Germany's Focke-Wulf 190 presents an apparently strange combination of simple, yet sturdy, construction, paralleled by highly complex components. Analysis of the craft reveals, however, that is has been designed for the pilot and the field maintenance man. What often appears initially to be an unnecessarily complex small unit turns out to be a well-designed, self-contained, and quickly removable unit.
Underlying theory of the entire design appears to be to reduce field maintenance time to a minimum, as though the plane had been created with the idea that it's quicker to get parts off the plane replaced than to repair the parts themselves.
Then, too, the design is such that the craft can be built through widespread use of subcontracting or dispersal plants. The fuselage, for example, is comprised of two major components, the fore section extending from the firewall, or what the Germans call bulkhead No 1, to bulkhead No 8 aft of the pilot's seat, and the aft section extending from bulkhead 8 to the empennage.
The fore fuselage section is the heart of the plane and is, in effect, a double-deck box type structure, with the top section making up the pilot's cockpit and the lower section serving as the fuel tank bays.
The firewall, or No 1 bulkhead, is built up of light sheet steel backed by sheet aluminum alloy riveted to built-up flanges extending from the two top forged engine mount fittings down to forged fittings which serve as attaching points for both lower side engine mounts and the front wing spar.
Longerons run aft from these four points to No 8 bulkhead, where they are spliced to lighter ones in the aft section. Top longerons are 1¾ in wide U-sections made up of 3/16-in thick aluminum alloy and serve as tracks in which the cockpit canopy travels. One hat-shaped stringer on each side, 10½ in below the top longerons, make up the only horizontal stiffeners in the top part of the fuselage. Aluminum alloy sheet, riveted to the lower longerons, forms the cockpit floor, separating it from the fuel tank bays.
Bulkheads in the upper fore fuselage section are not uniformly spaced, nor are they all of the same construction. No 2, of conventional stamped flanged construction, is 12½ in aft of No 1; No 3 some 6-5/8 in farther aft is directly beneath the front windshield base. No 4, also of conventional construction, is 10-5/8 in farther aft. No 5, directly under the rear end of the fixed windshield and above the rear spar fitting, is angle shaped against the skin, and extends above the floor only to the stringer. It is braced by a ¾-in tubular section flattened at each end for riveting to the bulkhead and cockpit floor. No 6 is an A-frame structure, the base of the fore part being 12 in aft of the No 5 bulkhead, the top 18½ in farther aft. The sloping fore part is a channel section in which the pilot's adjustable seat is supported. The vertical member, set 5 in aft of the top, is conventional stamped, flanged construction, riveted to the fore part at the top by a web plate of aluminum alloy. No 7 is conventional construction, set 12 in aft of the rear part of No 6, and No 8 is a built-up stamped flanged member extending the full depth of the fuselage, and forms the joining point of fore and aft fuselage sections.
The lower fore fuselage, or fuel bay section, has but six bulkheads. No 1 forms the front end, being right aft of the front wing spar. No 2, which is in reality a contour rib, is 10 in aft and is a continuation of No 3 from the upper section. Lower No 3, set 5-7/8 in farther aft, is also a contour rib and joins the longeron between Nos 3 and 4 of the upper section. No 4, of built-up web construction, is the tie-through member between rear spar fittings, and separates the two fuel tank bays. No 5 is set below the forepart of the A-frame No 6 of the upper section and, like lower No 6, which is set 11 in aft, is contour-rib type.
One belly skin panel, attached to longitudinal and transverse angle shaped stiffeners, is attached to the lower fuselage section by nine screws along each side and five on each end, thus giving quick access to the two self sealing fuel tanks, which are suspended from the contour rib-bulkheads by heavy web straps.
On the upper fore fuselage section, immediately aft of the top engine mount fittings, the fuselage structure is flat, forming a shelf to which are bolted mounts for the twin 7.9-mm machine guns that fire through the propeller. Back of this gun mount shelf the fuselage sides extend up to form the base for the windshield, the front panel of which is 1¾ in bulletproof glass.
At the base of this front panel is hinged the fairing to cover the guns just mentioned. This fairing, which hinges up and back for access to the guns, is of "waffle" type construction, with the two skins being fastened together by one rivet in each inner skin dimple. Three heavy locking toggle switches typical of those installed throughout the plane are used on each side to hold the fairing in place.
