What is HIGE in Aviation? (Hover In Ground Effect)

What is Hover in Ground Effect (HIGE)?
Hover in Ground Effect (HIGE) is a term used in aviation to describe the phenomenon of an aircraft hovering close to the ground, benefiting from the increased lift generated by the ground effect. Ground effect is the increase in lift and decrease in drag that occurs when an aircraft is flying close to the ground or another large surface, such as water.
When an aircraft is hovering in ground effect, it is able to maintain a stable hover at a lower power setting compared to hovering out of ground effect. This is because the cushion of air trapped between the aircraft and the ground enhances the lift produced by the rotor or wings, allowing the aircraft to achieve a higher lift-to-drag ratio.
Hovering in ground effect is particularly advantageous for helicopters, as it allows them to operate more efficiently and with greater stability. However, fixed-wing aircraft can also benefit from ground effect during takeoff and landing, especially for aircraft with short takeoff and landing capabilities.

The Physics Behind Hover in Ground Effect
The physics behind hover in ground effect can be explained by the principles of aerodynamics and fluid dynamics. When an aircraft flies close to the ground, the airflow around the wing or rotor is influenced by the presence of the ground.
As the aircraft approaches the ground, the air beneath it becomes compressed, causing an increase in pressure. This higher pressure results in an increase in lift, while the reduced vortex drag further enhances the aircraft's performance. The ground effect is most pronounced when the aircraft is hovering at an altitude equal to its wingspan or rotor diameter.
The ground effect also alters the airflow patterns around the aircraft. The downwash, or the downward flow of air generated by the rotor or wings, is reflected off the ground and redirected upward, creating a cushion of air that supports the aircraft. This cushion reduces the induced drag and allows the aircraft to hover with less power.

Applications of Hover in Ground Effect
Hover in ground effect has various applications in aviation, particularly in helicopter operations and short takeoff and landing (STOL) aircraft. Let's explore some of these applications:

Helicopter Operations
Helicopters heavily rely on the benefits of hover in ground effect. By hovering close to the ground, helicopters can conserve fuel, increase payload capacity, and enhance stability during takeoff and landing. This is especially crucial in situations where helicopters need to land in confined spaces or operate in challenging environments, such as offshore platforms or mountainous terrain.
Hover in ground effect also plays a significant role in helicopter rescue operations. When rescuing individuals from the water, helicopters can hover just above the surface, utilizing the ground effect to increase lift and reduce the risk of rotor blades hitting the water. This allows for safer and more efficient water rescues.

Short Takeoff and Landing (STOL) Aircraft
Short takeoff and landing (STOL) aircraft, designed to operate in limited runway or landing space, can benefit from hover in ground effect during takeoff and landing. By utilizing the ground effect, these aircraft can achieve shorter takeoff and landing distances, allowing them to access remote or unprepared landing areas.
One example of a STOL aircraft that utilizes hover in ground effect is the Harrier Jump Jet. This vertical/short takeoff and landing (V/STOL) aircraft takes advantage of the ground effect to achieve short takeoff and landing distances, making it suitable for operations in confined areas or on aircraft carriers.

In conclusion, hover in ground effect (HIGE) is a valuable concept in aviation that allows aircraft to hover close to the ground, benefiting from increased lift and decreased drag. This phenomenon is particularly advantageous for helicopters and STOL aircraft, enabling them to operate more efficiently, safely, and with greater maneuverability. Understanding and utilizing hover in ground effect is essential for pilots and engineers alike, as it enhances the performance and capabilities of various aircraft.