Buffet with sideslip
Ironflight said:
Take a look at Randy Lervold's web site - he has a great discussion on this
One of the issues that was discussed on the Yahoo group was tail buffet in a side-slip, which seemed to magnify the effect. A side slip (such as would be caused by a rudder reversal) can cause vortices and other turbulent wakes to be shed from fuselage, gear legs, wing root intersections, and the root edges of the flaps, if they're deployed.
As for straight ahead power off stalls, I hadn't seen Randy's writeup before. Definitely interesting information, and pretty definitive that the fairings are involved in some way. I still wonder what the exact mechanism is, however. Randy lists stall speeds with and without the fairing, but there are two speeds that I think are relevant to the discussion. First, the speed at which buffet starts, and second the stall speed.
I'm a little suspicious that the fairings reduced the stall by 10 mph, but it could very well have changed the buffet onset speed by 10 mph. Measuring power off stall speed with high accuracy is a little tricky if you're not measuring AOA and logging the data. Looking for the pitch break or buffet is ok from a pilot perspective, but does not really pinpoint the speed where max lift coefficient is achieved.
Given the location of the gear leg intersection on the -8, I could see the wake of the gear intersection going over the top of the wing at high AOA without the fairing and then being forced under the wing with the fairing. This could be enough to keep it away from the tail.