Question about landing characteristics of "flat wing" Pitts from other Pitts models

[Ernie]

I fly a Waco Taperwing, which shares the M6 airfoil with the S1C. I am in the process of writing some notes on how the airfoil affects the landing characteristics of the Taperwing. Just curious about the S1T compared with the symmetrical airfoil airplanes. I am comparing the M6 to Clark Y type airfoils.

Ernie

[martymayes]

Ernie, not sure if you meant S1T. The plans build Pitts S-1C (and S-1D) had an M6 airfoil, sometimes referred to as the "flat bottom" wing and the S-1T had a symmetrical airfoil.

[rwanttaja]

Ernie, the Biplane forum has a number of Pitts owners, and, in fact, a subgroup dedicated to them. Suggest you try there.

http://www.biplaneforum.com/

Ron Wanttaja

[Ernie]

Ernie, not sure if you meant S1T. The plans build Pitts S-1C (and S-1D) had an M6 airfoil, sometimes referred to as the "flat bottom" wing and the S-1T had a symmetrical airfoil.

Thanks, showing my ignorance.

Ernie

[WLIU]

Before you think about the airfoil to compare performance, take a look at the wing loading and the aspect ratio of the wings. Aspect ratio has a big effect on the performance of a wing. The Taperwing wings have a higher aspect ratio which is more efficient.

The Most Pitts also likely have higher wing loadings than the Waco, even though the Waco is a heavier airplane. This can translate into higher landing and takeoff speeds. Most Pitts fly the pattern at 80 - 100 mph. The very few 135 HP Pitts out there fly slower but most S-1's are at least 150HP these days.

Waco's are more comparable to S-2's, but all of the S-2's have symmetrical airfoils in the wings.

Best of luck,

Wes
S-2A N78PS

[Ernie]

I do realize that there is more to airplane performance than the airfoil.

The M6 does have some unique characteristics that affect some types of landing. The M6, in comparison to a Clark Y, stalls at a higher angle of attack but makes less lift. On the other hand, it retains more lift after the stall. As I began to understand that, some of the neighborhood gossip about the Taperwing began to make sense. When I checked out in the Taperwing, all of my landings were from a Poweroff 180, with admonitions to go around rather than attempt to save a landing with power. As I tried to teach myself straight in approaches with a little power, it got really interesting. The basic difference is relative wind direction. Parallel to the runway, the flight path is nowhere near stalling; there is still a lot of lift in the wings. Even if you touch three wheels, you are for all practical purposes in a wheel landing. The tiny rudder and slightly squirrelly landing gear geometry make for a very interesting landing. The Classic Waco (YMF) I also fly regularly is a totally different animal, and you are right, most of the differences are not the airfoil. But the M6 makes a significant contribution to the challenges.

Here is the NACA analysis from a long time ago: https://digital.library.unt.edu/ark:...adc59645/m1/2/

I have almost no experience in Pitts aircraft, and I was curious about the differences there.

Ernie

[WLIU]

The challenges in landing that are being described have more to do with the tail volume and how the wing and fuselage blank out airflow over that tail when all 3 wheels are on the runway. Most of these airplanes have landing gear geometry that has the airplane still flying when all 3 wheels are on the runway. And with the tail down, the rudder is much less effective. We think that we want to have no wind when we land, but in fact a 10kt wind down the runway keeps the rudder working much longer. And if there is a crosswind, when we slow, with the tail down, we need all of the rudder area we can get to keep the airplane straight. Some airplanes like Pitts have larger rudders that are more effective, even at slow speeds with less airflow in them. Some airplanes have tails sized for cruise flight and those tails are much less effective when landing.

The other factor mentioned is the use of power to "salvage" a landing. Any small airplane that has a relatively large propeller requires smooth throttle inputs. Better to add a little power on short final in anticipation of a challenging landing than a sudden throttle input after a bounce.

Best of luck,

Wes
N78PS