Design Analysis of the
Vought Corsair

By William C Hoff
Eastern Editor, Industrial Aviation

Structural details of the F4U-1D whose inverted gull wing set a design precedent

The Vought Corsair, one of the wor1d's fastest airplanes, is an exception to the rule that ship-based airplanes must necessarily be inferior in performance and fighting ability to land-based planes. It has been operated steadily and successfully from aboard ships of the United Nations; and it is, in fact, supplied (under contract with the US Navy) as the mainstay of the Royal Navy's Fleet Air Arm. The US Marines fly Corsairs from land bases in competition with other land-based fighters, and it has gained recognition as an efficient dive bomber, in addition to its abilities as a fighter. Historically, this shipboard airplane was the first fighter to use a 2000-hp engine, was one of the first fighters to revive the use of the aircooled engine, the first of the new heavy fighters, the first airplane to utilize a great quantity of spotwelding to join its structural members, and the first airplane to exceed 400 mph with full military equipment — a performance which it has since surpassed owing to further refinements in design.

It is true that the requirements for airplanes intended for use in ship-board operations are to some extent contradictory to the requirements for those of high-performance fighting ability. For example, the landing speed of the Corsair had to be limited to 85 mph. This fixed the wing loading at 33.3 psf, a lower figure than would normally be desired in a high performance airplane. It also meant that a comparatively large wing was required. At the same time, the wings must fold, and with the wings folded, the airplane must fit the clearances of elevators and between-decks areas of existing aircraft carriers. Consequently, the allowable height of the airplane with wings folded was limited to 17 ft. Since available "head room" on the British carriers is somewhat less than that of US carriers, the folded height (and consequently the span) of the Royal Navy version of the Corsair was decreased by "clipping" the wing tip until it was almost square.

Another problem was presented by the propeller. To efficiently use the high power which the engine made available at high altitudes, a large, comparatively slow-turning propeller had to be provided. The airplane had to be designed to provide sufficient ground clearance for this large diameter propeller without the use of a long, heavy landing gear. In addition, the landing gear required a design that would withstand not only the hard landings expected in ship-board operations, but also the stresses of "barrier crashes," when the airplane, after a slightly overshot landing, is stopped by a barrier on the flight deck. Such landings result in drag loads on the landing gear far in excess of those for which a land-type landing gear is designed. Other problems were catapult hooks, and a design that would provide for the high stresses incurred in the airplane's structure when it is catapulted. Finally, the stability and control characteristics of the airplane had to be docile and safe for carrier approaches when the airplane is flown at almost the stall condition with considerable power on.

The Gull Wing

Solution for most of the above problems centered around the inverted gull wing, which is characteristic of the Corsair. This wing combines the main advantages of the mid-wing design with those of a low wing. It permits a wing root similar to that of a mid-wing airplane in that the wing is joined normally to the surface of the fuselage, thus avoiding acute angles with their resulting interference drag, and making fillets unnecessary. At the same time, the inverted gull shape also provides a low point for the attachment of the landing gear. Thus, the landing gear can be as short and as comparatively light as that of a low-wing monoplane and can nevertheless provide sufficient ground clearance for the large propeller. Because the gear is so short, it can be retracted backward into the wing instead of having to be swung up sideways. Although there is little general objection to sideways retracting, the backward retracting gear has the advantages of permitting air intakes to be installed in the wing leading edge and eliminating the necessity for large spanwise wheel wells in the underside of the wing which might present aerodynamic problems in flight with the landing gear extended. One of the disadvantages of backward retracting landing gear is the center of gravity displacement. This, however, in the case of the Corsair is not critical.

The inverted gull shape of the wing also materially improves pilot visibility by placing the pilot's position high above that portion of the wing most likely to interfere with his view. Furthermore, it provides a low hinge line about which the wing can be folded upward; a somewhat simpler arrangement than a backward folding wing which must be rotated during the folding process.

An incidental advantage of the inverted gull wing is that it helps determine the stalling characteristics of the wing. Since the most desirable stall is one which begins near the fuselage, the gull arrangement, at high angles of attack, has the stall occur first in the trough of the gull — a location, spanwise, which is desirable from the viewpoint of control and safety in slow flight.

