Admit ...when you see a drawing like this, you really get the
bird-feeling and dream about soaring over forests and mountains
like a eagle. If not, i do get that feeling. This
pilot-inside-airplane concept gives me that feeling.
And then i start wondering: "Why are there not so many airplanes
Many people talk about the prone pilot position and many have
opinions, but ...nearly nobody tested the concept the last years.
So ...i did it for my own satisfaction. Is prone really easy to do
or it is a problem like many sceptics say.
During X-mas holidays in 2011, i used some furniture to test
this prone position. At first i wanted to test the position like it
is known from the drawing of the Horten HXc.
Before i begin the reports on the tests, i need to tell you that
most info about the prone position of the Horten airplanes talk
about a angle of 30° for the upper body.
My findings test with 30° upperbody and 20° upperlegs
even after 10 seconds i had pain in the lower part of my back
(sensitive area for me). Imagining to feel the shocks during a
landing in such a position does make me think it is not a good
idea. If you could land on your feet, it might be ok, but ...first
you need to "survive" the time in the air in that position. Again
...not good for me.
Please, note that here i still try to keep my head upright.
Later i changed that point of view.
My findings test with 30° upperbody and 30° upperlegs
I noticed the following:
Without the support of your knees you slide down along the 30°
plank. A hip-harness can prevent that.The elbows feel more at ease
below the body than beside the body like in Horten IV. Reimar
Horten probably did it to keep the cockpits as tiny as possible.
But ...i wanted to know if this position is comfortable. I might be
wrong with my findings as i didn't test the position toooo long and
i recall that during long car rides i like to lean my arm on the
armsupport of the door. Hmm ...maybe more tests will show better
The wrists rotate less upsteering than downsteering. And we all
know that the rotation for pitch will triple (Reimar Horten used a
pitch-roll mixer of 1:3). Might be a problem to just count on the
wrists. But ...during the running it is better to wrist steer for
less steering oscillations from the running.
The long duration test
I installed the test couch and placed a TV in front of it
(counting on the thought that i needed to see forward in a
horizontal line). My shin was resting on a cushion. I was planning
to view a long movie in this position. Toughest question became
...which movie to see. :)
Here are the notes i took during the tests in the test
couch set at 30° angle for upperbody and upperlegs. Oh yes, the
film was the newest Blueray of the first episode of Star Wars, the
Phantom Menace. :)
- 21:11 start
- 21:22 shin feels like i will not be able to do this for three
- 21:36 knees get soar
- 21:37 without chin rest
- 21:45 test couch too wide. Arms start to feel numb where couch
- 21:53 pain middle of back
- 22:05 hard to sit still. Moving a lot
- 22:25 drinking is tough in this position(bottle of Lipton
Ice-tea)(need straw next time)
- 22:30 with hands under chin it goes well, without not
- 22:50 knees hurt
- 22:55 the fillings in my mouth even start to hurt (strange
feeling)(chin was on cushion)
- 23:00 No prone pilots in my next drafts any more!
- 23:05 Anakin Skywalker gets in spaceship. I get in pain. Chin
pain, knee pain. I quit the idea of a comfortable prone position!
(giving my back a more upright position and placing hands under
- 23:20 I step off test couch. I feel more air getting inside my
lungs. Star Wars rules! :) "
At this point i was no longer convinced to keep the
prone position as a good idea. Not many pilots
will handle this pain just for a good flight. I start to think
that Mr. Sheidbauer (Horten's test pilot) was a really tough
My findings test with 20° upperbody and 20° upperlegs
My findings were:The head has the same rotation freedom like in
the 30°, except ...the upperview is totally gone this time. At 30°
you had still some ...but not much.You clearly see that the frontal
area gets reduced a lot. You feel more like racing in this
The more comfortable prone support
During my tests i came to the idea that maybe the reason for my
pains during my tests was the bad support of my body and the
position of my head.
Why did i try to force my head to a nice vertical position?
Hanggliders don't use that kind of head position. They look half
down most of the time.
Could i make a support that is better shaped to my body? Yes, i
can. And the technique is not really hard to get that result. I
just made a plastic sack of about 2m (6.5 feet) long and about 60
cm (2 feet) wide. I filled it with expanding foam (a mixture of two
chemicals you can find in the online composite shops). I let it
foam a bit, than placed it in a U-shaped wooden frame which had a
support (plastic tube) to get my legs to the proper angle. I placed
a few layers of insultaion on the plastic bag to shield my body
from the heat of the chemical reaction in the bag (do not do this
without that heat protection!!!) and ...i stayed in that position
for nearly half a hour.
I took the foam home and installed it at a angle of 10°. Why
10°? Well, i wanted to see if it would be possible to reduce the
frontal area of the pilot to the max. Why not 0°? To understand
this you need to look at the drawing of the HXa. If i would place
the pilot at 0° his legs would stick out the upperside of the wing.
Using 10° would make it possible to get more under the top line of
the airfoil of the mid section.
This is what i wrote after the test:
"me super happy.
Just made a test on my foam negative shape. You know ...the thing
to lay under me while testing prone poisition. Well, i saw
only a movie of 1.5 hours. So ...you would think it went wrong, but
...no no, after 1.5 hours all i could say is that the skin support
needs to be removed. I felt nothing strange as cramps in my muscles
or ackes in my back. After 1.5 hours i was even willing to do
another movie. But ...that will not be needed. I am convinced. It
works! All you need is a really good shape to lay onto.
10,20,30 degrees. I guess it does not matter. All that changes
is the place on earth you see as your head points a bit downwards
like the pilot of hanggliders know too. But if they can fly that
way with mostly looking downwards, why would i not do it?"
I got hold of a few pictures by Manfred Poznanski, which he took during the
presentation of the Horten HIV replica. It shows a good view on
the pilot. Now ...look at his hands! I was right in my thinking
that the wrists are hard to be upright. You need to use force to do
that. Here you can see that Reimar Horten thought the same. He
placed the hands at a certain angle inwards. That position feels
more comfortable indeed.
I am very optimistic about the prone pilot position. It really
is not hard to get it right. Just the idea to get a pilot really IN
a wing sounds like science-fiction to many, like history to Horten Flying Wing Believers and like fun to
guys like me.
But if you ever want to use a prone position in your own
designs, take care to test the rest of the ergonomics. The freedom
to move, the force you can put into the steering, how to fix
("seat belts") and release yourself into that
position without help, how to get in this position without being a
elastic person and ...how to get the spar in your design when the
pilot is where the spar should be. Don't underestimate the
Have fun with your experiments. And feel free to report to me.