Propeller
A propeller is a propeller on an aircraft . It is used to generate propulsion (thrust) from the shaft power of an aircraft engine or a shaft turbine .
technology
In principle, propellers can be rigid or adjustable in pitch ( variable pitch propeller ). Propellers have usually have two or more sheets with a profile are provided. In special cases, single-bladed propellers are also used, where a mass balance is provided on the opposite side. Propellers can be placed in front of the engine (pulling propeller, pull propeller ) or behind it (pushing propeller, pusher propeller ). Wood, plastics or metals are used as materials. The streamlined fairing of the hub , on which the propeller is connected to the axis of the drive motor, is called the spinner.
The required torque of a propeller increases with the square of the speed, the power consumption increases to the 3rd power. The efficiency of a propeller depends on the speed of the aircraft as well as on the speed of the propeller. It corresponds to the ratio of the product of thrust and speed to the absorbed shaft power. Efficiencies of up to about 90% are achieved. The highest speed that can be economically achieved with a propeller is around 700 km / h for an aircraft . In order to adapt the drive speed to the optimal propeller speed, a propeller gear is required in some aircraft .
Adjustable propellers are often equipped with an automatic pitch adjustment, which allows their speed to be kept constant even with changed shaft power. In the event of a motor failure, these propellers can be moved into a feathered position in order to keep the air resistance low. They can be set to reverse thrust to support the wheel brakes and for maneuvering. They create a forward thrust. The adjustment is usually done hydraulically or electrically .
Some propellers are in the range around the hub around with electrical heater elements provided for ice formation to be prevented. In the outer area, the resulting frictional heat is so high due to the higher peripheral speed that ice can no longer settle there. Ice accumulation is a danger in aviation because of the increase in weight and because of the change in the aerodynamic profile .
A propeller jet - the air set in motion by a propeller that generates the thrust of an aircraft - can reach speeds of several hundred km / h and is dangerous for people and objects. Therefore, a safety distance behind a propeller is essential.
history
Airship
At the turn of the 19th and 20th centuries , the native Brazilian Alberto Santos-Dumont built a number of bulging airships in France . In 1894 he first used the gasoline engine of his tricycle for the propeller of one of his airships. Ferdinand Graf von Zeppelin carried out experiments with a propeller boat since 1896 in order to gain experience in the efficient use of the propellers with which the first two Zeppelin airships were powered.
First flight of an airplane
Karl Jatho noted in a notebook for August 18, 1903 an "air jump" on the Vahrenwalder Heide near Hanover . In August 1933, 30 years later, four eyewitnesses are said to have given notarial confirmation. No information is available about the whereabouts of these confirmations and the authenticity of the notebook. His “flying machine”, a 12-HP double-decker equipped with a propeller with a 36 m² wing area, flew “18 meters at a height of three quarters of a meter”. Jatho describes improvements in his performance over the course of the following three months up to a flight of 80 meters at a height of up to 2.50 m.
Wright brothers' first controlled flight
The Wrights made propellers with a high degree of efficiency and, since a suitable engine was nowhere to be found, had one made in a bicycle factory. Within a very short time, a water-cooled four-cylinder four-stroke petrol engine weighing just under 110 kg was created and delivered 12 hp. To compensate for the moments, the flying machine was fitted with two propellers rotating in opposite directions, which were driven by roller chains that ran in tubes to avoid vibrations.
On the morning of December 17, 1903 , Orville Wright took off on his first flight with the Flyer . He was in the air for 12 seconds and covered 37 m (10.8 km / h). Wilbur immediately followed, each flying twice that day. Wilbur managed a flight of 59 seconds and 260 meters of flight distance (19 km / h). Orville later said of it that it was the first time in history that “a machine with a human had raised itself in free flight by its own power, flown forward in a horizontal orbit, and finally landed without going to the wreck become". The flying machine measured 12.3 m in wingspan, 6.4 m in length and 2.8 m in height, it consisted of wood and a fabric covering, its flight weight was 340 kg and the pilot lay unchanged on the lower wing.
Fastest propeller-driven aircraft
The sources as to which propeller-driven aircraft is the fastest or how fast it can fly in each case is inconsistent. The Soviet Tupolev Tu-114 airliner , which went into service in 1961 and is powered by four turboprop engines , is often the fastest propeller-driven aircraft at 871 km / h. It was a further development of the Tupolev Tu-95 strategic bomber . Often, however, the Tupolev Tu-95 itself or the sea reconnaissance aircraft Tupolew Tu-142 derived from it, with various alleged top speeds of 910 km / h to 930 km / h, is named as the fastest propeller-driven aircraft.
The fastest propeller airplane powered by a piston engine is a modified F8F-2 Bearcat . In 1989 a speed of 850 km / h was reached.
Biggest propeller
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For the Linke Hofmann R.II , the prototype of a long-range bomber of the German air force in the First World War , a propeller with a diameter of 6.90 m driven by four motors was used.
Web links
Individual evidence
- ↑ [1]
- ^ Fédération Aéronautique Internationale (FAI) - General Aviation World Records . records.fai.org. Archived from the original on October 7, 2007. Retrieved December 12, 2010.
- ^ Guinness World Records . Guinness World Records. Archived from the original on September 24, 2015. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved December 12, 2010.
- ^ Guinness World Records . Guinness World Records. Archived from the original on September 24, 2015. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved December 12, 2010.
- ↑ Archived copy ( Memento of the original dated May 7, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
