QDMQDMQDM
30th Jun 2003, 23:54
Anyone else been into this strip deep in the Rhone valley? I took the Super Cub in today to stick it in a hangar for a few days against some forecast storms. Well, what a surprise.
Looked very innocuous, forecast wind blowing North-South down the valley, about 5-10 knots in the surface, smooth flight from 7,500 feet down to about 3,000 feet, smoke from factory chimneys agreeing with forecast wind, approach from the North, get near the overhead at 1700 agl (field is 1300 feet amsl) and all hell breaks loose. Bad, bad turbulence, looks like the wind is the opposite direction to that on the ground, what the hell is going on?! Thrown about a lot and couldn't make out the windsock, so headed back north and all went quiet again. Came back south, same thing, so entered the circuit downwind at 2200 feet for the northerly runway, lots of turbulence, but it looked like a North-South wind, as per the factory chimneys. Missed approach off the first one, 500 feet circuit for the second and got in, but very, very blowy down to about a hundred feet, wing drops, 20mph airspeed excursions etc. On the ground, calm 5-10 knot northerly, looks like a lovely calm day for flying.
The answer? 3 miles south of the airfield, the Rhone valley narrows to a couple of hundred yards from about 5 miles wide and convective, contrary winds are very common. The landing directions switches all day apparently.
Interesting lesson. Moral? Be prepared for the unexpected, especially in the mountains, look for topographical influences on winds like a hawk and always pack an extra pair of underpants, even for short day trips.
David
Looked very innocuous, forecast wind blowing North-South down the valley, about 5-10 knots in the surface, smooth flight from 7,500 feet down to about 3,000 feet, smoke from factory chimneys agreeing with forecast wind, approach from the North, get near the overhead at 1700 agl (field is 1300 feet amsl) and all hell breaks loose. Bad, bad turbulence, looks like the wind is the opposite direction to that on the ground, what the hell is going on?! Thrown about a lot and couldn't make out the windsock, so headed back north and all went quiet again. Came back south, same thing, so entered the circuit downwind at 2200 feet for the northerly runway, lots of turbulence, but it looked like a North-South wind, as per the factory chimneys. Missed approach off the first one, 500 feet circuit for the second and got in, but very, very blowy down to about a hundred feet, wing drops, 20mph airspeed excursions etc. On the ground, calm 5-10 knot northerly, looks like a lovely calm day for flying.
The answer? 3 miles south of the airfield, the Rhone valley narrows to a couple of hundred yards from about 5 miles wide and convective, contrary winds are very common. The landing directions switches all day apparently.
Interesting lesson. Moral? Be prepared for the unexpected, especially in the mountains, look for topographical influences on winds like a hawk and always pack an extra pair of underpants, even for short day trips.
David