Cheers, Clarrie and safetypee. Yes, had done the google but had found nothing specific to the DC-9 wing that was from an
authoritative source. Plenty of discussion of isobars and stagnation points in aerospace.org and some nice contributions on !!!!!!!!!!!!!! forum re the DC-8 wing.
Taking a look at the vortilon on our machine, it makes sense w.r.t. above discussions of leading edge attachment line. "Preserving lift on the outboard wing sections, so the inner wing would stall first" also makes a lot of sense.
I was curious as to why it was placed at 1/4 span, rather than further from root/closer to tip.
Am now reading DC-9 aerodynamicist Dick Shevell's article on 'his' wing.