Wind Triangle
Heading and groundspeed for a course
Variation: enter east as positive (8) and west as negative (−13) to get magnetic heading. Add compass deviation from the card for a compass heading.
Runway Wind
Crosswind and headwind components
Watch the reference: runway numbers and tower or ATIS winds are magnetic. Raw METAR and TAF winds are true, so convert before you use them here.
Density Altitude
What the airplane thinks the field elevation is
Performance: use density altitude with the POH charts for takeoff and climb, not field elevation. Cloud base uses the 2.5 °C per 1000 ft spread rule and only applies to convective cumulus.
True Airspeed
Calibrated to true, with Mach
CAS vs IAS: most trainers are within a knot or two in cruise, so the indicated number is usually fine here. Use the airspeed calibration table in section 5 of the POH when it matters. Rule of thumb adds 2% per 1000 ft to CAS.
Time · Speed · Distance
Pick what to solve for
Time accepts plain minutes (38) or hours and minutes (1:15). Off time is a 24-hour clock in the same reference you plan in, Zulu or local.
Fuel
Burn, endurance, and what it weighs
Day VFR needs 30 minutes of reserve at cruise burn, night VFR 45, IFR 45 to the alternate. Endurance on board assumes the same burn rate the whole time.
Climb & Descent
Top of descent, rate, and gradient
The 3:1 rule is three nautical miles for every 1000 ft to lose, and a 3° path needs roughly groundspeed × 5 in feet per minute. Both work in the airplane without a calculator.
Weight & Balance
Example numbers below, replace them with yours
| Station | Weight lb | Arm in | Moment | Remove |
|---|
Add or remove stations to match your aircraft, and rename any of them. Type a weight in gallons by adding g, for example 40g, and it converts at the fuel weight set above. Rows and limits are saved on this device.
Conversions
The rest of the slide rule
Fuel weight uses 6.0 lb/gal for avgas. Jet A at 6.7 lb/gal is on the fuel page.