Openings in military parachutes regulate airflow, helping steady the canopy and prevent violent rocking or collapse that could send a jumper into an uncontrolled fall. The T-11 static-line chute has deliberate openings and descends at about 19 feet per second.
The T-11 replaced the T-10 in 2015. A study published by the National Institutes of Health and cited in the article reported 5.2 injuries per 1,000 T-11 jumps, versus 9.1 per 1,000 T-10 jumps. The T-11 descends three feet per second slower, and its canopy takes about six seconds to inflate, reducing the jolt of a hard opening that can injure a jumper.
Static-line T-11s offer little steering. By contrast, ram-air chutes used in free-fall jumps have front openings that fill the canopy with air, stiffening it like a wing and giving jumpers more control and forward travel. The Marine Corps' PS-2 is reported to have a 5-to-1 glide ratio.
