As the war in Europe slowly progressed,
the Luftwaffe found itself in a desperate struggle to fend
off ever-increasing Allied bombing raids. These desperate times demanded a desperate
solution, which came in the form of many experimental aircraft and other technological
proposals. Some of these included developing ramjets engines that could be powered using
alternative fuels, and aircraft designs that could potentially reach supersonic speed. The
man who tried to combine them into a single design was Alexander Martin Lippisch and
his bizarre-looking P 13a flying triangle. In the later stages of the war, chronic fuel
shortages caused major issues for the Luftwaffe in opposing the Allies. As one solution to
overcome this rising problem, it was proposed to speed up the development of the ramjet
engines. They were designed to use compressed air mixed with fuel to create thrust but without a
mechanical compressor. In contrast to jet engines, ramjet engines were much simpler to build in
theory and could be adapted to use other types of fuel beyond aviation gasoline. The downside
was that it could not function during take-off, as it required a high volume of airflow to
function. Thus, an auxiliary power plant was needed. The first working prototype was built
and tested in 1942, mounting the engine on a Dornier Do 17 and, later, a Do 217.
While the ramjet was being developed, the Germans needed a suitable aircraft for it
to be equipped with. This is where tailless delta wing designs enthusiast and engineer
Alexander Martin Lippisch came into play. He made a breakthrough with the construction of
a rocket-powered glider known as the DFS 194, and after some time spent refining this design,
it eventually led to the development of the Me 163 rocket-powered interceptor. In 1942, Lippisch left
Messerschmitt. Instead, he joined the Aeronautic Research Institute in Vienna, where he continued
working on his delta-wing aircraft designs. In May of 1943, he became director of this institution,
and at that time, work on a supersonic aircraft was initiated. In October 1943, Lippisch won
a contract to develop the experimental P 11 delta-wing aircraft. Lippisch became interested
in merging his new work with a ramjet engine, leading to the P 12. In the early stages of the
project, Lippisch and his team were not completely sure what to use as fuel for their aircraft.
The whole project had a major setback when the facilities where he and his team worked were
bombed by the Allies. In addition to the damage to the project itself, over 45 team members died
during this raid. To further complicate matters, the scarcity of gasoline meant that Lippisch's
team was forced to seek other available resources, such as different forms of coal. This led to the
creation of the slightly modified project named P 13. In contrast to the P 12, the cockpit was
relocated from the fuselage into a large fin. This design provided better stability while also
increasing the aircraft's aerodynamic properties. The P 12 and P 13 small-scale models were
successfully tested at Spitzerberg Airfield near Vienna in May of 1944. The project even received
a green light from the Ministry of Armaments. In the early stages of the project, there were
some concerns that the radical new design would require the extensive retraining of pilots.
However, the wind tunnel test showed that the design was aerodynamically feasible and that the
aircraft had no major control issues. Based on these tests, work on an experimental aircraft
was ordered to begin as soon as possible. As the work on the P 13 went on, the name
was slightly changed. This was necessary as different variations were proposed. The original P
13 received the prefix ‘a’, while the designations of later variants continued alphabetically.
After a brief period of examination, the P 12 project was discarded in favor of P 13a.
The P 13a did not have a traditional fuselage, but rather a base consisting of a delta wing.
A large fin with a pilot cockpit was placed on top of it. The exact ram engine type was never
specified, but it was positioned in the central fuselage, with the air intake to the front and
the exhaust to the back. The total fuel load was to be around 800 kg (1,760 lbs). Combustion
was to be initiated by using small quintiles of liquid fuel or gas flames. The overall engine
design was changed several times during the work on the P 13 without any real solution to
the issues of output consistency. Given that the ramjets could not work without air thrust, an
auxiliary engine had to be used during take-off, though a more practical scenario would have been
to tow the P 13 until it could start its engine. The wing construction was quite robust and
provided with deflectors that would prevent any potential damage to the rudders. The wing
design also incorporated a sharp metal plate, similar to those used for cutting enemy balloon
cables. A plausible reason for this choice was the fact that, given it had no landing gear, the
aircraft design had to be robust enough so as not to be torn apart during landing. The wings
were swept back at an angle of 60 degrees. The fin had to be enlarged to provide good
flight command characteristics. The fin cockpit was provided with a large glazed canopy that
offered a good view of the front and sides. While this is often how the P 13a was portrayed,
Lippisch never fully decided whether he should use this version or the second version that used
a smaller fin with the pilot cockpit placed above the engine intake. These are drastically different
from each other. Lippisch, for unknown reasons, presented the version that used the smaller fin
to British intelligence officers and the large fin version to the Americans after the war.
Landing was a bit unusual. To save weight, no standard landing gear was to be used. Instead,
a small dolly would be used to move the aircraft. Once sufficient height was reached, the
dolly was to be jettisoned. In theory, this was an easy process, but in practice, this
operation offered a good chance of failure and was much less safe than a conventional landing gear.
