Brunswick LF-1 Zaunkönig
Winter LF 1 Zaunkönig
The LF-1 was designed by Prof. Dr.-Ing. Hermann Winter and some of his students from the Technische Universität Braunschweig (English:Technical University of Brunswick), Lower Saxony, Germany in 1939, as a fool-proof trainer for novice student pilots to experience solo flight. Winter was a former chief engineer at the Bulgarian company, DAR (Drzhavnata Aeroplanna Rabotilnitsa in cyrillic ДАР – Държавната аеропланна работилница).
The LF-1 is a parasol wing monoplane with a high-set tailplane, powered by a Zündapp Z 9-092 engine delivering 37 kW (50 hp), able to operate from a 100 m (330 ft) airstrip. The two-piece wings are set at 16° dihedral and are supported by a pair of v cabane struts and v-struts either side from approx half-span to the lower centre fuselage. Full span leading edge slats extend automatically and full span trailing edge flaps / drooping ailerons can be extended manually by the pilot. The fixed tailwheel undercarriage attaches to the fuselage with long struts and oleo pneumatic shock absorbers.
When the flaps were lowered (max. angle 40°), the ailerons also drooped. The Zündapp engine was an air-cooled 4-cylinder engine with single ignition, it produced 51 hp producing a max. airspeed of 87 m.p.h.
It was a proof-of-concept design for a 'fool-proof' trainer intended for novice pilots with only one hour of ground instruction, the hour being reduced to five-minutes for those who had already flown gliders, and was intended to be impossible to either stall or spin.
The first prototype, the LF-1 V1, was built in 1940 and made its maiden flight, piloted by Winter himself, on 17 December 1940 powered by a 51 hp Zündapp 9-092 engine. The flight characteristics revealed a good-natured behavior, while the flight performance confirmed the expectations with a stall speed of 29.2 mph (47 kmh) and a maximum speed in level flight of 87.6 mph (141 kmh). The aircraft was repaired and flown again on July 16, 1941, however, on September 11, 1942, during a flight to determine the roll speed of the aircraft, a second serious accident occurred. During the flight tests, performed by the assistant Franz Glatz, there was an overload of the lateral control system, which then failed. This led to the flapping of the wings and subsequently the loss of the right wing. The pilot managed to parachute to safety, the plane crashed onto a truck parked on the parade ground in Brunswick, and both the aircraft and the truck were a total loss.
In 1943 a second prototype, the V2, was built, again receiving the registration D-YBAR. The aircraft was tested for military applications and was once even armed with a Panzerfaust 100 recoilless anti-tank weapon.
The type was named Zaunkönig (Wren) on February 5, 1944.
The aircraft survived WW II, but shortly before the occupation of the Technische Hochschule Braunschweig by Allied troops in April 1945, all aircraft documentation was destroyed. In 1945 groups of specialist units were capturing German secrets and technology. Eric ‘Winkle’ Brown led a British aviation team and managed to fly most of the Luftwaffe’s aeroplanes, from the Messerschmitt 163 rocket fighter to the Blohm und Voss 222 6- engined flying boat. One less exotic type he encountered was the Zaunkönig (Wren). An example was brought back to England for thorough testing.
The Zaunkönig registration D-YBAR was taken to the Royal Aircraft Establishment (RAE) at Farnborough for slow flying tests; given the British serial VX190, where amongst others, it was flown by Eric "Winkle" Brown CO Aero Flight, the aircraft also being soloed by the then-head of the RAE Aerodynamics Section, Handel Davies, whose previous experience was as a pupil in a dual-control Miles Magister, after a half-hour of ground instruction.
Most of the pilots found flying the Zaunkönig ‘an interesting experience’. Getting into the small cockpit close under the wing was quite a gymnastic manoeuvre. The engine started easily and with no ignition check or elevator trimmer it was soon time for take-off. The briefing was that flap position was ‘anywhere you like’ and on opening the throttle the aircraft ‘cannot fail to fly itself away’. It left the ground at 44 m.p.h. flaps up or 31 m.p.h. flaps down. The lack of trimmer was not a problem as all three controls were light and pleasantly balanced. Approach to land was at 45 m.p.h. flaps up or 40 m.p.h. flaps down. There was no need to flatten out. The aircraft approached in a three point attitude and the pilot could be told to ‘wait until the ground hits the aircraft’. The undercarriage was strengthened to allow it to absorb the shock of the widest range of landing techniques - or should that be lack of technique.
