![]() The idea for the goggles came from Cal's experience during his early days of flying helicopter (1957) at Eniwetok Atoll during nuclear tests under 'Operation Hardtack' and later from his experiences with the flash curtain, gold goggles and eye patch problems encountered as a SAC B-47 and B-52 aircraft commander with the 306th and 509th Bomb Wings." "The PLZT material was developed by two engineers, Gene Haertling and Cecil Land, from the Sandia National Laboratories in New Mexico from 1961 to 1973 (U.S. The requirements for the goggles was orchestrated by Cal Crochet, SAC Life Support System program manager, who was the direct interface with Sandia Laboratories at Kirtland AFB, NM. Unfortunately, in order to obtain the desired switching speed, this meant that when the nuclear flash protective goggle failed, it was basically opaque." "PLZT is a ceramic material consisting of lead, lanthanum, zirconate, and titante and it can be electronically switched rapidly in polarity, such that when sandwiched with a near infrared blocking material and a fixed polarizing material, the visual transmittance can be varied from full open state (approximately 20%) to totally opaque within a ten-millionth of a second." "The protection device (helmet-mounted special goggles containing four lenses) was developed under a $7.2 million contract managed by Aeronautical Systems Division at Wright-Patterson AFB, Ohio. The designers of the PLZT goggle had found that the material could be discharged quicker than when charged to change the transmittance. This causes the lenses to go black, protecting the vision of anyone wearing the helmet. But any dangerous flash of light, such as lightning or a nuclear blast, instantaneously breaks the circuit. When linked to an electric current, the lenses are clear. These goggles are made of sandwich composite of polarized glass with an inner layer of a transparent electro-optic ceramic called PLZT. Here's another excerpt from Flightgear.dk website: "The most advanced thermal flash protective devices in use are the PLZT goggles. Hence the need to use PLZT protective devices on the dual visor housing of an HGU-55 flight helmet (HGU-55E). It will occur only when the fireball is actually in the individual's field of view and should be a relatively uncommon injury." Retinal scarring is the permanent damage from a retinal burn. ![]() At night, with the pupil dilated for dark adaptation, flash blindness will affect personnel at greater ranges and for greater durations." "Partial recovery can be expected in 3 to 10 minutes, though it may require 15 to 35 minutes for full night adaptation recovery. During daylight hours, this temporary effect may last for about 2 minutes. "This flash swamps the retina, bleaching out the visual pigments and producing temporary blindness. Just imagine the impact of a temporary blindness on an aircrew flying in hostile environment who are not able to read instruments and operate systems. The nuclear weapons panel in the cockpit of a B-52.Īs explained in details by Steen Hartov in an article published by Flightgear On-line (one of the most famous websites among flight helmets collectors and one of my personal favorites on this topic for years), nuclear detonations would cause "Flash blindness" making extremely difficult, if not impossible, for a pilot, to handle the aircraft for some time. ![]() Account icon An icon in the shape of a person's head and shoulders.
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