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w6kd

Excessive ground effect on landing

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Anyone else having issues with the jet floating FAR too much on landing, especially in a stiff headwind?

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Which version are you running? It was either hf3 or 4 that adjusted it a bit to provide a more realistic flare attitude.

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Hotfix 4 (2987). I looked in the .air file and table 400 has ground effect providing as much as 25% lift augmentation...I think r/w figures are something more like 8-10%, and probably a bit less still in an acft with winglets.

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Hotfix 4 (2987). I looked in the .air file and table 400 has ground effect providing as much as 25% lift augmentation...I think r/w figures are something more like 8-10%, and probably a bit less still in an acft with winglets.
Based on what information?

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Based on what information?
Roskam and Lan, Airplane Aerodynamics and Performance, Ch 10.2.1

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Hi Bob. how are you?. I had all your airfiles from the PSS Airbus. Great info you provided and enjoyed that old days....The HF 4 seemed to have solved the ground effect, but the developers said that they were looking at it, because discovered in the simulator (real) that the speed on finals, was not correct or that´s what i understood from Captain Randazzo.We´ll have to wait for SP1.Best regards.Miquel Egea.

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I have not noticed any problems since the relase of Hot Fix 4. I can flare at 4 to 5 degrees easily without floating. Maybe your coming in a little too hot?VREF +5 +Half the Wind +All the Gust. (If you have the Short Field Package option enabled then forget the +5 part)

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Hi Bob. how are you?. I had all your airfiles from the PSS Airbus. Great info you provided and enjoyed that old days....The HF 4 seemed to have solved the ground effect, but the developers said that they were looking at it, because discovered in the simulator (real) that the speed on finals, was not correct or that´s what i understood from Captain Randazzo.We´ll have to wait for SP1.Best regards.Miquel Egea.
Hi Miquel; Hmmmm...I'm still floating horribly with the 2987 hotfix installed...I found it very bad yesterday landing in strong headwinds. I had not seen that PMDG was already working it...thanks for the info. @Paul--it floats with threshold crossing at Vref and no additives...can't imagine what adding another 15-20 KIAS would look like!!

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@Paul--it floats with threshold crossing at Vref and no additives...can't imagine what adding another 15-20 KIAS would look like!!
Does any of the below help you? Although they made some tweaks in Hotfix 4 for the Flare, I still think the bird is 10 knots too fast. Look at some of the examples below. I never seen the NGX go lower than 138 on vref and they are talking about vref in the 120s. So i just treat it like its 10 knots too fast and compensate as needed.Try this and see how it works for you. Next time you are landing do everything normally with VREF +5 +Half the Wind + All the gust, but pull the throtttles back to idle sooner than you normally do so that you touch down at 10 knots slower than VREF +5. Works just fine for me and some of my flares look just like the real world videos I have seen on youtube of 737-800 landings.
*When using autothrottle to touchdown set the command speed bug to Vref +5.*When planning to disconnect the autothrottle at any stage prior to touchdown, set the command speed bug as per the following.1. Add 1/2 the steady headwind component + all of the gust to Vref (maximum Vref +20) set that speed.2. The minimum speed to be set on the command speed bug is Vref +53. The maximum speed to be set on the command speed bug is Vref +204. The steady headwind additive should be bleed off just prior to touchdown. 5.The gust additive should be maintained to touchdown Examples - 1. Vref 120kts, Runway 18, wind 180/10. Bug set at 125, touchdown at 125 2. Vref 120kts, Rwy 18, wind 180/20G30. Bug set at 140 (steady headwind = 20, 1/2 of 20 = 10. Gust = 10, so 10 + 10 = additive 20), touchdown at 130 (bleed off the steady headwind additive of 10kts & just carry the gust additive of 10kts to touchdown).There are examples given in the table above the section of the FCTM that you quoted. In a lot of situations you will be touching down below the bugged speed. This is normal. However, you shouldn't be touching down below Vref +5. You also shouldn't be flying an approach above the bugged speed or touching down above Vref + the gust additive.

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Ground effect is over the top imo. Before I get bashed, I'm not a real pilot, all I am basing it on is many video's ive watched online and experince with other aircraft. I done a test where you "pretend" to land at 1000ft mark, the difference in how the aircraft behaves when you pitch back slightly at 1020ft and cut the throttles compared to 20ft and cut throttles is amazing, i can cut throttles at 1020ft, pitch back to 5 degrees and the aircarft still descends, if you pitch back to 2 degrees at 20ft, the airaft climbs back up before descending again. It just seems fat to exagerated, a bit like flying a vstol. Even with the latest patch, I need to fly at vref -5 and cut the throttles at 100ft to get some sort of feeling to land, if I fly "on the numbers" I can simply cut the throttles and the ground effect over flares the aircraft for me without any yoke input!

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Guys, not to trivialise your opinions (they're valid, the NGX is a floaty beast) but as we all know PMDG put a lot of work into every aspect of this sim, flight model included. Is it not possible that our technique is what's at fault here?It took me quite a while to get the hang of landing the 737 but in fairness I (and indeed all of us) have been flying heavies for years and the characteristics of those aircraft are quite different in the flare. I took the MD11 for a flight the other day, the first time since NGX beta started, and I fair SMASHED it into the ground because I delayed the flare until 20 feet!Just like the real world, every aircraft type behaves differently, it's down to you as PIC to refine your technique for the aircraft.

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Hi Mark. Yesterday I had a landing with a 25-kt headwind, crossed the threshold at 50 ft and Vref with the power at idle, and it floated over 4000 feet down the runway before I forced it down and planted it. I can't explain that away as technique...

