(a) When subjected to continuously applied force in accordance with paragraph (b) of this section, the lumbar spine assembly shall flex by an amount that permits the thoracic spine to rotate from its initial position in accordance with Figure No. 18 of §572.21 (49 CFR part 572) by 40 degrees at a force level of not less than 18 pounds and not more than 22 pounds, and straighten upon removal of the force to within 5 degrees of its initial position.

(b) Test procedure.

(1) The lumbar spine flexure test is conducted on a dummy assembly as shown in drawing LP 1049/A, but with the arms (which consist of parts identified as items 17 through 30) and all head-neck parts (identified as items 1 through 13 and 59 through 63), removed.

(2) With the torso assembled in an upright position, adjust the lumbar cable by tightening the adjustment nut for the lumbar vertebrae until the spring is compressed to 2⁄3 of its unloaded length.

(3) Position the dummy in an upright seated position on a seat as indicated in Figure No. 18 of §572.21 (lower legs do not need to be removed, but must be clamped firmly to the seating surface), ensuring that all dummy component surfaces are clean, dry and untreated unless otherwise specified.

(4) Firmly affix the dummy to the seating surface through the pelvis at the hip joints by suitable clamps that also prevent any relative motion with respect to the upper legs during the test in §572.65(c)(3) of this part. Install a pull attachment at the neck to torso juncture as shown in Figure 18 of §572.21.

(5) Flex the thorax forward 50 degrees and then rearward as necessary to return it to its initial position.

(6) Apply a forward pull force in the midsagittal plane at the top of the neck adapter so that at 40 degrees of the lumbar spine flexion the applied force is perpendicular to the thoracic spine box. Apply the force at any torso deflection rate between 0.5 and 1.5 degrees per second up to 40 degrees of flexion but no further; maintain 40 degrees of flexion for 10 seconds, and record the highest applied force during that time. Release all force as rapidly as possible and measure the return angle three minutes after release.