On May 28, 12:21*am, Roel Baardman wrote:
After speaking with an instructor about my Pilatus B4 landings, he argued that
the angle of incidence on this glider has a great influence on the landing
characteristics.
I looked it up, and it was only 1.5 degrees. With the tailplane oriented at -3
degrees.

However, I cannot figure out what other gliders have as the angle of
incidence. I have 6 degrees in my head somehow, but I'm not sure where I get
this from. Searching on Google does not give me figures, only stories about
changing it (from Ls6 to Ls8 for example).

I'm therefor wondering: can you tell me the angle of incidence on your glider
if you know it? And how does it effect take-off and landing characteristics?
For example: some people in my club argue that the Discus2 take-off
characteristics are also to be blamed on its angle of incidence.

regards,

Roel

Angle of incidence does vary from glider to glider, and it's a useful
point to note when making transitions to new gliders. Trainers like
the ASK21 have a fairly high angle of incidence. Duos and standard
class gliders have much lower angle of incidence, the latest (28, D2)
especially. That, along with c.g. much further behind the main gear,
is worth reflecting on and preparing for in a transition.

Low angle of incidence in unflapped gliders means the fuselage is more
aligned with the airflow at high speeds. Good for high speed
performance, but it means that the nose points way up to achieve a
high angle of attack at low speed. They can't achieve a stalling
angle of attack even with the tail wheel on the ground. Thus, they
have to take off at substantially higher airspeeds. There is a
tendency to roll down the runway forever on the first few flights. One
answer is to take off with the fuselage at a much higher pitch
attitude in order to produce the same angle of attack at takeoff.
Similarly, If you land close to a stall you will hit the tail wheel
first and then plop down on the main.

That's also why the nose is very high on tow and while thermaling.
Some pilots find themselves thermaling at too high speeds early in the
transition. Part of the reason is that the nose needs to be much
higher on the horizon at thermaling angles of attack. If you put the
nose at the ASK21 pitch attitude, the duo or a standard class glider
will be screaming along.

It's also useful to note that where the nose is pointing is not where
the glider is going. That's what's going on with the feeling that the
nose is high on takeoff, tow, and thermaling -- the nose is pointing
up though the glider is gliding down. The converse issue happens at
high speed. The wings are very efficient at high speed, so putting the
nose down and pointing at the runway just means you speed up to 90
knots and keep going flat. Glider looks like this: (moving left to
right) \ \ \ . That's part of the feeling that "spoilers don't
work." No, you're not using them! To an eyeball approximation, the
glide angle is always the same, but pointing the nose up or down just
changes the airspeed.

More than you asked for, but I've learned a lot about these sight
angles while helping new pilots transition to our duo discus and asw24
lately

John Cochrane