The Junkers G.38 was a striking sight when first flown in 1929.
It was perhaps the pinnacle of blended wing aircraft design in the interwar period,
at least as far as success goes. It was made during a time when some aircraft designers
predicted that blended wing or indeed complete flying wing aircraft would be
the future – with many passengers housed in these large wings as opposed to a fuselage.
In 1929 this was not a new concept for Hugo Junkers. 20 years previously he applied for
a patent for a thick profile hollow wing design that could be used as a large commercial aircraft.
Way back in 1909 the standard design for aircraft at the time could be summarised as a flying crate,
as the old saying goes. Most aircraft were thin winged biplanes that relied on a mass of wires
and struts, which while effective was not the most aerodynamic of designs. Junkers rejected
this way of thinking, and wanted to bring forward the concept of a large cantilever metal wing,
which as a result of its aerodynamically functional design and thickness would provide an
optimal ratio of lift, drag, and practicability. The first world war allowed Junkers to partly
realise his idea of an internally structured aircraft with all-metal wings, removing the
need for obstructive wires and struts, but he was limited in his designs by military specifications.
After the war he now had the experience and the manufacturing facilities available to realise
his dream of a large commercial aircraft, but this time he was limited by the treaty of Versailles.
In 1920 he began development work on the Junkers JG1, which was a four-engine all-metal transport
aircraft. Construction of a prototype began in 1921, with the outer wing and rear parts of
the fuselage being completed. However, when the allied supervisory board inspected the factory
during their investigations, they demanded work to be stopped and the aircraft scrapped.
Undeterred, Hugo Junkers continued to draw up designs during the 1920s,
but it would not until the end of the decade when he would make another serious attempt, which
would result in the G38, working in collaboration with design engineer Ernst Zindel. In 1927 design
work began on project G40, which was for a postal seaplane that could perform transatlantic flights.
Junkers also developed a landplane variant dubbed G38, and although the German navy was
more interested in the seaplane, Junkers preferred the J38 as he believed it offered more versatility
and he was able to secure funding from air ministry for its construction. From conception
to completion, work on the prototype took just over two years, and in November of 1929 the first
aircraft (identified as D-2000) rolled out of Junkers Dessau plant for its maiden flight. When
it took to the skies on the 6th November 1929, the G38 was the largest landplane in the world.
The dominating aspect of the aircraft was of course the huge,
cantilevered wing – it had a wingspan of 44 meters which puts it slightly wider than that of a B-29.
It was built on a series of tubular frames and struts that were bolted together and attached
directly to the fuselage. To make production, maintenance and transportation easier the G38s
wing was divided into a central section, two intermediate sections and two outer sections.
Covering this structure was the classic stressed and corrugated Duraluminium sheets
that were the hallmark of many all-metal aircraft built in Germany at the time.
Not only did this metal provide strong and effective protection, but it also served to
absorb torsional motion exerted on the wing. Not only was the wing broad, but it was also
incredibly thick. At the root where it mets the fuselage it had a height of 1.9 meters.
This is because it was not just designed as a lifting surface, but as functioning section of
the aircrafts internal structure. Much like the Kalanin K7, which was covered in an earlier video,
the front inner sections of the G38s wing was designed to house people and equipment.
At the front, immediately adjacent to the fuselage and accessed via a passageway, were a
pair of passenger cabins which afforded commanding views through a series of curved windows…hopefully
it came with a warning to passengers who suffered vertigo or a fear of heights.
Further outboard from this was the intermediate sections of the wing that mounted the engines,
the forward portion of each section housing one engine each. These consisted of two
Junkers L55 V12 and two L8 inline-6 engines. The larger engines were mounted as the inward pair,
and the smaller as the outer. Together they provided the G38 with 1971hp, with the more
powerful engines driving four-blade propellers, and the smaller ones driving two blade propellers.
This gave the G38 a maximum speed of 225 k/h and a cruising speed of 180 kmh.
Not only did this section of the massive wing house the engines,
but it also housed them in what could be termed the aircraft equivalent of a ships engine room.
Access was granted via a maintenance corridor that carried on behind the wing passenger cabins, and
this allowed engine work to be carried out during flight – certainly not something a lot of aircraft
then or now could boast. The corridor behind the wing allowed it to be accessible for inspection
almost up to the very wingtips, if the engineers were okay with a tight crawl.
Behind the passenger and engine rooms that were on the leading edge of the wing,
separated by a double fire wall and a lot of metal, there were the main fuel compartments.
This consisted of two rows of fuel tanks with a passageway between them for inspection.
Inward of this, and again behind a double fire wall, were the storage cabins that contained the
requisite luggage and cargo of the passengers and crew- this being accessed by the fuselage.
There was also another luggage and freight holder located on the underside of the fuselage like in
more traditional commercial aircraft, but the thick wings allowed this space to be
reduced for better overall cabin space. The fuselage itself, like the wing,
was constructed from tubular struts and girders covered with an all-metal skin.
The pilot and co-pilot enjoyed an elevated position in a comfortable cabin just above
the nose. In front and slightly below them was a navigation room that also held two passenger seats
right up in the front of the nose- for those who felt extra adventurous. Behind the cockpit was
the chief mechanic’s post, from which the whole power plant and fuel systems and be controlled.
