Last time we looked at the Hawker Hart, a light bomber that was built in large numbers during the
interwar period. Today, we’re looking at the four major sub-variants that followed it, as the Hart
proved to be a highly capable, highly versatile, and highly affordable design to mass-produce.
These were known as the Hawker Demon, Osprey, Audax, and Hardy. The reason I’m
covering these separately to the Hart itself is because a) they had their own designations,
and b) they often fulfilled roles that was quite different from those
originally intended for the Hart light bomber. Additionally, photos of these aircraft are a
little scarce, so parts of this video may resemble a glorified slideshow, but hopefully that isn’t
too much of a problem and you all enjoy learning about the history of what was a remarkable set
of machines that are often underappreciated for the impact they had on the RAF in the 1930s.
So, we’ll cover them in approximate chronological order – beginning with the Demon.
When the Hart bomber entered service with the Royal Air Force in 1930, it proved to
be faster by a significant margin than any of the current interceptor fighters, and this fact
itself posed a unique training problem during the 1930 air exercises. During the air defence
exercises the RAF's Siskins and Bulldogs were often unable to intercept the new Hart bombers,
which were sometimes instructed to restrict their height and speed to give the fighters a chance,
which for the officers of these fighter squadrons was a little bit embarrassing. Thus,
very quickly it was appreciated that the RAF needed a new fighter, and while a couple other
designs were in development, said development would take time, and many turned to the Hawker
Hart itself to provide a short-term solution. Specification 15/30 was drawn up with this
in mind, and the first production Hart was subsequently modified into a fighter prototype.
This was equipped with a 485hp Rolls Royce Kestrel 2S, the S standing for supercharged, it now had
two forward firing 303. Calibre Vickers machine guns, and it retained the rear firing Lewis gun
for defence. Additionally, the bomb-aiming position was deleted, and the coaming for the
rear cockpit was deepened to increase the field of fire for the rear gun. Similar modifications
were made to a second Hart bomber, and together they went to Martlesham Heath for evaluations.
Known initially as the Hart Fighter, its performance was approximately the same as the
bomber variant. This was because the weight savings of removing the bombing equipment,
and trimming out parts of the rear fuselage, were offset by the additional armament and an
increase in overall ammunition storage. The Hart bomber had a loaded weight of 4,596 lb (2,085 kg),
and the Hart Fighter prototypes had a loaded weight which was just about 100lbs less.
A small initial batch of these fighters were ordered and delivered towards the end of March
1931. These fighters were allocated to no 23 fighter squadron in kenley, becoming the first
two-seat fighters to enter RAF service since the first world war. After a working up period,
they took part in the annual summer exercises where they successfully intercepted the Hart
Bombers – thus proving the concept was sound. The following 12 months was spent making gradual
tweaks and improvements to the design. Some of these were based on the Martlesham assessments,
and others from feedback given by 23 fighter squadron. The biggest complaint came from the rear
gunners, who, in their open cockpits, and thanks to the Harts high-speeds, were subjected to the
icy slipstream coming through the space between the upper wing and fuselage. This was not only
frostbite-inducing, but also made accurate gunnery exceedingly difficult. A couple of things were
tried to fix this. This included experiments with rudimentary hoods to try and deflect some of the
air, as well as a system of flap-like dividers, and while these did sort of work, they limited
the field of fire of the rear gun to such an extent that it might as well have been removed.
This was a problem that persisted as more large scale production got under way, and it was not
until 1934 that a solution was found. This came in the form of a prototype Frazer-Nash,
hydraulically operated turret. The added weight of this turret did shift the centre of gravity
to the rearmost limit of what was deemed safe, but spinning trials at Brookland and
Martlesham heath proved that it did not turn the aircraft into a violently oscillating death-trap,
and from the mid-1930s many were built with this new equipment, or had it retrofitted.
Returning to 1932, full production of the aircraft had been authorised, and it was officially renamed
as the Hawker Demon. The first production Demon flew on the 10th of February 1933, and by April
the first order for 17 units had been completed. In total, 304 Hawker Demons would be built,
and this included approximately 106 built under contract by Boulton-Paul, all of which
came with the Frazer-Nash turret as standard. By 1936 two regular fighter squadrons operated
the Demon, nos 29 and 65 Squadron, as well as Nos. 600, 601, 604, and 607 of the Auxilliary
air force. Additionally, the Demon would see use with the Royal Australian Air Force as well, who
would eventually order 64. These Demons differed a little from their RAF counterparts. They were
powered by re-rated Kestral Vs, which produced 600hp, and they were used as army-cooperation
aircraft and fighter-bombers rather than just as dedicated fighters. Due to a lack of suitable
training aircraft, there being none that compared in terms of speed, the Australian Demons suffered
a high attrition rate in training accidents, and this led to an additional order for 10 Demons with
dual controls and target towing equipment, and these were known as the Demon mk.II.
