Today, we’re taking a look at one of the first truly mass produced British military
aircraft, becoming the backbone of RAF’s expansion program in the mid-1930s, and this
was the Hawker Hart.
The hart was the outcome of specification 12/26, issued in May 1926.
It called for the production of a daytime bomber that had a maximum speed in excess
of 160mph (257 kmh), a requirement which, at the time, most manufacturers felt was impossible
with the current aero engines available.
This specification also came about during a time of heightened apathy within the British
aircraft industry, time and again, manufacturers had submitted proposals, good, promising proposals,
only to never make it past prototyping phase.
This was due to the conservative fiscal policy in the lean years following the First World
War, which meant that new, innovative designs were often sidelined due to cost, especially
airframes that made use of metal structures.
It also meant that manufacturers were having to rely on older, outdated engines, hence
why many believed the new specification to be an impossibility.
However, investigations were being made into using the Rolls Royce Falcon F.1 Supercharged
inline engine, and because of this Avro, Hawker, and later Fairey submitted proposals.
The Hawker design team, led by Sydney Camm, commenced work on the project in collaboration
with Rolls Royce, who also offered assistance to the others, and by December 1926 their
initial tender was ready for submission.
The proposed design used the now-familiar Hawker steel tube primary structure, single-bay
wings, and a split axel undercarriage with pneumatic shock absorbers.
The submission was quickly accepted and a mock-up was produced early in 1927.
In this design Sydney Camm introduced a new form of wing spar, consisting of top and bottom
rolled steel strip booms connected by a light-gauge plate web.
This spar gave maximum strength for minimum weight since the materials were functioning
near their permissible stress at full factored load.
Putting that aside, During 1927 the design of the aircraft was modified several times.
First, the heavy I-struts were replaced by much lighter and stronger N-struts, then a
cross-axel undercarriage with Vickers oleo-pneumatic shock absorbers was added, a pump operated
fuel system replaced the gravity fed system, and, most importantly, the Rolls Royce F.XIB
engine was adopted instead.
This engine differed fundamentally from the original Falcon, having the cylinder blocks
cast in one instead of individual cylinder castings.
This improvements improved its strength, and reduced the engine weight by something around
60 pounds.
As construction on the prototype proper began, the design sat as such.
It was a single-bay biplane powered by a Rolls-Royce F.XI water-cooled V12 engine (the engine that
later became known as the Rolls-Royce Kestrel).
It had, as the specification required, a metal structure, with a fuselage structure of steel-tube
covered by aluminium panels and fabric, with the wings having steel spars and duralumin
ribs, covered in fabric.
The crew of two sat in individual tandem cockpits, with the pilot sitting under the wing trailing
edge, and operating a single .303 in (7.7 mm) Vickers machine gun mounted on the port
side of the cockpit.
The observer sat behind the pilot, and was armed with a single Lewis gun on a ring mount,
while for bomb-aiming, he lay prone under the pilot's seat.
In terms of ordnance, Up to 520 pounds (240 kg) of bombs could be carried under the aircraft's
wings.
Construction began at some point in mid-1927(ish), and the prototype was ready for its first
flight in the summer of 1928.
It was first flown by Flt Lft P. “George” Bulman in June.
It then went on to complete a series of flight trials over a period of six months, before
the existence of the Hawker Hart was announced and it made its first public appearance at
the Olympia Aero Show.
Detailed service evaluation of the Hart began before the end of 1928, with the prototype
visiting Martlesham Heath for no less than eight separate trials in a six month period.
It demonstrated good performance and handling, reaching 176 mph (283 km/h) in level flight
and a blistering 282 miles per hour (454 km/h) in a vertical dive.
These trials were held in direct competition with those being completed with the Avro Antelope
and the Fairey Fox Mk II.
At the completion of the trials the Hart was deemed to be the best of the batch, being
superior in speed, handling, and ease of maintenance.
Thus an initial production order for 15 aircraft was placed to a new specification, 9/29.
These could be considered pre-production Harts, as it was felt that such a leap in aircraft
performance would produce some teething problems, both from the points of crew training, and
serviceability.
No.33 bomber squadron, based at Eastchurch, received 12 of these early Harts in January
of 1930, which replaced their existing Hawker Horsleys.
