Landing flare at Nellis

[Yurgon]

There is an area of turbulence under the bridge at Hoover dam. Fly a Huey under it and you'll see it straight away.

 

Not sure whether it's really related, but there's a new thread about that disturbance including a video that shows it quite nicely in the F-15: Odd Transient When Flying Under Bridge

[Yurgon]

I did some testing myself regarding the landing flare anomaly.

 

I got it every time after I had flown below the Hoover dam bridge, which I did I think 4 times in an A-10C Free Flight mission.

 

Mission specs:

 

 

- Date: June 6

- Time: 18:30

- Weather and loadout:

 

 

 

 

I tried McCarran 25L and 25R and Nellis 21L (I think, might have been 21R though, it was completely dark by then).

 

Each time this flare anomaly had happened, it wouldn't return until I flew below the Hoover dam bridge again, no matter how many times or where I landed in the meantime (at least with the runways stated above; I didn't feel like taking the trip to Creech or Groom Lake).

 

So I'm pretty sure there's a connection between that bridge or something close to it and the landing flare anomaly.

 

I saved the track but it's basically 12 MB of nonsensical flying around Vegas. If anyone's interested, I'll upload it, but I think we've now got enough groundwork for the testers to look for a specific effect under specific circumstances.

 

BTW, has this been reported in 2.0 Bugs & Problems yet?

[Mike77]

Additionally, while I was holding short of the runway, a 109 passed low over a friend of mine and myself. We both noticed our planes shook a bit.

 

Awesome to see this stuff modeled, even if it still needs some fine tuning I guess.

 

 

Wow! Thank you for that report. That really is awesome. Still in Alpha, so really looking forward to the fine tuning/tweaking and what's ahead.

 

It sure is a GREAT time to be a flight sim enthusiast :)

 

Mike

 

 

 

 

 

Sent from my iPhone using Tapatalk. System specs: Windows 7 Pro, EVGA X58 3x classified 3 MOBO, i7 960 @3.2Ghz, 24Gb Ram, Nvidia EVGA GTX 780ti with 3 Gb VRAM.

[ctannell]

BTW, has this been reported in 2.0 Bugs & Problems yet?

 

Well there's the report about the transient stuff underlying the dam in the 2.0 specific forum.

 

http://forums.eagle.ru/showthread.php?t=154901

 

I also put a report in the regular A-10C bug section (as per instructions for module specific issues, although I no longer think this is just related to the hog).

 

http://forums.eagle.ru/showthread.php?t=154630

 

I now expect these are the same issue and perhaps should be merged once a mod takes a look at this.

[Donut]

It is interesting the people mention the Hoover Dam bridge. As I think back to the flight that my brother and I experienced ground effect at Groom Lake, we had both flown under the bridge. There were two others in our flight who did not fly under the bridge and did not experience any ground effect when landing. There definitely could be a correlation here.

[Aeroscout]

There is an area of turbulence under the bridge at Hoover dam. Fly a Huey under it and you'll see it straight away.

 

It's not really turbulence, it's the same kind of glitch you can already find in some hangars and oil rigs in 1.2 and 1.5.

More details and a track here: http://forums.eagle.ru/showthread.php?t=154325

 

Whether it's related to what is described here, however, I do not know.

 

Not sure whether it's really related, but there's a new thread about that disturbance including a video that shows it quite nicely in the F-15: Odd Transient When Flying Under Bridge

 

Yup, that's it. It's not really an increase in lift so much as just a disturbance. It happens in yaw, or at least in the inertial XY plane (See the bit where I go under when banked, it seems to be along the horizon). I figured I'd just post the video and be done with it, but now part of me wants to set everything back up and try it with a slower aircraft.

 

It is interesting the people mention the Hoover Dam bridge. As I think back to the flight that my brother and I experienced ground effect at Groom Lake, we had both flown under the bridge. There were two others in our flight who did not fly under the bridge and did not experience any ground effect when landing. There definitely could be a correlation here.

 

That's interesting. I might have to give that a go.

 

Another thing, ground effect isn't going to result in pitch up so much as an overall increase in lift. In a fixed wing aircraft, however, the effect should be very subtle, so I doubt this landing disturbance is ground effect modeling, or at least, it doesn't appear to be proper ground effect modeling if is indeed pitching up.

[Corrigan]

What if ground effect is modelled, and flying under the ground (=bridge surface) is messing something up?

[Yurgon]

I tested this some more to find a common denominator.

 

2 out of 3 times, I got the same landing flare anomaly after flying below the road bridge at Las Vegas Freeway crossing Tropicana Ave (according to Google Maps) not far from McCarran.

 

That one:

 

 

The third time, I heard the canopy or maybe the vertical stabilizers scratch the concrete; after that pass, the next landing felt pretty normal (strangely enough, there seemed to be no damage to the aircraft at all :music_whistling:).

 

So I would theorize that the Hoover dam bridge isn't the only structure to trigger this type of behavior.

 

I also flew below one of the road bridges a bit further south of the above one and the next landing was normal.

 

I also was NOT able to reproduce the landing anomaly with Bf 109 and Fw 190, even after flying below the Hoover dam bridge (both landings were terrible, but I believe that was 100% my fault :D).