‘Stalling’ tests were carried out with wool tufts attached to the upper surface of the wing. These were filmed from a following helicopter and showed that, at about 30 m.p.h., engine off or engine on, the centre section of the wing stalled but the outer section went on flying and the ailerons continued to give full lateral control. The Zaunkönig effectively ‘turned into a parachute’.
After being wrung out at Farnborough, there seemed to be no useful military function for the Zaunkönig and it was tested by the Civil Aviation Flying Unit of the Ministry of Civil Aviation at Gatwick. There were ideas of using it to promote the expected surge in private flying so it was sold to a British private owner in June 1949 as G-ALUA, and then to the Experimental Flying Group and to the Ultra Light Aircraft Association.
It toured the flying clubs whose members could fly it for £1 per hour. However, it caused little excitement and passed through the hands of several private owners including one in Ireland. At one stage, it was rebuilt by John Isaacs (noted for his own designs of a mini Hawker Fury biplane and mini Spitfire).
It was subsequently sold in 1974 to an Irish owner, being registered EI-AYU, returning to Germany, in 1976, as D-EBCQ. As of 2008, it was preserved in the Deutsches Museum collection at Oberschleissheim near Munich.
The second Zaunkönig D-EBCQ preserved in the Deutsches Museum, Oberschleissheim, in July 2008.
Encouraged by the positive British reviews Prof. Ing. Hermann Winter decided to build a third LF-1. The construction started in 1954 and it was the first new aircraft in Germany after the war to receive a certificate by the Luftfahrt-Bundesamt (LBA) in Braunschweig and the registration D-EBAR. Winter envisioned the Zaunkönig as a People's Aircraft affordable for all (for a price of around DM 6,000). On 28 April 1957, the wartime Luftwaffe fighter ace Heinrich Bär was conducting a routine flight check in the D-EBAR. Bär put the aircraft into a flat spin, the final manoeuvre in the test process at Braunschweig-Waggum. The aircraft spun down to 50 m (160 ft) then, unable to regain control, it crashed and Bär received fatal head injuries. The aircraft was damaged beyond repair and written off.
At the time a fourth LF-1 V4 was already under construction and it flew a few months after the fatal accident with the V3, in the summer of 1957. It received its certificate in 1958, it expired on October 8, 1964, when the aircraft was grounded, and the code D-ECER. This aircraft flew for some years in Germany until grounded after the death of Prof. Ing. Winter in 1968. In November 1979 it was registered again, this time as D-EBCG, restored in 1980 and flew until 1999 as D-EBCG. Tthe registration was cancelled on October 15, 1999. As of 2008 it was preserved in the collection of the Internationals Luftfahrtmuseum Manfred Pflumm near Villingen-Schwenningen.
Engine: 1 × Zündapp Z9-092, 37 kW (50 hp)
Propeller: 2-bladed wooden fixed pitch propeller, 1.8 m (5 ft 11 in) diameter
Wingspan: 8.02 m (26 ft 4 in)
Wing area: 8.5 m2 (91 sq ft)
Length: 6.08 m (19 ft 11 in)
Height: 2.38 m (7 ft 10 in)
Empty weight: 253 kg (558 lb)
Gross weight: 370 kg (816 lb)
Fuel capacity: 40 l (8.80 imp gal; 10.57 US gal)
Oil capacity: 3.5 l (0.77 imp gal; 0.92 US gal) oil
Maximum speed: 141 km/h (88 mph; 76 kn)
Cruising speed: 125 km/h (78 mph; 67 kn)
Landing speed: 46 km/h (29 mph; 25 kn)
Stall speed: 50 km/h (31 mph; 27 kn)
Slowest flying speed: 29 mph
Range: 450 km (280 mi; 243 nmi)
Service ceiling: 3,820 m (12,533 ft)
Rate of climb: 2.85 m/s (561 ft/min)
Time to altitude: 1,000 m (3,300 ft) in 6 minutes 42 seconds
Typical take-off run: 55 yds
Landing run: 29 yds
Armament: 1x Panzerfaust 100 mounted above mainplane centre section