The aircraft would land with the nose raised from the ground and then use a landing blade skid. To
help absorb the landing impact, additional torsion springs were to be used. This contraption
had to be activated before the landing, emerging from beneath the aircraft fuselage,
with the rotation point located at the front. Once released, it was to guide the aircraft toward
the ground, with the torsion springs softening the landing. This whole contraption seems like
a disaster just waiting to happen and it's questionable how practical it would have been.
The main issue with the P13 project was finding the most suitable fuel. A great deal of
time was spent testing and evaluating the most suitable forms of coal that could be used
as fuel. Initial laboratory test runs were made using solid brown Bohemian coal in combination
with oxygen to increase the burn rate. The fuel coal was tube-shaped, with an estimated weight
of 1 kg, and encased in a mesh container through which the granulated coal could be ejected.
The testing showed serious problems with this concept. While a fuel tube could provide thrust
that on average lasted 4 to 5 minutes, its output was unpredictable. During the testing, it was
noted that, due to the mineral inconsistency of the coal fuel, it was impossible to
achieve even burning. Additionally, larger pieces of the coal fuel would be torn off
and ejected into the jet stream. The final results of these tests are unknown but seem to have
led nowhere, with the concept being abandoned. While working on the P 12 and P 13, Lippisch
was approached by a group of students from the Darmstadt and Munich universities, who were
interested in being involved in his projects. Lippisch agreed to this and dispatched one of his
assistants. This group moved to a small warehouse and began working on the DM 1 wooden glider. It
did not have a traditional fuselage, but instead, its base consisted of a delta wing with a large
fin on top. The cockpit was positioned in front of the aircraft, within the large vertical
stabilizer. To provide a better view of the lower parts of the nose, it was glazed. The
landing gear consisted of three small landing wheels which retracted up into the wing-fuselage.
Given that it was to be used as a test glider, no operational engine was ever to be used on it.
While it was under construction, preparations were made for its first test flight. As it
was a glider, it needed a towing aircraft, and a Sibel Si 204 twin-engine aircraft was chosen
for the job. However, this was not to be done like any other glider, being towed behind the larger
aircraft. Instead, the DM-1 was to be placed above the Si 201 in a frame, in a similar combination
as the Mistel project. In any case, the glider was almost completed by the time the war ended and
was later captured by the Western Allies. Under the US Army's supervision, the glider was fully
completed and sent to America for evaluation. The precise purpose of the P 13a is
not quite clear, even to this day. Despite being briefly considered for mass
production, no official offensive armament is mentioned in the sources. So how would
the P 13a have engaged the enemy?. In an after war interrogation by British officers,
Lippisch was asked if the P 13 was to be used as an aerial ram aircraft. He responded
“.. The possibilities of using the P.13 as a ramming aircraft had been considered
but Dr Lippisch did not think that athodyd propulsion was very suitable for this purpose
owing to the risk of pieces of the rammed aircraft entering the intake. This would
be avoided with a rocket-propelled rammer…” This statement contradicts the building
description issued in late 1944. “...Due to tactical considerations, among other things,
the speed difference of fighters and bombers, preferably when attacking from behind, though
the thought was given to the installation of brakes .. and although ample room for weaponry is
present, the task of ram fighter has been taken into account – so that the ramming attack
will not lead to the loss of the aircraft, thanks to its shape and static structure.”
This meant that this concept may have been considered by Lippisch at some point
in the project's development. The P 13 overall shape closely resembles aircraft that were
intentionally designed for this role. That said, the use of such tactics had been considered
but rejected, as it was seen as a futile and flawed concept. The project itself never got
far enough to have an armament decided for it. In May 1945, Lippisch and his team had to flee
toward the West to avoid being captured by the advancing Soviets. They went to Strobl in
Western Austria, where they encountered the Allies. Lippisch was later transported to Paris
in late May 1945 to be questioned about his delta wing designs. He was then moved to England, and
then to America in 1946. The following year, American engineers with the National Advisory
Committee for Aeronautics tested the DM 1 glider at the unique Full-Scale Wind Tunnel of the
Langley Memorial Aeronautical Laboratory in Hampton, VA. The test seemed promising and it was
suggested to begin preparation for a real flight. Ironically, Lippisch was not mentioned
in this report, as technically speaking, he was not involved in the DM 1 project.
Nevertheless, he was invited for further testing and evaluation of this glider.
Whether this glider and work had any real impact on the US designs is not quite clear.
Despite no flight-ready aircraft ever being completed, one full-size replica of this unusual
aircraft was built after the war. The replica can now be seen at the American Military
Aviation Museum located in Virginia Beach. This concludes our look at the
DM-1 and P 13a. What do you think about these two aircraft? Wunderwaffe or
Wunder-waste-of-time? Let us know in the comments. If you like what we do and want
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