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Focke-Wulf GL 18c training and commercial aircraft.A
few days ago, a new twin-engine aircraft type GL 18c from Focke-Wulf Flugzeugbau AG., Bremen, was accepted at the Deutsche Versuchsanstalt für Luftfahrt e.V., Adlershof. (GL 18) and, in order to achieve even higher performance, was equipped with two 108/125 hp Siemens engines installed in the wing on both sides of the fuselage. These engines, with which more than one million air kilometers were covered in Germany alone in 1926, are known to be characterized by particularly high economy and reliability in operation.
The fuselage of the aircraft is significantly wider than the GL 18, so that the cockpit could be equipped with a comfortable 2nd driver's seat and double controls. The elevator and ailerons are operated in the familiar way by means of a split handwheel, while the rudder is moved by pedal. Since the machine is also intended as a training aircraft in addition to commercial flights, the most important control, the elevator, was set up in such a way that it can be separated from the student's control by the 1st leader with one handle in the event of any incorrect steering movements of the student. All other parts of the aircraft show the design characteristic of Focke-Wulf. The machine is comingespecially for young commercial pilots to familiarize themselves with the operation of multi-engine aircraft.
The installation of the two Siemens motors and the resulting adaptation to the streamlined motor nacelles is interesting, which is made possible by the short design of the motor with the star-shaped cylinders located in one plane. The installation consists of a tubular steel frame with an advanced motor frame made of sheet steel. The tubular steel framework with its root points is anchored directly to the box spar of the wing with continuous long steel bolts. Steel pipes and removal rods are bolted together by means of conical bolts, welding has not been done. the whole structure of the engine mount is such that there is
an extraordinarily convenient accessibility to the parts mentioned for the inspection and for the possible overhaul of magnets and carburettors. When the lower body shell is removed in a few simple steps, the fitter can work standing on the ground, with the carburettor and magnet sitting in front of him at eye level. The engine compartment is separated from any wing construction at the top and rear by a fire bulkhead made of sheet steel; above each carburetor ends a fire extinguishing line of the manual fire extinguisher, which is permanently installed in the driver's seat and can be handled easily and quickly. The engine mount is so far forward that in the event of propeller damage, no occupants and no vital part of the machine can be hit by departing pieces. The carburettors can all be overlooked by the guide through sight holes in the body and can be easily monitored.
In the Priifungstliigen, extraordinarily good performance, especially very good climb times of the aircraft, were recorded. The machine was even used to perform various types of aerobatics, such as rolls and loops, which proved to be extraordinarily manoeuvrable and safe. In the test report of the German Aviation Research Institute, Adlershof, it says: The aircraft can still be flown straight ahead with a failing engine with low forces.14 This performance is all the more remarkable because there are only a few aircraft today that can continue to fly if an engine fails.