Continuing
our adventure of looking at questionable designs built to questionable air ministry
specifications, we come to the Boulton-Paul P.32. Recently, we looked at the De Havilland DH.72,
a three-engine bomber designed in the late 1920s, one that was plagued with problems
and eventually got nowhere, but at least the De Havilland wasn’t a literal threat
to the life and limbs of its pilots. Just to recap on the situation, In 1927,
the Air Ministry issued specification B.22/27, which called for a three-engine, long-range,
heavy bomber capable of night-time operations. It was to be metal framed, have four crew members,
and the nose was to be left free for a gunner/bomb aimer. Two prototypes would
eventually be built to this requirement. Sometimes, when two designers set out to
solve the same problem they arrive at very different solutions, but often they produce
remarkably similar products, as was the case with de Havilland and Boulton Paul. Though the broad
layouts were the same, the unique ancestry of the two designs could still be seen. De
Havilland used their Dh.66 as the base template for their design, and Boulton-Paul drew heavily
on their Sidestrand bomber, itself a highly popular design with the RAF. The all-metal
construction was largely similar to that of the Sidestrand, and the fuselage and square
cut of the P.32s wings were clear descendants of the company’s previous twin-engine designs.
As mentioned in the video on the de havilland, the initial specification presented near-impossible
challenges due to the central mounting of the third engine. This eventually forced
concessions in the design requirements to be made, which caused delays. Further delays were
then encountered with both manufacturers, De Havilland was inexperienced with metalwork, and
Boulton-Paul just seemed to be unlucky as the Air Ministry kept imposing revisions on their design
specifically. Whether this was because somebody highly placed preferred de Havilland, or whether
Boulton Paul’s initial design was simply not good is impossible to tell. Either way, the P.32
was not ready until almost three years later. The construction of the sole P.32 was an epic tale
of delay, government meddling, and questionable safety tolerances. Or, in other words, a typical
Tuesday in the interwar aviation industry of Great Britain. As built, the P.32 was either
a five or a six seat aircraft – the optional sixth seat was to allow a pilot-instructor to
come along for training purposes should the bomber be placed into mainline production.
The fuselage resembled that of a scaled-up Sidestrand, both in construction and appearance,
though the tail differed in shape. It had a wingspan of 100 ft (30.4 meters),
a gross weight of 22,700 lbs (10,300 kg), and it was the largest and most complex aircraft Boulton
Paul had yet built. It was also equipped with -for the time at least- modern equipment. It came with
a full radio suite, a toilet for the crew (though admittedly this was just a glorified tube out the
side), and the control surfaces for both the wings and the tail came with full servo tabs.
The pilot’s cockpit was originally placed ahead of the wings on the starboard side, but the first
of the many design modifications was to move it to port, with the second pilot’s position just behind
it. The nose gunner also acted as bomb-aimer and navigator. He was equipped with a single lewis
gun on a Scarff ring, and had a swivel seat – this allowed him to operate the Mk VI course
setting bombsight when facing forward, and to use the chart table and navigation instruments when
facing aft. There was a hatch in the floor of his compartment for a parachute exite,
and a door at the back of this compartment led to a walkway that ran alongside the pilot’s cockpits
and further aft to the other compartments. A door at the rear of this walkway led into the
wireless and camera compartment, which, funnily enough, came with a wireless radio set and either
a P.7 or P.8 observation camera. From the rear of this compartment, the walkway continued,
going past the main fuel tanks which were accompanied by three header tanks, and then
it terminated at the rear gunner’s station. Originally, the P.32 was designed with both
dorsal and ventral gunners, to provide optimal protection, but another of the Ministry’s
requested changes included the deletion of the ventral position in favour of a general tail
gunner station. As in the Sidestrand, this meant the tail gunner had to also manage the dorsal gun
as well, which meant that if the P.32 was attacked from multiple approaches at the rear…its defensive
capabilities were exceedingly compromised. Because of this, a request was granted
to have a parachute installed at each position, so that the poor, harassed,
rear gunner didn’t have to run from one spot to the other to bail out in an emergency.
Now, while the various changes requested by the Air Ministry thus far had delayed construction
by nearly six months, the biggest delay came from troubles in sourcing adequate engines.
Boulton-Paul had fought tooth-and-nail to use their preferred powerplant, the Bristol Mercury V,
with provision to upgrade to the new Pegasus engine should it become available.
This had been the cause of some consternation, as the Air Ministry had a preference for the cheaper
Jupiter engine, and when it became clear that no Bristol Mercuries could be spared,
the Jupiter engine was forced upon the Boulton Paul design team with particular enthusiasm.
Unfortunately, it presented a little bit of a design challenge, specifically when it came to
the central engine, and the three-blade propellers used by all three. Firstly, servicing the central
engine was such a challenge that they had to literally build a new type of expensive engine
hoist to facilitate this, and secondly…there was only nine inches of clearance between the tips of
the propellers and the second pilot’s head. Potential pilot decapitation or dismemberment
was something of a safety concern, and honestly the proposed solutions made them realise that
the second pilot’s position might as well just be deleted. Solution one was to install some
sort of guard, which probably would have done something to help, but also wouldn’t prevent
violent bodily harm in the event of an engine mount failure, or the pilot somehow forgetting
about the spinning blade of death behind him and gesturing to the ground crew…only to lose a hand
in the process. Solution two was to move the seat further forward, which increased clearance to a
calm and reassuring fourteen inches, but made operating the rudder impossible. Additionally,
neither solution addressed the other problem, which was that it was impossible for the pilots
to talk to each other, owing to the deafening roar of the propellers being so close to
their heads in the first place. Adding insult to potential injury,
the Air Ministry then made 41 further modification requests at their final
conference with Boulton Paul in November of 1930, when the prototype was almost finished.
The Jupiter XF engines were then changed to the 575hp supercharged Jupiter XFBM, but delivery
and fitting delays then pushed back the planned delivery date even further to March 1st 1931.
Then, problems in ground testing pushed the delay back even further to July,
and then even more problems (including a dramatic port engine failure) pushed things back once
again. In the end, the prototype did not make its maiden flight until October the 23rd, 1931,
over a year behind schedule. Flight trials were then marred by more problems,
this time with the port engine that had replaced the last one which had all but exploded a few
months previously. As it turned out a problem with the reduction gears had been the culprit,
and a new reduction gear unit was not received until mid-November. The P.32 was then finally
taken to Martlesham heath, where it could be compared to the De Havilland DH.72,
which had also encountered its own problems. In the end, like the De Havilland, it was all a
waste of time and money, as the Air Ministry had lost interest in the heavy bomber project.
Additionally, all of the Ministry’s required changes had ballooned the cost of the Boulton
Paul design by over 20%, which would have put it at an immediate financial
disadvantage against the De Havilland design. The P.32 would still be publicly displayed at
RAF Hendon that year in 1932, and it was around at least for another
eighteen months before being broken up at Martlesham at some point in the mid-decade.
It is deeply ironic that the British Manufacturers with almost zero experience in heavy bombers
tendered designs for this specification, whereas the heavy bomber experts (Vickers
and Handley Page) had produced prototypes for the slightly less ambitious twin-engine specification,
but had avoided this one like the plague. Boulton-Paul and de Havilland tried their best,
of course, but these two projects were almost doomed to fail from the start
thanks to the conflicting requirements of the original specifications.