BarNapkin

Exact flight math

Where the rules of thumb come from

• Pressure altitude, (29.92 − altimeter) × 1,000 + elevation: Pilot Institute
• Density altitude, 120 ft per °C off standard: AOPA
• True airspeed, 2% per 1,000 ft: FAA Pilot's Handbook, chapter 8
• Crosswind clock rule: PilotWorkshops
• Max drift, wind × 60 ÷ TAS: British Aerobatic Academy
• Three-degree descent, groundspeed × 5: Boldmethod
• Fuel weights: avgas 6.0 and oil 7.5 lb/gal; Jet A between 6.7 and 6.8, with 6.7 used here: FAA Pilot's Handbook, chapter 10 and FAA Weight & Balance Handbook
• The printed answers use the ICAO standard atmosphere and the compressible-flow airspeed equations.

Every answer uses the full formula. An answer is only as good as the numbers that go in, and no credit is taken for the descent. The pilot in command verifies everything against the aircraft's own flight manual and current official sources. This is not an approved flight planning source.