Very quickly the Hart showed to be a big improvement, and before the Squadron had even worked up
they placed second in the annual Bomber Command operational contests.
Overnight it had become the most capable bomber in service.
In fact, it had become the most capable aircraft fielded by the RAF, full stop.
No single fighter in service, or about to enter service, could catch it, and the venerable
Bristol Bulldog, the main fighter at the time, was ten mph slower.
Because of this startling performance, one of the first Harts was sent across to India
for evaluation to replace the ageing fighters currently stationed there: specifically the
Bristol Fighter, and the Armstrong Whitworth Siskin.
This Hart, flown by Fred Raynham, performed well.
However during one of the flights, a local Kite, as in the bird of prey, took exception
to the fabric-clad, loud, noisy thing entering its territory and began a series of swooping
attacks.
In the aerial equivalent of David vs Goliath, the Kite actually inflicted enough damage
to bring this Hart down, and it was written off.
Fred Raynham survived the ordeal, though I imagine he was a little embarrassed.
Bird-related beatdowns aside, the Hart proved well suited to the environment, and an initial
order was placed for 57 versions of the Hart India.
This was a tropicalised version of the design, intended to cope better with the hotter, more
humid climates to be found, and the first of these was flown on September the 7th 1931.
Meanwhile, further orders were being placed for the Hart for Home Service, and indeed
the Hart would form a core elements of the RAF’s mid-1930s expansion plan.
A total of 82 were ordered between 1930-31, equipping 12, 18, and 57 Bomber Squadrons,
but more soon followed.
This quickly put a strain on the Hawker production line, as work was also now in progress on
the Hawker Fury, Horsley, and Tomtit, and Hart production was sub-contracted to other
manufacturers.
The scale of Hart production was a big achievement for the time, when most aircraft were built
at maybe 100 or perhaps 200 examples if they were very successful.
Westland built 43 Harts under contract, Boulton Paul built 106, Bristol 141, Gloster 144,
Vickers built 226, Avro managed 244, and Armstrong Whitworth produced a deeply impressive 456
– which represented a massive commitment from such a firm.
In addition to this, Hawker itself produced approximately 1,438 Harts across the different
variants.
At one time, in 1934, seven out of every eight aircraft delivered to the RAF were of Hawker
origin, while in 1936 -at the height of the expansion plan- three out of four new squadrons
being formed were being equipped with the Hawker Hart or one of its sub-variants.
The impending, widespread acceptance of the Hart presented two problems.
Firstly, it outclassed everything in the RAF inventory, which meant they needed a new fighter.
And secondly…it outclassed everything in the RAF inventory, and thus any current training
aircraft weren’t good enough to prepare pilots for the raw, untamed fury of this new
and fantastic machine.
And so, this led to the development of two things: the Hawker Fury, which we’ll cover
in another video, and a training version of the Hawker hart.
This was in fact a converted version of the Hawker Audax, which itself was another variant
of the Hart which had been designed for Army Co-operation duties.
Following evaluations of a prototype, and two other hastily converted models.
The two-seat, dual control trainer was placed into service.
Testing had revealed issues with the centre of gravity effecting the handling, it having
shifted due to the removal of military equipment, and Hart trainers had a reduced sweep-back
on their upper wings.
On production Harts it was 5 degrees, but on the trainers it was just 2 1/2.
And this mostly solved the problem and their handling was considered almost identical.
In a short period of time, Hart Trainers formed the main equipment of the advanced training
wing at the Royal Air Force College at Cranwell, where they replaced the Armstrong Whitworth
Atlas trainers.
Hart trainers also went to frontline squadrons for training in navigation, communication
and instrument flying.
At the height of the expansion program, every Home flying school would fly Harts, and its
contribution in training the light bomber crews of the RAF cannot be overstated.
In front-line service, the Hart served with numerous squadrons.
It operated with numbers 6, 11, 12, 15, 18, 33, 39, 57, 60 and 142 bomber squadrons.
Number 24 communications squadron.
And numbers 600, 601, 605, and 610 squadrons of the Auxiliary air force.
Though produced in massive numbers, for the time, the Harts didn’t see a great deal
of exciting service -or action- during the interwar period.
They were, however, produced in a great variety of variants and a few export models were produced
as well.
