Pilot Mental Math (Quick Reference)
🔹 ROC / ROD
Use GS × Gradient
🔹 3° Glide Path (ROD)
Use GS × 5 or (GS × 10) ÷ 2
For better accuracy, add +6% of the result
Example: GS 100 → 100 × 5 = 500
6% of 500 = 30 → ROD ≈ 530 ft/min
🔹 Mach Change
For every 0.01 Mach change, speed changes by ≈ 6 kt
( 1% of speed of sound)
🔹 Same Mach, Different Level (or same level with temperature difference)
At the same Mach, TAS varies with temperature
Warmer = faster / Colder = slower
Approx 1 kt per 1°C
Example: FL350 vs FL370 → about 4 kt difference
( FL350 -faster)
(Except inversion or tropopause conditions, no wind involved)
🔹 Different Mach + Different Level
Combine and offset the effects above
Example:
FL370 M0.84
FL350 M0.83
Mach difference = 6 kt
Temperature effect = 4 kt
→ Net difference = 2 kt
(FL370-faster)
🔹 Landing (Higher Threshold Crossing Height)
For every 1 ft above normal TCH → landing distance increases by ≈ 6 m or 20 feet
📌 Not exact values — for quick mental calculation and backup use only