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Albatros "Kobold" (L 79),
The aircraft type Albatros "Kobold" (L 79) was developed as a single-seater experimental aircraft for research into the behavior of symmetrical wing profiles at the suggestion of the D V L. In addition to all normal ones, the tests should also include the conditions in reverse flight attitude (inverted flight). The aircraft had to be appropriately trained in accordance with this plan.
The entire airframe is dimensioned according to the requirements of the highest group of load assumptions. In the case of inverted flight, the strengths are also increased by 50%.
The supporting structure consists of upper and lower wings of the same span without staggering and without V-position. One N-stem each, streamlined wire outcrossing in the front spar plane. Upper wing on the tensioning tower, lower wing hinged to fuselage lower edge Same wing cut, symmetrical profile over the entire span with rounded ends. Box spars in usual design, wing nose and top planked with plywood. Double ailerons made of light alloy
The fuselage is a welded tubular steel framework. The rear fields are crossed out with wire. Side doors and removable fuselage back. Use of seat cushions, Irwing and Heinecke parachute provided. Behind the driver's seat, 550X350X150 light alloy carry-on.
Along the fuselage, the masses were pushed together as much as possible, so that the guide moved close to the center of gravity. As a result, the aircraft does not assume high rotational speeds in spinning, and the operator works with low centrifugal accelerations. The fuel tank is almost in the center of gravity, so that the aircraft's center of gravity hardly shifts when the payloads change.
The tails consist of tubular steel skeletons covered with fabric. The elevator fin is adjustable at the bottom. The rudders are balanced.
The control unit consists of bumpers, levers and cables. The elevator ropes are double. Foot lever adjustable.
The chassis has a raised axle and pressure rubber struts. The spur also has pressure rubber suspension.
Engine: Sh 12 with "Sum U 36" injection carburettor. The decisive factor for the design of the engine system was the required unrestricted inverted flight capability. The previous explanations could not serve as models, since they used either pressure vessels, which are prohibited, or drop containers, which were out of the question because of the increase in air resistance, and moreover their losses of lubricant were too great, as their entire lubrication system was inadequate. Despite the fact that the fuel pump's flow rate was many times larger under the existing conditions and varied with the speed, it could be brought into line with the very pressure-sensitive injection carburettor, and the lubrication system could also be designed to be operationally reliable despite the engine's gear pumps, which were unusable for the inverted flight and the oil sealing of the fuel pump. The fuel pumping from the aerobatic tank is carried out by the Junkers Deka fuel pump, which is completely insensitive to position, the flow rate of which is perfectly automatically regulated by a throttle and overflow line according to the respective consumption of the engine despite the sensitivity of the carburetor to pressure.
The lubricant flows to the engine in a normal flight position through a natural gradient and under the suction effect of the engine's fresh oil gear pump. After its circulation in the engine, it is returned to the reservoir by the engine's return gear pump. Two additional gear pumps are installed for the lubrication conveyance in inverted flight and for the oil sealing of the fuel pump, one of which is connected to the fuel pump with about 1 atm via a reduction and check valve. pulls the trigger. The oil flowing out of the reducer valve is returned to the lubrication tank by an automatic diverter valve in the normal flight position, while in the supine position it is pushed into the fresh oil line, from where it flows to the engine's fresh oil pump. The second additional oil pump takes over the suction of the lubricant in the supine position and transports the hot oil back into the container. These lubrication systems have completely avoided lubricant losses and ensure perfect lubrication of the engine in every flight attitude. Furthermore, for safety reasons, the fresh oil tap is coupled with a safety ignition switch, so that the engine cannot be started before the tap is opened.
The fuel tanks are made of light metal and are housed inside the fuselage. The capacity of the drop tank is 34.5 l, that of the aerobatic tank, which is specially shaped for figure flights, 47.5 1 and that of the oil tank 5 1. At normal speed, the amount of fuel is sufficient for a flight duration of 2.5 hours.
If the unlimited inverted flight capability is dispensed with, the engine system can be simplified accordingly. The engine receives the normal sum carburettors again, and the fuel supply from the aerobatic tank is taken over by an A.-M. pump, which pushes the fuel into the float carburettors via an air chamber. The lubricant system is given the usual design of Siemens motors by eliminating the additional gear oil pumps and valves.
Wingspan 8.8 m, height 2.24 m, length 6.27 m, wing area 16.60 m2, engine power 108/125 hp, set-up weight: cruising 465 kg, bracketed aerobatics (465 kg), payload 175 kg (120 kg), flight weight 640 kg (585 kg), wing loading 33.5 kg/m2 (35.2 kg/m2), power load 5.92/5.12 kg/hp (5.42/4.68 kg/hp), maximum speed 165 km/h (165 km), landing speed 76 km/h (73 km/h), Flight duration 2.5 h (1.25 h), climb time to 1000 m (DNA) 4.5 min (4 min), climb speed (at 8 = 1.1 kg/m3) 3.2 m/sec (3.75 m/sec).
The above services are guaranteed with a 4% discount on the maximum speed, a 10% surcharge on the climb time and, depending on the aerodrome conditions, up to 10% surcharge on the landing speed