Gerner G II R

{{short description|1930s German light aircraft}}  {{Infobox aircraft | name = Gerner G II | logo = | logo_size = | image = Gerner_II_at_the_1933_Deutschland_Flug.png | alt = | caption = | long_caption = | other_names = | aircraft_type = Sports, touring and training | aim = | outcome = | related = | national_origin = Germany | manufacturer = Flugzeuge Max Gerner/Adler Werke | design_group = | designer = Max Gerner | builder = | issuer = | status = | owners = | primary_user = | more_users = | service = | major_applications = | proposals = | prototypes = | number_built = 54 | construction_number = | civil_registration = | military_serial = | radio_code = | requirement = | aircraft_carried = | flights = | total_hours = | total_distance = | construction_date = | introduction = | retired = | first_flight = spring 1931 | initiated = | in_service = | last_flight = | expected = | developed_from = Gerner G I | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = }}

The '''Gerner G II''' or '''Adler-Gerner G II''' was a German steel framed, low power biplane, intended both for sports and training in the early 1930. Over fifty were built for clubs and private owners.

==Design and development== Max Gerner's G II R sport, touring and training biplane was a development of his one-off G I. The two types had low cost, easily repaired structures built from proprietary steel tubing and unswept, constant chord wings with two truss braced spars; both had lattice girder fuselages and were largely fabric covered. Both also had open, tandem cockpits, fixed undercarriages and a single engine. However, the G II R was larger, heavier and had a choice of engines which typically doubled the power. The fuselage was lengthened, mostly by increased cockpit separation, strengthened with diagonal cross members between the longerons, which placed the rear cockpit behind, rather than over, the trailing edge. These changes raised the weight by 25% and so wing area was increased by extending the span by 20%. The G II R retained the N-form interplane and cabane struts of the G I, though the former no longer leaned outwards and the upper wing was somewhat higher over the fuselage. It had two extra inter-spar trusses (six rather than four) in its lower wing, which alone carried ailerons. A newly patented method cramped, rather than welded, trusses and spars together. The G II R was easier to transport as it wings could be folded parallel to its fuselage despite the move of the fuel reservoir from behind the engine firewall to the top of the upper wings, for it now consisted of two side-by-side tanks, one on each wing.<ref name=Kens/>

G II Rs were powered by several different engines, some radial engines and some inverted inlines, but the prototype first flew with a {{convert|45|hp|kW|abbr=on|0|order=flip}} Salmson 9 AD, a small, nine cylinder radial. Later this first example flew with a {{convert|50|hp|kW|abbr=on|0|order=flip}} five cylinder BMW X. The Salmson was installed with its cylinder heads completely exposed but the wider spaced heads of the BMW protruded from a rounded cowling. The G-II RB and RC production aircraft had four cylinder Hirth HM 60 inverted inlines, producing {{convert|60|hp|kW|abbr=on|0|order=flip}}, or the {{convert|80|hp|kW|abbr=on|0|order=flip}} Hirth 60 R racing version. Behind the nose the G I and G II R fuselages were similar, with flat sides and rounded tops, apart from the increased inter-cockpit spacing. The G I and G II RB empennages also shared the same constant chord surfaces with semicircular tips. Early G II Rs had the same single axle main undercarriage and tailskid as on the G I but this was altered on from the G II RB onwards to one where each main wheel was mounted on a V-form strut mounted on the central lower fuselage, with a bungee shock absorber from the stub axle to the upper longeron. The tailskid was replaced with a small wheel on a sprung strut.<ref name=Kens/>

Early in 1934 responsibility for the Gerner II R was taken over by Adler Werke, who produced cars and motorcycles; they retained Max Gerner as designer.<ref name=Kens/> Subsequently the aircraft were sometimes called Gerner Adlers or just Adlers.<ref name="Flight2" />

Investigations into two serious accidents in 1933 and 1934 concluded that the G II R's deep, over-wing fuel tank could blank airflow over the tail and cause loss of control. The result was the G II RC, which had a shallower tank and revised tapered and broadened tail surfaces. Its elevators were fitted with trim tabs. The new tank moved the centre of gravity significantly rearwards and to compensate the wings were swept back at about 8° and broadened ailerons fitted.<ref name=Kens/>

==Operational history==

The second G II R, the first production example, appeared at the Düsseldorf contest in 1931. Though it did not compete, it flew part of the course. The design gained aristocratic support from Hermann-Otto Graf zu Solms aus Lich. Over the next few years he bought four G II R variants and flew them competitively.<ref name=Kens/><ref name=Flight1/> Four G II Rs were entered in the 1933 Deutschland Flug ({{langx|en|Germany Flight}}) though only two, including his, competed. In 1934 two more G II Rs took part and Solms, with his navigator W.H. Storp, won. The two machines returned for the 1935 contest. The following year he was flying a G II RC in Olympic flights and in Belgium.<ref name=Kens/>