The Demon’s service life was fairly uneventful, and they were declared fully obsolete by the start
of 1939. They were only intended as a stop-gap fighter, and they performed that role until
more modern equipment became available. They did however see non-combat roles in world war two,
mostly training and target towing. The Demons operated in Australia had a slightly bigger
impact, especially as the RAAF lacked any high-speed training aircraft following the
very austere years of the 1920s, and they became popular trainers in the mid-1930s.
Additionally, when war broke out with Japan, some of these Demons were brought back to
full operational status, owing to the severe shortage of suitable aircraft for the RAAF,
but they would never see frontline service, instead serving in secondary roles.
After the Demon, we have the Hawker Osprey, a navalised version of the Hart bomber. Now
the Hart was never intended for use aboard naval vessels, specifically aircraft carriers, however
a complete lack of suitable alternatives forced the hands of both the Admiralty and Hawker.
Back in 1926, when the specification that led to the Hart was first issued, another,
completely unrelated specification was issued for a naval aircraft. Specification 0.22/26
called for a high-performance fleet spotter and reconnaissance aircraft,
and one which could perform air intercept missions if needed. Though primarily intended for use
aboard aircraft carriers, a successful design was to be sufficiently strong enough to withstand
the forces of catapult launching and rough sea landings as well, and thus it was required to have
the option of a twin-float undercarriage. Unfortunately, for the next two and a half years,
the navy received no satisfactory design tenders. Whether this was due to the RAF’s monopolising of
air ministry funds, and manufacturers resources, or whether there simply were no good designs
submitted, is still somewhat up for debate. But, once the Hawker Hart prototype had proven itself
in its flight trials, the Navy, now becoming a little desperate thought hmmm, we could use
that – and they entered into talks with Hawker to modify the Hart to their own requirements.
This initially began as a private venture, but it soon gained air ministry support as well,
being far cheaper to modify an existing design than to build a new one from scratch, which made
all the bean counters at Whitehall very happy. The Hart prototype, J9052, was thus modified.
The most obvious change was the installation of folding wings, which were hinged at the
first interplane struts; local strengthening of the airframe was completed, to deal with the
aforementioned catapult use; and the undercarriage was modified so that it could be easily swapped
between a wheeled or a float layout. Its unknown when this aircraft,
soon to be renamed Hawker Osprey, first flew, but a small production order was placed towards
the end of 1930, with a new specification – 19/30 – drawn up to match it. The prototype
would go on aboard HMS Eagle, along with other aircraft, and head to Buenos Aires to take part
in the 1931 British Empire Trade exhibition, following which it returned to Brooklands
where it remained in use until being written off in a take-off accident on May 9th 1931.
Production models of the Osprey began to appear in 1932, with the first being allocated to replace
Fairey Flycatchers aboard the carriers HMS Eagle and Courageous, as well as equipping
the 2nd Cruiser Squadron of the Home Fleet. These early Ospreys used the same construction
methods found on the Hart, however the tubular steel structure of the airframe
soon began to suffer from the corrosive effects of saltwater. Rusting carrier aircraft was not ideal,
and experiments were quickly carried out with structures made from stainless steel instead,
and the first of these Ospreys were demonstrated at the 1932 Paris Air Show. The following year,
six of these aircraft were ordered as a sort of pre-production series, and they saw prolonged
service trials with the Fleet Air Arm. 1933 Saw the widespread adaption of the Osprey
within the Royal Navy, and early in the year they began equipping 404, 405, and 409 Flight.
In February, Ospreys of 407 flight became the first fully operational Cruiser units,
serving aboard HMS York, Dorsetshire, and Exeter. 405 Flight, which was then renamed to
no. 803 Squadron that year, then embarked on HMS Eagle and set sail for the far east, serving for
several years before transferring to HMS Hermes. Ospreys built in 1933 were of either the Mark 1 or
2 type, the only major difference being the type designation of the floats that were installed.
