DIY aircraft

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Rutan Long-EZ , British kit plane from 1984

A DIY aircraft , even DIY Aircraft , Kitflugzeug or aircraft kit is an aircraft that has been certified to be produced for the most part in non-commercial DIY and their own continuing education or leisure activity serves. It can be an in-house development, a construction according to given plans or a kit . In Germany , kit aircraft are approved by the Federal Aviation Office as individual pieces. For this, certain requirements must be observed. For example, the aircraft must have been manufactured predominantly, i.e. with an own share of at least 51% of the construction work, itself and within the Federal Republic of Germany and exclusively for the purpose of personal training and leisure activities. Kit aircraft built abroad are therefore not permitted in Germany. This rule also applies accordingly in the United States , Brazil , Australia , New Zealand and South Africa .

General

Do-it- yourself aircraft are generally simply constructed, one- to four-seat small aircraft . They mostly consist of fabric-covered or plywood-clad wooden or metal frames. But also are increasingly fiber reinforced plastic and other composite materials and aluminum designs in use that are already at the time of the First World War by Hugo Junkers were explored. The engines are mostly the same or similar to those used in conventional aircraft. These include engines from Lycoming , Continental and Rotax . A small proportion of the self-construction aircraft use modified automobile engines . Engines such as air-cooled four-cylinder from Volkswagen , water-cooled engines from Subaru , rotary engines from Mazda and the six-cylinder from the Chevrolet Corvair are popular here. While using car engines reduces costs, many do-it-yourself builders prefer aircraft engines because they are considered more powerful and reliable. Chainsaw and motorcycle engines have also been used for kit airplanes.

history

Pietenpol Air Camper
Mignet Pou-du-Ciel HM-8

The history of do-it-yourself aircraft goes back to the beginnings of aviation . The Wright brothers , Clément Ader and their successors drove on while commercial interests, but the first aircraft of passionate enthusiasts were built, who dreamed of flying.

Early years

In the United States, the industrialization that accompanied World War I gave aviation a major boost. As manufacturers had to open up new markets in the post-war period, they began to develop travel aircraft. However, only the very rich could afford this.

Many aircraft developed from the 1920s onward have been classified as unique pieces by the Civil Aeronautics Authority , a predecessor to the Federal Aviation Administration . In 1928 Henri Mignet published the plans for his HM-8 and Bernard Pietenpol for his Air Camper . Pietenpol later set up a factory and began selling prefabricated aircraft kits in 1933.

In 1936 an association of aircraft self- builders was founded in France . After more and more self-made aircraft were produced, a change in the law was passed in 1938, which introduced the Certificat de navigabilité restreint d'aéronef 'Certification for the restricted operation of aircraft' . In 1946 the Ultralight Aircraft Association , the forerunner of the Light Aircraft Association , was founded in the United Kingdom . 1953 followed the Experimental Aircraft Association in the United States and the Sport Aircraft Association in Australia .

In Germany, on the other hand, the self-construction of aircraft was repeatedly exposed to great difficulties in the beginning. Due to the flight bans after the First and Second World War , such activities were slowed down again and again and in the former GDR these difficulties lasted until the end of the 1980s.

In the 1930s, the self-building of aircraft began on the Wasserkuppe . Above all, the construction of gliders was promoted, but the construction of the first powered aircraft also took place here. During this time, Oskar Ursinus first published plans according to which it was possible to build an airplane yourself. During the Second World War and during the time of the occupation by the Allies , building it yourself was practically impossible and after the relaxation of aviation restrictions in 1955, it took thirteen years until the Oskar Ursinus Association for the Promotion of Do-It-Yourself Aircraft was founded on March 9, 1968 . But even after it was founded, the self-construction of aircraft in Germany did not gain momentum. In the first few years the authorities only allowed the construction of new developments. Developments based on commercial interest, such as the sale of construction plans, were not permitted. Only after this regulation was lifted and it was only stipulated that more than fifty percent of the project had to be carried out by the self-builder did the self-construction take off in Germany. The ability to build an airplane using a kit drove the number of self-build projects up. This boom reached its preliminary peak in the late 1990s.

Technical development

Until the late 1950s, do-it-yourself aircraft were mostly made of wood or metal covered with fabric. Since do-it-yourself aircraft were not subject to the same restrictions as the aircraft industry, innovative designs and construction techniques were developed in this area. Burt Rutan introduced canard design into the field of kit aircraft and pioneered the processing of composite materials. In the do-it- yourself sector, some jets such as the Bede BD-5 have even been developed since the 1970s .

construction materials

In principle, a kit airplane can be built from any material that is light and stable enough to fly. Various common materials are described below.

Wood and textile

Bowers Fly Baby , typical example of a structure made of wood with fabric covering
Frame of a Pietenpol Air Camper
Metal hull of a Murphy Moose
Lancair 235 made of GRP

Wood and fabric are the oldest and therefore also the most common materials that were used in aircraft construction. Therefore, there are most specialists in this type of building material.

Spruce wood is the most commonly used because it has an extremely good strength-to- weight ratio . Components made of wood are joined together using adhesives - usually epoxy resin . In contrast to wooden structures in other areas, practically all wooden connections in aircraft construction are simple butt joints with plywood reinforcement. The connections are designed to be stronger than the parts they connect. The finished wooden frame is covered with textile fabric - mostly polyester . The advantages of this type of construction lie in the use of simple tools and equipment such as saws , planes , files , sandpaper and screw clamps .

