A new hydrostatic anti-G suit vs. a pneumatic anti-G system: preliminary comparison.
OBJECTIVE
A newly developed hydrostatic anti-G suit is now commercially available. The suit is said to offer a high level of protection against +Gz acceleration. However, past experience shows that it is difficult to produce a hydrostatic suit with effective high-G protection. Careful testing is, therefore, needed to verify its efficacy.


METHODS
The G-protective properties of the hydrostatic anti-G suit (Libelle; L) were compared with those of a pneumatic anti-G ensemble (AGE-39) used in the Swedish JAS 39 Cripen aircraft. Three pilots were studied during vertical (+Gz) acceleration in a centrifuge using the following: 1) the L-suit with varied straining maneuvers; 2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); and 3) the AGE-39 in combination with AGSM during the initial part of each high-G exposure (reduced maneuver; RM). G-intensity tolerance was established during exposures to rapid onset rate (ROR) profiles with G-plateau levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during simulated aerial combat maneuvers (SACM) consisting of 10 cycles of 5.5 to 7.5 G.


RESULTS
All three pilots tolerated 9.0 G with the pneumatic system both in the RM and FM conditions; their tolerances averaged 6.3 G (range 6.0 to 7.0 G) for the L suit. Thus, during the ROR exposures only the 6.0 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition. Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L condition. In the RM condition all subjects completed the SACM profile and in the FM condition two subjects completed the SACM.


CONCLUSIONS
Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. While wearing the L-suit, G-tolerance was 6.3 G. Thus, under the conditions tested, the G-protection afforded by the L-suit is not adequate for use in a 9-G aircraft.
Defence Research Agency, Karolinska Institutet, Stockholm, Sweden. ola.eiken@fyfa.ki.se
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Eiken
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Lindborg
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Aldman
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Karlmar
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Kölegoård
D000054:Acceleration; D000222:Adaptation, Physiological; D000328:Adult; D000337:Aerospace Medicine; D000388:Air; D001794:Blood Pressure; D002498:Centrifugation; D004576:Electromyography; D004867:Equipment Design; D006112:Gravitation; D005676:Gravity Suits / Q000592:standards*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008889:Military Personnel; D016273:Occupational Exposure / Q000009:adverse effects*; D010807:Physical Endurance; D014636:Valsalva Maneuver; D014867:Water
D014867:Water