If ground effect are so much more efficient why aren’t we using them for flights, from Europe to the US for example?
In: Engineering
Is that the very low flying planes?
Probably waves.
The Soviets did some pretty cool prototyping with ground effect “Erkanoplans”. Do some googling on those and you’ll see the main reasons why the technology was abandoned.
Short answer: they suck as soon as the sea gets a little too choppy. Which most of the Atlantic and Pacific is. They might do ok on smaller bodies of water, but by the time you’re doing that it’s too much hassle compared to regular air travel or boat travel.
Ground effect is more pronounced over flat and calm surfaces. In the case of long-distance flights, the aircraft would encounter various weather conditions, including turbulence, which could make flying at low altitudes challenging and unsafe.
The ground effect increases lift. At the same time flying at sea level mean the air pressure is a lot higher and it increases drag. The result is it is more fuel-efficient to fly very high up.
Flying where you have a ground effect would be a lot less safe. Airplanes can crash into ships, large waves, islands, and other airplanes because there is no vertical separation.
The sea isn’t flat.
In the middle of the Atlantic it’s not uncommon to run into 20-40 foot waves.
There are lots of reasons why.
1. It’s not particularly safe. Large waves, inclement weather and even shipping could cause a catastrophe with little warning.
2. Airplanes and water aren’t wonderful friends. Building a plane that needs to also float and endure water landings is actually fairly tricky and adds significant weight.
3. Needing smooth water conditions along the coastline for take-off and landing would likely lead to significant travel delays in many locales.
4. There’s not enough space to manoeuvre. If all the planes travelled at the same altitude, they simply couldn’t achieve the same level of air traffic density without risking collisions frequently.
5. Flying at high altitude is typically more fuel efficient than flying at sea level.
Because if there’s a wave, the plane hits the water.
At plane speeds that’s just as bad as crashing into the ground.
Something not mentioned by the other (vgood) answers here is maintenance.
Salt water spray and mist ingest into engines means some very expensive maintenance cycles and bills. This alone makes the concept infeasible even to military standards, nevermind commercial.
The drag gains at high altitude would negate any benefit. The biggest benefit of ground effect is more lift with less wing. Fuel economy and ultimately operating cost is really all anyone in commercial air flight care about
The “ground” (ocean surface) doesn’t stay sufficiently level when the ocean starts to get large swells. Ground effect depends on a reasonably consistent distance between the lifting surface and the ground below, and as soon as that changes, efficiency goes way down. It can also get dangerous, with tops of waves hitting the airfoil.
It’s more practical on lakes, but there’s not enough benefit on shorter hops.
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