Aircrew Helmet retention in ejection – The importance of custom fitted edge‐roll

摘要

One year after the termination of the Yom‐Kippur war, a report published by SurgeonGeneral of The Israeli Air Force (IAF) showed that in 44 out of the 67 recorded ejections, thehelmet was lost during the ejection. Three (3) additional helmets rotated forward causing faceinjuries.Resulting from helmets loss, four (4) air crewmen suffered from head injuries after landing.To remedy helmet separation in ejection, aircrew helmets custom fitting methods wasdeveloped, fielded (1978) and later integrated into a new lighter helmet shell.Since the introduction of custom fitting helmet was retained on head in more than 90% ofejection events. In most helmet separation events, either visor was in up position; canopycollided with the helmet or occurred in an irregular ejection.The IAF pilot's helmet is based on Israeli made, light weight shell (shaped to HGH‐22/Pgeometry). The helmets configuration is identical to standard issue US Air Force (HGU‐2A/P;HGU – 55/P) and Navy (HGU‐68/P) using the same accessories. The only difference in the shapeof the helmet’s parts subjected to wind blast air‐flow is the custom fitted edge‐roll. Theinstantaneous seal when subjected to wind blast in ejection is enough to prevent entrance ofairflow into the helmet. The conversion of airflow’s dynamic pressure to static pressure insidethe helmet is prevented and with it ballooning and exertion of lift forces on the helmet (themain cause to helmet/ head separation).It is our conclusion that a well fitted, snug edge‐roll plays an important role in air crewhelmet on head retention in ejection events.