Another of the Corsair's most noticeable features is the location of the air intake scoops in the leading edge of the two wing roots. These scoops not only furnish engine intake air, but also intercooler cooling air, oil cooler air, air for cockpit ventilation, air for ventilating the space between the fuel tank and the fuselage skin, and air to the vacuum relief valve in the fuel tanks. Unlike most air scoop arrangements, this one does not add appreciably to the airplane's frontal area, but takes the air from a location where stagnation already exists. In addition, this location gives the air scoops the full benefit of not only the ram due to the airplane's airspeed, but also the ram due to propeller slipstream. Thus, the slipstream helps keep the intercooler and oil cooler effective in climbing flight when airspeed is slow but slipstream velocity is comparatively high.

General Layout

Except for the gull wing, the general layout of the Corsair is conventional for single engine airplanes. The entire space between the propeller and the pilot's seat is taken up by the engine with its auxiliary equipment, such as intercoolers, air ducts, oil tank, main fuel tank, hydraulic equipment, water tanks for the water injection system, and the instrument panels, rudder pedals, etc. All the airplane's radio equipment and controls, the remote indicating compass, and baggage space is located behind the pilot seat.

Tail surfaces are cantilever. Rudder and elevator are fabric-covered and incorporate overhanging balances to decrease the forces required to move the control column fore and aft, as well as balance tabs for the same purpose, and trim tabs controlled from the cockpit. Ailerons are aerodynamically balanced to decrease the forces required to move the control column from side to side and incorporate balance tabs to further decrease these forces. The left-hand aileron also incorporates a trim tab which is controlled from the cockpit and serves to compensate for the varying torque reaction effects during flight, and to compensate for the difference in weight distribution on each side of the airplane due, for instance, to the different loading combinations on the wing pylon racks.

All movable control surfaces are also dynamically balanced to prevent flutter which is a major design consideration in any high performance airplane of the Corsair's caliber. A small fixed spoiler is attached to the leading edge of the right wing midway between the wing root and the wing tip. This spoiler improves the behavior of the airplane in stalls with power on by inducing the right wing to stall immediately after the left wing, thereby helping prevent spins and eliminating any severe rolling tendencies in a stall.

Hydraulically operated slotted flaps decrease the landing speed by some 15 mph, permit steep glides, and aid in decreasing the takeoff run. A spring-loaded bypass slide valve in the hydraulic system permits the flaps to blow up to the extent required to avoid excessive air loads, allowing the use of the landing flaps as "maneuver flaps." The hydraulically operated landing gear permits the main wheels to retract rapidly and completely. The tail wheel is retracted almost fully, the drag of its protruding section being reduced by a special fairing. The arresting hook also retracts so that it is out of the slipstream.

In the extended position, the tail wheel assembly is comparatively high, so that the airplane's ground attitude is not as nose-high as that of most airplanes, although its overall ground height is greater than other single engine fighters. The original ground angle of 13½° was reduced to 11½° which resulted in greatly improved landing and ground handling characteristics.

The landing gear also serves as a dive brake, a feature that makes it possible to use the Corsair as a dive bomber. The hydraulic system exerts enough pressure to extend the gear fully at speeds up to 260 knots. A flat plate, which serves as a landing gear door and is part of the fairing when the gear is retracted, adds to the effectiveness of the gear as a dive brake by adding drag. As previously stated, the gear may be lowered if the braking effect is desired. However, some squadrons use the Corsair as a dive bomber with the gear retracted in order to take advantage of extra speed for getaway.

The Corsair has no wing tanks, although some early models were designed with them. Instead, two auxiliary droppable tanks can be carried on pylons installed underneath the wing center section, inboard of the landing gear. The Corsair's normal armament consists of six .50-cal machine guns mounted in the wings. Cannon and various types of external bomb racks and rocket launchers have been used on this airplane. Armor consists of a 3/8" plate of steel which is mounted directly behind the pilot's seat, a removable ¼" homogeneous plate on the bottom of the pilot seat, and a ½" plate in back of the pilot's head.

