Originally Posted by
Maoraigh1
Max wind from Campbelltown METAR in online archive was 20 mph at noon that day. That doesn't suggest turbulence downwind of Arran that would trouble a Pa28.
Hmm. Some years ago I was flying downwind of Snowdonia near Anglesey with Caernarfon surface wind < 5 KTS when we were hit by lee side turbulence. I have never experienced turbulence like it; I could not control the aeroplane, I was a passenger, my head was hitting the canopy despite a tightened aerobatic harness, the aeroplane was being tossed like a cork on a rough sea, and wisps of cloud were forming and dispersing around us in the otherwise clear air. I feared for the integrity of the airframe (Chipmunk, so quite strong). I headed away from the hills and Just as suddenly as it had started, it spat us out.
A few years before that incident a C150 I used to fly out of Manchester crashed on the lee side of Kinder Scout in Derbyshire in severe sink at night, with Manchester Airport (who was working them) reporting a surface wind of < 5 KTS. The AAIB report indicated there was an unusual air formation over the hills funneling the surface air between the upper mass and the top of the hill; the estimated surface wind speed on Kinder summit was > 50 KTS! Thankfully the pilots escaped with minor injuries.
I suspect we encountered a similar phenomena that day near Snowdonia.
Local lowland calm winds do not mean you will not experience deadly turbulence downwind of mountains.
Not suggesting of course that that was the case here. Just passing on some experience I hope might be useful regarding flying downwind of mountains even in low reported surface winds.