[#Why] The Perfect Glide Slope,
The 3° glide slope is the gold standard for most airport approaches, offering a safe, efficient descent path. While there are other glide slopes used in specific situations, the 3° angle is the standard default, used globally unless obstructions or terrain call for a steeper approach, sometimes up to 5°.
Why 3° Matters:
- PAPI Lights and Glide Paths: Precision Approach Path Indicator (PAPI) lights are set to align with this slope. Straying from this standard can lead to higher, longer approaches, forcing pilots to make adjustments for a precise touchdown.
Quick Math for 3° Descent Rates:
- Flying at 90 knots? Your descent rate should be approximately 450 Feet Per Minute (FPM).
- Calculation: Divide ground speed by 2 and add a zero (90/2 = 45, 45 with a zero = 450 FPM).
- Alternatively, multiply your groundspeed by 5 to estimate your descent rate.
Understanding the Math:
- 3° = 5.24% gradient.
- 1 NM = 6076 feet. Therefore, 6076 ft x 0.0524 = 318.4 ft/NM.
- Need to descend faster? Increase your descent rate proportionally.
When to Begin Your Descent:
- Formula: Divide the altitude to lose by 300.
- Example: Need to descend from 11,000' to 2,000'? That's 9,000' to lose. 9,000'/300 = 30 NM out. Simple, right?
Pilot's Tip: Start your descent a bit earlier to comfortably reach pattern altitude before arriving at the airport.
Wishing you blue skies, tailwinds, and safe journeys. Keep soaring in knowledge and skill!.
