Flying Basics: How "Ground Effect" Affects Planes In DCS WORLD

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[@w33b3l]

I havnt noticed it in DCS much, but its actually something you have to be mindful of in Civilian aircraft. Low wings in XP11 for example. The TBM900 will want to just sit about 2 feet off the runway. While the caravan doesn't do it nearly as much. You notice it more in the A10C in DCS because of the lower landing speeds and huge wings. Fighters not so much.

[@Vampiresquid007]

thats because fighters can travel faster and the wake is just too far behind to hit the ground and reflect back to the jet which is already gone grim is flying too fast too. especiallly if ur faster than sound

[@w33b3l]

@@Vampiresquid007 plus even when you land most of those planes you touch down pretty hard.

[@LeoH3L1]

I think that on the F/A-18 the low pressure zone is below and ahead of the wing, which would interact with the pressure field around the wing, altering the lift distribution in the longitudinal axis between the wing and the ground, which would create a nose down torque, it's not so much you're being sucked in more that you're being rotated in.

[@czdaniel1]

Groom Lake Nevada _(about 3 mountains & valleys north-west of LasVegas)_ gives you several miles of exceptionally flat terrain. Plus there's a runways a couple miles long leading into the dry lake-bed

[@jethro_xd]

Hello Cap, my name is Jeff. I hold a commercial pilot's license single-engine multi-engine land instrument rated. There seems to be some confusion about ground effect. Ground effect is experienced within 1/2 the wings span above the ground. Ground effect does not increase the air speed. Ground effect allows the aircraft become airborne at a lower speed than would normally be required for flight. We use this for short feild take off. Get it up into ground effect, level off, the aircraft will accelerate quicker, there's no rolling resistance of The Wheels on the runway. The suck down thing, on some aircraft, tip vortices can kind of bounce off the ground and influence the tail or empennage if you prefer.What causes ground effect, that is a complex topic that is beyond the scope of KZbin comment section. There are some published papers that get into this, I get them on NASA's website however you need to be an aerodynamicist to really get it. Cool video though, all your videos are cool. Hope this helps.....

[@grimreapers]

Thanks Jethro

[@onurerdincler3107]

Im an aerospace engineering student ill try to explain the lower wingtip vortices bit simply. Imagine a 2d wing aka an airfoil, the air below the wing has more pressure so it creates a net upward force. Now make that wing 3d the high pressure air below the wing wants to meet with the lower pressure air on top of the wing. They usually meet at the trailing edge and everybody is happy. I say most of the time because at the part near the wingtips air has an easier way of meeting, going around the wingtip. So the air below the wing near the wingtip goes down out of the and back up again to meet with the lower pressure air. In ground effect the cant go down as freely because there ground underneath so all that air has to go the traditional way of meeting at the trailing edge thus reducing vortices and drag.

[@onurerdincler3107]

Think of the drag reduction like this the energy that would have been spent of creating wingtip vortices are now utilized in producing lift

[@datrandomguy3253]

This really helped me understand it. Thanks.

[@frogsshadow4189]

The vortices (plural for vortex) normally happens at the wing tips where the high pressure under the wing flows past the wing tips and on top of the wings. This causes the air to spiral around the wing tips and creates drag. (side note, this is why airliners have vertical wing tips, this reduces the vortices allowing them to fly more efficiently, though they have since learned that curving wings is even more efficient which is why we don't see as many vertical wing tips now.) When in ground effect you're basically riding on a cushion of air and the high pressure area extends a bit in front of the wings, reducing the vortices and decreasing drag. Typically fighters have smaller wings so they aren't as effected by ground effect though it is still there, it's a lot more noticable on bigger aircraft though. Though I don't know about why specifically but I think the mirage got sucked down because of the shape of the delta wing

[@koningwillie6839]

I feel like this video could have been 10 minutes instead of 45...

[@romakrelian]

The F-18 was the aircraft that rudely introduced me to the ground effect.

[@LeoH3L1]

All this is real world aviation related.... There are basically two ways of generating lift in normal flight for a given wing, either by the airspeed, or by the AoA, you can reduce one and increase the other and maintain the same lift, but in ground effect you introduce a third way, and that is compression between the wing and the ground, and this effect starts to kick in at about one wingspan and gets progressively stronger the lower you go. The vorticies are a product of induced lift, and induced lift is a product of angle of attack. The reason that the vorticies are a product of induced lift is that as you increase the AoA you're increasing the pressure differential between the top and bottom sides of the wing, and the air tries to move around the tip from the high pressure side to the low pressure side, the more AoA you have the bigger that pressure differential is and the stronger the vortex. If you can reduce the need for AoA, by keeping the airspeed the same and introducing ground effect you will get a reduction in induced drag and smaller vorticies.

