I heard and read about them, never actually experienced one until yesterday.
Maybe because most of the time I fly very early and its too cool for the river to make any effect.

Yesterday was landing at a gravel bar at noon, was in the 80s and definitelly I could feel the downdraft.
Was a perfect training scenario to avoid the instinct to pull on the yoke, and give power instead.
Did 4 landings and every time the downdraft was there.

So the warm air rises and cool air doesnt , is that the cause? Cooler air has more lift than warm air though.

This video kind of shows it, it was very noticeable when flying it.

Not just rivers--any body of water that is cooler than the surrounding land will do that. From advice on the Colorado Pilots website about landing at the Marble airstrip: "Be prepared for some sink over the lake at the end of the runway and try to remember that the runway is still over 90 feet wide near the middle." Other types of terrain differences can do the same thing, although perhaps not to the extent of cold water. That's why flying at relatively low altitudes in the summer usually means pretty bumpy travel.

Cary

My understanding of the phenomenon isn't that the water is cooling the air, it's that the warm air that is rising from the heated terrain has to be replaced with cooler air which comes down (or over) to fill the void. Because the space over the water is cooler than the space over the land, that's where the air flows down to replace the rising air. The water isn't cooling the air, it's just keeping it from heating as quickly as the surrounding terrain, so it's the natural pathway for incoming air.

Air cannot rise up unless the space it previously occupied is filled with more air. Flying through a layer of cold air which is not in motion does not cause the aircraft to sink. The aircraft sinks because the air over the water is the refill supply for the rising air over the terrain, and often flowing down in the process.

Air flows are not always predictable. Some mountains experience downdrafts in the afternoon because the desert below them heats so extremely that the air is pulled down the mountains to fill the void.

Hammer wrote:My understanding of the phenomenon isn't that the water is cooling the air, it's that the warm air that is rising from the heated terrain has to be replaced with cooler air which comes down (or over) to fill the void. Because the space over the water is cooler than the space over the land, that's where the air flows down to replace the rising air. The water isn't cooling the air, it's just keeping it from heating as quickly as the surrounding terrain, so it's the natural pathway for incoming air.

Air cannot rise up unless the space it previously occupied is filled with more air. Flying through a layer of cold air which is not in motion does not cause the aircraft to sink. The aircraft sinks because the air over the water is the refill supply for the rising air over the terrain, and often flowing down in the process.

Air flows are not always predictable. Some mountains experience downdrafts in the afternoon because the desert below them heats so extremely that the air is pulled down the mountains to fill the void.

excellent post!

Hammer tells the correct story. The physics of cold air and hot air are predictable. I learned that at Wilson Bar in 2004. It didn't help that I was allowing the plane settle in a little slow on approach while trying to spot steelhead in the Middle Fork of the Salmon in September.
When you go into Wilson Bar at 5pm that time of year you are shrouded by darkness river left and glaring hot light and air river right. it causes a little lateral tornado, maybe a waternado. Cold air on the left is sinking, hot air on the right is rising.
I wound up stalling the airplane right over the water, jamming one of the Cessna 180 gear legs backwards, but still got her onto the runway over that little cliff. The rest of the story is a comedy of errors trying to save the situation with glare in my face, but Sparky Immeson always said in his seminars if you've run out f things to do in a bad situation in a taildragger, flip it. So I did it. Beat the lava rocks coming up and on both sides of the airplane.
But the message is, canyons with dark sides and light sides in the afternoon on warm days are a hazard for downdrafts, and some of them can be powerful.
I sure enjoy the rebuild posts on the Cessna 180/185s. Keep it up.

When I crashed my Pawnee my second season and had to go hat in hand to the old mechanic to lease one, he said, "You've only crashed one? I'm not sure you have enough experience to lease a spray plane from me."

Getting slow means we have to be ready with rapid throttle control movement. Being slow, however, is the only right way to crash.

Great info, thanks for the replies.