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By the 1960’s, the idea that a jet could take off and land vertically was no longer
the stuff of science fiction, and freeing jets from needing runways was
going to revolutionize their use.
While the British led the way with the first jump jet fighter, Germany set out to build
something even more ambitious.
The world’s first vertical jet lift transport, combining the speed and range of a jet with
more lifting power than just about any helicopter in the world.
This was a plane that would revolutionize Germany’s air force.
A truly versatile machine that could even redefine air travel itself.
But developing the world’s first VTOL transport would be fraught with technical challenges.
It’s called Vertical Take Off and Landing, or VTOL.
And getting a jet to do it would prove to be one of the most difficult challenges in
aviation history.
Without forward motion, a plane’s wings can’t generate any lift, and it means a
VTOL jet must rely entirely on its engines to get airborne, by directing thrust downwards.
But making enough power to lift off vertically is only part of the challenge.
Jet thrust must also keep the aircraft stable and oriented.
Because while hovering, conventional control surfaces aren’t able to control the aircraft.
And a VTOL jet still needs to fly like a conventional plane.
And one approach is to use dedicated lift jets to get airborne and a separate jet for
conventional forward flight.
Another approach is to develop an engine that can do both.
Vector thrust downwards for vertical lift and rearwards for forward flight.
A third way is to combine dedicated lift jets and vectored thrust.
These were enormous engineering challenges.
But throughout the 1960s, several countries launched VTOL jet development programs.
Because freeing jets from needing runways could make all the difference in the next
major conflict.
During the Second World War, a grass field was just about all that military aircraft
needed to get airborne.
Grass fields are hard to destroy and easy to replace.
And a World War Two-era fighter needed only a few hundred feet of it.
But in little over a decade that all changed.
Because jet aircraft needed thousands of feet of concrete runway to get airborne, creating
a strategic vulnerability.
In the opening hours of a conflict, runways were going to be the first targets and their
destruction would render an entire air force inoperable.
During the Cold War, nowhere was this vulnerability more apparent than in West Germany, where
most air bases were just a few hundred kilometers from Soviet Bloc countries.
Within easy striking distance of aircraft and cruise missiles.
But VTOL jets could operate without runways.
And for West Germany, the technology seemed like the perfect solution.
Because aircraft could be stationed throughout the country, away from threats.
Kept hidden under the cover of forests or inside buildings Aircraft could even use the
country’s Autobahn highway network to stage operations.
In 1960, West Germany set out to build an air force around VTOL technology.
Starting with the development of a supersonic fighter with unique pivoting wing-tip jets
engines.
A year later, work also began on a VTOL strike fighter, a ground attack aircraft to serve
as the mainstay of West- German air force.
But critical for supporting these aircraft out in the field would be a jet lift transport.
A plane that could deliver supplies and personnel to remote forward operating bases.
And in 1962, West German aircraft builder Dornier was assigned the enormous challenge
of developing it.
Getting a jet to lift off vertically was difficult enough.
A VTOL transport would also need to lift several tons of cargo.
And to do it, engineers would need to develop everything from new flight control systems,
engine layouts, to avionics.
This is the Dornier Do-31.
The world’s only vertical jet lift transport.
Using the combined power of two vectored thrust turbofans and eight lift jets in wing-tip
pods, the Do 31 could generate an incredible 66,000 pounds of thrust.
More vertical lifting power than just about any helicopter in the world.
To keep the aircraft stable, engineers developed an advanced computerized flight control system.
Working around the limits of 1960’s technology with an innovative part-digital, part-analog
hybrid computer.
In forward flight, the lift jets would be shut off and the Do 31
would fly like a conventional plane.
And it could reach speeds of over 700km an hour and carry 36 fully equipped troops or
nearly six tons of cargo.
An unprecedented combination of speed, range and lifting capacity.
But developing the world’s first VTOL jet transport would be fraught with technical
challenges.
And it took Dornier almost five years to develop the Do 31’s technologies.
But by 1967, confidence in the aircraft was growing and soon test flights were proving
that Germany’s jet lift transport was more than capable of fulfilling it’s design mission.
And as Dornier moved closer to a production version, some even saw the potential for vertical
jet lift technology to revolutionize commercial aviation.
Because VTOL airliners would operate from helipads, maybe even directly
from building rooftops.
But VTOL jet travel was going to have to wait.
As the 1960s drew to a close, the Cold War evolved into a new phase.
An all out war with the Soviet Union now seemed less likely.
And it meant the development of VTOL capable jets was now less of a strategic priority.
And getting a jet to reliably take off and land vertically proved to be far more challenging
and dangerous than originally anticipated.
By 1968 it was clear that Germany’s VTOL fighter jet wasn't going to
meet it’s design objectives.
And with rising development costs the program was cancelled.
And that put the future of Do 31 in doubt
More than anything, what west Germany needed was a partner
to help shoulder development costs.
And while Dornier managed to get the attention of the U.S military and aerospace industry,
partnerships never materialized.
Like other VTOL jets, the Do 31 had some serious limitations.
Sure, its ten jets could lift more than just about any helicopter in the world.
Much of what they were actually lifting was the aircraft's own weight.
Ten jet engines and the fuel needed to keep them all running made the Do 31 incredibly
complex and heavy.
And the noise would've been a deal breaker for any civil application.
Dornier tried to impress crowds at the 1969 Paris air show, flying alongside Britain's
harrier jump jet in a coordinated aerial display.
But excitement over VTOL was starting to fade and the plane garnered little in the way of
serious interest.
And without a development partner or buyers, Dornier was forced to
cancel the project in 1970.
The attack aircraft it was intended to support would eventually suffer a similar fate.
Of the many VTOL projects launched in the 1950s and 60s, most would end in failure.
Unable to overcome monumental engineering challenges or the inherent limitations of
jet lift technology
The world’s only jet lift transport promised to combine the speed and range of a jet, with
the versatility of a helicopter.
A machine designed to address a pressing strategic challenge.
Decades earlier Japanese engineers were also trying to solve their own strategic problem.
And their solution would be to combine the stealth of a submarine with the strike capabilities
of an aircraft carrier.
Japan’s underwater aircraft carriers were some of the most fascinating machines to come
out of the Second World War.
And you can learn their incredible story in my latest video.
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