During the Vietnam War, it was not uncommon to see photos of soldiers with their feet dangling from a Huey. War movies also promote this image, with soldiers ready to jump from the helicopter as soon as it lands. So, how do those soldiers keep from falling out?
TLDR – Soldiers do not fall from the helicopter due to physics. When the helicopter turns, the centripetal force presses inward, keeping soldiers sitting on the cabin or the cabin’s lip pressed to the floor. In today’s military, soldiers are also typically harnessed or strapped.
Why Don’t People Fall Out of Helicopters?
When the blades of a helicopter rotate, they generate lift. When the helicopter turns, the force of lift includes two specific components. The first component is the vertical lift caused by centrifugal force. Centrifugal force is the equal and opposite reaction that allows the helicopter to change direction.
The second component is the horizontal lift caused by centripetal force. The centripetal force moves horizontally toward the center of the object around which it rotates, which is the cabin of the helicopter. The centripetal force keeps outer objects pressed inward toward the center.
Along with centripetal force, soldiers avoid falling out of helicopters thanks to harnesses and straps. The interior of a military helicopter includes a wide range of fittings for securing people or cargo.
Many of the fittings are found on the floor of the cabin. A long strap is often secured to the soldier’s belt. They often call the strap a “monkey tail” or a “monkey harness.”
Along with individual straps, some military helicopters use a five-point harness system. Soldiers are secured to seats with a safety harness that is not too different from the harness systems found on child safety seats. Standard lap belts are also found in most helicopters.
How Do Door Gunners Not Fall Out?
As with soldiers sitting at the edge of the cabin, door gunners avoid falling out due to a combination of gravity, inertia, and safety harnesses. Door gunners were first used during the Vietnam War. They would ride on CH-21, UH-34, and UH-1 helicopters with the door open, typically while secured to a strap.
The first door gunners used standard rifles. However, the military soon began mounting medium machine guns on swivel mounts. For increased stability, the guns were sometimes secured with bungee cords.
The door gunners were typically restrained using a standard lap belt or a monkey harness. The monkey harness secures to the waist and connects to fittings on the floor of the cabin. This gives the door gunner more maneuverability and keeps them from falling out.
As helicopters were not initially designed for door gunners, they would leave the door open or remove it from its hinges. Several modern military helicopters eliminate the need to leave the door open or off. For example, the doors of the Black Hawk helicopters have windows. The machine gun is mounted with the barrel pointing through the window. The door can remain closed, but the window needs to stay open.