Both models were built by Short Brothers, though there were experiments conducted
with floats built by Armstrong Whitworth, including a single float design which had
outrigger supports on the wings, but these were never put into mainline production.
The Osprey Mark 3, announced towards the end of the year, did feature some changes.
It came equipped with a dinghy for air-sea-rescue operations, it had an engine-driven generator,
and it exchanged the old two-blade wooden propeller for a metal Fairey Reed design.
Thus far, all Ospreys were powered by the 630 hp Rolls Royce Kestrel II MS, which allowed
for a decent top speed of 168 mph at 5,000 ft in the landplane configuration. The addition of the
floats dropped this down to around 146 mph. The Mark 4 would be powered by the Kestrel V, which
produced 640hp, unfortunately I couldn’t find any reliable information on what impact that had on
its performance, so we’ll just leave it at that. In total, 146 Ospreys were built, plus an
additional 7 export models which were intended for Sweden and Portugal – 5 going to the former,
2 for the latter. Like the export hart bombers, the Swedish ones were powered
by the Bristol Pegasus radial, and these Swedish Ospreys were used to equip the new
aircraft-carrying cruiser Gottland. A licence was also acquired to produce the aircraft as well,
but few appeared to have been built. That being said, one of these aircraft did survive into the
1950s before being broken up, though again records of its use, like the Harts are sketchy at best.
Though declared obsolete and being withdrawn from frontline service in 1938, the Osprey appears to
have had its combat debut at some point between 1936 and 1937. A single aircraft was ordered by
Spain, re-engined with a Hispano-Suiza V-12. Privately owned and used as a demonstrator,
it was hoped to drive more sales of the type to the Spanish Government. It arrived in Spain just
a few days before the outbreak of the civil war, and it was flown by Republican forces until being
brought down in a forced landing in 1937. Following the Osprey, we now come to the
Hawker Audax, which could be considered the most successful of the Hart sub-variants,
both from the points of total numbers produced, and their general usefulness.
In early 1931, the Air Ministry issued specification 7/31, which called for an
army cooperation aircraft to replace the Armstrong Whitworth Atlas, which had been in service for the
past four years. Unlike the Osprey, which was intended to replace a relatively small number
of aircraft, the Audax was immediately required to upgrade five home squadrons,
plus another two in the middle east, and at least two more which were planned – there also
seemed to be hints of something for India as well, but I couldn’t find enough information
on this so we’ll assume this wasn’t the case. Once again, the Hart bomber, proving to be an
incredibly viceless and versatile airframe, was selected as the ideal candidate to be modified
for this role. An early production Hart was set aside for evaluation in in the summer of 1931,
and in the meantime an initial order for 40 army co-operation Harts was placed by the Air Ministry,
with the type being re-named the Hawker Audax. The first production Audax was flown on the 29th
of December 1931. With a lighter all-up weight of 4,290 lbs, and powered by the 530hp Kestrel 1b,
the Audax was easily identified by its significantly lengthened exhaust manifold. This
was done to prevent the exhaust from obscuring the pilots view when flying near the ground.
This initial batch of forty Audaxes was intended purely for home use. The first of these went
to no.4 Army-cooperation squadron, based at Farnborough, in January and February of 1932
and they were flown at the RAF display later that year. The next squadron to receive the Audax was
no. 13 AC, and between them these two squadrons put in a lot of flying time with the Audax,
with some airframes logging over 1,000 flying hours, which for this type of aircraft at the
time was a considerable amount. Some of these early Audax’s survived into the second world war,
with some still being used up until 1942 as training and liaison aircraft.
More production orders for the Audax quickly followed, with the second batch of 91 aircraft
intended to re-equip two more home squadrons, one in the middle east,
and no.4 Training School in Egypt. Further orders then followed again, including a special order for
a modified version of the Audax for use in India, and in the following year these began replacing
the ageing Westland Wapitis with numbers 20 and 28 Squadron on the northwest frontier.
Like the production of the Hart, the Audax was sub-contracted to several manufacturers to take
the strain off Hawker, who were busy working on the Hart, Fury, Nimrod, and a smattering of
other designs as well. Gloster would build 25 Audax’s under contract, Westland 43,
Bristol 141, and A V Roe produced 287. Including models built by Hawker, Audax production totalled
some 761 airframes before production ceased. Along with RAF use, the Audax also saw some
foreign service as well. As early as March 1933, the government of Iran placed an order
for thirty aircraft, powered by the Pratty & Whitney Hornet S2B. The first of these
radial-powered Audaxes flew on the 22nd of August 1933, and the order was completed in
the following 12 months. Their easy handling and serviceability resulted in a follow up order,
this time for 26 Audaxes powered by the Bristol Pegasus 2, with the final aircraft being shipped
off to Iran on the 7th of April 1935. Another foreign operator of the Audax was Iraq, which
ordered 36 Audaxes, also powered by the Bristol Pegasus, and these were delivered in 1936.
