L32 Pre-flight

L32 Pre-flight#

Block 4: Aircraft Survivability and Mission Planning — Lesson 32: Threat Geometry: SAM Rings, MEZ/LEZ Work this before L32. 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#

  • L31 wrap-up (the P_K chain; a link can act only where the site can see and reach you).

  • The Jupyter Book Reading page for L32 — the aspect-dependent detection contour R(φ) = R_ref [σ_b(θ(φ))/σ_ref]^(1/4) with θ = wrap(φ + 180° − ψ), the radar horizon d = 4.12(√h_r + √h_t) km, the MEZ (v_m + v_t) t_max and LEZ (v_m − v_t) t_max, and overlaps, gaps and seams in a layered laydown.

Quiz questions (5 items, ~5 minutes)#

Q1. (Multiple choice) A radar sits at the origin. An aircraft flies heading 090° (due east) and is due north of the radar, at bearing φ = 0° from it. Using θ = wrap(φ + 180° − ψ), measured clockwise from the nose, which aspect does the radar see?

  • [ ] (a) 0°, nose-on — the aircraft is flying toward the radar

  • [ ] (b) 90°, the right beam — the radar lies off the right wing

  • [ ] (c) 180°, tail-on — the radar lies behind the aircraft’s track

  • [ ] (d) 270°, the left beam — the radar lies off the left wing

Q2. (Multiple choice) An X-band TTR on a 16 m mast would detect an aircraft at 40 km by the R⁴ law at its current aspect. The aircraft is flying at 81 m. Which bound sets the detection range, and what is it?

  • [ ] (a) The horizon, at 53.6 km — it is the larger of the two bounds

  • [ ] (b) The R⁴ law, at 40 km — the horizon lies beyond that range

  • [ ] (c) The horizon, at 37.1 km — only the aircraft’s own altitude counts

  • [ ] (d) Neither alone: the two ranges add to about 93.6 km

Q3. (Multiple choice) A missile is launched at an aircraft closing on a SAM site. At launch the aircraft is inside the MEZ but outside the LEZ, and it turns directly away. Under the constant-speed model, what does the turn do here, and what would the same turn do inside the LEZ?

  • [ ] (a) Here it escapes; inside the LEZ the missile still catches it

  • [ ] (b) Here it escapes, and inside the LEZ it escapes as well

  • [ ] (c) Here it changes nothing; only inside the LEZ does it help

  • [ ] (d) It changes nothing in either zone — only the range matters

Q4. (Multiple choice) A notional SAM’s missile averages v_m = 1.1 km/s and can fly for at most t_max = 50 s. The target flies at v_t = 0.2 km/s. What are the MEZ and LEZ radii?

  • [ ] (a) MEZ 55 km and LEZ 55 km

  • [ ] (b) MEZ 45 km and LEZ 65 km

  • [ ] (c) MEZ 65 km and LEZ 45 km

  • [ ] (d) MEZ 65 km and LEZ 55 km

Q5. (Short answer) Give two reasons a SAM site’s threat ring on your map is not one fixed circle. Say which of them flying high usually removes for the B-21, and why routing on the nose-on ring alone can mislead you.

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