Such heavy cowling and easily removable hinges to keep it in place naturally adds what seems unnecessary weight. It is, however, in keeping with the apparent design theory; the cowling is always on the craft ready for locking and a quick takeoff. It is heavy enough to stand hard wear, in fact, the side panels swinging downward around the engine mount are used as work platforms. Too, in case the cowling is bent a bit, the toggles are sturdy enough to pull it into place for quick locking.
Cowling on the FW-190 averages about 1.75 lb per sq ft, compared with 1.25 for British and American craft, but the German's persistent use of the type indicates their belief the beatings it can take and the speed with which it can be locked in place make it worth the added weight.
The cockpit cover and its fairing are built as an integral unit. Base of the structure is a 5/8-in tubular member bent into an inverted U at the front to fit into the windshield. The plastic glass of the cover is mounted between two strips of buna and a flat aluminum strip, held by screws driven into self-locking nuts in the tube. At the rear of the plastic glass a stamped, flanged aluminum A-frame sets between the tube-frame ends, and is riveted to aluminum alloy fairing mounted on a ¾-in. tube extending aft. The whole structure rides on three ball bearing rollers; one on each side at the front of the plastic glass section in the top fuselage longerons, and one attached to the tube, running in a channel section (which serves as top longeron) set in the fuselage turtle deck.
The cockpit cover can be operated only from inside by a crank attached to a sprocket which engages a pin ratchet attached to the front end of the tubular frame. Emergency exit can be effected by pushing down on a small handle located near the crank. This disengages the sprocket and then, through a series of rods and shafts, releases a latch holding the firing pin. A cartridge explodes and blows the rear end of the canopy backward far enough to let the slip stream get under and pull it away. The explosive charge about the size of a 12-gage shotgun shell is located aft of a silhouette of ¼-in armor plate back of the pilot's head. This armor is attached to the cockpit cover tubular member by links attached to studs welded to the armor plate.
An interesting angle of the cockpit cover is its connection with the radio antenna, which leads in from the vertical fin to and over a pulley set in the plastic glass just behind the armor plate, then over another pulley set in the aft end of the cover fairing, then forward again to an insulated lead-in to the radio mounted just behind No 8 bulkhead. Thus, regardless of whether the cockpit cover is open or closed, the radio antenna has the same tension.
While the cockpit itself does not give the appearance of being overcrowded there is, nevertheless, no waste space. Flight and engine instruments are arranged on two panels beneath the windshield and on horizontal panels on each side, as shown in the accompanying diagrammatic layout. The pilot's seat, the back of which is made of armor plate, is only adjustable up and down 4 in and is designed for seat pack parachutes.
The aft fuselage from bulkhead 8 through 14 is semi-monocoque construction, and is attached to the fore section by a double row of rivets through both skins and the flanged section of bulkhead 8. An examination of several different craft, including more than one model, indicates these two sections are not jig-drilled prior to mating. Apparently the two sections are brought together in a mating jig and both drilling and riveting done there, for variations in rivet locations are readily apparent. This same type of assembly is rather widely used, as will be noted in the discussion of other components.
Bulkheads Nos 9 and 10 of the aft fuselage section are built up in three sections, the bottom ones being heavy channel sections with flat tops to support camera installations. Upper portions of both are conventional stamped flanged construction, riveted together and to the bottom sections.
Numbers 11,12, and 13 are of lighter construction and follow conventional practice, being built in halves and riveted together at top and bottom. No 13 contains a cross tube for lifting the fuselage. In No 12 there is set a fabric panel to keep dust from seeping forward to the radio, camera and master magnetic compass with its contact for control of the repeater on the instrument panel.
Bulkhead No 14 is heavy flanged construction for bolting the empennage to the aft section.
There are two upper side channel-shaped longerons, riveted to those from the fore fuselage by 6-in splices and they extend to aft of bulkhead No 11. A channel-shaped top longeron extends the full length of the aft section, between bulkheads 8 and 11 serving to support the cockpit cover fairing track. There are six Z-shaped stringers with rolled edges on each side of this section of the fuselage and five in the bottom in addition to two heavy U-shaped stringers where side and bottom sections are joined.
The aft fuselage skin like that in the fore section is slightly lighter than our 24ST, but no evidence of wrinkling was found in the several craft studied. Flush riveting is used on every surface of the craft.
One of the outstanding examples of simple, yet sturdy construction found in the Focke-Wulf 190 is the empennage. It is attached to the aft fuselage section at bulkhead 14 by mating, flanged bulkheads through a series of closely-spaced bolts.