Though reduced to secondary roles by the outbreak of the second world war, some Audaxes did see
action in Africa and the middle east. In the campaigns against the Italians in Eritrea and
Somaliland, during 1940, No.237 Squadron flying Audaxes carried out continual border patrols,
often encountering air units of the Regia Aeronautica. Others, based at RAF Habbaniyah,
took part during the Anglo-Iraqi war of 1941, with some of these Audaxes carrying out ground strike
missions. In general, they carried eight 20 lb bombs, but about a dozen Audaxes were modified
(albeit in secret as command had forbidden it) to carry a single 250 lb bomb instead.
Due to Iraqi shelling of the airfield, these Audaxes were forced to redeploy to the polo field
of the station, and their take-offs were conducted by barrelling down the main driveway of the base,
threading the gap of the main gateway entrance, and
hoping they didn’t hit anything along the way. These Audaxes, bravely flown with a want of care,
were also joined the fourth major sub-variant of the Hart, and that was the Hawker Hardy.
This was essentially a more specialised version of the Audax, specifically intended
for use in the harsh condition of the Middle East. Designed to specification G.23/33,
a production Hart was taken back to Brooklands and progressively modified by the addition of some 200
lbs of equipment, including a tropical survival kit, water containers, a message pickup hook,
and a tropicalised radiator. This experimental prototype first flew on the 7th of September 1934,
and it then went to Martlesham Heath for a series of evaluations and tests.
A production order quickly followed, with the aircraft renamed as the Hardy,
and an initial batch of 47 Hardys were built in the latter quarter of 1934. The first of
these aircraft were shipped out to Iraq, where they joined no 30 Squadron at Mosul. A second
order of 16 Hardys was then placed, with these being sent out to No 6 Squadron in Palestine,
these aircraft differed from the first in being powered by the Kestrel 10 engine.
Between 1935 and 1938, the majority of the RAF’s aerial policing of these regions was done by the
Audax and Hardys, totalling six squadrons deployed from India’s north-west frontier, through Iraq,
Palestine, and Egypt. Understandably, operating in these remote, often very
harsh conditions took its toll, and a final order for ten replacement Hardys was placed at
some point between 1935 and late 1936, the exact details of which seem to be impossible to find.
Built in far smaller numbers, the Hardys didn’t see as much action as the Audax, but collectively
both of these aircraft put in a surprising amount of work during the first two years
of the second world war. This was mostly done in the face of vastly superior Italian opposition,
and the Hawkers often found themselves going up against Fiat Cr.32. Though the Audax gradually
faded away from use, as it was replaced by more modern designs, the Hardy literally died in
battle. With the exception of maybe two airframes, which were struck off charge (supposedly), every
operational Hardy was destroyed by enemy action in one form or another, and one unit was completely
wiped out on the ground in a single day. But, despite the Hardys poor fate, the Audax,
Demon, and Osprey, fared considerably better, and although not many survive today,
indeed no versions of the Audax or Osprey exist anymore, they represent a very important part
of the history of the RAF. Though outdated by the outbreak of war, they were responsible for
training almost an entire generation of pilots and crew, some of whom went on to serve in the
war in more modern aircraft, or, they went on to train newer pilots and crews who would
themselves go on to serve instead. Combined, the Hart, Demon, Audax, Osprey, and Hardy could be
considered the most important British biplanes ever produced after the first world war, merely
due to how much they contributed to training and expanding the RAF in the middle of the 1930s.
As always, thank you all so much for watching, and a big thank you of course to the patreons.
Provided I got my workload sorted this video should be going up on a Wednesday and not a
weekend, and in the coming weeks we’ll be on a schedule of just one video per week until
I return after the 17th of July…though I am thinking of uploading a few sort of min-videos
as well. We’ll see. A big thank you of course to the wing commander tier patrons,
our highest tier supporters, and the latest officer-tier patreon Q&A is now live,
so feel free to ask your questions there. But, as always thank you all
so much for your continued support, and I’ll catch you all next time. Goodbye.