Title 49

SECTION 572.173

572.173 Neck assembly and test procedure.

§ 572.173 Neck assembly and test procedure.

(a) The neck assembly for the purposes of this test consists of the assembly of components shown in drawing 420-2000 (incorporated by reference, see § 572.170).

(b) When the head-neck assembly consisting of the head (drawing 420-1000), neck (drawing 420-2000), six-channel neck transducer (SA572-S11, included in drawing 420-0000), lower neck bracket assembly (drawing 420-2070), and either three uniaxial accelerometers (drawing SA572-S4, included in drawing 420-0000) or their mass equivalent installed in the head assembly as specified in drawing 420-1000 (all incorporated by reference, see § 572.170), 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 T2, shall rotate in the direction of preimpact flight with respect to the pendulum's longitudinal centerline between 76 degrees and 90 degrees. During the time interval while the rotation is within the specified corridor, the peak moment, measured by the neck transducer (drawing SA572-S11, included in drawing 420-0000) (incorporated by reference, see § 572.170), about the occipital condyles may not be less than 50 N-m (36.9 ft-lbf) and not more than 62 N-m (45.7 ft-lbf). The positive moment shall decay for the first time to 10 N-m (7.4 ft-lbf) between 86 ms and 105 ms after time zero.

(ii) The moment shall be calculated by the following formula: Moment (N-m) = My − (0.01778) × (FX).

(iii) My is the moment about the y-axis in Newton-meters, FX is the shear force measured by the neck transducer (drawing SA572-S11) in Newtons, and 0.01778 is the distance in meters from the load center of the neck transducer to the occipital condyle.

(2) Extension. (i) Plane D, referenced in Figure T3, shall rotate in the direction of preimpact flight with respect to the pendulum's longitudinal centerline between 96 degrees and 115 degrees. During the time interval while the rotation is within the specified corridor, the peak moment, measured by the neck transducer (drawing SA572-S11, included in drawing 420-0000) (incorporated by reference, see § 572.170), about the occipital condyles may not be more than −37 N-m (−27.3 ft-lbf) and not less than −46 N-m (−33.9 ft-lbf). The positive moment shall decay for the first time to −10 N-m (−7.4 ft-lbf) between 100 ms and 116 ms after time zero.

(ii) The moment shall be calculated by the following formula: Moment (N-m) = My − (0.01778) × (FX).

(iii) My is the moment about the y-axis in Newton-meters, FX is the shear force measured by the neck transducer (drawing SA572-S11, included in drawing 420-0000) (incorporated by reference, see § 572.170) in Newtons, and 0.01778 is the distance in meters from the load center of the neck transducer to the occipital condyle.

(3) Time zero is defined as the time of initial contact between the pendulum striker plate and the honeycomb material. All data channels shall be at the zero level at this time.

(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 hex nut (drawing 420-2000, part 9000130) on the neck cable (drawing 420-2060) (both incorporated by reference, see § 572.170) to 0.9 ±0.2 N-m (8 ±2 in-lbf) before each test on the same neck.

(3) Mount the head-neck assembly, defined in paragraph (b) of this section, on the pendulum described in Figure 22 of 49 CFR part 572 so that the leading edge of the lower neck bracket coincides with the leading edge of the pendulum as shown in Figure T2 for flexion tests and Figure T3 for extension tests.

(4)(i) Release the pendulum and allow it to fall freely from a height to achieve an impact velocity of 6.1 ±0.12 m/s (20.0 ±0.4 ft/s) for flexion tests and 5.03 ±0.12 m/s (16.50 ±0.40 ft/s) for extension tests, measured by an accelerometer mounted on the pendulum as shown in Figure T2 at the instant of contact with the honeycomb.

(ii) Stop the pendulum from the initial velocity with an acceleration vs. time pulse that meets the velocity change as specified below. Integrate the pendulum acceleration data channel to obtain the velocity vs. time curve:

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