Leading aft from this bulkhead, some 5 in from the top skin, is a stamped flanged rib with lightening holes, extending from side to side and seven and three eighths inches lower is another full-width rib. The stabilizer goes through the fuselage between these ribs.
Both ribs intersect a diagonal member which is the heart of the empennage, for it carries tail wheel loads on the ground and, once the craft is airborne, carries both fin-and-rudder and stabilizer-and-elevator loads.
Starting at the bottom skin 18¾ in aft of the attaching bulkhead, this member extends up and aft 63½ in to the top vertical fin rib (which extends aft to support the top rudder hinge) at the base of the detachable vertical fin tip. Nine inches from this member's lower end, on the aft side, is riveted a fitting to which is attached the front end of the tail wheel drag yoke. On the front face, between the two horizontal ribs previously noted, is riveted a forged hexagonal fitting to which the stabilizer rear spar attaches.
Above the top horizontal rib, on the aft face is riveted a 20-in double channel member which forms the guide rails for the tail wheel retracting unit, which will be detailed later. The channel member is surmounted by a plate bearing a pulley which is part of the retracting unit, and the top fin rib.
The topmost of the two horizontal ribs extends aft of the diagonal member 16¼ in, the middle rudder hinge being mounted at its end. The other horizontal rib, aft of the diagonal, extends downward at approximately 28° from the base of the stabilizer fitting to the bottom of the tail cone to support the lower rudder hinge. A vertical web plate of stamped flanged alloy connects the two ribs at their aft ends.
Below the two horizontal ribs, three Z-shaped stringers on each side run from bulkhead 14 to the diagonal member, and a similar number are employed above.
At the leading edge of the fin, the skin is crimped and riveted together, with a series of 5 diamond-shaped, self locking nuts inserted and riveted between the crimping. The leading edge skin, a single sheet of formed aluminum alloy, can then be fastened in place with flush flat head screws driven into the diamond-nuts. Drilling of the two fin skin surfaces apparently is not a jig operation, for study of several craft showed uneven spacing and lack of rivet alignment. In one plane, as a matter of fact, even a difference in rivet sizes was evident.
Skin aft of the diagonal member between it and rudder hinge points is of the familiar double skin "waffle" construction, eliminating the need for stringers. A triangular inspection door 30 in high by 15 in across the base set in the left side of the fin gives quick access to the tail wheel retracting unit and top of the oleo shock strut. Two screw driven locks are used. The piano hinge springs to keep the door closed. These and the hinge are sealed in fabric.
Apparently deterioration of pilot quality, well-prepared airports, or some other causes have resulted in failures in the empennage, for examination of later models of the 190 reveals that additional web plates have been installed between the horizontal ribs behind and below the stabilizer fitting to better distribute the stabilizer-elevator and tail wheel loads.
The dynamic and mass balanced rudder is built around a single spar of stamped flanged aluminum to which are riveted the three hinge fittings. Leading edge is flush riveted to the spar, and ribs have rounded gusset plates. Trailing edge is also of metal, with the entire unit being fabric covered. Unlike most modern fighters, the 190's rudder trim tab is adjustable only on the ground. It consists simply of a 15 x 1-in metal strip riveted into the trailing edge, with a series of perforations to facilitate bending to the desired degree. Two types of tabs are used; some with slotted perforations, some with round holes.
The stabilizer is full cantilever single spar all-metal construction, built as one unit except for detachable tips. There are seven floating ribs on each side. Stabilizer attaches at the aft edge to the diagonal member of the fin through forged fitting previously noted, and hinges on pins that go into self aligning trunnions, for vertical trim of craft is effected through adjusting the stabilizer.
On the center of the stabilizer's leading edge is a fitting attached to a yoke which, in turn, fastens to a screw jack and electric motor suspended by a ball and socket joint from the leading edge of the vertical fin. This motor, which turns up to 14,000 rpm, has six trains of gears with 533 to 1 reduction. It moves the stabilizer leading edge 4.1 in per min, or over the full arc of adjustment in about 20 sec. A magnetic brake is provided to prevent motor overrunning when current is cut off.
In the stabilizer, as in the leading edge of the vertical fin, the upper and lower skins are crimped and riveted together and the leading edge screwed in place via six of the diamond-shaped nuts. In this unit, too, rivet alignment and spacing are both irregular along the crimped skin.