Structure

The Corsair's structure differs from conventional all-metal structures mainly by making use of comparatively large sheets and employing spotwelding of aluminum to an extent never before attempted in aircraft structural fabrication. The largest of these sheets forms part of the fuselage mid section and measures 48" x 102". Each of these sheets is preshaped by stretching over forms, and some of them incorporate compound curvatures. The result is a skin with remarkably few external fastening seams, and consequently low drag characteristics.

Before the sheets are assembled to form larger subassemblies, stiffening structure is affixed to the inboard side of each sheet. These stiffeners are almost exclusively spotwelded, rivets being employed only as "stop" rivets in certain critical locations. After assembly, the sheets then form the skin of the airplane, while the stiffeners join to form the transverse frames of the fuselage or similar internal members. This method of construction makes it possible to apply an unusually large proportion of the total required man hours to the airplane before the parts are assembled into shapes which would make access comparatively difficult. In many cases, hydraulic lines and controls and similar components are installed on these panels before assembly.

The airplane is subdivided into several major assemblies, each of which is replaceable.

Fuselage

Fuselage consists of three major sections, each of which is replaceable. There is a front section which houses the fuel tank and cockpit, a midsection, and a tail section which houses the tail wheel assembly and carries the tail surfaces.

These three sections are quite similar in design. In each section, four longerons, consisting of built-up I and T beams, carry the bending loads. Shear and torsional loads are carried by the skin which is up to .072" thick and is reinforced by transverse stiffening frames. In locations where the fuselage has cutouts (for example, the cutout for the cockpit or for the tail wheel doors) there are additional longitudinal stiffeners.

Longerons of each section terminate in fittings of dural forgings. In joining two fuselage sections together where lesser longitudinal members must be carried from one section to another, similar treatment is employed.

The skin of each fuselage section ends in a shear plate. Final connection of the two sections is effected by bolting and riveting the two shear plates together.

Overturn provisions are built into the bulkhead behind the pilot's seat as an integral part of the fuselage structure.

Cockpit

Controls are conventional, the stick carrying the machine gun firing button and the bomb release button. Rudder pedals carry toe-type brake pedals. Height of the seat is adjustable. In addition, the rudder pedals can be adjusted through a wide range fore and aft, and the angle of the brake pedals on the rudder pedals can be adjusted.

The main instrument board carries the usual flight and engine instruments. A sub-panel near the pilot's right knee carries a fuel gage, hydraulic pressure gage, and position indicators for oil and intercooler flaps. A sub-panel near the pilot's left knee carries a separate position indicator for each main wheel and the tail wheel. At the pilot's left, controls are arranged in the following order, rear to front: wingfold lock, wingfold control, tail wheel lock, rudder tab control combined with tab position indicator, aileron tab control combined with tab position indicator, elevator tab control, elevator tab position indicator, engine control unit, fuel selector, landing gear control, and flap control.

On the pilot's right there is a shelf which carries electrical switches, including the starter switch, the primer, and emergency electrical fuel pump. Forward of these are the controls for the cowl flaps, oil cooler flap, and intercooler flap. The arresting hook control is located outboard of the switch box. Radio control units are on the right wall of the cockpit. The airplane's battery is under the pilot's distribution box. All radio equipment is located on a shelf installed just aft of Station 186.

Wing Center Section

Wing center section is the most intricate structure of the entire airplane. It incorporates not only the inverted gull curvature but also provides a housing for the landing gear in its retracted position. Structure consists of a leading edge torque box which is formed by a series of chordwise leading edge ribs and spanwise stringers and is completed by the main beam which can be considered the backbone of the airplane. An interbeam torque box is formed by the main beam and the rear beam interconnected by skin of .091" thickness plus chordwise formers and spanwise stringers.

Extensive loads are introduced in the leading edge torque box chiefly through its support of the wing center panel and the landing gear. These loads could not be carried entirely through the leading edge to the fuselage and were transferred to the interbeam torque box. Adequate structure could not be provided economically in the inboard area of leading edge due to air intake ducts.

Considering that the main beam is a part of both the leading edge and interbeam torque boxes, and further considering its complicated shape, it can be seen that an involved design problem was encountered. The upper and lower flanges of this beam could not be formed from an ordinary extrusion. Instead, the flanges had to be built up from a series of flat strips and smaller extrusions formed to the gull contour and bolted together. Heavy sheet webs reinforced by vertical stiffeners complete the major construction of the main beam. The outer panel main hinge fittings, catapult hooks for airplane launching, landing gear drag link attachment fittings, and pylon mounting fittings for drop tanks and bombs, all are mounted directly to the main beam.

