Caution:. Wake turbulence

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Aerowerx

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Big airplanes are not the only thing that causes wake turbulence, nor are small planes the only ones that have a problem with it.

I was cruising down the freeway today at 70 mph. There was an 18 wheeler several hundred feet ahead of me.

A group of 5 Canada geese came up from a pond on the right, and crossed the freeway about 40 feet up, just as the truck went under them.

The goose at the back, lower down than the others, suddenly bank right about 40 degrees and nosed down about 30 degrees,. Lost about 10 feet of altitude then recovered.
 

lr27

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Too bad we don't have a video!

If I get behind an 18 wheeler at highway speeds with a car, I definitely notice buffeting in a light car. I REALLY notice it if there's a boat on top of the car.
 

Dana

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During my brief experiment with an old weightshift Quicksilver, I encountered wake turbulence from a powered parachute that was making low passes over the field (I was doing crow hops, 5' high). Fortunately I was so low, the only damage was some tubes.

A PPC isn't a large aircraft, but it's heavier than that Quicksilver, and the inefficient low aspect ratio wing of the PPC means lots of induced drag and wingtip vortices.

Dana
 

lr27

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Sometimes, flying indoors, you can see a light free flight model drop a bit when it passes close behind another one. I've also seen a really light one of mine get sucked in by the wake of a spectator who was trying to get out of the way!
 

lr27

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Yes. But it would have made an interesting video if it was possible. You just need to start using a dash cam like so many people seem to in Russia, judging by all the accident videos on YouTube. ;-)
 

Angusnofangus

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I flew through a helicopter wake in a Cessna 150 many years ago. It was not a pleasant experience. The airplane was slammed really hard by the turbulence. Note to self, stay clear of helicopters.
 

lr27

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I was a passenger in a Jetranger (helicopter) doing a tour of Boston. It wasn't a windy day, but when we flew downwind of the Hancock building, we could definitely feel it. Ugh! I had the controls earlier, or at least the basic ones, but when we went over an antenna that was at least 2/3 our altitude, I said "You take it!". The rest of the time the ride was nice and smooth.

The Hancock is the big, mirror-like building shown here:
https://goo.gl/maps/n73h7qs7rKu
 

BBerson

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I flew through a helicopter wake in a Cessna 150 many years ago. It was not a pleasant experience. The airplane was slammed really hard by the turbulence. Note to self, stay clear of helicopters.
Your first sentence conflicts with your signature line. :gig:
 

timberwolf8199

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Grand Rapids area, MI, USA
In college my roommate (also an aero engineering major) told me that drafting only worked at high speeds such as in racecars. That you would never notice a wake at legal speeds. I laughed heartily. Then I realized he was serious. I expressed my disagreement in a less derisive manner. He refused to budge from his stance. I offered to take him for a drive so I could illustrate my statements. He declined. The disagreement popped up once or twice later that week but wasn't resolved. Another week went by and I was giving him a ride home for the weekend so I took the opportunity to tuck in behind a semi where the buffeting was strong and sat there for a while. When I pulled around it I said something like "glad to get out of that." A few miles later I found a pickup with a cap on it...as we came up behind it and felt light turbulence I said "not again" and moved on. The topic never came up again.
 

Aerowerx

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In college my roommate (also an aero engineering major) told me that drafting only worked at high speeds such as in racecars. That you would never notice a wake at legal speeds......
A couple of years ago Mythbusters tested that. They proved that it does work, and you could save fuel by drafting a large truck at legal highway speeds. But in typical LawyerSpeak, they gave their obligatory "Do not try this at home".

