Better not hiccup....

[earl1937]

I think there is confusion about what is meant by "ground effect".  If we are talking about aeroplanes it is mainly the reduction of induced drag. If we are talking about ground effect vehicles then we are probably talking about stagnation of air under the vehicle providing a high pressure cushion. I still don't think the reflections in the video are plausible.

I know there is a lot scientific information posted here and on u-tube, but, Go to Crystal River, Fla, which has 2 runways, 1 grass and 1 paved. Wait until late in day, with not enough wind to make any difference and land on the grass runway and then on the paved runway. First thing you will notice is how much longer, after all power off, the aircraft will float down the runway on paved surface than it does on grass.
Now if all the explanations of ground effect were accurate, there would be no difference in the paved and unpaved runway, but there is a difference, so I am going to stick with reflected heat or thermals from paved surface, vs unpaved surface as the cause of so called ground effect. At any rate, not flying anything heavy anymore, I don't have to worry about "ground effect" anymore.

[B3YT]

For ground effect , look up the Blackburn Buccaneer . That plane could be flown hands free at 25ft from the ground and never nose down into the ground due to ground effect . An extremely stable bomber / attack aircraft that flew from the 1960's to the mid 1990's with the RAF and NFAA . 

[earl1937]

For ground effect , look up the Blackburn Buccaneer . That plane could be flown hands free at 25ft from the ground and never nose down into the ground due to ground effect . An extremely stable bomber / attack aircraft that flew from the 1960's to the mid 1990's with the RAF and NFAA . 

I don't doubt your comment about the hands off at 25 feet, but that is not low enough to be in ground effect! By that logic, a B-36 peace maker, with a 230 foot wing span, could encounter ground effect somewhere around 75 feet. Someone, somewhere, computed the height above ground level to be in ground effect, based on the length of the wing! I can't find it right now, but will cont' looking. Again, I personally don't think that is accurate for a number of reasons, I still say that so called ground effect is based on heat thermals from the runway. Again, I invite anyone to land on pavement, then turn around and land, same direction, in the grass! You are going to see there is a difference. When this thread started, I was curious, so I called a friend of mine, J. Wingo, a 20 year veteran in the outback of Northern Canada, who flies a Maule, hauling hunters and fisherman into the outback. He says that he carries power, just above a stall when landing on a sand bar, chops throttle just as he gets over dry land and it lands immediately. So if there was such a thing as true ground effect, why wouldn't the Maule float a few feet prior to touching down. He is an old timer and says that is hog wash! Jay married my sister-in-laws, sisters, daughter.

[colmbo]

ET, heated air rising off the runway isn't ground effect.  Granted that it will cause you to float....it's rising air....same as hitting a thermal.

Ground effect has the most effect within 1/2 wingspan of the surface.

Your buddy is dragging in using power, of course it lands when he pulls the power off.  It doesn't float because he is nailing the approach speed.  If he really wants to test it tell him to go out a fly down the runway as slowly as he possibly can just inches above the surface and have him take note of the amount of power needed to maintain level flight at that speed.  Then tell him to do the same thing more than a wingspan above the ground.  If it is a measurable amount he'll note that it takes a bit less power to make that super low pass than it does for the higher pass due to the reduced drag resulting from ground effect. 

[earl1937]

ET, heated air rising off the runway isn't ground effect.  Granted that it will cause you to float....it's rising air....same as hitting a thermal.

Ground effect has the most effect within 1/2 wingspan of the surface.

Your buddy is dragging in using power, of course it lands when he pulls the power off.  It doesn't float because he is nailing the approach speed.  If he really wants to test it tell him to go out a fly down the runway as slowly as he possibly can just inches above the surface and have him take note of the amount of power needed to maintain level flight at that speed.  Then tell him to do the same thing more than a wingspan above the ground.  If it is a measurable amount he'll note that it takes a bit less power to make that super low pass than it does for the higher pass due to the reduced drag resulting from ground effect. 

