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Inside the Me 262 turbojet fighter


Written by Sakhal

The Messerschmitt 262 was the first turbojet fighter to have operative use in war. It entered service, as an experimental unit, in the beginning of the summer 1944. Due to the insistence from Hitler to turn it into a "Blitz-bomber", it was initially employed as such in the Western Front, from August 1944; however, soon after it was allowed - additionally - its normal development as a fighter, equipping several units during the last months of the war, including an elite unit, composed by veteran pilots. It was used as well by some Staffeln specialized in short-range reconnaissance and even as night fighter in the defense of Berlin. The program started to convert four KG (bomber wings) in fighter units equipped with the Me 262A, was interrupted by the end of the conflict, happening the same to the development of the version Me 262C Heimatschutzer (Protector of the Homeland), which used an additional engine. After the war, this aircraft was produced in small scale by Avia in Czechoslovakia, in versions single-seat and two-seat (S-92 and CS-92 respectively), remaining in service until the mid 1950s.

Inside the Me 262 turbojet fighter


Inside the Me 262 turbojet fighter


Features of the Messerschmitt Me 262

Fore fuselage

The tip of the nose has a hole cut in front for a gun camera mounted inside, which can be reached by a small access plate placed in the larboard side. This film recording camera is activated when the guns are fired, being the recordings used later to study their performance. The next section of the fuselage contains the pivot point of the nose wheel and the four MK 108 30 millimeters cannons grouped high in the nose section. Since the length of these guns is just about 106.5 centimeters, a very compact installation has been achieved with no external projections. A large spherical support around the barrel near the aft end facilitates adjustments during sighting in operations. The guns are usually set to converge at 450 meters. The MK-108 cannon has a rate of fire of 575-600 rounds per minute and a muzzle velocity of 480-540 meters/second, with a weight of 60 kilograms. Compressed air for charging is carried in eight bottles placed next to the ammunition magazines. The upper guns carry 100 rounds each while the lower ones carry 80, being all fired simultaneously by a switch on the control stick. The shell sheats are expulsed through apertures in the lower part of the fuselage. Four 30-millimeter cannons is an unusually strong armament for a fighter, and very few of the fighters ever built had installed such a firepower. However the Me 262 suffered from low ammunition reserves; it was actually intended for destroying bombers more than for fighting against another fighters, for ammunition shortages would be a problem. The section of the fuselage where the guns are installed is covered by 2-millimeter thick steel plates. The guns are accessible through two access doors, piano hinged on the top centerline, which can be quickly opened, exposing the gun mechanisms and ammunition magazines.

The nose section could be detached from and attached to the aircraft with relative easiness, to allow installation of a new nose in short time, perhaps equipped with different armament or reconnaissance equipment. This whole nose section attaches to the central fuselage in a simple but effective manner. At each lower corner there is a high-tension steel bolt fastening it to the solid web bulkhead of the mid section, while at the top there are two steel tubes, also bolted to forged fittings on the mid-section bulkhead and extending forward to the fore bulkhead. Both tubes are built as turnbuckles so that alignment adjustments can be easily made. At the end of the nose section, the cross section of the fuselage resembles a slightly rounded out equilateral triangle. The first bulkhead in the mid fuselage section is made of solid web aluminum alloy with six vertical and two horizontal hat-shaped stiffeners. At a point 42.5 centimeters after there is a channel- shaped former, flush riveted to the cover, and 40.6 centimeters further aft there is another solid web bulkhead with vertical and horizontal hat-shaped stiffeners. In this section practically all the space is taken by the fore fuel tank. The bottom panel of this section, 88.2 centimeters long and 139.7 centimeters wide, is attached to the fuselage by flush screws and captured nuts.

Cockpit

After this section, the cockpit is contained in a cylindrical compartment; albeit this section was designed for pressurization, the crude sealing points that this feature was never used in operations by the Germans. The cockpit canopy consists of two rounded plastic glass sections mounted in a frame with flat fore-and-aft pieces and tubular base. The canopy is of the swing-open type and the armored windshield is 90-millimeter thick bulletproof glass. A 15-millimeter thick head and shoulder silhouette armor section, which extends up and over the back of the pilot's head, is bolted to the canopy frame just ahead of the turtleback section. There is no protection provided for sides and bottom on the cockpit. The rudder pedals are quite close to the seat and there is no fore-and-aft adjustment either on the pedals or the seat; for this reason pilots should be smaller than average. The pilot's seat is adjustable only up and down on a parallelogram frame, and it is locked in position by a lever under the front of the seat which engages a pin in ratchet teeth. Unlike earlier German aircraft, the Me 262 has no bungee cord to facilitate moving the seat. The upholstered back of the seat is held in place by two clip springs to facilitate removal for access to the battery, which sits just behind the seat frame. The seat itself does not incorporate armor plating; it is instead attached to channel-shaped vertical and horizontal stiffeners riveted to the solid aluminum alloy bulkhead which begins the aft fuselage section and forms the front panel of the rear fuel cell. The bottom panel for this section measures 90 x 152 centimeters and is similar in construction to that under the front fuel cell.

