49 CFR § 572.123 - Neck assembly and test procedure.
(a) The neck assembly for the purposes of this test consists of the assembly of components shown in drawing 127–1015.
(b) When the head-neck assembly consisting of the head (drawing 127–1000), neck (drawing 127–1015), pivot pin (drawing 78051–339), bib simulator (drawing TE127–1025, neck bracket assembly (drawing 127–8221), six-axis neck transducer (drawing SA572–S11), neck mounting adaptor (drawing TE–2208–001), and three accelerometers (drawing SA572–S4) installed in the head assembly as specified in § 572.122, is tested according to the test procedure in paragraph (c) of this section, it shall have the following characteristics:
(1) Flexion.
(i) Plane D, referenced in Figure N2, shall rotate in the direction of preimpact flight with respect to the pendulum's longitudinal centerline between 74 degrees and 92 degrees. Within this specified rotation corridor, the peak moment about the occipital condyles shall be not less than 27 N-m (19.9 ft-lbf) and not more than 33 N-m (24.3 ft-lbf).
(ii) The positive moment shall decay for the first time to 5 N-m (3.7 ft-lbf) between 103 ms and 123 ms.
(iii) The moment shall be calculated by the following formula: Moment (N-m) = My−(0.01778m) × (FX).
(iv) My is the moment about the y-axis and FX is the shear force measured by the neck transducer (drawing SA572–S11) and 0.01778m is the distance from force to occipital condyle.
(2) Extension.
(i) Plane D, referenced in Figure N3, shall rotate in the direction of preimpact flight with respect to the pendulum's longitudinal centerline between 85 degrees and 103 degrees. Within this specified rotation corridor, the peak moment about the occipital condyles shall be not more than −19 N-m (−14 ft-lbf) and not less than −24 N-m (−17.7ft-lbf).
(ii) The negative moment shall decay for the first time to −5 N-m (−3.7 ft-lbf) between 123 ms and 147 ms.
(iii) The moment shall be calculated by the following formula: Moment (N-m) = My−(0.01778m) × (FX).
(iv) My is the moment about the y-axis and FX is the shear force measured by the neck transducer (drawing SA572–S11) and 0.017778m is the distance from force to occipital condyle.
(3) Time-zero is defined as the time of initial contact between the pendulum striker plate and the honeycomb material.
(c) Test procedure. The test procedure for the neck assembly is as follows:
(1) Soak the neck assembly in a controlled environment at any temperature between 20.6 and 22.2 °C (69 and 72 °F) and a relative humidity between 10 and 70 percent for at least four hours prior to a test.
(2) Torque the jam nut (drawing 9000341) on the neck cable (drawing 127–1016) to 0.23 ±0.02 N-m (2.0 ±0.2 in-lbs).
(3) Mount the head-neck assembly, defined in paragraph (b) of this section, on the pendulum so the midsagittal plane of the head is vertical and coincides with the plane of motion of the pendulum as shown in Figure N2 for flexion tests and Figure N3 for extension tests.
(4) Release the pendulum and allow it to fall freely from a height to achieve an impact velocity of 4.95 ±0.12 m/s (16.2 ±0.4 ft/s) for flexion tests and 4.3 ±0.12 m/s (14.10 ±0.40 ft/s) for extension tests, measured by an accelerometer mounted on the pendulum as shown in Figure 22 of 49 CFR 572 at the instant of contact with the honey comb.
(i) Time-zero is defined as the time of initial contact between the pendulum striker plate and the honeycomb material. All data channels should be at the zero level at this time.
(ii) Stop the pendulum from the initial velocity with an acceleration vs. time pulse which meets the velocity change as specified below. Integrate the pendulum acceleration data channel to obtain the velocity vs. time curve:
Table B
| Time | Pendulum pulse | |||
|---|---|---|---|---|
| ms | Flexion | Extension | ||
| m/s | ft/s | m/s | ft/s | |
| 10 | 1.2–1.6 | 3.9–5.3 | 1.0–1.4 | 3.3–4.6 |
| 20 | 2.4–3.4 | 7.9–11.2 | 2.2–3.0 | 7.2–9.8 |
| 30 | 3.8–5.0 | 12.5–16.4 | 3.2–4.2 | 10.5–13.8 |