Elevators, like the rudder, generally follow conventional practice with a single spar, metal leading edge, metal ribs with the familiar rounded gusset plates, metal trailing edge and fabric covering. Despite the fact that the stabilizer is adjustable, the right elevator has a perforated trailing edge trim tab like that on the rudder.
The elevator hinges to the stabilizer at three points and, although all three fittings are different, each hinge has an self aligning ball bearing unit.
A departure from conventional construction shows up in the 190 wing, for it is built as a single unit from tip to tip. Thus, if it is damaged structurally any place between the detachable tips, the entire unit, rather than say, one panel, must be replaced.
The integral center section of the tapering front spar is a very heavy member, for it takes the weight of the two lower side and bottom engine mounts, fuselage fitting attachments, four 20-mm cannon, and main landing gear. At the center line it is a built-up triple-web I-beam 16¾ in deep, reinforced by a heavy vertical channel-shaped member embracing, at its lower end, a forged fitting for the lower engine mount structure, a combined tubular-and-channel truss unit. Between the center line and side engine mounts, set 24 in out, are two vertical hat shaped stiffeners. Engine mount members themselves are of similar shape, but are heavier and are riveted rather than bolted to the spar.
At these side engine mounts the spar is bent forward 14°, with this angle being maintained 64½ in to the main landing gear fittings, from which point it parallels the center section. The bend permits the landing gear to retract in and up ahead of the spar. This section of the spar has, in addition to the cannon ports, three lightening holes and three vertical angle stiffeners.
The triple-web construction continues beyond the bend to just outboard of the port for the barrel of the inboard cannon. Immediately outboard of the landing gear fittings, where the spar again bends, it is reinforced by a heavy riveted gusset extending some 12 in beyond the outboard cannon port, from which point to the tips the spar is single web I-beam with 1½-in lightening holes. For the full length of this outer portion the spar has lips top and bottom to which the leading edge is screwed.
The leading edge, from engine cowl outboard to the landing gear, is built as one unit and is attached by screws to the spar. The main member, just outboard of the gun port, is a double, stamped flanged rib with cutout for the landing gear strut. Two feet farther out is another contour rib of I-beam construction and between them a stamped flanged contour rib. Tip-end of this section also has a stamped flanged rib with cutout for the landing gear strut. Remainder of the leading edge is built as one unit, consisting of formed aluminum sheet reinforced by conventional stamped flanged D-type nose ribs.
Only five 'tween-spars ribs on each side, besides those at the wingtips, are attached to both top and bottom skins. Of conventional stamped, flanged construction, they are located just outboard of the inboard cannon; on either side of the landing gear fittings to form a torque box; on either side of the outboard cannon ports; and at the outer end of the reinforcing gusset around these ports.
The rear spar, a conventional tapering I-beam, extends from top and bottom forged fuselage attachment fittings to the tips, and carries both flaps and ailerons. It is double web for 32 in from the fuselage fittings, single from there to the tips.
It would appear that the rear spar and the top skin panel (forward to the front spar) are built as an integral unit, with blind riveting being necessary only for attaching the five top-and-bottom or “solid” ribs previously mentioned, Three stamped, flanged contour ribs are located between the "solid" ribs and six are utilized between the outer flap hinge and the tip rib. All these ribs have cutouts for Z-shaped spanwise stringers, of which there are nine outboard of the flap, and eleven between the "solid" ribs. Skin aft of the rear spar, above the flap, is a separate subassembly attached by ten contour ribs riveted to the spar web, with one continuous stringer between the spar and trailing edge.
Also built as a unit is the bottom skin panel, which screws to front and rear spars. One contour rib is located at the fuselage attachment fittings, one between the cannon and landing gear ports, and five between the outer "solid" rib and the tips. All these ribs have diagonal cutouts for Z-shaped stringers similar to those in the upper panel.
An interesting development found on later 190 models is the addition of aluminum strips, .032-in thick and ¾-in wide, riveted to the ribs and skin, much like diagonal braces between joists in a house to prevent side sway. This addition has been made to both top and bottom skin panels, and appears to be a modification made in production rather than in the field.
Split type flaps follow conventional practice, with the monospar being made up of a rolled section with beaded stiffeners. Top skin section is cutout in the familiar rounded gusset pattern; ribs are normal stamped flanged construction. Top and bottom sections are riveted together at the leading edge, and the whole fabric covered. With a total span of 7 ft 10 in each, the flaps are built up in halves, the two sections being riveted together adjacent to the middle of three ball bearing hinges. Atop the trailing edge are ten ½-in dia rubber bumpers to absorb vibration between the flap and trailing edge.
