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Biomedical subjects

J W Brinkley

Publications and source records attributed to J W Brinkley.

8 recordsLinked to original sources
PubMed1986

Effect of seat cushions on human response to +Gz impact.

Human response to vertical (+Gz) impact acceleration was evaluated as a function of various seat cushions, including current operational cushions used in such aircraft as the A-10, F-15, and F-111 and proposed alternative cushions comprised of rate-dependent, slow-recovery polyurethane foams. There were 133 tests conducted of volunteer subjects in seven different experimental conditions, using a vertical deceleration tower facility. The mean peak acceleration of the impact carriage for these tests was 9.85 G (S.D. = 0.07) and the mean carriage velocity change was 8.01 m X s-1 (S.D. = 0.05). Resultant seat loads and head and chest accelerations were significantly higher for the F-111 cushion than for the rate-dependent foam cushions, which included cushions comprised of Confor foam or Temper foam. Resultant head and chest accelerations were also significantly higher for the ACES II cushion than for the rate-dependent foam cushions. Therefore, from an impact protection standpoint, the operational cushions were inferior to the proposed alternative cushions. Operational use of rate-dependent foam cushions is recommended to improve the impact protection performance of escape systems. Flight tests conducted by the USAF Strategic Air Command have shown that these cushions enhance crewmember sitting comfort during long-duration missions.

Acceleration↗
PubMed1986

Comparison of human impact response in restraint systems with and without a negative G strap.

A test program to assess the influence of a negative G strap on restraint dynamics and human impact response was conducted at AFAMRL. There were 131 experimental-level impact tests with volunteer subjects performed in eight different test conditions. Forward-facing (-Gx) impacts were carried out on a horizontal accelerator, while vertical (+Gz) impact tests were done on a vertical drop tower facility. In both axes, the experimental exposure was an approximate half-sine waveform with peak acceleration up to 10 G and velocity change up to 9.2 m X s-1. Subjects were restrained to the test vehicle using either the PCU-15/P torso harness and lap belt, which is used operationally in such aircraft as the A-20 and F-15, or a conventional double shoulder strap and lap belt configuration. In one half of the test conditions, fixed-length negative G straps were incorporated into these restraint systems. In the other test conditions, the unmodified restraint systems were evaluated. Adding the negative G strap to either restraint system had clearly beneficial effects. These included decreasing the tendency toward submarining in forward-facing impacts, providing better occupant-seat coupling during free falls, and improving vertical impact protection. Sufficient benefits appear to result from use of the negative G strap to warrant a recommendation for its incorporation into selected USAF restraint systems, such as the PCU-15/P torso harness and lap belt. Additional data analysis revealed that the conventional double shoulder strap and lap belt restraint provided better forward-facing and vertical impact protection than the PCU-15/P torso harness and lap belt configuration. Further research at AFAMRL is planned to identify restraint harness features which may improve the performance of current and future impact protection systems.

Acceleration↗
PubMed1985

Knee ligament injury during lateral impact.

A volunteer woman subject incurred injury to her right knee consisting of a torn anterior cruciate ligament and stretched medial collateral ligament during a lateral (+Gy) impact test. Similar injury has not been reported in the English-language literature an accidental sideward automotive crashes or lateral impact experimentation involving humans. The primary mechanism which produced this injury was external tibial rotation on the femur with the knee flexed. The factors contributing to the injury included extraordinarily forceful leg bracing by the subject, her knee joint laxity or hypermobility, and the absence of side supports to limit lower extremity flailing during the impact response. In future lateral impact tests, women subjects should be used with caution and any subject with abnormal joint mobility should be excluded from participation.

Adult↗
PubMed1985

Psychomotor performance after forward-facing impact.

An experiment to assess psychomotor performance before and after forward-facing (-Gx) impact was conducted using the AFAMRL Horizontal Decelerator Facility. There were 10 volunteer subjects who participated in 50 tests at 4 impact levels (0 G or sham, 8 G, 10 G, and 12 G). Two initial head positions were explored at the highest impact level. The manikin psychomotor task, a complex reaction time and accuracy task, was used to evaluate performance. Linear and angular accelerations were measured at the head. Although there was a weak correlation between angular head acceleration and prolonged post-impact reaction time, no compelling statistical evidence was found to support the hypothesis that psychomotor performance is degraded with increasing impact severity at these test levels. The highest test level explored in this study may not have been sufficient to produce a change in performance or, alternatively, the manikin task may not have been sufficiently sensitive to measure a change in performance if one was present. In addition, significantly lower angular head acceleration was observed at the 12-G test level when the head was rotated forward initially rather than prepositioned upright against the headrest. The potential for temporary stunning of aircrew members during operational crash landings or ditchings may be reduced by rotating the head forward prior to an imminent crash if time permits.

Acceleration↗
PubMed1983

Vertical impact evaluation of the F/FB-111 crew restraint configuration, headrest position, and upper extremity bracing technique.

An experiment to assess the influence of changes in restraint harness configuration, fore-aft headrest position, and upper extremity bracing technique on human response to impact was conducted using the AFAMRL Vertical Deceleration Tower. A total of 201 tests was performed with volunteer subjects in 11 test conditions to evaluate 3 restraint harnesses, 3 arm bracing conditions, and 4 seat adjustment configurations. The test fixture, restraint harness, and subject were instrumented to obtain pertinent objective data during each experiment. Measured parameters included acceleration of the impact carriage and test seat, velocity of the carriage, loads reacted at the seat, loads measured at the restraint harness attachment points, triaxial translational accelerations at the head and chest of the subject, and body segment displacements. The mean peak carriage acceleration for the 161 experimental level tests was 10.5 G (S.D. = 0.18) and the mean carriage velocity change was 7.89 m/s (S.D. = 0.05). Resultant head and chest accelerations were increased in a proposed, modified F/FB-111 restraint system compared to the operational F/FB-111 restraint system. These findings contributed to the decision not to implement the proposed modification. Also, the arms crossed bracing position for F/FB-111 ejectees preparing for landing impact of the crew module was associated with higher seat loads than the arms extended position. With the arms extended and braced on the anterior thighs or knees, loads are transmitted through the extremities to the footrest thereby reducing loading of the vertebral column. Operational use of the arms extended position prior to anticipated vertical impact accelerations may be helpful in reducing the vertebral fracture rate associated with these mechanical force environments.

Adult↗