Hey friend, you and I don't need to debate this, because you can't convince me or a lot of other pilots in this world that ground effect exists! Take your aircraft, land on grass and then pavement, should be the same, right? There are just some things about aviation that the so called experts have never really pinned down. All these explanations that you and some others are reading are theories, yet to be proved.
Just like some say the reason the aircraft turns is the high wing produces more lift that the low wing, hence it turns. Wind tunnel tests have shown time and time again that the whole wing is producing "resultant" lift, my term, and lift is what pulls the aircraft around in the turn. If you are slipping or skidding in the turn, yes, one wing will produce more lift than the other one, but if it is a level, constant altitude turn, both wings are producing the same amount of lift. Think about it, if it was true about the high wing producing more lift, the aircraft would just cont' on until inverted. Now, you and I both know that a lot of aircraft can be set up into a turn and with out touching anything, will cont' that bank angle and turn, unless some outside force acts on it, i.e., controls, wind, surface turbulence. If you turned it loose during the turn, it would start to continue banking until inverted. Don't mean to be stubborn, but until someone can show me some facts, gonna stay with what I have learned in 66 years of flying with no accidents!

[Golfer]

Ground effect doesn't exist but being "on the step" does?

I've flown plenty from grass runways and I've never noticed the phenomenon you're talking about. If anything I've floated a little more in the grass surfaces for want of a slightly smoother touchdown whereas if I need to plant it on pavement I'm not worried about turf because I'm going to have a pretty uniform surface I'm not going to compress with an airplane.

[earl1937]

Ground effect doesn't exist but being "on the step" does?

I've flown plenty from grass runways and I've never noticed the phenomenon you're talking about. If anything I've floated a little more in the grass surfaces for want of a slightly smoother touchdown whereas if I need to plant it on pavement I'm not worried about turf because I'm going to have a pretty uniform surface I'm not going to compress with an airplane.

Being "on step" is not some theory. All getting an aircraft on step, as it is called, is exceeding the normal cruise speed by a few knots and is usually accomplished by climbing slightly higher than intended cruising altitude, set up a slight descending attitude until back down to the altitude you intend to cruise at. What you are actually doing by doing this step, is changing slightly the AOA during cruise, the desired AOA is slightly a negative AOA. But, as with a lot of other things in aerodynamics of flight, there are outside factors which will effect "step", such as into the wind, down wind, turbulence, snow, rain, ice pellets, so the conditions have to be right to actually attain "on step" and maintain "on step". Now, basically we are talking about aircraft without a "flight director", as with those aircraft, if you dial up 250knots, that's what it is going to fly at. The aircraft which we are talking about are manually flown aircraft. Now that is not to say that a aircraft with a auto pilot, which has a altitude hold feature, cannot be set up "on step" because it can, you just have to engage said auto pilot feature after you obtain the on step speed for that aircraft. But, again, there are several outside factors which can disturb the on step speed. The old Beechcraft Bonanza, with a "V' tail confg is a good example. It is easy to get on step, but first turbulence and the thing starts "fish tailing" and your step advantage goes away.

[Lusche]

When grond effect does not exist, how do ground effect vehicles work?  

[earl1937]

When grond effect does not exist, how do ground effect vehicles work?  

(Image removed from quote.)

That, sir is a whole different concept in which the aircraft works! Its producing power to hold it above the ground  and so called ground effect. With out equipment and engines to provide downward thrust, it would depend on forward speed to maintain that low of altitude. The bottom line is just this: as long as lift overcomes gravity, it will stay in the air, but with no thrust to provide forward speed to develop lift, then weight overcomes gravity and down she comes. That is another reason I keep saying "ground effect" is an old timers tale. Once forward speed, which is producing the lift of the wing, is reduced to the point of weight, i.e., gravity, overcoming the lift factor, the aircraft is going to land or crash, depending on where you are when you run out of airspeed and altitude at the same time.

[Lusche]

That, sir is a whole different concept in which the aircraft works! Its producing power to hold it above the ground  and so called ground effect. With out equipment and engines to provide downward thrust, it would depend on forward speed to maintain that low of altitude.

