Talk:FVA-18

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A glider tug on 40 hp I don't think so!!! If you google translate the page on the FVA-18 on the FVA website:-[1] You will soon discover that it was more akin to a Motor-glider, not a Glider-tug. Two very different animals (except that some more powerful motor-gliders are now used for aero-towing).

This is the google trans;ation FVA-18 "Primitivkrähe"

 # Engine aircraft for training purposes in lightweight handling qualities with gutmtigen
 # 1965 First Flight
 # Technical Characteristics: Extremely light weight (250kg) and homemade gear
 # 1971: Presentation on OUV meeting. Raises interest from.
 # Problems: Engine difficult to start, loud gear noise

A gutmtiges engine training aircraft End of the fifties, the opinion prevailed in the FVA, each student should have aircraft after studying also a private pilot certificate in his pocket. As the cost of that engine machine D-Emyr were too high for the budget of a student, it was decided to develop a lightweight, inexpensive engine aircraft with flight characteristics harmless for the training and exercise. When construction is offered to the mixed material, as was customary by the glider. Regarding the cell could be found of the Emyr (PiperJ 3C) inspire ".

The engine Since everything depends on one engine aircraft engine, had a useful first be obtained. The American engines were too expensive, and so we turned our attention to the Pollmann-flight engine, developed from the VW engine and having an average output of 30 HP at a speed of 3,200 rpm gave. To achieve now to get a double seater aircraft with a launch power of just over 30 hp in the air, had the available engine performance is optimized.

By careful selection of the propeller was able to bring the propeller efficiency of 0.78 on the Wen at a progress 0.2.

To achieve this good value, it was necessary to the propeller by a relatively large diameter to give. It amounted to 2.15 m.

Also min had to have the speed of the engine to 1,100 U lower. Only this should be done by one of the company for the motor supplied Keilriemenuntersetzung Pollmann, which turned out to be unusable. So had a gearbox to be developed, which supplied the necessary Drehzahluntersetzung of 2.85: l by a helical spur gear of the FVA.

Minimalist design In conventionally designed structure - steel tube fuselage and wing piece aspired - an extreme lightweight stand in the foreground. Stingy with every gram of weight. File off any excessively long screw, scraping off any drops of glue, however, had paid off: 250 kg empty weight for a double seater engine airplane with a wingspan of 10.50 m and a body length of 6.70 m were not commonplace.

Pending the completion of construction of the aircraft was a lot of difficulties to overcome. It had several strength tests are made, such as wing loading tests. The wing handles were examined at the Institute for Building Research on buckling strength.

The left with a weight of 90 kp fairly serious engine plant, the flight weight increase to 430 kp. 400 kp once planned to achieve but requires an enormous additional expense would have been. Moreover, while the demand for simplicity and less expensive construction was no longer tenable.

The fuselage width of the FVA-18 was only 0.67 m. They had chosen not least because so little to keep the radiation loss of the propeller against the hull low. However, it turned out later that in this weighty fellow passengers with a fuselage width of the rudder pedals of the pilot (the pilot was sitting in tandem behind the co-pilots) came in contact.

Transverse and elevator load testing and suspension drop tests completed the test series. s been up to the FVA-18 aircraft in the category of "Normal" (load factor = 3.8) were fully approved by the American building codes CAR-Part 3 was next calculation notes had about 300 pages of mathematical proofs are geliefen strength.

Testing phase The flight tests were in accordance with the provisions of the Civil Aeronaurics Manual (CAM) "and after the" Flight Test Report conducted Guide ". Herein are subject to each flight phase and flight situation clearly defined requirements.

The flight test had to prove that the characteristics and performance of the aircraft move in this framework. Deviations should be detected and eliminated during the testing.

The testing of the self-constructed transmission extended mainly to the reliability. This had to be to determine wear or replace bearings and leaking oil seal for better control of cut at fixed intervals.

The rolling tests had already shown positive results, such as short distance to the roll-off, easy handling and sufficient action of the self-developed disc brakes. With jumps of 100-200 m length to 2-5m height were already before the actual flight rudder effectiveness good, balanced rudder coordination and pleasant hand forces are determined. But it turned out soon that the propeller pitch was chosen too low. The motor speeds were in the state at full load at 3400-3500 rpm, so the engine at take-off speed already strung. A new propeller was given at the Hoffmann commissioned.

Technical problems The first flights were chosen to determine the normal behavior of the FVA-18. It rose after a few minutes' flying time the oil temperature to exceed the permissible limit. Also could with the breather of the transmission oil spray on the windshield.

The gear was at engine speeds below 1,800 rpm, loud noises, which, as it turned out, also due to misfiring of the engine were. Based on our metal shavings in the oil were thrown out, the gearbox was taken apart after just 20 minutes flying time. The helical Evolventenzahnräder had shifted by 4 mm, and beat each other in one distance ring.

Improvements A newly-designed additional spacer ring which prevented a migration of the gears against each other, and the transmission was much calmer. The next flights were still the measurement of oil and cylinder head temperature. Additional baffles increased the oil cooling for the level flight at a constant temperature of 90 ° C. When they climb ranged from limited. It was necessary to achieve greater heights, Horizontalflüge insert for cooling.

Flight services With a weight of 380 kp following flight services were flown:

Travel speed: 100 km / h at 3200 rpm 90 km / h at 3000 rpm Lift-off distance: 40 m Off distance of 15 meters: 120 m Rate of climb: 2.10 m / s Altitude reached 2500 m Fuel consumption: 9 l / h Range: 380 km / h

Überziehversuche at cruising speed was slowly tipping forward with very little loss of height (about 20 m). The plane started off with a fully rifled Hörhensteuerselbst, as the flow on the wing once again docked.

At idle, the tilt was a little faster, the plane went by preference on the left wing in a Schiebezustand. It was easily in the back by Gegensteuermaßnahmen Normalflugzustand.

The first attempts at medium spin balance could be initiated by Normalsteuerausschläge and again expelled. The FVA-18 turned it to 1 / 4 to 1 / 2 turn. The spin was hardly different from one with Steilkreis Minimalfahrt.

The next flights were carried out with maximum allowable weight in flight. After a Fahrtmesserreichung have not yet flown the following: Front and rear center of gravity with the appropriate service behavior, service ceiling, landing distance, longitudinal stability, price stability, spin and flutter. The flight test was to Professor Dr.-Ing. AW Quick conducted at the Institute of Aerospace in the thesis of Freddy Schliewa.

The crow would have the stuff that is a popular club aircraft had the homemade gear had not been so noisy and restless, and restart the motor something simple. But as the crow stood mostly sad in the hall, while the glow engine pilots mostly conducted tow flights.

Reactions to the "crow" In 1971 she was flown to the meeting of the Oskar-Ursinus-Vereinigung (OUV) in Egelsbach. where she was much respected:

"The next day asked the representatives of the FVA Aachen their" Primitivkrähe - FVA-18 before. Of the flying qualities of this bird, which bears because of its simple construction, the right name, were able to convince all interested parties themselves, by participating in the stick set and with the crow in the air went. Conclusion of the presentation of the aircraft from Aachen: Everybody talks about the replica aircraft to the club - we have it. Only interested in (yet) any of this. " (From German Aerokurier, Issue 8, 71, p. 556 OUV Report on Meeting)

Especially the low minimum speed of 55 km h and the harmless stall impressed so much that the present Tragschrauberpiloten before comparing flying "pinched". The simple construction aroused the interest of the hobby aircraft. In the following years have been answered countless questions and made ten sets of drawings to interested parties.

Petebutt (talk) 14:15, 15 September 2010 (UTC)