Immediately after the end of the first world war, aircraft manufacturers across Europe
were scrambling to adjust to the new market of civil aviation.
Many companies folded during this turbulent time, either due to excessive wartime surplus
taxes or simply being too reliant on military contracts – which were now being slashed
left, right, and centre.
In Britain the period between 1918 and 1922 saw the untimely end of several notable manufacturers,
but it also saw the emergence of new companies, some of whom would rapidly become household
names in the field of aviation.
When Airco was compelled to close its doors in 1920, one of its top designers, Geoffrey
De Havilland, decided to strike out and start his own business.
He made the decision to focus most of the company’s early efforts on building civil
designs – a decision that would pay off.
By focusing on the small but rapidly emerging civil market, De Havilland secured itself
a future during a time that saw many other companies close their doors for good, and
the plane that started it all was the little-known DH.29 Doncaster.
Unlike many of De Havilland’s later designs, this was not a success, but it is nonetheless
still important for laying the groundwork the company’s future, as well as being the
first British aircraft built with a thick-section cantilever wing.
De Havilland had begun experimentation with a design that was known as the DH.26, for
which no surviving drawings or photos seem to exist.
The emerging civil aircraft market was already proving to be a highly competitive field,
and De Havilland was looking for something new that would give his designs a decided
advantage.
He knew that one of the biggest areas for improvement would be efficiency, as the cost
per-mile in both fuel and power was already a hugely influential factor, and so he decided
to do away with the drag-inducing, wire-braced biplane design, and try a thick profile monoplane
instead.
This attracted the attention of the air ministry, who then ordered a larger design for research
as a potential long-range transport, and thus the DH.29 Doncaster was born.
The Doncaster took some of its design features from the DH.18, which was the last aircraft
designed by De Havilland during his time with Airco, and the two aircraft would share the
same shock absorbers, cooling system, and fuselage structure.
Like on the DH.18, the Doncaster’s structure was primarily built from wood.
The fuselage was built around spruce longerons, and to keep the main cabin free from obstructions,
a series of cross-struts was employed; this not only kept the cabin space free of internal
bracing, but also served as a suitable mounting point for the undercarriage.
Aside from also having an identical engine, the 450hp Napier Lion, this is where the similarities
end with the DH.18.
The tail surfaces, though similar in appearance, were in fact built to their own design, and
the wing of course was De Havillands new thick-profile monoplane design.
Like the main structure the wing was also built mainly from wood, with the main surface
covered in fabric.
In its original configuration it was fitted with differential ailerons, and also contained
a pair of fuel tanks on the leading edge.
Due to the high placement of the wing, this fuel could be gravity-fed into the engine
without the need for pumps, which helped keep the design simple.
The prototype Doncaster was flown for the first time on July the 5th 1921, with de Havilland
at the controls.
Unfortunately, he had quite the rough time of it.
Firstly, the placement of the engine, the size of the propeller, and the location of
the open cockpit lined up in such a way that de Havilland’s face received the strongest
winds possible during flight.
This also caused damage to some of the doped panels immediately adjacent to the cockpit,
which disturbed the airflow over the central section of the wing and affected performance.
Landing went just as poorly when the ineffectiveness of the rudder became immediately apparent
as the prototype entered an uncontrollable ground loop during landing, drawing a lovely
circle on the airstrip.
In a vain attempt to improve directional control, a new nose was built to raise the engine up
by 20 inches, but this caused problems with the gravity-fed fuel system.
A low-pressure fuel system was installed, and this necessitated the addition of a streamlined
header tank on top of the centre section of the wing.
The elevators were also changed out for horn-balanced units, and it was in this guise that the aircraft
went to Martlesham in 1922 for its initial trials.
During this time, it was modified again, with a series of portholes replacing the old sliding
windows, and a gunner’s cockpit was installed with a scarf ring.
It then, at some point between 1922 and 1924, received the name of Doncaster and this model
was then used at RAE Farnborough for a series of control tests to collect data on the performance
of the thick-profile wing.
Before the first prototype had even flown, a second Doncaster was built, this time as
a purely commercial aircraft as DE Havilland had originally intended.
Ten wicker chairs were installed in the fuselage, with a gangway running down the middle, and
a door at the front of the cabin gave access to the cockpit…the pilot on the original
Doncaster having been forced to use a ladder to get into the plane.
In its commercial form, the Doncaster provided the promise of success that De Havilland had
hoped for.
Even though it was powered by the same engine as the DH.18 biplane, it could carry a heavier
load over a longer distance whilst using less fuel.
Further modifications then raised the Doncasters passenger capacity to 12, which may not sound
like much today, but for a single-engine aircraft in 1922 this was a solid achievement.
Unfortunately, the Doncaster was to be a victim of its own design.
Though it had attracted interest from several companies, other control problems had come
to light which were not fully understood at the time, concerning the new wing, and addressing
them would also take time.
It was also still plagued with the habit of wanting to ground loop during landing.
Though modifications could no-doubt have been made to improve things, the need for new aircraft
in the civil industry was so urgent that several companies placed orders with De Havilland
for the DH.34 instead, which was essentially a biplane that took the best features of the
Doncaster into a more stable package.
In consequence of this, the Doncaster’s chance of civil service was gone.
Its only recorded public appearance was at the Imperial Air Conference in February of
1922, where it featured as purely static exhibit, and in the following November it joined the
first prototype at Martlesham Heath.
Here they both went through a considerable program of test flights, and these made a
considerable contribution to the understanding of the behaviour of thick section cantilever
wings.
That being said, the Doncaster had shown De Havilland that further development work on
monoplane designs was needed before they became a viable commercial option, and monoplane
De Havillands would not take to the skies again until the latter years of the 1920s.
The Doncaster’s direct successor, the DH.34, enjoyed a little more success.
The prototype flew for the first time in March of 1922, and as a testament to the urgent
need for transports, it was entered into passenger service just over a week later.
The first plane was quickly followed by an order for seven more, and carrying up to 10
passengers, the DH34s were used heavily on the cross-channel air routes, with the fleet
completing more than 8,000 hours in the first nine months of operations.
They made a striking impression, and claimed several records in the civil industry, including
being the first civil transport to complete multiple channel crossings in a single day.
By June of 1922, DH.34s were completing five of these trips in a single day, and they were
now also flying services between England and Germany.
When Imperial Airways was formed in 1924, it inherited seven DH.34s from former operations
and kept them in regular service.
Their time in this role was brief, as they were replaced with multi-engine aircraft in
the spring of 1926, but their exceptional reliability and longevity – with one model
logging over 130,000 miles – helped De Havilland to establish an early and excellent reputation
in the industry, one that would secure its future throughout the rest of the 1930s and
1940s.
As always thank you all so much for watching, and a big thank you of course to the Patreons,
with a special shout out to Kevin, Delliardo, Bane, FB, Christopher R, Tronathon, Erik Hindman,
John Austin Jr, Ray Culotta, Keith Tarrier, Greenseaships, Northlincsweb, MCT, and Ted
Parsons for their support as Wing Commander Tier Patreons.
Thank you all so much, and I’ll see you all next time.