The off-shoot versions of the Hart were the Audax, the aforementioned army cooperating
aircraft.
The Demon, a fighter variant of the hart.
The Hardy, an appropriately named general purpose and tropicalised version of the Hart.
And the Osprey, which was a carrier-borne version.
I’m not going to discuss them now, as I plan to cover them in a follow up video, which
will come out in the next week.
Export models of the Hart did not amount to too much, this was because Hawker was still
a private company until 1933, and it just didn’t have the capacity to produce large
quantities of aircraft for overseas customers while tending to the massive requirements
of the RAF.
There were, however, a few exceptions.
In 1932, the Estonian government ordered eight Hart bombers which were delivered in the Autumn
of that year.
They came with interchangeable wheel and float undercarriages – a design feature inherited
from the Osprey.
Not much is known about their service, but they were still listed as operational when
the they became involved during the Second World War.
Harts operated by Sweden had a far more active life than most that were in British service.
In 1934, Sweden ordered four pattern aircraft for evaluation, which were unique in being
powered by the 580HP Bristol Pegasus radial engine, instead of the rolls royce inline.
Following successful testing, Sweden purchased a licence to produce the aircraft, and at
least 42 were built.
When Russia invaded Finland in 1939, Swedish Harts formed part of the volunteer unit sent
to assist their Finnish neighbour.
By January 1940, at least four Harts were in action alongside other aircraft, including
Gloster Gladiators, and they were usually equipped with ski undercarriages due to the
frozen conditions.
In all, about nine Harts took part in the Finnish campaign, carrying out reconnaissance
patrols, bombing attacks on infantry columns, and other various strike missions.
One of these Swedish Harts still survives today, and can be found at the Swedish Air
Force Museum.
Another role the Hart found itself heavily involved in was that of a testbed.
With wide flying limits, good control at low speeds, and accommodation for a flight observer,
Rolls-Royce purchased several ex-contract aircraft for engine testing.
One Hart was used to test the Bristol Jupiter and Pegasus engines, until it came to a sudden
and watery end in the English Channel, it having run into problems on the way back from
the 1932 Paris Air show.
Another Hart was used during the early development of the troubled Rolls-Royce Goshawk, a steam-cooled
engine that I’ve mentioned in a few videos, as it was imposed upon several manufacturers
when the Air Ministry became a bit obsessed with it.
This Hart used special strip condensers on the leading edge of the upper wing.
This led to the installation of a canopy, as the pilots took extreme exception to their
face being spattered by supercooled droplets of water, which was apparently quite painful,
and this led to canopies being fitted to, and tested with, several other Harts as well.
The two most notable Harts were registered G-ABMR, and K3036.
The latter was a vital testbed for the Rolls-Royce P.V.12, which went on to become the famous
Merlin engine.
A significant amount of testing was done with this hart, and it performed a large amount
of the early flight development that contributed to the Merlin’s success.
The other Hart, G-ABMR, had one of the longest flying careers for this type of aircraft.
Despite being the 13th Hart built, it was not unlucky at all.
Apart from having flown with almost every type of Kestrel engine between 1930 and 1939,
it was used during World War 2 both as a photographic aircraft and as a pilot ferry.
It was also used as a demonstrator, and after the war it performed a variety of civilian
roles, as well as being used for air races.
It was still flying in the 1970s, when it was transferred to the RAF Museum.
There it can still be found, painted in a striking silver and yellow livery, and it
isn’t the only survivor either.
There is the Swedish Hart, of course, and there is also a Hart trainer on display, as
well as a couple of the Hawker Demons – one belongs to the Shuttleworth collection in
Britain, and the other can be found at the Royal Australian Air Force Museum in Point
Cook.
As always, thank you all so much for watching, and a big thank you of course to the Patreon
supporters, who’s names you’ll see here.
I’m currently working on a small backlog of videos to cover me during my overseas travels,
so that’s why things have been a bit quiet on here, but there shouldn’t be too much
of a gap in content moving forward.
A big thank you of course to our wing commander tier patrons, our highest tier members, and
a big thank you to a couple of those commanders who upgraded their pledges by a considerable
amount, you know who you are, and thank you both very, very much.
The support I get from everyone, regular viewers and patreon supporters, is absolutely heartwarming,
but I will say that I will catch you all next time, goodbye.