What downward thrust? For example the Lun depicted above has no other thrusters than the 8 forward mounted, conventional turbojets


The A-90



has two PAR turbofans vectoring their thrust below the wings for takeoff, but are shut down after that and the Ekranoplan is only flying in ground effect, driven by it's huge turboprop. No additional downward thrust at all.

[Golfer]

Being "on step" is not some theory. All getting an aircraft on step, as it is called, is exceeding the normal cruise speed by a few knots and is usually accomplished by climbing slightly higher than intended cruising altitude, set up a slight descending attitude until back down to the altitude you intend to cruise at. What you are actually doing by doing this step, is changing slightly the AOA during cruise, the desired AOA is slightly a negative AOA. But, as with a lot of other things in aerodynamics of flight, there are outside factors which will effect "step", such as into the wind, down wind, turbulence, snow, rain, ice pellets, so the conditions have to be right to actually attain "on step" and maintain "on step". Now, basically we are talking about aircraft without a "flight director", as with those aircraft, if you dial up 250knots, that's what it is going to fly at. The aircraft which we are talking about are manually flown aircraft. Now that is not to say that a aircraft with a auto pilot, which has a altitude hold feature, cannot be set up "on step" because it can, you just have to engage said auto pilot feature after you obtain the on step speed for that aircraft. But, again, there are several outside factors which can disturb the on step speed. The old Beechcraft Bonanza, with a "V' tail confg is a good example. It is easy to get on step, but first turbulence and the thing starts "fish tailing" and your step advantage goes away.

Not buying.  Are you aware of the dangers of the downwind turn as well?

[earl1937]

Not buying.  Are you aware of the dangers of the downwind turn as well?

Depends on your airspeed where or not the down wind turn is of any danger to the aircraft!

[earl1937]

What downward thrust? For example the Lun depicted above has no other thrusters than the 8 forward mounted, conventional turbojets


The A-90

(Image removed from quote.)

has two PAR turbofans vectoring their thrust below the wings for takeoff, but are shut down after that and the Ekranoplan is only flying in ground effect, driven by it's huge turboprop. No additional downward thrust at all.

But it is producing enough thrust to over come weight, i.e., gravity, so there fore it will fly, as long as lift equals drag and weight sir!

[DaveBB]

For a non-aviator such as myself, let's see if I understand this right.  Vortices are produced by the wing.  These create drag by some mechanism (are they creating low pressure areas behind the wing, actually try to pull the wing in the opposite direction of flight?).  When low to the ground, these vortices can't form, and by whatever mechanism that they use to normally create drag cannot occur?

[earl1937]

For a non-aviator such as myself, let's see if I understand this right.  Vortices are produced by the wing.  These create drag by some mechanism (are they creating low pressure areas behind the wing, actually try to pull the wing in the opposite direction of flight?).  When low to the ground, these vortices can't form, and by whatever mechanism that they use to normally create drag cannot occur?

Vortices's are created by the Wing Tips, primarily by the shape of the wing tip. Some aircraft produce more vortices's than others and the heavy the aircraft, the more pronounced vortices's are present. The vortices's are what creates the "wake" turbulence and have been responsible for several accidents. Vortices's are no problem on landing, if you plan your touch down beyond where the aircraft in front of you touched down. It is best practice to wait on takeoff for a couple or 3 minutes to give the vortices's time  to dissipate or the wind move them to the side of the runway prior to you taking off. In FAA tests of vortices's, they settle behind the generating aircraft and as long as you climb above the aircraft in front of you, you shouldn't encounter any problem. Don't let ATC rush you into to taking off, until you are satisfied that wake turbulence will be no problem to you.
Vortices's per sae do not produce any drag, that is created by the shape of the wing itself. Any wing which produces lift, also produces drag, but again, the shape of the wing will dictate how much drag is created.
For example, in this game, the B-17G has a "Hersey Bar" type wing, which is designed to create a lot of lift, but it also creates a lot of drag, hence the reason for slow speed of the aircraft in all flight realms. In the other end of the spectrum, look at the LA-7 wing, which is designed for speed and because of the shape does not produce much drag.