A new direction for an old thread: Crosswind landings

It obviously has been a long winter in your part of the country. You
badly need to go flying!


wrote:
Yes, well said. But still wrong, in this sense:

Side slipping does not change your direction. What you have done is to
define the limits of side slipping as an alignment maneuver. This
doesn't make side slipping and crabbing additive. It simply says that
you've been taught or you prefer to uncoordinate the aircraft early on
final to align the gear with the runway. However, the rudder will only
allow a finite maximum angle of yaw, which limits the amount of bank
you can use before the wing turning force exceeds the fuselage force
and you start turning. So put another way, a side slip is only useful
for gear alignment up to some fixed crosswind component speed. Above
that speed, you will need to add a skid before touch down... but
wait... your rudder is already full over. How will you align the gear?
Well, if you had both the full authority of the rudder and the adverse
yaw or you ailerons, you might be able to manage it. But that would
require a crabbed (coordinated) approach. Which just happens to be the
same path you were moving through the air while side slipping "plus"
crabbing. Do you see why I just can't stomach the notion of side slips
and crabs being additive? There is a reverse logic at work here which
gives the side slip a false role in crosswind management.

Put another way, a side slip is only appropriate for light to moderate
crosswind components and flat landing surfaces. The stronger the
crosswind, the rougher the runway, the more critical it is to have
maximum yaw performance at touch down. Side slips and skids are
additive, but only to the degree that you have any rudder left to yaw
the glider. Since everyone seems to have a preference, I would guess
this is the worst of both worlds.

Think of it another way... if I slow down on final, I'll need to change
my direction to maintain a constant ground track. (This is simple trig
that I'll leave to you.) I cannot accomplish this by adding side slip.
A side slip changes heading only, not track. I must turn in order to
maintain track. This isn't even apples and oranges. This trying to add
fruits and vegetables.

So here I am on final in calm conditions... I slip to the right. I
recover. I slip to the left. I recover. Net force always equals zero.
My flight path remains the same. Track, the same. Heading swings 20
degrees either side of the runway center line. Same thing in a cross
wind. I establish a ground track. I point down the runway. I recover
form the side slip. For amusement I slip in the other direction - with
the downwind wing low (is this a side slip or a forward slip???!!!). I
recover. Net force always equals zero. My track remains exactly the
same while my heading swings through 40 total degrees, centered on my
path through the air.

I'll see if I can't find a new direction to come at this. Redefining
the approach in terms of coordination may be the way. But I really do
need to check out. Be back in a week or two.

OC aka 59 aka Chris O'Callaghan