Inboard and outboard hinge fittings are castings riveted to the flap spar. The mid-fitting, which also forms the flap actuating arm, is of built up welded construction. Attached to this fitting is a dial reading 0-60°, visible through a hole in the top skin panel, so that the pilot can get an exact reading of each flap position.
Electrically driven by gear trains through a nut to a screw jack attached to the motor mounted on the front face of the rear spar, the flaps move down 60°. The two motors are connected through a relay control box so that neither flap can go more than 3° without stopping to wait for the other to catch up.
Fabric-covered Frise-type ailerons are as light in weigh as they are reported to be on controls. They are built around a channel monospar with beaded vertical stiffeners to which are riveted upper and lower two-layer metal leading edge skins, the inner ones having beaded stiffeners. Aft of the spar there are 10 conventional ribs, with the familiar rounded gussets, and 10 intercostals of stamped flanged light aluminum alloy. These light-weight intercostals are provided to contour the fabric and allow it to be stitched down with wire.
Ailerons are mounted on three self aligning ball bearing hinges at ribs Nos 1, 5, and 9. The inboard hinge at rib No 1 is a cast aluminum fitting into the bottom of which screws a lug and ball bearing collar, running on a tapered pin assembly through the bracket attached to the rear spar. The screw bearing collar is split and the taper jambs it tight when the lock nut is tightened. This makes it possible to get perfect alignment between the hinge, bracket and wing fairing without the necessity of mating parts in jigs. Mid and outboard fittings are cast angle brackets, with roller bearing collar screwing in from the bottom and running on a pin through a bracket in the same manner as the other hinge. In each case, curved shims between the bearing collar and bracket are utilized to eliminate side play while retaining alignment. Balance weight washers are fastened into the hinge slots with a bolt and captured nut riveted to each side rib of the slots.
On the inboard end of the right aileron is a 19¼-in-long trim tab adjustable only on the ground similar to those on the stabilizer and rudder.
Main landing gear is a single-strut oleo shock unit, with conventional torque scissors, attached to a forged steel tapered roller bearing spindle assembly. The front face of the mounting is flanged to bolt to the front spar. Fairing is in three sections; one attached to brackets extending up from the hub, another bolted to the oleo strut and the third hinged at the center of the fuselage. A scale painted on the two fairings attaches to the landing gear tells at a glance if proper pressure about 1,300 psi is being maintained in the shock strut.
Retraction is electric, with a separate unit for each wheel. The motor which turns up 14,000 rpm, is mounted back of the front spar web, with a 3.3:1 reduction from the armature shaft, then a safety centrifugal clutch, followed by two gearless reductions, one 53:1 the other 60:1, giving a total reduction of 10,494:1 in three steps in a unit 14 in long and, at the front end, 7 in in diameter. The last reduction stage at the front face of the spar web drives a 1-3/8 in thick forged steel ring to which is yoked a tapered aluminum alloy I-beam of 13¾ in length. This in turn is jointed to another tapering beam into the lower end of which is screwed a ball and socket joint that attaches to the oleo strut. The forged ring turns outward to lower the wheels and the arms, due to their toggle action, lock the landing gear down. When turned toward the airplane center line, the joint between the I-beams or toggle arms breaks to pull the oleo and wheel up and inward.
It is interesting to not that in down position the oleo struts have not yet reached the perpendicular, but there is no down lock on the gear. The two I-beams form a straight line when the gear is down and this straight thrust, coupled with the high reduction from the motor, appear to suffice for gear down locking.
Small metal contacts through fiber insulation on the faces of the I-beam joints automatically shut off the motor when the landing gear is full down. On the rotating member of the landing gear mechanism there is a small scaled rod which projects up through a ball joint in the top of the wings as the gear goes down so that the pilot can tell the exact position of each wheel.
As gear retracts, the oleo strut just above the wheel contacts a coupling (set in a box-structure mounted on the front face of the front spar) which snaps into place, locks the gear in up position and automatically shuts off the retracting gear motor. The lock is held closed by an electrical latch and releases electrically when the power is turned on to lower the wheels. Unlocking can be done manually, however: the pilot pulls a knob (on the left side of the instrument panel) attached to a flexible cable which, atop the center of the front spar, is yoked to similar cables leading out to each landing gear up-lock box.