In September 1934 a G II RC visited the UK at Lympne in an international competition.<ref name=Flight2/> In a 1936 rally at Lympne, two examples visited, one with the front cockpit faired over. There is colour film of the event.<ref>{{cite web |title=1936 Lympne International Air Rally - Colour Film |url=https://www.youtube.com/watch?v=URv-rBcrQYg&t=3s |website=YouTube |access-date=26 January 2025}}</ref>

Flights like these attracted notice and the Gerner aircraft looked to sell well with clubs, justifying Adler Werke's investment. In the end only 53 production machines were completed, the majority G II RBs. Sales of the C variant were disappointing; the accidents may have played a part but there was also a move in the now nationally organised flying clubs towards aircraft with rather more powerful engines.<ref name=Kens/>

[[File:Gerner II at Lympne.png|thumb|G II RC visiting Lympne, UK in 1934]]

==Variants== ;Gerner G II R: Single prototype with Salmson 9 Ad and BMW X radial engines. ;Gerner G II RB: Hirth HM 60 or Hirth HM 60R engine. 40 built. ;Adler-Gerner G II RC: Revised tank, swept wings, new undercarriage and empennage. 13 built.

==Specifications (G II RC) == {{Aircraft specs |ref=''Historische Deutsche Flugzeug bis 1945''<ref name=Kens/> |prime units?=met  |genhide=

|crew=Two |length m=6.32 |length note= |span m=7.20 |height m=2.20 |height note= |wing area sqm=12.50 |wing area note= |aspect ratio= |airfoil= |empty weight kg=295 |empty weight note= |gross weight kg=500 |gross weight note= |max takeoff weight kg= |max takeoff weight lb= |max takeoff weight note= |fuel capacity={{convert|70|L|Impgal USgal|abbr=on}} |more general=  |eng1 number=1 |eng1 name=Hirth HM60R |eng1 type= four-cylinder inverted air-cooled inline |eng1 kw=59 |eng1 note=80 PS |power original=

|more power=

|perfhide=

|max speed kmh=175 |max speed note= |cruise speed kmh=150 |cruise speed note= |stall speed kmh= |stall speed mph= |stall speed kts= |stall speed note= |never exceed speed kmh= |never exceed speed mph= |never exceed speed kts= |never exceed speed note= |minimum control speed kmh= |minimum control speed mph= |minimum control speed kts= |minimum control speed note= |range km=550 |range miles= |range nmi= |range note= |endurance= |ceiling m= |ceiling ft= |ceiling note= |g limits= |roll rate= |glide ratio= |climb rate ms= |climb rate ftmin= |climb rate note= |time to altitude={{convert|4000|m|ft|abbr=on}} in 32 min |sink rate ms= |sink rate ftmin= |sink rate note= |lift to drag= |wing loading kg/m2= |wing loading lb/sqft= |wing loading note=

|power/mass= |more performance= *'''Landing speed:''' {{convert|65|km/h|mph kn|abbr=on|0}} }}

==See also== {{aircontent  |see also=*Volksflugzeug |related= |similar aircraft= |lists= }}

==References== {{Commons category|Gerner G II R}} <references>

<ref name=Kens>{{cite book |last=Kens |first=Karlheinz |date=2011 |title= Historische Deutsche Flugzeug bis 1945 band 1|trans-title=Historic German Aircraft before 1945 |language=de |location=Baden-Baden |publisher=Modellsport Verlag GMBH|pages=97–107 |isbn=978-3-923142-39-2}}</ref>

<ref name=Flight1>{{cite magazine |date=31 August 1933 |title= The Deutschland Flug 1933|magazine= Flight|volume=XXV |issue=35 |page=581 |url= https://archive.org/details/Flight_International_Magazine_1933-08-31-pdf/page/n7/mode/1up?q=Gerner }}</ref>

<ref name=Flight2>{{cite magazine |date=6 September 1934 |title= International Meeting at Lympne|magazine= Flight|volume=XXVI |pages=922–3 |url= https://archive.org/details/Flight_International_Magazine_1934-09-06-pdf/page/n11/mode/1up?q=Gerner }}</ref>

</references>

Category:1930s German sport aircraft Category:Single-engined tractor aircraft Category:Biplanes Category:Aircraft first flown in 1931