The completed wing center section contributes greatly to the distinctive appearance of the Corsair. More important, it provides supports for the outer panel flap, landing gear, and landing gear retracting mechanism. It is designed for catapult launching, is stressed for barrier crash loads, and houses the oil coolers and intercoolers.

Wing Outer Panels

While the wing center section is of two-beam design, outer panels are designed with a single beam. This main beam, located at 30% of the chord, together with the leading edge structure, forms a D beam which carries all torsional, drag, and lift loads. Leading edge structure consists of chordwise ribs, spanwise stringers, and metal skin covering. All structure aft of the beam is cantilevered from the beam and consists chiefly of chordwise ribs, fabric covered except for an area inboard under the gun bay, which is metal covered.

Provision for three .50-cal machine guns is built into the inboard end of the panel with blast tubes through the leading edge. Ammunition boxes, carrying 375 rounds for each of the two outboard guns and 400 rounds for each of the four inboard guns, are easily removed through the upper surface of the trailing edge. The guns are serviced through an access door in the upper surface. Various sizes of rockets can be attached to the under surface of the outer panel.

The wing tips are fabricated from plastic materials and can be manufactured quickly and cheaply, providing an excellent expendable unit. The wing tips are interchangeable and are easily removed. Both the British and Navy versions of the wing tip are removable, and the structure inboard of the tips is the same for both versions.

Wingfold

The wingfold is hydraulically operated and is controlled from the cockpit. In the extended position, wing outer panel is connected to the center section by three steel fittings. Torsional and side loads are taken by a fitting just aft of the leading edge. Bending loads are taken by a fitting at the top of the main spar, and another fitting at the bottom of the main spar. Fittings at the leading edge and at the top of the spar are designed as hinges about which the wing can be swung upward. With the airplane in a three-point position, the wing folds approximately straight up. If wing folding motion was described with reference to the airplane's longitudinal axis, the wings could be said to fold slightly forward.

The third fitting, located at the bottom of the main spar, is designed as a simple lock. The wing is held in place by a large sliding hinge pin. After manually releasing the mechanical lock, the pilot moves the wingfold control to the fold position and hydraulic fluid is admitted to the hinge pin-pulling strut. This causes the hinge pin to be pulled out of the lock. As the hinge pin retracts, it releases a spring-loaded mechanism which causes a small "flag" door on the top of the wing surface to spring open. This door clears a space just above the main spar hinge where wing folding would otherwise crush the skin. At the same time, the door serves as a warning signal to the pilot that the bolt no longer is in place.

As retraction of the hinge pin is completed, a sequence valve, built into the pin-pulling strut, diverts hydraulic fluid to the wing folding strut which is located in the outer panel. The outer panel then folds upward.

When the pilot moves the wingfold control to the spread position, hydraulic fluid is directed to the wingfold strut located in the outer panel and the panel lowers into place. As the outer panel falls into place, a load and fire valve diverts hydraulic fluid from the wing folding strut to the hinge pin-pulling strut causing the hinge pin to slide into place, thus locking the wing. As the hinge pin completes the last of its travel, it contacts an linkage which pulls the flag door closed, thus signaling to the pilot that the hinge pin is in place. The pilot then locks the hinge pin from a separate cable-actuated locking control in the cockpit. After locking the control, the wing cannot be folded again until the pilot has released the locking pin.

An interesting problem was presented by the aileron and flap controls and by the hydraulic lines to the machine guns and the wing folding strut. All these components must be carried through the wing fold. The problem was solved by carrying most of the controls and lines through the exact wingfolding hinge line. In the case of the aileron, this arrangement resulted in the additional advantage that with the wings folded the aileron linkage becomes almost inoperative and the ailerons are practically locked so that they cannot be moved by the wind. In the case of hydraulic lines, the problem was solved by the use of swiveling joints mounted on the exact wing-folding hinge line.

