View Full Version : A Question (Ground Effect)

04-20-2009, 08:16 PM
Is ground effect simulated in IL2?

04-20-2009, 08:16 PM
Is ground effect simulated in IL2?

04-20-2009, 08:38 PM
Sometimes landing and taking off one would think it is there.I would have to say no,Because if you had ground effect,then the programmer would have included the nasty vortex

04-20-2009, 08:43 PM
It doesn't seem to be.

Considering we are mainly flying low wing monoplanes you would expect it to be quite pronounced if it was modelled.

04-20-2009, 08:58 PM
Just now I did a search for information about it and saw this in the 4.02 patch Readme:

Flight Model

- adjusted ground effect *
- adjusted gyro effect *

So ground effect must have been included in the sim. But can it be used to increase an aircraft's top speed at gound level? Anyone tested it?

04-21-2009, 02:23 AM
Ground effect is the "cushion" of air between the ground and the wings of the plane.

It's less pronounced with high wing planes like Cessna 150's because the wing is further away from the ground than with low wing planes.

If anything ground effect, will result in the plane being able to fly slower, without stalling.

To go faster, i.e. with higher ground speed, you need thinner air and need to go higher.

04-21-2009, 02:34 AM
Ground effect is a lessening of induced drag, not an increase in lift. If you still have usable AOA then you can pitch up though.
In game ground effect may only happen over airstrips. That's been debated but I forget how that all ended up.

04-21-2009, 03:21 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jabout:
If anything ground effect, will result in the plane being able to fly slower, without stalling.

To go faster, i.e. with higher ground speed, you need thinner air and need to go higher. </div></BLOCKQUOTE>
As M_Guns has said, ground effect lessens induced drag, so I speculate that it may increase the top speed of an aircraft. I mean, for instance, if that's true, a bf109 flying above the sea will fly faster at an altitude of 5 metres than at an altitude of 15 metres.

04-21-2009, 04:44 AM
I think its modeled. A few times I have been able to stay airborne in ground effect when my engine has been producing minium power due to damage.
However now when u mentioned it, it was waaaaay back, probably 4-5 years ago... I rememember it clearly tho with the IL-2, in a specific patch, u could get airborne but u couldnt climb higher than a few meter.
A general rule is that the ground effect area is roughly equal to half your wingspan..
Saying that, a 747 has LOADS of groundeffect while our fighters dont have so much of it...

04-21-2009, 08:02 AM
You're right (tho' you probably knew that already http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif), it does reduce the vortices and the induced drag, very interesting.

04-21-2009, 01:09 PM
Try landing a B-17 (any model) with full flaps...

yes there is ground effect...at least somewhat

04-21-2009, 04:19 PM
Same goes for the H8K "Emily".

It will go on and on and on if you have the "landing flaps" deployed.

04-21-2009, 04:57 PM
The Tempest seems to balloon if you are'nt careful.

04-21-2009, 04:57 PM
Your top speed won't go up by much at all. Induced drag is very small at high speed with low AOA.
Ground effect does not reduce parasitic drag, at least from all I've read.

Here is John Denker's See How It Flies site. He is well qualified in aero to put it lightly. (http://www.av8n.com/how/)

Some things to expect IRL:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">When you are flying in ground effect, you are influenced by the mirror image of your bound vortex. Specifically, the flow circulating around the mirror-image bound vortex will reduce the airflow over your wing. I call this a pseudo-tailwind.17

Operationally, this means that for any given angle of attack, you need a higher true airspeed to support the weight of the airplane. This in turn means that a low-wing airplane will need a longer runway than the corresponding high-wing airplane, other things being equal. It also means – in theory – that there are tradeoffs involved during a soft-field takeoff: you want to be sufficiently deep in ground effect to reduce induced drag, but not so deep that your speeds are unduly increased. In practice, though, feel free to fly as low as you want during a soft-field takeoff, since in an ordinary-shaped airplane the bad effect of the reflected bound vortex (greater speed) never outweighs the good effect of the reflected trailing vortices (lesser drag).

As a less-precise way of saying things, you could say that to compensate for ground effect, any given true airspeed, you need more coefficient of lift. This explains why all airplanes – some more so than others – exhibit “squirrely” behavior when flying near the ground, including:

* Immediately after liftoff, the airplane may seem to leap up a few feet, as you climb out of the pseudo-tailwind. This is generally a good thing, because when you become airborne you generally want to stay airborne.
* Conversely, on landing, the airplane may seem to drop suddenly, as the pseudo-tailwind takes effect. This is unhelpful, but it’s not really a big problem once you learn to anticipate it. It does mean that practicing flaring at altitude (as discussed in section 12.11.3) will never entirely prepare you for real landings.
* The wing and the tail will be influenced by ground effect to different degrees. (This is particularly pronounced if your airplane has a low wing and a high T-tail, but no airplane is entirely immune.) That means that when you enter or exit ground effect, there will be squirrely pitch-trim changes ... in addition to the effects mentioned in the previous items. Just to rub salt in the wound, the behavior will be different from flight to flight, depending on how the aircraft is loaded, i.e. depending on whether the center of mass is near the forward limit or the aft limit.

During landing, ground effect is a lose/lose/lose proposition. You regret greater speed, you regret lesser drag, and you regret squirrely handling. </div></BLOCKQUOTE>

04-22-2009, 06:20 PM
I've picked this up in landing my fav FW..
If I come in at the right height fast and level (rare occasions).. very little effect.

On less perfect occasions I find myself flaring/rotating a lot more than usual with a lot of rudder correction. Only for a split second but enough to be corrected for.

04-24-2009, 04:37 AM
Thanks guys for your comments.