Usually you think of the wake extended behind or to the sides of the truck, but as the geese demonstrated it also extends vertically.
 

stuart fields

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I was hauling some sky divers up in a Cessna 182. The three of them were not belted in and had their helmets in their hands and talking. I saw below me a descending B-52 that we were going to cross behind. We had more than adequate vertical separation (estimated 1,000+) and I "Knew" that any wake turbulence went down and not up. All of a sudden the 182 rolled rather violently an I quickly corrected with ailerons and a couple of seconds later it rolled violently the other direction. When I got it straight, all the jumpers had helmets on and were crowding the door. They told me later that if I was going to fly that way they were jumping and didn't care what the terrain was like below. If that wasn't wake turbulence, then I don't know what it was. On another time we were climbing out and the jumper at the door hollered look at that. On the ground there was a big shadow and little shadow coming together. I look out and up thru the wind screen and was able to verify the B-52 gear was down and locked. He was coming down right over us in spite of the NOTAM about jumpers in the area. I was ready for some severe turbulence that never happened.
Stuart Fields
 

Aesquire

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A major player in the early hang glider days, Bob Wills, died filming a Jeep commercial when the helicopter used in the filming cut their turn short directly over his flight path on landing approach. Basically pounded him into the ground.

Years later in Italy Valley NY, I was wire man ( the fellow who stands in front of the hang glider, holding the lower nose wires, while the pilot gets ready, and then stabilizes the glider until the pilot has control, announces his intent to take off, then the wire man dives out of the way, quickly. Often with treacherous footing and occasionally with a safety line to keep from falling off the cliff ) when I heard the curious sound of multiple jet engines approaching. I called an abort for the pilots take off, then as the noise got louder & closer, told him to disconnect. ( actually, yelled "unhook & bail dude! NOW!" )

Suddenly a B-52 came around the bend in the valley, below ridge height, all 8 P&W's leaving a pall of smoke behind, at about 350-400 knots. I could see the trees thrashing behind it as the wake turbulence rolled down the valley like a Stadium Wave, only on a massive scale. I dropped to the ground and wrapped my arms around the glider's lower flying wires and when the wake hit felt like a squirrel being shaken by a dog the size of a semi truck. No serious injuries or damage, we pulled that glider off the takeoff ramp and did an inspection on all the gliders tossed about.

The forces involved in keeping tons of airplane in the air are seldom felt on the ground. The magnitude would astound most people.
 

bmcj

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The forces involved in keeping tons of airplane in the air are seldom felt on the ground. The magnitude would astound most people.
I used to go out to the end of the Runway at March Air Force Base and watch the jets (originally B-52's, and later C-17's and C-141's) fly low over my head as they landed. The wake would follow a few seconds later with a thrashing of the long grass and a loud 'ripping' sound in the air as if someone was ripping bed sheets right next to your head. In other words, the strength and gradient was strong enough that you could HEAR the riptide of the air by itself, without it blowing against any trees, grass, or structures.
 

BJC

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A major player in the early hang glider days, Bob Wills, died filming a Jeep commercial when the helicopter used in the filming cut their turn short directly over his flight path.
...

Bob's brother, and co-founder of Wills Wings, Dr. Chris Wills, still is active in sport aviation. He flies a Glasair Aviation Sportsman 2+2 that he built.

My limited HG experience was in one of their SST's.


BJC
 

Derswede

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In college my roommate (also an aero engineering major) told me that drafting only worked at high speeds such as in racecars. That you would never notice a wake at legal speeds. I laughed heartily. Then I realized he was serious. I expressed my disagreement in a less derisive manner. He refused to budge from his stance. I offered to take him for a drive so I could illustrate my statements. He declined. The disagreement popped up once or twice later that week but wasn't resolved. Another week went by and I was giving him a ride home for the weekend so I took the opportunity to tuck in behind a semi where the buffeting was strong and sat there for a while. When I pulled around it I said something like "glad to get out of that." A few miles later I found a pickup with a cap on it...as we came up behind it and felt light turbulence I said "not again" and moved on. The topic never came up again.
Heh...spend 10 minutes on a motorcycle behind a truck and you will start thinking about passing said truck at the highest rate of overtake possible..I have almost been blown off my bike (which is a big, heavy Triumph) by buffeting....I have also seen a hawk get sucked between two trucks when he left the side of the road, heading in the same direction...hawk unfortunately did not survive the moment.

Derswede
 

radfordc

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I witnessed a massive wake turbulence incident at Oshkosh a few years back. A Super G Connie was doing a low flyby on Runway 36. Behind the Connie was a Bonanza on final to 36. When the Bonanza flew into the Connie's wake it rolled past 90 degrees. The Bonanza recovered and immediately did a go around. I'm sure the pilot relives that moment still today.
 
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