Examples of do-it-yourself aircraft made of wood and textile are

Wood and composite materials

A newer method is the use of wood in combination with composite materials . The basic structure is still made of wood, but it is combined with foam ( e.g. to increase the resistance to buckling of load-bearing plywood cladding) and other synthetic materials such as GRP or CFRP (to increase the modulus of elasticity of load-bearing parts).

Examples of this method are

metal

The construction of kit airplanes made of metal uses methods and techniques similar to those used in the construction of conventional, industrially manufactured airplanes. The construction is usually more demanding, because techniques for cutting, shaping and riveting metal are required if only plans are to be used. However, so-called quick assembly kits are also available, which already contain cut, shaped and pre-drilled parts, so that only fine-tuning and assembly are required. Such quick assembly kits are also offered with other materials - especially composite materials. There are three main types of metal structures: aluminum sheets, aluminum tubes, and welded steel tubes . The pipe constructions are covered with a suitable fabric like the wooden constructions.

Examples of kit airplanes are made of metal

Composite materials

Constructions made of composite materials usually consist of a high-strength fabric made of glass fibers or carbon fibers - rarely also Kevlar - in conjunction with a plastic . The plastic is mostly epoxy and occasionally vinyl ester resin . The tissue is soaked with the liquid plastic. After curing, the finished part retains its predetermined shape and maintains the strength of the fabric.

The two main types of aircraft made of composite materials are, on the one hand, aircraft made of plastic molded parts, in which the wings and fuselage are produced by molding , and, on the other hand, aircraft, the parts of which are cut out of foam blocks and then coated with GRP or CFRP .

The greatest advantages of this construction method are smooth surfaces without the resistance of rivets , the combination of bends and the possibility of optimally shaping the material. Disadvantages are the need to work with chemicals and the low load capacity of the materials across the grain. Composite materials have a very high strength in relation to their weight. In contrast to metals, however, they are not equally resilient in all directions.

Examples of kit airplanes made from composite materials are

safety

General aviation accident rate in the United States in 2003

The safety record of kit aircraft is worse than that of conventionally built general aviation aircraft . In 2003, the United States had 21.6 accidents per 100,000 flight hours. The accident rate in general aviation in the same period was 6.75 accidents per 100,000 flight hours.

The Federal Aviation Administration has long been concerned about the accident rate among self-build aircraft in the United States. At a Sun 'n Fun event in 2010, FAA chief Randy Babbitt said kit airplanes accounted for 10 percent of general aviation but 27 percent of all accidents. It is not the fault of the self-builders of such aircraft, but that of the second owner. Improved differences training is needed.

A 2012 study by the National Transportation Safety Board found that self-made aircraft have an accident rate three to four times higher than the rest of all general aviation aircraft. Almost ten percent of accidents happen during the maiden flight and nine percent during the maiden flight of a new owner. Furthermore, the study found that accidents due to an engine failure and loss of control of the aircraft in flight occur with kit aircraft far more frequently than with flights of commercially manufactured aircraft.

In most countries, the legal regulations require that kit aircraft be specially marked. For example, in the UK, the phrase “ Occupant Warning - This aircraft […] is amateur built ” must be visibly displayed on aircraft. Furthermore, further test flights are usually required before passengers can be carried.

Operation itself is also restricted in Germany. With the exception of take-off and landing, do-it-yourself aircraft may not be flown over crowds of people or over large cities, so that free terrain is always accessible in the event of a fault. Kit aircraft may only be operated during the day and at sight . Night flights and IFR are not allowed. A do-it-yourself aircraft may only fly into the airspace of other countries if the respective state has the appropriate permission. In Europe there are general entry permits for kit aircraft in Austria , Italy , Sweden and Switzerland .

literature

Web links

Commons : DIY Aircraft  - Collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b Testing and approval of self-made individual items according to § 3 LuftGerPV. (PDF) Luftfahrt-Bundesamt, August 2013, accessed on April 25, 2018 .
  2. ↑ Experimental Category - Operating Amateur-built, Kit-built, or Light-sport Aircraft. Federal Aviation Administration, August 6, 2009, accessed April 25, 2018 .
  3. ↑ a b story. Oskar Ursinus Association , accessed April 26, 2018 .
  4. ^ Annual Review of Aircraft Accident Data. (PDF) (No longer available online.) National Transportation Safety Board , 2003, archived from the original on Aug. 24, 2007 ; accessed on April 25, 2018 (English).
  5. ↑ FAA Administrator Babbitt Takes In Sun 'n Fun. AVWeb, April 14, 2010, accessed April 25, 2018 .
  6. ↑ Ron Wanttaja: Amateur-Built Aircraft Safety Study . In: Kitplanes . Vol. 29, No. 12 . Belvoir Publications, December 2012, ISSN  0891-1851 , p. 36 to 41 (English).
  7. ^ Mary Grady: NTSB Completes Homebuilt Safety Study. AVWeb, May 22, 2012, accessed April 25, 2018 .
  8. ↑ CAP 659 - Amateur Built Aircraft. (PDF) (No longer available online.) Civil Aviation Authority, October 1998, archived from the original on May 16, 2004 ; accessed on April 25, 2018 (English).
  9. ↑ FAQ. Oskar Ursinus Association , accessed April 27, 2018 .