[@vnyggi621]

What is meant by downwash in the beginning of the video? Or was that referring to helicopters

[@LeoH3L1]

@@vnyggi621 "Downwash" occurs in all aircraft strictly speaking, with helicopters it's more obvious the meaning, but at the trailing edge of a fixed wing you'll also get downwash (and upwash at the leading edge). The concepts of upwash and downwash are critical to the "circulation" theory of lift.

[@Maeyanie]

There's a number of elements in the physics, but probably the biggest one is that the airplane's wing is pushing down the air beneath it to generate lift. Normally that air can just move downwards no problem, but (little-known fact) air doesn't move well through the ground. So when you're very low altitude (lower than one wing chord... the span does matter for some parts, but overall is less important than the chord for ground effect), the air being pushed down by your wing smacks into the ground and slows down somewhat. The air above it keeps moving downwards, though, so you end up with the air compressing. Because of this, you end up with higher-than-normal pressure air under your wing, and normal-pressure air above your wing, so it pushes your plane up more than usual, generating more lift. This is very simplified, but you asked for the layman's version, so there it is. When you think about it, it actually does make a lot of sense. Edit: It's possible the pitch-down effect in the Mirage comes from the fact that the delta wing ends right at the back of the plane, and the closer to the back of the wing, the greater the compression effect. It does actually make sense that it would try to pitch you forward there... so I think that's actually some good work on Razbam's part. Edit 2: You should feel the lift more at lower speeds rather than higher ones, since you have higher AoA then. But the wingtip vortex shortening should work better at higher speeds. So, bit of both. Edit 3: The effects should also be stronger on the low-wing planes than the high-wing planes, which did seem to be the case in the results. I'm not sure why the speeds were as inconsistent as they were, but I'm guessing it's a lack of knowledge on my part rather than implementation on their part... though admittedly I'm pretty sure high-speed flight at 4 feet off the ground wasn't part of the standard testing routine.

[@Relax2437]

Cool video! But I would redo the test. Because ground-effect is most noticeable during landings, when an airplane is in land-config & slow. A good test is ie. Nellis AFB (long rwy), fly at Vref, & don't touch the power, sink to ground-effect height & see what happens. I would also think that ED & 3:rd p. concentrated more on ground-effect FM in this circumstances (landings).

[@grimreapers]

Copy wilco

[@codyparsons5986]

One of the reasons for ground effect reducing the size of the wing tip vortexes is a lot of the air that is trying to expand out and curve around the under side of the wing to the low pressure on top hits the ground first before it can do so thus reducing the wing tip vortex and reducing induced drag.

[@terryboyer1342]

Cap, here's a few things you may find interesting. The Soviets were big into this. en.wikipedia.org/wiki/Ground-effect_vehicle www.theregister.co.uk/2017/04/06/ekranoplan_returns/ And I don't know how accurate they are but I've read several stories about the US flying missions against the Japanese with P-38s flying low to use ground effect. It increased their range by several hundred miles catching the Japanese completely off guard as they didn't think they had the legs to reach them.

[@grimreapers]

thx

[@ukke]

Also it depends on wing design. Delta wings, ekranoplan or tandem wings will have more ground.

[@firemedicjm911]

Great video! "Ground effect is maximized in calm wind conditions and over a smooth and level hard surface. The effect over grass, an uneven surface and sometimes over water is likely to be much less. Not surprisingly, fixed wing aircraft with low wing fuselage attachment receive maximum ground effect."

[@Darrylx444]

Hi Cap. I like your research videos very much. Suggestion: Try the same experiment again, but this time at typical landing speeds. Induced drag is a much larger (i.e. more noticable) component of total drag at lower speeds, and thus the results should be much more definitive (and relevant).

[@grimreapers]

thx

[@Madeyes6]

The Buccaneer was renowned for its ground effect. Allegedly you couldn’t push the stick down to make it crash. There was a really strong cushion of air that pushed it up.

[@grimreapers]

awesome thx

[@dannsgamingfails8899]

At the red flag event in “77 the Buccaneers flew so low that the American SAM operators couldn’t track the aircraft. They had to look for dust trails to find the British pilots. Apparently after the first week someone was summoned to the Pentagon to explain how an aircraft with a top speed of 580kts could not be shot down by the Americans. Thing is 580kts with no after burners is plenty at 30ft.

[@benpoffenberger7173]

many suggestions to try in landing config. here. instead, if you want to really test the models for this effect, try takeoff with no flaps at lightest weight. Use minimum throttle. At the right balance, you will get the airplane airborne at some minimum speed and it won't fly higher than about 1/2 wingspan above runway without adding more power (if the models are true to life that is). You may need a really long runway... ;-} Thanks for being curious, I think that is fun stuff! Blue Skies! Ben

[@liquidbeaf]

"it sucked me down..." this ground effect thing sounds amazing

[@orionmec]

Has I understand physics.... the "vortices" created at the tip of a wing or rotor in itself is "drag".... more of a voticy or "rotation" of air flow means more drag. Therefore if the voticy is reduced either by shape or speed you will have more lift in respect to the speed by the very nature of 'lift' itself. So, this really helped me as I have been having a problem landing. Some was because of my stick adjustment but I neglected to concider this. Much to learn in DCS!