Behind this was the crew cabin and stewards’ room where meals and drinks would be prepared,
and adjacent to this room was a small lavatory. Behind this were two more spacious passenger
cabins and a smoking cabin. The passenger accommodation was considered to be luxurious,
and it was intended to compete with the standards found aboard the Zeppelins, which were at the time
the pride of German commercial aviation. Like many other Junkers aircraft at the time,
the G38 featured control surfaces that went along the full span of the trailing edge of the wing.
They were split into two sections, this allowed them to be operated as flaps on the inner section,
and ailerons on the outer section. The tail control surfaces were arranged in a bi-plane style
configuration, with three vertical rudders. This was done in response to the consideration of drag.
If a single large rudder was used, the drag force of the tail wing would have been too great to be
manually countered. All of the control surfaces were dynamically balanced to reduce flutter,
and reports from the test flight praised the G38 for its easy handling characteristics.
The controls of the G38 supposedly felt no more difficult than those of the much
smaller Junkers F13 and G31, which said quite a lot for such a bulky aircraft.
Speaking of bulk, the G38 with its all-metal design, thick wings and four engines,
weighed quite a bit when it was completed - at least for the standards of the time.
It had an empty weight of 13 tonnes and a maximum takeoff weight of 21 tonnes. This was supported
by a main landing gear arrangement of four large wheels that were set in tandem pairs.
For improved comfort and ground handling, these wheels pivoted on the horizonal plane
and were kept in place by a series of springs. The landing gear was in a fixed spatted
arrangement, with shock absorbers built into the vertical frame. Originally this landing gear was
covered by an aerodynamic fairing, but it was at some point removed to save weight,
and then at another point put back on for the sake of style. This seems to go back and
fourth several times during the 1930s which makes dating any unknown photographs a bit difficult.
After its maiden flight the G38 was purchased by the Air Ministry with the intention of
flying it with Lufthansa. It was then put through a series of test and demonstration
flights in which gathered much attention. On the 30th November 1930, test pilots Zimmermann and
Schnizinger set several world records for speed and altitude whilst carrying a 5 tonne payload.
The flight tests concluded with a round trip around Europe, which did much to
stoke enthusiasm for Junkers new aircraft, and then it was officially delivered to Lufthansa.
It then began to run a commercial route between London and Berlin.
Almost immediately after it began flying these routes, however, the decision was made
to modify the G38. The recent press tour had so increased demand for the aircraft that a passenger
capacity of just 13 was considered ludicrous. The engines were upgraded to four L88 V-12s,
which upped the power from 1971hp to 3154hp, and all of them now drove four blade propellers. The
Airframe itself was retrofitted to expand the passenger cabins, which increased capacity to
allow for up to 30 passengers and their cargo. This refit was completed in the summer of 1932
and the aircraft took to the skies once more. Lufthansa also commissioned the construction
of a second aircraft, which would be given the identification D-2500. From the outset it was
designed with lessons learned from the first prototype. It was built with a full two-deck
fuselage and had its wing cabins expanded to allow for a total passenger capacity of 34.
This new aircraft also had the added advantaged of giving most passengers in the central fuselage
a view of the outside world, something that had been missing from the first prototype.
This aircraft entered service around the same time that the first finished its refit,
and they both went into commercial service. The G38s soon earned a very strong reputation
for luxury and comfort. Passengers were allowed to move about freely during flight, and were catered
for by well trained staff. Though their passenger capacity was still somewhat small compared to
their impressive scale, the aircraft quickly became the pride of Lufthansa and German aviation.
In 1933 the D-2500 was given the name “Marshal Hindenburg” in honour of President Hindenburg.
In 1934 both planes received another overhaul, this time replacing all of their engines with
inline six cylinder Jumo 4s, giving a new total power output of 4023hp.
The aircraft were also redesignated, the first being G38A and the second G38E.
Unfortunately for the G38A it would not survive past 1936. It crashed during takeoff
during a workshop flight at Dessaur, the result of incorrectly connected cables. The pilot survived,
but the extensive damage wrote off the aircraft.
The G38E would continue to fly commercial routes for Lufthansa until the start of World War
Two. Then it would be re-painted in wartime camouflage and used as a military transport.
It worked regularly during the military campaign in Greece as a long-range transport aircraft
for troops and supplies, but on May 17th 1941 it was destroyed during a raid by British bombers.
There had been thoughts of a militarised version of the G38 for use with the Luftwaffe,
in fact Junkers had tasked itself to design such an aircraft under the designation K51 but it was
never built…at least not in Germany. As early as 1928, Japan had shown interest in the G38 design
and were indeed the first to approach Junkers about converting the G38 for use as a bomber.
Junkers licenced the design to Mitsubishi in April of 1930
and sent a team over to Japan to oversee and support further development. This was developed
into the type 92, also known as the Ki-20. Mitsubishi manufactured six of these between 1933
and 1935. They were powered by four Jumo 204 engines, had a top speed of 200km/h and could
carry up to 5000kg of bombs. In addition to this they were well defended for a bomber of that era,
mounting five machine guns in various positions and a 20mm dorsal cannon.
When first operated they were the largest offensive aircraft fielded by Japan
and were shrouded in secrecy, but by the height of the second world war they were hopelessly
obsolete and were only ever used as transports. Sadly, none of these aircraft survive today,
having all been destroyed in one form or another, usually involving explosions. But like the Caproni
60, they were recently immortalised in the studio Ghibli movie ‘ the wind rises’.