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G'day Bob, to be fair it might be that PMDG are adjusting this parameter for the SP, I'm not sure. I'm certainly not about to tell someone with your RW experience that they are at fault!The point I'm trying to make (more for the benefit of the exclusively virtual aviators on here) is that if you try and flare the NGX exactly as you would an MD11 or 747 then you'll run into trouble.

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Same as Bob here, tried to land this morning with a 20 kt headwind, crossed threshold at 50ft, Vref+5, idle, floated over 3/4 of runway 11 in Oslo. Decided to go around...Haven't noticed this if no headwind is present though.Guillaume

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HI Bob and all,I´m a former ATP and my experience is on 737-700 (no wl) and I can tell that she's a floatty girl, and as in every aircraft it's a matter of a combo of tech-feel. Even in the same airplane, it behaves differently when light or heavy when landing, and of course the rule is Vref + 5 when crossing the threshold at 50 ft. What I've developped that I recall was when light go idle at the threshold, no flare till 10 feet or so; when heavy what I did was to idle just at 10 feet and a VERY little back pressure if none till touchdown. I personally tried landings with flaps 25 when heavy front wind and it works at least in real life.Is fs I applied this personal tech on the beloved TinMouse and it behaves quite real, now on the NGX I think it has to be retouched a bit since I also noticed that overfloating effect a bit. I agree with Paul Deemer in the tech he depicts above but as an old instructor told us once..."Landings are as brushing your teeth" a personal taste within the limits of a good tech.Have a good day my friends.Art Washton

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Maybe someone can answer this for me, why would headwind matter on approach? Who cares if we're going 20kts faster or slower relative to the ground? Compensating for gusty conditions I understand, but why add any of the steady head/tailwind?I'm not trying to be a smartass, it's a serious question.

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Maybe someone can answer this for me, why would headwind matter on approach? Who cares if we're going 20kts faster or slower relative to the ground? Compensating for gusty conditions I understand, but why add any of the steady head/tailwind?I'm not trying to be a smartass, it's a serious question.
In the real world, as you get close to the ground the wind will decrease due to the boundary layer close to the surface. It's like a mini windshear. So you need additional airspeed to compensate. Whether FSX reduces wind close to the ground I don't know, but it's something we always model in full flight simulators.Kevin Hall

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In the real world, as you get close to the ground the wind will decrease due to the boundary layer close to the surface. It's like a mini windshear. So you need additional airspeed to compensate. Whether FSX reduces wind close to the ground I don't know, but it's something we always model in full flight simulators.Kevin Hall
Thanks for the info. It didn't even occur to me to consider wind diminishing near the ground.

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That's a fact, wind dynamics generates a sort of turbulence when reaches the ground, as Ken says, a kind of mini ws, thence reducing momentum and speed, beside the density altitude and local temp that counts a lot, wing makes it's ground effect also. The other main reason is the posibility to go around and keep momentum in case you can't land for any reason. As I get it, all that arose when those early days of the golden age when a lot of accidents occured due to wind shear, if you were with less momentum when getting into it you hit the ground, till they learned how to trade speed for altitude or at least keep'er leveled and steady, there's in fact not too much room left for manouver in those cases, remember aviation has beed defined as hours of boreing by seconds of real terror... to be in the mood these days.Art Washton

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I had a session with a RW pilot on a proper simulator and when I went to land he told me to make sure that I flew it into the ground otherwise I would float down the runway. Ever since then that is what I do with the NGX and never float down the runway unless I forget to.

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I've been told the airfile line 400 isn't for aerodynamic ground effect, it's the effectiveness of the thrust while on the ground - lowering that value's going to make breakaway for taxiing require a lot more power, that's it. FSX doesn't actually simulate aerodynamic ground effect.Regardless, I did ask one of our test team pilots and he said what others have said here - it's very difficult to land the NG well, it does want to float.

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What I can't understand is why I personally haven't had any issues with floating. Perhaps some hidden variable at work.As for Paul's suggestion that VREF was 10 knots too high, I checked the manuals, and according to the charts, the computed VREF is spot on.I tend to think people flare too much, rather than the mere two degrees required. I use the HUD, which makes landing a piece of cake.Autothrust on or off Bob? Always off for the approach for me. Autothrust on, may not be automatically disingaging and throttling back soon enough.I wouldn't want to argue with Bob Scott though, most of us long time simmers will be well aware of Bob's experience, and contribution to our hobby.

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HI Bob and all,I personally tried landings with flaps 25 when heavy front wind and it works at least in real life. Have a good day my friends.Art Washton
I've never heard of a F25 landing that wasn't caused by some QRH. It's not even certified for a F25 landing. Huh.

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I've been told the airfile line 400 isn't for aerodynamic ground effect, it's the effectiveness of the thrust while on the ground - lowering that value's going to make breakaway for taxiing require a lot more power, that's it. FSX doesn't actually simulate aerodynamic ground effect.Regardless, I did ask one of our test team pilots and he said what others have said here - it's very difficult to land the NG well, it does want to float.
Not sure who's telling you that Ryan, but table 400 in FSX is the lift augmentation due to ground effect...one axis (the input) is height above ground expressed as a fraction of wingspan, the other axis (output) is a multiplier applied to the coefficient of lift. Experimentation with this table demonstrates that FSX does indeed simulate at least this aspect of ground effect, and indirectly there is also some impact to induced drag as the relative AOA (and consequently induced drag) for a given CL is lowered as the ground effect's impact to CL increases.I'm not trying to split hairs here, or argue that landing distance is 3800 ft when it should be 3600 ft. There are (so far) only two characteristics of the NGX that raise a red flag for me...one is the excessive amount of ground effect and resultant float, the other is a rash of brake malfunction episodes, which I seem to be able to avoid pre-SP1 by leaving the autobrake off through the whole flight.

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