The main instrument panel is divided in two sections, with flight instruments on the left and engine instruments on the right; bomb switches are on a panel in the lower center. At the top, the reflector gunsight Revi 16B is displaced to the right to improve frontal visibility. Flight instruments include artificial horizon combined with bank and turn indicator, airspeed indicator, altimeter, rate of climb indicator, repeater compass and blind approach indicator. Engine instruments include tachometers of two-speed variety to give readings from 0 to 3000 revolutions per minute and from 2000 to 15000 revolutions per minute, gas pressure gauges indicating up to 1 kilogram/square centimeter, gas temperature gauges indicating up to 1000 degrees and oil pressure gauges and fuel gauges for fore and rear tanks. Included in design plans, but not installed in studied aircraft, there were two fuel injection pump pressure gauges marked at 65 kilograms/square centimeter. At the left of the cockpit, the diagonal panel includes oxygen valve and flow indicator, emergency landing gear and flap operating switches, while the horizontal panel includes landing gear and flap position indicators, landing gear and flap operating buttons, stabilizer pitch indicator and operating switch, throttle quadrant, fuel selector valves, rudder trim tab cranks, and jet-assisted takeoff unit jettison release. At the base of the front panel there is a pull handle for the nose wheel brake, and to the right, beneath the left windshield panel, there is a lever to open and close the cockpit's ventilating scoop. At the right side of the cockpit there are canopy jettison lever, pilot heater, very signal, radio frequency selector and on/off switches, and tachometer low-speed selector switches. A curved handle is for bomb release; pulling it clear back beyond bomb release stop jettisons bomb racks. The electric junction box is installed below these panels outside the fuselage cockpit liner, being easily accessible from the ground because it is located just above the wheel well.

Rear fuselage

The bulkhead forming the aft end of the rear fuel cell is a solid web in sheet steel of approximately 2 millimeters in thickness. An unusual construction feature is found throughout much of the aft fuselage section, where the formers are made of the aluminum skin sheets themselves. In fabrication, the skin sheets are formed to the fuselage contour, then the aft 12 millimeters are joggled to the thickness of the metal itself - about 1.27 millimeters -, then bent inward to form a channel or J-section. The next skin is lap jointed and flush riveted in place. After the rear fuel tank there is the electronic equipment and further aft the master compass and oxygen bottle. Access to these elements is via a 44.5 x 38.7 centimeters door held in place by four quick fasteners. Immediately after the cockpit the fuselage shape starts changing to a very narrow elliptical section of only 60 centimeters in width at a point just ahead of the stabilizer. There a single-piece drawn aluminum fairing, held by 41 screws, encloses the adjusting electric motor and screw jack for the all-metal stabilizers.

Electronics

A metallic box contains the radio transmitter/receiver and occasionally an IFF system. Radio installation consists of the FuG 16Z or FuG 16ZY VHF transceivers, operating in frequency ranges from 38.5 to 42.3 MHz, fitted with retransmission facilities for ground control stations. The FuG 25a was an identification transponder, intended as an early attempt of an IFF (Identification Friend or Foe) system. This allowed the aircraft to identificate itself to the Freya, Wurzburg and Gemse ground radars. Its reception frequency range was 125 + or - 1.8 MHz and its transmission frequency was 160 MHz with a range of up to 100 kilometers. Small aluminum strips which frequently carried explosive charges were fitted onto the outside of the electronic equipment aluminium housings. These explosives, fitted with a slow match cord fuse that allowed for the evacuation of the crew, destroyed the equipment rather than allowing it being captured by the Allies.

Fuel tanks

The two main fuel tanks, self-sealing, had a capacity of 920 liters, each of them fitted with two booster pumps and selector valves allowing pumping from either tank to either engine, or from aft to fore tank. A 200 liters reserve tank could be installed below the cockpit, and there were plans for a 630 liters auxiliary tank installed after the aft tank. The pilot would be in fact surrounded by fuel tanks.

Gear landing

In operation the main wheels swing up and into the bottom of the fuselage, with the right strut operating an actuating valve at the end of its arc. This valve in turn closes fairing doors which are hinged at the fuselage centerline and which serve as the landing gear up lock. The nose wheel retracts aft and up into a well below the armament compartment; the wheel, near the end of the retracting arc, strikes a transverse tube which pulls the double skin fairing door closed. Spring loaded pins moving into the piston serve as up and down locks. Pilot's error in forgetting to lower the landing gear is avoided through the system being so arranged that the flaps cannot be extended until the landing gear has been put down. The nose gear retracts and extends after the main wheels have been locked either up or down. Both the landing gear and flap operating systems have connections with a compressed air bottle which can be cut in for emergency operation of the two systems.