Ailerons

Ailerons are constructed entirely of wood, since it was found that plywood skin provides a stiff and smooth surface which improved considerably many of the undesirable aerodynamic characteristics of the rib and fabric type ailerons. Wood construction also was chosen in preference to metal because of weight saving possibilities and because gun fire tests on both wood and metal types showed that although wood splintered, it left no undesirable protuberances as did sheet metal skin on the all-metal aileron. The plywood ailerons are covered with fabric for weatherproofing. The Corsair is noted for having exceptionally high rate of roll combined with light stick loads, even at high speeds.

Flaps

Flaps on each side of the airplane are subdivided into three separate sections, One of the sections is carried by the outer wing panel and is separated from the other sections by the wingfold. The other two flap sections are carried by the wing center section, one on the down-sloping portion, and one on the up-sloping portion. Because of the gull shape, these two flap sections diverge from each other as they are deflected, thus opening a gap at the trough of the gull shape. This gap is closed by a "gap-closing" door which is a sliding panel hinged to the inner flap section and sliding telescopically within the center flap section.

The flaps are actuated by a hydraulic strut located in the wing center section. To carry the flap actuating mechanism across the wingfold, the hydraulic strut is at the wingfold line and the outer flap section connected with it by a rod which incorporates a swiveling universal joint.

Tail Surfaces

Stabilizers are of full cantilever, all-metal construction. Structure consists of a single spar which is located at the trailing edge of the stabilizer, to which bulkheads, the main attachment fittings and the elevator hinge fittings are attached. Hat-shaped stringers, parallel to the spar are spotwelded to the skin which is riveted to the bulkheads and the spar. Left and right stabilizers are identical and may be interchanged. They are connected to the fuselage by three main attachment points (two at the spar and one at the leading edge) which take bending loads, while torsional loads are taken through a structural fairing attached to the skin by screws and anchor nuts.

Elevators are of fabric covered aluminum alloy construction. They are attached to the stabilizer at three hinge points and are connected by a torque tube. The tip of each elevator projects 11" forward of the hinge line to provide aerodynamic balancing for reduction of control stick forces. The left and right elevators are identical and may be interchanged.

The fin is of full cantilever, stressed skin construction. It contains a single spar and is attached to the fuselage by two main fittings at the spar and a structural fairing around the bottom contour. The leading edge is offset 2° to the left to counteract the effect of propeller slipstream.

The rudder is similar in construction to the elevators and incorporates a short mast on the hinge line for supporting one end of the radio antennas.

Alighting Gear

Alighting gear of the Corsair includes the two main landing wheels and mechanisms, the tail wheel and arresting hook and their mechanisms. The main landing gear is supported from the wing center section and retracts aft into the wing, being completely enclosed by doors when retracted. The tail wheel and arresting gear are integrated mechanically and structurally; they are supported from the after section of the fuselage, and retract upward into the fuselage, being almost entirely enclosed by doors when retracted. Power for retraction and extension of the alighting gear is furnished from the main hydraulic system. Main landing gear wheel brakes are powered by an independent hydraulic system. The tail wheel is self-centering and may be locked in the trailing fore and aft position. The main landing gear consists of 32 x 8 wheel with multiple disc brakes, oleo strut, lifting device, linkage, retracting cylinder, and dive brake fairing.

Retraction is hydraulic and operates through a linkage which is self-locking in both extended and retracted positions. In retracting, the hydraulic retracting cylinder shortens, pulling the cylinder links (pivoted on the oleo strut) aft and pushing the lock links up. This action causes the lock links to break upward at their toggle joints, and in turn, break the drag links upward at their points. As the retracting cylinder continues to shorten, it pulls the collar of the oleo strut aft and upward, pulling the oleo strut aft. The pivot fitting of the oleo strut, which is set at an angle to the plane of rotation of the strut rotates as the strut is pulled aft, rotating the strut within the collar. It is this action which permits the retracted wheel to lie within the wing.

Oleo struts of both the main wheels and tail wheels are of the compound oleo-pneumatic type. These units were especially designed by Chance Vought to provide the necessary shock absorption to give the Corsair its exceptional carrier landing qualities.

The tail wheel linkage carries the arresting hook. The hook is raised and lowered by a separate hydraulic strut actuated from a control in the cockpit. A dashpot serves to prevent the arresting hook from bouncing, upon contact with the flight deck, in order to minimize the probability of the hook missing the arresting cables on the deck.

