the D XII Pfalz has a car-type radiator in front of the engine, and wings which have two bays a side. The lower planes are faired off into the body in the characteristic Pfalz way, but the fin, which in the earlier model was built of 3-ply as an integral part of the body, is now a separate fitting.

Area of upper wings (without ailerons) 104.8 sq. ft.
Area of lower wings (both) 117.6 sq. ft.
Area of aileron (one only) 8.4 sq. ft.
Area of balance of aileron .8 sq. ft.
Area of elevators (each) 8.4 sq. ft.
Area of balance of elevator (one) .6 sq. ft.
Area of rudder 8.8 sq. ft.
Area of balance of rudder .4 sq. ft.
Area of tail plane (both sides) 16.0 sq. ft.
Area of fin .'. .. 4.4 sq.
Area, of body (horizontal) 32.8 sq.
Area'of body (vertical) 53.6 sq. ft.
Engine 180 h.p. Mercedes
Petrol capacity 18 3/4 gallons.
Guns Two Spandau (fixed).

   The portion of body 3-ply which bears an inscription regarding weight and permissible load is missing.

Wings
   The flat upper plane is built in one piece as before, but the centre section contains neither gravity tank nor radiator, and the tips are no longer heavily raked. The two ailerons of high aspect ratio are very similar to those of the D VII Fokker, as are the placing of the radiator and the form of the interplane struts.
   The lower planes, which are attached to a"kind of" centre section that may be said to grow out of the body, are of the same chord as the upper plane, and only slightly shorter in span. The lower planes possess a dihedral angle, in this case of 1 ?#, and the two pairs of interplane struts on each side slope outwards.
   The attachments of the lower plane to the body are unchanged. From Fig. 1 it will be seen that the spars are cut down to circular section at their extremities, and a piece of steel tube is bolted over.
   A lug on the fuselage has a-circular-section base round which the open end of the tube on the spar fits, while the lug itself is pinned into the fork on the spar in the usual manner. Both front and rear spars are attached in this way.
   Fig. 2 shows the upper aerofoil section compared with that of the R.A.F. 14, which is shown dotted. It will be noticed that the two sections approximate more closely than was previously the case.
   The wing construction of upper and lower planes is similar. Each lower wing contains eleven ribs, spaced at equal intervals of approximately 13 1/2 in. The wood leading edge of the plane is not of the usual "C" section, but is more solid, as will be noticed from Fig. 3. The spars retain the former Pfalz design, but the section is of a squarer shape than formerly, and the flanges are not spindled. Dimensioned sketches are given in Fig. 4, and the upper and lower plane spars are exactly similar. At those points where the strut attachments occur, the spars are solidified by the insertion of small blocks of wood, as shown in the lower sketch of Fig. 4. The various components of the spars are very strongly glued together with a casein cement, and fabric is glued round the whole.
   The tape lattice work that was found in the old-type Pfalz between the spars, and between the rear spar and trailing edge is no longer present, but a vertical rectangular-section strip of wood lies parallel to the rear spar between that member and the trailing edge, and strips of wood are tacked on to the leading edge, and on to the two spars, and finish just behind this strip. These false ribs are placed midway between the true ribs, and the space between each false and true rib is again bisected by another strip. These pieces simply pass from the leading edge to just behind the front spar, and are built up with a vertical strip so that the whole is of T section. The ribs are of 2 mm. 3-ply, with flanges tacked on in the usual way, and are lightened to the extent shown in Fig. 3, which explains clearly all the features just described. The trailing edge is of wire, and each rib has fabric sewn over it. There are twelve steel compression tubes in the upper plane, and five in each of the lower planes. The bracing varies from steel tie rods of 5 mm. diameter to 12-gauge piano wire.

Ailerons
   The ailerons, which are fitted only to the upper wings, are very similar to those of the D VII Fokker. They are balanced, and their high aspect ratio can be judged from the general arrangement drawings. They are constructed of light welded steel tube, and have the usual welded-up curved aileron lever, which works in a slot cut in the plane. The hinges by which the ailerons are attached are very simple. A length of 3/16-in. mild steel rod passes through eyebolts fixed alternately to the wing and aileron, and is secured at one end by a knob, and at the other end by a split pin. Fig. 5 shows how strongly the false spar, to which the aileron is hinged, is coupled to the rear spar.

Struts
   All the interplane struts of the D XII are of streamline steel tube, and not of wood as before. The centre section struts take the form of two "M's," as is clearly shown by the side view in the scale drawings. A slight adjustment is possible at the three central points, by the means already mentioned in the report on the Fokker biplane, i.e., there is a nut welded to the point of the strut, and a ball-headed bolt is screwed in. The ball, which is drilled, fits into a pierced round socket, and a small bolt locks the joint.
   The interplane struts are of precisely similar design to those of the D VII Fokker, and are of N-shape when, seen from the starboard side of the machine. They slope outwards from bottom to top, but, since the spars are equal distances apart in top and bottom planes, the front and rear limbs are parallel. They are attached to the spars by similar joints to those of the centre section, but in this case the strut carries the cup, and the spar has the ball-headed bolt passing through from top to bottom. Fig. 6 shows the spar fitting, and explains the manner in which the bracing is fixed by a dome held down by the bolt. The diameter and width of the struts, both centre section and interplane, are marked on a diagram, Fig. 7. The gauge of the metal has not been measured.
   The wings are braced with the usual flying and landing cables, and besides these it will be noticed from the scale drawings, that a lift wire is fitted between the lower rear spar and fuselage joint at the lower end, and the upper rear spar and centre section strut at the upper end. The lower front spar root is also joined by a cable to a lug fixed a few inches from the front of the engine bearers.

