SPH-4 U.S. Army Flight Helmet Performance 1972-1983

Abstract

Orders will be expedited if placed through the librarian or other person designated to request documents from DTIC.

Static and Dynamic Retention Assessment of the HGU-56/P Aircrew Integrated Helmet System Equipped with Quick-release ALPHA and Snap-fastener Retention Assemblies

“…However, several documented cases of helmets departing aviator's heads during crashes prompted the USAARL to explore several methods of assessing the dynamic retention capabilities of aircrew helmets (Reading et al, 1984, andVyrnwy-Jones, Lanoue, andPritts, 1988), with the mini-sled being the latest and most promising method. No requirements have been proposed as to how much helmet rotation is acceptable, but in general, helmet rotation -forward or rearward -should be minimized, as rotational displacement of the helmet can expose the head, allowing unprotected impacts to occur.…”

SPH-4 Aircrew Helmet Impact Protection Improvements 1970-1990

“…Even though the linear velocity of the helmeted head relative to the seat structure may range upward to 50 fps at a point from l-to-2 feet away from the seat headrest, the head is moving on an arc both forward and downward and is more likely to strike an object with a tangential (glancing) impact rather than a head-on (perpendicular) impact as practiced in the ANSI test method. Aircraft accident head injury studies supportthe theory that most helmeted head impacts occur with less than a 90-degree impact angle, but the exact angle is never easily determined and usually is recorded as an abrasion (Reading et al, 1984).…”

“…Penetrating-type head injuries rarely occur in actual survivable Army helicopter crashes due to the low incidence of helmet damage caused by hemispherical or sharp, rigid surfaces in the cockpit. Flat surfaces are the major impact surface types found in Army helicopter cockpits (Slobodnik, 1980;Haley et al, 1983;Reading et al, 1984;and Vyrnwy-Jones, Lanoue, and Pritts, 1988) (see Table 2). In order to pass the hemispherical surface impact test and the penetration test, it is necessary for the aircrew helmet to possess a relatively thick and rigid shell as well as a relatively high density foam liner.…”

“…Prior to 1980, USAARL testing included the hemispherical surface impact test on the SPH-4. Data obtained from Army helicopter accidents have shown that in most survivable crashes an aircrew helmet usually sustains only one severe impact (Reading et al, 1984). Therefore, performing one drop test per impact location appears to be a good representation of what cccurs in most survivable crashes.…”

“…However, this dynamic test falls short of evaluating the effectiveness of the retention system to prevent rotation on the head. Excessive helmet rotation and helmet loss have been a problem with the SPH-4 (Reading et al, 1984;Vyrnwy-Jones, Lanoue, and Pritts, 1988).…”