In ground effect information needed...

[underfire]

Given the multitude of experience with different platforms, and the abilities to express ones experience on this forum, I am looking for some real world data on ground effect. Specifically, the AGL at which you can 'feel' the ac is in ground effect.

https://upload.wikimedia.org/wikipedia/commons/thumb/c/ce/A340_wake_turbulence_simulation.jpg/800px-A340_wake_turbulence_simulation.jpg

There is a multitude of scenarios, but looking for any and all experience that you drivers have had. (color is always appreciated) 388 would be fantastic, 747, 330..the ones you need to leave a little bit extra space behind on ARR.

I am looking for the aircraft type, landing weight, flap settings, and winds...I know, quite a bit, but generalities are fine. You can also PM if you like.

Thanks for any and all information! :ok:

[safelife]

About half the wing span.

[eckhard]

On the 747-400, ground effect became noticeable below about 200ft on the approach.

On the 787 it seems to be noticeable below about 100ft.

737 and A320; no real effect that I remember.

[rigpiggy]

From my recollection comes into play within about 1 wingspan of ground

[underfire]

Thanks for the replies...

Does a strong headwind and/or more flaps influence the effect?

Eckhard, the 738 seems to be very slick, and it doesnt look like there is an appreciable effect...while the heavies, seem to want to float there, especially looking at the FAS of the B748/A388, looks like you have to push them down or they would keep gliding.

[misd-agin]

Really low, in ground effect, the elevators would buzz from the prop wash hitting the water. That is one time where the impact of being in ground effect can be noticed. Also for a given power setting the indicated airspeed would go up about 10 (???) KIAS when you're close to achieving zero ground effect. ;-)

With jets the buzzing in the elevators is not present.

[FullWings]

777 I’d say below 50RA for noticeable ground effect, in that the flight path is starting to change without control input. It can be difficult to separate this effect from low-level wind gradient sometimes.

[eckhard]

Eckhard, the 738 seems to be very slick, and it doesnt look like there is an appreciable effect...while the heavies, seem to want to float there, especially looking at the FAS of the B748/A388, looks like you have to push them down or they would keep gliding.

Underfire,
I remember a training video which showed the PFD of a 747-400 sim being manually flown down the ILS with manual thrust. Of course, being a sim, everything was 'perfect'. At about 400ft the pilot let go of the controls and the thrust levers. The aircraft continued on the GS until about 200ft when the VS started to reduce slightly and the GS diamond began to drop. I think the aircraft crossed the threshold at about 120ft.

The training point was that yes, you have to keep 'pushing it down' to maintain the GS.

As far as strong winds and different flap settings are concerned, I don't remember any noticeable difference.

[A Squared]

I remember a training video which showed the PFD of a 747-400 sim being manually flown down the ILS with manual thrust. Of course, being a sim, everything was 'perfect'. At about 400ft the pilot let go of the controls and the thrust levers. The aircraft continued on the GS until about 200ft when the VS started to reduce slightly and the GS diamond began to drop. I think the aircraft crossed the threshold at about 120ft.

I don't know whether or not this is an accurate representation of real life ground effect, perhaps it is. But generally, seeing something in a Sim doesn't necessarily make it so. A sim only does what it is programmed to do. It's programming may or may not accurately reflect more subtle, less quantified effects. Additionally, it may be intentionally programmed to exaggerate certain things for training purposes.

Just as a hypothetical example, a programmer who really sincerely believed in the downwind turn myth, could program that effect into a simulator, then you would be able to "prove" the downwind turn effect in the sim.

[eckhard]

Absolutely; good point!

[underfire]

I concur with a sim eval, but in reality, this effect is not well documented, so programming it....

The ground effect is still noticed at altitude on final, so there is an effect of the 300 tons of air compressed underneath you, with the AOA....that effect has to have some effect on landing...