The tail wheel is retracted automatically with the main gear. At the joint of the two I-beams on the right main wheel is attached a cable that runs over a pulley set just above the gear spindle, thence inboard to the right side of the fuselage in a conduit through the cockpit back to a pulley on the front of the diagonal "heart" member in the fin, then up over a pulley atop it and down to a yoke set at the top of the tail wheel oleo. Thus, and it's not as Rube-Goldbergian as it sounds, as the main gear joint starts to move up, tension on the cable is transmitted back to the tail wheel retracting mechanism and the wheel is pulled up. A similar cable arrangement is used to pull the camera protecting door open when the landing gear is retracted. The center wheel fairings are held tightly open by a cable system when the landing gear is down. They are closed by the wheel when it is retracted.
The tail wheel itself is mounted in a steel fork which fits into the front end of a heavy steel figure-eight casting which places the center of the yoke 6 in ahead of the wheel center to permit castering. The tail wheel drag yoke attaches to the diagonal empennage member and to this figure-eight casting just ahead of the bottom of the oleo strut, which fits into the aft portion directly over the wheel center.
At the top of the oleo strut is a yoke containing four rollers; two load carrying larger ones set on each side of the center, two smaller locking ones just aft. These rollers run in the channel member (previously mentioned in discussion of the empennage) on the aft face of the diagonal member, and are part of the yoke to which the retracting cable attaches and to which is also attached a coil spring going down and aft to the rib holding the lower rudder hinge. This spring and gravity pull the unit down. At the bottom of the channel the track leads forward, just enough for the larger rollers to fit into the resulting "pocket" so that loads from the tail wheel are transmitted up through the oleo directly against and toward the front of the diagonal rib, thus locking the wheel in down position. When tension is put on the cable from the main gear it starts the smaller rollers up the channel and they in turn pull the larger ones out of the "pocket", to unlock the gear, and then up the track
The tail wheel moves up 20 in, and rubber pads on the axle just outside the fork fit snug against the bottom the fork fit snug against the bottom fuselage skin when it is retracted. A spring loaded "V" cam centers the wheel as soon as the load is released.
An interesting detail of the tail wheel castering unit is this: the pivot is a hollow steel forging, welded to the fork and the hollow space is utilized as a grease reservoir for lubricating the swivel surface, the grease coming out through a 3-in long slot which also serves as the tail wheel lock.
Main landing gear tires are 700 x 175 mm smooth contour and tail wheel tire is 350 x 135 mm, also smooth contour.
Stick-and-rudder controls are generally the conventional push-pull rod and cable type, except that the elevator and rudder controls embody differential bell cranks which give a higher control surface-to-stick or rudder ratio near neutral position, thus tending to smooth out control action at high speeds.
Rudder pedals are stirrup type with heel plates, with the hydraulic brake cylinder an integral part so that exerting toe pressure energizes the system. Distance of rudder pedals from the pilot's seat can be individually adjusted by turning a knurled knob set in the push-pull rod on each side of the cockpit aft of the pedals themselves. There are also four positions for the pedal fulcrum point. Rudder pedal units are suspended from brackets attached to fuselage bulkhead No 2. Push-pull rods lead directly aft through the fuselage up to the differential bell crank which is suspended from the top longeron at bulkhead 13. From there cables lead aft inside the empennage skin and attach to the rudder spar, which is 4 in wide at the middle hinge.
The 21¼-in long control stick is mounted in a cast base in the fuselage floor center between bulkheads 3 and 4. Elevator control is via a tube leading to the right side of the cockpit, then via single push-pull rod to just aft of the pilot's seat to a bell crank from which two double ¼-in cables lead back to a differential bell crank mounted in bulkhead 14, where another short single push-pull rod leads back to a bell crank directly under the stabilizer leading edge and a vertical pus-pull rod attached to the elevator horn on the center of the elevator spar.
Aileron control consists of a tube running forward from the control stick base and actuating a push-pull rod and bell crank set on the front face of the front spar center. From here push-pull rods extend outboard through an idler hinge to change direction corresponding to the 5° dihedral to a point directly in front of the flap operating motor where a bellcrank changes direction aft to the front face of the rear spar. Here another bellcrank changes direction along the rear spar to the inboard end of the aileron where still another bell crank and push-pull rod attaches to the aileron horn. All hinges and connections are mounted on self aligning ball bearings. The bell cranks are all mounted on widely spaced ball bearings so that there is little lost motion even when the bearings get loose.