[@TealJosh]

Ground effect is quite annoying when landing too fast with too shallow AoA. My airspeed just wouldn't go down and real fast half of the runway has gone past. Two options, either slam the aircraft into ground or go around.

[@saintmobius5348]

Drop throttle and retract flaps 5 degrees and you'll mitigate ground effect enough to land.

[@simonwootten5821]

As always, great flying... but now with the addition of a new vocabulary.....suckage!!! Brilliant. Enjoyed this, thank you.

[@Hairysteed]

And when the suckage gets paraticularly serious it's called suckkake

[@grimreapers]

lol

[@Struktualnyj]

Also 26:23

[@cmibm6022]

When you are sucked down, it is due to the venturi effect. Try to hold 2 sheets of paper vertical, say 30mm apart. Then blow (with your mouth) in between them - and voila - they will move towards each other. The same principle as used in a carburettor, where you have the venturi pipe creating an under pressure to suck in the gasoline.The same effect can suck down huge ships several feet and must be taken into account when passing shallow waters. You probably should have had a setting with no waves. I imagine that the waves will have an effect on the ground effect.

[@grimreapers]

Welcome back Cam. You've missed some cool shit.

[@cmibm6022]

Thanks! I will try to catch up, but with your production rate, it will be quite hard :-)

[@arvadawelder]

The best way to test ground effect is due landing configuration flops gear at about 2000 ft and stall it. Then do the same thing coming in to land but do not touch runway with rain gear and try to stall just above the runway the speed should be different.

[@crazzy8873]

awesome info on the last few cap getting my pc today yay ive been watching GR utubes vids have to get a good joystick so im going to attemt this i used to fly the sims all the time but like you i got out of it for a bit its cool to see how they have been improved

[@adamsmith5151]

If you can afford it, get a VR headset. You won’t regret it! A TrackIR at the least.

[@crazzy8873]

@@adamsmith5151 k cool I'm want to get that two

[@Staletaters]

Bernoulli's principle, as velocity of a fluid increases, pressure of the fluid decreases, this principle is how airfoil generate lift.

[@grimreapers]

thx

[@ozgurkaratas6450]

Not to be confused with "wing in ground effect" which might happen with large low wings coming to flare abruptly n the air pressed by the attack area cushions the wing slightly for a bit. There are actual hovering crafts designed over this phenomenon.

[@grimreapers]

Copy

[@MrPnhartley]

Leon Hostad got it exactly right. The Russian Ekranoplan/Caspian Sea Monster ‘flew’ largely because of this effect. The extra lift and subsequent control input needed to ‘hold it down’ results in extra control surface drag although the wing are reduced drag due to less AoA. Different planes balance out differently.

[@LeoH3L1]

Thanks :)

[@czdaniel1]

*Woe!! Careful there with these highly technical aeronautic terms like **_Pushy-Upy-ness!!_*

[@grimreapers]

lol

[@spacemannich6107]

I learned to fly in a piper Cherokee. The ground effect was insane. It was basically a wall once you hit 5 feet with engine at idle you floated down the runway forever. Does a stalled wing benefit from ground effect? My guess would be no because there is very little induced drag on a stalled wing

[@timmunroe4873]

lol put a mower behind that cat lol wow record there I would say excellent Cap!

[@Bagheera2]

I mentally picture it at this your wings are forcing air down, kinda like a helicopter down wash. Close to the ground, the downward has a "ballooning" effect pushing your aircraft up. Less lift is needed by the wings. Your wings working less induce less drag. All aircraft, rotors and propellers have vorticies at the tip due to the wings function. Higher pressure on the bottom of the wings, rotors or propellers wants to get to the lower pressure at the top. This occurs at the tips of the wings and creates vortexes. This causes drag in all things that fly, and is the price you pay for lift. This is why airliners have those wingtip "winglets" to help reduce that.

[@Bagheera2]

Il2 1946 I believe has this modeled because some aircraft REALLY balloon on landing.

[@hba8103]

You should try to see the effect while in landing configuration. This is when the effect comes most into play. Not at straight and level flight.

[@grimreapers]

wilco

[@gosajd1736]

Cap, you need a new graphics card. Intresting video tho. Keep em coming :)

[@gketchup777]

Is it possible that on those planes that have suction they are actually missing a negative sign from the ground effect acceleration formula? I mean they should definitely push up and not down...

[@grimreapers]

Sounds plausible

[@indyjons321]

Ground effect, basically a cushion of air. But try lower speeds maybe?

