Noob Q: Huey in Ground effect on a ship?

[cfrag]

Please be advised that I'm a complete noob when it comes to helicopters. I've just begun training on the Huey, and for training purposes set up a complete unrealistic mission with no wind, and a couple of stationary ships set up just a a few yards off the coast near Batumi.

 

Now, after learning just about every possible way of crashing, stalling, drowning and otherwise fatally missing the boat, I finally managed to land on the Tarawa's (?) deck. It may have been my excitement or other factors, but to me it felt as if there was a distinct difference to landing on the ground; I had the impression that the ground effect was substantively less pronounce, perhaps even non-existent. From my understanding (ha!) of the involved physics, a ground effect should build up if the surrounding landing surface is large enough - and I deemed the landing platform as such. 

 

So my question is:

- was it just me or is there less / no ground effect when landing on a Tarawa?

- is this realistic?

 

I must be a masochist since I greatly enjoy the Huey while doing a worse job at flying it than a drunk captain navigating the Suez. Thanks for any pointers.

 

-ch

 

[admiki]

Did you set Tarawa to move or complete stationary?

If it's moving fast enough, you are prety much over ETL all the time. so no apparent ground effect. 

Anyway, get in one foot hover over deck, remove your hand from collective  and then sloooowly slide to one side and see what happens once you clear the deck.

Other way to compare is to get into stable hover, stable part is important, take note of engine parameters and then do the same over deck. 

TL;DR yes there is ground effect over deck.

 

[scoobie]

(I wrote it before admiki posted, so I'll paste it as-is, anyway).

 

I've just added Tarawa to the simplistic mission I had made when I was learing Huey, and tested.
All ships feel more or less the same to me in terms of "ship-ground" effect. Tarawa felt equal to Nimitz, OHP probably the same, Handy Wind, I guess all of them.
Oh, and yes, no doubt - this effect is modelled in DCS! Decks, helipads, roofs, water, ground, it's all there.

 

If you want to test it yourself, hover just outside Tarawa's deck and slightly higher than the deck, then "creep" towards the deck, very slowly. At some point, when a "preprogrammed" portion of your rotor gets above the deck, you should feel a slight kick from below. Not big, but easily noticeable. To me it feels much as 0/1 logic, it's not gradual, there seems to be a specific threshold when ground effect suddently kicks in - 0%, then 100%. It probably isn't very realistic, but better than nothing and you do have to correct for it every time when landing on an oil platform, picking cargo from the roof of a tower block (a typical place to leave cargo for helicopters), so I'm happy either way
Oh, if you want to test OHP, it may be tricky! The helipad is small and low above water, so depending on how you approach it (steep or flat), you might get different conclusions.

 

As for the difference between ship-ground effect and ground-ground effect, it's difficult for me to say. I've just been trying to get the feeling of it, but no... I can't tell the difference. Either it's the same or at least similar.
It would need proper testing, I guess you'd need a cliff (of Dover, maybe?) for such test.

 

Yeah, Huey is huge fun and highly addictive  Belsimtek should've put a "parental advisory" label on this module

 

Edited March 28, 2021 by scoobie

[cfrag]

Thanks, everyone. Practice does make perfect, and with 8 hours more under the belt, I can say that my initial observations were indeed adrenaline-infused. Also, as @scoobie mentions, there is a rapid drop-off at the edge of the ship; not being familiar with the Huey I most probably misjudged if I was above the deck or not. 

 

Thank you so much, and what a great module

 

[shagrat]

On 3/28/2021 at 7:03 PM, cfrag said:

Thanks, everyone. Practice does make perfect, and with 8 hours more under the belt, I can say that my initial observations were indeed adrenaline-infused. Also, as @scoobie mentions, there is a rapid drop-off at the edge of the ship; not being familiar with the Huey I most probably misjudged if I was above the deck or not. 

 

Thank you so much, and what a great module

 

Try to visualize what happens with the air in ground effect. If you move over the deck or a roof, etc. the part of the rotor disc not over the "obstacle" produces no ground effect (compressed air), while the other half does, as soon as it pushes enough air down that can't move aside. That effect should imbalance the helo quickly and quite pronounced, I guess.

[cfrag]

An interesting thought, thank you! Since air is a highly compressible medium, I might theorize that the column beneath the rotor quickly stabilizes in some sort of slope, much like when on tilted ground. I would therefore expect some kind of gradual ground effect when passing over the edge. Not that I could really tell, as my skills have not yet progressed much farther than being really happy with being able to re-use the aircraft after touchdown

 

 

Edited March 30, 2021 by cfrag

[shagrat]

1 hour ago, cfrag said:

An interesting thought, thank you! Since air is a highly compressible medium, I might theorize that the column beneath the rotor quickly stabilizes in some sort of slope, much like when on tilted ground. I would therefore expect some kind of gradual ground effect when passing over the edge. Not that I could really tell, as my skills have not yet progressed much farther than being really happy with being able to re-use the aircraft after touchdown

 

 

 

There is a hard edge on the deck or buildings, so the air creates a turbulence on the edge, no "gradual" cussion.

A slope is even worse, as it reflects the air away in an angle so there is no compression from air pushing "up"... the airflow simply dissipates at an angle.