Hi, are you talking about AOI ?

Steve Carlisle

No :-)

"Angle of Incidence (or AOI) is the angle between the blade chord
line and the plane of rotation of the rotor system." ???

I am talking about the panels behind the cockpit relative to the
direction of flight that are greater than 7 degrees. The Glass Goose
is an example.

There are a limited number of single engine sea plane configurations
that minimize drag. None of them have that configuration.

Lake, Coot and Sea Wind. High mounted engines that allow more or less
perfectly stream lined fuselages.  The High mount is necessary to
keep the prop out of the water spray.

The Coot did not take full advantages of the possibilities. Also the
prop could have been driven by a longer belt lowering the weight of
the engine and moving the prop higher. See the attached picture.
These airplane have rather bad handling due to the weight and thrust
of the high mounted engines relative to the wing. More power causes a
nose down moment as does landing in water due to the inertia of the
high mounted heavy engine.


IMHO the Sea wind is the best of the group.

For twins there is more variation. Gull wings are a good one Dornier
DO 26, Martin PBM, and an Italian lite sea plane  that I don't
remember the name of.

The next category  is pylon mounted wings with multiple engines. The
PBY is the best example. Dorneir D18D is another.  These usually
have some high drag strut bracing.

BTW if the pilot and passenger are semi reclined the cabin top of the
Glass Goose AKA Sea Hawker could be lowered and the wing supported
with a short pylon above the cabin top which would benefit the
aerodynamics some what.

Then the deep fuselage with wing mounted engines.  There is a whole
raft of those including the Spruce Goose and the Martin Mars. The
only feature that causes extra drag is the step and the extra deep or
high fuselage. As they get bigger this is less of a problem.

All the older  strut mounted high wing sea planes are high drag. The
Dorneir Wal was the best of the group.

Sea planes are a difficult design problem due to the two mediums it
must operate in.


Paul Lamar


Thanks for the info Paul, sorry about the confusion, I was meaning
AOI in regards to airplanes.

Steve Carlisle

What is your definition?


Paul Lamar


Hi Paul, just learning this stuff, but angle of incidence  and angle
of attack seem to be one in the same, is that right?

Steve C

They seem to be but AOI is associated with propellers however it is
rarely used Pitch is used most often. That is not an angle per se. It
is far the propeller will go in one revolution.

AOA is used very very frequently to refer to wings. In fact there is
an AOA instrument to warn the pilot of a stall among other uses. Navy
pilots were taught to use an AOA instrument as I recall .

Paul Lamar



Hi paul, The Seawind may be the best of the bunch, but it has killed
16 people so far, including their chief test pilot. An ex friend of
mine had one, I flew in it several times, it was a real dog, very
heavy in the controls, under ruddered and under elevated. It
eventually killed him trying to take off from a lake, it porpoised
and dove in killing him and badly injuring his wife.

Chris Hoskins.

Well as I recall the owner of the company was stubborn about fixing
the problems. He refused to do it and did not notify all customers
of the problems.

It is just the lowest drag configuration but is basically the same as a Lake
or Coot. The mass of the engine up high causes the pitch problem. Yes you need
a lot of elevator.

Dornier figured out years ago sea planes need long fuselages to deal with those
high engines.

Hitting a wave at 60 or 70 MPH is like hitting a brick wall. A top heavy sea plane
is going to want to nose over. If you apply power at that point it is worse.

That is why I propose using  a long cog belt in the rotary powered Coot to lower
the weight of the engine.

Paul Lamar

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