In today’s video we’ll be taking a look at a very interesting aircraft, coming out
of Germanys rich tradition for building seaplanes and flying boats.
Out of the many designs fielded by the Luftwaffe during the Second World War, the Blohm and
Voss BV 138 is perhaps one of the more underrepresented aircraft of its day, despite its striking
design and varied service life.
The first stages of its development would take place in the mid-1930s, in the hands
of Hamburger Flugzeugbau, or Hamburg aircraft construction (a subsidiary of Blohm & Voss).
A need had arisen for a new long-range patrol aircraft, one that should also double as a
transport if required.
Under the direction of Chief Engineer Richard Vogt, plans were initially drawn up for two
potential designs.
One would be powered by a pair of 1000hp BMW 15 engines, and the other by a trio of 650hp
Jumo 205s.
Both of these engines ran on diesel, an unusual feature of aero engines at the time, and this
was to both give the aircraft high efficiency and range, and also to allow it to be refuelled
by U-Boats at sea, thus greatly expanding its operational range.
The proposed aircraft was to be of all-metal construction, with a short central hull and
high-mounted cantilever gull wings.
The control surfaces were also to be skinned with metal, the only fabric covering being
located on some sections of the underside of both wings.
Twin booms connected to the tail assembly, consisting of twin vertical stabilisers and
a single elevator, and the aircraft would be balanced on the water by two non-retractable
pontoons.
Development problems with the BMW 15 engine led to the experimental Jumo 206 being selected
as the main powerplant instead, with the lower-power 205 being held as a backup.
The 206 was expected to give 60% more power than the 205, but at the eleventh hour, after
construction of the prototype 138 had already progressed to an advanced stage, everyone
was told this engine, too, was not available.
Because of this, the 138 V1 prototype, which began construction in early 1936, did not
complete its maiden flight until July 15th 1937, after a hasty conversion to fit three
Jumo engines on an airframe designed for two.
The second prototype, V2, took to the air in November of the same year – designed
with three engines from the outset - but it was quickly discovered that both prototypes
suffered from instability both on the water and in the air.
After further testing it was discovered that the necessary changes to improve handling
could not be made with the current layout of the aircraft – and as a result the prototype
underwent a serious redesign to accommodate a number of improvements.
The aircraft would have an extended hull, larger tail surfaces and stronger, reinforced
tail booms in an attempt to overcome the various stability problems.
Five of these improved prototypes, designated the BV 138A (now sporting the name of its
parent company), would undergo flight testing in early 1939 as a pre-production series.
Unfortunately, it was found that the aircraft still retained a multitude of unfavourable
characteristics, predominantly rooted in structural issues, leading to various cases of failure,
and further changes were thus required.
The fourth pre-production aircraft, BV 138A-04, was returned to the Blohm & Voss facility.
Here it underwent reinforcement to increase the strength of its airframe - leaving the
factory as the first of the strengthened 138B series.
But during this time, 25 BV 138 A-1s had been produced due to an urgent need for coastal
transports - these aircraft would enter service with the 108 Special Purpose Bomber Squadron,
and subsequently take part in the Norwegian campaign.
Some of these would be pressed into duty as troop transports (in this role it could accommodate
ten fully loaded troops in its hull).
For defence in this theatre, the BV 138 A-1 would have a 20 mm MG 151/20 cannon in a forward-facing
turret and a single 7.92mm MG 15 in the rear engine nacelle.
Though mostly used in Norway, a number would also be sent to the Bay of Biscay with Coastal
Group 506 and 906.
These aircraft would not be hugely effective or popular with crews, partly due to the structural
issues (which led to prayers for salvation every time they had to land in anything but
a flat calm), partly due to questionable engine performance, and partly because it was under
gunned.
December 1940 saw the flight trials of the BV 138B-1, which was a marked improvement
over its predecessor.
Not only did it not fall apart as easily as the A series, but This variant also added
a significantly upgraded, and formidable defensive armament of an additional bow 20mm cannon
in the LB 204 hydraulic traversable turret, along with a single 13mm MG 131 operated by
a gunner in the central engine nacelle (replacing the previous MG 15).
The weight increase in this model was offset by mounting the more capable Jumo 205D engine,
which produced an uprated 868 hp under takeoff power.
The B variant was the main conversion type for mine-sweeping duty.
This involved removing all armament to save weight and fitting a large circular coil around
the aircraft; an electric current would be run through the coil, and it would fly low
over target areas and magnetically detonate sea mines – much like the modified Vickers
Wellingtons we had covered in an earlier video.
Though it’s heavy guns had been removed, the mine-sweeping variant would end up carrying
over a ton of specialised extra equipment for this role.
The performance impact from this added bulk did not make it a particularly popular modification,
and only a small number of Bv 138s were modified for the minesweeping role.
