L36 Pre-flight

L36 Pre-flight#

Block 4: Aircraft Survivability and Mission Planning — Lesson 36: SEAD, Maneuvers, and Standoff Jamming Work this before L36. Pre-flights are never collected — in class, anyone may be cold-called to present any question at the board, and that recitation is the participation grade.

Assumed pre-class reading#

  • L17’s jam-to-signal ratio, \(J/S = 4\pi P_jG_jR^2 B_r/(P_tG_t\sigma B_j)\), the burn-through range, and the self-protect versus stand-off distinction; L5’s Doppler shift \(f_d = 2v_r/\lambda\) and the MTI notch; L6’s sidelobes.

  • The Jupyter Book Reading page for L36 — SEAD suppression versus destruction and the suppression window, the beam/notch maneuver, the standoff \(J/S\) with its two ranges (\(R_t\), \(R_j\)) and two gains (\(G_r\), \(G_r'\)), standoff burn-through, the jammed contour and its strobe, and the scalings \(R_{bt} \propto R_j^{1/2}\) and \(R_{bt} \propto (G_r'/G_r)^{-1/4}\).

Quiz questions (5 items, ~5 minutes)#

Q1. (Multiple choice) A standoff jammer (SOJ) orbits 140 km due west of a SAM acquisition radar that has a 4° beam and −30 dB sidelobes. Four strike packages are each 35 km from the radar. Which package gets the shortest burn-through range — the one the SOJ protects best?

  • [ ] (a) The package 35 km due east of the radar, on the far side from the SOJ

  • [ ] (b) The package 35 km due north of the radar, square to the SOJ’s line

  • [ ] (c) The package 35 km due west of the radar, between the radar and the SOJ

  • [ ] (d) The package 35 km southwest of the radar, 45° off the SOJ’s line

Q2. (Multiple choice) One radar, one SOJ. A package off the jammer’s azimuth is burned through at 32 km, where the jamming enters through the radar’s −24 dB sidelobes. The package turns onto the jammer’s azimuth, with the SOJ, the radar and the target unchanged. Its new burn-through range is:

  • [ ] (a) 2.0 km

  • [ ] (b) 8.0 km

  • [ ] (c) 32.0 km

  • [ ] (d) 127.4 km

Q3. (Multiple choice) An SOJ 100 km from a radar holds a package’s sidelobe burn-through range to 20 km. A newly located SAM forces the SOJ to back off to 225 km to stay outside that SAM’s MEZ plus the keep-out margin; the radar, the package’s azimuth and everything else are unchanged. The new sidelobe burn-through range is:

  • [ ] (a) 13.3 km

  • [ ] (b) 24.5 km

  • [ ] (c) 45.0 km

  • [ ] (d) 30.0 km

Q4. (Multiple choice) An X-band tracking radar (\(\lambda = 3\) cm) uses MTI that rejects every return with \(|f_d| < 2\) kHz. An aircraft at 250 m/s wants its echo inside that notch. It must fly:

  • [ ] (a) Within 6.9° of the beam, perpendicular to the line of sight

  • [ ] (b) Within 13.9° of the beam, perpendicular to the line of sight

  • [ ] (c) Within 6.9° of nose-on, flying straight at the radar

  • [ ] (d) Within 83.1° of the beam, perpendicular to the line of sight

Q5. (Short answer) (i) Distinguish SEAD suppression from destruction, and give one lethal and one non-lethal means. (ii) A package’s time inside one SAM’s lethal zone runs from 0410 to 0418; the suppression of that SAM runs from 0400 to 0415. What happens to the package, and name two ways the planner could fix it.

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