The Germans' extensive use of ball bearings is particularly evident in the Focke-Wulf 190 controls, for finely built ball bearing units are used not only throughout the complicated differential bell cranks, but wherever moving parts are joined and in all the electric reduction gears and motors.
Aileron stick gearing is 3.2° to the inch; elevator stick gearing is 4.1° to the inch; and rudder pedal gearing is 6° to the inch.
Outstanding control on the craft is the throttle quadrant and its Kommandgerat, or "brain box". Only one lever, mounted on the left side of the cockpit is used. From it a push-pull rod leads forward and down to a bell crank attached to a rod which runs across to the right side of the fuselage to a second bell crank and push-pull rod going up and forward through the firewall to another push-pull rod-bell crank and the tube unit which takes the movement to the left again a few inches (to a point inside the engine mount ring) and another bell crank and push-pull rod which connects with the "brain box", a finely built complicated unit measuring 16 x 16 x 12 in.
As the pilot moves the throttle, and the movement is transmitted through the bell cranks and push-pull rods, the "brain box" automatically makes compensating adjustments for fuel flow, fuel mixture, propeller pitch setting, ignition, and cuts in second stage supercharger at proper altitude. If, however, the pilot desires to make a propeller pitch change without changing other settings, he may do so "manually" by pushing a rocking lever switch set in the throttle. Further details of the "brain box" cannot be revealed at this time.
Another interesting detail of the Focke-Wulf's design is the engine mount ring, a hollow tubular structure which also serves as the reservoir for the hydraulic fluid used in the "brain box". The BMW-801 engine itself was discussed in detail in Aviation for Nov and Dec, 1942, and thus is not included in this discussion of the craft.
All the 190's fuel supply is carried in two self-sealing tanks suspended by fabric straps in the lower fore fuselage section with the fore tank, between spars, holding 61.2 US gal. and the aft tank having a capacity of 76.8 US gal.
Both tanks are filled from the right side of the fuselage, the filler pipe cover plates being quickly detachable flush units. Each tank contains a sealed electric pump. Gages are all electric; the fuel warning light and pump indicator lights being arranged vertically in the center of the lower instrument panel; the fuel supply gages for each tank just to their right; and selector gage to their right. Manually-operated fuel selector valve, however, is on the left of the top instrument panel. Lines from tanks to engine go through the firewall.
Majority of the highly complex electric system components are located to the right of the plane's centerline. On this side, for example, are the distributor, two generators, battery and main junction box with its ground supply connecting plug, this latter unit being located in the aft fuselage between bulkheads 8 and 9.
Wires leading from the removable top instrument panel containing six flight instruments go out through three quick disconnect plugs to the right for power or, as in the case of the dash repeater compass, to the master compass in the aft section.
Two control switch junction boxes are required, one on each side of the cockpit. That on the left contains the throttle quadrant, propeller pitch control, ignition switch, flap and landing gear indicator lights, starter mixture control, stabilizer trim switch and indicator, flap and landing gear switches, primer pump switch and radio. It is built as a removable unit, and wires going out from its front end are led through three quick-disconnect plugs, those out the back end to the main junction box through five lines in two similar plugs.
The right-hand panel contains forward and rear circuit breakers, external battery indicator, fuel booster pump switches and engine starter. Four quick-disconnect plugs are installed in the front end; even in the rear leading to the main junction box.
The electric system is further complicated by the fact that four of the six guns the two 7.9-mm machine guns and the two inboard 20-mm cannon must be synchronized to fire through the propeller. The synchronizing units are mounted behind the engine. Electric leads from them go to each gun.
Wherever possible, wires are grouped when leading from one part of the airplane to another through generous use of quick-disconnect plugs. In general, too, the Focke-Wulf 190 follows the German practice of having wires leading from one part of the plane to another in the same location, so that mechanics working on one aircraft will not have to become completely indoctrinated before being assigned to another make or type.
This article was originally published in the October, 1944, issue of Aviation magazine, vol 43, no 10, pp 127-152.
A PDF of this article, recovered from microfilm, includes 4 photos, 3-view and 43 detail drawings and diagrams, and 1 data table. The PDF also includes an article on the gear retraction system [ HTML ] and an "introduce-the-plane" article on an FW-190A3 in British hands [ HTML ].