The BV 138C-1 - which began to be delivered to operational units in March 1941 - was the
ultimate and most-produced version of the aircraft.
it was easily identified by the four-bladed central propellor, whilst the two wing-mounted
engines retained the old three-bladed model.
The 138 C-1 was 19.85 metres long, and had a wingspan and height of 26.94 and 5.9 metres
respectively, making it actually a fairly large aircraft - almost as long as an Avro
Lancaster!
The empty weight was 11,770 kg, and 14,500 kg loaded - though it could takeoff weighing
as much as 17,650 kg.
With a maximum endurance of around 20 hours - and a range of 2,400 km - the aircraft was
well suited to long range coastal reconnaissance missions.
With a maximum speed of 285 km/h at sea level the 138 was not a fast aircraft, but it was
more than adequate for its intended role.
Unloaded it could reach altitudes as high as 5,000 meters, but with a standard load
the operational ceiling was lower, at around 2,800 meters.
The 138 was generally operated by a crew of six men - with slight discrepancies depending
on the variant.
This would include a pilot, navigator, radio operator, nose-gunner, rear-gunner, and upper
nacelle gunner.
An optional field modification sometimes employed by crews in the C-1 was to fit a single 7.92mm
MG 15 in the starboard hatch opening, to provide extra defensive fire to the right of the aircraft
- the gun would be manned by the radio-operator.
Standard issue 138s were fitted with a bomb rack on the port inboard wing capable of holding
up to 150 kg of bombs or depth charges; Some C-1s would also be fitted with search radar
for anti-shipping duties.
Its payload, along with the improved defensive armament, made the BV 138 surprisingly effective
at stalking allied convoys.
In one sortie, a BV 138 successfully shadowed a British convoy for 1.5 hours, swatting away
several fighter attacks and making it back to base - damaged but serviceable.
Post-production modofications were very common for the 138.
Including the ones already mentioned, Of the 227 C-1s produced, around 70 were fitted with
the necessary equipment for making catapult-assisted take-offs for use on ships, increasing their
range of utility vastly.
164 of the total produced were also fitted with extra bomb racks, effectively doubling
the payload - aircraft with this upgrade were designated C-1/U-1.
Despite its protracted and shaky development process, the BV 138 wound up having a very
successful career in its intended role, being produced from 1938 to 1943 - with a total
production run of 279 aircraft, the vast majority of which were C-1s.
On the whole it was well liked.
It would serve its crews faithfully, flying over a very large geographic area - with BV
138 equipped Staffels ranging from Norway to the Mediterranean.
It was often operated alongside its smaller, more famous counterpart - the Arado Ar 196.
One quadron, equipped with ten 138 B-1s would log a total of 500 flight hours in October
1941 - which equates to a staggering 100,000 kms of reconnaissance patrol, a testament
to the aircraft’s reliability.
The many structural reinforcements that the 138 had undergone during its development phase
had also resulted in the aircraft being extremely tough, solidly built and robust - which the
138 would garner a very quick and well loved reputation for.
It also got a reputation for its looks, earning the effectionate nickname of the Flying Clog.
Now that name might not sound too threatening, mind you I would be scared if somebody threw
a clog at me, but the 138, on two separate occasions, took on and shot down both an RAF
Blenheim and a PBY Catalina, the latter being one of the few occasions when flying boats
engaged in aerial warfare.
Against fighters however, it was of course vulnerable – and as the war progressed the
138 was pressed into some particularly risky missions.
In one of its most famous operational uses, on the 1st of May 1945, a BV 138 C-1 from
the 130th Naval Air Group would land at Lake Berlin under a barrage of anti-aircraft fire
for a special mission - to retrieve the last testament and will of Adolf Hitler.
The mission did go as planned.
The couriers carrying said Will could not produce identification papers, and the pilot,
not choosing to linger in Berlin whilst they wrangled the matter, decided to evacuate 10
wounded personnel instead, taking them north to Copenhagen.
During its development, a number of rather strange off-shoot versions of the 138 were
explored - such as the BV P.111 - which was an asymmetrical derivative design that envisioned
a single boom, gondola style flying boat.
This was exactly the kind of imaginative design that Blohm & Voss gained a reputation for,
though none of these offshoots really amounted to anything other than drawings and blueprints.
After the war many of these plans fell into the hands of the British, who all collectively
whistled and wondered what exactly Heer Vogt took with his morning coffee.
But they were almost unanimously impressed by the daring attempts of BV to push for the
most inventive designs possible.
Unfortunately, no complete examples of the BV 138 survive to this day, though the badly
rusted hull of one 138 C-1 was salvaged in Copenhagen, and now is on display at the National
Museum of Science and Technology in Denmark.
There are further submerged wrecks that have been discovered mainly around Norway and Greater
Scandinavia, but none of these have been salvaged, and are likely to remain where they lay.
As always, thank you all so much for watching, and a big thank you of course to the Patreons.
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Thank you all for your continued support, and I’ll catch you all next time.
Goodbye.