A centrifuge simulated push-pull manoeuvre with subsequent reduced +Gz tolerance.

The push-pull effect (PPE) has been recognized as a deleterious contributor to fatal flight accidents. The purpose of the study was to establish a push-pull manoeuvre (PPM) simulation with a tri-axes centrifuge, studying the effect of this PPM on the +Gz tolerance, and to make this simulation suitable for pilot centrifuge training. The PPM was realized through pre-programmed acceleration profiles consisting of -1 Gz for 5 s followed by a +Gz plateau for 10 s. Relaxed +Gz tolerance recordings were obtained from 20 healthy male fighter aircraft pilots and 6 healthy male volunteers through exposure to pre-programmed profiles with and without previous -1 Gz exposure. A statistically significant decrease in +Gz tolerance was seen in all subjects after -1 Gz for 5 s exposure, 0.87 ± 0.13 G in the volunteer group and 0.95 ± 0.25 G in the pilot group. The ear opacity pulse as a +Gz tolerance endpoint criterion was sometimes found to be unreliable during the PPM experiments. The simulated PPM in this study elicited a PPE, which was obvious from the significant reduction in +Gz tolerance. The PPM profile appears useful to be included in centrifuge training.

[The protection effect of a new combined anti-G measure].

AIM: To observe the protection effect of a new combined anti-G measure which was composed of KH-x anti-G suit, unassisted PBG (positive pressure breathing for G, PBG) and PHP maneuver. The problem of fatigue and pain when using this measure was also discussed. METHODS: Five fully qualified centrifuge subjects were exposed to 5 groups of +Gz exposure: (1) relaxed tolerance, (2) KH-x and KT-x, (3) PBG, (4) 6.5 G 45 s, (5) 9.0 G 15 s. The subjective feeling of fatigue and pain induced by +Gz exposure was evaluated by the questionnaire after runs. RESULTS: There was no incidents of G-induced lose of consciousness in this study. The protective effect of KH-x and KT-x was 2.3 G while it was 1.7 G for PBG. All the subjects have accomplished the 4th and 5th runs. The pain has developed on neck, waist, arm and hands. The problem of waist pain was very significant. CONCLUSION: The new combined anti-G measure could meet the requirement of +9.0 Gz protection for high performance plane. How to prevent the occurrence of neck injury and alleviate the pain induced by G when using this measure should be studied further.

[+Gz protection provided by tilt-back seat and GZ-2 anti-G suit].

AIM: To investigate the +Gz protection provided by tilt-back seat and GZ-2 anti-G suit. METHODS: 6 subjects were exposed to centrifuge and onset rate is 3 G/s. First, their relaxed +Gz tolerances were determined while using tilt-back seat of 13 degrees. Secondly, it was their +Gz tolerance provided by pressurized GZ-2 anti-G suit and tilt-back seat of 13 degrees. Finally, their +Gz tolerances while using pressurized GZ-2 anti-G suit and tilt-back seat of 45 degrees were determined. The difference between the first and the third result was the +Gz protection that pressurized GZ-2 anti-G suit and tilt-back seat of 45 degrees offered. RESULTS: +Gz protection of pressurized GZ-2 anti-G suit and tilt-back seat of 13 degrees was 3.06 G, and +Gz protection of pressurized GZ-2 anti-G suit and tilt-back seat of 45 degrees was 4.13 G, which had an increase of 1.06 G. CONCLUSION: Tilt-back seat of 45 degrees can greatly enhance +Gz tolerances of human.

[Relative study for +Gz protection of an advanced bladder anti-G system and that of capstan anti-G system].

AIM: To assess the +Gz protection afforded by an advanced bladder anti-G system in the centrifuge against a capstan anti-G system. METHODS: Tow centrifuge experiments were completed, respectively, by two groups of six male subjects. In the first experiment, subjects using advanced bladder anti-G system, the +Gz protection afforded by this anti-G system was determined. Then they were exposed to simulated air combat maneuver (SACM)I with leg straining, the +Gz-time tolerance was determined. In the second experiment, subjects using capstan anti-G system, the +Gz protection afforded by this anti-G system was determined. Then they were exposed to SACMII with anti-G straining maneuver, the +Gz-time tolerance was determined. RESULTS: The anti-G effectiveness of the advanced bladder system was 5.33 G, which was significantly higher than that of the capstan system by 1.35 G (P < 0.01). All subjects of the two groups passed themselves SACM, but the effort, fatigue, and heart rates of the first group subjects were lower than those of the second group subjects. CONCLUSION: The results demonstrate that the +Gz protection afforded by the advanced bladder anti-G system is significantly higher than that by the capstan system.

[+Gz protection of the on board oxygen generating system (OBOGS) and anti-G equipment].

OBJECTIVE: To investigate the +Gz protection of the on board oxygen generating system (OBOGS) and anti-G equipment. METHOD: Physical and physiological tests of the OBOGS and anti-G equipment were accomplished using human centrifuge. +Gz tolerance of ten male subjects with or without the anti-G suit, pressure breathing for G (PBG) and OBOGS were determined. RESULT: The performance of the OBOGS and anti-G equipment fulfilled the requirements. The +Gz protections of the anti-G suit, PBG, and anti-G system were 2.08 G, 1.92 G, and 3.92 G, respectively. CONCLUSION: The +Gz protection of the OBOGS and anti-G equipment satisfy the performance requirements of high performance aircraft.

[Pathologic changes induced by sustained acceleration].

This paper mainly reviewed sustained +Gz acceleration-induced pathologic changes in various organ systems. Some of them are reversible and some may result in damage. Degree of the pathologic changes are related to G levels, G onset rates, duration of G exposure and individual difference factors. With raise of aircraft performance, acceleration problem is becoming more and more serious. Aviation medical workers should pay good attention to these changes and the use of high performance anti-G measures in order to ensure safety and performance of the pilots.