Power Plant

The engine is a Pratt & Whitney R-2800 radial, aircooled, engine equipped with two speed, two stage superchargers, and delivers 2000 hp for takeoff. It is equipped with a Bendix injection carburetor and with a water injection system. The auxiliary blower can be operated in neutral, or at a low gear ratio of 6.46:1, or at a high gear ratio of 7.93:1.

The exhaust system is designed to utilize the energy of the exhaust gases for propulsion. That is, the design is arranged so that the jet effect of the exhaust gases can be applied advantageously. Six separate exhaust manifolds, each serving three cylinders, discharge the exhaust backwards under the fuselage and create at full throttle a reactive force of 190 lb. At high speed, this amounts to approximately 210 hp, and the arrangement adds about 20 mph to the airplane's top speed. As compared with the utilization of the exhaust energy in a turbosupercharger, this arrangement has the advantage that the power thus made available need not be absorbed by the propeller. The Corsair shows the first application of jet thrust principles in radial, aircooled powered high performance airplanes.

Engine cowl is equipped with adjustable exit flaps. Because the absence of an intake air scoop makes the cross section of the cowl almost round, an exceptionally simple system of cowl flap control could be employed. The flaps are opened by spring action. They are closed by a cable draw-string which runs all the way around the entire flap system and is pulled in or let out by a hydraulic strut. An overload relief valve in the hydraulic system protects the flaps by allowing them to blow open under excessive internal air loads, and the mechanism is so designed that the flaps will blow closed under excessive external air loads.

The main fuel tank is located in the fuselage between the cockpit and the engine. It is of self-sealing construction and is protected in front by the engine and in back by the cockpit armor. Some additional protection against glancing shots is afforded by the skin, which at this section of the fuselage is .102" in thickness.

The fuel tank is vented to a point below the center section. A valve automatically closes the vent at altitudes above 12,000 ft and admits manifold pressure to the tank, maintaining tank pressure at approximately 3½ psi above surrounding atmospheric pressure. This prevents loss of fuel through boiling, which otherwise might seriously interfere with the airplane's range at high altitudes. The tank is pressurized also to insure positive fuel feed by eliminating the possibilities of vapor lock.

The tank is equipped with a vacuum relief valve which automatically admits outside air during a rapid descent when the capacity of the tank vent would not be sufficient to compensate for the rapid increase in outside atmospheric pressure.

In addition to the engine-driven main fuel pump, an electrically driven fuel pump is provided as an emergency auxiliary.

Injection of the coolant is accomplished automatically when the throttle is pushed forward far enough. In order to fit the desired tank capacity into the restricted area of the accessory compartment (on an installation already designed) three separate, comparatively small tanks are provided.

The cockpit is ventilated by air taken from the left hand air scoop. The air inlet is between the rudder pedals, and flow can be adjusted by the pilot's foot. The cockpit canopy can be locked in several slightly open positions in addition to the fully closed and fully opened positions.

A cockpit heater has proved unnecessary in this airplane since hot engine-cooling air flows along the fuselage and furnishes sufficient warmth. There is, however, a windshield defroster, heat for which is furnished by a Stewart-Warner heater. Mixture taken from the outlet side of the main stage blower is burned in a combustion chamber located in the cockpit, and the exhaust is piped to the inlet side of the main stage blower. This hook-up insures a sufficient pressure differential to operate the unit properly at all times, regardless of the absolute manifold pressure at which the engine is operating. An electrically-driven fan takes cockpit air past this unit from whence it is piped into the space between the windshield and armor glass reflector plate.

Primary control surfaces consist of the ailerons, elevators, and rudder. The manual flight controls for these surfaces consist of mechanisms used to actuate these units and their controllable trim tabs.

Aileron and elevator control systems are of the push rod type and motions are transmitted from the control stick to the surfaces through an arrangement of rods, levers, bellcranks, and idlers.

Rudder control mechanism consists of a continuous cable system from the rudder pedals to the rudder horn.