Engines

The Junkers Jumo 004 axial flow gas turbine jet power plant is 386 centimeters long from the intake to the tip of the exhaust; 76.2 centimeters in diameter at the skin around the six combustion chambers, with a maximum diameter of the cowling reaching 86.3 centimeters; diameter at the intake end is 50.8 centimeters, the outer skin increasing to 80 centimeters and the inner to 54.5 centimeters. Inside the nose cowling there is an annular gasoline tank divided into two sections, the upper one being of 2.8 liters capacity, feeding fuel to the starting engine, and the lower one of 12.3 liters capacity, feeding starting fuel to the combustion chambers. The nose cowling is attached by eight screws in captured nuts to the annular-shaped compound oil tank and cooler. Having 11.3 liters capacity, this tank has a baffle close to the inner surface so that as warm oil is fed in from the top it is cooled as it flows around to the bottom of the annulus and the tank proper. The oil tank, in turn, is attached by 23 bolts on a flange to the aluminum alloy intake casting. Inside the nose cowling there is a fairing which looks like a propeller spinner, increasing in size to 30.5 centimeters at the intake casting. This fairing houses the starting engine, a two-cylinder two-cycle horizontally opposed gasoline engine which develops 10 horsepower at 6000 revolutions per minute. This starting engine has its own electric starting motor; and, for emergency, extending out to the front of the fairing there is a cable starter similar to those found on outboard boat engines. The engine is 31.7 centimeters long, 25.4 centimeters wide, 21 centimeters high, and weighs 16.3 kilograms.

Next in the fore-to-aft sequence is the aluminum alloy stator casting, which is built in top and bottom halves held together longitudinally by eleven bolts through flanges on each side, with attachment to the intake casting by 24 bolts through a heavy flange. Running the entire length of the bottom half of the casting are three passages of 17.8 millimeters in diameter, one serving as part of the oil line leading to the rear compressor and turbine bearings, one connecting oil sumps - which are located in both intake and main castings -, and one serving as part of the oil return line from a scavenge pump set in the rear turbine bearing housing. Stator blades are made of either stamped aluminum or enameled mild steel; in the last row of blades temperatures reach 380 degrees, thus burning off the enamel. Except for the inlet guide vanes and the last row of stator blades, which act as straighteners, stator blades are arranged to simply serve as guides to direct the airflow into the rotor blades. The compressor rotor is made up of eight aluminum disks held together by twelve bolts each through shoulders approximately at mid-diameter, with the entire unit being pulled together by a 98.4 centimeters long and tie rod of 17.9 millimeters in diameter. The diameters of the disks increase from the low to high pressure ends as follows: stage 1, 35.2 centimeters; stage 2, 37.3 centimeters; stage 3, 39.6 centimeters; stage 4, 41.7 centimeters; stage 5, 43.6 centimeters; stage 6, 45.3 centimeters; stage 7, 46.3 centimeters; and stage 8, 46.6 centimeters. Compressor rotor blades, of which there are 27 in the first two stages and 38 in the rest, are all stamped aluminum with machined roots fitting into pyramid-shaped slots in the rotor disk.

The backbone of the Jumo 004 engine is a complex aluminum casting which, in addition to providing the three engine attaching points, supports the compressor casing - through 25 bolts -, the entire combustion chamber assembly, the turbine nozzle, the aft compressor bearing, the two turbine bearings and, through the combustion chamber casing, the entire exhaust system. Combustion chambers are surrounded by a mild steel double-skinned casing; holes in the front ring carry cooling air into ducts between the two skins. Cooling system takes well over 7 percent ot total air intake. 61-blade hardened chrome steel turbines are used, taking stresses of about 15 tons at maximum revolutions per minute. Originally both blades and disks were solid, later hollow blades and lighter disks were introduced, saving approximately 18.2 kilograms. The aluminized mild steel exhaust cone houses a rack gear which moves a "bullet" extending from its aft end. Actuating this bullet over its maximum travel of approximately 18 centimeters varies the exit area between 20 and 25 percent. It is set in retracted position for starting to give greater area and help prevent over-heating, then moved aft to decrease the area and give greater velocity for takeoff and flying, being the movement accomplished by a gear-type servo motor. Originally the unit was supposed to operate automatically over small ranges at extremely high speed and altitudes to give maximum efficiency, but on some engines examined the necessary lines had been blanked off. The two-position operation is obtained through a mechanical linkage with the throttle so that the bullet moves aft at between 7000 and 7500 revolutions per minute.



Article updated: 2015-07-09

Categories: Aircraft - World War Two - 20th Century - [General] - [General]

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Website: Military History

Article submitted: 2014-04-05


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