Injury incidence with T-10 and T-11 parachutes in military airborne operations.

Background: The T-10 parachute has been the U.S. Army standard parachute since 1952 and is now being replaced by the T-11, which has a capacity for heavier loads. This investigation compared injury rates between the two parachute systems during mass tactical parachute training exercises at Fort Bragg, NC.

Methods: Investigators were on the drop zone for all parachute operations. Data on injured jumpers were collected on the drop zone and supplemented with medical records. Operational data were collected from standard reports and weather data were obtained using a Kestrel(®) Model 4500 pocket weather tracker.

Results: There were a total of 131,747 jumps resulting in 1101 injured service members for a crude incidence of 8.4 injuries/1000 jumps. Most injuries (88%) with a known injury mechanism were associated with ground impact. In univariate analysis, risk of injury with the T-10 was 9.1/1000 jumps and that with the T-11 was 5.2/1000 jumps [odds ratio (T-10/T-11) = 1.72, 95% confidence interval (95%CI) = 1.45-2.08, P < 0.01]. Other factors that independently increased injury risk included night jumps, combat loads, higher wind speeds, higher temperatures, certain aircraft, and entanglements. After controlling for these factors in a multivariate analysis, injury risk was still higher for the T-10 parachute when compared to the T-11 [odds ratio (T-10/T-11) = 1.56, 95%CI = 1.28-1.89, P < 0.01). For virtually all strata of the independent risk factors, the T-11 had a lower injury rate.

Conclusion: Compared to the T-10, the T-11 parachute had a lower injury incidence under virtually all the operational conditions examined.