[Aeroscout]

I have noticed the issue where there appears to be an impact, but there's in fact no damage. Happens in the video below.

 

So, I did some more flying, and this is what happened. I'll let the video speak for itself.

 

 

Notice the significantly different trim positions.

[Yurgon]

So, I did some more flying, and this is what happened. I'll let the video speak for itself.

 

Great video, thx!

 

It shows exactly the same that happens to me whenever I fly under the bridge and try to land in the A-10C.

 

It feels as if the aircraft somehow gets infected by flying under the bridge, and gets healthy again after one landing attempt.

 

Other than this landing flare, I never noticed any other odd behavior after flying below the bridge.

[Aeroscout]

It's not really turbulence, it's the same kind of glitch you can already find in some hangars and oil rigs in 1.2 and 1.5.

More details and a track here: http://forums.eagle.ru/showthread.php?t=154325

 

Whether it's related to what is described here, however, I do not know.

 

I decided to take the Huey for a spin under the bridge. Here's how it went:

 

Something's really messed up here, though you say it happens in 1.2/1.5? Is there a bridge in the Black Sea map that exhibits this behavior? I'm wondering if we could give it a try in the A-10C to see if it happens there too.

[Yurgon]

Something's really messed up here, though you say it happens in 1.2/1.5? Is there a bridge in the Black Sea map that exhibits this behavior? I'm wondering if we could give it a try in the A-10C to see if it happens there too.

 

Huh, interesting.

 

When hovering into those huge hangars with one side open, which can be found on most airports all across the Black Sea map, I always thought that the helos (Ka-50 and UH-1H) developed a strange lift tendency where they would suddenly start to climb, and lateral movement also seemed to be very different. That caused me to crash quite a few times until I anticipated this tendency and corrected for it.

 

Come to think of it, the Hoover dam bridge is probably just big enough for us to really notice the effect, even more so as the old hangars never allowed an A-10 to enter them (well... enter, yes, exit, not so much :D).

 

Of course that still doesn't explain the landing flare anomaly on the next touchdown, even if it happens 10 or more minutes later in a different part of the map, and why it only seems to affect certain airframes.

[Flagrum]

Interesting theory, Yurgon. Perhaps the "(DCS) World Physics" doesn't (completely) apply in buildings and the bridge is just a building and between the pylons, we are inside of it.

 

Does this effect also happen if one flies much lower benath it? I.e. directly above the water, where the building perhaps does not reach that far down?

 

edit: thinking about it ... maybe the physics are all there and the behaviour in hangars is correct? Perhaps there is some sort of "reverse in-ground effect" or rather "under-ceiling effect"? There is lower air pressure above the wing - which creates the lift - correct? If now no new air can fill that low pressure area from above - as the airflow is blocked by a ceiling, the low pressure/lift effect is strengthened?

 

But for a "ceiling" that far above like here ... it definately is exaggerated then.

Edited December 12, 2015 by Flagrum

[Aeroscout]

If a helicopter hovers below a solid surface, it will indeed generate additional lift, and will appear to be sucked up towards it. However, this will only happen within a rotor diameter or two, much like ground effect. Helicopters obviously don't fly under things very often or at all, and so this is never really analyzed. I can't imagine there's much real world data on it.

 

Anyway, that said, I don't think that's what's going on here, and if it is, they've done it wrong. The bridge is way too far in the far field for it to have much effect (remember, we're talking only a rotor diameter or two). Additionally, there's a clear, distinct boundary where the aircraft enters and exits this disturbance. Should it be a real phenomenon, I would think it would fade in and out in some manner.

[Aeroscout]

Come to think of it, the Hoover dam bridge is probably just big enough for us to really notice the effect, even more so as the old hangars never allowed an A-10 to enter them (well... enter, yes, exit, not so much :D).

 

Of course that still doesn't explain the landing flare anomaly on the next touchdown, even if it happens 10 or more minutes later in a different part of the map, and why it only seems to affect certain airframes.

 

Yeah, that's why I was looking for something you could fly through in a fixed wing where this happens.

 

Interesting theory, Yurgon. Perhaps the "(DCS) World Physics" doesn't (completely) apply in buildings and the bridge is just a building and between the pylons, we are inside of it.

 

Does this effect also happen if one flies much lower benath it? I.e. directly above the water, where the building perhaps does not reach that far down?

 

That's an interesting idea. I'll have to give that a shot. The flight model is obviously taking the presence of the building into account, which is interesting. I didn't think it would beyond collision detection. I guess it all comes down to how the flight model is done, and how robust it can be made for these kinds of cases. For instance, the flight model has to know to model ground effect only when above an object, not beneath it. Seems obvious, but is something that could be overlooked. Of course, this issue could have nothing at all to do with ground effect. We have no way of knowing without actually seeing how it's modeled, and from what I know about ED, that's never going to happen.

[gnouze]

Difficult to land the F-15 , in DCS World 2.0 but also in 1.5.

The flare (pitch attitude increase) has nearly no vertical speed impact, at 150 kts. The planes sinks onto the runway. It wasn't the case in 1.2.

 

Also the drag is non existent , when at idle. Even the airbrake is not really efficient. But a turn or two is too much effective too me.

 

And the power in mil is also weak.

 

Gnouze