✈️ Flight Deck Cheat Sheet: The 3:1 Rule for Top of Descent (TOD)
Struggling to calculate your descent without an active VNAV profile? Whether you fly a steam-gauge Cessna, a modern turboprop, or an airliner, the classic 3:1 rule guarantees you never end up 5,000 ft too high on final.
📌 Key Takeaways:
The Distance Formula (Altitude to Lose × 3): Drop the last three zeros of your altitude to lose, then multiply by 3. If you are cruising at FL240 and need to enter the pattern at 2,000 ft (22,000 ft to lose: 22 × 3), your Top of Descent is 66 nautical miles out.
The Descent Rate Formula (Groundspeed × 5): Take your current groundspeed and multiply by 5 (or divide by 2 and add a zero). At a 240-knot groundspeed, aim for roughly 1,200 fpm on the vertical speed indicator.
The Buffer Factor: Always add 5 to 10 nautical miles to your calculated TOD distance to comfortably decelerate and configure flaps/gear before reaching the initial approach fix.
📺 Watch the full breakdown in action: https://youtu.be/MCbT-90kDl8
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