Ground Effect




Ground effect is the positive influence on the lifting characteristics of the horizontal surfaces of an aircraft wing when it is close to the ground. This effect is a consequence of the distortion of the airflow below such surfaces attributable to the proximity of the ground.






IGE (In-Ground Effect)

IGE conditions are usually found within heights about 0'5 to 1 times the diameter of the main rotor. So if a helicopter has a rotor diameter of 48 ft, the IGE region will be about 24-48ft above the ground. The height will vary depending on the type of helicopter, the slope and nature of the ground, and any prevailing winds.
The air impacting the ground creates a small build-up of air pressure in the region below the rotor disc. It seems as if the helicopter is floating upon a cushion of air.
The stagnated air will form a high-pressure zone just underneath the fuselage body of helicopters. There is basically no more motion inside this. Which will cause the air to not enter into it. Hence, the collective required is reduced significantly.

OGE (Out of Ground Effect)

A helicopter hovering 150ft above the ocean surface will be in an OGE condition and will require more power to maintain a constant altitude than if it was hovering at 15ft. Therefore a helicopter will always have a lower OGE ceiling than IGE due to the amount of engine power available.

Published performance figures for a given helicopter may state something like:

Hover Ceiling at Max Weight = 4000ft OGE and 6000ft IGE.

This means that the fully loaded helicopter can hover at 4000ft above the ocean (ie. no hard surfaces close below), and can hover at 6000ft above a tall mountain top where there is the ground close below (within 0.5 - 1.0 rotor diameters). Mountains this high are common in Papua New Guinea for example.


The phenomenon has been explained with an interactive simulation. The following link will redirect you to the project page.
(For the mobile version, please go to the bottom of the page)
Ground Effect on Scratch



Simple Ground Effect Simulation in Helicopters to understand the phenomenon of Ground Effect in Helicopters. 

Press Up or Down Arrow to increase or decrease Collective. The helicopter will gain altitude if the total lift is greater than the weight and will lose altitude if it’s not.
The graph shows the required amount of collective for hovering at different altitudes.
Press Left or Right Arrow to change the Pitch.
The Arrows point towards the direction of the arrow keys pressed.





Mobile Version of Ground Effect on Scratch







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