Table 514.8D: -iv. Category 15 - Jet aircraft external store vibration exposure

$\mathrm{W_{1}=5\times10^{-3}\times K\times A_{1}\times B_{1}\times C_{1}\times D_{1}\times E_{1};\quad(g^{2}/Hz)\quad\underline{1}/}$ $\mathrm{W_{2}=H\times(q/\rho)^{2}\times K\times A_{2}\times B_{2}\times C_{2}\times D_{2}\times E_{2};\quad(g^{2}/Hz)\quad\underline{1}/}$ $M\leq0.90,$ $K=1.0;$ $0.90\leq M\leq1.0,$ $K=-4.8\times M+5.32;$ $M\geq1.0,$ $K=0.52$ $\underline{2}/$ $f_{1}=10^{5}C(t/R^{2}),$ $(Hz)$ $\underline{3}/,\ \underline{4}/,\ \underline{5}/;$ $f_{2}=f_{1}+1000,$ $(Hz)$ $\underline{3}/:$ $f_{0}=f_{1}+100,$ $(Hz)$ $\underline{6}/,\ \underline{7}/$

M - Mach number. H - $\text{Constant}=5.59$ (metric units) ( $=5\times10^{-5}$ English units). C - $\text{Constant}=2.54\times10^2$ (metric units) ( $=1.0$ English units). q - Flight dynamic pressure (see Table 514.8D-V) – $\text{kN}/\text{m}^2 (\text{lb} / \text{ft}^2)$. $\rho$ - Store weight density (weight/volume) - $\text{kg}/\text{m}^3 (\text{lb}/\text{ft}^3)$. Limit values of $\rho$ to $641\leq\rho\leq2403\text{ kg}/\text{m}^3$ $(40\leq\rho\leq150\text{ lb} / \text{ft}^3)$. t - Average thickness of structural (load carrying) skin - m (in). R - Store characteristic (structural) radius m (in) (Average over store length). $=$ Store radius for circular cross sections. $=$ Half or major and minor diameters for elliptical cross section. $=$ Half or longest inscribed chord for irregular cross sections.

1/ - When store parameters fall outside limits given, consult references. 2/ - Mach number correction (see Annex B). 3/ - Limit f₁ to 100 ≤ f₁ ≤ 2000 Hz 4/ - Free fall stores with tail fins, f₁ = 125 Hz 5/ - Limit length ratio to: 0.0010 ≤ C ( t / R² ) ≤ 0.020 6/ - f₀ = 500 Hz for cross sections not circular or elliptical 7/ - If f₀ ≥ 1200 Hz, then use f₀ = 2000 Hz 8/ - Configurations with separated aerodynamic flow within the first ¼ of the store length. Blunt noses, optical flats, sharp corners, and open cavities are some potential sources of separation. Any nose other than smooth, rounded, and gently tapered is suspect. Aerodynamics engineers should make this judgment.

MIL-STD-810H METHOD 514.8, ANNEX D

Figure description:

Acceleration Spectral Density vs. Frequency

Acceleration Spectral Density Vibration Profile

Annotations

• $f_n$ = 1st body bending mode frequency ($f_n$) can be greater than 50 Hz (text_label - position: top right region)
• Assembled Store $W_o = 2.0$ (at store nose and tail (text_label - position: center right region))
• Materiel in Store: $W_o = 2.0$ at store nose and tail; $W_o = 0.5$ at store CG; Linear extrapolation between these points (text_label - position: bottom right region)
• $W_o$ (text_label - position: y-axis at peak level)
• 0.01 (text_label - position: y-axis at base level)

Figure 514.8D-7. Category 15 - Jet aircraft store buffet response.

514.8D -V. Dynamic pressure calculation

(See Annex A, paragraph 2.6.2 for definitions and details)

1. Dynamic pressure calculation valid only for Mach numbers less than 1.0 (one).
2. Mach number may be used at any airspeed.
3. Unless specifically stated otherwise, assume airspeeds to be in calibrated airspeed (Kcas).
4. When airspeed values are given as indicated airspeed (Kias), assume Kias equal Kcas.
5. Altitude (h) is pressure altitude and not height above terrain.

$q=2.5\rho_{o}\sigma V_{a}^{2}[(1/\delta\{[1+0.2(V_{cas}/V_{ao})^{2}]^{3\ 5}-1\}+1)^{2/7}-1]$ $q=\frac{1}{2}\rho_{o}\sigma V_{a}^{2}M^{2}$ $q=\frac{1}{2}\rho_{o}V_{eas}^{2}$ $q=\frac{1}{2}\rho_{o}\sigma V_{tas}^{2}$

Airspeeds are typically expressed in knots as follows: V_kcas - knots calibrated air speed V_kias - knots indicated air speed V_keas - knots equivalent air speed V_ktas - knots true air speed [ knots = nautical miles per hour ( knots x 0.51478 = m/sec)( knots x 1.6889 = ft/sec) ]

Figure description:

Dynamic Pressure Nomogram Charting Mach vs Altitude

Mach vs. Pressure Altitude for Constant Dynamic Pressure (q

Legend

• q = 76.2 — color: black; symbol: Solid line
• q = 135.4 — color: black; symbol: Solid line
• q = 211.5 — color: black; symbol: Solid line
• q = 304.6 — color: black; symbol: Solid line
• q = 414.6 — color: black; symbol: Solid line
• q = 541.6 — color: black; symbol: Solid line
• q = 685.5 — color: black; symbol: Solid line
• q = 846.3 — color: black; symbol: Solid line
• q = 1024.03 — color: black; symbol: Solid line
• q = 1218.6 — color: black; symbol: Solid line
• q = 1430.2 — color: black; symbol: Solid line
• q = 1658.2 — color: black; symbol: Solid line
• q = 1904.1 — color: black; symbol: Solid line

Annotations

• DYN. PRESS: q = 76.2 lb/ft (text_label - position: Label for the first dynamic pressure curve)

Figure 514.8D-8. Dynamic pressure as a function of Mach number and altitude.