'Ground Effects' question

[greybeard 0]

I've heard the term 'Ground Effects' in relation to aviation, particularly helos and aircraft landings.

Who can add info regarding canopy landing and of course the inevitable ws attempts.

I've heard stories forever about the chuteless freefaller who dived for speed, then swooped at the last moment, for lift and survived.

Roller blades on my walker, no brakes,

Greybeard

[medusa 0]

yess there is ground effect that can affect landing of anything planes, wing suits canopies etc....
the aircraft pilots are the only ones ho could really answer you question.

about the chuteless ws who dived for speed swoop and survive thats bull #$#@. even if you dive the suit and then swoop you can kill all your vertical speed for a split of second you will get a little sweet point with no margin for error, but you still going 100 M/ph forward speed. do the math.

Medusa

Get Killed or Die Trying!
Patent pending ATFK15456

[VectorBoy 0]

There is a little phenom in fixed wing aviation flight that occurs when a wing is closer to the ground than its own span. There is a net gain in lift as the high pressure air on the bottom of the lifting surfaces can not so readily migrate to the upper low pressure side due to interference from the ground.

I'm not sure how much this applies directly to a rotordisc but its not to be confused with rotorcrafts "translational lift" gained from forward momentum close to the ground before gaining altitude. This technique is used to keep the craft outside of the cone of death.

[vesatoro 0]

In fact the ground effect comes from reducing induced drag by interaction of ground surface and wing tip vortex. The ground effect begins (10% less induced drag) at about altitude of half wingspan. So with a wingsuit it would be less than one meter (3ft). And in case of good tracking at about 30cm (1ft). So you have to be quite accurate in the approach to use it

"Fear is the path to the Dark side"
(Master Yoda)

[Pendragon 1]

Just wanted to add to Vesa's reply that the reason why there are wing tip vortices is because air spills over the edge of the wing from the top and sets up a little eddy. This eddy (the same which produces wake turblulence) makes the wing less efficient in flight. When close to the ground, the eddy cannot form (insufficent space for the air to move and set up the vortex) so the induced drag is mitigated and wing performance is increased.

The phenomenon is quite detectable on a landing approach even by a hang glider.

Hope this helps!

Richard

--
BASE #1182
Muff #3573
PFI #52; UK WSI #13

[freakbrother 0]

Since airplane effects have already been described, I'll just add that a similar effect is found in helos within about 1 rotor diameter of the ground.

In marginal situations (hevy load, high density altitude) an aircraft may be able to take off but not climb out of ground effect. Has caused a number of accidents over the years.

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www.freak-brother.com

[larsrulz 0]

The phenomenon with helos is completely different than ground effect for aircraft, as hovering lift is not created in the same way that an aircraft, and hence canopies and wingsuits, create lift, but they do experience some aerodynamic effect when near the ground.

That said, given the very small wing area of a wingsuit, i.e. high wingloading, the induced drag will be considerably high, so if a flier could make use of the ground effect, then it could have a very large impact on total drag.

All that said, I know nothing about wingsuits, just aerodynamics.

I got a strong urge to fly, but I got no where to fly to. -PF

[freakbrother 0]

Quote

The phenomenon with helos is completely different than ground effect for aircraft, as hovering lift is not created in the same way that an aircraft, and hence canopies and wingsuits, create lift,.

How is the movement of an airfoil through the air as a helo rotor blade different from the movement of an airfoil through the air as a wing?

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www.freak-brother.com

[DBCOOPER 1]

Increased blade efficiency during in ground effect hover is due to two phenomena.1. Reduction in the velocity of the induced airflow.This results in less induced drag and a more vertical lift vector.The ground causes the static pressure under the rotor system to increase.2. There is also a reduction in the size of the blade tip vortices providing for more lift from the rotor system.This is caused by the reduction of the velocity of the induced flow and the outward movement of the air from under the rotor system.The opposite can happen out of ground effect where the velocity of the induced airflow continues to increase and the rotor tip vortex continues to grow reducing the total lift of the rotor system causing settling with power.You would probably have a better chance trying to land a wing suit on one of those outdoor wind tunnel thingies.

Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

[freakbrother 0]

Quote

Increased blade efficiency during in ground effect hover is due to two phenomena.1. Reduction in the velocity of the induced airflow.This results in less induced drag and a more vertical lift vector.The ground causes the static pressure under the rotor system to increase.2. There is also a reduction in the size of the blade tip vortices providing for more lift from the rotor system.This is caused by the reduction of the velocity of the induced flow and the outward movement of the air from under the rotor system.The opposite can happen out of ground effect where the velocity of the induced airflow continues to increase and the rotor tip vortex continues to grow reducing the total lift of the rotor system causing settling with power.You would probably have a better chance trying to land a wing suit on one of those outdoor wind tunnel thingies.

Sure, but how is the mechanics of lift production different (as was claimed) between a rotor blade and a wing? Both impart a downward momentum to the airflow resulting (by Newton) in lift. Both have airfoils, both have tip vortices, both have inflow, the pressure distribution over both airfoils agrees with Bernoulli's theorem, etc.

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www.freak-brother.com

[LBurna 0]

Dude, listen, someone already landed chuteless in 2007. he swore like a drunken sailor to the guy that owns the world book of records and stated,(i dont want to be in your book) he didnt want anyone to be influenced to do it, and for anyone to lose there loved ones trying to repeat this landing. it accured in pasidina california, the place where the park at the waters edge was bulldozed to keep others whom witnessed it to aviod anyone duplicating the jump. the guys name was LJ from south carolina. he weighed only 134lbs and landed it, doing 80mph when he touched down smoked rolled off his shoes just like an airplane when it lands....so pls dont tell me it cant be done. and pls tell jeb or jeff whatever fake name he goes by now that he lost the bet he pulled his chute first ....haha. it was the first time this fellow even jumped from a plane ....more lolz. and tell every one from red bull sponsered jumpers sorry for rubbing it in so much.........jeb pls enclude in your chuteless jump YouTube vids that u will be landing on a bunch of boxes.....wasted 30 mins of my life ....any time any where jeb. if you have the gear,the plane and good landing spot any time you grow a real pair call me. .... oh and again thnx jeb, for allowing me to borrow you damaged winged suit and i still landed it lolz. you know the black and bright green one you wore when you attempted the landing and tore the webbing between the legs, when landing attempt failed and you got nocked out. but still thnx. and 1 more thing, JUMP FLY LAND is mine dude stop coping me. bro really! so in short attention all jumpers if you want to see it done. then you can foot the bill. I will also need just a few items. A plane,place to land and a suit,and not the new rigs either. and one more thing the most important thing a can of non-stick cooking spray for my shoes.i know it sounds crazy but it works. jeb stated to pull back when i did i realized i pulled back to soon, i had to drop over 14ft to land. when landing turn around backwards to land(NOT) forward if you get to much downward weight on you shoe tread, you might face plant not a good thing when your approach speed was over 125mph landing speed 75 to 80+ mph.and dont listen to jeb or jeff, 125ft is to soon to pull back wait 2 secs longer then pull back. im the only man in the world who has done this so....... and im the only person in the history of man kind to do it! landed downhill at 80 mph on a 4ft wide blacktop sidewalk.....remeber turn around lean forward knees bent slightly.....do not land forward. pull back at 100ft not 125ft. im the only person in the world with 3 whole sec's of chuteless winged suit landing experience. hehehehe! i wieghed in at a 134lbs 6ft tall. no chute,no gear just the suit.oh, i almost forgot originally we were only supposed to climb to 1800 ft they allowed me 1 time to jump at 2500 so i could do some free style flips n stuff. this is the one were i jump fly landed, to bad none else could say jump fly ....LANDED! huh jeb or is it jeff now oh well no matter. i did it nener nana boo boo big J. in your face baby. good thing im better at landing than typing...lolz

[murf62 0]

If you're going to come on here with a mad rant, it's a bit unfair expecting people to know about something that is not going to happen for another 2 years after the last post!

[LBurna 0]

srry didnt mean to rant i just found this forum full of everything awesome. for the record i never actually expected anything from anyone for any reason just stating the facts and simply issueing a challenge. though i warn everyone my post may be misplaced till i get a feel for the place till then pls watch urself while on the sidewalks