Aerosport LH-10

Here you go:

http://ibis.experimentals.de/downloa...lvibration.pdf



"Morgans" wrote in message ...
.....

Surely someone out there can provide some of the links to the readings I did
a few years back, as to all of the developmental problems that they had,
dealing with the BD-5. There were volumes written, very detailed, some very
technical pages written on the case, and studies on the problem in a very
scientific study, as I recall.

Someone?

I am not saying that the problems are impossible to overcome. I am saying
that the problems are significant, and are to be expected with a drive
system of this type, and are more likely, than not, to show up in such a
system.

If you are thinking about a plane with that configuration, the writings
should be manditory reading, or if you are just interested in all things
mechanical, they are also very interesting.

You might be able to surf and find the studies yourself. Someone did give
me some good starting places way back, to explore. It would be nice to get
some clues provided for you, this time.

Have a good one!
--
Jim in NC


For me these are probably some of the considerations for
a conventional tractor propelled verses a push propeller:


ADVANTAGES

Efficiency can be gained by mounting a propeller behind the fuselage,
because it re-energizes the boundary layer developed on the body, and
reduces the form drag by keeping the flow attached. However, this
effect is not nearly as pronounced on a small airplane as it is on a
submarine or ship, where it is quite important due to the much higher
Reynolds number at which they operate.

Wing efficiency increases due to the absence of prop-wash over any
section of the wing.

Rear thrust is somewhat less stable in flight than with a tractor
configuration. This has the potential to make an aircraft more
maneuverable.

Visibility of a single-engined airplane is improved because the engine
does not block forward vision. Consequently, this configuration was
widely used for early combat reconnaissance aircraft, and remains
popular today among ultralight aircraft.

The propeller of a single-engined airplane can be placed closer to the
elevators and rudder. This increases the speed of the air flowing over
the control surfaces, improving pitch and yaw control at low speed,
particularly during takeoff when the engine is at full power. This can
be beneficial while bush flying, especially when taking off and
landing on airstrips bounded by obstacles that must be avoided while
the airplane is moving slowly.

The engine is mounted behind the crew and passenger compartments, so
fuel does not have to flow past personnel, any leak will vent behind
the aircraft, and any engine fire will be directed behind the aircraft
(however, this arrangement puts the empennage at greater risk, if
there is one -- but this is less of an issue if the fire occurs on, or
as a consequence of, landing). Similarly, propeller failure is
unlikely to directly endanger the crew.

And then we have the DISADVANTAGES-


The pusher configuration can endanger the aircraft's occupants in a
crash or crash-landing[citation needed]. If the engine is placed
behind the cabin, it may drive forward under its own momentum during a
crash, entering the cabin and injuring the occupants; however there is
no case where this has been reported to have occurred (in the US and
UK accident records). Conversely, if the engine is placed in front of
the cabin, it might act as a battering ram and plow through obstacles
in the airplane's path, providing an additional measure of safety.

Crew members may strike the propeller while attempting to bail out of
a single-engined airplane with a pusher prop. This potentially
gruesome scenario helps to explain why pusher props have rarely been
used on post-WWI fighters despite the theoretical increase in
maneuverability.

A less dire but more practical concern is foreign object damage. The
pusher configuration generally places the propeller(s) aft of the main
landing gear, but often placed above the wing. Rocks, dirt or other
objects on the ground kicked up by the wheels can find their way into
the prop, causing damage or accelerated wear to the blades. As a
result, pusher aircraft such as the canard homebuilts are not usually
operated from unimproved runways. Also, a few centreline pusher
designs place the propeller arc very close to the ground while flying
nose-high during takeoff or landing, making the prop more likely to
strike vegetation when the airplane operates from a turf airstrip.

When an airplane flies in icing conditions, a layer of ice can
accumulate on the wings. If an airplane with wing-mounted pusher
engines experiences wing icing and subsequently flies into warmer air,
the pusher props may ingest pieces of ice as they shed, posing a
hazard to the propeller blades and other parts of the airframe that
can be struck by chunks of ice flung by the props.

The propeller increases airflow around an air-cooled engine in the
tractor configuration, but does not provide this same benefit to an
engine mounted in the pusher configuration. Some aviation engines
experience cooling problems when used as pushers. Likewise, the pusher
configuration can exacerbate carburettor icing. Some air-cooled
aviation engines depend on air heated by the cylinders to warm the
carburettor(s) and discourage icing; the pusher configuration can
reduce the flow of warm air, facilitating the formation of ice.

Propeller noise often increases because the engine exhaust flows
through the props. This effect is particularly pronounced when using
turboprop engines due to the large volume of exhaust they produce.
Aviation enthusiasts can often hear a Piaggio P180 Avanti approach due
to the loud high-pitched wail produced by the engine exhaust blowing
through the props.

Vibration can be induced by the propeller passing through the wing
downwash, causing it to move asymmetrically through air of differing
energies and directions.

Problems may emerge when using wing flaps on a pusher airplane. First,
the absence of prop-wash over the wings can slow the airflow across
the flaps, making them less effective. Second, wing-mounted pusher
engines block the installation of flaps along portions of the trailing
edges of the wings, reducing the total available flap area.

Placement of the propeller in front of the tail (as referenced in
Advantages) can have a negative side effect: strong pitch and yaw
changes may occur as the engine's power setting changes and the
airflow over the tail correspondingly speeds up or slows down.
Aggressive pilot corrections may be required to maintain the desired
flight path after changing the power setting.

Still, I think the possibility of my having to bail out in flight
are minimal.

Do you or anyone know the approximate "drive-out" price
for an Aerosport LH-10 Ellipse?

Thanks, Mark

"Blueskies" wrote in message
news
Here you go:

http://ibis.experimentals.de/downloa...lvibration.pdf

Yep, that was the primer to the whole treatise.

Anyone who likes mechanical things, at all, NEEDS to read this. If you are
considering something that has a PSRU, or especially a long driveshaft, then
you really need to read it.

Download it, and read it a little at a time, if you don't have a little
while to digest it. To me, it is fascinating reading.
--
Jim in NC

"Morgans" wrote in message
news

"Blueskies" wrote in message
news
Here you go:

http://ibis.experimentals.de/downloa...lvibration.pdf

Yep, that was the primer to the whole treatise.

Anyone who likes mechanical things, at all, NEEDS to read this. If you are
considering something that has a PSRU, or especially a long driveshaft,
then you really need to read it.

Download it, and read it a little at a time, if you don't have a little
while to digest it. To me, it is fascinating reading.
--
Jim in NC
Jim,

That is the article that I had previously lost, and is now properly saved.

It is an absolute "must read" for anyone considering an aircraft with a
reduction drive, and esecially with a remote propeller built from plans or a
kit.

Thanks
Peter

"Peter Dohm" wrote

Jim,

That is the article that I had previously lost, and is now properly saved.

It is an absolute "must read" for anyone considering an aircraft with a
reduction drive, and esecially with a remote propeller built from plans or
a kit.

Yep. I had forgotten that most of the information was in one article, and
what exactly was in it, but I remembered it was enlightening, and valuable
information. I too am glad to have it properly found and saved, again.

I hope people take the time to read it, and don't blow it off.
--
Jim in NC

On Dec 21, 9:59*pm, "Morgans" wrote:

I hope people take the time to read it, and don't blow it off.

Jim in NC

An interesting read and valuable piece of literature
added to my Aviation archive. Thanks.

Mark