Tab controls for all primary surfaces consist of cable and chain assemblies routed from sprockets on the bottom of a cockpit control wheel to a sprocket in the control surface. This sprocket turns a screw jack which moves a rod assembly. Motion is transmitted to the trim tabs by a rod and bellcrank. The Corsair's hydraulic system is a medium pressure, closed-center system operating between the pressure limits of 925 and 1150 lb. Hydraulically actuated units are: main landing gear and doors, tail wheel, arresting hook, wing folding and wing hinge pin pulling mechanism, landing flaps, cooling flaps, and gun chargers.

The system is energized by an engine-driven, fixed-displacement pump. Oil is supplied to the pump from a reservoir. From the pump, the fluid is passed through a fine filter to a pressure regulator which, in conjunction with an accumulator, maintains system pressure between the prescribed limits. From the pressure regulator, the main pressure line enters a manifold. The manifold acts as a distribution center from which pressure valves branch to the selector valves which control the hydraulically actuated units.

A main relief valve is provided to keep the pressure at a safe maximum in the event of regulator failure. A hand pump in the cockpit allows the pilot to actuate a unit in the event of any pump difficulties and also serves as an aid in maintenance, allowing the ground crew to actuate hydraulic mechanisms without running the engine.

In the event of hydraulic system failure, extension of the landing gear is effected by a carbon dioxide system which, when actuated, automatically by-passes and shuts off the hydraulic system and allows CO2 under pressure to enter the actuating cylinders to extend the gear.

The electrical power for the Corsair is supplied by a DC-type installation operating on a nominal potential of 24 V. It is a one-wire system with copper wiring on the positive side of all circuits and the negative side of the circuits carried through the airplane structure, all parts of which are electrically bonded.

The greater portion of the electrical system is controlled from the pilot's distribution box located on the right hand shelf of the cockpit. From there, such operations as starting, priming, and operation of the electric fuel pump are controlled. There are also the battery, pitot heater, recognition lights, emergency generator, master radio, and exterior lights switches and the interior light starter rheostats. Other control switches will be found on the gun switch box and rocket and bomb switch box which are located on the left and right side of the cowl deck, respectively.

Almost all of the electrical circuits of the airplane are protected by circuit breakers most of which are located on the armament switch panel on the left side of the cockpit; the rest, of which there are six, are located on the distribution box. These are the instrument, recognition lights, inertia switch, IFF radio, exterior lights, and starter circuit breakers.

The batteries used are 24-V, 17 amp-hr type and the generator is of the engine-driven aircooled type with a rated output of 75 amp at 30 V. A voltage regulator automatically maintains the voltage in the system at a constant value.

Armament

Armament installation comprises six .50-cal Browning non-synchronized, fixed aircraft machine guns in the outer panels. Provisions are made for carrying eight aircraft rocket projectiles, and when the airplane is used as a dive-bomber, two 1000-lb bombs.

Armament installations are so arranged that guns may be fired in pairs, by four, or in salvo. Rockets can be launched in pairs, or in salvo at a 1/10 second interval. Bombs are released in pairs or singly. All firing controls are mounted on the pilot's control stick.

Guns are located in the inboard end of the outer panel with the barrels projecting into blast tubes, the muzzles of which are flush with the wing leading edge. Guns are mounted on adjustable trunnion posts which permit a wide range of adjustment for the different boresighting patterns used in the variety of tactical missions for which the Corsair is so well suited. Ejected cases and links fall directly into the airstream through chutes attached to and below the guns. For each gun the link and case chutes meet in a common opening to the airstream. Ammunition is fed from the boxes, over phenolic rollers and through feed chutes into the gun breech.

Accessible Gun Installation

One of the outstanding features of the Corsair gun installation is its accessibility. Access to the guns for servicing is provided by large gun bay doors in the upper surface of the outer panel. Latches on the doors are of the quick opening type. Ammunition boxes are easily and quickly replaceable.

Ease of servicing provided by the installation accounts for the low time allowance necessary for rearming the Corsair on a carrier flight deck.

This Design Analysis article was originally published in the August, 1945, issue of Industrial Aviation magazine, vol 3, no 2, pp 7-8, 10, 12-14, 16, 18-23, 96-97.
The original article includes 5 photos, three-view and 9 detail drawings, plus a ledger-sized foldout with a color phantom rendering and a major assemblies diagram.
Photos are not credited.