[@grimreapers]

Roger every is saying that

[@MattVarnish1103]

I thought it was Chuck Yeager who first sussed it all out when he literally couldnt get his new jet any lower to the ground (P-80 so straight wing jet)

[@MattVarnish1103]

And I think the straight wing jets experience the ground effect differently than delta shapes (Mirage, F14, mig-29, etc)

[@alexanderbeck5998]

Could it be that your tail hit the water while your nose was in the air in the M2000?

[@williamstilgoe61]

Hi Cap, love your videos. The basic thing about ground effect is that it is a cushion of air, like a hovercraft without the skirt. It seems to be all about being at just the right speed, height and angle of attack. The Russians made some awesome craft that could only fly with ground effect. Check out the Caspian Sea Monster it’s awesome, kzbin.info/www/bejne/rmOVn4l8iclrpKs.

[@grimreapers]

thx

[@matk4731]

My brain herts now. 👍🏻👍🏻🙃🙃

[@timmunroe4873]

could it be you get more suction over the water due to fluid dynamics. Meaning the water can actually get sucked upwards were as over the ground witch is denser does not move upward!? just a thought I'm no expert on this though.

[@Synystr7]

Your mirage turns into a diffuser at 4tf lol

[@bourrinopathe764]

Thanks for those tests. I was surprised the Hornet would get sucked down instead of being more controllable in ground effect. Apparently this happens (also in inverted flight) passing the top of a hill or flying over the deck of a carrier. Here's a neat video about the ground effect techniques and also showcasing a Nanchang CJ-6 (aka almost a Yak-52): kzbin.info/www/bejne/gYHEcneNlNp8f7c

[@Etyneo1984]

Wait...wait...you're flying that low in the F14B and Jester hasn't punched out yet? Did he take his Brave Pills today?

[@grimreapers]

I removed his ejection privileges

[@czdaniel1]

*@**40:25** -- SCREENSHOTS --**40:25*

[@cmskinner3682]

Ground effects. I thought we we racing for a moment.

[@indyjons321]

I flew gliders for a couple years, ground effect saved my life once.

[@grimreapers]

awesome

[@dmn01]

For those interested in an absolutely bloody excellent book about Helicopters read CHICKENHAWK by Robert Mason. For the aviation geek I cannot recommend it enough. I've read it 6/7 times in the last 20 years. I've lent the book so often I've had to buy it 3 times. I don't mind, it's worth it. You'll have a better understanding of how choppers work and how god awful Vietnam was. What a shit show. Anyway, go and buy it, no need to come back an tell me how right I am.

[@FinalGlideAus]

Remember Cap that induced drag is most effective at lower speeds where profile drag is most effective at higher speeds. Us glider pilots use ground effect quite often. Have a look at the end of this video of mine. kzbin.info/www/bejne/qKSuYqCrqct5hK8

[@grimreapers]

thx

[@FinalGlideAus]

Oh and think of profile drag like someone pushing against the airframe from the front and induced drag like someone pulling the plane back from behind with rope. Induced drag effects the object most at low speeds and it’s effect tapers off as speed increases. Profile drags is least effective at low speed but increases as speed increases. There is a point on the polar curve where they balance out and that’s where things like best cruise speed of best glide speed are calculated. The effect is similar to helicopters where the aircraft can takeoff but not get out of ground effect when overloaded or underpowered (takeoff altitude can also affect this) and also is responsible for the “floaty” feeling when trying land an aircraft that you flare when landing.

[@Roarkady]

you should try it over smooth and level hard surface... water is much less effective for ground effect. maybe you should try some lower speeds too

[@DCS_World_Japan]

That's way too low to be "testing" ground effect. Ground effect is supposed to happen when your height is around half the aircraft's wing span. That said, I've noticed ground effect the most in the Mi-8.

[@grimreapers]

rgr thx

[@gvii]

Look up the Russian Ekranoplan vehicles. Those ought to really blow your noodle.

[@Scoobydcs]

Caspian sea monster ftw

[@RanmaSaotome12]

you have nerves of steel flying so low for so long

[@TheGranicd]

"...and F18 is just stupid". Made me chuckle.

[@Viking355th]

Some aircraft are designed to operate exclusively within ground effect. en.wikipedia.org/wiki/Ground-effect_vehicle

[@Forest0922]

Lol you said testicle features @4:05

[@bradorem2262]

4:10 you said testical features 😂😂😂

[@btfoaccounting2902]

46 mins? Couldn't you just sum up the results in a 2 min video?

[@taipan185]

So how does someone who is completely new to the game go about joining you guys? It seems to me that the best way to learn DCS is by joining a group with a solid structure.

[@grimreapers]

DCS need you to have 1 years XP, but our Arma 3 is free to all to join.

[@taipan185]

@@grimreapers Ouch, well thats a little way off. Shame you guys dont play Squad