Fuselage
   It is interesting to note that, although many drastic alterations between the D III Pfalz and the new type have been made, the method of construction employed for the fuselage has not been changed.
   The body is of oval section, deeper in proportion to its width than before, and has eight lightened longerons, to which are fixed lightened cross bulkheads. Over this framework, two thin 3-ply skins are tacked spirally, as was described in the D III Pfalz report. The body is entirely without internal wire bracing. There is a strong bulkhead immediately behind t h e engine, and forward of this the 3-ply skin drops almost to the level of the engine bearers, as may be seen in the photographs. The sides of the engine are enclosed by aluminium cowls, and t he front is covered by the radiator. An aluminium cowl rounds off the lower part of the nose, and joins the 3-ply of the body.
   The pilot's seat is missing, but it was supported on a steel tubular framework, which remains, and is illustrated in Fig. 8. It should be noticed from this sketch, that the seat is adjustable both horizontally and vertically, there being three possible positions horizontally, and two vertically. The pilot's backrest is a simple strip of webbing attached to the sides of the fuselage, and the anchorage points for the safety belt are exactly as on the D III machine. The body tapers consistently towards the rear, and finishes in a vertical knife-edge, about 16 in. deep.

Tail
   The body and fin are no longer integral, as in the D III, but the fin is simply a self-contained unit of welded-steel tube and fabric, bolted into its place. The fixed horizontal tail plane, however, is integral with the body, although the joint between fuselage and tail plane is an abrupt angle. The tail plane spars pass right through the body, and are connected by ribs lightened roughly by the boring of many circular holes.
   Not only is the angle of incidence of the tail plane not adjustable, but the plane is incapable of removal. The camber is symmetrical, and its centre line is not only parallel to, but also in line with the crankshaft.
   The balanced and divided elevators (in the D III the elevator was in one piece) are hinged by means similar to the aileron hinges, and from the sketch, Fig. 10, which shows the manner of removal of the hinge-rod, it will be noticed that the leading edge of the elevator is a steel tube, flattened to a vertical oval in t he unbalanced portion, and to a horizontal oval in the balanced piece. The elevators are constructed throughout of welded steel tube, and the balanced rudder has the same construction.
   The tail skid is a sturdy piece of ash with the usual steel shoe, and is balanced about its middle. The upper half is encased in the fuselage, and the shock absorber is of double coil steel spring.
   Fig. 9 shows the framework construction at the rear of the fuselage.

Undercarriage
   This component was not salved, and in the scale drawings the D III undercarriage has been supplied, as the two are conjectured to be substantially similar. From the sockets on the fuselage, it is clear that the limbs of the undercarriage vee finished in ball joints.
   The following particulars regarding the undercarriage are taken from a French source. It is of the same type as that shown in dotted lines in the scale drawings, but the centre line of the axle is vertically underneath the leading edge of the lower planes, and 31 1/2 in. below this leading edge at the centre section. The track is given as 61 in. in the French drawings.

Engine and Mounting
   The engine, a 180 h.p. Mercedes (reported to be No. 42932, B.N. 827, M.N. 63, guaranteed till 30/1/19), is carried on rectangular-section ash bearers (3 5/16 in by 1 1/2 in.), which are lightened in places to I section. At the front end the bearers project a few inches beyond the U-shaped front bulkhead. Two other similarly-shaped bulkheads support the bearers in the places shown by dotted lines in the side view of the scale drawings, and at the rear the bearers are mortised into the behind-engine bulkhead, so that the end of the bearers are flush with the rear surface of the bulkhead. The top of the bearers is covered on either side with a 3-ply shell which extends to the side of the fuselage. In the three-quarter front view photograph may be seen an aluminium scoop (there is also one on the starboard side), which leads air round the crankcase for cooling purposes. The air escapes by holes which are visible just above the leading edge of the lower plane.

