Inverted flight

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Inverted flight with an ASK21
Air show in Salzburg

The inverted flight is a flight condition in which an aircraft is flown upside down on his back. This attitude is achieved by turning the aircraft halfway around the longitudinal axis (half roll) or around the transverse axis (half loop). The perfect control of inverted flight is a prerequisite for all higher aerobatic maneuvers .

Requirements and execution in detail

In inverted flight, the pilot is pulled into the seat belts by gravity towards the ground. For a stable flight position, the elevator has to be pressed on most aircraft, i.e. the control stick has to be pushed forward by the pilot. Otherwise the aircraft will dive into a dive.

Inverted flight is not possible without problems with every aircraft. The biggest problem with powered aircraft is the lubrication of the engine , which must also be guaranteed in inverted flight . This applies to both piston engines and turbines. This usually requires special dry sump lubrication , whereby the engine is lubricated by an oil pump from an external oil tank regardless of the flight position. Motorized aircraft without such a lubrication system may only be flown on their back for a few seconds, as the oil in engines with wet sump lubrication leaves the suction area of ​​the oil pump in inverted flight and the engine can be damaged by insufficient lubrication. A special fuel tank is also required for powered aircraft. The drain opening of the tank is usually at the lowest point in normal flight. From there the fuel is forwarded to the engine. In inverted flight, however, this point is at the highest point of the tank, which means that no fuel can get from there to the engine. That is why a small additional tank is often installed in aircraft that are supposed to be suitable for return flights. This is mounted in such a way that the fuel flows inverted from this tank to the engine. Other solutions are the supply of the fuel via a pump system and a tank with several drainage openings or a pendulum hose: a soft hose that hangs in the tank with a weight. Like liquid fuel, this weight follows the force of acceleration. Therefore, the end of the fuel hose should always be in the fuel. Even if there are specially designed carburettors suitable for backflighting, injection engines are usually used nowadays in aerobatics.

Fixed-wing aircraft can basically be flown with any profile shape on the back, but some profiles are better than others. With an asymmetrical wing profile, the lower lift coefficient in inverted flight is compensated for by a higher speed. It is important that the rudder remains sufficiently effective in the supine position to be able to roll the aircraft back into the normal position. This is not guaranteed with all aircraft.

With man-carrying rotary wing aircraft (helicopters, gyroscopes) it is not possible to fly in a stable inverted position, as these (in contrast to many radio-controlled models) can achieve either no negative effective angle of attack at all or only too small negative effective angles of attack due to blade adjustment on the main rotor, depending on the pattern thus cannot generate negative thrust or insufficiently negative thrust.

history

Gerhard Fieseler demonstrating an inverted flight in June 1932 in Berlin

During training for the outside loop , Gerhard Fieseler recognized that a stable inverted flight position of the aircraft is an indispensable prerequisite for this flight maneuver, since for safety reasons the upward bow had to be trained first, the starting position of which is a horizontal inverted flight. In order to be able to perform safe inverted flight, he first developed a tank and carburetor system for his Raab-Katzenstein Schwalbe in June 1927 , with which the aircraft was suitable for reverse flight. At the Zurich aerobatic competition from August 12 to 21, 1927, he set a new world record with this machine in inverted flight of 10 minutes 56 seconds.

swell

  1. ↑ Flight September 1, 1927, pp. 608ff

literature

  • Gerhard Fieseler: My path in the sky . (Autobiography). Bertelsmann Verlag, Munich 1989, ISBN 3-570-01192-5 .
  • Ernst Götsch: Aircraft technology . Motorbuchverlag, Stuttgart 2003, ISBN 3-613-02006-8 .

See also