Radiator
   The radiator no longer occupies the position it had on the D III model - i.e., in the centre section - but now closely follows Fokker practice. Fig. 11 shows the shape and construction, and it will be noticed that the whole radiator is situated above the crankshaft. The tank at the head of the radiator is of sheet brass, covered with an aluminium lacquer.
   The construction, it will be observed, is very simple. A large number of oval-section tubes of thin brass (9 mm. by 4 mm. cross section), are arranged vertically between the header tank and the radiator bottom, and are supported by two intermediate shelves. The tubes are staggered, and have their cross section inclined at a slight angle to the line of flight, so that the air currents have no straight path, but must impinge upon all the tubes in their course through the radiator. There is a peculiar aluminium "blinker" on the starboard side, permanently fixed edge-wise to the line of flight. Its probable purpose is to prevent the propeller swirl from altogether missing the starboard part of the radiator, by deflecting the current.
   The fact that it is fixed on the starboard side, and that the propeller turns in an anti-clockwise direction when seen from the front, gives support to this view.
   Two aluminium shutters are fitted behind the radiator, one each side-the tops can be seen in Fig. 11 - and are worked positively and independently by means of cables.
   The radiator is supported by two sheet-steel brackets, which are fitted to the foremost bulkhead, a few inches above the engine bearers. (See three-quarter front view photograph.)

Petrol System
   As in the D VII Fokker, both petrol tanks are inside the fuselage. It will be seen that the seat is placed rather far back, and in connection with this, it is remarked that the main petrol tank (sketched in Fig. 12) is placed low down in the fuselage underneath the rudder bar, and is covered with a 3-ply foot board. Its capacity is 16.1 galls. The auxiliary tank is slung from the gun bearers, as shown in Fig. 14, and has a capacity of 2.6 galls. This gives a total petrol capacity of approximately 18 3/4 galls. Both tanks work under pressure. The usual Mercedes oil tank is present, and holds, roughly, 2 galls.
   The throttle is a simple lever, without quadrant or ratchet, which is coupled to the carburettor by light gauge steel tubing, and there is no sign of there having been any inter-connected throttle on the control lever. The welded exhaust pipe points outwards and downwards, and is visible in several illustrations.

Controls
   The stick and its connections are both clearly explained by the sketch (Fig. 13). It will be noticed that only the gun triggers are found near the handles. The rudder bar is precisely similar to that of the D III Pfalz, and has the same adjustment. From the photographs it will be noticed that the cables are enclosed in the body for the greater part of their length and that the upper elevator cable passes right through the fixed tail plane. The aileron cables pass in the usual way through the lower wings, and are protected there by rolled tubes of varnished paper. The place where they leave the lower plane and pass upwards to the aileron lever is marked in the drawings and photographs and the pulleys at this point are of aluminium, and are neatly enclosed in cases of light-gauge sheet steel.

Armament
   In common with the undercarriage and many instruments, both guns had been removed before the machine was inspected, but they were obviously of the Spandau type, fixed, and firing through the propeller path by the usual clutch and synchronizing gear. The triggers are on the control lever, and are illustrated in Fig. 13. As in the Fokker biplane, two strong steel channels are fitted under the guns, and over the engine. They are visible in all three photographs, and in the scale drawings. The double ammunition box is of sheet aluminium, but has a tinplate top, and holds 400 rounds for each gun. It would appear that links were used between the cartridges, as no special receptacle for the usual web belt could be found. A link and cartridge-case deflector is fitted to the top of the cowling.

Instruments
   These were not salved, and all that can be definitely stated is that the compass was of the Pathfinder type, and was fixed inside the cockpit. No dashboard was used, but the instruments had been distributed around the cockpit. It is reported that the pilot was provided with a parachute, which was folded into the seat, and acted as a cushion, but these fittings were not salved.

Propeller
   This is of Heine make, No. 26206; diameter 2,780, pitch 2,000. It has eight laminations of mahogany and walnut.

Fabric and Painting
   The fabric is of the usual colour-printed variety, and the body was painted dark purple from nose to rear of engine; bluish-grey to pilot's cockpit; and a dark green shading into a light pea-green extending to the tail. The fin and rudder are creamy-white, as is the part of the body above the tail planes, but the tail planes themselves, and the underneath portion of the body at the tail, are painted in broad stripes of alternate black and white. The photographs help to identify these various divisions.

D XII TYPE-Schedule of Principal Weights

Fuiselage, without engine, guns, auxiliary lbs. ozs.
   tank or oil tank, but with main tank and
   tail skid 257 0
Starboard lower wing, with control cables
   but no bracing wires. Only one side
   fabric covered 46 0
Upper wing, with bracing wires, but only
   one side fabric covered 127 0
One centre section M strut 7 4
Radiator 44 8
Brass oil tank 5 1
Auxiliary petrol tank 7 8
One outer N strut 8 9
One inner N strut 10 6
Fin (covered) 3 2
Aileron (covered) 7 12
Aileron hinge rod 0 8
3-ply tail plane (partly estimated) 19 0
Aluminium nose cowl 3 14
Cockpit cowl and padding 2 6
One aluminium side cowl 1 12
Ammunition magazine 7 12
Two clutches for synchronising gear 5 13
Two gun channels 5 5

The weights of the main components of the earlier Pfalz - D III type - are given below for comparison

Fuselage, without engine, guns, or empennage,
   but with tanks and all fittings 295 0
One lower plane, covered, but without
   bracing wires 49 0
Complete upper plane, covered, with
   ailerons, bracing wires, radiator, and
   gravity tank 225 0
One centre section strut 9 6
One U interplane strut 8 13